diff --git a/.changeset/unified-layout-language.md b/.changeset/unified-layout-language.md
new file mode 100644
index 000000000..006d4d25c
--- /dev/null
+++ b/.changeset/unified-layout-language.md
@@ -0,0 +1,5 @@
+---
+"hunkdiff": minor
+---
+
+Rename the single-column diff layout to unified, add canonical OpenTUI and extension API v23 fields, and retain deprecated stack compatibility across existing CLI, config, command, OpenTUI, and extension integrations.
diff --git a/AGENTS.md b/AGENTS.md
index 9c6dda1e5..79fe7795d 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -98,7 +98,7 @@ ReviewIntent + caller facts -> planReviewIntent -> ReviewAction[] -> reducer ->
 - Keep the app review-first: the main pane is a single top-to-bottom stream of all visible file diffs.
 - The sidebar is for navigation. Selecting a file jumps to that file in the main review stream; it should not collapse the main pane to one file.
 - Keep Pierre as the diff engine and renderer foundation. Do not switch the main renderer back to OpenTUI's built-in `<diff>` widget.
-- Keep split and stack views terminal-native and driven from the same normalized diff model.
+- Keep split and unified views terminal-native and driven from the same normalized diff model.
 - Preserve mouse + keyboard parity for primary actions.
 - Keep the chrome restrained: top menu bar, minimal borders, no redundant metadata headers.
 
@@ -165,7 +165,7 @@ ReviewIntent + caller facts -> planReviewIntent -> ReviewAction[] -> reducer ->
 ## review behavior
 
 - Default behavior is a multi-file review stream in sidebar order.
-- Layout modes are `auto`, `split`, and `stack`. `auto` chooses split on wide terminals and stack
+- Layout modes are `auto`, `split`, and `unified`. `auto` chooses split on wide terminals and unified
   on narrow ones; explicit modes override it.
 - `[` and `]` navigate hunks across the full review stream. Do not reintroduce `j`/`k` hunk navigation unless the user asks.
 - Agent context belongs beside the code, not hidden in a separate mode or workflow.
diff --git a/README.md b/README.md
index 1811d16ec..c3c4d4c61 100644
--- a/README.md
+++ b/README.md
@@ -11,21 +11,21 @@ Hunk is a review-first terminal diff viewer for agent-authored changesets, built
 
 - multi-file review stream with sidebar navigation
 - inline AI and agent annotations beside the code
-- split, stack, and responsive auto layouts
+- split, unified, and responsive auto layouts
 - watch mode for auto-reloading file and Git-backed reviews
 - keyboard, mouse, pager, and Git difftool support
 
 <table>
  <tr>
    <td width="60%" align="center">
-    <img width="845" alt="image" src="https://github.com/user-attachments/assets/35605618-be3f-479e-b6e0-edb089910651" />
+     <img width="845" alt="image" src="https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/review-stream.webp" />
      <br />
      <sub>Split view with sidebar and inline AI notes</sub>
    </td>
    <td width="40%" align="center">
-     <img width="507"alt="image" src="https://github.com/user-attachments/assets/92eb8993-f044-436d-a038-8139da5ad8de" />
+     <img width="507"alt="image" src="https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/agent-comments.webp" />
      <br />
-     <sub>Stacked view and mouse-selectable menus</sub>
+     <sub>Unified view and mouse-selectable menus</sub>
    </td>
  </tr>
 </table>
@@ -135,17 +135,17 @@ For the full live-session and `--agent-context` workflow guide, see [the agent w
 
 ## Feature comparison
 
-| Capability                         | [hunk](https://github.com/modem-dev/hunk) | [lumen](https://github.com/jnsahaj/lumen) | [difftastic](https://github.com/Wilfred/difftastic) | [delta](https://github.com/dandavison/delta) | [diff-so-fancy](https://github.com/so-fancy/diff-so-fancy) | [diff](https://www.gnu.org/software/diffutils/) |
-| ---------------------------------- | ----------------------------------------- | ----------------------------------------- | --------------------------------------------------- | -------------------------------------------- | ---------------------------------------------------------- | ----------------------------------------------- |
-| Review-first interactive UI        | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Multi-file review stream + sidebar | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Inline agent / AI annotations      | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Responsive auto split/stack layout | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Mouse support inside the viewer    | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Runtime view toggles               | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Syntax highlighting                | ✅                                        | ✅                                        | ✅                                                  | ✅                                           | ❌                                                         | ❌                                              |
-| Structural diffing                 | ❌                                        | ❌                                        | ✅                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Pager-compatible mode              | ✅                                        | ❌                                        | ✅                                                  | ✅                                           | ✅                                                         | ✅                                              |
+| Capability                           | [hunk](https://github.com/modem-dev/hunk) | [lumen](https://github.com/jnsahaj/lumen) | [difftastic](https://github.com/Wilfred/difftastic) | [delta](https://github.com/dandavison/delta) | [diff-so-fancy](https://github.com/so-fancy/diff-so-fancy) | [diff](https://www.gnu.org/software/diffutils/) |
+| ------------------------------------ | ----------------------------------------- | ----------------------------------------- | --------------------------------------------------- | -------------------------------------------- | ---------------------------------------------------------- | ----------------------------------------------- |
+| Review-first interactive UI          | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Multi-file review stream + sidebar   | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Inline agent / AI annotations        | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Responsive auto split/unified layout | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Mouse support inside the viewer      | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Runtime view toggles                 | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Syntax highlighting                  | ✅                                        | ✅                                        | ✅                                                  | ✅                                           | ❌                                                         | ❌                                              |
+| Structural diffing                   | ❌                                        | ❌                                        | ✅                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Pager-compatible mode                | ✅                                        | ❌                                        | ✅                                                  | ✅                                           | ✅                                                         | ✅                                              |
 
 Hunk is optimized for reviewing a full changeset interactively.
 
@@ -162,7 +162,7 @@ Example:
 
 ```toml
 theme = "github-dark-default" # any built-in theme id, auto, or custom
-mode = "auto"        # auto, split, stack
+mode = "auto"        # auto, split, unified
 vcs = "git"          # git, jj, sl
 watch = false
 exclude_untracked = false
diff --git a/benchmarks/README.md b/benchmarks/README.md
index 7b2794cd3..5882f63ec 100644
--- a/benchmarks/README.md
+++ b/benchmarks/README.md
@@ -58,7 +58,7 @@ bun run bench:competitors
 - `bootstrap-load.ts` — measures bootstrap and git-loader cost on a synthetic large repo, including file-pair bootstrap.
 - `working-tree-load.ts` — measures git working-tree loads across small, medium, large, many-untracked, and few-large-untracked repos.
 - `changeset-parse.ts` — measures patch normalization, Pierre parsing, patch chunking, and normalized `DiffFile` construction for many-small-files, balanced, and large-single-file patches.
-- `render-layout.ts` — measures pure split/stack row building, section geometry, and review-plan construction for many-small-files, balanced, and large-single-file streams.
+- `render-layout.ts` — measures pure split/unified row building, section geometry, and review-plan construction for many-small-files, balanced, and large-single-file streams.
 - `highlight-prefetch.ts` — measures selected-file highlight startup and adjacent prefetch readiness.
 - `worker-highlight-cache.ts` — measures a cold worker highlight against an immediate compact-result cache hit.
 - `highlight-cache-layers.ts` — measures a resident terminal-cache hit against a worker-cache revisit after the terminal cache evicts the diff.
diff --git a/benchmarks/render-layout.ts b/benchmarks/render-layout.ts
index 6d5effc07..15f0e6032 100644
--- a/benchmarks/render-layout.ts
+++ b/benchmarks/render-layout.ts
@@ -1,6 +1,6 @@
-// Benchmark pure diff row/layout planning across split, stack, and size-shape cases.
+// Benchmark pure diff row/layout planning across split, unified, and size-shape cases.
 import { performance } from "perf_hooks";
-import { buildSplitRows, buildStackRows } from "../packages/hunk/src/ui/diff/diffRows";
+import { buildSplitRows, buildUnifiedRows } from "../packages/hunk/src/ui/diff/diffRows";
 import { buildReviewRenderPlan } from "../packages/hunk/src/ui/diff/reviewRenderPlan";
 import { measureDiffSectionGeometry } from "../packages/hunk/src/ui/diff/diffSectionGeometry";
 import { resolveTheme } from "../packages/hunk/src/ui/themes";
@@ -16,7 +16,7 @@ function measureMs(run: () => void) {
 
 function measureScenario(name: string, files: ReturnType<typeof createLargeSplitStreamFiles>) {
   let splitRows = 0;
-  let stackRows = 0;
+  let unifiedRows = 0;
   let plannedRows = 0;
 
   const splitRowsMs = measureMs(() => {
@@ -25,9 +25,9 @@ function measureScenario(name: string, files: ReturnType<typeof createLargeSplit
     }
   });
 
-  const stackRowsMs = measureMs(() => {
+  const unifiedRowsMs = measureMs(() => {
     for (const file of files) {
-      stackRows += buildStackRows(file, null, theme).length;
+      unifiedRows += buildUnifiedRows(file, null, theme).length;
     }
   });
 
@@ -50,12 +50,12 @@ function measureScenario(name: string, files: ReturnType<typeof createLargeSplit
   });
 
   console.log(`METRIC ${name}_split_rows_ms=${splitRowsMs.toFixed(2)}`);
-  console.log(`METRIC ${name}_stack_rows_ms=${stackRowsMs.toFixed(2)}`);
+  console.log(`METRIC ${name}_unified_rows_ms=${unifiedRowsMs.toFixed(2)}`);
   console.log(`METRIC ${name}_geometry_ms=${geometryMs.toFixed(2)}`);
   console.log(`METRIC ${name}_review_plan_ms=${reviewPlanMs.toFixed(2)}`);
   console.log(`METRIC ${name}_files=${files.length}`);
   console.log(`METRIC ${name}_split_rows=${splitRows}`);
-  console.log(`METRIC ${name}_stack_rows=${stackRows}`);
+  console.log(`METRIC ${name}_unified_rows=${unifiedRows}`);
   console.log(`METRIC ${name}_planned_rows=${plannedRows}`);
 }
 
diff --git a/docs/extensions.md b/docs/extensions.md
index fd0c85c6b..890221878 100644
--- a/docs/extensions.md
+++ b/docs/extensions.md
@@ -302,8 +302,10 @@ and retires the replaced instance at that explicit ownership boundary.
 
 ### `hunk.apiVersion`
 
-The API generation this Hunk speaks (currently `22`). Branch on it if you want
-one file to support several Hunk versions. Version 22 adds frame-derived pane preferred sizing, non-resizable dynamic panes, and commit-history paint tokens; version 21 adds optional inclusive history-range review
+The API generation this Hunk speaks (currently `23`). Branch on it if you want
+one file to support several Hunk versions. Version 23 adds canonical unified-layout fields while
+preserving the previous event vocabulary; version 22 adds frame-derived pane preferred sizing,
+non-resizable dynamic panes, and commit-history paint tokens; version 21 adds optional inclusive history-range review
 planning and bounded comparison commit summaries; version 20 adds optional commit timestamps to review
 metadata, pane clipboard actions, and the `theme.copyAction` paint token; version 19 adds provider-owned history
 enumeration and review planning; version 18 lets lifecycle and custom-event handlers request
@@ -1399,7 +1401,7 @@ Marks are addressed by **source coordinates**, never by rendered rows: `side`
 (`"old"` or `"new"`), a 1-based `line` on that side, and a `[start, end)`
 range in UTF-16 code units of the line's raw text — exactly what `indexOf` and
 `RegExp.exec` return against `file.patch` lines or a `readDocument` result.
-That addressing survives split vs stack layout, line wrapping, horizontal
+That addressing survives split vs unified layout, line wrapping, horizontal
 scrolling, and collapsed-context expansion, and the extension never learns
 Hunk's row model. A context line may be addressed through either side's line
 number; split view mirrors the mark onto both halves of the row. Offsets that
@@ -1963,28 +1965,38 @@ normal cancel value, and workspace reads or not-yet-started writes return
 filesystem write starts, it reports its actual outcome and success reconciles
 the review then active.
 
-| Event                  | Payload                 | When                                                      |
-| ---------------------- | ----------------------- | --------------------------------------------------------- |
-| `startup`              | `{ cwd }`               | once per loaded instance, after its review UI mounts      |
-| `changeset_loaded`     | `{ changeset }`         | first load and every reload                               |
-| `command_executed`     | `{ commandId }`         | after a named command dispatches in this terminal host    |
-| `selection_changed`    | `{ fileId, hunkIndex }` | when the review selection settles (debounced ~150ms)      |
-| `file_viewed`          | `{ file, hunkIndex }`   | when selection settles on a file or a reload replaces it  |
-| `hunk_viewed`          | `{ file, hunkIndex }`   | when selection settles on a different hunk                |
-| `filter_changed`       | `{ filter }`            | whenever the file-filter query changes                    |
-| `theme_changed`        | `{ themeId }`           | when the user commits a new theme                         |
-| `layout_changed`       | `{ mode, layout }`      | mode or responsive split/stack layout changes             |
-| `watch_reload_pending` | `{}`                    | watcher observed a change before its reload check         |
-| `note_created`         | `{ note }`              | a user saves an inline review note                        |
-| `note_edited`          | `{ note }`              | a draft body changes or an existing note is saved         |
-| `note_changed`         | `{ kind, note }`        | a saved ReviewStore note is created, updated, or removed  |
-| `session_reload`       | `{ changeset, reason }` | on every session reload                                   |
-| `shutdown`             | `{}`                    | before instance replacement or exit, with a short timeout |
+| Event                  | Payload                                              | When                                                      |
+| ---------------------- | ---------------------------------------------------- | --------------------------------------------------------- |
+| `startup`              | `{ cwd }`                                            | once per loaded instance, after its review UI mounts      |
+| `changeset_loaded`     | `{ changeset }`                                      | first load and every reload                               |
+| `command_executed`     | `{ commandId, canonicalCommandId? }`                 | after a named command dispatches in this terminal host    |
+| `selection_changed`    | `{ fileId, hunkIndex }`                              | when the review selection settles (debounced ~150ms)      |
+| `file_viewed`          | `{ file, hunkIndex }`                                | when selection settles on a file or a reload replaces it  |
+| `hunk_viewed`          | `{ file, hunkIndex }`                                | when selection settles on a different hunk                |
+| `filter_changed`       | `{ filter }`                                         | whenever the file-filter query changes                    |
+| `theme_changed`        | `{ themeId }`                                        | when the user commits a new theme                         |
+| `layout_changed`       | `{ mode, layout, canonicalMode?, canonicalLayout? }` | mode or responsive split/unified layout changes           |
+| `watch_reload_pending` | `{}`                                                 | watcher observed a change before its reload check         |
+| `note_created`         | `{ note }`                                           | a user saves an inline review note                        |
+| `note_edited`          | `{ note }`                                           | a draft body changes or an existing note is saved         |
+| `note_changed`         | `{ kind, note }`                                     | a saved ReviewStore note is created, updated, or removed  |
+| `session_reload`       | `{ changeset, reason }`                              | on every session reload                                   |
+| `shutdown`             | `{}`                                                 | before instance replacement or exit, with a short timeout |
 
 A newly mounted extension instance receives `startup` before its first
 `changeset_loaded`; reloads then deliver `changeset_loaded` before
 `session_reload` once the matching review generation has committed.
 
+Starting with extension API v23, `layout_changed` adds `canonicalMode` and
+`canonicalLayout`. They emit `"auto"`, `"split"`, or `"unified"` for the mode and
+`"split"` or `"unified"` for its resolved layout. The original `mode` and `layout`
+fields remain available for compatibility and continue to report `"stack"`
+where their canonical counterparts report `"unified"`. To preserve exhaustive
+existing source, `ExtensionLayoutMode` and `ExtensionResolvedLayout` retain their
+pre-v23 shapes; new extensions use `ExtensionCanonicalLayoutMode` and
+`ExtensionCanonicalResolvedLayout`. Hunk will keep the deprecated `"stack"`
+literal and legacy event fields until a separately announced major API revision.
+
 `selection_changed` is trailing-debounced on purpose: holding `[`/`]` retargets
 the selection many times a second, and handlers only care where the user landed.
 `fileId` and `hunkIndex` are `null` when nothing is selected.
@@ -1995,9 +2007,10 @@ does not fire for current-line movement within a hunk. `file_viewed` still fires
 only when the selected file object changes, so a soft reload can report a fresh
 file without counting as a new hunk read.
 
-`command_executed` reports the stable canonical command id after the terminal dispatcher invokes
+`command_executed` reports a stable command id after the terminal dispatcher invokes
 it, whether the user reached it through a key, a menu, an old command alias, or
-`ctx.commands.execute`. Extension commands
+`ctx.commands.execute`. When a command was renamed, `commandId` preserves its deprecated
+identity for existing handlers and `canonicalCommandId` names the replacement. Extension commands
 may still have detached async work in flight; this event observes the accepted user action, not
 promise settlement. Listen for ids rather than key chords so behavior follows the user's live
 `[keybindings]` table. Browser/session actions lower to shared review intents rather than terminal
diff --git a/docs/keybindings.md b/docs/keybindings.md
index 5b68f62ad..67b5143ce 100644
--- a/docs/keybindings.md
+++ b/docs/keybindings.md
@@ -108,7 +108,7 @@ an ordered provider-owned parent; they do not navigate the history selection to
 | `hunk.view.cursorLineRow`                      | Highlight the current row                      | _(none)_                     |
 | `hunk.view.layoutAuto`                         | Auto layout                                    | `0`                          |
 | `hunk.view.layoutSplit`                        | Split layout                                   | `1`                          |
-| `hunk.view.layoutStack`                        | Stack layout                                   | `2`                          |
+| `hunk.view.layoutUnified`                      | Unified layout                                 | `2`                          |
 | `hunk.view.openThemeSelector`                  | Choose theme                                   | `t`                          |
 | `hunk.view.toggleAgentNotes`                   | Toggle agent notes                             | `a`                          |
 | `hunk.view.toggleCopyDecorations`              | Toggle copy decorations                        | _(none)_                     |
@@ -124,7 +124,9 @@ replacement on any terminal edge without changing unrelated panes. Remapping or
 unbinding `hunk.view.toggleFilesPane` changes that role-aware action, not an
 extension pane's own commands. The former `hunk.view.toggleSidebar` id remains a
 compatibility alias; prefer the files-pane name in new config and extension
-code.
+code. Likewise, `hunk.view.layoutStack` remains a deprecated alias for
+`hunk.view.layoutUnified`, so existing keybindings and extension command calls
+continue to select the canonical unified layout.
 
 Commands marked _(none)_ ship without a key: they remain callable by command id
 and can be assigned a shortcut through `[keybindings]`. Some also appear in a
diff --git a/docs/opentui-component.md b/docs/opentui-component.md
index 5cc67b5ae..ad50e7cca 100644
--- a/docs/opentui-component.md
+++ b/docs/opentui-component.md
@@ -65,7 +65,7 @@ In a real app, derive `width` from your layout or `useTerminalDimensions()`.
 `HunkDiffView` renders one file and can own an OpenTUI `scrollbox`:
 
 ```tsx
-<HunkDiffView diff={file} width={88} layout="split" scrollable />
+<HunkDiffView diff={file} width={88} canonicalLayout="split" scrollable />
 ```
 
 Use it when you just want a drop-in diff viewer.
@@ -76,7 +76,7 @@ Use it when you just want a drop-in diff viewer.
 
 ```tsx
 <scrollbox width="100%" height="100%" scrollY>
-  <HunkDiffBody file={file} width={88} layout="stack" selectedHunkIndex={2} />
+  <HunkDiffBody file={file} width={88} canonicalLayout="unified" selectedHunkIndex={2} />
 </scrollbox>
 ```
 
@@ -190,9 +190,14 @@ If you need direct access to Pierre's parser, `parsePatchFiles(...)` is still re
 
 ## Common props
 
+Use `canonicalLayout` in new integrations. The legacy `layout` prop and `HunkDiffLayout` type keep
+their original `split | stack` shape so existing exhaustive TypeScript consumers continue to
+compile; when both props are present, `canonicalLayout` wins.
+
 | Prop                 | Type                                                                                                                                                       | Default      | Notes                                                                               |
 | -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------ | ----------------------------------------------------------------------------------- |
-| `layout`             | `"split" \| "stack"`                                                                                                                                       | `"split"`    | Chooses side-by-side or stacked rendering.                                          |
+| `canonicalLayout`    | `"split" \| "unified"`                                                                                                                                     | `"split"`    | Chooses side-by-side or unified rendering in new integrations.                      |
+| `layout`             | `"split" \| "stack"`                                                                                                                                       | `undefined`  | Legacy source-compatible input; `stack` renders as unified.                         |
 | `width`              | `number`                                                                                                                                                   | —            | Required content width in terminal columns.                                         |
 | `theme`              | `"graphite" \| "midnight" \| "paper" \| "ember" \| "catppuccin-latte" \| "catppuccin-frappe" \| "catppuccin-macchiato" \| "catppuccin-mocha" \| "zenburn"` | `"graphite"` | Matches Hunk's built-in themes.                                                     |
 | `showLineNumbers`    | `boolean`                                                                                                                                                  | `true`       | Toggles line-number columns.                                                        |
@@ -217,6 +222,7 @@ If you need direct access to Pierre's parser, `parsePatchFiles(...)` is still re
 - `countHunkDiffStats`
 - `HUNK_DIFF_THEME_NAMES`
 - `HunkDiffThemeName`
+- `CanonicalHunkDiffLayout`
 - `HunkDiffLayout`
 - `HunkDiffFile`
 - `HunkDiffFileInput`
diff --git a/examples/4-ui-polish/README.md b/examples/4-ui-polish/README.md
index 99871555d..1a9effafd 100644
--- a/examples/4-ui-polish/README.md
+++ b/examples/4-ui-polish/README.md
@@ -12,4 +12,4 @@ hunk diff --files examples/4-ui-polish/before.tsx examples/4-ui-polish/after.tsx
 
 - renamed props and extracted button-label helper
 - nice intra-line emphasis in strings and labels
-- a compact UI-focused diff that looks good in split and stacked layouts
+- a compact UI-focused diff that looks good in split and unified layouts
diff --git a/examples/5-pager-tour/after.ts b/examples/5-pager-tour/after.ts
index e679fef16..221f494b9 100644
--- a/examples/5-pager-tour/after.ts
+++ b/examples/5-pager-tour/after.ts
@@ -34,7 +34,7 @@ export const tourLine24 =
   "Readable filler text makes navigation practice feel intentional instead of synthetic.";
 export const tourLine25 = "A few distinct hunks are better than one endless wall of edits.";
 export const tourLine26 = "Split view is great when you want both sides visible at once.";
-export const tourLine27 = "Stack view can feel calmer when lines are long or heavily wrapped.";
+export const tourLine27 = "Unified view can feel calmer when lines are long or heavily wrapped.";
 export const tourLine28 =
   "Pager mode should stay familiar to people who already live in git diff and less.";
 export const tourLine29 =
diff --git a/examples/5-pager-tour/before.ts b/examples/5-pager-tour/before.ts
index 5a902fdf0..7449add87 100644
--- a/examples/5-pager-tour/before.ts
+++ b/examples/5-pager-tour/before.ts
@@ -24,7 +24,7 @@ export const tourLine23 = "The best demos let you try scrolling without any setu
 export const tourLine24 = "Readable filler text keeps navigation practice from feeling fake.";
 export const tourLine25 = "A few distinct hunks are better than one endless wall of edits.";
 export const tourLine26 = "Split view is great when you want both sides visible at once.";
-export const tourLine27 = "Stack view can feel calmer when lines are long.";
+export const tourLine27 = "Unified view can feel calmer when lines are long.";
 export const tourLine28 = "Pager mode should stay familiar to people who live in git diff.";
 export const tourLine29 = "Clean copy changes are useful because they are easy to scan.";
 export const tourLine30 = "Repeated line structure makes scrolling behavior obvious.";
diff --git a/examples/7-opentui-component/README.md b/examples/7-opentui-component/README.md
index 48a87ba89..94d1c7677 100644
--- a/examples/7-opentui-component/README.md
+++ b/examples/7-opentui-component/README.md
@@ -16,7 +16,7 @@ bun run examples/7-opentui-component/from-patch.tsx
 - embedding `HunkDiffView` inside a normal OpenTUI app shell
 - building `diff.metadata` with `parseDiffFromFile`
 - parsing raw unified diff text with `parsePatchFiles`
-- switching between split and stacked layouts with example shell controls
+- switching between split and unified layouts with example shell controls
 - a scrollable terminal diff component that other OpenTUI apps can reuse
 
 The in-repo demos import from `../../packages/hunk/src/opentui` so they run from source. Published consumers should import from `hunkdiff/opentui` instead.
diff --git a/examples/7-opentui-component/support.tsx b/examples/7-opentui-component/support.tsx
index c1fe2c5e7..83809aeab 100644
--- a/examples/7-opentui-component/support.tsx
+++ b/examples/7-opentui-component/support.tsx
@@ -3,7 +3,7 @@ import path from "node:path";
 import { createCliRenderer } from "@opentui/core";
 import { createRoot, useTerminalDimensions } from "@opentui/react";
 import { useState } from "react";
-import type { HunkDiffFile, HunkDiffLayout } from "../../packages/hunk/src/opentui";
+import type { CanonicalHunkDiffLayout, HunkDiffFile } from "../../packages/hunk/src/opentui";
 import { HunkDiffView } from "../../packages/hunk/src/opentui";
 import { fitText } from "../../packages/hunk/src/ui/lib/text";
 
@@ -11,7 +11,7 @@ interface ExampleProps {
   title: string;
   subtitle: string;
   diff: HunkDiffFile;
-  layout?: HunkDiffLayout;
+  layout?: CanonicalHunkDiffLayout;
 }
 
 /** Read one checked-in example file relative to this folder. */
@@ -76,14 +76,19 @@ function ExampleApp({ title, subtitle, diff, layout = "split" }: ExampleProps) {
         />
         <box style={{ width: 1, height: 1 }} />
         <LayoutButton
-          active={activeLayout === "stack"}
-          label="Stack"
-          onPress={() => setActiveLayout("stack")}
+          active={activeLayout === "unified"}
+          label="Unified"
+          onPress={() => setActiveLayout("unified")}
         />
       </box>
       <box style={{ height: 1 }} />
       <box style={{ flexGrow: 1 }}>
-        <HunkDiffView diff={diff} layout={activeLayout} width={diffWidth} theme="midnight" />
+        <HunkDiffView
+          diff={diff}
+          canonicalLayout={activeLayout}
+          width={diffWidth}
+          theme="midnight"
+        />
       </box>
     </box>
   );
diff --git a/examples/8-opentui-primitives/README.md b/examples/8-opentui-primitives/README.md
index 5a443929c..52b028ced 100644
--- a/examples/8-opentui-primitives/README.md
+++ b/examples/8-opentui-primitives/README.md
@@ -17,6 +17,6 @@ bun run examples/8-opentui-primitives/primitives-demo.tsx
 - `HunkReviewStream` for a multi-file review stream without Hunk's menu bar or global shortcuts
 - `HunkDiffFileHeader` and `HunkDiffBody` for a single-file view assembled by the host app
 - Host-owned window borders/chrome around each primitive so you can inspect component boundaries
-- Host-owned state for selected file and split/stack layout
+- Host-owned state for selected file and split/unified layout
 
 The in-repo demo imports from `../../packages/hunk/src/opentui` so it runs from source. Published consumers should import from `hunkdiff/opentui` instead.
diff --git a/examples/8-opentui-primitives/primitives-demo.tsx b/examples/8-opentui-primitives/primitives-demo.tsx
index 2f193825d..ba20cf969 100644
--- a/examples/8-opentui-primitives/primitives-demo.tsx
+++ b/examples/8-opentui-primitives/primitives-demo.tsx
@@ -9,7 +9,7 @@ import {
   HunkFileNav,
   HunkReviewStream,
   createHunkDiffFilesFromPatch,
-  type HunkDiffLayout,
+  type CanonicalHunkDiffLayout,
 } from "../../packages/hunk/src/opentui";
 import { fitText, padText } from "../../packages/hunk/src/ui/lib/text";
 
@@ -108,7 +108,7 @@ function WindowFrame({
 function PrimitivesDemoApp({ onQuit }: { onQuit: () => void }) {
   const terminal = useTerminalDimensions();
   const files = useMemo(() => createHunkDiffFilesFromPatch(PATCH, "primitives-demo"), []);
-  const [layout, setLayout] = useState<HunkDiffLayout>("split");
+  const [layout, setLayout] = useState<CanonicalHunkDiffLayout>("split");
   const [selectedFileId, setSelectedFileId] = useState(files[0]?.id ?? "");
   const selectedFile = files.find((file) => file.id === selectedFileId) ?? files[0];
   const sidebarWidth = Math.min(34, Math.max(24, Math.floor(terminal.width * 0.28)));
@@ -132,7 +132,7 @@ function PrimitivesDemoApp({ onQuit }: { onQuit: () => void }) {
     }
 
     if (key.name === "2") {
-      setLayout("stack");
+      setLayout("unified");
       return;
     }
 
@@ -159,7 +159,7 @@ function PrimitivesDemoApp({ onQuit }: { onQuit: () => void }) {
         <text fg="#eef4ff">
           {padText(
             fitText(
-              " Hunk primitives as app windows — q quit · Tab next file · 1 split · 2 stack ",
+              " Hunk primitives as app windows — q quit · Tab next file · 1 split · 2 unified ",
               Math.max(1, terminal.width - 2),
             ),
             Math.max(1, terminal.width - 2),
@@ -217,7 +217,7 @@ function PrimitivesDemoApp({ onQuit }: { onQuit: () => void }) {
             >
               <HunkDiffBody
                 file={selectedFile}
-                layout={layout}
+                canonicalLayout={layout}
                 width={Math.max(20, mainWidth - 4)}
                 theme="midnight"
               />
@@ -236,7 +236,7 @@ function PrimitivesDemoApp({ onQuit }: { onQuit: () => void }) {
             >
               <HunkReviewStream
                 files={files}
-                layout={layout}
+                canonicalLayout={layout}
                 width={Math.max(20, mainWidth - 4)}
                 theme="midnight"
                 selection={{ fileId: selectedFile?.id ?? "", hunkIndex: 0 }}
diff --git a/examples/extensions/github-pr/README.md b/examples/extensions/github-pr/README.md
index 642e585f1..6ae4e728e 100644
--- a/examples/extensions/github-pr/README.md
+++ b/examples/extensions/github-pr/README.md
@@ -27,7 +27,7 @@ hunk gh https://github.com/modem-dev/hunk/pull/123
 Quote the `owner/repo#number` form because an unquoted `#` starts a comment in some shells. Use `--` to pass options to the delegated `hunk patch` command:
 
 ```bash
-hunk gh 123 --repo modem-dev/hunk -- --pager --mode stack
+hunk gh 123 --repo modem-dev/hunk -- --pager --mode unified
 ```
 
 Run `hunk gh --help` for the extension-owned help text.
diff --git a/examples/extensions/jsx-file-view-gallery/README.md b/examples/extensions/jsx-file-view-gallery/README.md
index eb097c91b..1ebfa02aa 100644
--- a/examples/extensions/jsx-file-view-gallery/README.md
+++ b/examples/extensions/jsx-file-view-gallery/README.md
@@ -9,7 +9,7 @@ Nested boxes, responsive meters, semantic color, and selected-hunk styling summa
 ```bash
 bun run packages/hunk/src/main.tsx -- diff \
   --extension ./examples/extensions/jsx-file-view-gallery \
-  --mode stack \
+  --mode unified \
   examples/extensions/jsx-file-view-gallery/fixtures/change-atlas/before.ts \
   examples/extensions/jsx-file-view-gallery/fixtures/change-atlas/after.ts
 ```
@@ -21,7 +21,7 @@ The extension lazily reads both exact documents, associates changed opaque three
 ```bash
 bun run packages/hunk/src/main.tsx -- diff \
   --extension ./examples/extensions/jsx-file-view-gallery \
-  --mode stack \
+  --mode unified \
   examples/extensions/jsx-file-view-gallery/fixtures/css-palette/before.css \
   examples/extensions/jsx-file-view-gallery/fixtures/css-palette/after.css
 ```
@@ -33,7 +33,7 @@ A conservative package-file parser highlights only the changed semantic-version
 ```bash
 bun run packages/hunk/src/main.tsx -- diff \
   --extension ./examples/extensions/jsx-file-view-gallery \
-  --mode stack \
+  --mode unified \
   examples/extensions/jsx-file-view-gallery/fixtures/package-dependencies/before/package.json \
   examples/extensions/jsx-file-view-gallery/fixtures/package-dependencies/after/package.json
 ```
diff --git a/examples/extensions/jsx-file-view-gallery/mixed-review/fixtures/after/README.md b/examples/extensions/jsx-file-view-gallery/mixed-review/fixtures/after/README.md
index cdba4d875..f0d78949a 100644
--- a/examples/extensions/jsx-file-view-gallery/mixed-review/fixtures/after/README.md
+++ b/examples/extensions/jsx-file-view-gallery/mixed-review/fixtures/after/README.md
@@ -30,7 +30,7 @@ The repository file may define a theme, default layout, ignored paths, and exten
 ```json
 {
   "theme": "midnight",
-  "layout": "stack",
+  "layout": "unified",
   "ignored": ["dist/**"],
   "extensions": ["./review-extensions"]
 }
diff --git a/examples/extensions/jsx-file-view-gallery/mixed-review/run.ts b/examples/extensions/jsx-file-view-gallery/mixed-review/run.ts
index f8a048379..ee291d6f0 100644
--- a/examples/extensions/jsx-file-view-gallery/mixed-review/run.ts
+++ b/examples/extensions/jsx-file-view-gallery/mixed-review/run.ts
@@ -79,7 +79,7 @@ try {
       "--extension",
       galleryRoot,
       "--mode",
-      "stack",
+      "unified",
     ],
     { cwd: demoRepo, stdio: "inherit", env: process.env },
   );
diff --git a/packages/hunk/README.md b/packages/hunk/README.md
index 1811d16ec..c3c4d4c61 100644
--- a/packages/hunk/README.md
+++ b/packages/hunk/README.md
@@ -11,21 +11,21 @@ Hunk is a review-first terminal diff viewer for agent-authored changesets, built
 
 - multi-file review stream with sidebar navigation
 - inline AI and agent annotations beside the code
-- split, stack, and responsive auto layouts
+- split, unified, and responsive auto layouts
 - watch mode for auto-reloading file and Git-backed reviews
 - keyboard, mouse, pager, and Git difftool support
 
 <table>
  <tr>
    <td width="60%" align="center">
-    <img width="845" alt="image" src="https://github.com/user-attachments/assets/35605618-be3f-479e-b6e0-edb089910651" />
+     <img width="845" alt="image" src="https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/review-stream.webp" />
      <br />
      <sub>Split view with sidebar and inline AI notes</sub>
    </td>
    <td width="40%" align="center">
-     <img width="507"alt="image" src="https://github.com/user-attachments/assets/92eb8993-f044-436d-a038-8139da5ad8de" />
+     <img width="507"alt="image" src="https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/agent-comments.webp" />
      <br />
-     <sub>Stacked view and mouse-selectable menus</sub>
+     <sub>Unified view and mouse-selectable menus</sub>
    </td>
  </tr>
 </table>
@@ -135,17 +135,17 @@ For the full live-session and `--agent-context` workflow guide, see [the agent w
 
 ## Feature comparison
 
-| Capability                         | [hunk](https://github.com/modem-dev/hunk) | [lumen](https://github.com/jnsahaj/lumen) | [difftastic](https://github.com/Wilfred/difftastic) | [delta](https://github.com/dandavison/delta) | [diff-so-fancy](https://github.com/so-fancy/diff-so-fancy) | [diff](https://www.gnu.org/software/diffutils/) |
-| ---------------------------------- | ----------------------------------------- | ----------------------------------------- | --------------------------------------------------- | -------------------------------------------- | ---------------------------------------------------------- | ----------------------------------------------- |
-| Review-first interactive UI        | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Multi-file review stream + sidebar | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Inline agent / AI annotations      | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Responsive auto split/stack layout | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Mouse support inside the viewer    | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Runtime view toggles               | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Syntax highlighting                | ✅                                        | ✅                                        | ✅                                                  | ✅                                           | ❌                                                         | ❌                                              |
-| Structural diffing                 | ❌                                        | ❌                                        | ✅                                                  | ❌                                           | ❌                                                         | ❌                                              |
-| Pager-compatible mode              | ✅                                        | ❌                                        | ✅                                                  | ✅                                           | ✅                                                         | ✅                                              |
+| Capability                           | [hunk](https://github.com/modem-dev/hunk) | [lumen](https://github.com/jnsahaj/lumen) | [difftastic](https://github.com/Wilfred/difftastic) | [delta](https://github.com/dandavison/delta) | [diff-so-fancy](https://github.com/so-fancy/diff-so-fancy) | [diff](https://www.gnu.org/software/diffutils/) |
+| ------------------------------------ | ----------------------------------------- | ----------------------------------------- | --------------------------------------------------- | -------------------------------------------- | ---------------------------------------------------------- | ----------------------------------------------- |
+| Review-first interactive UI          | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Multi-file review stream + sidebar   | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Inline agent / AI annotations        | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Responsive auto split/unified layout | ✅                                        | ❌                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Mouse support inside the viewer      | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Runtime view toggles                 | ✅                                        | ✅                                        | ❌                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Syntax highlighting                  | ✅                                        | ✅                                        | ✅                                                  | ✅                                           | ❌                                                         | ❌                                              |
+| Structural diffing                   | ❌                                        | ❌                                        | ✅                                                  | ❌                                           | ❌                                                         | ❌                                              |
+| Pager-compatible mode                | ✅                                        | ❌                                        | ✅                                                  | ✅                                           | ✅                                                         | ✅                                              |
 
 Hunk is optimized for reviewing a full changeset interactively.
 
