diff --git a/.changeset/mapdensity-dead-rowheight-spellings-4352.md b/.changeset/mapdensity-dead-rowheight-spellings-4352.md
new file mode 100644
index 0000000000..8d6e986408
--- /dev/null
+++ b/.changeset/mapdensity-dead-rowheight-spellings-4352.md
@@ -0,0 +1,36 @@
+---
+'@object-ui/react': minor
+---
+
+`bridgeListView` maps the five row heights the spec admits, and only those — the four dead spellings are gone
+
+`mapDensity` carried a nine-key table: `compact`, `short`, `comfortable`,
+`spacious`, `small`, `medium`, `large`, `tall`, `extra_tall`. `RowHeightSchema`
+in `@objectstack/spec` admits five — `short | compact | medium | tall |
+extra_tall` — so `comfortable`, `spacious`, `small` and `large` were unreachable
+from any spec-valid list view. The bridge's own parameter type said as much
+(`Partial< ListView >`), and `mapDensity` widened it back to `rowHeight?: string`
+to let them in. They survived because the fixture asserting three of them
+compiled against nothing: the package's build tsconfig excludes tests and no
+other `tsc` read them, so four branches of renderer-side dialect read as live
+capability (objectui#4352, surfaced by objectui#4040 / PR #4351).
+
+They are deleted. The parameter takes the spec type honestly, and the table is
+now `Record< RowHeight, … >`, so a row height added upstream fails the build here
+instead of arriving with no density. This is AGENTS.md #0.1: a lenient reading
+for off-spec metadata is a second de-facto contract, and one strict contract
+beats N dialects — a bad `rowHeight` gets fixed at the producer, where the schema
+already rejects it.
+
+**Breaking semantics, deliberately graded `minor`** (this repo never publishes
+`major` — its major tracks `@objectstack`). Nothing narrows in the published type
+surface: `mapDensity` is module-local and never appeared in the emitted `.d.ts`,
+and `bridgeListView`'s declaration is unchanged. What changes is runtime output,
+and only for input the spec already rejects: a host handing the bridge
+`rowHeight: 'comfortable'` (or `'spacious'` / `'small'` / `'large'`) used to get
+`density: 'comfortable'` / `'spacious'` / `'compact'` back, and now gets no
+`density` key at all, so the renderer's own default applies. A sweep of this repo,
+the `objectstack` example apps and the console's view metadata found zero authored
+uses of any of the four; the legacy `densityMode` alias cannot produce one either,
+since `DENSITY_MODE_TO_ROW_HEIGHT` is typed `Record< DensityMode, RowHeight >` and
+folds onto `compact` / `medium` / `tall`.
diff --git a/packages/react/src/spec-bridge/__tests__/SpecBridge.test.ts b/packages/react/src/spec-bridge/__tests__/SpecBridge.test.ts
index db62e05042..67cd477d7c 100644
--- a/packages/react/src/spec-bridge/__tests__/SpecBridge.test.ts
+++ b/packages/react/src/spec-bridge/__tests__/SpecBridge.test.ts
@@ -183,6 +183,46 @@ describe('SpecBridge', () => {
       expect(extraTall.density).toBe('spacious');
     });
 
+    // The other half of that enum: `comfortable` / `spacious` / `small` /
+    // `large` used to be mapped too, so four values `RowHeightSchema` does not
+    // admit read as live capability. They are gone (objectui#4352) — AGENTS.md
+    // #0.1, one strict contract beats N dialects — and an off-spec `rowHeight`
+    // now falls through to no density at all rather than being quietly
+    // rehabilitated into one.
+    //
+    // Routed through `SpecBridge.transformListView`, whose parameter is `any`:
+    // that untyped boundary is the one a host's stored JSON actually crosses,
+    // and it is the only way left to get these values into the bridge. Writing
+    // them on `bridgeListView` directly no longer type-checks, which is the
+    // static half of the same fix.
+    it.each(['comfortable', 'spacious', 'small', 'large'])(
+      'leaves density unset for the off-spec rowHeight %s',
+      (rowHeight) => {
+        const node = new SpecBridge().transformListView({
+          name: 'off_spec_density',
+          rowHeight,