@@ -162,7 +162,7 @@ Example:
 
 ```toml
 theme = "github-dark-default" # any built-in theme id, auto, or custom
-mode = "auto"        # auto, split, stack
+mode = "auto"        # auto, split, unified
 vcs = "git"          # git, jj, sl
 watch = false
 exclude_untracked = false
diff --git a/packages/hunk/skills/hunk-extensions/SKILL.md b/packages/hunk/skills/hunk-extensions/SKILL.md
index 2dcc21106..31867b9f6 100644
--- a/packages/hunk/skills/hunk-extensions/SKILL.md
+++ b/packages/hunk/skills/hunk-extensions/SKILL.md
@@ -111,7 +111,7 @@ bad or duplicate id is skipped with a startup notice.
 | Reload after an external agent changes reviewed inputs   | `ctx.review.requestReload()` in an event     |
 | Read user-supplied settings                              | `hunk.config` (`[extension.<id>]` table)     |
 | Snapshot stable files and every saved review note        | `ctx.review.snapshot()` in a command         |
-| Branch on the API generation (currently `18`)            | `hunk.apiVersion`                            |
+| Branch on the API generation (currently `21`)            | `hunk.apiVersion`                            |
 
 Registration is only valid while the factory runs — Hunk seals the API object
 afterwards.
diff --git a/packages/hunk/src/app/cli.test.ts b/packages/hunk/src/app/cli.test.ts
index 20311ffb3..856bf88d5 100644
--- a/packages/hunk/src/app/cli.test.ts
+++ b/packages/hunk/src/app/cli.test.ts
@@ -64,6 +64,8 @@ describe("parseCli", () => {
     expect(parsed.text).toContain("hunk skill path");
     expect(parsed.text).toContain("Global options:");
     expect(parsed.text).toContain("Common review options:");
+    expect(parsed.text).toContain("layout mode: auto, split, unified");
+    expect(parsed.text).not.toContain("layout mode: auto, split, stack");
     expect(parsed.text).toContain("--file-gap");
     expect(parsed.text).toContain("file separator rows, including ─");
     expect(parsed.text).toContain("--hunk-gap");
@@ -387,14 +389,23 @@ describe("parseCli", () => {
       left,
       right,
       "--mode",
-      "stack",
+      "unified",
     ]);
 
     expect(parsed).toMatchObject({
       kind: "diff",
       left,
       right,
-      options: { mode: "stack" },
+      options: { mode: "unified" },
+    });
+  });
+
+  test("normalizes the deprecated stack layout input to unified", async () => {
+    const parsed = await parseCli(["bun", "hunk", "diff", "--mode", "stack"]);
+
+    expect(parsed).toMatchObject({
+      kind: "vcs",
+      options: { mode: "unified" },
     });
   });
 
@@ -1803,7 +1814,7 @@ describe("parseCli", () => {
       "right.ts",
       "src/example.ts",
       "--mode",
-      "stack",
+      "unified",
     ]);
 
     expect(parsed).toMatchObject({
@@ -1812,7 +1823,7 @@ describe("parseCli", () => {
       right: "right.ts",
       path: "src/example.ts",
       options: {
-        mode: "stack",
+        mode: "unified",
       },
     });
     if (parsed.kind !== "difftool") {
diff --git a/packages/hunk/src/app/cli.ts b/packages/hunk/src/app/cli.ts
index ca8197705..f5ed164a7 100644
--- a/packages/hunk/src/app/cli.ts
+++ b/packages/hunk/src/app/cli.ts
@@ -1,18 +1,20 @@
 import { existsSync, realpathSync } from "node:fs";
 import { resolve } from "node:path";
 import { Command, Option } from "commander";
-import type {
-  CliInput,
-  CommonOptions,
-  CursorLine,
-  ExtensionManageCommandInput,
-  HelpCommandInput,
-  LayoutMode,
-  PagerCommandInput,
-  ParsedCliInput,
-  SelfUpdateCommandInput,
-  SessionCommentListType,
-  SessionCommentApplyItemInput,
+import {
+  isLayoutModeInput,
+  normalizeLayoutModeInput,
+  type CliInput,
+  type CommonOptions,
+  type CursorLine,
+  type ExtensionManageCommandInput,
+  type HelpCommandInput,
+  type LayoutMode,
+  type PagerCommandInput,
+  type ParsedCliInput,
+  type SelfUpdateCommandInput,
+  type SessionCommentListType,
+  type SessionCommentApplyItemInput,
 } from "../core/run/commandInputs";
 import {
   isBuiltInCliCommandName,
@@ -97,7 +99,7 @@ export interface CliReferenceCommand {
 
 /** Review flags registered on every full-screen review command. */
 export const COMMON_REVIEW_OPTIONS = [
-  { flag: "--mode <mode>", description: "layout mode: auto, split, stack", parse: "layout" },
+  { flag: "--mode <mode>", description: "layout mode: auto, split, unified", parse: "layout" },
   {
     flag: "--cursor-line <style>",
     description: "current-line marker: row, number, off",
@@ -365,8 +367,8 @@ export const CLI_REFERENCE_COMMANDS = {
 
 /** Validate one requested layout mode from CLI input. */
 function parseLayoutMode(value: string): LayoutMode {
-  if (value === "auto" || value === "split" || value === "stack") {
-    return value;
+  if (isLayoutModeInput(value)) {
+    return normalizeLayoutModeInput(value);
   }
 
   throw new Error(`Invalid layout mode: ${value}`);
@@ -597,7 +599,7 @@ function renderCliHelp() {
     "  --fast                                  review working tree with experimental fast highlighting",
     "",
     "Common review options:",
-    "  --mode <mode>                           layout mode: auto, split, stack",
+    "  --mode <mode>                           layout mode: auto, split, unified",
     "  --watch                                 auto-reload when the current diff input changes",
     "  --agent-context <path>                  JSON sidecar with agent rationale",
     "  --pager                                 use pager-style chrome",
diff --git a/packages/hunk/src/core/run/commandCatalog.test.ts b/packages/hunk/src/core/run/commandCatalog.test.ts
index a0be55309..a31731e90 100644
--- a/packages/hunk/src/core/run/commandCatalog.test.ts
+++ b/packages/hunk/src/core/run/commandCatalog.test.ts
@@ -45,6 +45,7 @@ describe("app command catalog", () => {
       }
     }
     expect(appCommandCatalogEntry("hunk.view.toggleSidebar")?.id).toBe("hunk.view.toggleFilesPane");
+    expect(appCommandCatalogEntry("hunk.view.layoutStack")?.id).toBe("hunk.view.layoutUnified");
   });
 
   test("declares a review effect for semantic commands and nothing else", () => {
diff --git a/packages/hunk/src/core/run/commandCatalog.ts b/packages/hunk/src/core/run/commandCatalog.ts
index 704781aca..0724b8e73 100644
--- a/packages/hunk/src/core/run/commandCatalog.ts
+++ b/packages/hunk/src/core/run/commandCatalog.ts
@@ -345,8 +345,9 @@ const BUILTIN_COMMANDS = [
     closesMenu: true,
   },
   {
-    id: "hunk.view.layoutStack",
-    title: "Stack layout",
+    id: "hunk.view.layoutUnified",
+    aliases: ["hunk.view.layoutStack"],
+    title: "Unified layout",
     category: "view",
     defaultKeys: ["2"],
     locus: "client-local",
diff --git a/packages/hunk/src/core/run/commandInputs.ts b/packages/hunk/src/core/run/commandInputs.ts
index 5713d571a..7312c19f0 100644
--- a/packages/hunk/src/core/run/commandInputs.ts
+++ b/packages/hunk/src/core/run/commandInputs.ts
@@ -15,7 +15,19 @@ import type {
 } from "../../extension-api/types";
 import type { InstallSource } from "../install/installSource";
 
-export type LayoutMode = "auto" | "split" | "stack";
+export type LayoutMode = "auto" | "split" | "unified";
+export type LayoutModeInput = LayoutMode | "stack";
+
+/** Return whether an unknown value uses canonical or deprecated layout vocabulary. */
+export function isLayoutModeInput(value: unknown): value is LayoutModeInput {
+  return value === "auto" || value === "split" || value === "unified" || value === "stack";
+}
+
+/** Normalize canonical and deprecated layout inputs without widening runtime state. */
+export function normalizeLayoutModeInput(value: LayoutModeInput): LayoutMode {
+  return value === "stack" ? "unified" : value;
+}
+
 export type CursorLine = "row" | "number" | "off";
 export type SidebarVisibility = boolean | "auto";
 export type VcsMode = string;
diff --git a/packages/hunk/src/core/run/config.test.ts b/packages/hunk/src/core/run/config.test.ts
index 9b5f312e7..9bdd0ebd3 100644
--- a/packages/hunk/src/core/run/config.test.ts
+++ b/packages/hunk/src/core/run/config.test.ts
@@ -67,6 +67,7 @@ describe("config persistence", () => {
       [
         "# personal defaults",
         'theme = "github-dark-default"',
+        'mode = "stack"',
         "wrap_lines = false",
         "",
         "[custom_theme]",
@@ -76,7 +77,7 @@ describe("config persistence", () => {
 
     const savedPath = saveGlobalViewPreferences(
       {
-        mode: "split",
+        mode: "unified",
         theme: "dracula",
         showLineNumbers: false,
         wrapLines: true,
@@ -94,8 +95,8 @@ describe("config persistence", () => {
       [
         "# personal defaults",
         'theme = "dracula"',
+        'mode = "unified"',
         "wrap_lines = true",
-        'mode = "split"',
         "line_numbers = false",
         "hunk_headers = false",
         "menu_bar = false",
@@ -213,7 +214,7 @@ describe("config resolution", () => {
     expect(resolved.viewPreferencesConfigPath).toBe(join(repo, ".hunk", "config.toml"));
     expect(resolved.input.options).toMatchObject({
       pager: true,
-      mode: "stack",
+      mode: "unified",
       theme: "github-light-default",
       lineNumbers: false,
       tabWidth: 6,
@@ -819,7 +820,7 @@ describe("config resolution", () => {
     mkdirSync(join(home, ".config", "hunk"), { recursive: true });
     writeFileSync(
       join(home, ".config", "hunk", "config.toml"),
-      ["[show]", 'mode = "stack"', "line_numbers = false"].join("\n"),
+      ["[show]", 'mode = "unified"', "line_numbers = false"].join("\n"),
     );
 
     const resolved = resolveConfiguredCliInput(
@@ -831,7 +832,7 @@ describe("config resolution", () => {
       { cwd: createTempDir("hunk-config-cwd-"), env: { HOME: home } },
     );
 
-    expect(resolved.input.options.mode).toBe("stack");
+    expect(resolved.input.options.mode).toBe("unified");
     expect(resolved.input.options.lineNumbers).toBe(false);
   });
 
diff --git a/packages/hunk/src/core/run/config.ts b/packages/hunk/src/core/run/config.ts
index 940d26f87..bb8f42481 100644
--- a/packages/hunk/src/core/run/config.ts
+++ b/packages/hunk/src/core/run/config.ts
@@ -34,13 +34,15 @@ import type {
   CustomSyntaxScopesConfig,
   NamedCustomThemeConfig,
 } from "../../extension-api/types";
-import type {
-  CliInput,
-  CommonOptions,
-  CursorLine,
-  LayoutMode,
-  SidebarVisibility,
-  VcsMode,
+import {
+  isLayoutModeInput,
+  normalizeLayoutModeInput,
+  type CliInput,
+  type CommonOptions,
+  type CursorLine,
+  type LayoutMode,
+  type SidebarVisibility,
+  type VcsMode,
 } from "./commandInputs";
 
 /** Resolved `[extensions]` and `[extension.<id>]` configuration for one invocation. */
@@ -230,11 +232,6 @@ function upsertTopLevelTomlValue(source: string, key: string, value: string | bo
   return `${lines.join("\n").replace(/\n*$/, "")}\n`;
 }
 
-/** Accept only the layout names Hunk already supports. */
-function normalizeLayoutMode(value: unknown): LayoutMode | undefined {
-  return value === "auto" || value === "split" || value === "stack" ? value : undefined;
-}
-
 /** Accept only the current-line styles the review stream can draw. */
 function normalizeCursorLine(value: unknown): CursorLine | undefined {
   return value === "row" || value === "number" || value === "off" ? value : undefined;
@@ -325,9 +322,9 @@ export const CONFIG_REFERENCE_OPTIONS: readonly ConfigReferenceOption[] = [
     key: "mode",
     property: "mode",
     type: "string",
-    accepted: "`auto`, `split`, or `stack`",
+    accepted: "`auto`, `split`, `unified`, or deprecated alias `stack`",
     runtimeDefault: DEFAULT_VIEW_PREFERENCES.mode,
-    description: "Choose responsive, side-by-side, or stacked diff layout.",
+    description: "Choose responsive, side-by-side, or unified diff layout.",
   },
   {
     key: "cursor_line",
@@ -968,7 +965,7 @@ function resolveExtensionsConfig(
 function normalizeConfigReferenceValue(property: keyof CommonOptions, value: unknown) {
   switch (property) {
     case "mode":
-      return normalizeLayoutMode(value);
+      return isLayoutModeInput(value) ? normalizeLayoutModeInput(value) : undefined;
     case "cursorLine":
       return normalizeCursorLine(value);
     case "vcs":
diff --git a/packages/hunk/src/extension-api/index.ts b/packages/hunk/src/extension-api/index.ts
index eb625a58f..39348f3ca 100644
--- a/packages/hunk/src/extension-api/index.ts
+++ b/packages/hunk/src/extension-api/index.ts
@@ -122,7 +122,10 @@ export type {
   ExtensionHorizontalPane,
   ExtensionVerticalPane,
   ExtensionCurrentLinePaint,
+  ExtensionCanonicalLayoutMode,
+  ExtensionCanonicalResolvedLayout,
   ExtensionLayoutMode,
+  ExtensionLegacyLayout,
   ExtensionResolvedLayout,
   ExtensionReviewNavigation,
   ExtensionReviewNote,
diff --git a/packages/hunk/src/extension-api/types.ts b/packages/hunk/src/extension-api/types.ts
index 3e1a08981..8bc91152c 100644
--- a/packages/hunk/src/extension-api/types.ts
+++ b/packages/hunk/src/extension-api/types.ts
@@ -21,7 +21,7 @@
  * Extensions can branch on `hunk.apiVersion` so a newer Hunk can keep loading
  * older extensions without guessing at their expectations.
  */
-export const HUNK_EXTENSION_API_VERSION = 22;
+export const HUNK_EXTENSION_API_VERSION = 23;
 export type HunkExtensionApiVersion = typeof HUNK_EXTENSION_API_VERSION;
 
 export type ExtensionNotifyType = "info" | "warning" | "error";
@@ -474,7 +474,7 @@ export type ExtensionLineHighlightTone = "match" | "current" | "info" | "warning
  * One marked character range inside one diff line.
  *
  * Addressed by source coordinates — `(side, line, range)` — rather than by
- * rendered rows, so a mark survives split vs stack layout, line wrapping,
+ * rendered rows, so a mark survives split vs unified layout, line wrapping,
  * horizontal scrolling, and collapsed-context expansion without the extension
  * ever learning Hunk's row model.
  */
@@ -2152,8 +2152,15 @@ export interface ExtensionEventContext extends ExtensionContext {
  */
 export type SessionReloadReason = "watch" | "daemon" | "extension" | "manual";
 
-/** Payload delivered with each lifecycle event, keyed by event name. */
-export type ExtensionLayoutMode = "auto" | "split" | "stack";
+/** @deprecated Use the canonical `unified` vocabulary in new integrations. */
+export type ExtensionLegacyLayout = "stack";
+/** Canonical layout mode vocabulary emitted to extensions. */
+export type ExtensionCanonicalLayoutMode = "auto" | "split" | "unified";
+/** Concrete canonical layout emitted to extensions. */
+export type ExtensionCanonicalResolvedLayout = Exclude<ExtensionCanonicalLayoutMode, "auto">;
+/** Pre-v23 layout vocabulary retained so existing extension source remains exhaustive. */
+export type ExtensionLayoutMode = "auto" | "split" | ExtensionLegacyLayout;
+/** Pre-v23 concrete layout vocabulary retained for source and event compatibility. */
 export type ExtensionResolvedLayout = Exclude<ExtensionLayoutMode, "auto">;
 
 /** A user-authored note as reported by note lifecycle events. */
@@ -2182,7 +2189,12 @@ export interface ExtensionEventPayloads {
   startup: { cwd: string };
   changeset_loaded: { changeset: ExtensionChangeset };
   /** A named built-in or extension command was dispatched in this terminal host. */
-  command_executed: { commandId: string };
+  command_executed: {
+    /** Stable command identity, including deprecated ids preserved for existing handlers. */
+    commandId: string;
+    /** Canonical replacement when `commandId` is a deprecated compatibility identity. */
+    canonicalCommandId?: string;
+  };
   selection_changed: { fileId: string | null; hunkIndex: number | null };
   /** The review stream settled on a different file. */
   file_viewed: { file: ExtensionDiffFile; hunkIndex: number | null };
@@ -2197,8 +2209,20 @@ export interface ExtensionEventPayloads {
   filter_changed: { filter: string };
   /** The user committed a different active theme. Selector previews do not emit this event. */
   theme_changed: { themeId: string };
-  /** The configured layout mode or responsive resolved layout changed. */
-  layout_changed: { mode: ExtensionLayoutMode; layout: ExtensionResolvedLayout };
+  /**
+   * The configured layout mode or responsive resolved layout changed.
+   *
+   * `mode` and `layout` preserve the pre-v23 vocabulary for existing handlers.
+   * New integrations should consume the canonical fields.
+   */
+  layout_changed: {
+    /** @deprecated Use `canonicalMode`. */
+    mode: ExtensionLayoutMode;
+    /** @deprecated Use `canonicalLayout`. */
+    layout: ExtensionResolvedLayout;
+    canonicalMode?: ExtensionCanonicalLayoutMode;
+    canonicalLayout?: ExtensionCanonicalResolvedLayout;
+  };
   /** A watch source observed a change and is waiting to check/reload it. */
   watch_reload_pending: Record<string, never>;
   /** A user saved a new inline review note. */
diff --git a/packages/hunk/src/extensions/runExtension.test.ts b/packages/hunk/src/extensions/runExtension.test.ts
index 4d1df9697..345f0f046 100644
--- a/packages/hunk/src/extensions/runExtension.test.ts
+++ b/packages/hunk/src/extensions/runExtension.test.ts
@@ -13,6 +13,10 @@ function bundledMetadata(id: string) {
 }
 
 describe("runExtensionFactory", () => {
+  test("advertises canonical layout event fields through extension API v23", () => {
+    expect(HUNK_EXTENSION_API_VERSION).toBe(23);
+  });
+
   test("applies a synchronous factory before returning, with nothing to await", () => {
     const registry = createEmptyExtensionRegistry();
     const issues: ExtensionLoadIssue[] = [];
diff --git a/packages/hunk/src/opentui/HunkDiffBody.tsx b/packages/hunk/src/opentui/HunkDiffBody.tsx
index 34ccc8a83..bbaa994cd 100644
--- a/packages/hunk/src/opentui/HunkDiffBody.tsx
+++ b/packages/hunk/src/opentui/HunkDiffBody.tsx
@@ -2,7 +2,7 @@ import { useMemo } from "react";
 import { DEFAULT_HUNK_GAP } from "../core/run/reviewGap";
 import { DEFAULT_TAB_WIDTH } from "../core/run/tabWidth";
 import { findMaxLineNumber } from "../ui/diff/codeColumns";
-import { buildSplitRows, buildStackRows } from "../ui/diff/diffRows";
+import { buildSplitRows, buildUnifiedRows } from "../ui/diff/diffRows";
 import { DiffRowView } from "../ui/diff/DiffRowView";
 import { diffMessage, fitText } from "../ui/diff/plannedRowText";
 import { buildReviewRenderPlan } from "../ui/diff/reviewRenderPlan";
@@ -10,6 +10,7 @@ import { plannedReviewRowVisible } from "../ui/diff/reviewRowGeometry";
 import { useHighlightedDiff } from "../ui/diff/useHighlightedDiff";
 import { reviewRowId } from "../ui/lib/ids";
 import { resolveTheme } from "../ui/themes";
+import { normalizeHunkDiffLayout } from "./layout";
 import { toInternalDiffFile } from "./model";
 import type { HunkDiffBodyProps } from "./types";
 
@@ -17,6 +18,7 @@ import type { HunkDiffBodyProps } from "./types";
 export function HunkDiffBody({
   file,
   layout = "split",
+  canonicalLayout,
   width,
   theme = "github-dark-default",
   showLineNumbers = true,
@@ -28,6 +30,7 @@ export function HunkDiffBody({
   highlight = true,
   selectedHunkIndex = 0,
 }: HunkDiffBodyProps) {
+  const resolvedLayout = canonicalLayout ?? normalizeHunkDiffLayout(layout);
   const resolvedTheme = resolveTheme(theme, null);
   const internalFile = useMemo(() => (file ? toInternalDiffFile(file) : undefined), [file]);
   const resolvedHighlighted = useHighlightedDiff({
@@ -38,11 +41,11 @@ export function HunkDiffBody({
   const rows = useMemo(
     () =>
       internalFile
-        ? layout === "split"
+        ? resolvedLayout === "split"
           ? buildSplitRows(internalFile, resolvedHighlighted, resolvedTheme, tabWidth)
-          : buildStackRows(internalFile, resolvedHighlighted, resolvedTheme, tabWidth)
+          : buildUnifiedRows(internalFile, resolvedHighlighted, resolvedTheme, tabWidth)
         : [],
-    [internalFile, layout, resolvedHighlighted, resolvedTheme, tabWidth],
+    [internalFile, resolvedHighlighted, resolvedLayout, resolvedTheme, tabWidth],
   );
   const plannedRows = useMemo(
     () =>
@@ -84,7 +87,7 @@ export function HunkDiffBody({
       {plannedRows.map((plannedRow) => {
         if (
           !plannedReviewRowVisible(plannedRow, {
-            layout,
+            layout: resolvedLayout,
             showHunkHeaders,
             width,
           })
diff --git a/packages/hunk/src/opentui/HunkDiffView.test.tsx b/packages/hunk/src/opentui/HunkDiffView.test.tsx
index dad55e7c1..fde34ae96 100644
--- a/packages/hunk/src/opentui/HunkDiffView.test.tsx
+++ b/packages/hunk/src/opentui/HunkDiffView.test.tsx
@@ -78,7 +78,7 @@ describe("OpenTUI public components", () => {
     const frame = await captureFrame(
       <HunkDiffBody
         file={createExampleDiff()}
-        layout="stack"
+        canonicalLayout="unified"
         theme="github-dark-default"
         width={88}
         highlight={false}
@@ -92,6 +92,44 @@ describe("OpenTUI public components", () => {
     expect(frame).toContain("  1 +  export const value = 2;");
   });
 
+  test("normalizes the deprecated stack layout prop to unified", async () => {
+    const file = createExampleDiff();
+    const canonical = await captureFrame(
+      <HunkDiffBody file={file} canonicalLayout="unified" width={88} highlight={false} />,
+      92,
+      12,
+    );
+    const legacy = await captureFrame(
+      <HunkDiffBody file={file} layout="stack" width={88} highlight={false} />,
+      92,
+      12,
+    );
+
+    expect(legacy).toBe(canonical);
+  });
+
+  test("gives the additive canonical layout prop precedence over the legacy prop", async () => {
+    const file = createExampleDiff();
+    const expected = await captureFrame(
+      <HunkDiffBody file={file} canonicalLayout="split" width={88} highlight={false} />,
+      92,
+      12,
+    );
+    const overridden = await captureFrame(
+      <HunkDiffBody
+        file={file}
+        layout="stack"
+        canonicalLayout="split"
+        width={88}
+        highlight={false}
+      />,
+      92,
+      12,
+    );
+
+    expect(overridden).toBe(expected);
+  });
+
   test("accepts a custom tab width through the public body primitive", async () => {
     const metadata = parseDiffFromFile(
       { cacheKey: "tabs-before", contents: "a\tb\n", name: "tabs.txt" },
@@ -101,7 +139,13 @@ describe("OpenTUI public components", () => {
     );
     const file = createHunkDiffFile({ id: "tabs", metadata, path: "tabs.txt" });
     const frame = await captureFrame(
-      <HunkDiffBody file={file} layout="stack" width={88} tabWidth={8} highlight={false} />,
+      <HunkDiffBody
+        file={file}
+        canonicalLayout="unified"
+        width={88}
+        tabWidth={8}
+        highlight={false}
+      />,
       92,
       8,
     );
@@ -126,7 +170,13 @@ describe("OpenTUI public components", () => {
     );
     const file = createHunkDiffFile({ id: "multi", metadata, path: "multi.ts" });
     const frame = await captureFrame(
-      <HunkDiffBody file={file} layout="stack" width={88} hunkGap={2} highlight={false} />,
+      <HunkDiffBody
+        file={file}
+        canonicalLayout="unified"
+        width={88}
+        hunkGap={2}
+        highlight={false}
+      />,
       92,
       24,
     );
diff --git a/packages/hunk/src/opentui/HunkReviewStream.tsx b/packages/hunk/src/opentui/HunkReviewStream.tsx
index 94f5ab1cb..23cef7397 100644
--- a/packages/hunk/src/opentui/HunkReviewStream.tsx
+++ b/packages/hunk/src/opentui/HunkReviewStream.tsx
@@ -1,6 +1,7 @@
 import { DEFAULT_FILE_GAP, DEFAULT_HUNK_GAP } from "../core/run/reviewGap";
 import { resolveTheme } from "../ui/themes";
 import { HunkDiffBody } from "./HunkDiffBody";
+import { normalizeHunkDiffLayout } from "./layout";
 import { HunkDiffFileHeader } from "./HunkDiffFileHeader";
 import type { HunkDiffFileInput, HunkDiffSelection, HunkReviewStreamProps } from "./types";
 
@@ -18,6 +19,7 @@ function resolveSelection(files: HunkDiffFileInput[], selection: HunkDiffSelecti
 export function HunkReviewStream({
   files,
   layout = "split",
+  canonicalLayout,
   width,
   theme = "github-dark-default",
   selection,
@@ -33,6 +35,7 @@ export function HunkReviewStream({
   highlight = true,
   onSelectionChange,
 }: HunkReviewStreamProps) {
+  const resolvedLayout = canonicalLayout ?? normalizeHunkDiffLayout(layout);
   const resolvedTheme = resolveTheme(theme, null);
   const activeSelection = resolveSelection(files, selection);
 
@@ -83,7 +86,7 @@ export function HunkReviewStream({
             ) : null}
             <HunkDiffBody
               file={file}
-              layout={layout}
+              canonicalLayout={resolvedLayout}
               width={width}
               theme={theme}
               showLineNumbers={showLineNumbers}
diff --git a/packages/hunk/src/opentui/index.ts b/packages/hunk/src/opentui/index.ts
index 50ad25121..ca7f80b80 100644
--- a/packages/hunk/src/opentui/index.ts
+++ b/packages/hunk/src/opentui/index.ts
@@ -7,11 +7,13 @@ export { HunkFileNav } from "./HunkFileNav";
 export { HunkReviewStream } from "./HunkReviewStream";
 export { countHunkDiffStats, createHunkDiffFile, createHunkDiffFilesFromPatch } from "./model";
 export type {
+  CanonicalHunkDiffLayout,
   HunkDiffBodyProps,
   HunkDiffFile,
   HunkDiffFileHeaderProps,
   HunkDiffFileInput,
   HunkDiffLayout,
+  LegacyHunkDiffLayout,
   HunkDiffSelection,
   HunkDiffStats,
   HunkDiffViewProps,
diff --git a/packages/hunk/src/opentui/layout.ts b/packages/hunk/src/opentui/layout.ts
new file mode 100644
index 000000000..803f753bd
--- /dev/null
+++ b/packages/hunk/src/opentui/layout.ts
@@ -0,0 +1,8 @@
+import type { CanonicalHunkDiffLayout, HunkDiffLayout } from "./types";
+
+/** Normalize the deprecated public `stack` prop before it reaches renderer state. */
+export function normalizeHunkDiffLayout(
+  layout: HunkDiffLayout | CanonicalHunkDiffLayout,
+): CanonicalHunkDiffLayout {
+  return layout === "stack" ? "unified" : layout;
+}
diff --git a/packages/hunk/src/opentui/types.ts b/packages/hunk/src/opentui/types.ts
index 8bae652c1..3fa11e264 100644
--- a/packages/hunk/src/opentui/types.ts
+++ b/packages/hunk/src/opentui/types.ts
@@ -1,7 +1,12 @@
 import type { FileDiffMetadata } from "@pierre/diffs";
 import type { HunkDiffThemeName } from "./themes";
 
-export type HunkDiffLayout = "split" | "stack";
+/** @deprecated Use the canonical `unified` layout. */
+export type LegacyHunkDiffLayout = "stack";
+/** Pre-unified layout vocabulary retained so existing consumer source remains exhaustive. */
+export type HunkDiffLayout = "split" | LegacyHunkDiffLayout;
+/** Canonical layout vocabulary for new OpenTUI integrations. */
+export type CanonicalHunkDiffLayout = "split" | "unified";
 
 /** Line stats shown by public Hunk OpenTUI primitives. */
 export interface HunkDiffStats {
@@ -37,7 +42,10 @@ export interface HunkDiffSelection {
 /** Public props shared by single-file diff body and view components. */
 export interface HunkDiffBodyProps {
   file?: HunkDiffFileInput;
+  /** Legacy layout vocabulary retained for source compatibility. */
   layout?: HunkDiffLayout;
+  /** Canonical layout vocabulary. Takes precedence over `layout` when both are supplied. */
+  canonicalLayout?: CanonicalHunkDiffLayout;
   width: number;
   theme?: HunkDiffThemeName;
   showLineNumbers?: boolean;
@@ -65,7 +73,10 @@ export interface HunkDiffFileHeaderProps {
 
 export interface HunkReviewStreamProps {
   files: HunkDiffFileInput[];
+  /** Legacy layout vocabulary retained for source compatibility. */
   layout?: HunkDiffLayout;
+  /** Canonical layout vocabulary. Takes precedence over `layout` when both are supplied. */
+  canonicalLayout?: CanonicalHunkDiffLayout;
   width: number;
   theme?: HunkDiffThemeName;
   selection?: HunkDiffSelection;
diff --git a/packages/hunk/src/session/protocol.ts b/packages/hunk/src/session/protocol.ts
index e5e1c10a0..b64d4912f 100644
--- a/packages/hunk/src/session/protocol.ts
+++ b/packages/hunk/src/session/protocol.ts
@@ -36,7 +36,7 @@ export const HUNK_SESSION_API_VERSION = 1;
  * builds can refresh an older daemon even when it still exposes the same API endpoints. Bump this
  * when daemon-forwarded payloads change, even if the supported action names stay stable.
  */
-export const HUNK_SESSION_DAEMON_VERSION = 14;
+export const HUNK_SESSION_DAEMON_VERSION = 15;
 
 export type SessionDaemonAction =
   | "list"
diff --git a/packages/hunk/src/session/protocolSchemas.test.ts b/packages/hunk/src/session/protocolSchemas.test.ts
index 55140b6c8..df52ce420 100644
--- a/packages/hunk/src/session/protocolSchemas.test.ts
+++ b/packages/hunk/src/session/protocolSchemas.test.ts
@@ -79,8 +79,8 @@ const _mixedBatchItemIsNotACommand: SessionCommentApplyItemInput = {
 void _mixedBatchItemIsNotACommand;
 
 describe("session daemon request validation", () => {
-  test("uses the daemon revision for structured two-endpoint reload payloads", () => {
-    expect(HUNK_SESSION_DAEMON_VERSION).toBe(14);
+  test("uses the daemon revision for structured reloads with canonical layout payloads", () => {
+    expect(HUNK_SESSION_DAEMON_VERSION).toBe(15);
   });
 
   test("strictly parses cross-process capabilities", () => {
@@ -113,6 +113,23 @@ describe("session daemon request validation", () => {
       expect(parseSessionDaemonCapabilities(value)).toBeNull();
     }
   });
+
+  test("normalizes deprecated stack layout values in reload payloads", () => {
+    expect(
+      parseSessionDaemonRequest({
+        action: "reload",
+        selector: { sessionId: "s-1" },
+        nextInput: {
+          kind: "show",
+          ref: "HEAD",
+          options: { mode: "stack" },
+        },
+      }),
+    ).toMatchObject({
+      nextInput: { options: { mode: "unified" } },
+    });
+  });
+
   test("accepts every wire-shaped action payload", () => {
     const requests: unknown[] = [
       { action: "list" },
diff --git a/packages/hunk/src/session/protocolSchemas.ts b/packages/hunk/src/session/protocolSchemas.ts
index 84820218b..f2d7d0870 100644
--- a/packages/hunk/src/session/protocolSchemas.ts
+++ b/packages/hunk/src/session/protocolSchemas.ts
@@ -1,5 +1,5 @@
 import { z } from "zod";
-import type { CliInput } from "../core/run/commandInputs";
+import { normalizeLayoutModeInput, type CliInput } from "../core/run/commandInputs";
 import { EXPERIMENTAL_FEATURES } from "../core/run/experimental";
 import { parseExtensionReviewDescriptor } from "../core/reviewDescriptor";
 import type { ExtensionReviewDescriptor } from "../extension-api/types";
@@ -57,8 +57,13 @@ const rangeEndpointsSchema = z.strictObject({
   to: z.string().min(1),
 });
 
+/** Accept legacy layout vocabulary on the wire while returning canonical CLI state. */
+const layoutModeInputSchema = z
+  .enum(["auto", "split", "unified", "stack"])
+  .transform(normalizeLayoutModeInput);
+
 const commonOptionsSchema = z.strictObject({
-  mode: z.enum(["auto", "split", "stack"]).optional(),
+  mode: layoutModeInputSchema.optional(),
   cursorLine: z.enum(["row", "number", "off"]).optional(),
   vcs: z.string().optional(),
   theme: z.string().optional(),
diff --git a/packages/hunk/src/ui/App.extension-command-controls.test.tsx b/packages/hunk/src/ui/App.extension-command-controls.test.tsx
index f8ffbbf73..c6c6e69d1 100644
--- a/packages/hunk/src/ui/App.extension-command-controls.test.tsx
+++ b/packages/hunk/src/ui/App.extension-command-controls.test.tsx
@@ -14,7 +14,7 @@ function createBootstrap(extensions = createEmptyExtensionLoadResult("/repo")):
     ...createTestVcsAppBootstrap({
       changesetId: "changeset:command-controls",
       files: [createTestDiffFile({ id: "alpha", path: "alpha.ts" })],
-      initialMode: "stack",
+      initialMode: "unified",
     }),
     extensions,
   };
diff --git a/packages/hunk/src/ui/App.extension-runtime.test.tsx b/packages/hunk/src/ui/App.extension-runtime.test.tsx
index 97156fc10..930c457d1 100644
--- a/packages/hunk/src/ui/App.extension-runtime.test.tsx
+++ b/packages/hunk/src/ui/App.extension-runtime.test.tsx
@@ -13,7 +13,7 @@ function createBootstrap(id: string, extensions: ExtensionLoadResult): AppBootst
     ...createTestVcsAppBootstrap({
       changesetId: id,
       files: [createTestDiffFile({ id: "alpha", path: "alpha.ts" })],
-      initialMode: "stack",
+      initialMode: "unified",
     }),
     extensions,
   };
diff --git a/packages/hunk/src/ui/App.extension-trust.test.tsx b/packages/hunk/src/ui/App.extension-trust.test.tsx
index 885869fbc..5808bc904 100644
--- a/packages/hunk/src/ui/App.extension-trust.test.tsx
+++ b/packages/hunk/src/ui/App.extension-trust.test.tsx
@@ -13,7 +13,7 @@ function createBootstrap(pendingTrustRepoRoot?: string): AppBootstrap {
   const bootstrap = createTestVcsAppBootstrap({
     changesetId: "changeset:trust",
     files: [createTestDiffFile({ id: "alpha", path: "alpha.ts" })],
-    initialMode: "stack",
+    initialMode: "unified",
   });
   const extensions = createEmptyExtensionLoadResult("/repo");
 
diff --git a/packages/hunk/src/ui/AppHost.cursor-line.test.tsx b/packages/hunk/src/ui/AppHost.cursor-line.test.tsx
index 94361e86a..6b1fed35b 100644
--- a/packages/hunk/src/ui/AppHost.cursor-line.test.tsx
+++ b/packages/hunk/src/ui/AppHost.cursor-line.test.tsx
@@ -31,7 +31,7 @@ async function flush(setup: Awaited<ReturnType<typeof testRender>>) {
 
 function createCursorLineBootstrap(
   cursorLine: CursorLine,
-  initialMode: "split" | "stack" = "stack",
+  initialMode: "split" | "unified" = "unified",
 ) {
   return {
     ...createTestVcsAppBootstrap({
@@ -91,7 +91,7 @@ function gutterBackground(setup: Awaited<ReturnType<typeof testRender>>, needle:
 
 async function renderCursorLineApp(
   cursorLine: CursorLine,
-  initialMode: "split" | "stack" = "stack",
+  initialMode: "split" | "unified" = "unified",
 ) {
   const setup = await testRender(
     <AppHost bootstrap={createCursorLineBootstrap(cursorLine, initialMode) as never} />,
diff --git a/packages/hunk/src/ui/AppHost.edit-in-editor.test.tsx b/packages/hunk/src/ui/AppHost.edit-in-editor.test.tsx
index 566590de7..53fd5d6a4 100644
--- a/packages/hunk/src/ui/AppHost.edit-in-editor.test.tsx
+++ b/packages/hunk/src/ui/AppHost.edit-in-editor.test.tsx
@@ -49,7 +49,7 @@ function mockSpawnSync(implementation: typeof Bun.spawnSync) {
 function createEditorBootstrap(sourceLabel: string): AppBootstrap {
   return createTestVcsAppBootstrap({
     changesetId: "changeset:edit-in-editor",
-    initialMode: "stack",
+    initialMode: "unified",
     sourceLabel,
     files: [
       createTestDiffFile({
diff --git a/packages/hunk/src/ui/AppHost.extension-dialogs.test.tsx b/packages/hunk/src/ui/AppHost.extension-dialogs.test.tsx
index 1bb32d4a1..d03ee4774 100644
--- a/packages/hunk/src/ui/AppHost.extension-dialogs.test.tsx
+++ b/packages/hunk/src/ui/AppHost.extension-dialogs.test.tsx
@@ -101,7 +101,7 @@ async function flushUntil(
 /** Launch a bootstrap whose extensions come from one `--extension` fixture path. */
 async function launchWithExtension(repo: string, extPath: string): Promise<AppBootstrap> {
   const bootstrap = await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+    { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
     { cwd: repo },
   );
   bootstrap.extensions = await loadStartupExtensions({
diff --git a/packages/hunk/src/ui/AppHost.extension-navigation.test.tsx b/packages/hunk/src/ui/AppHost.extension-navigation.test.tsx
index 5482e4599..e488a1827 100644
--- a/packages/hunk/src/ui/AppHost.extension-navigation.test.tsx
+++ b/packages/hunk/src/ui/AppHost.extension-navigation.test.tsx
@@ -100,7 +100,7 @@ async function flushUntil(
 /** Launch a bootstrap whose extensions come from one `--extension` fixture path. */
 async function launchWithExtension(repo: string, extPath: string): Promise<AppBootstrap> {
   const bootstrap = await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+    { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
     { cwd: repo },
   );
   bootstrap.extensions = await loadStartupExtensions({
diff --git a/packages/hunk/src/ui/AppHost.extension-sidebar.test.tsx b/packages/hunk/src/ui/AppHost.extension-sidebar.test.tsx
index 477ca8815..281ae21e4 100644
--- a/packages/hunk/src/ui/AppHost.extension-sidebar.test.tsx
+++ b/packages/hunk/src/ui/AppHost.extension-sidebar.test.tsx
@@ -116,7 +116,7 @@ async function flushUntil(
 /** Launch a bootstrap whose extensions come from one `--extension` fixture path. */
 async function launchWithExtension(repo: string, extPath: string): Promise<AppBootstrap> {
   const bootstrap = await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+    { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
     { cwd: repo },
   );
   bootstrap.extensions = await loadStartupExtensions({
diff --git a/packages/hunk/src/ui/AppHost.extensions.test.tsx b/packages/hunk/src/ui/AppHost.extensions.test.tsx
index c1dd465d8..6b651afca 100644
--- a/packages/hunk/src/ui/AppHost.extensions.test.tsx
+++ b/packages/hunk/src/ui/AppHost.extensions.test.tsx
@@ -380,7 +380,7 @@ async function withAppHost(
  */
 async function launchInSubdirectory(repo: string, options: Record<string, unknown>) {
   return await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack", ...options } },
+    { kind: "vcs", staged: false, options: { mode: "unified", ...options } },
     { cwd: join(repo, "sub") },
   );
 }
@@ -876,7 +876,7 @@ describe("mounted lifecycle ordering", () => {
       {
         kind: "patch",
         text: "diff --git a/a.txt b/a.txt\n--- a/a.txt\n+++ b/a.txt\n@@ -1 +1 @@\n-before\n+after\n",
-        options: { mode: "stack", extensionPaths: [extPath] },
+        options: { mode: "unified", extensionPaths: [extPath] },
       },
       { cwd: root },
     );
@@ -902,7 +902,7 @@ describe("mounted lifecycle ordering", () => {
     useTempConfigHome();
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+      { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
       { cwd: repo },
     );
     bootstrap.extensions = await loadStartupExtensions({
@@ -946,7 +946,7 @@ describe("mounted lifecycle ordering", () => {
     useTempConfigHome();
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+      { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
       { cwd: repo },
     );
     bootstrap.extensions = await loadStartupExtensions({
@@ -1028,7 +1028,7 @@ describe("mounted lifecycle ordering", () => {
     useTempConfigHome();
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+      { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
       { cwd: repo },
     );
     bootstrap.extensions = await loadStartupExtensions({
@@ -1084,7 +1084,7 @@ describe("mounted lifecycle ordering", () => {
     useTempConfigHome();
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+      { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
       { cwd: repo },
     );
     bootstrap.extensions = await loadStartupExtensions({
@@ -1132,7 +1132,7 @@ export default function (hunk) {
     useTempConfigHome();
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", extensionPaths: [extPath] } },
+      { kind: "vcs", staged: false, options: { mode: "unified", extensionPaths: [extPath] } },
       { cwd: repo },
     );
     bootstrap.extensions = await loadStartupExtensions({
@@ -1180,7 +1180,7 @@ async function grantTrustAndCollectProbeEvents(repo: string) {
   useTempConfigHome();
 
   const bootstrap = await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack" } },
+    { kind: "vcs", staged: false, options: { mode: "unified" } },
     { cwd: repo },
   );
   bootstrap.extensions = await loadStartupExtensions({
@@ -1491,7 +1491,7 @@ describe("reload re-runs extension VCS detection", () => {
         kind: "vcs",
         staged: false,
         options: {
-          mode: "stack",
+          mode: "unified",
           extensionPaths: [extPath],
           vcs: resolveDetectedVcsIdWithExtensions(repo, vcsCatalog),
         },
@@ -1552,7 +1552,7 @@ describe("reload re-runs extension VCS detection", () => {
         kind: "vcs",
         staged: false,
         options: {
-          mode: "stack",
+          mode: "unified",
           extensionPaths: [extPath],
           vcs: resolveDetectedVcsIdWithExtensions(inner, vcsCatalog),
         },
diff --git a/packages/hunk/src/ui/AppHost.file-view-modes.test.tsx b/packages/hunk/src/ui/AppHost.file-view-modes.test.tsx
index 6db9bdfb1..3da1ac7f1 100644
--- a/packages/hunk/src/ui/AppHost.file-view-modes.test.tsx
+++ b/packages/hunk/src/ui/AppHost.file-view-modes.test.tsx
@@ -252,8 +252,8 @@ async function renderWithExtension(
   const bootstrap = createTestVcsAppBootstrap({
     changesetId: "changeset:file-view-mode",
     files,
-    initialMode: "stack",
-    inputMode: "stack",
+    initialMode: "unified",
+    inputMode: "unified",
     vcsOptions: { extensionPaths: [extension] },
   });
   bootstrap.extensions = extensions;
@@ -325,7 +325,7 @@ async function renderWatchedWithExtension({
     kind: "diff",
     left,
     right,
-    options: { mode: "stack", watch: true },
+    options: { mode: "unified", watch: true },
   });
   const extensions = await loadStartupExtensions({
     cliExtensionPaths: [extension],
diff --git a/packages/hunk/src/ui/AppHost.file-views.test.tsx b/packages/hunk/src/ui/AppHost.file-views.test.tsx
index 9696492c6..5458b7829 100644
--- a/packages/hunk/src/ui/AppHost.file-views.test.tsx
+++ b/packages/hunk/src/ui/AppHost.file-views.test.tsx
@@ -249,8 +249,8 @@ describe("AppHost file views", () => {
     const bootstrap = createTestVcsAppBootstrap({
       changesetId: "changeset:broken-row",
       files: [createTwoHunkFile()],
-      initialMode: "stack",
-      inputMode: "stack",
+      initialMode: "unified",
+      inputMode: "unified",
       vcsOptions: { extensionPaths: [extension] },
     });
     bootstrap.extensions = extensions;
@@ -292,8 +292,8 @@ describe("AppHost file views", () => {
     const bootstrap = createTestVcsAppBootstrap({
       changesetId: "changeset:stateful-view",
       files: [createTestDiffFile({ id: "stateful", path: "stateful.ts" })],
-      initialMode: "stack",
-      inputMode: "stack",
+      initialMode: "unified",
+      inputMode: "unified",
       vcsOptions: { extensionPaths: [extension] },
     });
     bootstrap.extensions = extensions;
@@ -410,8 +410,8 @@ describe("AppHost file views", () => {
     const bootstrap = createTestVcsAppBootstrap({
       changesetId: "changeset:bulk-view",
       files,
-      initialMode: "stack",
-      inputMode: "stack",
+      initialMode: "unified",
+      inputMode: "unified",
       vcsOptions: { extensionPaths: [extension] },
     });
     bootstrap.extensions = extensions;
@@ -477,8 +477,8 @@ describe("AppHost file views", () => {
     const bootstrap = createTestVcsAppBootstrap({
       changesetId: "changeset:jsx-runtime-proof",
       files: [createTwoHunkFile()],
-      initialMode: "stack",
-      inputMode: "stack",
+      initialMode: "unified",
+      inputMode: "unified",
       vcsOptions: { extensionPaths: [extension] },
     });
     bootstrap.extensions = extensions;
@@ -555,8 +555,8 @@ describe("AppHost file views", () => {
     const bootstrap = createTestVcsAppBootstrap({
       changesetId: "changeset:jsx-runtime-proof",
       files: [createTwoHunkFile()],
-      initialMode: "stack",
-      inputMode: "stack",
+      initialMode: "unified",
+      inputMode: "unified",
       vcsOptions: { extensionPaths: [extension] },
     });
     bootstrap.extensions = extensions;
diff --git a/packages/hunk/src/ui/AppHost.interactions.test.tsx b/packages/hunk/src/ui/AppHost.interactions.test.tsx
index b00106ed5..183a48d8e 100644
--- a/packages/hunk/src/ui/AppHost.interactions.test.tsx
+++ b/packages/hunk/src/ui/AppHost.interactions.test.tsx
@@ -374,8 +374,8 @@ function createRapidViewportLoopBootstrap(): AppBootstrap {
   return createTestVcsAppBootstrap({
     changesetId: "changeset:rapid-viewport",
     files,
-    vcsOptions: { mode: "stack", agentNotes: true },
-    initialMode: "stack",
+    vcsOptions: { mode: "unified", agentNotes: true },
+    initialMode: "unified",
     initialShowAgentNotes: true,
   });
 }
@@ -630,7 +630,7 @@ describe("App interactions", () => {
           },
         },
       ],
-      initialMode: "stack",
+      initialMode: "unified",
     });
 
     const setup = await testRender(<AppHost bootstrap={bootstrap} />, { width: 240, height: 24 });
@@ -676,7 +676,7 @@ describe("App interactions", () => {
       await flush(setup);
 
       // Regression coverage for issue #233 / PR #242. This intentionally combines the inputs
-      // that made the old React/OpenTUI feedback loop reproducible: stack layout, many hunks,
+      // that made the old React/OpenTUI feedback loop reproducible: unified layout, many hunks,
       // visible agent notes, repeated next-hunk jumps, and bursty wheel scrolling.
       for (let batch = 0; batch < 2; batch += 1) {
         await act(async () => {
@@ -2291,7 +2291,7 @@ describe("App interactions", () => {
     }
   });
 
-  test("layout toggles preserve the current viewport anchor across split and stack", async () => {
+  test("layout toggles preserve the current viewport anchor across split and unified", async () => {
     const setup = await testRender(<AppHost bootstrap={createLineScrollBootstrap()} />, {
       width: 220,
       height: 12,
@@ -2977,7 +2977,7 @@ describe("App interactions", () => {
 
   test("coalesced line movement opens a draft at the latest cursor without moving its row", async () => {
     const setup = await testRender(
-      <AppHost bootstrap={createLineScrollBootstrap(false, "stack")} />,
+      <AppHost bootstrap={createLineScrollBootstrap(false, "unified")} />,
       { width: 120, height: 26 },
     );
 
diff --git a/packages/hunk/src/ui/AppHost.keybindings.test.tsx b/packages/hunk/src/ui/AppHost.keybindings.test.tsx
index ba5d76c22..878d37fd5 100644
--- a/packages/hunk/src/ui/AppHost.keybindings.test.tsx
+++ b/packages/hunk/src/ui/AppHost.keybindings.test.tsx
@@ -77,7 +77,7 @@ async function launchWithConfig(repo: string, configToml: string): Promise<AppBo
   const input = {
     kind: "vcs" as const,
     staged: false,
-    options: { mode: "stack" as const, promptSaveViewPreferences: false },
+    options: { mode: "unified" as const, promptSaveViewPreferences: false },
   };
   const vcsCatalog = getBundledVcsCatalog();
   const configured = resolveConfiguredCliInput(input, { cwd: repo, vcsCatalog });
@@ -270,6 +270,33 @@ describe("user keybindings", () => {
     });
   });
 
+  test("preserves the deprecated layout command event id beside its canonical replacement", async () => {
+    const repo = createTestRepo("hunk-keybindings-layout-command-event-");
+    const bootstrap = await launchWithConfig(repo, "");
+    const extensions = createEmptyExtensionLoadResult(repo);
+    const seen: Array<{ commandId: string; canonicalCommandId?: string }> = [];
+    extensions.registry.eventHandlers.command_executed.push({
+      extensionId: "coach",
+      handler: (payload) => {
+        seen.push(payload);
+      },
+    });
+    bootstrap.extensions = extensions;
+
+    await withAppHost(bootstrap, async (setup) => {
+      await act(async () => {
+        await setup.mockInput.typeText("2");
+      });
+      await flush(setup);
+      expect(seen).toEqual([
+        {
+          commandId: "hunk.view.layoutStack",
+          canonicalCommandId: "hunk.view.layoutUnified",
+        },
+      ]);
+    });
+  });
+
   test("observes commands invoked through extension command controls exactly once", async () => {
     const repo = createTestRepo("hunk-keybindings-programmatic-command-event-");
     const bootstrap = await launchWithConfig(repo, "");
diff --git a/packages/hunk/src/ui/AppHost.keyboard-modes.test.tsx b/packages/hunk/src/ui/AppHost.keyboard-modes.test.tsx
index afac9ef37..da05d21cb 100644
--- a/packages/hunk/src/ui/AppHost.keyboard-modes.test.tsx
+++ b/packages/hunk/src/ui/AppHost.keyboard-modes.test.tsx
@@ -99,8 +99,8 @@ async function renderWithExtension() {
   const bootstrap = createTestVcsAppBootstrap({
     changesetId: "keyboard-mode",
     files: [createTestDiffFile({ id: "alpha", path: "alpha.ts" })],
-    initialMode: "stack",
-    inputMode: "stack",
+    initialMode: "unified",
+    inputMode: "unified",
   });
   bootstrap.extensions = extensions;
   const setup = await testRender(<AppHost bootstrap={bootstrap} onQuit={() => {}} />, {
diff --git a/packages/hunk/src/ui/AppHost.reload.test.tsx b/packages/hunk/src/ui/AppHost.reload.test.tsx
index 4e073867e..d06d8c490 100644
--- a/packages/hunk/src/ui/AppHost.reload.test.tsx
+++ b/packages/hunk/src/ui/AppHost.reload.test.tsx
@@ -120,7 +120,7 @@ describe("reload watch runtime compatibility", () => {
     writeFileSync(file, "original line\nfirst change\n");
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", excludeUntracked: true } },
+      { kind: "vcs", staged: false, options: { mode: "unified", excludeUntracked: true } },
       { cwd: dir, vcsCatalog: getBundledVcsCatalog() },
     );
     const { dispatchCommand, hostClient } = createTestHostClient();
@@ -142,7 +142,7 @@ describe("reload watch runtime compatibility", () => {
             nextInput: {
               kind: "vcs",
               staged: false,
-              options: { mode: "stack", excludeUntracked: true, watch: true },
+              options: { mode: "unified", excludeUntracked: true, watch: true },
             },
           },
         }),
@@ -172,7 +172,7 @@ describe("reload stale highlight cache", () => {
       kind: "diff",
       left,
       right,
-      options: { mode: "stack" },
+      options: { mode: "unified" },
     });
 
     const setup = await testRender(<AppHost bootstrap={bootstrap} />, {
@@ -227,7 +227,7 @@ describe("reload stale highlight cache", () => {
     writeFileSync(file, "original line\nfirst change\n");
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", excludeUntracked: true } },
+      { kind: "vcs", staged: false, options: { mode: "unified", excludeUntracked: true } },
       { cwd: dir, vcsCatalog: getBundledVcsCatalog() },
     );
 
@@ -282,7 +282,7 @@ describe("reload agent attention marks", () => {
       kind: "diff",
       left,
       right,
-      options: { mode: "stack" },
+      options: { mode: "unified" },
     });
     const { dispatchCommand, hostClient } = createTestHostClient();
     const setup = await testRender(<AppHost bootstrap={bootstrap} hostClient={hostClient} />, {
@@ -373,7 +373,7 @@ describe("reload agent attention marks", () => {
     writeFileSync(bravo, "export const bravo = 2;\n");
 
     const bootstrap = await loadAppBootstrap(
-      { kind: "vcs", staged: false, options: { mode: "stack", excludeUntracked: true } },
+      { kind: "vcs", staged: false, options: { mode: "unified", excludeUntracked: true } },
       { cwd: dir, vcsCatalog: getBundledVcsCatalog() },
     );
     const { dispatchCommand, hostClient } = createTestHostClient();
diff --git a/packages/hunk/src/ui/AppHost.responsive.test.tsx b/packages/hunk/src/ui/AppHost.responsive.test.tsx
index 29311f0f2..f0bfc7ccf 100644
--- a/packages/hunk/src/ui/AppHost.responsive.test.tsx
+++ b/packages/hunk/src/ui/AppHost.responsive.test.tsx
@@ -206,17 +206,17 @@ describe("responsive app", () => {
     }
   });
 
-  test("explicit split and stack modes override responsive auto switching", async () => {
+  test("explicit split and unified modes override responsive auto switching", async () => {
     const forcedSplit = await captureFrameForBootstrap(createBootstrap("split"), 140);
-    const forcedStack = await captureFrameForBootstrap(createBootstrap("stack"), 240);
+    const forcedUnified = await captureFrameForBootstrap(createBootstrap("unified"), 240);
 
     expect(forcedSplit).not.toContain("Files");
     expect(forcedSplit).not.toContain("Changeset summary");
     expect(forcedSplit).toMatch(/▌.*▌/);
 
-    expect((forcedStack.match(/alpha\.ts/g) ?? []).length).toBe(2);
-    expect(forcedStack).not.toContain("Changeset summary");
-    expect(forcedStack).not.toMatch(/▌.*▌/);
+    expect((forcedUnified.match(/alpha\.ts/g) ?? []).length).toBe(2);
+    expect(forcedUnified).not.toContain("Changeset summary");
+    expect(forcedUnified).not.toMatch(/▌.*▌/);
   });
 
   test("pager mode stays responsive while hiding app chrome", async () => {
diff --git a/packages/hunk/src/ui/AppHost.review-metadata.test.tsx b/packages/hunk/src/ui/AppHost.review-metadata.test.tsx
index 35b4e1a0e..428cb51b2 100644
--- a/packages/hunk/src/ui/AppHost.review-metadata.test.tsx
+++ b/packages/hunk/src/ui/AppHost.review-metadata.test.tsx
@@ -75,7 +75,7 @@ async function createTestBootstrap({ watch = false }: { watch?: boolean } = {})
   writeTestPatch(firstPatch, "first");
   writeTestPatch(secondPatch, "second");
   const bootstrap = await loadAppBootstrap(
-    { kind: "patch", file: firstPatch, options: { mode: "stack", watch } },
+    { kind: "patch", file: firstPatch, options: { mode: "unified", watch } },
     { cwd: directory },
   );
   bootstrap.review = Object.freeze({
@@ -129,7 +129,7 @@ async function createHistoryCommitBootstrap() {
   const nested = join(directory, "nested");
   mkdirSync(nested);
   const bootstrap = await loadAppBootstrap(
-    { kind: "show", ref: "HEAD", options: { mode: "stack", vcs: "git" } },
+    { kind: "show", ref: "HEAD", options: { mode: "unified", vcs: "git" } },
     { cwd: nested, vcsCatalog: getBundledVcsCatalog() },
   );
   bootstrap.review = Object.freeze({
@@ -231,7 +231,7 @@ describe("review metadata reloads", () => {
             nextInput: {
               kind: "patch",
               file: fixture.secondPatch,
-              options: { mode: "stack" },
+              options: { mode: "unified" },
             },
           },
         });
@@ -251,7 +251,7 @@ describe("review metadata reloads", () => {
             nextInput: {
               kind: "patch",
               file: fixture.firstPatch,
-              options: { mode: "stack" },
+              options: { mode: "unified" },
             },
           },
         });
diff --git a/packages/hunk/src/ui/AppHost.selection.test.tsx b/packages/hunk/src/ui/AppHost.selection.test.tsx
index 8c82b683a..d58e52b06 100644
--- a/packages/hunk/src/ui/AppHost.selection.test.tsx
+++ b/packages/hunk/src/ui/AppHost.selection.test.tsx
@@ -32,7 +32,7 @@ function createSelectionBootstrap(): AppBootstrap {
         context: 1,
       }),
     ],
-    initialMode: "stack",
+    initialMode: "unified",
     initialCopyDecorations: true,
   });
 }
@@ -56,7 +56,7 @@ function createWideCharSelectionBootstrap(): AppBootstrap {
         context: 1,
       }),
     ],
-    initialMode: "stack",
+    initialMode: "unified",
     initialCopyDecorations: true,
   });
 }
diff --git a/packages/hunk/src/ui/AppHost.watch.test.tsx b/packages/hunk/src/ui/AppHost.watch.test.tsx
index e1e2c6330..d8a38981c 100644
--- a/packages/hunk/src/ui/AppHost.watch.test.tsx
+++ b/packages/hunk/src/ui/AppHost.watch.test.tsx
@@ -129,7 +129,7 @@ describe("watched input lifecycle", () => {
       options: {
         agentContext: sidecar,
         agentNotes: true,
-        mode: "stack",
+        mode: "unified",
         watch: true,
       },
     });
@@ -179,7 +179,7 @@ describe("watched input lifecycle", () => {
       kind: "diff",
       left,
       right,
-      options: { mode: "stack", watch: true },
+      options: { mode: "unified", watch: true },
     });
     const watch = createWatchTestRuntime();
     const setup = await testRender(<AppHost bootstrap={bootstrap} watchRuntime={watch.runtime} />, {
diff --git a/packages/hunk/src/ui/AppHost.workspace.test.tsx b/packages/hunk/src/ui/AppHost.workspace.test.tsx
index 6773b3f7f..199f57a54 100644
--- a/packages/hunk/src/ui/AppHost.workspace.test.tsx
+++ b/packages/hunk/src/ui/AppHost.workspace.test.tsx
@@ -326,7 +326,7 @@ describe("extension workspace reads", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     let markReadStarted!: () => void;
     const readStarted = new Promise<void>((resolve) => {
@@ -379,7 +379,7 @@ describe("extension workspace reads", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -417,7 +417,7 @@ describe("extension workspace reads", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "show",
       ref: "HEAD",
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -455,7 +455,7 @@ describe("extension workspace reads", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -488,7 +488,7 @@ describe("extension workspace reads", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -533,7 +533,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -590,7 +590,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     const deferredWriter = createDeferredWorkspaceWriter();
     const broker = createTestBrokerClient();
@@ -645,7 +645,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     const deferredWriter = createDeferredWorkspaceWriter();
     const quitController = new AbortController();
@@ -696,7 +696,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -744,7 +744,7 @@ describe("extension workspace writes", () => {
       const bootstrap = await launchWithExtension(repo, extPath, {
         kind: "vcs",
         staged: false,
-        options: { mode: "stack", extensionPaths: [extPath] },
+        options: { mode: "unified", extensionPaths: [extPath] },
       });
       await withAppHost(bootstrap, async (setup) => {
         await flushUntil(
@@ -788,7 +788,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "vcs",
       staged: false,
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
@@ -832,7 +832,7 @@ describe("extension workspace writes", () => {
       const bootstrap = await launchWithExtension(repo, extPath, {
         kind: "vcs",
         staged: false,
-        options: { mode: "stack", extensionPaths: [extPath] },
+        options: { mode: "unified", extensionPaths: [extPath] },
       });
       await withAppHost(bootstrap, async (setup) => {
         await flushUntil(
@@ -873,7 +873,7 @@ describe("extension workspace writes", () => {
     const bootstrap = await launchWithExtension(repo, extPath, {
       kind: "show",
       ref: "HEAD",
-      options: { mode: "stack", extensionPaths: [extPath] },
+      options: { mode: "unified", extensionPaths: [extPath] },
     });
     await withAppHost(bootstrap, async (setup) => {
       await flushUntil(
diff --git a/packages/hunk/src/ui/components/panes/AgentInlineNote.test.tsx b/packages/hunk/src/ui/components/panes/AgentInlineNote.test.tsx
index 34f7a77f3..dc2975f77 100644
--- a/packages/hunk/src/ui/components/panes/AgentInlineNote.test.tsx
+++ b/packages/hunk/src/ui/components/panes/AgentInlineNote.test.tsx
@@ -31,7 +31,7 @@ test("AgentInlineNote connects a ranged card to the external annotation rail", a
     <AgentInlineNote
       annotation={{ source: "user", newRange: [2, 4], summary: "Connected range" }}
       anchorSide="new"
-      layout="stack"
+      layout="unified"
       rangeGuideConnection="terminate"
       theme={theme}
       width={60}
@@ -59,7 +59,7 @@ test("AgentInlineNote continues an aggregate rail through the card", async () =>
     <AgentInlineNote
       annotation={{ source: "user", newRange: [2, 4], summary: "Continuing range" }}
       anchorSide="new"
-      layout="stack"
+      layout="unified"
       rangeGuideConnection="continue"
       theme={theme}
       width={60}
@@ -221,7 +221,7 @@ function renderedCardRowCount(frame: string) {
   return bottom - top + 1;
 }
 
-function plannedCardHeight(body: string, width: number, layout: "split" | "stack" = "split") {
+function plannedCardHeight(body: string, width: number, layout: "split" | "unified" = "split") {
   return measureAgentInlineNoteHeight({
     annotation: draftAnnotation(body),
     anchorSide: "new",
@@ -301,7 +301,7 @@ describe("AgentInlineNote draft composer", () => {
       <AgentInlineNote
         annotation={draftAnnotation(body)}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={34}
         draft={{
@@ -320,7 +320,7 @@ describe("AgentInlineNote draft composer", () => {
       const frame = setup.captureCharFrame();
       expect(frame).toContain("HEAD-");
       expect(frame).toContain("TAIL");
-      expect(renderedCardRowCount(frame)).toBe(plannedCardHeight(body, 34, "stack"));
+      expect(renderedCardRowCount(frame)).toBe(plannedCardHeight(body, 34, "unified"));
     } finally {
       await act(async () => {
         setup.renderer.destroy();
diff --git a/packages/hunk/src/ui/components/panes/FileView.tsx b/packages/hunk/src/ui/components/panes/FileView.tsx
index 9592556a7..25b5fb1a8 100644
--- a/packages/hunk/src/ui/components/panes/FileView.tsx
+++ b/packages/hunk/src/ui/components/panes/FileView.tsx
@@ -170,7 +170,7 @@ function FileViewComponent({
                 annotation={plannedRow.annotation}
                 anchorSide={plannedRow.anchorSide}
                 file={file}
-                layout="stack"
+                layout="unified"
                 noteCount={plannedRow.noteCount}
                 noteIndex={plannedRow.noteIndex}
                 draft={plannedRow.note.draft}
diff --git a/packages/hunk/src/ui/components/panes/copySelection.test.ts b/packages/hunk/src/ui/components/panes/copySelection.test.ts
index 594d3fea0..0fa1c42a7 100644
--- a/packages/hunk/src/ui/components/panes/copySelection.test.ts
+++ b/packages/hunk/src/ui/components/panes/copySelection.test.ts
@@ -31,7 +31,7 @@ import {
 import {
   DIFF_RAIL_PREFIX_WIDTH,
   resolveSplitCellGeometry,
-  resolveStackCellGeometry,
+  resolveUnifiedCellGeometry,
   resolveSplitPaneWidths,
 } from "../../diff/codeColumns";
 import { measureTextWidth } from "../../lib/text";
@@ -114,7 +114,7 @@ describe("planSelectionActionBar", () => {
 
 describe("selectionInvalidationIdentity", () => {
   const base = {
-    layout: "stack" as const,
+    layout: "unified" as const,
     wrapLines: false,
     width: 80,
     viewportHeight: 20,
@@ -278,13 +278,13 @@ function createCjkDiffFile(): DiffFile {
 function buildMultiFileTestContext({
   copyDecorations = true,
   files,
-  layout = "stack",
+  layout = "unified",
   width = 120,
   wrapLines = false,
 }: {
   copyDecorations?: boolean;
   files: DiffFile[];
-  layout?: "stack" | "split";
+  layout?: "unified" | "split";
   width?: number;
   wrapLines?: boolean;
 }) {
@@ -316,7 +316,7 @@ function buildMultiFileTestContext({
   return { context, fileSectionLayouts, sectionGeometry };
 }
 
-/** Build a one-line change that sits on both split and stack add-note wrap boundaries. */
+/** Build a one-line change that sits on both split and unified add-note wrap boundaries. */
 function createWrappedBoundaryDiffFile(): DiffFile {
   const metadata = parseDiffFromFile(
     { name: "boundary.ts", contents: "", cacheKey: "boundary-before" },
@@ -337,7 +337,7 @@ function createWrappedBoundaryDiffFile(): DiffFile {
 }
 
 function buildContext(
-  layout: "stack" | "split" = "stack",
+  layout: "unified" | "split" = "unified",
   width = 120,
   file: DiffFile = createDiffFile(),
 ): {
@@ -349,7 +349,7 @@ function buildContext(
 }
 
 /** Build copy and measured geometry with the same wrapped add-note reservation policy. */
-function buildWrappedBoundaryContext(layout: "stack" | "split", reserveAddNoteColumn: boolean) {
+function buildWrappedBoundaryContext(layout: "unified" | "split", reserveAddNoteColumn: boolean) {
   const file = createWrappedBoundaryDiffFile();
   const theme = resolveTheme("github-dark-default", null);
   const width = layout === "split" ? 20 : 10;
@@ -460,9 +460,9 @@ describe("findLineCursorForClick", () => {
     ).toBe(contextCursor!);
   });
 
-  test("resolves a stacked row and ignores non-line rows", () => {
+  test("resolves a unified row and ignores non-line rows", () => {
     const file = createDiffFile();
-    const { fileSectionLayouts, sectionGeometry } = buildContext("stack", 120, file);
+    const { fileSectionLayouts, sectionGeometry } = buildContext("unified", 120, file);
     const cursors = buildLineCursors([file], sectionGeometry);
     const cursor = cursors.find(
       (candidate) => candidate.target.side === "new" && candidate.target.line === 1,
@@ -693,7 +693,7 @@ describe("projectCommentSelection", () => {
 
   test("projects contiguous code and rejects selected non-code rows", () => {
     const file = createDiffFile();
-    const { fileSectionLayouts, sectionGeometry } = buildContext("stack", 120, file);
+    const { fileSectionLayouts, sectionGeometry } = buildContext("unified", 120, file);
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
     const cursors = buildLineCursors([file], sectionGeometry);
@@ -803,7 +803,7 @@ describe("projectCommentSelection presentation crossings", () => {
       fileId: "synthetic",
       hunkIndex,
       row: {
-        type: "stack-line",
+        type: "unified-line",
         key,
         fileId: "synthetic",
         hunkIndex,
@@ -1183,14 +1183,14 @@ describe("renderCopySelectionText", () => {
   });
 
   test("code-only single-row selections preserve selected columns", () => {
-    const { context, fileSectionLayouts, sectionGeometry } = buildContext("stack");
+    const { context, fileSectionLayouts, sectionGeometry } = buildContext("unified");
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
     const rowIndex = geometry.plannedRows.findIndex(
-      (row) => row.kind === "diff-row" && row.row.type === "stack-line",
+      (row) => row.kind === "diff-row" && row.row.type === "unified-line",
     );
     const visualRow = section.bodyTop + geometry.rowBounds[rowIndex]!.top;
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -1227,7 +1227,7 @@ describe("renderCopySelectionText", () => {
   });
 
   test("does not include terminal controls from copied paths or code", () => {
-    const { context, fileSectionLayouts } = buildContext("stack", 160, createMaliciousDiffFile());
+    const { context, fileSectionLayouts } = buildContext("unified", 160, createMaliciousDiffFile());
     const start: CopySelectionPoint = {
       kind: "pinned-header",
       column: 0,
@@ -1265,13 +1265,13 @@ describe("renderCopySelectionText", () => {
     const rowIndex = geometry.plannedRows.findIndex(
       (row) =>
         row.kind === "diff-row" &&
-        row.row.type === "stack-line" &&
+        row.row.type === "unified-line" &&
         row.row.cell.kind === "addition",
     );
     const bounds = geometry.rowBounds[rowIndex]!;
     expect(bounds.height).toBeGreaterThan(2);
 
-    const { gutterWidth, contentWidth } = resolveStackCellGeometry(
+    const { gutterWidth, contentWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -1383,9 +1383,9 @@ describe("renderCopySelectionText", () => {
 });
 
 describe("resolveCopySelectionSide", () => {
-  test("returns undefined in stack layout", () => {
-    expect(resolveCopySelectionSide(10, "stack", 120)).toBeUndefined();
-    expect(resolveCopySelectionSide(80, "stack", 120)).toBeUndefined();
+  test("returns undefined in unified layout", () => {
+    expect(resolveCopySelectionSide(10, "unified", 120)).toBeUndefined();
+    expect(resolveCopySelectionSide(80, "unified", 120)).toBeUndefined();
   });
 
   test("returns 'left' for columns inside the split left pane", () => {
@@ -1665,11 +1665,11 @@ describe("buildCopySelectedRowKeys", () => {
 
 describe("expandSelectionPoint", () => {
   test("triple-click with code-only copy selects the code line", () => {
-    const { context, fileSectionLayouts, sectionGeometry } = buildContext("stack");
+    const { context, fileSectionLayouts, sectionGeometry } = buildContext("unified");
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
     const undecoratedContext: CopySelectionContext = { ...context, copyDecorations: false };
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -1691,8 +1691,8 @@ describe("expandSelectionPoint", () => {
     });
   });
 
-  test("triple-click in stack selects the full width", () => {
-    const { context, fileSectionLayouts } = buildContext("stack");
+  test("triple-click in unified selects the full width", () => {
+    const { context, fileSectionLayouts } = buildContext("unified");
     const section = fileSectionLayouts[0]!;
     const point: CopySelectionPoint = {
       kind: "review-row",
@@ -1750,14 +1750,14 @@ describe("expandSelectionPoint", () => {
   });
 
   test("double-click on whitespace selects the whitespace character itself", () => {
-    const { context, fileSectionLayouts, sectionGeometry } = buildContext("stack");
+    const { context, fileSectionLayouts, sectionGeometry } = buildContext("unified");
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
 
     // Compute the global column for the space character between "export" and "const".
     // The addition row "export const answer = 42;" starts at bodyTop + 2
     // (after a hunk header row and a deletion row).
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -1785,10 +1785,10 @@ describe("expandSelectionPoint", () => {
   });
 
   test("double-click on a word stops at code punctuation", () => {
-    const { context, fileSectionLayouts, sectionGeometry } = buildContext("stack");
+    const { context, fileSectionLayouts, sectionGeometry } = buildContext("unified");
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -1897,7 +1897,7 @@ describe("renderCopySelectionText in split with side", () => {
 });
 
 describe("wrapped add-note copy parity", () => {
-  for (const layout of ["split", "stack"] as const) {
+  for (const layout of ["split", "unified"] as const) {
     test(`${layout} continuation rows match measured, decorated, code-only, and word-selection boundaries`, () => {
       const unreserved = buildWrappedBoundaryContext(layout, false);
       const { context, geometry, section } = buildWrappedBoundaryContext(layout, true);
@@ -1905,7 +1905,7 @@ describe("wrapped add-note copy parity", () => {
         row.kind === "diff-row" &&
         (row.row.type === "split-line"
           ? row.row.right.kind === "addition"
-          : row.row.type === "stack-line" && row.row.cell.kind === "addition");
+          : row.row.type === "unified-line" && row.row.cell.kind === "addition");
       const rowIndex = geometry.plannedRows.findIndex(isAddedCodeRow);
       const unreservedRowIndex = unreserved.geometry.plannedRows.findIndex(isAddedCodeRow);
       expect(rowIndex).toBeGreaterThanOrEqual(0);
@@ -1975,13 +1975,13 @@ describe("copy selection with wide (CJK) characters", () => {
 
   function buildCjkContext() {
     const { context, fileSectionLayouts, sectionGeometry } = buildContext(
-      "stack",
+      "unified",
       120,
       createCjkDiffFile(),
     );
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
@@ -2125,7 +2125,7 @@ describe("copy selection with wide (CJK) characters", () => {
       metadata,
       agent: null,
     };
-    const { context, fileSectionLayouts } = buildContext("stack", 120, file);
+    const { context, fileSectionLayouts } = buildContext("unified", 120, file);
     const nextVisualRow = fileSectionLayouts[0]!.bodyTop;
 
     const headerCells = (startColumn: number, endColumn: number) =>
@@ -2168,10 +2168,10 @@ describe("copy selection with zero-width characters", () => {
       metadata,
       agent: null,
     };
-    const { context, fileSectionLayouts, sectionGeometry } = buildContext("stack", 120, file);
+    const { context, fileSectionLayouts, sectionGeometry } = buildContext("unified", 120, file);
     const section = fileSectionLayouts[0]!;
     const geometry = sectionGeometry[0]!;
-    const { gutterWidth } = resolveStackCellGeometry(
+    const { gutterWidth } = resolveUnifiedCellGeometry(
       context.width,
       geometry.lineNumberDigits,
       context.showLineNumbers,
diff --git a/packages/hunk/src/ui/components/panes/copySelection.ts b/packages/hunk/src/ui/components/panes/copySelection.ts
index 717fa5b3e..352e0afa9 100644
--- a/packages/hunk/src/ui/components/panes/copySelection.ts
+++ b/packages/hunk/src/ui/components/panes/copySelection.ts
@@ -38,7 +38,7 @@ export type CopySelectionPoint =
     };
 
 // In split layout the drag is anchored to one side of the diff (left = old / A, right = new / B)
-// based on the anchor column. In stack layout there is only one column, so side is undefined.
+// based on the anchor column. In unified layout there is only one column, so side is undefined.
 export type CopySelectionSide = "left" | "right";
 
 export interface CopySelectionDrag {
@@ -312,7 +312,7 @@ function resolveCopyVisualLineOffset({
     width,
     wrapLines: context.wrapLines,
   });
-  if (codeLayout?.kind === "stack") {
+  if (codeLayout?.kind === "unified") {
     return codeLayout.cell.prefixWidth + codeLayout.cell.gutterWidth;
   }
   if (codeLayout?.kind !== "split" || !copySide) {
@@ -658,7 +658,7 @@ export function expandSelectionPoint(
       const cell = side === "left" ? codeLayout.left : codeLayout.right;
       globalContentStart =
         (side === "left" ? 0 : codeLayout.leftPaneWidth) + cell.prefixWidth + cell.gutterWidth;
-    } else if (codeLayout?.kind === "stack") {
+    } else if (codeLayout?.kind === "unified") {
       globalContentStart = codeLayout.cell.prefixWidth + codeLayout.cell.gutterWidth;
     }
 
diff --git a/packages/hunk/src/ui/components/ui-components.test.tsx b/packages/hunk/src/ui/components/ui-components.test.tsx
index e5d0b9817..7a4491b0c 100644
--- a/packages/hunk/src/ui/components/ui-components.test.tsx
+++ b/packages/hunk/src/ui/components/ui-components.test.tsx
@@ -665,7 +665,7 @@ describe("UI components", () => {
     const setup = await testRender(
       <RawDiffRowView
         row={{
-          type: "stack-line",
+          type: "unified-line",
           key: "alpha:line:1",
           fileId: "alpha",
           hunkIndex: 0,
@@ -830,7 +830,7 @@ describe("UI components", () => {
   test("DiffRowView keeps wrapped text stable when showing the add-note affordance", async () => {
     const theme = resolveTheme("github-dark-default", null);
     const row = {
-      type: "stack-line" as const,
+      type: "unified-line" as const,
       key: "alpha:line:hover-wrap",
       fileId: "alpha",
       hunkIndex: 0,
@@ -877,7 +877,7 @@ describe("UI components", () => {
     const setup = await testRender(
       <RawDiffRowView
         row={{
-          type: "stack-line",
+          type: "unified-line",
           key: "alpha:line:hover-wrap-bg",
           fileId: "alpha",
           hunkIndex: 0,
@@ -966,7 +966,7 @@ describe("UI components", () => {
   test("DiffRowView preserves zero-width combining spans in nowrap and wrapped rows", async () => {
     const theme = resolveTheme("github-dark-default", null);
     const row = {
-      type: "stack-line" as const,
+      type: "unified-line" as const,
       key: "alpha:line:combining",
       fileId: "alpha",
       hunkIndex: 0,
@@ -1011,7 +1011,7 @@ describe("UI components", () => {
   test("DiffRowView height matches geometry for repeated composing scalars", async () => {
     const theme = resolveTheme("github-dark-default", null);
     const row = {
-      type: "stack-line" as const,
+      type: "unified-line" as const,
       key: "alpha:line:repeated-composition",
       fileId: "alpha",
       hunkIndex: 0,
@@ -1059,7 +1059,7 @@ describe("UI components", () => {
     }
   });
 
-  test("DiffRowView matches planned split and stack geometry at guide and add-note wrap boundaries", async () => {
+  test("DiffRowView matches planned split and unified geometry at guide and add-note wrap boundaries", async () => {
     const theme = resolveTheme("github-dark-default", null);
     const plannedRows = [
       {
@@ -1086,14 +1086,14 @@ describe("UI components", () => {
       },
       {
         kind: "diff-row" as const,
-        key: "alpha:stack:guide-boundary",
-        stableKey: "alpha:stack:guide-boundary",
+        key: "alpha:unified:guide-boundary",
+        stableKey: "alpha:unified:guide-boundary",
         fileId: "alpha",
         hunkIndex: 0,
         noteGuideSide: "new" as const,
         row: {
-          type: "stack-line" as const,
-          key: "alpha:stack:guide-boundary",
+          type: "unified-line" as const,
+          key: "alpha:unified:guide-boundary",
           fileId: "alpha",
           hunkIndex: 0,
           cell: {
@@ -1205,7 +1205,7 @@ describe("UI components", () => {
       { spans: [{ text: "日" }, { text: "áá" }], expectedHeight: 2 },
     ]) {
       const row = {
-        type: "stack-line" as const,
+        type: "unified-line" as const,
         key: "alpha:line:zero-before-wide",
         fileId: "alpha",
         hunkIndex: 0,
@@ -2850,7 +2850,7 @@ describe("UI components", () => {
     const measured = measureAgentInlineNoteHeight({
       annotation,
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 60,
       actions,
       threadDepth: thread.depth,
@@ -2859,7 +2859,7 @@ describe("UI components", () => {
       <AgentInlineNote
         annotation={annotation}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         actions={actions}
@@ -2956,7 +2956,7 @@ describe("UI components", () => {
     const measured = measureAgentInlineNoteHeight({
       annotation,
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 60,
       threadDepth: thread.depth,
     });
@@ -2964,7 +2964,7 @@ describe("UI components", () => {
       <AgentInlineNote
         annotation={annotation}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         thread={thread}
@@ -2995,7 +2995,7 @@ describe("UI components", () => {
     const measured = measureAgentInlineNoteHeight({
       annotation,
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 60,
     });
     const onSave = mock(() => {});
@@ -3004,7 +3004,7 @@ describe("UI components", () => {
       <AgentInlineNote
         annotation={annotation}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         draft={{
@@ -3063,14 +3063,14 @@ describe("UI components", () => {
     const measured = measureAgentInlineNoteHeight({
       annotation,
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 60,
     });
     const frame = await captureFrame(
       <AgentInlineNote
         annotation={annotation}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         onClose={() => {}}
@@ -3104,7 +3104,7 @@ describe("UI components", () => {
       <AgentInlineNote
         annotation={annotation}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         onClose={() => {}}
@@ -3184,7 +3184,7 @@ describe("UI components", () => {
         }}
         file={file}
         anchorSide="new"
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={48}
       />,
@@ -3218,7 +3218,7 @@ describe("UI components", () => {
         }}
         anchorSide="new"
         file={file}
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={60}
         thread={{ noteId: "note", depth: 0 }}
@@ -3618,7 +3618,7 @@ describe("UI components", () => {
         activeMenuId="view"
         activeMenuEntries={[
           { kind: "item", label: "Split view", hint: "1", checked: true, action: () => {} },
-          { kind: "item", label: "Stacked view", hint: "2", checked: false, action: () => {} },
+          { kind: "item", label: "Unified view", hint: "2", checked: false, action: () => {} },
           { kind: "item", label: "Line numbers", hint: "l", checked: true, action: () => {} },
           { kind: "item", label: "Line wrapping", hint: "w", checked: false, action: () => {} },
           { kind: "item", label: "Hunk metadata", hint: "m", checked: true, action: () => {} },
@@ -3636,7 +3636,7 @@ describe("UI components", () => {
     );
 
     expect(frame).toContain("[x] Split view");
-    expect(frame).toContain("[ ] Stacked view");
+    expect(frame).toContain("[ ] Unified view");
     expect(frame).toContain("[x] Line numbers");
     expect(frame).toContain("[ ] Line wrapping");
     expect(frame).toContain("[x] Hunk metadata");
@@ -3888,7 +3888,7 @@ describe("UI components", () => {
       "Wheel                    scroll vertically",
       "Shift+Wheel              scroll code horizontally",
       "View",
-      "1 / 2 / 0                split / stack / auto",
+      "1 / 2 / 0                split / unified / auto",
       "s / t                    sidebar / theme selector",
       "a                        toggle AI notes",
       "z                        toggle unchanged context",
@@ -4123,13 +4123,13 @@ describe("UI components", () => {
     expect(frame).toContain("1 + export const alpha = 2;");
   });
 
-  test("DiffSectionBody renders stack-mode wrapped continuation rows", async () => {
+  test("DiffSectionBody renders unified-mode wrapped continuation rows", async () => {
     const file = createWrapBootstrap().changeset.files[0]!;
     const theme = resolveTheme("github-dark-default", null);
     const frame = await captureFrame(
       <DiffSectionBody
         file={file}
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={48}
         selectedHunkIndex={0}
@@ -4161,7 +4161,7 @@ describe("UI components", () => {
     const baseFrame = await captureFrame(
       <DiffSectionBody
         file={file}
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={48}
         selectedHunkIndex={0}
@@ -4174,7 +4174,7 @@ describe("UI components", () => {
     const shiftedFrame = await captureFrame(
       <DiffSectionBody
         file={file}
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={48}
         selectedHunkIndex={0}
@@ -4192,7 +4192,7 @@ describe("UI components", () => {
     expect(shiftedFrame).not.toContain("this is a very");
   });
 
-  test("split view wraps the same long diff line across more rows than stack view at the same width", async () => {
+  test("split view wraps the same long diff line across more rows than unified view at the same width", async () => {
     const file = createWrapBootstrap().changeset.files[0]!;
     const theme = resolveTheme("github-dark-default", null);
     const width = 64;
@@ -4210,10 +4210,10 @@ describe("UI components", () => {
       width + 4,
       18,
     );
-    const stackFrame = await captureFrame(
+    const unifiedFrame = await captureFrame(
       <DiffSectionBody
         file={file}
-        layout="stack"
+        layout="unified"
         theme={theme}
         width={width}
         selectedHunkIndex={0}
@@ -4225,11 +4225,13 @@ describe("UI components", () => {
     );
 
     const splitContinuationRows = splitFrame.split("\n").filter((line) => /^▌\s+▌\s+\S/.test(line));
-    const stackContinuationRows = stackFrame.split("\n").filter((line) => /^▌\s{6,}\S/.test(line));
+    const unifiedContinuationRows = unifiedFrame
+      .split("\n")
+      .filter((line) => /^▌\s{6,}\S/.test(line));
 
     expect(splitFrame).toContain("1 + export const message = 't");
-    expect(stackFrame).toContain("1 +  export const message = 'this is a very long wrapped line");
-    expect(splitContinuationRows.length).toBeGreaterThan(stackContinuationRows.length);
+    expect(unifiedFrame).toContain("1 +  export const message = 'this is a very long wrapped line");
+    expect(splitContinuationRows.length).toBeGreaterThan(unifiedContinuationRows.length);
   });
 
   test("DiffSectionBody anchors range-less notes to the first visible row when hunk headers are hidden", async () => {
diff --git a/packages/hunk/src/ui/currentReviewRefresh.test.ts b/packages/hunk/src/ui/currentReviewRefresh.test.ts
index 3bb008312..9f3afb35d 100644
--- a/packages/hunk/src/ui/currentReviewRefresh.test.ts
+++ b/packages/hunk/src/ui/currentReviewRefresh.test.ts
@@ -22,7 +22,7 @@ describe("current review refresh descriptor", () => {
       kind: "diff",
       left: "before.ts",
       right: "after.ts",
-      options: { mode: "stack", theme: "dracula", watch: true, tabWidth: 8 },
+      options: { mode: "unified", theme: "dracula", watch: true, tabWidth: 8 },
     };
 
     expect(withCurrentReviewViewOptions(input, currentView)).toEqual({
@@ -38,7 +38,7 @@ describe("current review refresh descriptor", () => {
         wrapLines: true,
       },
     });
-    expect(input.options).toEqual({ mode: "stack", theme: "dracula", watch: true, tabWidth: 8 });
+    expect(input.options).toEqual({ mode: "unified", theme: "dracula", watch: true, tabWidth: 8 });
   });
 
   test("attaches the source path only to VCS inputs", () => {
diff --git a/packages/hunk/src/ui/diff/CodeCellView.test.tsx b/packages/hunk/src/ui/diff/CodeCellView.test.tsx
index 4814e3f1e..6e4f42c29 100644
--- a/packages/hunk/src/ui/diff/CodeCellView.test.tsx
+++ b/packages/hunk/src/ui/diff/CodeCellView.test.tsx
@@ -8,7 +8,7 @@ import {
   lineHighlightToneStyle,
   selectionHighlightBg,
   splitCellPalette,
-  stackCellPalette,
+  unifiedCellPalette,
 } from "./rowStyle";
 import { plannedDiffRowFromRaw, planCodeRowLayout } from "./codeRowLayout";
 import type { DiffRow } from "./diffRows";
@@ -53,9 +53,9 @@ function backgroundForText(
   return colorsForText(capture, text).bg;
 }
 
-const stackRow: Extract<DiffRow, { type: "stack-line" }> = {
-  type: "stack-line",
-  key: "paint:stack",
+const unifiedRow: Extract<DiffRow, { type: "unified-line" }> = {
+  type: "unified-line",
+  key: "paint:unified",
   fileId: "paint",
   hunkIndex: 0,
   cell: {
@@ -86,21 +86,21 @@ function codeRowView(row: DiffRow, options: Partial<Parameters<typeof RawDiffRow
 }
 
 describe("CodeCellView painting", () => {
-  test("keeps partial copy selections exact in nowrap and wrapped stack cells", async () => {
+  test("keeps partial copy selections exact in nowrap and wrapped unified cells", async () => {
     const theme = resolveTheme("github-dark-default", null);
 
     for (const wrapLines of [false, true]) {
-      const plannedRow = plannedDiffRowFromRaw(stackRow);
+      const plannedRow = plannedDiffRowFromRaw(unifiedRow);
       const layout = planCodeRowLayout(plannedRow, {
         width: 12,
         lineNumberDigits: 1,
         showLineNumbers: false,
         wrapLines,
       });
-      if (!layout || layout.kind !== "stack") throw new Error("Expected stack layout");
+      if (!layout || layout.kind !== "unified") throw new Error("Expected unified layout");
       const contentStart = layout.cell.prefixWidth + layout.cell.gutterWidth;
       const capture = await captureCodeRow(
-        codeRowView(stackRow, {
+        codeRowView(unifiedRow, {
           copySelectedRowRange: {
             startCol: contentStart + 1,
             endCol: contentStart + 2,
@@ -110,7 +110,7 @@ describe("CodeCellView painting", () => {
       );
 
       expect(backgroundForText(capture.spans, "bc")).toBe(
-        selectionHighlightBg(stackCellPalette("addition", theme).contentBg, theme).toLowerCase(),
+        selectionHighlightBg(unifiedCellPalette("addition", theme).contentBg, theme).toLowerCase(),
       );
       expect(capture.frame).toContain("abcd");
     }
@@ -128,7 +128,7 @@ describe("CodeCellView painting", () => {
     };
 
     for (const wrapLines of [false, true]) {
-      for (const row of [stackRow, splitRow]) {
+      for (const row of [unifiedRow, splitRow]) {
         const plannedRow = plannedDiffRowFromRaw(row);
         const width = row.type === "split-line" ? 24 : 12;
         const layout = planCodeRowLayout(plannedRow, {
@@ -139,7 +139,7 @@ describe("CodeCellView painting", () => {
         });
         if (!layout) throw new Error("Expected code row layout");
         const contentStart =
-          layout.kind === "stack"
+          layout.kind === "unified"
             ? layout.cell.prefixWidth + layout.cell.gutterWidth
             : layout.left.width + layout.right.prefixWidth + layout.right.gutterWidth;
         const capture = await captureCodeRow(
@@ -155,7 +155,7 @@ describe("CodeCellView painting", () => {
         const contentBg =
           row.type === "split-line"
             ? splitCellPalette("addition", theme).contentBg
-            : stackCellPalette("addition", theme).contentBg;
+            : unifiedCellPalette("addition", theme).contentBg;
         expect(backgroundForText(capture.spans, sourceText)).toBe(
           selectionHighlightBg(contentBg, theme).toLowerCase(),
         );
@@ -165,11 +165,11 @@ describe("CodeCellView painting", () => {
 
   test("keeps extension highlights geometry-neutral for wide and combining text", async () => {
     const theme = resolveTheme("github-dark-default", null);
-    const row: Extract<DiffRow, { type: "stack-line" }> = {
-      ...stackRow,
+    const row: Extract<DiffRow, { type: "unified-line" }> = {
+      ...unifiedRow,
       key: "paint:wide",
       cell: {
-        ...stackRow.cell,
+        ...unifiedRow.cell,
         spans: [{ text: "a\u0301日bc" }],
       },
     };
@@ -187,7 +187,7 @@ describe("CodeCellView painting", () => {
       expect(backgroundForText(marked.spans, "\u0301")).toBe(
         lineHighlightToneStyle(
           "match",
-          stackCellPalette("addition", theme).contentBg,
+          unifiedCellPalette("addition", theme).contentBg,
           theme,
         )!.bg.toLowerCase(),
       );
@@ -196,11 +196,11 @@ describe("CodeCellView painting", () => {
 
   test("resolves dim foregrounds against the final cursor background", async () => {
     const theme = resolveTheme("ayu-light", null);
-    const row: Extract<DiffRow, { type: "stack-line" }> = {
-      ...stackRow,
+    const row: Extract<DiffRow, { type: "unified-line" }> = {
+      ...unifiedRow,
       key: "paint:dim-cursor",
       cell: {
-        ...stackRow.cell,
+        ...unifiedRow.cell,
         spans: [{ text: "dimtext", fg: theme.syntaxColors.default }],
       },
     };
@@ -227,11 +227,11 @@ describe("CodeCellView painting", () => {
 
   test("resolves selected and unselected pieces of one dim span against their own backgrounds", async () => {
     const theme = resolveTheme("ayu-light", null);
-    const row: Extract<DiffRow, { type: "stack-line" }> = {
-      ...stackRow,
+    const row: Extract<DiffRow, { type: "unified-line" }> = {
+      ...unifiedRow,
       key: "paint:dim-copy-selection",
       cell: {
-        ...stackRow.cell,
+        ...unifiedRow.cell,
         spans: [{ text: "dimtext", fg: theme.syntaxColors.default }],
       },
     };
@@ -247,7 +247,7 @@ describe("CodeCellView painting", () => {
         showLineNumbers: false,
         wrapLines,
       });
-      if (!layout || layout.kind !== "stack") throw new Error("Expected stack layout");
+      if (!layout || layout.kind !== "unified") throw new Error("Expected unified layout");
       const contentStart = layout.cell.prefixWidth + layout.cell.gutterWidth;
       const capture = await captureCodeRow(
         codeRowView(row, {
@@ -274,7 +274,7 @@ describe("CodeCellView painting", () => {
     }
   });
 
-  test("paints transparent-theme cursors while retaining split and stack note guides", async () => {
+  test("paints transparent-theme cursors while retaining split and unified note guides", async () => {
     const theme = withTransparentSurfaces(resolveTheme("github-dark-default", null));
     const rows: DiffRow[] = [
       {
@@ -286,8 +286,8 @@ describe("CodeCellView painting", () => {
         right: { kind: "context", sign: " ", lineNumber: 1, spans: [{ text: "shared" }] },
       },
       {
-        type: "stack-line",
-        key: "paint:stack-context",
+        type: "unified-line",
+        key: "paint:unified-context",
         fileId: "paint",
         hunkIndex: 0,
         cell: {
@@ -314,7 +314,10 @@ describe("CodeCellView painting", () => {
 
         expect(capture.frame).toContain("│");
         expect(backgroundForText(capture.spans, "shared")).toBe(
-          cursorLineHighlightBg(stackCellPalette("context", theme).contentBg, theme).toLowerCase(),
+          cursorLineHighlightBg(
+            unifiedCellPalette("context", theme).contentBg,
+            theme,
+          ).toLowerCase(),
         );
       }
     }
diff --git a/packages/hunk/src/ui/diff/CodeCellView.tsx b/packages/hunk/src/ui/diff/CodeCellView.tsx
index e33271603..873d43ed7 100644
--- a/packages/hunk/src/ui/diff/CodeCellView.tsx
+++ b/packages/hunk/src/ui/diff/CodeCellView.tsx
@@ -1,12 +1,12 @@
 /**
- * Paints split and stack diff code cells through React and OpenTUI.
+ * Paints split and unified diff code cells through React and OpenTUI.
  * Canonical code-row and styled-span plans continue to own geometry and wrapping.
  */
 import { Fragment, isValidElement, memo, type ReactNode } from "react";
 import { parseColor, StyledText, type TextChunk } from "@opentui/core";
 import type { AppTheme } from "../themes";
 import type { CodeCellLayoutPlan, CodeRowLayoutPlan } from "./codeRowLayout";
-import type { DiffRow, RenderSpan, SplitLineCell, StackLineCell } from "./diffRows";
+import type { DiffRow, RenderSpan, SplitLineCell, UnifiedLineCell } from "./diffRows";
 import {
   applyLineHighlightsToSpans,
   lineHighlightPaintKey,
@@ -16,8 +16,8 @@ import {
   lineHighlightToneStyle,
   splitCellPalette,
   splitGutterText,
-  stackCellPalette,
-  stackGutterText,
+  unifiedCellPalette,
+  unifiedGutterText,
 } from "./rowStyle";
 import { sanitizeTerminalSpans } from "../../lib/terminalText";
 import { measureTextWidth, sliceTextByWidth } from "../lib/text";
@@ -229,10 +229,10 @@ function appendPlainSplitCellChunks(
   );
 }
 
-/** Append one unhighlighted stack cell without constructing React span fibers. */
-function appendPlainStackCellChunks(
+/** Append one unhighlighted unified cell without constructing React span fibers. */
+function appendPlainUnifiedCellChunks(
   chunks: TextChunk[],
-  cell: StackLineCell,
+  cell: UnifiedLineCell,
   geometry: CodeCellLayoutPlan,
   lineNumberDigits: number,
   showLineNumbers: boolean,
@@ -240,7 +240,7 @@ function appendPlainStackCellChunks(
   contentOffset: number,
   prefix: CellPrefix,
 ) {
-  const palette = stackCellPalette(cell.kind, theme, cell.moveKind);
+  const palette = unifiedCellPalette(cell.kind, theme, cell.moveKind);
   chunks.push(
     {
       __isChunk: true,
@@ -250,7 +250,7 @@ function appendPlainStackCellChunks(
     },
     {
       __isChunk: true,
-      text: stackGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(geometry.gutterWidth),
+      text: unifiedGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(geometry.gutterWidth),
       fg: styledTextColor(palette.numberColor),
       bg: styledTextColor(palette.gutterBg),
     },
@@ -524,7 +524,7 @@ interface WrappedCellLine {
 interface WrappedCellLayout {
   gutterWidth: number;
   contentWidth: number;
-  palette: ReturnType<typeof splitCellPalette> | ReturnType<typeof stackCellPalette>;
+  palette: ReturnType<typeof splitCellPalette> | ReturnType<typeof unifiedCellPalette>;
   lines: WrappedCellLine[];
 }
 
@@ -553,16 +553,16 @@ function buildWrappedSplitCell(
   } satisfies WrappedCellLayout;
 }
 
-/** Build wrapped stack-cell gutter/content lines while keeping continuation gutters blank. */
-function buildWrappedStackCell(
-  cell: StackLineCell,
+/** Build wrapped unified-cell gutter/content lines while keeping continuation gutters blank. */
+function buildWrappedUnifiedCell(
+  cell: UnifiedLineCell,
   geometry: CodeCellLayoutPlan,
   lineNumberDigits: number,
   showLineNumbers: boolean,
   theme: AppTheme,
 ) {
-  const palette = stackCellPalette(cell.kind, theme, cell.moveKind);
-  const firstGutterText = stackGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(
+  const palette = unifiedCellPalette(cell.kind, theme, cell.moveKind);
+  const firstGutterText = unifiedGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(
     geometry.gutterWidth,
   );
   const wrappedSpans = wrapSpans(cell.spans, geometry.contentWidth);
@@ -721,8 +721,8 @@ function renderSplitCell(
   );
 }
 
-/** Render selection-invariant stack-cell content behind its independently painted rail. */
-const StackCellContent = memo(function StackCellContent({
+/** Render selection-invariant unified-cell content behind its independently painted rail. */
+const UnifiedCellContent = memo(function UnifiedCellContent({
   cell,
   gutterWidth,
   contentWidth,
@@ -734,7 +734,7 @@ const StackCellContent = memo(function StackCellContent({
   prefixWidth,
   highlight,
 }: {
-  cell: StackLineCell;
+  cell: UnifiedLineCell;
   gutterWidth: number;
   contentWidth: number;
   lineNumberDigits: number;
@@ -745,7 +745,7 @@ const StackCellContent = memo(function StackCellContent({
   prefixWidth: number;
   highlight?: CodeCellHighlight;
 }) {
-  const basePalette = stackCellPalette(cell.kind, theme, cell.moveKind);
+  const basePalette = unifiedCellPalette(cell.kind, theme, cell.moveKind);
   const palette = highlightsWholeCell(highlight)
     ? applyHighlightPalette(basePalette, highlight!.bg)
     : basePalette;
@@ -759,7 +759,7 @@ const StackCellContent = memo(function StackCellContent({
   return (
     <>
       <span key={`${keyPrefix}:gutter`} fg={palette.numberColor} bg={palette.gutterBg}>
-        {stackGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(gutterWidth)}
+        {unifiedGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(gutterWidth)}
       </span>
       {renderInlineSpans(
         cell.spans,
@@ -775,9 +775,9 @@ const StackCellContent = memo(function StackCellContent({
   );
 });
 
-/** Render one stack-view cell while letting a rail-only selection change skip its code spans. */
-function renderStackCell(
-  cell: StackLineCell,
+/** Render one unified-view cell while letting a rail-only selection change skip its code spans. */
+function renderUnifiedCell(
+  cell: UnifiedLineCell,
   geometry: CodeCellLayoutPlan,
   lineNumberDigits: number,
   showLineNumbers: boolean,
@@ -802,7 +802,7 @@ function renderStackCell(
           {resolvedPrefix.text}
         </span>
       ) : null}
-      <StackCellContent
+      <UnifiedCellContent
         key={`${keyPrefix}:body`}
         cell={cell}
         gutterWidth={geometry.gutterWidth}
@@ -876,10 +876,10 @@ function renderWrappedSplitCellLine(
   );
 }
 
-/** Render one already-wrapped stack cell line with its persistent rail prefix. */
-function renderWrappedStackCellLine(
+/** Render one already-wrapped unified cell line with its persistent rail prefix. */
+function renderWrappedUnifiedCellLine(
   line: WrappedCellLine,
-  palette: ReturnType<typeof stackCellPalette>,
+  palette: ReturnType<typeof unifiedCellPalette>,
   contentWidth: number,
   theme: AppTheme,
   keyPrefix: string,
@@ -978,7 +978,7 @@ function withRowLineHighlights(
     return left === row.left && right === row.right ? row : { ...row, left, right };
   }
 
-  if (row.type === "stack-line") {
+  if (row.type === "unified-line") {
     const cell = row.cell;
     // Context cells carry both numbers pointing at one merged range list, so
     // consulting the new side first never hides an old-side mark.
@@ -992,7 +992,7 @@ function withRowLineHighlights(
     if (!ranges) {
       return row;
     }
-    const contentBg = stackCellPalette(cell.kind, theme, cell.moveKind).contentBg;
+    const contentBg = unifiedCellPalette(cell.kind, theme, cell.moveKind).contentBg;
     return {
       ...row,
       cell: {
@@ -1096,9 +1096,9 @@ function renderNowrapSplitCodeCells({
   );
 }
 
-interface NowrapStackCodeCellOptions {
-  row: Extract<DiffRow, { type: "stack-line" }>;
-  layout: Extract<CodeRowLayoutPlan, { kind: "stack" }>;
+interface NowrapUnifiedCodeCellOptions {
+  row: Extract<DiffRow, { type: "unified-line" }>;
+  layout: Extract<CodeRowLayoutPlan, { kind: "unified" }>;
   lineNumberDigits: number;
   showLineNumbers: boolean;
   theme: AppTheme;
@@ -1108,8 +1108,8 @@ interface NowrapStackCodeCellOptions {
   guideOnNewSide: boolean;
 }
 
-/** Paint one nowrap stack row, retaining the direct-chunk path when it is unhighlighted. */
-function renderNowrapStackCodeCell({
+/** Paint one nowrap unified row, retaining the direct-chunk path when it is unhighlighted. */
+function renderNowrapUnifiedCodeCell({
   row,
   layout,
   lineNumberDigits,
@@ -1119,10 +1119,10 @@ function renderNowrapStackCodeCell({
   prefix,
   highlight,
   guideOnNewSide,
-}: NowrapStackCodeCellOptions) {
+}: NowrapUnifiedCodeCellOptions) {
   if (!highlight) {
     const chunks: TextChunk[] = [];
-    appendPlainStackCellChunks(
+    appendPlainUnifiedCellChunks(
       chunks,
       row.cell,
       layout.cell,
@@ -1138,13 +1138,13 @@ function renderNowrapStackCodeCell({
 
   return (
     <text key={`${row.key}:painted`}>
-      {renderStackCell(
+      {renderUnifiedCell(
         row.cell,
         layout.cell,
         lineNumberDigits,
         showLineNumbers,
         theme,
-        `${row.key}:stack`,
+        `${row.key}:unified`,
         horizontalOffset,
         prefix,
         highlight,
@@ -1167,7 +1167,7 @@ function appendNoteGuideChunk(chunks: TextChunk[], enabled: boolean, theme: AppT
 export interface WrappedCodeCellLineHighlights {
   left?: CodeCellHighlight;
   right?: CodeCellHighlight;
-  stack?: CodeCellHighlight;
+  unified?: CodeCellHighlight;
 }
 
 export interface WrappedCodeCells {
@@ -1292,13 +1292,13 @@ function createWrappedSplitCodeCells({
   };
 }
 
-interface WrappedStackCodeCellOptions extends Omit<
-  NowrapStackCodeCellOptions,
+interface WrappedUnifiedCodeCellOptions extends Omit<
+  NowrapUnifiedCodeCellOptions,
   "horizontalOffset"
 > {}
 
-/** Build a wrapped stack-row painter whose line count and chunks share one wrapped layout. */
-function createWrappedStackCodeCell({
+/** Build a wrapped unified-row painter whose line count and chunks share one wrapped layout. */
+function createWrappedUnifiedCodeCell({
   row,
   layout,
   lineNumberDigits,
@@ -1307,8 +1307,8 @@ function createWrappedStackCodeCell({
   prefix,
   highlight,
   guideOnNewSide,
-}: WrappedStackCodeCellOptions): WrappedCodeCells {
-  const wrapped = buildWrappedStackCell(
+}: WrappedUnifiedCodeCellOptions): WrappedCodeCells {
+  const wrapped = buildWrappedUnifiedCell(
     row.cell,
     layout.cell,
     lineNumberDigits,
@@ -1320,7 +1320,7 @@ function createWrappedStackCodeCell({
     lineCount: wrapped.lines.length,
     contentBackground: wrapped.palette.contentBg,
     paintLine(index, trailingWidth = 0, highlights) {
-      const resolvedHighlight = highlights ? highlights.stack : highlight;
+      const resolvedHighlight = highlights ? highlights.unified : highlight;
       const line = wrapped.lines[index]!;
       let styledRow: StyledText;
       if (isChunkCompatibleWrappedHighlight(resolvedHighlight)) {
@@ -1338,12 +1338,12 @@ function createWrappedStackCodeCell({
         styledRow = new StyledText(chunks);
       } else {
         styledRow = styledTextFromSpanNodes([
-          renderWrappedStackCellLine(
+          renderWrappedUnifiedCellLine(
             line,
             wrapped.palette,
             layout.cell.contentWidth,
             theme,
-            `${row.key}:stack:${index}`,
+            `${row.key}:unified:${index}`,
             prefix,
             resolvedHighlight,
           ),
@@ -1391,8 +1391,8 @@ function spacerContent(width: number, background: string) {
 export const codeCellView = {
   applyLineHighlights: withRowLineHighlights,
   createWrappedSplit: createWrappedSplitCodeCells,
-  createWrappedStack: createWrappedStackCodeCell,
+  createWrappedUnified: createWrappedUnifiedCodeCell,
   renderNowrapSplit: renderNowrapSplitCodeCells,
-  renderNowrapStack: renderNowrapStackCodeCell,
+  renderNowrapUnified: renderNowrapUnifiedCodeCell,
   spacerContent,
 };
diff --git a/packages/hunk/src/ui/diff/CodeRowView.test.tsx b/packages/hunk/src/ui/diff/CodeRowView.test.tsx
index 64191f8e3..66694a786 100644
--- a/packages/hunk/src/ui/diff/CodeRowView.test.tsx
+++ b/packages/hunk/src/ui/diff/CodeRowView.test.tsx
@@ -9,8 +9,8 @@ import type { PlannedCodeReviewRow } from "./reviewRenderPlan";
 import {
   cursorLineHighlightBg,
   selectionHighlightBg,
-  stackCellPalette,
-  stackRailColor,
+  unifiedCellPalette,
+  unifiedRailColor,
 } from "./rowStyle";
 
 /** Return the normalized background painted behind matching captured text. */
@@ -44,7 +44,7 @@ test("CodeRowView limits character selections to source text instead of cell chr
     fileId: "paint",
     hunkIndex: 0,
     row: {
-      type: "stack-line",
+      type: "unified-line",
       key: "character-range",
       fileId: "paint",
       hunkIndex: 0,
@@ -76,7 +76,7 @@ test("CodeRowView limits character selections to source text instead of cell chr
       await setup.renderOnce();
     });
     const spans = setup.captureSpans();
-    const palette = stackCellPalette("addition", theme);
+    const palette = unifiedCellPalette("addition", theme);
 
     expect(backgroundForText(spans, "lec")).toBe(
       selectionHighlightBg(palette.contentBg, theme).toLowerCase(),
@@ -86,7 +86,7 @@ test("CodeRowView limits character selections to source text instead of cell chr
     expect(backgroundForText(spans, "▌")).toBe(theme.panel.toLowerCase());
     expect(foregroundForText(spans, "+ ")).toBe(palette.numberColor.toLowerCase());
     expect(foregroundForText(spans, "▌")).toBe(
-      stackRailColor("addition", theme, false).toLowerCase(),
+      unifiedRailColor("addition", theme, false).toLowerCase(),
     );
   } finally {
     await act(async () => {
@@ -104,7 +104,7 @@ test("CodeRowView paints wrapped selection boundaries per visual line", async ()
     fileId: "paint",
     hunkIndex: 0,
     row: {
-      type: "stack-line",
+      type: "unified-line",
       key: "wrapped-selection",
       fileId: "paint",
       hunkIndex: 0,
@@ -123,7 +123,7 @@ test("CodeRowView paints wrapped selection boundaries per visual line", async ()
     showLineNumbers: false,
     wrapLines: true,
   });
-  if (!layout || layout.kind !== "stack") throw new Error("Expected stack layout");
+  if (!layout || layout.kind !== "unified") throw new Error("Expected unified layout");
   const contentStart = layout.cell.prefixWidth + layout.cell.gutterWidth;
   const setup = await testRender(
     <CodeRowView
@@ -154,7 +154,7 @@ test("CodeRowView paints wrapped selection boundaries per visual line", async ()
     });
     const lines = setup.captureSpans().lines;
     const selectedBg = selectionHighlightBg(
-      stackCellPalette("addition", theme).contentBg,
+      unifiedCellPalette("addition", theme).contentBg,
       theme,
     ).toLowerCase();
     const backgroundInLine = (line: (typeof lines)[number], text: string) =>
@@ -163,13 +163,13 @@ test("CodeRowView paints wrapped selection boundaries per visual line", async ()
       )?.toLowerCase();
 
     expect(backgroundInLine(lines[0]!, "ab")).toBe(
-      stackCellPalette("addition", theme).contentBg.toLowerCase(),
+      unifiedCellPalette("addition", theme).contentBg.toLowerCase(),
     );
     expect(backgroundInLine(lines[0]!, "c")).toBe(selectedBg);
     expect(backgroundInLine(lines[1]!, "j")).toBe(selectedBg);
     expect(backgroundInLine(lines[2]!, "s")).toBe(selectedBg);
     expect(backgroundInLine(lines[2]!, "u")).toBe(
-      stackCellPalette("addition", theme).contentBg.toLowerCase(),
+      unifiedCellPalette("addition", theme).contentBg.toLowerCase(),
     );
   } finally {
     await act(async () => setup.renderer.destroy());
@@ -185,7 +185,7 @@ test("CodeRowView gives copy selection precedence over cursor paint", async () =
     fileId: "paint",
     hunkIndex: 0,
     row: {
-      type: "stack-line",
+      type: "unified-line",
       key: "precedence",
       fileId: "paint",
       hunkIndex: 0,
@@ -218,7 +218,7 @@ test("CodeRowView gives copy selection precedence over cursor paint", async () =
       await setup.renderOnce();
     });
     const background = backgroundForText(setup.captureSpans(), "selected");
-    const baseBackground = stackCellPalette("addition", theme).contentBg;
+    const baseBackground = unifiedCellPalette("addition", theme).contentBg;
 
     expect(background).toBe(selectionHighlightBg(baseBackground, theme).toLowerCase());
     expect(background).not.toBe(cursorLineHighlightBg(baseBackground, theme).toLowerCase());
@@ -240,7 +240,7 @@ test("CodeRowView overlays the nowrap add-note badge instead of shifting the not
     anchorId: "note-guide",
     noteGuideSide: "new",
     row: {
-      type: "stack-line",
+      type: "unified-line",
       key: "note-guide-hover",
       fileId: "paint",
       hunkIndex: 0,
diff --git a/packages/hunk/src/ui/diff/CodeRowView.tsx b/packages/hunk/src/ui/diff/CodeRowView.tsx
index 28c389309..5a2dd6b1d 100644
--- a/packages/hunk/src/ui/diff/CodeRowView.tsx
+++ b/packages/hunk/src/ui/diff/CodeRowView.tsx
@@ -1,4 +1,4 @@
-/** Mounts split and stack code rows from the canonical code-row layout and paint plans. */
+/** Mounts split and unified code rows from the canonical code-row layout and paint plans. */
 import type { UserNoteLineTarget } from "../../core/liveComments";
 import { copySelectedRangeAtVisualLine, type CopySelectedRowRange } from "../lib/diffSpatial";
 import type { AppTheme } from "../themes";
@@ -18,7 +18,7 @@ import {
   selectionHighlightBg,
   splitLeftRailColor,
   splitRightRailColor,
-  stackRailColor,
+  unifiedRailColor,
 } from "./rowStyle";
 import { markNestedRowMouseAction } from "./rowMouseActions";
 
@@ -106,7 +106,7 @@ function renderAddNoteSpacer(key: string, width: number, bg: string) {
   );
 }
 
-/** Mount one split or stack code row with selection, cursor, guide, and affordance paint. */
+/** Mount one split or unified code row with selection, cursor, guide, and affordance paint. */
 export function CodeRowView({
   plannedRow,
   width,
@@ -175,7 +175,7 @@ export function CodeRowView({
         lineHasSelection && copySelectedSide !== "left",
         onCursorRow && (splitContextRow || cursorHighlight.side === "new"),
       ),
-      stack: pickRowHighlight(
+      unified: pickRowHighlight(
         lineSelectionHighlight,
         cursorRowHighlight,
         lineHasSelection,
@@ -186,7 +186,7 @@ export function CodeRowView({
   const firstLineHighlights = highlightsAtVisualLine(0);
   const leftHighlight = firstLineHighlights.left;
   const rightHighlight = firstLineHighlights.right;
-  const cellHighlight = firstLineHighlights.stack;
+  const cellHighlight = firstLineHighlights.unified;
 
   if (row.type === "split-line") {
     // The planner and row type are derived from the same complete planned row.
@@ -311,13 +311,13 @@ export function CodeRowView({
   }
 
   // The planner and row type are derived from the same complete planned row.
-  const stackLayout = codeRowLayout as Extract<CodeRowLayoutPlan, { kind: "stack" }>;
-  const hasRangeGuide = stackLayout.noteGuideSide !== undefined;
+  const unifiedLayout = codeRowLayout as Extract<CodeRowLayoutPlan, { kind: "unified" }>;
+  const hasRangeGuide = unifiedLayout.noteGuideSide !== undefined;
   const addNoteTarget = resolveCodeRowNoteTarget(row);
-  const addBadgeWidth = stackLayout.addNoteBadgeWidth;
+  const addBadgeWidth = unifiedLayout.addNoteBadgeWidth;
   const prefix = {
     text: diffRailMarker(),
-    fg: stackRailColor(row.cell.kind, theme, selected),
+    fg: unifiedRailColor(row.cell.kind, theme, selected),
     bg: theme.panel,
   };
 
@@ -335,9 +335,9 @@ export function CodeRowView({
         onMouseMove={() => onHoverRow?.(row.key)}
       >
         <box style={{ width: "100%", height: 1 }}>
-          {codeCellView.renderNowrapStack({
+          {codeCellView.renderNowrapUnified({
             row,
-            layout: stackLayout,
+            layout: unifiedLayout,
             lineNumberDigits,
             showLineNumbers,
             theme,
@@ -362,9 +362,9 @@ export function CodeRowView({
     );
   }
 
-  const wrapped = codeCellView.createWrappedStack({
+  const wrapped = codeCellView.createWrappedUnified({
     row,
-    layout: stackLayout,
+    layout: unifiedLayout,
     lineNumberDigits,
     showLineNumbers,
     theme,
diff --git a/packages/hunk/src/ui/diff/DiffSectionBody.tsx b/packages/hunk/src/ui/diff/DiffSectionBody.tsx
index d2deddb76..a16096c66 100644
--- a/packages/hunk/src/ui/diff/DiffSectionBody.tsx
+++ b/packages/hunk/src/ui/diff/DiffSectionBody.tsx
@@ -40,11 +40,11 @@ export interface ActiveAddNoteAffordance {
   target?: UserNoteLineTarget;
 }
 
-type AddNoteTargetRow = Extract<DiffRow, { type: "split-line" | "stack-line" }>;
+type AddNoteTargetRow = Extract<DiffRow, { type: "split-line" | "unified-line" }>;
 
 /** Return whether a diff row can be used as an inline user-note target. */
 function isAddNoteTargetRow(row: DiffRow): row is AddNoteTargetRow {
-  return row.type === "split-line" || row.type === "stack-line";
+  return row.type === "split-line" || row.type === "unified-line";
 }
 
 /** Resolve the note insertion target represented by a visible add-note affordance. */
@@ -55,7 +55,7 @@ function addNoteAffordanceForRow(row: AddNoteTargetRow): ActiveAddNoteAffordance
   };
 }
 
-/** Render a file diff in split or stack mode, with inline agent notes inserted between diff rows. */
+/** Render a file diff in split or unified mode, with inline agent notes inserted between diff rows. */
 export function DiffSectionBody({
   codeHorizontalOffset = 0,
   copySelectedRowRanges,
diff --git a/packages/hunk/src/ui/diff/codeColumns.test.ts b/packages/hunk/src/ui/diff/codeColumns.test.ts
index 9314b1f56..4c2b44761 100644
--- a/packages/hunk/src/ui/diff/codeColumns.test.ts
+++ b/packages/hunk/src/ui/diff/codeColumns.test.ts
@@ -84,10 +84,10 @@ describe("findMaxLineNumberInRows", () => {
     expect(findMaxLineNumberInRows(rows)).toBe(1000);
   });
 
-  test("accounts for synthesized stack expansion rows", () => {
+  test("accounts for synthesized unified expansion rows", () => {
     const rows: DiffRow[] = [
       {
-        type: "stack-line",
+        type: "unified-line",
         key: "file:expanded:trailing:0:0",
         fileId: "file",
         hunkIndex: 0,
diff --git a/packages/hunk/src/ui/diff/codeColumns.ts b/packages/hunk/src/ui/diff/codeColumns.ts
index c9866a18a..efb9686c4 100644
--- a/packages/hunk/src/ui/diff/codeColumns.ts
+++ b/packages/hunk/src/ui/diff/codeColumns.ts
@@ -101,7 +101,7 @@ export function findMaxLineNumberInRows(rows: Iterable<DiffRow>, fallback = 1) {
       continue;
     }
 
-    if (row.type === "stack-line") {
+    if (row.type === "unified-line") {
       highest = Math.max(highest, row.cell.oldLineNumber ?? 0, row.cell.newLineNumber ?? 0);
     }
   }
@@ -137,8 +137,8 @@ export function resolveSplitCellGeometry(
   };
 }
 
-/** Resolve the stack-cell gutter and code viewport after the left rail prefix. */
-export function resolveStackCellGeometry(
+/** Resolve the unified-cell gutter and code viewport after the left rail prefix. */
+export function resolveUnifiedCellGeometry(
   width: number,
   lineNumberDigits: number,
   showLineNumbers: boolean,
@@ -168,5 +168,5 @@ export function resolveCodeViewportWidth(
     );
   }
 
-  return resolveStackCellGeometry(width, lineNumberDigits, showLineNumbers).contentWidth;
+  return resolveUnifiedCellGeometry(width, lineNumberDigits, showLineNumbers).contentWidth;
 }
diff --git a/packages/hunk/src/ui/diff/codeRowAffordance.test.ts b/packages/hunk/src/ui/diff/codeRowAffordance.test.ts
index 5c68e4d57..309940c9d 100644
--- a/packages/hunk/src/ui/diff/codeRowAffordance.test.ts
+++ b/packages/hunk/src/ui/diff/codeRowAffordance.test.ts
@@ -24,11 +24,11 @@ function splitRow(leftLine?: number, rightLine?: number): CodeDiffRow {
   };
 }
 
-/** Build a stack code row with independently optional old and new line numbers. */
-function stackRow(oldLine?: number, newLine?: number): CodeDiffRow {
+/** Build a unified code row with independently optional old and new line numbers. */
+function unifiedRow(oldLine?: number, newLine?: number): CodeDiffRow {
   return {
-    type: "stack-line",
-    key: "stack",
+    type: "unified-line",
+    key: "unified",
     fileId: "file",
     hunkIndex: 2,
     cell: {
@@ -42,18 +42,18 @@ function stackRow(oldLine?: number, newLine?: number): CodeDiffRow {
 }
 
 describe("resolveCodeRowNoteTarget", () => {
-  test("prefers the new side for split and stack rows", () => {
+  test("prefers the new side for split and unified rows", () => {
     expect(resolveCodeRowNoteTarget(splitRow(10, 20))).toEqual({ side: "new", line: 20 });
-    expect(resolveCodeRowNoteTarget(stackRow(10, 20))).toEqual({ side: "new", line: 20 });
+    expect(resolveCodeRowNoteTarget(unifiedRow(10, 20))).toEqual({ side: "new", line: 20 });
   });
 
   test("falls back to the old side for deleted lines", () => {
     expect(resolveCodeRowNoteTarget(splitRow(10))).toEqual({ side: "old", line: 10 });
-    expect(resolveCodeRowNoteTarget(stackRow(10))).toEqual({ side: "old", line: 10 });
+    expect(resolveCodeRowNoteTarget(unifiedRow(10))).toEqual({ side: "old", line: 10 });
   });
 
   test("returns no target when neither side has a line", () => {
     expect(resolveCodeRowNoteTarget(splitRow())).toBeUndefined();
-    expect(resolveCodeRowNoteTarget(stackRow())).toBeUndefined();
+    expect(resolveCodeRowNoteTarget(unifiedRow())).toBeUndefined();
   });
 });
diff --git a/packages/hunk/src/ui/diff/codeRowLayout.test.ts b/packages/hunk/src/ui/diff/codeRowLayout.test.ts
index 64d52f009..e6a43d152 100644
--- a/packages/hunk/src/ui/diff/codeRowLayout.test.ts
+++ b/packages/hunk/src/ui/diff/codeRowLayout.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import { CODE_ROW_ADD_NOTE_BADGE_WIDTH } from "./codeRowAffordance";
-import type { DiffRow, SplitLineCell, StackLineCell } from "./diffRows";
+import type { DiffRow, SplitLineCell, UnifiedLineCell } from "./diffRows";
 import {
   measurePlannedRenderedRowHeight,
   planCodeRowLayout,
@@ -40,17 +40,17 @@ function splitPlannedRow(noteGuideSide?: "old" | "new"): PlannedDiffRow {
   };
 }
 
-/** Build one complete planned stack row for width-boundary layout tests. */
-function stackPlannedRow(noteGuideSide?: "old" | "new"): PlannedDiffRow {
-  const cell: StackLineCell = {
+/** Build one complete planned unified row for width-boundary layout tests. */
+function unifiedPlannedRow(noteGuideSide?: "old" | "new"): PlannedDiffRow {
+  const cell: UnifiedLineCell = {
     kind: "addition",
     sign: "+",
     newLineNumber: 1,
     spans: [{ text: boundaryText }],
   };
   const row: DiffRow = {
-    type: "stack-line",
-    key: "file:stack:1",
+    type: "unified-line",
+    key: "file:unified:1",
     fileId: "file",
     hunkIndex: 0,
     cell,
@@ -103,24 +103,24 @@ describe("planned code-row layout", () => {
     expect(decoratedLines(guided, options).some((line) => line.endsWith("│"))).toBe(false);
   });
 
-  test("stack measurement keeps an external new-side guide outside canonical row text", () => {
+  test("unified measurement keeps an external new-side guide outside canonical row text", () => {
     const options = {
       width: 10,
       lineNumberDigits: 1,
       showLineNumbers: false,
       wrapLines: true,
     } as const;
-    const unguided = stackPlannedRow();
-    const guided = stackPlannedRow("new");
+    const unguided = unifiedPlannedRow();
+    const guided = unifiedPlannedRow("new");
 
     expect(planCodeRowLayout(unguided, options)).toMatchObject({
-      kind: "stack",
+      kind: "unified",
       cell: { contentWidth: 7, wrappedLineCount: 1 },
       trailingGuideWidth: 0,
       wrappedLineCount: 1,
     });
     expect(planCodeRowLayout(guided, options)).toMatchObject({
-      kind: "stack",
+      kind: "unified",
       cell: { contentWidth: 7, wrappedLineCount: 1 },
       trailingGuideWidth: 0,
       wrappedLineCount: 1,
@@ -131,8 +131,8 @@ describe("planned code-row layout", () => {
   });
 
   test("memoizes wrapped measurement while preserving lazy plan construction", () => {
-    for (const row of [splitPlannedRow(), stackPlannedRow()]) {
-      if (row.row.type !== "split-line" && row.row.type !== "stack-line") {
+    for (const row of [splitPlannedRow(), unifiedPlannedRow()]) {
+      if (row.row.type !== "split-line" && row.row.type !== "unified-line") {
         throw new Error("expected a code row");
       }
       const spans = row.row.type === "split-line" ? row.row.right.spans : row.row.cell.spans;
@@ -166,8 +166,8 @@ describe("planned code-row layout", () => {
     }
   });
 
-  test("guide, badge, and wrapping policies reserve the same total width in split and stack", () => {
-    for (const rowFactory of [splitPlannedRow, stackPlannedRow]) {
+  test("guide, badge, and wrapping policies reserve the same total width in split and unified", () => {
+    for (const rowFactory of [splitPlannedRow, unifiedPlannedRow]) {
       for (const noteGuideSide of [undefined, "old", "new"] as const) {
         for (const wrapLines of [false, true]) {
           for (const reserveAddNoteColumn of [false, true]) {
diff --git a/packages/hunk/src/ui/diff/codeRowLayout.ts b/packages/hunk/src/ui/diff/codeRowLayout.ts
index a42ab1fac..6c58a515a 100644
--- a/packages/hunk/src/ui/diff/codeRowLayout.ts
+++ b/packages/hunk/src/ui/diff/codeRowLayout.ts
@@ -3,7 +3,7 @@ import type { AppTheme } from "../themes/types";
 import {
   resolveSplitCellGeometry,
   resolveSplitPaneWidths,
-  resolveStackCellGeometry,
+  resolveUnifiedCellGeometry,
 } from "./codeColumns";
 import { CODE_ROW_ADD_NOTE_BADGE_WIDTH } from "./codeRowAffordance";
 import type { DiffRow, RenderSpan } from "./diffRowModel";
@@ -33,7 +33,7 @@ export interface CodeRowLayoutOptions {
   showAddNoteBadge?: boolean;
 }
 
-/** Concrete split or stack layout used to measure, copy, and paint one planned code row. */
+/** Concrete split or unified layout used to measure, copy, and paint one planned code row. */
 export type CodeRowLayoutPlan =
   | {
       kind: "split";
@@ -47,7 +47,7 @@ export type CodeRowLayoutPlan =
       wrappedLineCount: number;
     }
   | {
-      kind: "stack";
+      kind: "unified";
       cell: CodeCellLayoutPlan;
       noteGuideSide?: "old" | "new";
       trailingGuideWidth: number;
@@ -96,7 +96,7 @@ export function planCodeRowLayout(
   }
 
   const row = plannedRow.row;
-  if (row.type !== "split-line" && row.type !== "stack-line") {
+  if (row.type !== "split-line" && row.type !== "unified-line") {
     return null;
   }
 
@@ -154,7 +154,7 @@ export function planCodeRowLayout(
   }
 
   const cellWidth = Math.max(0, width - trailingGuideWidth - addNoteBadgeWidth);
-  const cellGeometry = resolveStackCellGeometry(
+  const cellGeometry = resolveUnifiedCellGeometry(
     cellWidth,
     lineNumberDigits,
     showLineNumbers,
@@ -170,7 +170,7 @@ export function planCodeRowLayout(
 
   let measuredWrappedLineCount: number | undefined;
   return {
-    kind: "stack",
+    kind: "unified",
     cell,
     noteGuideSide: plannedRow.noteGuideSide,
     trailingGuideWidth,
diff --git a/packages/hunk/src/ui/diff/diffRowModel.ts b/packages/hunk/src/ui/diff/diffRowModel.ts
index c1b5966ea..48625cdbc 100644
--- a/packages/hunk/src/ui/diff/diffRowModel.ts
+++ b/packages/hunk/src/ui/diff/diffRowModel.ts
@@ -25,7 +25,7 @@ export interface SplitLineCell {
   spans: RenderSpan[];
 }
 
-export interface StackLineCell {
+export interface UnifiedLineCell {
   kind: "context" | "addition" | "deletion";
   sign: string;
   oldLineNumber?: number;
@@ -74,11 +74,11 @@ export type DiffRow =
       expandedGapKey?: string;
     }
   | {
-      type: "stack-line";
+      type: "unified-line";
       key: string;
       fileId: string;
       hunkIndex: number;
-      cell: StackLineCell;
+      cell: UnifiedLineCell;
       isExpansionRow?: true;
       /** Exact collapsed gap this synthesized row reveals. */
       expandedGapKey?: string;
diff --git a/packages/hunk/src/ui/diff/diffRows.test.ts b/packages/hunk/src/ui/diff/diffRows.test.ts
index a19cf413b..44bfd07bd 100644
--- a/packages/hunk/src/ui/diff/diffRows.test.ts
+++ b/packages/hunk/src/ui/diff/diffRows.test.ts
@@ -4,7 +4,7 @@ import { createTwoFilesPatch } from "diff";
 import type { DiffFile } from "../../core/changeset/model";
 import {
   buildSplitRows,
-  buildStackRows,
+  buildUnifiedRows,
   HIGHLIGHT_WORKER_MIN_LINES,
   highlightedDiffLineCount,
   loadHighlightedDiff,
@@ -16,7 +16,7 @@ import {
 } from "./diffRows";
 import { resolveSplitPaneWidths } from "./codeColumns";
 import { renderCodeOnlyPlannedRowText, renderDecoratedPlannedRowText } from "./plannedRowText";
-import { stackCellPalette } from "./rowStyle";
+import { unifiedCellPalette } from "./rowStyle";
 import { buildReviewRenderPlan } from "./reviewRenderPlan";
 import { measureTextWidth } from "../lib/text";
 import { TRANSPARENT_BACKGROUND, resolveTheme } from "../themes";
@@ -285,8 +285,8 @@ describe("Pierre diff rows", () => {
     expect(highlighted.additionLines).toHaveLength(0);
 
     // Plain rows still carry the diff itself, so the file stays reviewable without color.
-    const rows = buildStackRows(file, highlighted, theme);
-    expect(rows.some((row) => row.type === "stack-line")).toBe(true);
+    const rows = buildUnifiedRows(file, highlighted, theme);
+    expect(rows.some((row) => row.type === "unified-line")).toBe(true);
 
     // A source file of ordinary size is unaffected.
     expect(shouldHighlightDiff(createDiffFile())).toBe(true);
@@ -353,7 +353,7 @@ describe("Pierre diff rows", () => {
 
     expect(offloaded.compact?.deletionLineMap).toHaveLength(file.metadata.deletionLines.length);
     expect(offloaded.compact?.additionLineMap).toHaveLength(file.metadata.additionLines.length);
-    expect(buildStackRows(file, offloaded, theme)).toEqual(buildStackRows(file, inline, theme));
+    expect(buildUnifiedRows(file, offloaded, theme)).toEqual(buildUnifiedRows(file, inline, theme));
   }, 30_000);
 
   test("falls back to plain spans for an out-of-range compact source mapping", () => {
@@ -435,17 +435,18 @@ describe("Pierre diff rows", () => {
     const file = createLargeSourceBackedDiffFile(6_000);
     const theme = resolveTheme("github-dark-default", null);
     const highlighted = await loadHighlightedDiff(file, theme);
-    const rows = buildStackRows(file, highlighted, theme);
+    const rows = buildUnifiedRows(file, highlighted, theme);
     const functionRow = rows.find(
       (row) =>
-        row.type === "stack-line" && row.cell.spans.some((span) => span.text.includes("def hello")),
+        row.type === "unified-line" &&
+        row.cell.spans.some((span) => span.text.includes("def hello")),
     );
 
     expect(shouldHighlightDiff(file)).toBe(true);
     expect(highlighted.deletionLines).toHaveLength(file.metadata.deletionLines.length);
     expect(highlighted.additionLines).toHaveLength(file.metadata.additionLines.length);
-    expect(functionRow?.type).toBe("stack-line");
-    expect(functionRow?.type === "stack-line" ? functionRow.cell.spans[0]?.fg : undefined).toBe(
+    expect(functionRow?.type).toBe("unified-line");
+    expect(functionRow?.type === "unified-line" ? functionRow.cell.spans[0]?.fg : undefined).toBe(
       "#A5D6FF",
     );
   });
@@ -469,25 +470,25 @@ describe("Pierre diff rows", () => {
     const file = createElixirHeredocDiffFile(sourceFetcher);
     const theme = resolveTheme("github-dark-default", null);
     const highlighted = await loadHighlightedDiff(file, theme);
-    const rows = buildStackRows(file, highlighted, theme);
+    const rows = buildUnifiedRows(file, highlighted, theme);
     const rowFor = (text: string) =>
       rows.find(
         (row) =>
-          row.type === "stack-line" && row.cell.spans.some((span) => span.text.includes(text)),
+          row.type === "unified-line" && row.cell.spans.some((span) => span.text.includes(text)),
       );
     const docRow = rowFor("Line two.");
     const functionRow = rowFor("def");
     const additionRow = rowFor("edited");
 
     expect(sourceFetcher.calls).toEqual(["old", "new"]);
-    expect(docRow?.type === "stack-line" ? docRow.cell.spans[0]?.fg : undefined).toBe("#8B949E");
+    expect(docRow?.type === "unified-line" ? docRow.cell.spans[0]?.fg : undefined).toBe("#8B949E");
     expect(
-      functionRow?.type === "stack-line"
+      functionRow?.type === "unified-line"
         ? functionRow.cell.spans.find((span) => span.text.includes("def"))?.fg
         : undefined,
     ).toBe("#FF7B72");
     expect(
-      additionRow?.type === "stack-line"
+      additionRow?.type === "unified-line"
         ? additionRow.cell.spans.find((span) => span.text.includes("edited"))?.bg
         : undefined,
     ).toBeDefined();
@@ -500,15 +501,16 @@ describe("Pierre diff rows", () => {
     const file = createElixirHeredocDiffFile(sourceFetcher);
     const theme = resolveTheme("github-dark-default", null);
     const highlighted = await loadHighlightedDiff(file, theme);
-    const rows = buildStackRows(file, highlighted, theme);
+    const rows = buildUnifiedRows(file, highlighted, theme);
     const functionRow = rows.find(
       (row) =>
-        row.type === "stack-line" && row.cell.spans.some((span) => span.text.includes("def hello")),
+        row.type === "unified-line" &&
+        row.cell.spans.some((span) => span.text.includes("def hello")),
     );
 
     expect(sourceFetcher.calls).toEqual(["old", "new"]);
-    expect(functionRow?.type).toBe("stack-line");
-    expect(functionRow?.type === "stack-line" ? functionRow.cell.spans[0]?.fg : undefined).toBe(
+    expect(functionRow?.type).toBe("unified-line");
+    expect(functionRow?.type === "unified-line" ? functionRow.cell.spans[0]?.fg : undefined).toBe(
       "#A5D6FF",
     );
   });
@@ -612,10 +614,10 @@ describe("Pierre diff rows", () => {
     const theme = resolveTheme("github-dark-default", null);
     const highlighted = await loadHighlightedDiff(file, theme);
     const addedText = (tabWidth: number) => {
-      const row = buildStackRows(file, highlighted, theme, tabWidth).find(
-        (candidate) => candidate.type === "stack-line" && candidate.cell.kind === "addition",
+      const row = buildUnifiedRows(file, highlighted, theme, tabWidth).find(
+        (candidate) => candidate.type === "unified-line" && candidate.cell.kind === "addition",
       );
-      if (!row || row.type !== "stack-line") {
+      if (!row || row.type !== "unified-line") {
         throw new Error("expected one highlighted addition row");
       }
       return row.cell.spans.map((span) => span.text).join("");
@@ -625,27 +627,27 @@ describe("Pierre diff rows", () => {
     expect(addedText(4)).toBe("let a   = 2;");
   });
 
-  test("builds stacked rows with separate deletion and addition lines", () => {
+  test("builds unified rows with separate deletion and addition lines", () => {
     const file = createDiffFile();
     const theme = resolveTheme("github-light-default", null);
-    const rows = buildStackRows(file, null, theme);
+    const rows = buildUnifiedRows(file, null, theme);
 
     const deletionRow = rows.find(
-      (row) => row.type === "stack-line" && row.cell.kind === "deletion",
+      (row) => row.type === "unified-line" && row.cell.kind === "deletion",
     );
     const additionRow = rows.find(
-      (row) => row.type === "stack-line" && row.cell.kind === "addition",
+      (row) => row.type === "unified-line" && row.cell.kind === "addition",
     );
 
     expect(deletionRow).toBeDefined();
     expect(additionRow).toBeDefined();
 
-    if (!deletionRow || deletionRow.type !== "stack-line") {
-      throw new Error("Expected a stacked deletion row");
+    if (!deletionRow || deletionRow.type !== "unified-line") {
+      throw new Error("Expected a unified deletion row");
     }
 
-    if (!additionRow || additionRow.type !== "stack-line") {
-      throw new Error("Expected a stacked addition row");
+    if (!additionRow || additionRow.type !== "unified-line") {
+      throw new Error("Expected a unified addition row");
     }
 
     expect(deletionRow.cell.oldLineNumber).toBe(1);
@@ -661,32 +663,32 @@ describe("Pierre diff rows", () => {
       additionLines: ["moved"],
     };
     const theme = resolveTheme("github-dark-default", null);
-    const rows = buildStackRows(file, null, theme);
+    const rows = buildUnifiedRows(file, null, theme);
     const movedDeletion = rows.find(
-      (row) => row.type === "stack-line" && row.cell.kind === "deletion",
+      (row) => row.type === "unified-line" && row.cell.kind === "deletion",
     );
     const movedAddition = rows.find(
-      (row) => row.type === "stack-line" && row.cell.kind === "addition",
+      (row) => row.type === "unified-line" && row.cell.kind === "addition",
     );
 
     expect(movedDeletion).toBeDefined();
     expect(movedAddition).toBeDefined();
 
-    if (!movedDeletion || movedDeletion.type !== "stack-line") {
+    if (!movedDeletion || movedDeletion.type !== "unified-line") {
       throw new Error("Expected a moved deletion row");
     }
 
-    if (!movedAddition || movedAddition.type !== "stack-line") {
+    if (!movedAddition || movedAddition.type !== "unified-line") {
       throw new Error("Expected a moved addition row");
     }
 
     expect(movedDeletion.cell.moveKind).toBe("moved");
     expect(movedAddition.cell.moveKind).toBe("moved");
     expect(
-      stackCellPalette(movedDeletion.cell.kind, theme, movedDeletion.cell.moveKind).contentBg,
+      unifiedCellPalette(movedDeletion.cell.kind, theme, movedDeletion.cell.moveKind).contentBg,
     ).toBe(theme.movedRemovedBg);
     expect(
-      stackCellPalette(movedAddition.cell.kind, theme, movedAddition.cell.moveKind).contentBg,
+      unifiedCellPalette(movedAddition.cell.kind, theme, movedAddition.cell.moveKind).contentBg,
     ).toBe(theme.movedAddedBg);
   });
 
@@ -780,10 +782,10 @@ describe("Pierre diff rows", () => {
     expect(measureTextWidth(line.slice(0, centerSeparatorIndex))).toBe(leftWidth);
   });
 
-  test("renders planned stack rows with horizontal copy offset", () => {
+  test("renders planned unified rows with horizontal copy offset", () => {
     const file = createDiffFile();
     const theme = resolveTheme("github-dark-default", null);
-    const rows = buildStackRows(file, null, theme);
+    const rows = buildUnifiedRows(file, null, theme);
     const plannedRows = buildReviewRenderPlan({
       fileId: file.id,
       rows,
@@ -792,13 +794,13 @@ describe("Pierre diff rows", () => {
     const additionRow = plannedRows.find(
       (row) =>
         row.kind === "diff-row" &&
-        row.row.type === "stack-line" &&
+        row.row.type === "unified-line" &&
         row.row.cell.kind === "addition",
     );
 
     expect(additionRow).toBeDefined();
     if (!additionRow || additionRow.kind !== "diff-row") {
-      throw new Error("Expected a planned stack addition row");
+      throw new Error("Expected a planned unified addition row");
     }
 
     const [line] = renderDecoratedPlannedRowText(additionRow, {
@@ -863,11 +865,11 @@ describe("Pierre diff rows", () => {
     const theme = resolveTheme("github-dark-default", null);
     const highlighted = await loadHighlightedDiff(file);
 
-    for (const buildRows of [buildSplitRows, buildStackRows]) {
+    for (const buildRows of [buildSplitRows, buildUnifiedRows]) {
       const rows = buildRows(file, highlighted, theme);
       const allSpans = rows.flatMap((row) => {
         if (row.type === "split-line") return [...row.left.spans, ...row.right.spans];
-        if (row.type === "stack-line") return row.cell.spans;
+        if (row.type === "unified-line") return row.cell.spans;
         return [];
       });
 
@@ -966,7 +968,7 @@ describe("Pierre diff rows", () => {
 
     const theme = resolveTheme("github-dark-default", null);
 
-    for (const buildRows of [buildSplitRows, buildStackRows]) {
+    for (const buildRows of [buildSplitRows, buildUnifiedRows]) {
       const rows = buildRows(file, null, theme);
       const collapsedRows = rows.filter(
         (row): row is Extract<DiffRow, { type: "collapsed" }> => row.type === "collapsed",
@@ -1064,10 +1066,10 @@ describe("Pierre diff rows", () => {
         }),
       );
       const highlighted = await loadHighlightedDiff(file, theme);
-      const spans = buildStackRows(file, highlighted, theme)
+      const spans = buildUnifiedRows(file, highlighted, theme)
         .filter(
-          (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-            row.type === "stack-line" && row.cell.kind === "addition",
+          (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+            row.type === "unified-line" && row.cell.kind === "addition",
         )
         .flatMap((row) => row.cell.spans);
 
@@ -1145,28 +1147,28 @@ describe("Pierre diff rows", () => {
         loadHighlightedDiff(file, nextCustomTheme),
         loadHighlightedDiff(file, variableTheme),
       ]);
-    const baseSpans = buildStackRows(file, baseHighlighted, baseTheme)
+    const baseSpans = buildUnifiedRows(file, baseHighlighted, baseTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
-    const customSpans = buildStackRows(file, customHighlighted, customTheme)
+    const customSpans = buildUnifiedRows(file, customHighlighted, customTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
-    const nextCustomSpans = buildStackRows(file, nextCustomHighlighted, nextCustomTheme)
+    const nextCustomSpans = buildUnifiedRows(file, nextCustomHighlighted, nextCustomTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
-    const variableSpans = buildStackRows(file, variableHighlighted, variableTheme)
+    const variableSpans = buildUnifiedRows(file, variableHighlighted, variableTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
 
@@ -1222,16 +1224,16 @@ describe("Pierre diff rows", () => {
       loadHighlightedDiff(file, baseTheme),
       loadHighlightedDiff(file, customTheme),
     ]);
-    const baseSpans = buildStackRows(file, baseHighlighted, baseTheme)
+    const baseSpans = buildUnifiedRows(file, baseHighlighted, baseTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
-    const customSpans = buildStackRows(file, customHighlighted, customTheme)
+    const customSpans = buildUnifiedRows(file, customHighlighted, customTheme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
 
@@ -1266,10 +1268,10 @@ describe("Pierre diff rows", () => {
     };
     const theme = resolveTheme("catppuccin-mocha", null);
     const highlighted = await loadHighlightedDiff(file, theme);
-    const spans = buildStackRows(file, highlighted, theme)
+    const spans = buildUnifiedRows(file, highlighted, theme)
       .filter(
-        (row): row is Extract<DiffRow, { type: "stack-line" }> =>
-          row.type === "stack-line" && row.cell.kind === "addition",
+        (row): row is Extract<DiffRow, { type: "unified-line" }> =>
+          row.type === "unified-line" && row.cell.kind === "addition",
       )
       .flatMap((row) => row.cell.spans);
 
diff --git a/packages/hunk/src/ui/diff/diffRows.ts b/packages/hunk/src/ui/diff/diffRows.ts
index f50bccf1e..752501c58 100644
--- a/packages/hunk/src/ui/diff/diffRows.ts
+++ b/packages/hunk/src/ui/diff/diffRows.ts
@@ -27,7 +27,7 @@ import { measureTextWidth } from "../lib/text";
 import { sanitizeTerminalLine } from "../../lib/terminalText";
 import { MIN_EMPHASIS_SEPARATION, TRANSPARENT_BACKGROUND, type AppTheme } from "../themes";
 import { expandDiffTabs } from "./codeColumns";
-import type { DiffRow, RenderSpan, SplitLineCell, StackLineCell } from "./diffRowModel";
+import type { DiffRow, RenderSpan, SplitLineCell, UnifiedLineCell } from "./diffRowModel";
 import {
   aliasContextHighlightLines,
   collectHastHighlightRuns,
@@ -104,7 +104,7 @@ export type {
   DiffRow,
   RenderSpan,
   SplitLineCell,
-  StackLineCell,
+  UnifiedLineCell,
 } from "./diffRowModel";
 
 /** Expand source tabs before terminal rendering so downstream geometry stays predictable. */
@@ -114,7 +114,7 @@ function tabify(text: string, tabWidth: number, initialColumn = 0) {
 
 // The expensive part after highlighting is walking Pierre's HAST line tree and flattening it
 // into terminal spans. The same highlighted line objects are reused when files remount or when
-// we build both split and stack rows, so memoize flattened spans by line node + theme/background.
+// we build both split and unified rows, so memoize flattened spans by line node + theme/background.
 const flattenedHighlightedLineCache = new WeakMap<HastNode, Map<string, RenderSpan[]>>();
 const WORD_DIFF_BLEND_STEP = 0.005;
 const WORD_DIFF_MAX_BLEND = 0.2;
@@ -368,9 +368,9 @@ function makeSplitCell(
   } satisfies SplitLineCell;
 }
 
-/** Build the normalized render model for one stack-view cell. */
-function makeStackCell(
-  kind: StackLineCell["kind"],
+/** Build the normalized render model for one unified-view cell. */
+function makeUnifiedCell(
+  kind: UnifiedLineCell["kind"],
   oldLineNumber: number | undefined,
   newLineNumber: number | undefined,
   rawLine: string | undefined,
@@ -413,7 +413,7 @@ function makeStackCell(
     newLineNumber,
     moveKind,
     spans,
-  } satisfies StackLineCell;
+  } satisfies UnifiedLineCell;
 }
 
 /** Describe one collapsed unchanged region in the diff stream. */
@@ -884,8 +884,8 @@ export function buildSplitRows(
   return rows;
 }
 
-/** Expand Pierre metadata into the flat stack-view row stream consumed by the renderer. */
-export function buildStackRows(
+/** Expand Pierre metadata into the flat unified-view row stream consumed by the renderer. */
+export function buildUnifiedRows(
   file: DiffFile,
   highlighted: HighlightedDiffCode | null,
   theme: AppTheme,
@@ -898,12 +898,12 @@ export function buildStackRows(
   for (const [hunkIndex, hunk] of file.metadata.hunks.entries()) {
     const leadingGap = reviewLeadingGap(file.metadata, hunkIndex);
     if (leadingGap) {
-      rows.push(collapsedGapRow(file, leadingGap, "stack:collapsed:"));
+      rows.push(collapsedGapRow(file, leadingGap, "unified:collapsed:"));
     }
 
     rows.push({
       type: "hunk-header",
-      key: `${file.id}:stack:header:${hunkIndex}`,
+      key: `${file.id}:unified:header:${hunkIndex}`,
       fileId: file.id,
       hunkIndex,
       text: formatHunkHeader(hunk),
@@ -918,11 +918,11 @@ export function buildStackRows(
       if (content.type === "context") {
         for (let offset = 0; offset < content.lines; offset += 1) {
           rows.push({
-            type: "stack-line",
-            key: `${file.id}:stack:${hunkIndex}:context:${deletionLineIndex + offset}:${additionLineIndex + offset}`,
+            type: "unified-line",
+            key: `${file.id}:unified:${hunkIndex}:context:${deletionLineIndex + offset}:${additionLineIndex + offset}`,
             fileId: file.id,
             hunkIndex,
-            cell: makeStackCell(
+            cell: makeUnifiedCell(
               "context",
               deletionLineNumber + offset,
               additionLineNumber + offset,
@@ -945,11 +945,11 @@ export function buildStackRows(
 
       for (let offset = 0; offset < content.deletions; offset += 1) {
         rows.push({
-          type: "stack-line",
-          key: `${file.id}:stack:${hunkIndex}:deletion:${deletionLineIndex + offset}`,
+          type: "unified-line",
+          key: `${file.id}:unified:${hunkIndex}:deletion:${deletionLineIndex + offset}`,
           fileId: file.id,
           hunkIndex,
-          cell: makeStackCell(
+          cell: makeUnifiedCell(
             "deletion",
             deletionLineNumber + offset,
             undefined,
@@ -965,11 +965,11 @@ export function buildStackRows(
 
       for (let offset = 0; offset < content.additions; offset += 1) {
         rows.push({
-          type: "stack-line",
-          key: `${file.id}:stack:${hunkIndex}:addition:${additionLineIndex + offset}`,
+          type: "unified-line",
+          key: `${file.id}:unified:${hunkIndex}:addition:${additionLineIndex + offset}`,
           fileId: file.id,
           hunkIndex,
-          cell: makeStackCell(
+          cell: makeUnifiedCell(
             "addition",
             undefined,
             additionLineNumber + offset,
@@ -992,7 +992,7 @@ export function buildStackRows(
 
   const trailingGap = reviewTrailingGap(file.metadata);
   if (trailingGap) {
-    rows.push(collapsedGapRow(file, trailingGap, "stack:collapsed:"));
+    rows.push(collapsedGapRow(file, trailingGap, "unified:collapsed:"));
   }
 
   return rows;
diff --git a/packages/hunk/src/ui/diff/diffSectionGeometry.test.ts b/packages/hunk/src/ui/diff/diffSectionGeometry.test.ts
index 48bc8a78c..515e238ba 100644
--- a/packages/hunk/src/ui/diff/diffSectionGeometry.test.ts
+++ b/packages/hunk/src/ui/diff/diffSectionGeometry.test.ts
@@ -11,16 +11,16 @@ import {
 describe("measureDiffSectionGeometry", () => {
   const theme = resolveTheme("github-dark-default", null);
 
-  test("measures split and stack layouts from the render plan", () => {
+  test("measures split and unified layouts from the render plan", () => {
     const file = createTestDiffFile();
 
     const split = measureDiffSectionGeometry(file, "split", true, theme);
-    const stack = measureDiffSectionGeometry(file, "stack", true, theme);
+    const unified = measureDiffSectionGeometry(file, "unified", true, theme);
 
     expect(split.bodyHeight).toBeGreaterThan(0);
-    expect(stack.bodyHeight).toBeGreaterThan(split.bodyHeight);
+    expect(unified.bodyHeight).toBeGreaterThan(split.bodyHeight);
     expect(split.hunkBounds.get(0)?.height).toBeGreaterThan(0);
-    expect(stack.hunkBounds.get(0)?.height).toBeGreaterThan(split.hunkBounds.get(0)?.height ?? 0);
+    expect(unified.hunkBounds.get(0)?.height).toBeGreaterThan(split.hunkBounds.get(0)?.height ?? 0);
   });
 
   test("reuses no-note geometry for the same file and layout inputs", () => {
@@ -269,7 +269,7 @@ describe("measureDiffSectionGeometry", () => {
 
     const nowrapGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       [],
@@ -279,7 +279,7 @@ describe("measureDiffSectionGeometry", () => {
     );
     const wrappedGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       [],
@@ -437,7 +437,7 @@ describe("measureDiffSectionGeometry", () => {
 
     const nowrapGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       [],
@@ -449,7 +449,7 @@ describe("measureDiffSectionGeometry", () => {
     );
     const wrappedGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       [],
@@ -498,7 +498,7 @@ describe("measureDiffSectionGeometry", () => {
 
     const shortGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       visibleAgentNotes,
@@ -510,7 +510,7 @@ describe("measureDiffSectionGeometry", () => {
     );
     const longGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       visibleAgentNotes,
diff --git a/packages/hunk/src/ui/diff/diffSectionGeometry.ts b/packages/hunk/src/ui/diff/diffSectionGeometry.ts
index 5594b7de3..c4307e1e6 100644
--- a/packages/hunk/src/ui/diff/diffSectionGeometry.ts
+++ b/packages/hunk/src/ui/diff/diffSectionGeometry.ts
@@ -370,7 +370,7 @@ export function measureDiffSectionGeometry(
       stableKey: row.stableKey,
       stableKeys,
       ...(row.kind === "diff-row" &&
-      (row.row.type === "split-line" || row.row.type === "stack-line") &&
+      (row.row.type === "split-line" || row.row.type === "unified-line") &&
       row.row.expandedGapKey
         ? { expandedGapKey: row.row.expandedGapKey }
         : {}),
diff --git a/packages/hunk/src/ui/diff/diffSectionRowPlan.ts b/packages/hunk/src/ui/diff/diffSectionRowPlan.ts
index f6f500c2a..05362a9f3 100644
--- a/packages/hunk/src/ui/diff/diffSectionRowPlan.ts
+++ b/packages/hunk/src/ui/diff/diffSectionRowPlan.ts
@@ -9,7 +9,7 @@ import { findMaxLineNumber, findMaxLineNumberInRows } from "./codeColumns";
 import { expandCollapsedRows, type FileSourceStatus } from "./expandCollapsedRows";
 import {
   buildSplitRows,
-  buildStackRows,
+  buildUnifiedRows,
   type HighlightedDiffCode,
   type RenderSpan,
 } from "./diffRows";
@@ -47,7 +47,7 @@ function buildBaseRows(
 ) {
   return layout === "split"
     ? buildSplitRows(file, highlightedDiff ?? null, theme, tabWidth)
-    : buildStackRows(file, highlightedDiff ?? null, theme, tabWidth);
+    : buildUnifiedRows(file, highlightedDiff ?? null, theme, tabWidth);
 }
 
 /** Build the shared file-level diff plan consumed by rendering and geometry measurement. */
diff --git a/packages/hunk/src/ui/diff/expandCollapsedRows.test.ts b/packages/hunk/src/ui/diff/expandCollapsedRows.test.ts
index 383dbbc41..c2345252c 100644
--- a/packages/hunk/src/ui/diff/expandCollapsedRows.test.ts
+++ b/packages/hunk/src/ui/diff/expandCollapsedRows.test.ts
@@ -169,22 +169,22 @@ describe("expandCollapsedRows", () => {
     expect(third.right.spans[0]?.text).toBe("gamma");
   });
 
-  test("inserts stack-line context rows when layout is stack", () => {
+  test("inserts unified-line context rows when layout is unified", () => {
     const rows: DiffRow[] = [makeCollapsedRow("before", 0, [2, 3], [2, 3]), makeHunkHeader(0)];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: SOURCE },
       side: "new",
     });
 
     const inserted = result.slice(1, 3);
-    expect(inserted.every((row) => row.type === "stack-line")).toBe(true);
+    expect(inserted.every((row) => row.type === "unified-line")).toBe(true);
 
     const first = inserted[0];
-    if (!first || first.type !== "stack-line") {
-      throw new Error("expected stack-line context rows");
+    if (!first || first.type !== "unified-line") {
+      throw new Error("expected unified-line context rows");
     }
     expect(first.cell.kind).toBe("context");
     expect(first.cell.oldLineNumber).toBe(2);
@@ -214,7 +214,7 @@ describe("expandCollapsedRows", () => {
     const rows: DiffRow[] = [makeHunkHeader(0), makeCollapsedRow("trailing", 0, [4, 6], [4, 6])];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("trailing", 0)]),
       sourceStatus: { kind: "loaded", text: SOURCE },
       side: "new",
@@ -222,8 +222,8 @@ describe("expandCollapsedRows", () => {
 
     expect(result.length).toBe(rows.length + 3);
     const last = result[result.length - 1];
-    if (!last || last.type !== "stack-line") {
-      throw new Error("expected synthesized stack-line rows after the trailing collapsed row");
+    if (!last || last.type !== "unified-line") {
+      throw new Error("expected synthesized unified-line rows after the trailing collapsed row");
     }
     expect(last.cell.spans[0]?.text).toBe("zeta");
     expect(last.cell.newLineNumber).toBe(6);
@@ -255,15 +255,15 @@ describe("expandCollapsedRows", () => {
     const rows: DiffRow[] = [makeCollapsedRow("before", 0, [1, 2], [1, 2]), makeHunkHeader(0)];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: sourceWithCrlf },
       side: "new",
     });
 
     const inserted = result[1];
-    if (!inserted || inserted.type !== "stack-line") {
-      throw new Error("expected stack-line context row");
+    if (!inserted || inserted.type !== "unified-line") {
+      throw new Error("expected unified-line context row");
     }
     expect(inserted.cell.spans[0]?.text).toBe("alpha");
   });
@@ -273,15 +273,15 @@ describe("expandCollapsedRows", () => {
     const rows: DiffRow[] = [makeCollapsedRow("before", 0, [1, 1], [1, 1]), makeHunkHeader(0)];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: sourceWithControls },
       side: "new",
     });
 
     const inserted = result[1];
-    if (!inserted || inserted.type !== "stack-line") {
-      throw new Error("expected one stack-line row");
+    if (!inserted || inserted.type !== "unified-line") {
+      throw new Error("expected one unified-line row");
     }
 
     const text = inserted.cell.spans.map((span) => span.text).join("");
@@ -296,7 +296,7 @@ describe("expandCollapsedRows", () => {
     const rows: DiffRow[] = [makeCollapsedRow("before", 0, [1, 1], [1, 1]), makeHunkHeader(0)];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: sourceWithTab },
       tabWidth: 4,
@@ -304,8 +304,8 @@ describe("expandCollapsedRows", () => {
     });
 
     const inserted = result[1];
-    if (!inserted || inserted.type !== "stack-line") {
-      throw new Error("expected one stack-line row");
+    if (!inserted || inserted.type !== "unified-line") {
+      throw new Error("expected one unified-line row");
     }
     expect(inserted.cell.spans[0]?.text).toBe("a   b");
   });
@@ -315,7 +315,7 @@ describe("expandCollapsedRows", () => {
     const calls: Array<{ line: string | undefined; sourceLineNumber: number }> = [];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: SOURCE },
       sourceLineSpans: (line, sourceLineNumber) => {
@@ -331,8 +331,8 @@ describe("expandCollapsedRows", () => {
     ]);
 
     const inserted = result[1];
-    if (!inserted || inserted.type !== "stack-line") {
-      throw new Error("expected stack-line context row");
+    if (!inserted || inserted.type !== "unified-line") {
+      throw new Error("expected unified-line context row");
     }
     expect(inserted.cell.spans).toEqual([{ text: "highlighted:beta", fg: "#abcdef" }]);
   });
@@ -341,7 +341,7 @@ describe("expandCollapsedRows", () => {
     const rows: DiffRow[] = [makeCollapsedRow("before", 0, [1, 3], [1, 3]), makeHunkHeader(0)];
 
     const result = expandCollapsedRows(rows, {
-      layout: "stack",
+      layout: "unified",
       expandedKeys: new Set([reviewGapId("before", 0)]),
       sourceStatus: { kind: "loaded", text: "alpha\n" },
       side: "new",
diff --git a/packages/hunk/src/ui/diff/expandCollapsedRows.ts b/packages/hunk/src/ui/diff/expandCollapsedRows.ts
index e4bfc5088..d525b491a 100644
--- a/packages/hunk/src/ui/diff/expandCollapsedRows.ts
+++ b/packages/hunk/src/ui/diff/expandCollapsedRows.ts
@@ -8,10 +8,10 @@ import type {
   DiffRow,
   RenderSpan,
   SplitLineCell,
-  StackLineCell,
+  UnifiedLineCell,
 } from "./diffRows";
 
-export type ExpansionLayout = "split" | "stack";
+export type ExpansionLayout = "split" | "unified";
 
 /** Per-file load status for the source text used to fill expanded gaps. */
 export type FileSourceStatus =
@@ -80,7 +80,7 @@ function buildSplitContextRow(
   };
 }
 
-function buildStackContextRow(
+function buildUnifiedContextRow(
   fileId: string,
   hunkIndex: number,
   position: CollapsedGapPosition,
@@ -88,8 +88,8 @@ function buildStackContextRow(
   oldLineNumber: number,
   newLineNumber: number,
   spans: RenderSpan[],
-): Extract<DiffRow, { type: "stack-line" }> {
-  const cell: StackLineCell = {
+): Extract<DiffRow, { type: "unified-line" }> {
+  const cell: UnifiedLineCell = {
     kind: "context",
     sign: " ",
     oldLineNumber,
@@ -98,7 +98,7 @@ function buildStackContextRow(
   };
 
   return {
-    type: "stack-line",
+    type: "unified-line",
     key: `${fileId}:expanded:${position}:${hunkIndex}:${index}`,
     fileId,
     hunkIndex,
@@ -209,7 +209,7 @@ export function expandCollapsedRows(
               newLineNumber,
               spans,
             )
-          : buildStackContextRow(
+          : buildUnifiedContextRow(
               row.fileId,
               row.hunkIndex,
               row.position,
diff --git a/packages/hunk/src/ui/diff/lineHighlightPaint.test.ts b/packages/hunk/src/ui/diff/lineHighlightPaint.test.ts
index 75477bb60..886cea52b 100644
--- a/packages/hunk/src/ui/diff/lineHighlightPaint.test.ts
+++ b/packages/hunk/src/ui/diff/lineHighlightPaint.test.ts
@@ -58,7 +58,7 @@ describe("buildLineHighlightPaintIndex", () => {
     const oldRanges = index?.get(lineHighlightPaintKey("old", 1));
     expect(newRanges).toEqual([{ startCol: 0, endCol: 6, tone: "match" }]);
     // The same physical line renders on both split halves; identity equality
-    // keeps stack view from double-counting the mirrored entry.
+    // keeps unified view from double-counting the mirrored entry.
     expect(oldRanges).toBe(newRanges!);
   });
 
diff --git a/packages/hunk/src/ui/diff/lineHighlightPaint.ts b/packages/hunk/src/ui/diff/lineHighlightPaint.ts
index acae28f26..f2d549794 100644
--- a/packages/hunk/src/ui/diff/lineHighlightPaint.ts
+++ b/packages/hunk/src/ui/diff/lineHighlightPaint.ts
@@ -44,7 +44,7 @@ export interface LineHighlightColRange {
  * Column ranges per rendered line, keyed by `lineHighlightPaintKey`.
  *
  * A context line is registered under both its old and new key with one shared
- * range list, so split view mirrors the mark onto both halves and stack view
+ * range list, so split view mirrors the mark onto both halves and unified view
  * finds it through either line number.
  */
 export type LineHighlightPaintIndex = ReadonlyMap<string, readonly LineHighlightColRange[]>;
@@ -276,7 +276,7 @@ export function buildLineHighlightPaintIndex({
 
   const index = new Map<string, LineHighlightColRange[]>();
   // One shared array per physical line: context and gap marks register the
-  // same bucket under both side keys, so split view mirrors them and stack
+  // same bucket under both side keys, so split view mirrors them and unified
   // view finds one list through either line number without double-counting.
   const bucketFor = (key: string, counterpartKey: string | undefined) => {
     let bucket = index.get(key) ?? (counterpartKey ? index.get(counterpartKey) : undefined);
diff --git a/packages/hunk/src/ui/diff/plannedRowText.ts b/packages/hunk/src/ui/diff/plannedRowText.ts
index 1a6c535e4..7a6283577 100644
--- a/packages/hunk/src/ui/diff/plannedRowText.ts
+++ b/packages/hunk/src/ui/diff/plannedRowText.ts
@@ -15,8 +15,8 @@ import {
   type CodeCellLayoutPlan,
   type CodeRowLayoutPlan,
 } from "./codeRowLayout";
-import type { RenderSpan, SplitLineCell, StackLineCell } from "./diffRowModel";
-import { diffRailMarker, splitGutterText, stackGutterText } from "./rowStyle";
+import type { RenderSpan, SplitLineCell, UnifiedLineCell } from "./diffRowModel";
+import { diffRailMarker, splitGutterText, unifiedGutterText } from "./rowStyle";
 import type { PlannedReviewRow } from "./reviewRenderPlan";
 import { wrapSpans } from "./styledSpanLayout";
 
@@ -30,7 +30,7 @@ export interface PlannedRowTextOptions {
   codeHorizontalOffset: number;
   reserveAddNoteColumn?: boolean;
   showAddNoteBadge?: boolean;
-  /** Limits split rows to one pane; stack rows ignore this filter. */
+  /** Limits split rows to one pane; unified rows ignore this filter. */
   side?: "left" | "right";
 }
 
@@ -122,16 +122,16 @@ export function buildPlainSplitCellLines(
   }));
 }
 
-/** Build stack-cell lines from an existing code layout plan. */
-export function buildPlainStackCellLines(
-  cell: StackLineCell,
+/** Build unified-cell lines from an existing code layout plan. */
+export function buildPlainUnifiedCellLines(
+  cell: UnifiedLineCell,
   geometry: CodeCellLayoutPlan,
   lineNumberDigits: number,
   showLineNumbers: boolean,
   wrapLines: boolean,
   codeHorizontalOffset = 0,
 ): PlainCellLine[] {
-  const gutterText = stackGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(
+  const gutterText = unifiedGutterText(cell, lineNumberDigits, showLineNumbers).padEnd(
     geometry.gutterWidth,
   );
   if (!wrapLines) {
@@ -260,17 +260,17 @@ export function renderDecoratedPlannedRowText(
     });
   }
 
-  if (preparedRow.type !== "stack-line") {
+  if (preparedRow.type !== "unified-line") {
     return [];
   }
 
   const codeLayout = planCodeRowLayout(row, options) as Extract<
     CodeRowLayoutPlan,
-    { kind: "stack" }
+    { kind: "unified" }
   >;
   // The external range rail is presentation chrome outside this canonical text width.
   const prefix = diffRailMarker();
-  const cellLines = buildPlainStackCellLines(
+  const cellLines = buildPlainUnifiedCellLines(
     preparedRow.cell,
     codeLayout.cell,
     lineNumberDigits,
@@ -307,14 +307,14 @@ export function renderCodeOnlyPlannedRowText(
     return [];
   }
 
-  if (preparedRow.type === "stack-line") {
+  if (preparedRow.type === "unified-line") {
     if (!wrapLines) {
       return [cellCodeText(preparedRow.cell.spans, codeHorizontalOffset)].filter(Boolean);
     }
 
     const codeLayout = planCodeRowLayout(row, options) as Extract<
       CodeRowLayoutPlan,
-      { kind: "stack" }
+      { kind: "unified" }
     >;
     return wrapSpans(preparedRow.cell.spans, codeLayout.cell.contentWidth)
       .map((spans) => spansText(spans))
diff --git a/packages/hunk/src/ui/diff/reviewRenderPlan.test.ts b/packages/hunk/src/ui/diff/reviewRenderPlan.test.ts
index e874cad90..bc29d40e0 100644
--- a/packages/hunk/src/ui/diff/reviewRenderPlan.test.ts
+++ b/packages/hunk/src/ui/diff/reviewRenderPlan.test.ts
@@ -11,7 +11,7 @@ import {
 } from "./reviewRenderPlan";
 import { resolveTheme } from "../themes";
 
-const { buildSplitRows, buildStackRows } = await import("./diffRows");
+const { buildSplitRows, buildUnifiedRows } = await import("./diffRows");
 const { buildReviewRenderPlan } = await import("./reviewRenderPlan");
 
 function lines(...values: string[]) {
@@ -237,12 +237,12 @@ describe("review render plan", () => {
   test("anchors range-less notes to the shared default line without guide rows", () => {
     const theme = resolveTheme("github-dark-default", null);
     const file = createDiffFile(
-      "stack",
-      "stack.ts",
+      "unified",
+      "unified.ts",
       "export const value = 1;\n",
       "export const value = 2;\nexport const added = true;\n",
     );
-    const rows = buildStackRows(file, null, theme);
+    const rows = buildUnifiedRows(file, null, theme);
     const plannedRows = buildReviewRenderPlan({
       fileId: file.id,
       rows,
@@ -250,7 +250,7 @@ describe("review render plan", () => {
       showHunkHeaders: true,
       visibleAgentNotes: [
         createVisibleAgentNote(file.metadata.hunks, {
-          id: "annotation:stack:0:0",
+          id: "annotation:unified:0:0",
           annotation: {
             summary: "General hunk note",
             rationale: "No explicit line range is attached yet.",
@@ -273,8 +273,8 @@ describe("review render plan", () => {
     const anchoredRow = inlineNoteAnchorRow(plannedRows);
     expect(anchoredRow?.kind).toBe("diff-row");
     if (anchoredRow?.kind === "diff-row") {
-      expect(anchoredRow.row.type).toBe("stack-line");
-      if (anchoredRow.row.type === "stack-line") {
+      expect(anchoredRow.row.type).toBe("unified-line");
+      if (anchoredRow.row.type === "unified-line") {
         expect(anchoredRow.row.cell.newLineNumber).toBe(1);
       }
     }
@@ -436,11 +436,11 @@ describe("review render plan", () => {
 });
 
 describe("hunk-gap rows", () => {
-  test("inserts a spacer before each hunk after the first in split and stack plans", () => {
+  test("inserts a spacer before each hunk after the first in split and unified plans", () => {
     const theme = resolveTheme("github-dark-default", null);
     const file = createDiffFile("multi", "multi.ts", TWELVE_LINES_BEFORE, TWELVE_LINES_AFTER);
 
-    for (const rows of [buildSplitRows(file, null, theme), buildStackRows(file, null, theme)]) {
+    for (const rows of [buildSplitRows(file, null, theme), buildUnifiedRows(file, null, theme)]) {
       expect(
         buildReviewRenderPlan({ fileId: file.id, rows, showHunkHeaders: true }).some(
           (row) => row.kind === "hunk-gap",
diff --git a/packages/hunk/src/ui/diff/reviewRenderPlan.ts b/packages/hunk/src/ui/diff/reviewRenderPlan.ts
index b26d70db2..0deff9b36 100644
--- a/packages/hunk/src/ui/diff/reviewRenderPlan.ts
+++ b/packages/hunk/src/ui/diff/reviewRenderPlan.ts
@@ -10,7 +10,7 @@ import type { DiffRow } from "./diffRows";
 const EMPTY_VISIBLE_AGENT_NOTES: VisibleAgentNote[] = [];
 const EMPTY_ROW_KEYS = new Set<string>();
 
-type DiffLineRow = Extract<DiffRow, { type: "split-line" | "stack-line" }>;
+type DiffLineRow = Extract<DiffRow, { type: "split-line" | "unified-line" }>;
 
 interface InlineVisibleNotePlacement {
   anchorKey: string;
@@ -82,18 +82,18 @@ export function createPlannedDiffReviewRow(
       return { kind: "diff-row", ...fields, row };
     case "split-line":
       return { kind: "diff-row", ...fields, row };
-    case "stack-line":
+    case "unified-line":
       return { kind: "diff-row", ...fields, row };
   }
 }
 
-/** Split or stack code row accepted by code-row rendering and interaction policy. */
-export type CodeDiffRow = Extract<DiffRow, { type: "split-line" | "stack-line" }>;
+/** Split or unified code row accepted by code-row rendering and interaction policy. */
+export type CodeDiffRow = Extract<DiffRow, { type: "split-line" | "unified-line" }>;
 
 /** Collapsed gap or hunk-header row accepted by metadata rendering. */
 export type DiffMetaRow = Extract<DiffRow, { type: "collapsed" | "hunk-header" }>;
 
-/** Planned review row carrying split or stack code cells. */
+/** Planned review row carrying split or unified code cells. */
 export type PlannedCodeReviewRow = PlannedDiffReviewRow<CodeDiffRow>;
 
 /** Planned review row carrying metadata rather than code cells. */
@@ -103,7 +103,7 @@ export type PlannedDiffMetaReviewRow = PlannedDiffReviewRow<DiffMetaRow>;
 export function isPlannedCodeReviewRow(
   plannedRow: PlannedDiffReviewRow,
 ): plannedRow is PlannedCodeReviewRow {
-  return plannedRow.row.type === "split-line" || plannedRow.row.type === "stack-line";
+  return plannedRow.row.type === "split-line" || plannedRow.row.type === "unified-line";
 }
 
 /** Return whether a planned diff row carries a gap or hunk header. */
@@ -115,7 +115,7 @@ export function isPlannedDiffMetaReviewRow(
 
 function lineRows(rows: DiffRow[]) {
   return rows.filter(
-    (row): row is DiffLineRow => row.type === "split-line" || row.type === "stack-line",
+    (row): row is DiffLineRow => row.type === "split-line" || row.type === "unified-line",
   );
 }
 
@@ -216,7 +216,7 @@ export function contextLineStableKeySides(
   };
 }
 
-/** Resolve the stable anchor keys for one rendered diff row across split and stack layouts. */
+/** Resolve the stable anchor keys for one rendered diff row across split and unified layouts. */
 function diffRowStableKeys(row: DiffRow) {
   if (row.type === "collapsed") {
     return [`meta:collapsed:${row.position}:${row.hunkIndex}`];
@@ -241,7 +241,7 @@ function diffRowStableKeys(row: DiffRow) {
       ]);
     }
 
-    // Prefer the old-side line so split→stack toggles stay near the same vertical position even
+    // Prefer the old-side line so split→unified toggles stay near the same vertical position even
     // when one large change block expands into many deletions followed by many additions.
     return uniqueStableKeys([
       oldLineStableKey(row.hunkIndex, row.left.lineNumber),
diff --git a/packages/hunk/src/ui/diff/reviewRowGeometry.ts b/packages/hunk/src/ui/diff/reviewRowGeometry.ts
index 3e08fcb09..5fb1ef854 100644
--- a/packages/hunk/src/ui/diff/reviewRowGeometry.ts
+++ b/packages/hunk/src/ui/diff/reviewRowGeometry.ts
@@ -48,7 +48,7 @@ export function plannedReviewRowContributesToHunkBounds(row: PlannedReviewRow) {
   }
 
   if (
-    (row.row.type === "split-line" || row.row.type === "stack-line") &&
+    (row.row.type === "split-line" || row.row.type === "unified-line") &&
     row.row.isExpansionRow === true
   ) {
     return false;
diff --git a/packages/hunk/src/ui/diff/rowStyle.test.ts b/packages/hunk/src/ui/diff/rowStyle.test.ts
index 8a87eff0a..a7224ec79 100644
--- a/packages/hunk/src/ui/diff/rowStyle.test.ts
+++ b/packages/hunk/src/ui/diff/rowStyle.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, test } from "bun:test";
 import { contrastRatio, hexColorDistance } from "../lib/color";
 import { THEMES, TRANSPARENT_BACKGROUND, withTransparentSurfaces } from "../themes";
-import { cursorLineHighlightBg, lineHighlightToneStyle, stackCellPalette } from "./rowStyle";
+import { cursorLineHighlightBg, lineHighlightToneStyle, unifiedCellPalette } from "./rowStyle";
 
 const DARK = THEMES.find((theme) => theme.id === "github-dark-dimmed")!;
 const LIGHT = THEMES.find((theme) => theme.id === "github-light-default")!;
@@ -10,7 +10,7 @@ describe("cursorLineHighlightBg", () => {
   test("marks context rows on transparent surfaces", () => {
     for (const base of [DARK, LIGHT]) {
       const theme = withTransparentSurfaces(base);
-      const context = stackCellPalette("context", theme);
+      const context = unifiedCellPalette("context", theme);
 
       expect(context.contentBg).toBe(TRANSPARENT_BACKGROUND);
       expect(cursorLineHighlightBg(context.contentBg, theme)).not.toBe(TRANSPARENT_BACKGROUND);
@@ -21,7 +21,7 @@ describe("cursorLineHighlightBg", () => {
     for (const base of THEMES) {
       for (const theme of [base, withTransparentSurfaces(base)]) {
         for (const kind of ["context", "addition", "deletion"] as const) {
-          const marked = cursorLineHighlightBg(stackCellPalette(kind, theme).contentBg, theme);
+          const marked = cursorLineHighlightBg(unifiedCellPalette(kind, theme).contentBg, theme);
           expect(contrastRatio(theme.text, marked)).toBeGreaterThan(3);
         }
       }
@@ -29,8 +29,8 @@ describe("cursorLineHighlightBg", () => {
   });
 
   test("moves added and removed rows as far as it moves context rows", () => {
-    const context = stackCellPalette("context", DARK).contentBg;
-    const added = stackCellPalette("addition", DARK).contentBg;
+    const context = unifiedCellPalette("context", DARK).contentBg;
+    const added = unifiedCellPalette("addition", DARK).contentBg;
 
     const shift = (from: string) => {
       const to = cursorLineHighlightBg(from, DARK);
@@ -48,7 +48,7 @@ describe("lineHighlightToneStyle", () => {
   test("clears a strong visible distance on every line kind of every built-in theme", () => {
     for (const theme of THEMES) {
       for (const kind of ["context", "addition", "deletion"] as const) {
-        const baseBg = stackCellPalette(kind, theme).contentBg;
+        const baseBg = unifiedCellPalette(kind, theme).contentBg;
         for (const tone of TINTED_TONES) {
           const resolved = lineHighlightToneStyle(tone, baseBg, theme);
           expect(resolved).toBeDefined();
@@ -65,7 +65,7 @@ describe("lineHighlightToneStyle", () => {
   test("paints the current mark as reverse video, unmistakable on every theme", () => {
     for (const theme of THEMES) {
       for (const kind of ["context", "addition", "deletion"] as const) {
-        const baseBg = stackCellPalette(kind, theme).contentBg;
+        const baseBg = unifiedCellPalette(kind, theme).contentBg;
         const match = lineHighlightToneStyle("match", baseBg, theme)!;
         const current = lineHighlightToneStyle("current", baseBg, theme)!;
         // Inversion: theme text becomes the block, theme background the glyphs.
@@ -85,7 +85,7 @@ describe("lineHighlightToneStyle", () => {
     // this case silently painted nothing in the common case.
     for (const base of THEMES) {
       const theme = withTransparentSurfaces(base);
-      const contextBg = stackCellPalette("context", theme).contentBg;
+      const contextBg = unifiedCellPalette("context", theme).contentBg;
       expect(contextBg).toBe(TRANSPARENT_BACKGROUND);
       const assumed = theme.appearance === "dark" ? "#000000" : "#ffffff";
 
@@ -113,7 +113,7 @@ describe("lineHighlightToneStyle", () => {
 
   test("keeps code readable over every resolved tinted background", () => {
     for (const theme of THEMES) {
-      const baseBg = stackCellPalette("context", theme).contentBg;
+      const baseBg = unifiedCellPalette("context", theme).contentBg;
       for (const tone of TINTED_TONES) {
         const resolved = lineHighlightToneStyle(tone, baseBg, theme);
         expect(contrastRatio(theme.text, resolved!.bg)).toBeGreaterThan(3);
@@ -124,7 +124,7 @@ describe("lineHighlightToneStyle", () => {
   test("resolves dim tone to transform foreground toward background with readable contrast", () => {
     for (const theme of THEMES) {
       for (const kind of ["context", "addition", "deletion"] as const) {
-        const baseBg = stackCellPalette(kind, theme).contentBg;
+        const baseBg = unifiedCellPalette(kind, theme).contentBg;
         const resolved = lineHighlightToneStyle("dim", baseBg, theme);
         expect(resolved).toBeDefined();
         expect(resolved!.transformFg).toBeDefined();
@@ -149,7 +149,7 @@ describe("lineHighlightToneStyle", () => {
   test("resolves dim tone on transparent surfaces to readable contrast", () => {
     for (const base of THEMES) {
       const theme = withTransparentSurfaces(base);
-      const contextBg = stackCellPalette("context", theme).contentBg;
+      const contextBg = unifiedCellPalette("context", theme).contentBg;
       expect(contextBg).toBe(TRANSPARENT_BACKGROUND);
       const assumedBg = theme.appearance === "dark" ? "#000000" : "#ffffff";
 
diff --git a/packages/hunk/src/ui/diff/rowStyle.ts b/packages/hunk/src/ui/diff/rowStyle.ts
index 1ebf77a7f..ece8031e2 100644
--- a/packages/hunk/src/ui/diff/rowStyle.ts
+++ b/packages/hunk/src/ui/diff/rowStyle.ts
@@ -1,7 +1,7 @@
 import { TRANSPARENT_BACKGROUND, type AppTheme } from "../themes";
 import { blendHex, contrastRatio, hexColorDistance } from "../lib/color";
 import type { ExtensionLineHighlightTone } from "../../extension-api/types";
-import type { SplitLineCell, StackLineCell } from "./diffRows";
+import type { SplitLineCell, UnifiedLineCell } from "./diffRows";
 
 const INACTIVE_RAIL_BLEND = 0.35;
 const SELECTION_BG_BLEND = 0.75;
@@ -29,7 +29,7 @@ function cachedRowBackground(
   return background;
 }
 
-/** The diff rail marker is always visible in Hunk stack and split rows. */
+/** The diff rail marker is always visible in Hunk unified and split rows. */
 export function diffRailMarker() {
   return "▌";
 }
@@ -77,8 +77,12 @@ export function dimRailColor(color: string, theme: AppTheme) {
   return blendHex(color, theme.panel, INACTIVE_RAIL_BLEND);
 }
 
-/** Pick the stack-view rail color for one rendered row. */
-export function stackRailColor(kind: StackLineCell["kind"], theme: AppTheme, selected: boolean) {
+/** Pick the unified-view rail color for one rendered row. */
+export function unifiedRailColor(
+  kind: UnifiedLineCell["kind"],
+  theme: AppTheme,
+  selected: boolean,
+) {
   let color: string;
 
   if (kind === "addition") {
@@ -153,11 +157,11 @@ export function splitCellPalette(
   };
 }
 
-/** Pick stack-view colors from the semantic diff cell kind. */
-export function stackCellPalette(
-  kind: StackLineCell["kind"],
+/** Pick unified-view colors from the semantic diff cell kind. */
+export function unifiedCellPalette(
+  kind: UnifiedLineCell["kind"],
   theme: AppTheme,
-  moveKind?: StackLineCell["moveKind"],
+  moveKind?: UnifiedLineCell["moveKind"],
 ) {
   if (kind === "addition") {
     return {
@@ -428,9 +432,9 @@ export function diffLineNumberText(value: number | undefined, width: number) {
   return value === undefined ? " ".repeat(width) : String(value).padStart(width, " ");
 }
 
-/** Build the stack-view gutter text shared by the TUI and static pager renderers. */
-export function stackGutterText(
-  cell: StackLineCell,
+/** Build the unified-view gutter text shared by the TUI and static pager renderers. */
+export function unifiedGutterText(
+  cell: UnifiedLineCell,
   lineNumberDigits: number,
   showLineNumbers: boolean,
 ) {
diff --git a/packages/hunk/src/ui/fileViews/geometry.test.ts b/packages/hunk/src/ui/fileViews/geometry.test.ts
index be90aec9e..06616af0a 100644
--- a/packages/hunk/src/ui/fileViews/geometry.test.ts
+++ b/packages/hunk/src/ui/fileViews/geometry.test.ts
@@ -114,7 +114,7 @@ describe("file-view geometry", () => {
     const noteHeight = measureAgentInlineNoteHeight({
       annotation,
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 80,
     });
     const geometry = measureFileViewGeometry({
diff --git a/packages/hunk/src/ui/fileViews/geometry.ts b/packages/hunk/src/ui/fileViews/geometry.ts
index 997125e75..74855c8af 100644
--- a/packages/hunk/src/ui/fileViews/geometry.ts
+++ b/packages/hunk/src/ui/fileViews/geometry.ts
@@ -18,8 +18,8 @@ function plannedFileViewRowHeight(
   return measureAgentInlineNoteHeight({
     annotation: row.annotation,
     anchorSide: row.anchorSide,
-    // Alternate presentations are one full-width stack even when raw code uses split columns.
-    layout: "stack",
+    // Alternate presentations are one full-width unified even when raw code uses split columns.
+    layout: "unified",
     width,
     actions: row.note.actions,
     threadDepth: row.note.thread?.depth,
diff --git a/packages/hunk/src/ui/hooks/useCurrentReviewRefreshController.test.tsx b/packages/hunk/src/ui/hooks/useCurrentReviewRefreshController.test.tsx
index 023ac86b5..ee03f5ce7 100644
--- a/packages/hunk/src/ui/hooks/useCurrentReviewRefreshController.test.tsx
+++ b/packages/hunk/src/ui/hooks/useCurrentReviewRefreshController.test.tsx
@@ -46,7 +46,7 @@ function RefreshHarness({
     reloadContext: { cwd: "/repo" },
     sourceLabel: "/repo",
     view: {
-      layoutMode: "stack",
+      layoutMode: "unified",
       themeId,
       showAgentNotes: true,
       showHunkHeaders: true,
diff --git a/packages/hunk/src/ui/hooks/useExtensionReviewEvents.test.tsx b/packages/hunk/src/ui/hooks/useExtensionReviewEvents.test.tsx
index b2e443c5d..a492a9610 100644
--- a/packages/hunk/src/ui/hooks/useExtensionReviewEvents.test.tsx
+++ b/packages/hunk/src/ui/hooks/useExtensionReviewEvents.test.tsx
@@ -2,10 +2,9 @@ import { describe, expect, test } from "bun:test";
 import { testRender } from "@opentui/react/test-utils";
 import { act, Activity, StrictMode, useLayoutEffect, useState } from "react";
 import { createTestDiffFile } from "../../../../../test/helpers/diff-helpers";
+import type { LayoutMode } from "../../core/run/commandInputs";
 import type {
   ExtensionEventPayloads,
-  ExtensionLayoutMode,
-  ExtensionResolvedLayout,
   ExtensionReviewSnapshotNote,
 } from "../../extension-api/types";
 import {
@@ -129,8 +128,8 @@ function observeReviewEvents(extensions: ExtensionLoadResult, seen: SeenEvent[])
 interface ReviewEventFacts {
   extensions: ExtensionLoadResult;
   filter: string;
-  layoutMode: ExtensionLayoutMode;
-  resolvedLayout: ExtensionResolvedLayout;
+  layoutMode: LayoutMode;
+  resolvedLayout: Exclude<LayoutMode, "auto">;
   reviewGeneration?: string;
   reviewNotes?: readonly ExtensionReviewSnapshotNote[];
   selectedFile: ExtensionDiffFile | null;
@@ -360,8 +359,8 @@ describe("useExtensionReviewEvents", () => {
       await act(async () =>
         harness.updateFacts({
           filter: "src/",
-          layoutMode: "stack",
-          resolvedLayout: "stack",
+          layoutMode: "unified",
+          resolvedLayout: "unified",
           themeId: "github-light-default",
         }),
       );
@@ -369,7 +368,15 @@ describe("useExtensionReviewEvents", () => {
 
       expect(seen).toEqual([
         { event: "filter_changed", payload: { filter: "src/" } },
-        { event: "layout_changed", payload: { mode: "stack", layout: "stack" } },
+        {
+          event: "layout_changed",
+          payload: {
+            mode: "stack",
+            layout: "stack",
+            canonicalMode: "unified",
+            canonicalLayout: "unified",
+          },
+        },
         { event: "theme_changed", payload: { themeId: "github-light-default" } },
       ]);
     } finally {
@@ -479,8 +486,8 @@ describe("useExtensionReviewEvents", () => {
         harness.updateFacts({
           extensions: secondExtensions,
           filter: "src/",
-          layoutMode: "stack",
-          resolvedLayout: "stack",
+          layoutMode: "unified",
+          resolvedLayout: "unified",
           themeId: "github-light-default",
         }),
       );
@@ -513,7 +520,15 @@ describe("useExtensionReviewEvents", () => {
       ]);
       expect(secondSeen.slice(3)).toEqual([
         { event: "filter_changed", payload: { filter: "test/" } },
-        { event: "layout_changed", payload: { mode: "auto", layout: "split" } },
+        {
+          event: "layout_changed",
+          payload: {
+            mode: "auto",
+            layout: "split",
+            canonicalMode: "auto",
+            canonicalLayout: "split",
+          },
+        },
         { event: "theme_changed", payload: { themeId: "github-dark-default" } },
       ]);
     } finally {
@@ -580,7 +595,7 @@ describe("useExtensionReviewEvents", () => {
     try {
       harness.current().publishNoteEvent("note_created", { note });
       harness.current().publishNoteEvent("note_edited", { note: { ...note, draft: true } });
-      harness.current().publishCommandExecuted("hunk.review.nextHunk");
+      harness.current().publishCommandExecuted("hunk.view.layoutStack", "hunk.view.layoutUnified");
 
       expect(seen.map(({ event }) => event)).toEqual([
         "note_created",
@@ -588,6 +603,10 @@ describe("useExtensionReviewEvents", () => {
         "command_executed",
       ]);
       expect(seen[0]?.payload).toEqual({ note });
+      expect(seen[2]?.payload).toEqual({
+        commandId: "hunk.view.layoutStack",
+        canonicalCommandId: "hunk.view.layoutUnified",
+      });
     } finally {
       await destroy(harness.setup);
     }
diff --git a/packages/hunk/src/ui/hooks/useExtensionReviewEvents.ts b/packages/hunk/src/ui/hooks/useExtensionReviewEvents.ts
index b3a451bb6..4e55bd5be 100644
--- a/packages/hunk/src/ui/hooks/useExtensionReviewEvents.ts
+++ b/packages/hunk/src/ui/hooks/useExtensionReviewEvents.ts
@@ -10,10 +10,9 @@
 import { useCallback, useEffect, useLayoutEffect, useRef } from "react";
 import { emitExtensionEvent } from "../../extensions/events";
 import { diffExtensionReviewNotes } from "../../extensions/reviewSnapshot";
+import type { LayoutMode } from "../../core/run/commandInputs";
 import type {
   ExtensionEventPayloads,
-  ExtensionLayoutMode,
-  ExtensionResolvedLayout,
   ExtensionReviewSnapshotNote,
 } from "../../extension-api/types";
 import type { ExtensionDiffFile, ExtensionLoadResult } from "../../extensions/types";
@@ -42,7 +41,7 @@ const defaultScheduler: ExtensionReviewEventScheduler = {
 };
 
 export interface ExtensionReviewEventPublishers {
-  publishCommandExecuted: (commandId: string) => void;
+  publishCommandExecuted: (commandId: string, canonicalCommandId?: string) => void;
   publishNoteEvent: <Event extends NoteEventName>(
     event: Event,
     payload: ExtensionEventPayloads[Event],
@@ -66,8 +65,8 @@ export function useExtensionReviewEvents({
 }: {
   extensions?: ExtensionLoadResult;
   filter: string;
-  layoutMode: ExtensionLayoutMode;
-  resolvedLayout: ExtensionResolvedLayout;
+  layoutMode: LayoutMode;
+  resolvedLayout: Exclude<LayoutMode, "auto">;
   reviewGeneration?: string;
   reviewNotes?: readonly ExtensionReviewSnapshotNote[];
   scheduler?: ExtensionReviewEventScheduler;
@@ -189,8 +188,10 @@ export function useExtensionReviewEvents({
     const reported = reportedLayoutRef.current;
     if (reported && reported.extensions === extensions && reported.value !== layoutSignature) {
       emitExtensionEvent(extensions, "layout_changed", {
-        mode: layoutMode,
-        layout: resolvedLayout,
+        mode: layoutMode === "unified" ? "stack" : layoutMode,
+        layout: resolvedLayout === "unified" ? "stack" : resolvedLayout,
+        canonicalMode: layoutMode,
+        canonicalLayout: resolvedLayout,
       });
     }
     reportedLayoutRef.current = { extensions, value: layoutSignature };
@@ -207,8 +208,11 @@ export function useExtensionReviewEvents({
   }, [extensions, themeId]);
 
   // Keep action publishers stable while resolving the current runtime at call time.
-  const publishCommandExecuted = useCallback((commandId: string) => {
-    emitExtensionEvent(activeExtensionsRef.current, "command_executed", { commandId });
+  const publishCommandExecuted = useCallback((commandId: string, canonicalCommandId?: string) => {
+    emitExtensionEvent(activeExtensionsRef.current, "command_executed", {
+      commandId,
+      ...(canonicalCommandId ? { canonicalCommandId } : {}),
+    });
   }, []);
 
   const publishNoteEvent = useCallback(
diff --git a/packages/hunk/src/ui/hooks/useExtensionRuntimeBridge.test.tsx b/packages/hunk/src/ui/hooks/useExtensionRuntimeBridge.test.tsx
index d6f4708f6..b6d548699 100644
--- a/packages/hunk/src/ui/hooks/useExtensionRuntimeBridge.test.tsx
+++ b/packages/hunk/src/ui/hooks/useExtensionRuntimeBridge.test.tsx
@@ -112,7 +112,7 @@ function createBootstrap(id: string): AppBootstrap {
   return createTestVcsAppBootstrap({
     changesetId: id,
     files: [createTestDiffFile({ id: "alpha", path: "alpha.ts" })],
-    initialMode: "stack",
+    initialMode: "unified",
   });
 }
 
diff --git a/packages/hunk/src/ui/hooks/useTerminalReview.test.tsx b/packages/hunk/src/ui/hooks/useTerminalReview.test.tsx
index 016bee4a7..a6909c1f8 100644
--- a/packages/hunk/src/ui/hooks/useTerminalReview.test.tsx
+++ b/packages/hunk/src/ui/hooks/useTerminalReview.test.tsx
@@ -196,7 +196,7 @@ function TerminalReviewHarness({
         visibleFiles.map((file) =>
           measureDiffSectionGeometry(
             file,
-            "stack",
+            "unified",
             true,
             resolveTheme("github-dark-default", null),
             [],
@@ -537,8 +537,8 @@ describe("useTerminalReview", () => {
   });
 
   test("live comments validate markup at the published live width", async () => {
-    const noteGeometry: { current: { layout: "split" | "stack"; width: number } | null } = {
-      current: { layout: "stack", width: 120 },
+    const noteGeometry: { current: { layout: "split" | "unified"; width: number } | null } = {
+      current: { layout: "unified", width: 120 },
     };
     const { controllerRef, setup } = await renderTerminalReview(
       [
@@ -587,7 +587,7 @@ describe("useTerminalReview", () => {
         );
       });
 
-      // stack at width 120 → content width 112; split dock is roughly half.
+      // unified at width 120 → content width 112; split dock is roughly half.
       expect(results[0]!.markupWidth).toBe(112);
       expect(results[1]!.markupWidth).toBeLessThan(70);
     } finally {
@@ -1881,7 +1881,7 @@ describe("useTerminalReview", () => {
       [
         measureDiffSectionGeometry(
           file,
-          "stack",
+          "unified",
           true,
           resolveTheme("github-dark-default", null),
           [],
diff --git a/packages/hunk/src/ui/lib/agentNoteGeometry.test.ts b/packages/hunk/src/ui/lib/agentNoteGeometry.test.ts
index 50b3f18cd..10e31fd27 100644
--- a/packages/hunk/src/ui/lib/agentNoteGeometry.test.ts
+++ b/packages/hunk/src/ui/lib/agentNoteGeometry.test.ts
@@ -2,10 +2,10 @@ import { describe, expect, test } from "bun:test";
 import { agentNoteBoxLayout, agentNoteMarkupWidth } from "./agentNoteGeometry";
 
 describe("agentNoteBoxLayout", () => {
-  test("stack layout gives the note nearly the full pane", () => {
+  test("unified layout gives the note nearly the full pane", () => {
     const { boxWidth, contentWidth } = agentNoteBoxLayout({
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 120,
     });
     expect(boxWidth).toBe(116);
@@ -35,7 +35,7 @@ describe("agentNoteBoxLayout", () => {
   test("never collapses below the minimum card width", () => {
     const { boxWidth, contentWidth } = agentNoteBoxLayout({
       anchorSide: "new",
-      layout: "stack",
+      layout: "unified",
       width: 20,
     });
     expect(boxWidth).toBeGreaterThanOrEqual(16);
@@ -43,7 +43,7 @@ describe("agentNoteBoxLayout", () => {
   });
 
   test("huge terminals grow the markup width with the pane", () => {
-    expect(agentNoteMarkupWidth({ anchorSide: "new", layout: "stack", width: 220 })).toBe(212);
+    expect(agentNoteMarkupWidth({ anchorSide: "new", layout: "unified", width: 220 })).toBe(212);
     expect(
       agentNoteMarkupWidth({ anchorSide: "new", layout: "split", width: 220 }),
     ).toBeGreaterThan(100);
diff --git a/packages/hunk/src/ui/lib/appCommands.test.ts b/packages/hunk/src/ui/lib/appCommands.test.ts
index 5a30ad26d..4dc84f8b1 100644
--- a/packages/hunk/src/ui/lib/appCommands.test.ts
+++ b/packages/hunk/src/ui/lib/appCommands.test.ts
@@ -332,11 +332,12 @@ describe("executeAppCommand", () => {
     expect(ran).toEqual(["requestQuit", "openAgentSkill"]);
   });
 
-  test("executes a compatibility alias through the canonical command", () => {
+  test("executes compatibility aliases through their canonical commands", () => {
     const { commands, ran } = createTestCommands();
 
     expect(executeAppCommand(commands, "hunk.view.toggleSidebar")).toBe(true);
-    expect(ran).toEqual(["toggleFilesPane"]);
+    expect(executeAppCommand(commands, "hunk.view.layoutStack")).toBe(true);
+    expect(ran).toEqual(["toggleFilesPane", "selectLayoutMode:unified"]);
   });
 
   test("uses shipped semantics rather than a remapped chord for programmatic execution", () => {
@@ -384,14 +385,20 @@ describe("executeAppCommand", () => {
 });
 
 describe("observeAppCommandDispatch", () => {
-  test("observes successful terminal dispatch exactly once with the command id", () => {
+  test("observes successful terminal dispatch with stable and canonical command ids", () => {
     const { commands, ran } = createTestCommands();
-    const observed: string[] = [];
-    const wrapped = observeAppCommandDispatch(commands, (id) => observed.push(id));
+    const observed: Array<[string, string | undefined]> = [];
+    const wrapped = observeAppCommandDispatch(commands, (id, canonicalId) =>
+      observed.push([id, canonicalId]),
+    );
 
     expect(dispatchAppCommand(wrapped, keyEvent({ name: "q" }))?.id).toBe("hunk.app.quit");
-    expect(ran).toEqual(["requestQuit"]);
-    expect(observed).toEqual(["hunk.app.quit"]);
+    expect(executeAppCommand(wrapped, "hunk.view.layoutStack")).toBe(true);
+    expect(ran).toEqual(["requestQuit", "selectLayoutMode:unified"]);
+    expect(observed).toEqual([
+      ["hunk.app.quit", undefined],
+      ["hunk.view.layoutStack", "hunk.view.layoutUnified"],
+    ]);
   });
 
   test("does not observe disabled or throwing commands", () => {
diff --git a/packages/hunk/src/ui/lib/appCommands.ts b/packages/hunk/src/ui/lib/appCommands.ts
index 51f1f046c..7c2aa5e27 100644
--- a/packages/hunk/src/ui/lib/appCommands.ts
+++ b/packages/hunk/src/ui/lib/appCommands.ts
@@ -85,7 +85,7 @@ export interface AppCommand {
  */
 export function observeAppCommandDispatch(
   commands: readonly AppCommand[],
-  onDispatched: (commandId: string) => void,
+  onDispatched: (commandId: string, canonicalCommandId?: string) => void,
 ): AppCommand[] {
   return commands.map((command) => ({
     ...command,
@@ -93,7 +93,11 @@ export function observeAppCommandDispatch(
       command.run(key, count);
       // AppCommand is deliberately synchronous. Extension handlers may have
       // detached async work still running after terminal dispatch returns.
-      onDispatched(command.id);
+      if (command.id === "hunk.view.layoutUnified") {
+        onDispatched("hunk.view.layoutStack", command.id);
+      } else {
+        onDispatched(command.id);
+      }
     },
   }));
 }
@@ -238,7 +242,7 @@ function builtinCommandHandlers(
     "hunk.view.cursorLineNumber": { run: () => options.selectCursorLine("number") },
     "hunk.view.cursorLineOff": { run: () => options.selectCursorLine("off") },
     "hunk.view.layoutSplit": { run: () => options.selectLayoutMode("split") },
-    "hunk.view.layoutStack": { run: () => options.selectLayoutMode("stack") },
+    "hunk.view.layoutUnified": { run: () => options.selectLayoutMode("unified") },
     "hunk.view.layoutAuto": { run: () => options.selectLayoutMode("auto") },
     "hunk.view.applyFilePresentationToAllMatching": {
       isEnabled: () => options.canApplyFilePresentationToAllMatching,
diff --git a/packages/hunk/src/ui/lib/appMenus.test.ts b/packages/hunk/src/ui/lib/appMenus.test.ts
index 98164ea38..c3532ab57 100644
--- a/packages/hunk/src/ui/lib/appMenus.test.ts
+++ b/packages/hunk/src/ui/lib/appMenus.test.ts
@@ -17,7 +17,7 @@ import { resolveCommandKeys } from "./keymap";
 const MENU_STATE: Omit<BuildAppMenusOptions, "commands" | "extensionCommands"> = {
   copyDecorations: true,
   cursorLine: "row" as const,
-  layoutMode: "stack",
+  layoutMode: "unified",
   filesPaneVisible: false,
   showAgentNotes: true,
   showHelp: false,
@@ -132,7 +132,7 @@ describe("buildAppMenus", () => {
         .filter((item) => item.checked)
         .map((item) => item.label),
     ).toEqual([
-      "Stacked view",
+      "Unified view",
       "Menu bar",
       "Agent notes",
       "Line numbers",
diff --git a/packages/hunk/src/ui/lib/appMenus.ts b/packages/hunk/src/ui/lib/appMenus.ts
index 6a48df299..dfe2004b5 100644
--- a/packages/hunk/src/ui/lib/appMenus.ts
+++ b/packages/hunk/src/ui/lib/appMenus.ts
@@ -149,9 +149,9 @@ export function buildAppMenus({
     view: [
       { commandId: "hunk.view.layoutSplit", label: "Split view", checked: layoutMode === "split" },
       {
-        commandId: "hunk.view.layoutStack",
-        label: "Stacked view",
-        checked: layoutMode === "stack",
+        commandId: "hunk.view.layoutUnified",
+        label: "Unified view",
+        checked: layoutMode === "unified",
       },
       { commandId: "hunk.view.layoutAuto", checked: layoutMode === "auto" },
       SEPARATOR,
diff --git a/packages/hunk/src/ui/lib/extensionCurrentLine.tsx b/packages/hunk/src/ui/lib/extensionCurrentLine.tsx
index bf73db650..bbc98c7a7 100644
--- a/packages/hunk/src/ui/lib/extensionCurrentLine.tsx
+++ b/packages/hunk/src/ui/lib/extensionCurrentLine.tsx
@@ -1,12 +1,12 @@
 import type { ExtensionCurrentLinePaint } from "../../extension-api/types";
-import type { DiffRow, SplitLineCell, StackLineCell } from "../diff/diffRows";
+import type { DiffRow, SplitLineCell, UnifiedLineCell } from "../diff/diffRows";
 import { RawDiffRowView } from "../diff/RawDiffRowView";
 import type { DiffSectionRowPlan } from "../diff/diffSectionRowPlan";
 import type { LineCursor } from "./lineCursors";
 import type { AppTheme } from "../themes";
 
 type SplitLineRow = Extract<DiffRow, { type: "split-line" }>;
-type StackLineRow = Extract<DiffRow, { type: "stack-line" }>;
+type UnifiedLineRow = Extract<DiffRow, { type: "unified-line" }>;
 
 /** One lifecycle update from the review renderer to pane orchestration. */
 export type ExtensionCurrentLinePaintUpdate =
@@ -52,8 +52,8 @@ export function applyExtensionCurrentLinePaintUpdate(
 }
 
 /** Adapt one private split cell into the private full-width row painter. */
-function stackRow(row: SplitLineRow, cell: SplitLineCell, side: "old" | "new"): StackLineRow {
-  const adapted: StackLineCell = {
+function unifiedRow(row: SplitLineRow, cell: SplitLineCell, side: "old" | "new"): UnifiedLineRow {
+  const adapted: UnifiedLineCell = {
     kind: cell.kind === "empty" ? "context" : cell.kind,
     sign: cell.kind === "empty" ? " " : cell.sign,
     ...(side === "old" ? { oldLineNumber: cell.lineNumber } : { newLineNumber: cell.lineNumber }),
@@ -61,7 +61,7 @@ function stackRow(row: SplitLineRow, cell: SplitLineCell, side: "old" | "new"):
     spans: cell.spans,
   };
   return {
-    type: "stack-line",
+    type: "unified-line",
     key: `${row.key}:pane:${side}`,
     fileId: row.fileId,
     hunkIndex: row.hunkIndex,
@@ -96,8 +96,8 @@ export function createExtensionCurrentLinePaint({
   }
   if (!splitRow) return null;
   const rows = {
-    old: stackRow(splitRow, splitRow.left, "old"),
-    new: stackRow(splitRow, splitRow.right, "new"),
+    old: unifiedRow(splitRow, splitRow.left, "old"),
+    new: unifiedRow(splitRow, splitRow.right, "new"),
   };
   return Object.freeze({
     side: cursor.target.side,
diff --git a/packages/hunk/src/ui/lib/helpContent.test.ts b/packages/hunk/src/ui/lib/helpContent.test.ts
index 1666a41cc..f0f15d246 100644
--- a/packages/hunk/src/ui/lib/helpContent.test.ts
+++ b/packages/hunk/src/ui/lib/helpContent.test.ts
@@ -32,7 +32,7 @@ describe("buildHelpSections", () => {
     expect(keysFor(sections, "previous / next hunk")).toBe("[ / ]");
     expect(keysFor(sections, "half page down / up")).toBe("d / u");
     expect(keysFor(sections, "move line-by-line")).toBe("Up / Down");
-    expect(keysFor(sections, "split / stack / auto")).toBe("1 / 2 / 0");
+    expect(keysFor(sections, "split / unified / auto")).toBe("1 / 2 / 0");
     expect(keysFor(sections, "lines / wrap / metadata / menu")).toBe("l / w / m / M");
   });
 
diff --git a/packages/hunk/src/ui/lib/helpContent.ts b/packages/hunk/src/ui/lib/helpContent.ts
index 0bb8ae799..34ecd9918 100644
--- a/packages/hunk/src/ui/lib/helpContent.ts
+++ b/packages/hunk/src/ui/lib/helpContent.ts
@@ -81,8 +81,8 @@ const HELP_SECTIONS: readonly HelpSectionSpec[] = [
     title: "View",
     entries: [
       {
-        commandIds: ["hunk.view.layoutSplit", "hunk.view.layoutStack", "hunk.view.layoutAuto"],
-        description: "split / stack / auto",
+        commandIds: ["hunk.view.layoutSplit", "hunk.view.layoutUnified", "hunk.view.layoutAuto"],
+        description: "split / unified / auto",
       },
       {
         commandIds: ["hunk.view.toggleFilesPane", "hunk.view.openThemeSelector"],
diff --git a/packages/hunk/src/ui/lib/keymap.test.ts b/packages/hunk/src/ui/lib/keymap.test.ts
index 7e09b6599..75f7d45e0 100644
--- a/packages/hunk/src/ui/lib/keymap.test.ts
+++ b/packages/hunk/src/ui/lib/keymap.test.ts
@@ -15,6 +15,11 @@ const DEFAULTS: CommandKeyDefaults[] = [
     aliases: ["hunk.view.toggleSidebar"],
     defaultKeys: ["s"],
   },
+  {
+    id: "hunk.view.layoutUnified",
+    aliases: ["hunk.view.layoutStack"],
+    defaultKeys: ["2"],
+  },
   // A loaded extension's command, under that extension's own id.
   { id: "meta.toggle", defaultKeys: ["y"] },
 ];
@@ -54,6 +59,14 @@ describe("resolveCommandKeys", () => {
     expect(keys.get("hunk.view.toggleSidebar")).toEqual(["ctrl+b"]);
   });
 
+  test("the deprecated layout alias remaps the canonical unified command", () => {
+    const { keys, issues } = resolve({ "hunk.view.layoutStack": "ctrl+2" });
+
+    expect(issues).toEqual([]);
+    expect(keys.get("hunk.view.layoutUnified")).toEqual(["ctrl+2"]);
+    expect(keys.get("hunk.view.layoutStack")).toEqual(["ctrl+2"]);
+  });
+
   test("the first config entry wins when an alias and canonical id both appear", () => {
     const { keys, issues } = resolve({
       "hunk.view.toggleSidebar": "ctrl+b",
diff --git a/packages/hunk/src/ui/lib/lineCursors.test.ts b/packages/hunk/src/ui/lib/lineCursors.test.ts
index 53c08ecc2..53ecba141 100644
--- a/packages/hunk/src/ui/lib/lineCursors.test.ts
+++ b/packages/hunk/src/ui/lib/lineCursors.test.ts
@@ -67,7 +67,7 @@ function createCollapsedGapFile() {
 
 describe("buildLineCursors", () => {
   test("walks context and changed lines in rendered order", () => {
-    const cursors = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "stack");
+    const cursors = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "unified");
 
     expect(cursors).toEqual([
       {
@@ -98,7 +98,7 @@ describe("buildLineCursors", () => {
   });
 
   test("keeps old and new line numbering independent across hunks", () => {
-    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "stack");
+    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "unified");
 
     expect(cursors.map((cursor) => ({ hunkIndex: cursor.hunkIndex, ...cursor.target }))).toEqual([
       { hunkIndex: 0, side: "old", line: 1 },
@@ -127,7 +127,7 @@ describe("buildLineCursors", () => {
     ]);
   });
 
-  test("walks a change block one column at a time in stack layout", () => {
+  test("walks a change block one column at a time in unified layout", () => {
     const file = createTestDiffFile({
       id: "alpha",
       path: "alpha.ts",
@@ -136,7 +136,7 @@ describe("buildLineCursors", () => {
       context: 0,
     });
 
-    expect(cursorsFor([file], "stack").map((cursor) => cursor.target)).toEqual([
+    expect(cursorsFor([file], "unified").map((cursor) => cursor.target)).toEqual([
       { side: "old", line: 1 },
       { side: "old", line: 2 },
       { side: "old", line: 3 },
@@ -149,10 +149,10 @@ describe("buildLineCursors", () => {
   test("stops on the lines an expanded gap reveals", () => {
     const file = createCollapsedGapFile();
     const source = lines("one", "two", "three", "four", "five", "SIX");
-    const collapsed = measureDiffSectionGeometry(file, "stack", true, theme);
+    const collapsed = measureDiffSectionGeometry(file, "unified", true, theme);
     const expanded = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       true,
       theme,
       [],
@@ -176,7 +176,7 @@ describe("buildLineCursors", () => {
   test("flattens every visible file into one review stream", () => {
     const cursors = cursorsFor(
       [createTwoHunkFile("alpha", "alpha.ts"), createTwoHunkFile("beta", "beta.ts")],
-      "stack",
+      "unified",
     );
 
     expect(cursors).toHaveLength(8);
@@ -186,7 +186,7 @@ describe("buildLineCursors", () => {
 
   test("gives no stops to a file the stream renders no source lines for", () => {
     const empty = createTestHeaderOnlyDiffFile();
-    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts"), empty], "stack");
+    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts"), empty], "unified");
 
     expect(cursors.some((cursor) => cursor.fileId === "alpha")).toBe(true);
     expect(cursors.some((cursor) => cursor.fileId === empty.id)).toBe(false);
@@ -200,14 +200,14 @@ describe("buildLineCursors", () => {
 
 describe("reuseEquivalentLineCursors", () => {
   test("keeps list identity when remeasurement preserves every cursor", () => {
-    const previous = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "stack");
+    const previous = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "unified");
     const next = previous.map((cursor) => ({ ...cursor, target: { ...cursor.target } }));
 
     expect(reuseEquivalentLineCursors(previous, next)).toBe(previous);
   });
 
   test("keeps a changed cursor list", () => {
-    const previous = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "stack");
+    const previous = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "unified");
     const next = previous.map((cursor, index) =>
       index === 0
         ? { ...cursor, target: { ...cursor.target, line: cursor.target.line + 1 } }
@@ -221,7 +221,7 @@ describe("reuseEquivalentLineCursors", () => {
 describe("createLineCursorStabilizer", () => {
   test("does not rescan an unchanged measurement during unrelated renders", () => {
     const stabilize = createLineCursorStabilizer();
-    const measured = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "stack");
+    const measured = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "unified");
 
     expect(stabilize(measured)).toBe(measured);
     expect(stabilize(measured)).toBe(measured);
@@ -229,7 +229,7 @@ describe("createLineCursorStabilizer", () => {
 
   test("preserves stable cursor identity across equivalent remeasurement", () => {
     const stabilize = createLineCursorStabilizer();
-    const stable = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "stack");
+    const stable = cursorsFor([createContextWrappedFile("alpha", "alpha.ts")], "unified");
     const measured = stable.map((cursor) => ({ ...cursor, target: { ...cursor.target } }));
 
     expect(stabilize(stable)).toBe(stable);
@@ -250,7 +250,7 @@ describe("findLineCursorAt", () => {
   }
 
   test("finds a changed line by the side the patch numbers it on", () => {
-    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "stack");
+    const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "unified");
 
     expect(findLineCursorAt(cursors, "alpha", "new", 10)?.target).toEqual({
       side: "new",
@@ -264,7 +264,7 @@ describe("findLineCursorAt", () => {
 
   test("answers a context row to either side's number, even once they diverge", () => {
     // "three" is old line 3 and new line 4 after the insertion; both address the same row.
-    const cursors = cursorsFor([createShiftedContextFile()], "stack");
+    const cursors = cursorsFor([createShiftedContextFile()], "unified");
     const byNew = findLineCursorAt(cursors, "alpha", "new", 4);
     const byOld = findLineCursorAt(cursors, "alpha", "old", 3);
 
@@ -275,7 +275,7 @@ describe("findLineCursorAt", () => {
   test("stays inside the requested file when two files number the same line", () => {
     const cursors = cursorsFor(
       [createTwoHunkFile("alpha", "alpha.ts"), createTwoHunkFile("beta", "beta.ts")],
-      "stack",
+      "unified",
     );
 
     expect(findLineCursorAt(cursors, "beta", "new", 1)?.fileId).toBe("beta");
@@ -283,7 +283,7 @@ describe("findLineCursorAt", () => {
 
   test("finds no cursor for a line the stream draws no row for", () => {
     // Line 3 is inside the collapsed gap above the only hunk, so nothing measures it.
-    const cursors = cursorsFor([createCollapsedGapFile()], "stack");
+    const cursors = cursorsFor([createCollapsedGapFile()], "unified");
 
     expect(findLineCursorAt(cursors, "alpha", "new", 3)).toBeNull();
     expect(findLineCursorAt(cursors, "alpha", "new", 900)).toBeNull();
@@ -294,7 +294,7 @@ describe("findLineCursorAt", () => {
 describe("findNextLineCursor", () => {
   const cursors = cursorsFor(
     [createTwoHunkFile("alpha", "alpha.ts"), createTwoHunkFile("beta", "beta.ts")],
-    "stack",
+    "unified",
   );
 
   test("steps forward and backward one line at a time", () => {
@@ -339,7 +339,7 @@ describe("findNextLineCursor", () => {
 describe("firstLineCursorInHunk", () => {
   const cursors = cursorsFor(
     [createTwoHunkFile("alpha", "alpha.ts"), createTwoHunkFile("beta", "beta.ts")],
-    "stack",
+    "unified",
   );
 
   test("seeds at the first line of the requested hunk", () => {
@@ -369,7 +369,7 @@ describe("firstLineCursorInHunk", () => {
 });
 
 describe("resolveLineCursor", () => {
-  const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "stack");
+  const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "unified");
 
   test("keeps a cursor that still points at a real line", () => {
     expect(resolveLineCursor(cursors, cursors[2]!)).toEqual(cursors[2]!);
@@ -419,7 +419,7 @@ describe("resolveLineCursor", () => {
 });
 
 describe("clampLineCursorToViewport", () => {
-  const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "stack");
+  const cursors = cursorsFor([createTwoHunkFile("alpha", "alpha.ts")], "unified");
   const boundsOf = (cursor: LineCursor) => {
     const index = cursors.findIndex((candidate) => candidate.stableKey === cursor.stableKey);
     return index < 0 ? undefined : { top: index, height: 1 };
diff --git a/packages/hunk/src/ui/lib/responsive.test.ts b/packages/hunk/src/ui/lib/responsive.test.ts
index 652b6d46d..928fd204c 100644
--- a/packages/hunk/src/ui/lib/responsive.test.ts
+++ b/packages/hunk/src/ui/lib/responsive.test.ts
@@ -8,10 +8,10 @@ const MEDIUM_WIDTH = 180;
 const FULL_WIDTH = 240;
 
 describe("resolveResponsiveLayout — auto", () => {
-  test("chooses stack with no sidebar on tight terminals", () => {
+  test("chooses unified with no sidebar on tight terminals", () => {
     expect(resolveResponsiveLayout("auto", TIGHT_WIDTH)).toEqual({
       viewport: "tight",
-      layout: "stack",
+      layout: "unified",
       showSidebar: false,
     });
   });
@@ -50,17 +50,17 @@ describe("resolveResponsiveLayout — explicit overrides", () => {
     });
   });
 
-  test("keeps stack even on a full-width terminal and still shows the sidebar there", () => {
-    expect(resolveResponsiveLayout("stack", FULL_WIDTH)).toEqual({
+  test("keeps unified even on a full-width terminal and still shows the sidebar there", () => {
+    expect(resolveResponsiveLayout("unified", FULL_WIDTH)).toEqual({
       viewport: "full",
-      layout: "stack",
+      layout: "unified",
       showSidebar: true,
     });
   });
 
   test("shows the sidebar at medium and full widths for explicit modes", () => {
     expect(resolveResponsiveLayout("split", MEDIUM_WIDTH).showSidebar).toBe(true);
-    expect(resolveResponsiveLayout("stack", MEDIUM_WIDTH).showSidebar).toBe(true);
+    expect(resolveResponsiveLayout("unified", MEDIUM_WIDTH).showSidebar).toBe(true);
     expect(resolveResponsiveLayout("split", FULL_WIDTH).showSidebar).toBe(true);
   });
 });
@@ -85,9 +85,9 @@ describe("resolveResponsiveLayout — viewport bucket boundaries", () => {
     });
   });
 
-  test("auto switches from stack to split at its narrower independent cutoff", () => {
+  test("auto switches from unified to split at its narrower independent cutoff", () => {
     expect(resolveResponsiveLayout("auto", 119)).toMatchObject({
-      layout: "stack",
+      layout: "unified",
       showSidebar: false,
     });
     expect(resolveResponsiveLayout("auto", 120)).toMatchObject({
diff --git a/packages/hunk/src/ui/lib/responsive.ts b/packages/hunk/src/ui/lib/responsive.ts
index 1dfd29d7e..f63ac25ad 100644
--- a/packages/hunk/src/ui/lib/responsive.ts
+++ b/packages/hunk/src/ui/lib/responsive.ts
@@ -41,17 +41,17 @@ export function resolveResponsiveLayout(
     };
   }
 
-  if (requestedLayout === "stack") {
+  if (requestedLayout === "unified") {
     return {
       viewport,
-      layout: "stack",
+      layout: "unified",
       showSidebar: viewport !== "tight",
     };
   }
 
   return {
     viewport,
-    layout: viewportWidth >= AUTO_SPLIT_MIN_WIDTH ? "split" : "stack",
+    layout: viewportWidth >= AUTO_SPLIT_MIN_WIDTH ? "split" : "unified",
     showSidebar: viewport !== "tight",
   };
 }
diff --git a/packages/hunk/src/ui/lib/stml/guide.ts b/packages/hunk/src/ui/lib/stml/guide.ts
index 4ec3b5acb..44f1c8a2f 100644
--- a/packages/hunk/src/ui/lib/stml/guide.ts
+++ b/packages/hunk/src/ui/lib/stml/guide.ts
@@ -34,7 +34,7 @@ Preview from a file or stdin:
   that frame around the whole body. Sibling and nested boxes are supported.
 - Confirm \`hunk session context --json\` lists \`stml\` in
   \`experimentalFeatures\` before authoring markup. Width follows the live
-  session: stack ≈ full pane, split ≈ half. The context reports
+  session: unified ≈ full pane, split ≈ half. The context reports
   \`noteMarkupWidth\`; comment responses echo \`markupWidth\`. Preview with
   \`hunk markup render - --width <that>\`. Unknown? Design for ~${STML_REFERENCE_WIDTH} cols —
   it holds up wider, and users resize/switch layouts anytime.
diff --git a/packages/hunk/src/ui/lib/ui-lib.test.ts b/packages/hunk/src/ui/lib/ui-lib.test.ts
index 2dff5ff13..657183955 100644
--- a/packages/hunk/src/ui/lib/ui-lib.test.ts
+++ b/packages/hunk/src/ui/lib/ui-lib.test.ts
@@ -487,12 +487,12 @@ describe("ui helpers", () => {
     expect(resizeSidebarWidth(34, 33, 120, 22, 80)).toBe(80);
   });
 
-  test("estimateDiffSectionBodyRows matches split and stack row counts from the render plan", async () => {
+  test("estimateDiffSectionBodyRows matches split and unified row counts from the render plan", async () => {
     const file = createDiffFile();
     const theme = resolveTheme("github-dark-default", null);
 
     expect(estimateDiffSectionBodyRows(file, "split", true, theme)).toBeGreaterThan(0);
-    expect(estimateDiffSectionBodyRows(file, "stack", true, theme)).toBeGreaterThan(
+    expect(estimateDiffSectionBodyRows(file, "unified", true, theme)).toBeGreaterThan(
       estimateDiffSectionBodyRows(file, "split", true, theme),
     );
     expect(estimateDiffSectionBodyRows(file, "split", false, theme)).toBe(
diff --git a/packages/hunk/src/ui/lib/viewportAnchor.test.ts b/packages/hunk/src/ui/lib/viewportAnchor.test.ts
index 3b606f609..476b04b03 100644
--- a/packages/hunk/src/ui/lib/viewportAnchor.test.ts
+++ b/packages/hunk/src/ui/lib/viewportAnchor.test.ts
@@ -17,7 +17,7 @@ describe("viewport row anchors", () => {
     });
   }
 
-  test("honors a preferred stable key when a split change row can map to multiple stacked rows", () => {
+  test("honors a preferred stable key when a split change row can map to multiple unified rows", () => {
     const file = createChangedFile();
     const headerHeights = buildInStreamFileHeaderHeights([file]);
     const splitGeometry = measureDiffSectionGeometry(
@@ -30,9 +30,9 @@ describe("viewport row anchors", () => {
       true,
       false,
     );
-    const stackGeometry = measureDiffSectionGeometry(
+    const unifiedGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       false,
       theme,
       [],
@@ -41,27 +41,27 @@ describe("viewport row anchors", () => {
       false,
     );
     const splitChangeTop = splitGeometry.rowBounds.find((row) => row.key.includes(":change:"))?.top;
-    const stackDeletionTop = stackGeometry.rowBounds.find((row) =>
+    const unifiedDeletionTop = unifiedGeometry.rowBounds.find((row) =>
       row.key.includes(":deletion:"),
     )?.top;
-    const stackAdditionTop = stackGeometry.rowBounds.find((row) =>
+    const unifiedAdditionTop = unifiedGeometry.rowBounds.find((row) =>
       row.key.includes(":addition:"),
     )?.top;
 
     expect(splitChangeTop).toBeDefined();
-    expect(stackDeletionTop).toBeDefined();
-    expect(stackAdditionTop).toBeDefined();
+    expect(unifiedDeletionTop).toBeDefined();
+    expect(unifiedAdditionTop).toBeDefined();
 
     const deletionAnchor = findViewportRowAnchor(
       [file],
-      [stackGeometry],
-      stackDeletionTop!,
+      [unifiedGeometry],
+      unifiedDeletionTop!,
       headerHeights,
     );
     const additionAnchor = findViewportRowAnchor(
       [file],
-      [stackGeometry],
-      stackAdditionTop!,
+      [unifiedGeometry],
+      unifiedAdditionTop!,
       headerHeights,
     );
 
@@ -84,7 +84,7 @@ describe("viewport row anchors", () => {
     expect(splitAsAddition?.stableKey).toBe(additionAnchor?.stableKey);
   });
 
-  test("round-trips a stacked deletion row through split view without changing the viewport anchor", () => {
+  test("round-trips a unified deletion row through split view without changing the viewport anchor", () => {
     const file = createChangedFile();
     const headerHeights = buildInStreamFileHeaderHeights([file]);
     const splitGeometry = measureDiffSectionGeometry(
@@ -97,9 +97,9 @@ describe("viewport row anchors", () => {
       true,
       false,
     );
-    const stackGeometry = measureDiffSectionGeometry(
+    const unifiedGeometry = measureDiffSectionGeometry(
       file,
-      "stack",
+      "unified",
       false,
       theme,
       [],
@@ -107,25 +107,25 @@ describe("viewport row anchors", () => {
       true,
       false,
     );
-    const stackDeletionTop = stackGeometry.rowBounds.find((row) =>
+    const unifiedDeletionTop = unifiedGeometry.rowBounds.find((row) =>
       row.key.includes(":deletion:"),
     )?.top;
 
-    expect(stackDeletionTop).toBeDefined();
+    expect(unifiedDeletionTop).toBeDefined();
 
-    const stackDeletionAnchor = findViewportRowAnchor(
+    const unifiedDeletionAnchor = findViewportRowAnchor(
       [file],
-      [stackGeometry],
-      stackDeletionTop!,
+      [unifiedGeometry],
+      unifiedDeletionTop!,
       headerHeights,
     );
 
-    expect(stackDeletionAnchor).not.toBeNull();
+    expect(unifiedDeletionAnchor).not.toBeNull();
 
     const splitTop = resolveViewportRowAnchorTop(
       [file],
       [splitGeometry],
-      stackDeletionAnchor!,
+      unifiedDeletionAnchor!,
       headerHeights,
     );
     const splitAnchor = findViewportRowAnchor(
@@ -133,15 +133,15 @@ describe("viewport row anchors", () => {
       [splitGeometry],
       splitTop,
       headerHeights,
-      stackDeletionAnchor?.stableKey,
+      unifiedDeletionAnchor?.stableKey,
     );
     const roundTripTop = resolveViewportRowAnchorTop(
       [file],
-      [stackGeometry],
+      [unifiedGeometry],
       splitAnchor!,
       headerHeights,
     );
 
-    expect(roundTripTop).toBe(stackDeletionTop!);
+    expect(roundTripTop).toBe(unifiedDeletionTop!);
   });
 });
diff --git a/packages/hunk/src/ui/lib/viewportAnchor.ts b/packages/hunk/src/ui/lib/viewportAnchor.ts
index 89656a7dd..48f82bfba 100644
--- a/packages/hunk/src/ui/lib/viewportAnchor.ts
+++ b/packages/hunk/src/ui/lib/viewportAnchor.ts
@@ -36,7 +36,7 @@ function binarySearchRowBounds(sectionRowBounds: DiffSectionRowBounds[], relativ
  * Capture a stable top-row anchor from the current review stream.
  *
  * `preferredStableKey` lets callers preserve the exact logical side they were already following
- * when a split row can map to multiple stacked rows and vice versa.
+ * when a split row can map to multiple unified rows and vice versa.
  */
 export function findViewportRowAnchor(
   files: DiffFile[],
diff --git a/packages/hunk/src/ui/staticDiffPager.test.ts b/packages/hunk/src/ui/staticDiffPager.test.ts
index 49fe31a7e..cce346b4c 100644
--- a/packages/hunk/src/ui/staticDiffPager.test.ts
+++ b/packages/hunk/src/ui/staticDiffPager.test.ts
@@ -115,7 +115,7 @@ describe("static diff pager", () => {
     expect(output.length).toBeLessThan(50_000);
   });
 
-  test("keeps auto mode stacked in static pager output", async () => {
+  test("keeps auto mode unified in static pager output", async () => {
     const patchText =
       "diff --git a/a.ts b/a.ts\n--- a/a.ts\n+++ b/a.ts\n@@ -1 +1 @@\n-const value = 1;\n+const value = 2;\n";
 
@@ -131,7 +131,7 @@ describe("static diff pager", () => {
     expect(plain).toContain("▌  1 +  const value = 2;");
   });
 
-  test("extends stacked row backgrounds to the host panel edge", async () => {
+  test("extends unified row backgrounds to the host panel edge", async () => {
     const patchText =
       "diff --git a/a.ts b/a.ts\n--- a/a.ts\n+++ b/a.ts\n@@ -1 +1 @@\n-short\n+also short\n";
 
diff --git a/packages/hunk/src/ui/staticDiffPager.ts b/packages/hunk/src/ui/staticDiffPager.ts
index 3a60fdc20..8c0a563ce 100644
--- a/packages/hunk/src/ui/staticDiffPager.ts
+++ b/packages/hunk/src/ui/staticDiffPager.ts
@@ -23,7 +23,7 @@ import type { CommonOptions } from "../core/run/commandInputs";
 import type { NamedCustomThemeConfig } from "../extension-api/types";
 import {
   buildSplitRows,
-  buildStackRows,
+  buildUnifiedRows,
   loadHighlightedDiff,
   type DiffRow,
   type RenderSpan,
@@ -37,9 +37,9 @@ import {
   splitGutterText,
   splitLeftRailColor,
   splitRightRailColor,
-  stackCellPalette,
-  stackGutterText,
-  stackRailColor,
+  unifiedCellPalette,
+  unifiedGutterText,
+  unifiedRailColor,
 } from "./diff/rowStyle";
 import { measureTextWidth, sliceTextByWidth } from "./lib/text";
 import {
@@ -132,12 +132,12 @@ function fixedWidthText(text: string, width: number) {
   return `${visible.text}${" ".repeat(Math.max(0, width - visible.width))}`;
 }
 
-function staticStackGutterText(
-  cell: Extract<DiffRow, { type: "stack-line" }>["cell"],
+function staticUnifiedGutterText(
+  cell: Extract<DiffRow, { type: "unified-line" }>["cell"],
   lineNumberWidth: number,
   showLineNumbers: boolean,
 ) {
-  return stackGutterText(cell, lineNumberWidth, showLineNumbers).padEnd(
+  return unifiedGutterText(cell, lineNumberWidth, showLineNumbers).padEnd(
     showLineNumbers ? lineNumberWidth * 2 + 5 : 2,
   );
 }
@@ -152,8 +152,8 @@ function staticSplitGutterText(
   );
 }
 
-/** Render one non-interactive stacked diff row as ANSI text. */
-function renderStaticStackRow(
+/** Render one non-interactive unified diff row as ANSI text. */
+function renderStaticUnifiedRow(
   row: DiffRow,
   theme: AppTheme,
   lineNumberWidth: number,
@@ -169,14 +169,14 @@ function renderStaticStackRow(
       : renderHeaderLikeRow(row.text, theme.badgeNeutral, theme.panelAlt, theme);
   }
 
-  if (row.type !== "stack-line") {
+  if (row.type !== "unified-line") {
     return "";
   }
 
   const { cell } = row;
-  const palette = stackCellPalette(cell.kind, theme, cell.moveKind);
-  return `${colorText(marker(), stackRailColor(cell.kind, theme, true), theme.panel)}${colorText(
-    staticStackGutterText(cell, lineNumberWidth, options.lineNumbers !== false),
+  const palette = unifiedCellPalette(cell.kind, theme, cell.moveKind);
+  return `${colorText(marker(), unifiedRailColor(cell.kind, theme, true), theme.panel)}${colorText(
+    staticUnifiedGutterText(cell, lineNumberWidth, options.lineNumbers !== false),
     palette.numberColor,
     palette.gutterBg,
   )}${serializeSpans(cell.spans, palette.contentBg)}${fillRemainingLine(palette.contentBg)}`;
@@ -260,7 +260,7 @@ function renderStaticSplitRow(
 function maxLineNumberWidth(file: DiffFile, rows: DiffRow[]) {
   let max = 1;
   for (const row of rows) {
-    if (row.type === "stack-line") {
+    if (row.type === "unified-line") {
       max = Math.max(
         max,
         row.cell.oldLineNumber ? String(row.cell.oldLineNumber).length : 1,
@@ -360,9 +360,9 @@ function fileModeText(file: DiffFile) {
 }
 
 function resolveStaticLayout(options: CommonOptions) {
-  // Static pager output has historically defaulted to stack rows even on wide terminals.
+  // Static pager output has historically defaulted to unified rows even on wide terminals.
   // Honor only an explicit split request here so captured hosts avoid surprise layout changes.
-  return options.mode === "split" ? "split" : "stack";
+  return options.mode === "split" ? "split" : "unified";
 }
 
 /** Format one parsed diff file for static pager hosts like LazyGit's diff panel. */
@@ -380,7 +380,7 @@ async function renderStaticFile(
   const rows =
     layout === "split"
       ? buildSplitRows(file, highlighted, theme, tabWidth)
-      : buildStackRows(file, highlighted, theme, tabWidth);
+      : buildUnifiedRows(file, highlighted, theme, tabWidth);
   const lineNumberWidth = maxLineNumberWidth(file, rows);
   const stats = `${colorText(`+${file.stats.additions}${file.statsTruncated ? "+" : ""}`, theme.badgeAdded)} ${colorText(`-${file.stats.deletions}`, theme.badgeRemoved)}`;
   const status = colorText(`${fileStatusLabel(file)}${fileModeText(file)}`, theme.muted);
@@ -396,7 +396,7 @@ async function renderStaticFile(
       .map((row) =>
         layout === "split"
           ? renderStaticSplitRow(row, theme, lineNumberWidth, options, width, preserveFullLines)
-          : renderStaticStackRow(row, theme, lineNumberWidth, options),
+          : renderStaticUnifiedRow(row, theme, lineNumberWidth, options),
       )
       .filter(Boolean),
   ].join("\n");
diff --git a/scripts/benchmarks/compare-release-benchmarks.test.ts b/scripts/benchmarks/compare-release-benchmarks.test.ts
index 46cfb7c71..5947c9659 100644
--- a/scripts/benchmarks/compare-release-benchmarks.test.ts
+++ b/scripts/benchmarks/compare-release-benchmarks.test.ts
@@ -134,6 +134,32 @@ describe("compareBenchmarkRuns", () => {
     expect(comparison.rows[0]?.status).toBe("missing-base");
   });
 
+  test("compares historical stack metrics against the renamed unified series", () => {
+    const comparison = compareBenchmarkRuns(
+      runResult([
+        metric({
+          name: "render-layout/balanced_stream_stack_rows_ms",
+          source: "render-layout",
+          median: 100,
+        }),
+      ]),
+      runResult([
+        metric({
+          name: "render-layout/balanced_stream_unified_rows_ms",
+          source: "render-layout",
+          median: 110,
+        }),
+      ]),
+    );
+
+    expect(comparison.failed).toBe(false);
+    expect(comparison.rows).toHaveLength(1);
+    expect(comparison.rows[0]).toMatchObject({
+      name: "render-layout/balanced_stream_unified_rows_ms",
+      status: "pass",
+    });
+  });
+
   test("fails when a previously comparable metric disappears", () => {
     const comparison = compareBenchmarkRuns(runResult([metric({ median: 100 })]), runResult([]));
 
diff --git a/scripts/benchmarks/compare-release-benchmarks.ts b/scripts/benchmarks/compare-release-benchmarks.ts
index b427143bc..777b02316 100644
--- a/scripts/benchmarks/compare-release-benchmarks.ts
+++ b/scripts/benchmarks/compare-release-benchmarks.ts
@@ -180,15 +180,28 @@ function comparableThreshold(
   return baseResult?.threshold;
 }
 
+/** Map historical stack-layout metric names onto the canonical unified series. */
+function canonicalBenchmarkMetricName(name: string) {
+  if (!name.startsWith("render-layout/")) {
+    return name;
+  }
+
+  return name.replace("_stack_rows", "_unified_rows");
+}
+
 /** Compare two benchmark snapshots and mark only material regressions as failures. */
 export function compareBenchmarkRuns(
   base: BenchmarkRunResult,
   head: BenchmarkRunResult,
 ): BenchmarkComparisonResult {
-  const baseByName = new Map(base.results.map((result) => [result.name, result]));
-  const headByName = new Map(head.results.map((result) => [result.name, result]));
+  const baseByName = new Map(
+    base.results.map((result) => [canonicalBenchmarkMetricName(result.name), result]),
+  );
+  const headByName = new Map(
+    head.results.map((result) => [canonicalBenchmarkMetricName(result.name), result]),
+  );
   const acceptedRegressionNames = new Set(
-    (head.acceptedRegressions ?? []).map((entry) => entry.name),
+    (head.acceptedRegressions ?? []).map((entry) => canonicalBenchmarkMetricName(entry.name)),
   );
   const names = [...new Set([...baseByName.keys(), ...headByName.keys()])].sort();
   const rows: BenchmarkComparisonRow[] = names.map((name) => {
diff --git a/scripts/dev/test-large-untracked-render.tsx b/scripts/dev/test-large-untracked-render.tsx
index a0e6c0cd1..00336a0a7 100644
--- a/scripts/dev/test-large-untracked-render.tsx
+++ b/scripts/dev/test-large-untracked-render.tsx
@@ -60,7 +60,7 @@ try {
   writeFileSync(join(repo, largePath), createLargeFileBody(lineCount));
 
   const bootstrap = await loadAppBootstrap(
-    { kind: "vcs", staged: false, options: { mode: "stack" } },
+    { kind: "vcs", staged: false, options: { mode: "unified" } },
     { cwd: repo, vcsCatalog: getBundledVcsCatalog() },
   );
   const extensionSession = createExtensionSession(
diff --git a/scripts/launch-video/capture.ts b/scripts/launch-video/capture.ts
index c75a55356..3135480fe 100644
--- a/scripts/launch-video/capture.ts
+++ b/scripts/launch-video/capture.ts
@@ -115,7 +115,7 @@ function createDemoRepo() {
 async function captureReviewScene() {
   console.log("scene: review");
   const repoDir = createDemoRepo();
-  const session = await launchHunk(["diff", "--mode", "stack"], { cwd: repoDir });
+  const session = await launchHunk(["diff", "--mode", "unified"], { cwd: repoDir });
   try {
     await session.waitForText(/src\//, { timeout: 60_000 });
     await ensureKeyboardIsLive(session, HUNK_KEYBOARD_PROBE);
@@ -165,7 +165,7 @@ async function captureStmlScene() {
     join(repoRoot, "examples/9-agent-markup-notes/agent-context.json"),
     "--experimental",
     "--mode",
-    "stack",
+    "unified",
   ]);
   try {
     await session.waitForText(/retry\.ts/, { timeout: 60_000 });
@@ -270,7 +270,13 @@ async function captureTriageScene() {
   const repoDir = createDemoRepo();
 
   const session = await launchHunk(
-    ["diff", "--extension", join(repoRoot, "examples/extensions/review-triage"), "--mode", "stack"],
+    [
+      "diff",
+      "--extension",
+      join(repoRoot, "examples/extensions/review-triage"),
+      "--mode",
+      "unified",
+    ],
     { cwd: repoDir },
   );
   try {
@@ -333,7 +339,7 @@ async function captureFileViewScene(
     "--extension",
     join(repoRoot, "examples/extensions/jsx-file-view-gallery"),
     "--mode",
-    "stack",
+    "unified",
     before,
     after,
   ]);
diff --git a/scripts/packaging/check-pack.ts b/scripts/packaging/check-pack.ts
index 86104e74d..1d5bbb05c 100644
--- a/scripts/packaging/check-pack.ts
+++ b/scripts/packaging/check-pack.ts
@@ -24,6 +24,8 @@ import {
 } from "hunkdiff/extension";
 import type {
   ExtensionChangeset,
+  ExtensionCanonicalLayoutMode,
+  ExtensionCanonicalResolvedLayout,
   ExtensionCommandControls,
   ExtensionCommandExecutionOptions,
   ExtensionFileLanguageMatcher,
@@ -34,10 +36,12 @@ import type {
   ExtensionKeyboardModeKeyResult,
   ExtensionLineHighlight,
   ExtensionLineHighlightTone,
+  ExtensionLayoutMode,
   ExtensionPaintTheme,
   ExtensionHorizontalPane,
   ExtensionPaneProps,
   ExtensionPaneSize,
+  ExtensionResolvedLayout,
   ExtensionReviewSelection,
   ExtensionSessionOptions,
   ExtensionVerticalPane,
@@ -51,6 +55,26 @@ import type {
 } from "hunkdiff/extension";
 
 export default function (hunk: HunkExtensionAPI) {
+  const canonicalMode: ExtensionCanonicalLayoutMode = "unified";
+  const canonicalLayout: ExtensionCanonicalResolvedLayout = "unified";
+  const legacyLayout: ExtensionLayoutMode = "stack";
+  const legacyResolvedLayout: ExtensionResolvedLayout = "stack";
+  const legacyLayoutLabels: Record<ExtensionLayoutMode, string> = {
+    auto: "auto",
+    split: "split",
+    stack: "stack",
+  };
+  const canonicalLayoutLabels: Record<ExtensionCanonicalLayoutMode, string> = {
+    auto: "auto",
+    split: "split",
+    unified: "unified",
+  };
+  void canonicalMode;
+  void canonicalLayout;
+  void legacyLayout;
+  void legacyResolvedLayout;
+  void legacyLayoutLabels;
+  void canonicalLayoutLabels;
   const sessionOptions: ExtensionSessionOptions = { viewPreferences: "transient" };
   hunk.configureSession(sessionOptions);
   const noSelection: ExtensionReviewSelection = {
@@ -333,6 +357,9 @@ export default function (hunk: HunkExtensionAPI) {
   hunk.on("command_executed", ({ commandId }) => {
     hunk.log(\`terminal command \${commandId}\`);
   });
+  hunk.on("layout_changed", ({ mode, layout, canonicalMode, canonicalLayout }) => {
+    hunk.log(\`layout \${mode}:\${layout} -> \${canonicalMode}:\${canonicalLayout}\`);
+  });
   hunk.on("changeset_loaded", (event) => {
     hunk.log(\`loaded \${event.changeset.files.length} files\`);
   });
diff --git a/scripts/packaging/packed-public-consumer-check.ts b/scripts/packaging/packed-public-consumer-check.ts
index 896328166..c07920fc0 100644
--- a/scripts/packaging/packed-public-consumer-check.ts
+++ b/scripts/packaging/packed-public-consumer-check.ts
@@ -71,10 +71,14 @@ export function checkPackedPublicConsumers(repoRoot: string) {
     writeFileSync(
       path.join(consumerRoot, "consumer.tsx"),
       `import type { HunkExtensionAPI } from "hunkdiff/extension";\n` +
-        `import type { HunkDiffFileInput } from "hunkdiff/opentui";\n` +
+        `import type { CanonicalHunkDiffLayout, HunkDiffFileInput, HunkDiffLayout } from "hunkdiff/opentui";\n` +
         `import { HunkDiffView, createHunkDiffFile } from "hunkdiff/opentui";\n` +
         `declare const api: HunkExtensionAPI; declare const input: HunkDiffFileInput;\n` +
-        `api.log("packed"); createHunkDiffFile(input); void <HunkDiffView diff={input} width={80} />;\n`,
+        `const legacyLabels: Record<HunkDiffLayout, string> = { split: "split", stack: "stack" };\n` +
+        `const canonicalLabels: Record<CanonicalHunkDiffLayout, string> = { split: "split", unified: "unified" };\n` +
+        `api.log("packed"); createHunkDiffFile(input); void legacyLabels; void canonicalLabels;\n` +
+        `void <HunkDiffView diff={input} width={80} layout="stack" />;\n` +
+        `void <HunkDiffView diff={input} width={80} canonicalLayout="unified" />;\n`,
     );
 
     for (const [mode, resolution] of Object.entries(MODES)) {
diff --git a/test/pty/chrome.test.ts b/test/pty/chrome.test.ts
index d0b48a861..fc12b5407 100644
--- a/test/pty/chrome.test.ts
+++ b/test/pty/chrome.test.ts
@@ -291,23 +291,23 @@ describe("PTY chrome", () => {
       await session.click(/View/);
       const menu = await harness.waitForSnapshot(
         session,
-        (text) => text.includes("Stacked view") && text.includes("Split view"),
+        (text) => text.includes("Unified view") && text.includes("Split view"),
         5_000,
       );
 
-      expect(menu).toContain("Stacked view");
+      expect(menu).toContain("Unified view");
       expect(menu).toContain("Split view");
 
-      await session.click(/Stacked view/);
-      const stacked = await harness.waitForSnapshot(
+      await session.click(/Unified view/);
+      const unified = await harness.waitForSnapshot(
         session,
         (text) => !/▌.*▌/.test(text) && text.includes("1   -  export const alpha = 1;"),
         5_000,
       );
 
-      expect(stacked).not.toMatch(/▌.*▌/);
-      expect(stacked).toContain("1   -  export const alpha = 1;");
-      expect(stacked).toContain("1   -  export const beta = 1;");
+      expect(unified).not.toMatch(/▌.*▌/);
+      expect(unified).toContain("1   -  export const alpha = 1;");
+      expect(unified).toContain("1   -  export const beta = 1;");
     } finally {
       session.close();
     }
@@ -341,7 +341,7 @@ describe("PTY chrome", () => {
       await session.press("right");
       const viewMenu = await harness.waitForSnapshot(
         session,
-        (text) => text.includes("Split view") && text.includes("Stacked view"),
+        (text) => text.includes("Split view") && text.includes("Unified view"),
         5_000,
       );
 
@@ -349,14 +349,14 @@ describe("PTY chrome", () => {
 
       await session.press("down");
       await session.press("enter");
-      const stacked = await harness.waitForSnapshot(
+      const unified = await harness.waitForSnapshot(
         session,
         (text) => !/▌.*▌/.test(text) && text.includes("1   -  export const alpha = 1;"),
         5_000,
       );
 
-      expect(stacked).not.toMatch(/▌.*▌/);
-      expect(stacked).toContain("1   -  export const alpha = 1;");
+      expect(unified).not.toMatch(/▌.*▌/);
+      expect(unified).toContain("1   -  export const alpha = 1;");
     } finally {
       session.close();
     }
diff --git a/test/pty/cursor-line.test.ts b/test/pty/cursor-line.test.ts
index 8a59ecf2c..532b13e03 100644
--- a/test/pty/cursor-line.test.ts
+++ b/test/pty/cursor-line.test.ts
@@ -26,7 +26,7 @@ describe("PTY current line", () => {
   test("stepping moves the current line before it moves the viewport", async () => {
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["show", "HEAD", "--mode", "stack"],
+      args: ["show", "HEAD", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -146,7 +146,7 @@ describe("PTY current line", () => {
     }
   });
 
-  test("a current-line pane pins old above new and hides in stack mode", async () => {
+  test("a current-line pane pins old above new and hides in unified mode", async () => {
     const fixture = harness.createLongWrapFilePair();
     const session = await harness.launchHunk({
       args: [
@@ -221,7 +221,7 @@ describe("PTY current line", () => {
   test("a held step key advances one line per press", async () => {
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["show", "HEAD", "--mode", "stack"],
+      args: ["show", "HEAD", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -256,7 +256,7 @@ describe("PTY current line", () => {
   test("stepping reaches the lines an expanded gap reveals", async () => {
     const fixture = harness.createExpandableContextFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cols: 140,
       rows: 16,
     });
@@ -282,7 +282,7 @@ describe("PTY current line", () => {
   test("expanding a gap moves the current line into it and collapsing puts it back", async () => {
     const fixture = harness.createExpandableContextFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cols: 140,
       rows: 16,
     });
@@ -323,7 +323,7 @@ describe("PTY current line", () => {
   test("paging leaves the current line on screen", async () => {
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["show", "HEAD", "--mode", "stack"],
+      args: ["show", "HEAD", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -345,7 +345,7 @@ describe("PTY current line", () => {
   test("a note after paging opens where the reviewer is looking", async () => {
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["show", "HEAD", "--mode", "stack"],
+      args: ["show", "HEAD", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -373,7 +373,7 @@ describe("PTY current line", () => {
   test("a note anchors at the current line instead of the top of the hunk", async () => {
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["show", "HEAD", "--mode", "stack"],
+      args: ["show", "HEAD", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
diff --git a/test/pty/extensions-integration.test.ts b/test/pty/extensions-integration.test.ts
index e89a1fafe..fd43276f8 100644
--- a/test/pty/extensions-integration.test.ts
+++ b/test/pty/extensions-integration.test.ts
@@ -341,7 +341,7 @@ describe("PTY extensions", () => {
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
         "diff",
         "--mode",
-        "stack",
+        "unified",
       ],
       cwd: fixture.dir,
       cols: 140,
@@ -400,7 +400,7 @@ describe("PTY extensions", () => {
       "diff --git a/probe.txt b/probe.txt\\n--- a/probe.txt\\n+++ b/probe.txt\\n@@ -1 +1 @@\\n-before\\n+ordinary\\n",
     );
     const session = await harness.launchHunk({
-      args: ["patch", patch, "--mode", "stack"],
+      args: ["patch", patch, "--mode", "unified"],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
@@ -420,7 +420,7 @@ describe("PTY extensions", () => {
     const configHome = harness.createIsolatedConfigHome();
     const fixture = harness.createRepoExtensionFixture(TRANSFORM_EXTENSION_SOURCE);
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
@@ -459,7 +459,7 @@ describe("PTY extensions", () => {
     const fixture = harness.createRepoExtensionFixture(INTERRUPT_SHUTDOWN_EXTENSION_SOURCE);
     const shutdownLog = join(fixture.dir, ".hunk-shutdown.log");
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -486,7 +486,7 @@ describe("PTY extensions", () => {
     const configHome = harness.createIsolatedConfigHome();
     const fixture = harness.createRepoExtensionFixture(TRANSFORM_EXTENSION_SOURCE);
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
@@ -517,7 +517,7 @@ describe("PTY extensions", () => {
     const fixture = harness.createRepoExtensionFixture(TRANSFORM_EXTENSION_SOURCE);
     const launch = async () =>
       await harness.launchHunk({
-        args: ["diff", "--mode", "stack"],
+        args: ["diff", "--mode", "unified"],
         cwd: fixture.dir,
         cols: 140,
         rows: 24,
@@ -566,7 +566,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -607,7 +607,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         // Load the fixture through the dev flag so it is trusted without a prompt.
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
@@ -654,7 +654,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -688,7 +688,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -737,7 +737,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -781,7 +781,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         // Load the fixture through the dev flag so it is trusted without a prompt.
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
@@ -830,7 +830,7 @@ describe("PTY extensions", () => {
     const configHome = harness.createIsolatedConfigHome();
     const fixture = harness.createBottomClampedRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--extension", REVIEW_NOTE_NAVIGATOR_EXTENSION],
+      args: ["diff", "--mode", "unified", "--extension", REVIEW_NOTE_NAVIGATOR_EXTENSION],
       cwd: fixture.dir,
       cols: 140,
       rows: 22,
@@ -888,7 +888,7 @@ describe("PTY extensions", () => {
     const fixture = harness.createTwoFileRepoFixture();
     const outputPath = join(fixture.dir, "review-snapshot.json");
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--extension", REVIEW_SNAPSHOT_EXPORT_EXTENSION],
+      args: ["diff", "--mode", "unified", "--extension", REVIEW_SNAPSHOT_EXPORT_EXTENSION],
       cwd: fixture.dir,
       cols: 140,
       rows: 30,
@@ -935,7 +935,7 @@ describe("PTY extensions", () => {
     const configHome = harness.createIsolatedConfigHome();
     const fixture = harness.createRepoExtensionFixture(TRANSFORM_EXTENSION_SOURCE);
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--extension", REVIEW_TRIAGE_EXTENSION],
+      args: ["diff", "--mode", "unified", "--extension", REVIEW_TRIAGE_EXTENSION],
       cwd: fixture.dir,
       cols: 140,
       rows: 30,
@@ -983,7 +983,7 @@ describe("PTY extensions", () => {
     // Enough changed rows that top/bottom navigation has an observable viewport effect.
     const fixture = harness.createPinnedHeaderRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--extension", VIM_NAVIGATION_EXTENSION],
+      args: ["diff", "--mode", "unified", "--extension", VIM_NAVIGATION_EXTENSION],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
@@ -1130,7 +1130,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -1179,7 +1179,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -1232,7 +1232,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
       ],
@@ -1272,7 +1272,7 @@ describe("PTY extensions", () => {
       args: [
         "diff",
         "--mode",
-        "stack",
+        "unified",
         // Load the fixture through the dev flag so it is trusted without a prompt.
         "--extension",
         join(fixture.dir, ".hunk", "extensions", "fixture.ts"),
diff --git a/test/pty/file-views-integration.test.ts b/test/pty/file-views-integration.test.ts
index b11192985..ade02116b 100644
--- a/test/pty/file-views-integration.test.ts
+++ b/test/pty/file-views-integration.test.ts
@@ -114,7 +114,7 @@ describe("PTY file views", () => {
   test("does not load the Markdown example unless the user installs it", async () => {
     const pair = createMarkdownPairTest();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--files", pair.before, pair.after],
+      args: ["diff", "--mode", "unified", "--files", pair.before, pair.after],
       cwd: pair.directory,
       cols: 140,
       rows: 24,
@@ -139,7 +139,7 @@ describe("PTY file views", () => {
         "--extension",
         RENDERED_MARKDOWN_EXTENSION,
         "--mode",
-        "stack",
+        "unified",
         "--files",
         pair.before,
         pair.after,
@@ -211,7 +211,7 @@ describe("PTY file views", () => {
           "--extension",
           JSX_FILE_VIEW_GALLERY,
           "--mode",
-          "stack",
+          "unified",
           "--files",
           demo.before,
           demo.after,
@@ -298,7 +298,7 @@ describe("PTY file views", () => {
         "--extension",
         extension,
         "--mode",
-        "stack",
+        "unified",
         "--files",
         pair.before,
         pair.after,
@@ -351,7 +351,7 @@ describe("PTY file views", () => {
         "--extension",
         extension,
         "--mode",
-        "stack",
+        "unified",
         "--files",
         pair.before,
         pair.after,
@@ -405,7 +405,7 @@ describe("PTY file views", () => {
     const repo = harness.createTwoFileRepoFixture();
     const edited = join(repo.dir, "alpha.ts");
     const session = await harness.launchHunk({
-      args: ["diff", "--extension", INLINE_EDIT_EXTENSION, "--mode", "stack"],
+      args: ["diff", "--extension", INLINE_EDIT_EXTENSION, "--mode", "unified"],
       cwd: repo.dir,
       cols: 140,
       rows: 24,
@@ -488,7 +488,7 @@ describe("PTY file views", () => {
         "--extension",
         INLINE_EDIT_EXTENSION,
         "--mode",
-        "stack",
+        "unified",
         "--agent-context",
         agentContext,
         "--agent-notes",
@@ -527,7 +527,7 @@ describe("PTY file views", () => {
     const edited = join(repo.dir, "alpha.ts");
     writeFileSync(edited, "😀\n", "utf8");
     const session = await harness.launchHunk({
-      args: ["diff", "--extension", INLINE_EDIT_EXTENSION, "--mode", "stack"],
+      args: ["diff", "--extension", INLINE_EDIT_EXTENSION, "--mode", "unified"],
       cwd: repo.dir,
       cols: 140,
       rows: 24,
@@ -558,7 +558,7 @@ describe("PTY file views", () => {
         "--extension",
         RENDERED_MARKDOWN_EXTENSION,
         "--mode",
-        "stack",
+        "unified",
         "--agent-context",
         pair.agentContext,
         "--agent-notes",
@@ -595,7 +595,7 @@ describe("PTY file views", () => {
         "--extension",
         RENDERED_MARKDOWN_EXTENSION,
         "--mode",
-        "stack",
+        "unified",
         "--agent-context",
         pair.agentContext,
         "--agent-notes",
diff --git a/test/pty/highlighting.test.ts b/test/pty/highlighting.test.ts
index 93eeea5bd..e898a1637 100644
--- a/test/pty/highlighting.test.ts
+++ b/test/pty/highlighting.test.ts
@@ -36,7 +36,7 @@ describe("PTY syntax highlighting", () => {
   test("keeps key input responsive while a large added file highlights", async () => {
     const fixture = createLargeHighlightTestFiles();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--fast", "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--fast", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 24,
@@ -79,7 +79,7 @@ describe("PTY syntax highlighting", () => {
   test("keeps code after a hidden Elixir heredoc opener out of the string token state", async () => {
     const fixture = harness.createElixirHeredocRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 100,
       rows: 24,
diff --git a/test/pty/key-routing.test.ts b/test/pty/key-routing.test.ts
index e81291e65..9c1600c0d 100644
--- a/test/pty/key-routing.test.ts
+++ b/test/pty/key-routing.test.ts
@@ -129,19 +129,19 @@ describe("PTY key routing", () => {
         5_000,
       );
 
-      // Open the menu bar and pick "Stacked view" from the View menu with Enter.
+      // Open the menu bar and pick "Unified view" from the View menu with Enter.
       await session.press("f10");
       await session.waitForText(/Reload/, { timeout: 5_000 });
       await session.press("right");
       await harness.waitForSnapshot(
         session,
-        (text) => text.includes("Split view") && text.includes("Stacked view"),
+        (text) => text.includes("Split view") && text.includes("Unified view"),
         5_000,
       );
       await session.press("down");
       await session.press("enter");
 
-      // The menu item must run (layout switches to stacked) and the Enter must
+      // The menu item must run (layout switches to unified) and the Enter must
       // stop there: the filter keeps focus and its text instead of submitting.
       const afterEnter = await harness.waitForSnapshot(
         session,
diff --git a/test/pty/layout.test.ts b/test/pty/layout.test.ts
index 2692bed80..283109b18 100644
--- a/test/pty/layout.test.ts
+++ b/test/pty/layout.test.ts
@@ -67,7 +67,7 @@ describe("PTY layout", () => {
     // appear without any scroll input.
     const fixture = harness.createManyShortFileRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--no-sidebar"],
+      args: ["diff", "--mode", "unified", "--no-sidebar"],
       cwd: fixture.dir,
       cols: 100,
       rows: 40,
@@ -91,10 +91,33 @@ describe("PTY layout", () => {
     }
   });
 
+  test("the deprecated stack CLI value renders the canonical unified layout", async () => {
+    const fixture = harness.createTwoFileRepoFixture();
+    const session = await harness.launchHunk({
+      args: ["diff", "--mode", "stack", "--no-sidebar"],
+      cwd: fixture.dir,
+      cols: 100,
+      rows: 24,
+    });
+
+    try {
+      const snapshot = await harness.waitForSnapshot(
+        session,
+        (text) => text.includes("alpha.ts") && text.includes("1   -  export const alpha = 1;"),
+        8_000,
+      );
+
+      expect(snapshot).not.toMatch(/▌.*▌/);
+      expect(snapshot).toContain("1   -  export const alpha = 1;");
+    } finally {
+      session.close();
+    }
+  });
+
   test("a larger file gap inserts blank rows before the next file header", async () => {
     const fixture = harness.createTwoFileRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack", "--no-sidebar", "--file-gap", "3"],
+      args: ["diff", "--mode", "unified", "--no-sidebar", "--file-gap", "3"],
       cwd: fixture.dir,
       cols: 100,
       rows: 24,
@@ -131,7 +154,7 @@ describe("PTY layout", () => {
         fixture.before,
         fixture.after,
         "--mode",
-        "stack",
+        "unified",
         "--no-sidebar",
         "--hunk-gap",
         "2",
@@ -226,7 +249,7 @@ describe("PTY layout", () => {
   test("the CLI tab width reaches interactive app rendering", async () => {
     const fixture = harness.createTabbedFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack", "-x8"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified", "-x8"],
       cols: 100,
       rows: 12,
     });
@@ -620,10 +643,10 @@ describe("PTY layout", () => {
     }
   });
 
-  test("explicit stack mode stays stacked after a live resize", async () => {
+  test("explicit unified mode stays unified after a live resize", async () => {
     const fixture = harness.createTwoFileRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
@@ -650,10 +673,10 @@ describe("PTY layout", () => {
     }
   });
 
-  test("direct layout hotkeys can switch between split, stack, and auto in a real PTY", async () => {
+  test("direct layout hotkeys can switch between split, unified, and auto in a real PTY", async () => {
     const fixture = harness.createTwoFileRepoFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--mode", "stack"],
+      args: ["diff", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 220,
       rows: 24,
@@ -677,14 +700,14 @@ describe("PTY layout", () => {
       expect(split).toMatch(/▌.*▌/);
 
       await session.press("2");
-      const stack = await harness.waitForSnapshot(
+      const unified = await harness.waitForSnapshot(
         session,
         (text) => !/▌.*▌/.test(text) && text.includes("1   -  export const alpha = 1;"),
         5_000,
       );
 
-      expect(stack).not.toMatch(/▌.*▌/);
-      expect(stack).toContain("1   -  export const alpha = 1;");
+      expect(unified).not.toMatch(/▌.*▌/);
+      expect(unified).toContain("1   -  export const alpha = 1;");
 
       await session.press("0");
       const auto = await harness.waitForSnapshot(
@@ -732,13 +755,13 @@ describe("PTY layout", () => {
       expect(anchoredLineNumber).toBeDefined();
 
       await session.press("2");
-      const stacked = await harness.waitForSnapshot(
+      const unified = await harness.waitForSnapshot(
         session,
         (text) => !/▌.*▌/.test(text) && text.includes(`line${anchoredLineNumber} =`),
         5_000,
       );
 
-      expect(stacked).toContain(`line${anchoredLineNumber} =`);
+      expect(unified).toContain(`line${anchoredLineNumber} =`);
 
       await session.press("1");
       const split = await harness.waitForSnapshot(
diff --git a/test/pty/lifecycle.test.ts b/test/pty/lifecycle.test.ts
index 6465e9d7b..622a3a24c 100644
--- a/test/pty/lifecycle.test.ts
+++ b/test/pty/lifecycle.test.ts
@@ -184,7 +184,7 @@ describe("PTY lifecycle", () => {
     async () => {
       const fixture = harness.createTabbedFilePair();
       const session = await harness.launchHunk({
-        args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+        args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
         cwd: fixture.dir,
       });
 
@@ -214,7 +214,7 @@ describe("PTY lifecycle", () => {
         fixture.before,
         fixture.after,
         "--mode",
-        "stack",
+        "unified",
       ]);
       const session = await harness.launchShellCommand({
         command: "exec /bin/bash --noprofile --norc -i",
diff --git a/test/pty/moved-lines.test.ts b/test/pty/moved-lines.test.ts
index ae25b3a0b..1494e0d9d 100644
--- a/test/pty/moved-lines.test.ts
+++ b/test/pty/moved-lines.test.ts
@@ -18,7 +18,7 @@ afterEach(() => {
  * for the same reason: each combination reaches the palette through its own cell builder.
  */
 describe("PTY moved-line coloring", () => {
-  for (const layout of ["stack", "split"] as const) {
+  for (const layout of ["unified", "split"] as const) {
     for (const wrap of ["--wrap", "--no-wrap"] as const) {
       test(`tints moved rows apart from ordinary added rows in ${layout} with ${wrap}`, async () => {
         const fixture = harness.createMovedLinesRepoFixture();
diff --git a/test/pty/notes.test.ts b/test/pty/notes.test.ts
index f52fb3da6..78b4ee554 100644
--- a/test/pty/notes.test.ts
+++ b/test/pty/notes.test.ts
@@ -127,7 +127,7 @@ describe("PTY notes", () => {
   test("opening a draft keeps the active line fixed while pushing following code down", async () => {
     const fixture = harness.createScrollableFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cols: 120,
       rows: 26,
     });
@@ -188,7 +188,7 @@ describe("PTY notes", () => {
         fixture.before,
         fixture.after,
         "--mode",
-        "stack",
+        "unified",
         "--cursor-line",
         "off",
       ],
@@ -283,7 +283,7 @@ describe("PTY notes", () => {
   test("saved notes can be edited and replied to through clickable threaded actions", async () => {
     const fixture = harness.createLongWrapFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cols: 100,
       rows: 30,
     });
@@ -612,10 +612,10 @@ describe("PTY notes", () => {
     }
   });
 
-  test("clicking stack-mode add-note affordances can save draft notes", async () => {
+  test("clicking unified-mode add-note affordances can save draft notes", async () => {
     const fixture = harness.createLongWrapFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cols: 100,
       rows: 20,
     });
@@ -630,11 +630,11 @@ describe("PTY notes", () => {
       await revealAddNoteNear(session, targetRow);
       await session.click(/\[\+\]/);
       await session.waitForText(/Draft note/, { timeout: 5_000 });
-      await session.type("Save this stack draft.");
+      await session.type("Save this unified draft.");
       await session.press(["ctrl", "s"]);
       const saved = await session.waitForText(/Your note/, { timeout: 5_000 });
 
-      expect(saved).toContain("Save this stack draft.");
+      expect(saved).toContain("Save this unified draft.");
     } finally {
       session.close();
     }
diff --git a/test/pty/pager.test.ts b/test/pty/pager.test.ts
index dab2b0dbe..f4b114177 100644
--- a/test/pty/pager.test.ts
+++ b/test/pty/pager.test.ts
@@ -369,13 +369,13 @@ describe("PTY pager", () => {
 
       await session.waitIdle({ timeout: 200 });
       await session.press("2");
-      const stacked = await harness.waitForSnapshot(
+      const unified = await harness.waitForSnapshot(
         session,
         (text) => !/▌.*▌/.test(text) && text.includes("line01 = 1;"),
         5_000,
       );
 
-      expect(stacked).not.toMatch(/▌.*▌/);
+      expect(unified).not.toMatch(/▌.*▌/);
 
       await session.press("1");
       const split = await harness.waitForSnapshot(session, (text) => /▌.*▌/.test(text), 5_000);
diff --git a/test/pty/session-attention-integration.test.ts b/test/pty/session-attention-integration.test.ts
index f90f02159..4da29308d 100644
--- a/test/pty/session-attention-integration.test.ts
+++ b/test/pty/session-attention-integration.test.ts
@@ -128,7 +128,7 @@ describe("PTY session attention marks", () => {
     const fixture = createTallFilePair();
     const port = await reserveLoopbackPort();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--mode", "unified"],
       cwd: fixture.dir,
       cols: 140,
       rows: 24,
diff --git a/test/pty/watch.test.ts b/test/pty/watch.test.ts
index 5b671504d..fa620506e 100644
--- a/test/pty/watch.test.ts
+++ b/test/pty/watch.test.ts
@@ -16,7 +16,7 @@ describe("PTY watch mode", () => {
   test("passively refreshes direct files after an atomic save", async () => {
     const fixture = harness.createWatchFilePair();
     const session = await harness.launchHunk({
-      args: ["diff", "--files", fixture.before, fixture.after, "--watch", "--mode", "stack"],
+      args: ["diff", "--files", fixture.before, fixture.after, "--watch", "--mode", "unified"],
       cwd: fixture.dir,
       cols: 120,
       rows: 16,
@@ -44,7 +44,7 @@ describe("PTY watch mode", () => {
   test("passively refreshes a tracked file in a linked Git worktree", async () => {
     const fixture = harness.createLinkedWorktreeWatchFixture();
     const session = await harness.launchHunk({
-      args: ["diff", "--watch", "--mode", "stack"],
+      args: ["diff", "--watch", "--mode", "unified"],
       cwd: fixture.worktreeDir,
       cols: 120,
       rows: 16,
diff --git a/test/smoke/tty.test.ts b/test/smoke/tty.test.ts
index e144d0c97..df4a3eae9 100644
--- a/test/smoke/tty.test.ts
+++ b/test/smoke/tty.test.ts
@@ -419,7 +419,7 @@ async function driveTtySmoke(options: {
 }
 
 async function runTtySmoke(options: {
-  mode?: "split" | "stack";
+  mode?: "split" | "unified" | "stack";
   pager?: boolean;
   agentContext?: boolean;
   interaction?: TtyInteraction;
@@ -517,9 +517,9 @@ describe("TTY render smoke", () => {
   });
 
   ttyTest(
-    "stack mode keeps the terminal-native stacked rows without split separators",
+    "unified mode keeps the terminal-native unified rows without split separators",
     async () => {
-      const output = await runTtySmoke({ mode: "stack" });
+      const output = await runTtySmoke({ mode: "unified" });
 
       expect(output).toContain("View  Navigate  Agent  Help");
       expect(output).toContain("▌1   -  export const answer = 41;");
@@ -528,6 +528,14 @@ describe("TTY render smoke", () => {
     },
   );
 
+  ttyTest("deprecated stack input renders canonical unified rows", async () => {
+    const output = await runTtySmoke({ mode: "stack" });
+
+    expect(output).toContain("▌1   -  export const answer = 41;");
+    expect(output).toContain("▌  1 +  export const answer = 42;");
+    expect(output).not.toContain("│1 + export const answer = 42;");
+  });
+
   ttyTest("pager mode hides chrome while still rendering the diff transcript", async () => {
     const output = await runTtySmoke({ pager: true });
 
diff --git a/website/MEDIA.md b/website/MEDIA.md
index c772f53e0..25ab0ac99 100644
--- a/website/MEDIA.md
+++ b/website/MEDIA.md
@@ -13,10 +13,10 @@ bun run website/scripts/capture-media.ts mouse      # one asset: stream|agent|mo
 
 Video assets need an ffmpeg with libx264 and libvpx-vp9 on PATH (or pointed at via `FFMPEG=`). Like the other rituals in this file it is optional and Unix-oriented; website builds and tests never run it.
 
-The two workflow captures in `public/docs/images/` are optimized copies of the current product screenshots embedded in the repository README:
+The two workflow captures in `public/docs/images/` are current product screenshots used by the docs and repository README:
 
-- `review-stream.webp` — `https://github.com/user-attachments/assets/35605618-be3f-479e-b6e0-edb089910651`
-- `agent-comments.webp` — `https://github.com/user-attachments/assets/92eb8993-f044-436d-a038-8139da5ad8de`
+- `review-stream.webp` — `https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/review-stream.webp`
+- `agent-comments.webp` — `https://raw.githubusercontent.com/modem-dev/hunk/refs/heads/main/website/public/docs/images/agent-comments.webp`
 
 They teach the full review stream and inline agent-note workflows rather than serving as decorative art. Refresh them when those workflows visibly change.
 
diff --git a/website/public/docs/images/agent-comments.webp b/website/public/docs/images/agent-comments.webp
index 0a54b12ef..903bab5be 100644
Binary files a/website/public/docs/images/agent-comments.webp and b/website/public/docs/images/agent-comments.webp differ
diff --git a/website/public/docs/images/review-stream.webp b/website/public/docs/images/review-stream.webp
index 60076e130..d9a783e52 100644
Binary files a/website/public/docs/images/review-stream.webp and b/website/public/docs/images/review-stream.webp differ
diff --git a/website/scripts/capture-media.ts b/website/scripts/capture-media.ts
index e1876f3ac..73c3b37b0 100644
--- a/website/scripts/capture-media.ts
+++ b/website/scripts/capture-media.ts
@@ -396,7 +396,7 @@ async function captureAgent() {
   }
 }
 
-/** Video: one diff flipping between split and stack layouts. */
+/** Video: one diff flipping between split and unified layouts. */
 async function captureLayout() {
   // No sidebar and a single pretty file: the layout change is the whole story,
   // and fewer columns keep both split panes readable at page width.
diff --git a/website/src/components/marketing/FeatureShowcase.astro b/website/src/components/marketing/FeatureShowcase.astro
index ef1fd4a11..106bd7067 100644
--- a/website/src/components/marketing/FeatureShowcase.astro
+++ b/website/src/components/marketing/FeatureShowcase.astro
@@ -120,8 +120,8 @@ const showcase: (ShowcaseFeature | ShowcaseQuote)[] = [
   },
   {
     kind: "feature",
-    heading: "Split or stack — or let auto decide.",
-    body: "Side-by-side when your terminal is wide, stacked when it's narrow. Auto picks for you; press 1, 2, or 0 to override at any time, with wrapping and line numbers toggled live.",
+    heading: "Split or unified — or let auto decide.",
+    body: "Side-by-side when your terminal is wide, unified when it's narrow. Auto picks for you; press 1, 2, or 0 to override at any time, with wrapping and line numbers toggled live.",
     href: "/docs/configure/layout-and-display/",
     linkText: "Layout & display options",
     media: {
@@ -129,7 +129,7 @@ const showcase: (ShowcaseFeature | ShowcaseQuote)[] = [
       base: "feature-layout",
       width: 1816,
       height: 1200,
-      label: "The same diff flipping between Hunk's side-by-side split layout and its stacked layout",
+      label: "The same diff flipping between Hunk's side-by-side split layout and its unified layout",
     },
   },
   {
diff --git a/website/src/content/docs/docs/configure/layout-and-display.md b/website/src/content/docs/docs/configure/layout-and-display.md
index ebcab6dcd..4e5319805 100644
--- a/website/src/content/docs/docs/configure/layout-and-display.md
+++ b/website/src/content/docs/docs/configure/layout-and-display.md
@@ -10,14 +10,14 @@ Hunk uses the same normalized review model in every layout.
 ```bash
 hunk diff --mode auto
 hunk diff --mode split
-hunk diff --mode stack
+hunk diff --mode unified
 ```
 
-- `auto` chooses split on wide terminals and stack on narrow ones.
+- `auto` chooses split on wide terminals and unified on narrow ones.
 - `split` keeps before and after columns side by side.
-- `stack` shows changed rows in a single-width flow.
+- `unified` shows changed rows in a single-width flow.
 
-Explicit split and stack choices override responsive behavior. Press `0`, `1`, or `2` to switch while reviewing.
+Explicit split and unified choices override responsive behavior. Press `0`, `1`, or `2` to switch while reviewing. The former `stack` value remains accepted as a deprecated input alias and normalizes to `unified`.
 
 ## Tune code rows
 
diff --git a/website/src/content/docs/docs/extend/extension-api.md b/website/src/content/docs/docs/extend/extension-api.md
index 8b0d12bf5..3a2e900cb 100644
--- a/website/src/content/docs/docs/extend/extension-api.md
+++ b/website/src/content/docs/docs/extend/extension-api.md
@@ -7,8 +7,8 @@ The extension factory receives one API object. Registration calls are only valid
 
 ## `hunk.apiVersion`
 
-The API generation this Hunk speaks (currently `22`). Branch on it if you want
-one file to support several Hunk versions. Version 22 adds frame-derived pane preferred sizing, non-resizable dynamic panes, and commit-history paint tokens; version 21 adds optional inclusive history-range review
+The API generation this Hunk speaks (currently `23`). Branch on it if you want
+one file to support several Hunk versions. Version 23 adds canonical unified-layout fields while preserving the previous event vocabulary; version 22 adds frame-derived pane preferred sizing, non-resizable dynamic panes, and commit-history paint tokens; version 21 adds optional inclusive history-range review
 planning and bounded comparison commit summaries; version 20 adds optional commit timestamps to review
 metadata, pane clipboard actions, and the `theme.copyAction` paint token; version 19 adds provider-owned history enumeration and review planning; version 18 lets
 lifecycle and custom-event handlers request a host-owned review reload; version 17 adds structured review metadata to delegated
@@ -193,7 +193,7 @@ hunk.registerLineHighlighter({
 ```
 
 Marks are addressed by source coordinates — `side`, a 1-based `line`, and a `[start, end)` range in UTF-16 code units of
-the raw line text — so they survive split vs stack layout, wrapping, horizontal scrolling, and collapsed-context
+the raw line text — so they survive split vs unified layout, wrapping, horizontal scrolling, and collapsed-context
 expansion. A mark paints terminal columns, so a range covering only zero-width characters (bidi controls, ZWSP) paints
 nothing. Tones (`match`, `current`, `info`, `warning`, `error`, `dim`) rather than colors: Hunk resolves each tinted tone
 against the actual background of each marked line with a minimum-contrast guarantee stronger than its own word-diff
@@ -398,28 +398,29 @@ Writes require a reloadable, unstaged working-tree review and a writable reviewe
 
 Subscribe to a lifecycle or UI event. Handlers may be async; Hunk never blocks the UI waiting for one. Every handler receives `ctx.panes`, live `ctx.navigation`, attributed `ctx.dialogs`, and `ctx.review.requestReload()` alongside `cwd` and `notify`, so a `startup` handler can present one focused welcome dialog and navigate to its first example without a keypress. `ctx.sidebars` is deprecated. Controls retained across a review or extension-registry replacement expire instead of controlling the replacement UI; workspace reads and writes that have not started return `null`/`unavailable`. Once a consented filesystem write starts, it reports its actual outcome, graceful shutdown waits for it, and success reconciles the review then active.
 
-| Event                  | Payload                 | When                                                     |
-| ---------------------- | ----------------------- | -------------------------------------------------------- |
-| `startup`              | `{ cwd }`               | once, after the app mounts with its first changeset      |
-| `changeset_loaded`     | `{ changeset }`         | first load and every reload                              |
-| `command_executed`     | `{ commandId }`         | after a named command dispatches in this terminal host   |
-| `selection_changed`    | `{ fileId, hunkIndex }` | when the review selection settles (debounced ~150ms)     |
-| `file_viewed`          | `{ file, hunkIndex }`   | when selection settles on a file or a reload replaces it |
-| `hunk_viewed`          | `{ file, hunkIndex }`   | when selection settles on a different hunk               |
-| `filter_changed`       | `{ filter }`            | whenever the file-filter query changes                   |
-| `theme_changed`        | `{ themeId }`           | when the user commits a new theme                        |
-| `layout_changed`       | `{ mode, layout }`      | mode or responsive split/stack layout changes            |
-| `watch_reload_pending` | `{}`                    | watcher observed a change before its reload check        |
-| `note_created`         | `{ note }`              | a user saves an inline review note                       |
-| `note_edited`          | `{ note }`              | an in-progress inline note's body changes                |
-| `note_changed`         | `{ kind, note }`        | a saved ReviewStore note is created, updated, or removed |
-| `session_reload`       | `{ changeset, reason }` | on every session reload                                  |
-| `shutdown`             | `{}`                    | on exit, best-effort within a short timeout              |
+| Event                  | Payload                                              | When                                                     |
+| ---------------------- | ---------------------------------------------------- | -------------------------------------------------------- |
+| `startup`              | `{ cwd }`                                            | once, after the app mounts with its first changeset      |
+| `changeset_loaded`     | `{ changeset }`                                      | first load and every reload                              |
+| `command_executed`     | `{ commandId, canonicalCommandId? }`                 | after a named command dispatches in this terminal host   |
+| `selection_changed`    | `{ fileId, hunkIndex }`                              | when the review selection settles (debounced ~150ms)     |
+| `file_viewed`          | `{ file, hunkIndex }`                                | when selection settles on a file or a reload replaces it |
+| `hunk_viewed`          | `{ file, hunkIndex }`                                | when selection settles on a different hunk               |
+| `filter_changed`       | `{ filter }`                                         | whenever the file-filter query changes                   |
+| `theme_changed`        | `{ themeId }`                                        | when the user commits a new theme                        |
+| `layout_changed`       | `{ mode, layout, canonicalMode?, canonicalLayout? }` | mode or responsive split/unified layout changes          |
+| `watch_reload_pending` | `{}`                                                 | watcher observed a change before its reload check        |
+| `note_created`         | `{ note }`                                           | a user saves an inline review note                       |
+| `note_edited`          | `{ note }`                                           | an in-progress inline note's body changes                |
+| `note_changed`         | `{ kind, note }`                                     | a saved ReviewStore note is created, updated, or removed |
+| `session_reload`       | `{ changeset, reason }`                              | on every session reload                                  |
+| `shutdown`             | `{}`                                                 | on exit, best-effort within a short timeout              |
 
 - A newly mounted instance receives `startup` before its first `changeset_loaded`; reloads deliver `changeset_loaded` before `session_reload` after the matching review commits.
+- Starting with extension API v23, `layout_changed` adds `canonicalMode` and `canonicalLayout`, which use `"unified"`. The original `mode` and `layout` fields remain available for compatibility and continue to report `"stack"` where their canonical counterparts report `"unified"`. To preserve exhaustive existing source, `ExtensionLayoutMode` and `ExtensionResolvedLayout` retain their pre-v23 shapes; new extensions use `ExtensionCanonicalLayoutMode` and `ExtensionCanonicalResolvedLayout`. Hunk will keep `"stack"` and the legacy fields until a separately announced major API revision.
 - `selection_changed` is trailing-debounced: holding `[`/`]` retargets many times a second, and handlers only care where the user landed. `fileId` and `hunkIndex` are `null` when nothing is selected.
 - `hunk_viewed` fires when the settled `(file, hunk)` pair changes, including `[`/`]` inside one file. Current-line movement within a hunk does not emit it. `file_viewed` still fires only when the selected file object changes.
-- `command_executed` reports stable command ids after terminal dispatch from a key, menu, or `ctx.commands.execute`. Detached async extension work may still be running; the event observes the accepted action rather than promise settlement. It follows remapped keys; browser/session review intents and widget-owned Escape, Enter, note-editor Ctrl-S, and F10 menu navigation are not terminal commands.
+- `command_executed` reports stable command ids after terminal dispatch from a key, menu, or `ctx.commands.execute`. For a renamed command, `commandId` preserves the deprecated identity and `canonicalCommandId` names its replacement. Detached async extension work may still be running; the event observes the accepted action rather than promise settlement. It follows remapped keys; browser/session review intents and widget-owned Escape, Enter, note-editor Ctrl-S, and F10 menu navigation are not terminal commands.
 - `session_reload`'s `reason` is `"watch"`, `"daemon"` (an agent command through the session broker), `"extension"` (an in-process extension request), or `"manual"`.
 - `note_created` and `note_edited` cover notes authored in Hunk's own UI this session. Agent session comments do not emit them, and a reload may remap or drop notes. Use them for incremental reactions.
 - `note_changed` is store-backed: `kind` is `"created"`, `"updated"`, or `"removed"`, and `note` matches the snapshot shape command handlers read through `ctx.review.snapshot()`. It includes agent session comments and user deletes; drafts never appear. Reloads that remap notes do not emit it — use `session_reload` to invalidate extension-owned state and read the complete current record from a later command snapshot.
diff --git a/website/src/content/docs/docs/help/compatibility.md b/website/src/content/docs/docs/help/compatibility.md
index e58f09c1e..a2f404122 100644
--- a/website/src/content/docs/docs/help/compatibility.md
+++ b/website/src/content/docs/docs/help/compatibility.md
@@ -11,10 +11,10 @@ Hunk is a terminal-native application built on OpenTUI. The best experience need
 
 - a modern terminal with Unicode and truecolor support
 - alternate-screen and mouse protocol support
-- enough columns for split mode (auto mode stacks on narrow screens)
+- enough columns for split mode (auto mode uses unified layout on narrow screens)
 - OSC 52 support when Hunk copies through the terminal clipboard protocol
 
-If a terminal omits one capability, keyboard navigation and stack layout remain the safest fallback.
+If a terminal omits one capability, keyboard navigation and unified layout remain the safest fallback.
 
 ## Remote sessions and multiplexers
 
diff --git a/website/src/content/docs/docs/help/troubleshooting.md b/website/src/content/docs/docs/help/troubleshooting.md
index d04b25cdd..7208289b7 100644
--- a/website/src/content/docs/docs/help/troubleshooting.md
+++ b/website/src/content/docs/docs/help/troubleshooting.md
@@ -35,10 +35,10 @@ Some terminals do not answer background-color queries. `theme = "auto"` then fal
 
 ## Layout or text is hard to read
 
-Try stack mode and wrapping in a narrow terminal:
+Try unified mode and wrapping in a narrow terminal:
 
 ```bash
-hunk diff --mode stack --wrap
+hunk diff --mode unified --wrap
 ```
 
 Press `?` for shortcuts, `t` for themes, and `l` for line numbers. See [terminal compatibility](/docs/help/compatibility/) for mouse, color, and clipboard limits.
diff --git a/website/src/content/docs/docs/reference/cli.md b/website/src/content/docs/docs/reference/cli.md
index 19e84dfa8..87dd1bd63 100644
--- a/website/src/content/docs/docs/reference/cli.md
+++ b/website/src/content/docs/docs/reference/cli.md
@@ -18,7 +18,7 @@ This reference is generated from the command metadata used by Hunk itself. Run `
 
 | Option                      | Description                                                     |
 | --------------------------- | --------------------------------------------------------------- |
-| `--mode <mode>`             | layout mode: auto, split, stack                                 |
+| `--mode <mode>`             | layout mode: auto, split, unified                               |
 | `--cursor-line <style>`     | current-line marker: row, number, off                           |
 | `--theme <theme>`           | named theme override                                            |
 | `--agent-context <path>`    | JSON sidecar with agent rationale                               |
diff --git a/website/src/content/docs/docs/reference/config.md b/website/src/content/docs/docs/reference/config.md
index c851864f0..d5db33698 100644
--- a/website/src/content/docs/docs/reference/config.md
+++ b/website/src/content/docs/docs/reference/config.md
@@ -22,10 +22,10 @@ The user path is `$XDG_CONFIG_HOME/hunk/config.toml` when configured. Otherwise
 
 **`mode`**
 
-Choose responsive, side-by-side, or stacked diff layout.
+Choose responsive, side-by-side, or unified diff layout.
 
 - **Type:** string
-- **Accepted:** `auto`, `split`, or `stack`
+- **Accepted:** `auto`, `split`, `unified`, or deprecated alias `stack`
 - **Built-in default:** `auto`
 
 ---
diff --git a/website/src/content/docs/docs/start/keyboard-and-mouse.md b/website/src/content/docs/docs/start/keyboard-and-mouse.md
index ffd1e031b..187d15ad1 100644
--- a/website/src/content/docs/docs/start/keyboard-and-mouse.md
+++ b/website/src/content/docs/docs/start/keyboard-and-mouse.md
@@ -27,7 +27,7 @@ Hunk navigation stays review-wide: hunk and file shortcuts move through the same
 
 | Key             | Action                                           |
 | --------------- | ------------------------------------------------ |
-| `0` / `1` / `2` | Auto / split / stack layout                      |
+| `0` / `1` / `2` | Auto / split / unified layout                    |
 | `s`             | Toggle files pane                                |
 | `t`             | Choose a theme                                   |
 | `l`             | Toggle line numbers                              |
diff --git a/website/src/content/docs/docs/start/quick-start.md b/website/src/content/docs/docs/start/quick-start.md
index c51f75713..3872aeb65 100644
--- a/website/src/content/docs/docs/start/quick-start.md
+++ b/website/src/content/docs/docs/start/quick-start.md
@@ -19,7 +19,7 @@ Inside Hunk:
 
 1. Press `]` to jump to the next hunk.
 2. Press `.` to jump to the next file.
-3. Press `1`, `2`, or `0` for split, stack, or responsive auto layout.
+3. Press `1`, `2`, or `0` for split, unified, or responsive auto layout.
 4. Press `q` to quit.
 
 ![Hunk showing a multi-file review stream with a file sidebar, split diff rows, and restrained terminal chrome](/docs/images/review-stream.webp)
diff --git a/website/src/data/comparisons.ts b/website/src/data/comparisons.ts
index b5d2d8a91..49ac15c82 100644
--- a/website/src/data/comparisons.ts
+++ b/website/src/data/comparisons.ts
@@ -128,7 +128,7 @@ export const COMPARISONS: Comparison[] = [
     summary:
       "delta restyles the text Git already printed. Hunk turns the same changeset into a review UI. Most people keep both.",
     answer:
-      "delta is a pager. It restyles the text `git diff` already printed and hands it to `less`. Hunk is a review UI. It turns the same changeset into one scrollable stream with a file sidebar, split and stack layouts, mouse support, watch mode, and agent notes beside the hunks they explain. Keep delta for everyday diffs. Open Hunk when you sit down to review.",
+      "delta is a pager. It restyles the text `git diff` already printed and hands it to `less`. Hunk is a review UI. It turns the same changeset into one scrollable stream with a file sidebar, split and unified layouts, mouse support, watch mode, and agent notes beside the hunks they explain. Keep delta for everyday diffs. Open Hunk when you sit down to review.",
     pick: {
       hunk: [
         "You review whole changesets and want a sidebar and per-hunk navigation.",
@@ -156,7 +156,7 @@ export const COMPARISONS: Comparison[] = [
         capability: "Side-by-side / split view",
         hunk: "yes",
         rival: "yes",
-        note: "delta opts in with `--side-by-side`. Hunk's `auto` layout picks split on wide terminals and stack on narrow ones.",
+        note: "delta opts in with `--side-by-side`. Hunk's `auto` layout picks split on wide terminals and unified on narrow ones.",
       },
       { capability: "Word-level highlighting inside a changed line", hunk: "yes", rival: "yes" },
       {
@@ -232,7 +232,7 @@ export const COMPARISONS: Comparison[] = [
         heading: "What Hunk does differently",
         body: [
           "Hunk parses the changeset into a document, then draws a UI over it. Every visible file becomes one continuous review stream, and the sidebar indexes that stream instead of hiding the rest of the change. `[` and `]` walk hunks across the whole changeset, `,` and `.` walk files, and the selection is real state that the sidebar, note cards, and context expansion all follow.",
-          "Holding the model in memory makes things easy that a pager cannot do at all. Press `z` to expand unchanged context around a hunk without re-running the diff. Press `1`, `2`, or `0` for split, stack, or responsive layout. Press `w` for wrapping or `t` for another theme, mid-review. `hunk diff --watch` reloads as you keep editing.",
+          "Holding the model in memory makes things easy that a pager cannot do at all. Press `z` to expand unchanged context around a hunk without re-running the diff. Press `1`, `2`, or `0` for split, unified, or responsive layout. Press `w` for wrapping or `t` for another theme, mid-review. `hunk diff --watch` reloads as you keep editing.",
           "The part with no delta equivalent is agent context. An agent that wrote the change can attach its reasoning to specific hunks through `hunk session`, and Hunk renders those notes inline, next to the code, instead of in a pane you correlate by hand.",
         ],
       },
@@ -272,7 +272,7 @@ export const COMPARISONS: Comparison[] = [
       {
         question: "Does Hunk support side-by-side diffs like `delta --side-by-side`?",
         answer:
-          "Yes, and it is the default on wide terminals. Hunk's `auto` layout picks split on wide terminals and stack on narrow ones. `1` forces split and `2` forces stack, at any point in the review.",
+          "Yes, and it is the default on wide terminals. Hunk's `auto` layout picks split on wide terminals and unified on narrow ones. `1` forces split and `2` forces unified, at any point in the review.",
       },
       {
         question: "Which is faster, Hunk or delta?",
@@ -353,7 +353,7 @@ export const COMPARISONS: Comparison[] = [
         note: "difftastic prints to the terminal, so scrolling is your pager's job.",
       },
       { capability: "Multi-file review stream with a sidebar", hunk: "yes", rival: "no" },
-      { capability: "Split and stack layouts switchable mid-review", hunk: "yes", rival: "no" },
+      { capability: "Split and unified layouts switchable mid-review", hunk: "yes", rival: "no" },
       {
         capability: "Themes",
         hunk: "yes",
@@ -496,7 +496,7 @@ export const COMPARISONS: Comparison[] = [
     summary:
       "diff-so-fancy tidies Git's diff output. Hunk replaces the reading experience. The gap is bigger than it looks.",
     answer:
-      "diff-so-fancy is a Perl script that tidies Git's diff output before your pager shows it: simpler file headers, `+` and `-` out of the gutter, colored empty lines, rulers between files. It adds no syntax highlighting and has no side-by-side view. Hunk is a review UI rather than a filter: a multi-file stream with a file sidebar, split and stack layouts, syntax highlighting, mouse support, watch mode, and inline agent annotations.",
+      "diff-so-fancy is a Perl script that tidies Git's diff output before your pager shows it: simpler file headers, `+` and `-` out of the gutter, colored empty lines, rulers between files. It adds no syntax highlighting and has no side-by-side view. Hunk is a review UI rather than a filter: a multi-file stream with a file sidebar, split and unified layouts, syntax highlighting, mouse support, watch mode, and inline agent annotations.",
     pick: {
       hunk: [
         "You want syntax highlighting, which diff-so-fancy does not do.",
@@ -577,7 +577,7 @@ export const COMPARISONS: Comparison[] = [
       {
         heading: "What you get by moving to Hunk",
         body: [
-          "The two usual reasons people leave are the two things diff-so-fancy does not do: syntax highlighting and side-by-side. Hunk has both, with a responsive `auto` layout that picks split on wide terminals and stack on narrow ones, plus theme selection you change from inside the review.",
+          "The two usual reasons people leave are the two things diff-so-fancy does not do: syntax highlighting and side-by-side. Hunk has both, with a responsive `auto` layout that picks split on wide terminals and unified on narrow ones, plus theme selection you change from inside the review.",
           "Past that it is a different category of tool. Every visible file forms one review stream with a sidebar indexing it, `[` and `]` walk hunks across the whole changeset, `z` expands unchanged context without re-running the diff, and the mouse works for scrolling, menus, and jumping to a file. `hunk diff --watch` keeps the review current while you edit, and agent notes render inline beside the hunks they explain.",
           "The trade is real. Hunk is a bigger program than a Perl script, and it takes over the screen instead of printing into your scrollback. If tidy output in `less` is what you want, diff-so-fancy is still fine.",
         ],
@@ -646,7 +646,7 @@ export const COMPARISONS: Comparison[] = [
     summary:
       "git diff prints the patch. Hunk renders the same patch as something you can navigate. Git stays the source of truth.",
     answer:
-      "`git diff` prints a unified patch to standard output. One long stream, one file after another, with no navigation past your pager's search. Hunk reads the same data and draws a review UI: one multi-file stream, a file sidebar, split or stacked layouts, syntax highlighting, mouse support, expandable context, watch mode, and agent annotations on hunks. Git still computes the diff. Hunk replaces the reading. Run `hunk diff` where you would run `git diff`, or point `core.pager` at `hunk pager`.",
+      "`git diff` prints a unified patch to standard output. One long stream, one file after another, with no navigation past your pager's search. Hunk reads the same data and draws a review UI: one multi-file stream, a file sidebar, split or unified layouts, syntax highlighting, mouse support, expandable context, watch mode, and agent annotations on hunks. Git still computes the diff. Hunk replaces the reading. Run `hunk diff` where you would run `git diff`, or point `core.pager` at `hunk pager`.",
     pick: {
       hunk: [
         "The changeset spans more than a couple of files and scrolling stopped working as navigation.",
@@ -776,7 +776,7 @@ export const COMPARISONS: Comparison[] = [
       {
         question: "How do I get a side-by-side git diff in the terminal?",
         answer:
-          "`git diff` has no side-by-side mode. Run `hunk diff` instead, where split view is the default on wide terminals, or configure a difftool. Press `1` for split, `2` for stack, and `0` for the responsive layout at any point.",
+          "`git diff` has no side-by-side mode. Run `hunk diff` instead, where split view is the default on wide terminals, or configure a difftool. Press `1` for split, `2` for unified, and `0` for the responsive layout at any point.",
       },
       {
         question: "Can I make `git diff` itself open Hunk?",
@@ -947,7 +947,7 @@ export const COMPARISONS: Comparison[] = [
       {
         heading: "What Hunk does",
         body: [
-          "Hunk stays in the terminal. Run `hunk diff` in a second pane and it renders every visible file as one continuous review stream with a sidebar, split or stacked layouts, syntax highlighting, mouse support, and `--watch` to reload as the agent keeps working.",
+          "Hunk stays in the terminal. Run `hunk diff` in a second pane and it renders every visible file as one continuous review stream with a sidebar, split or unified layouts, syntax highlighting, mouse support, and `--watch` to reload as the agent keeps working.",
           "The agent-facing part runs the other direction from a comment box. Each session registers with a local loopback daemon, and the agent uses non-interactive `hunk session` commands to inspect the review you are looking at, navigate it, and leave notes. `hunk session review --json` gives it the structure of the changeset without pushing the whole patch into its context. Its reasoning then renders inline as note cards on specific hunks, so the explanation sits next to the code instead of in a separate transcript.",
           "Hunk is also an ordinary diff viewer. The same binary is your Git pager, difftool, patch reader, and two-file comparison tool, which matters if you would rather not install a second thing for non-agent work.",
         ],
diff --git a/website/src/data/vcsLandingPages.ts b/website/src/data/vcsLandingPages.ts
index 6e6ca3f90..693650c61 100644
--- a/website/src/data/vcsLandingPages.ts
+++ b/website/src/data/vcsLandingPages.ts
@@ -30,7 +30,7 @@ export const VCS_LANDING_PAGES: VcsLandingPage[] = [
       "review git changes",
     ],
     answer:
-      "Hunk turns Git changes into one review-first terminal UI: a multi-file stream, file navigation, split or stack layouts, expandable context, watch mode, and inline agent notes. Run Hunk directly for a complete changeset, or connect it to Git as a pager or difftool.",
+      "Hunk turns Git changes into one review-first terminal UI: a multi-file stream, file navigation, split or unified layouts, expandable context, watch mode, and inline agent notes. Run Hunk directly for a complete changeset, or connect it to Git as a pager or difftool.",
     quickStart: ["hunk diff", "hunk diff --staged", "hunk show HEAD~1", "hunk stash show"],
     setup: {
       heading: "Use Hunk from Git commands",
@@ -117,7 +117,7 @@ export const VCS_LANDING_PAGES: VcsLandingPage[] = [
       "review sapling changes",
     ],
     answer:
-      "Hunk detects Sapling repositories and accepts Sapling's own revision syntax. It turns working-copy and committed changes into a multi-file terminal review with fast navigation, split or stack layouts, expandable context, and inline agent notes.",
+      "Hunk detects Sapling repositories and accepts Sapling's own revision syntax. It turns working-copy and committed changes into a multi-file terminal review with fast navigation, split or unified layouts, expandable context, and inline agent notes.",
     quickStart: ["hunk diff", "hunk diff .^", "hunk show ."],
     setup: {
       heading: "Use Hunk as the Sapling pager",
diff --git a/website/src/pages/compare/index.astro b/website/src/pages/compare/index.astro
index 59e99b17e..a04904e51 100644
--- a/website/src/pages/compare/index.astro
+++ b/website/src/pages/compare/index.astro
@@ -72,7 +72,7 @@ const reviewedOn = reviewedOnLabel();
           <h1>Hunk vs the tools<br />you already run.</h1>
           <p class="cmp-answer">
             Most terminal diff tools are pagers. They restyle the text Git already printed. Hunk is
-            a review UI: one multi-file stream, a file sidebar, split and stack layouts, expandable
+            a review UI: one multi-file stream, a file sidebar, split and unified layouts, expandable
             context, watch mode, and agent notes beside the code. These pages say where that is
             worth it, and where the other tool wins.
           </p>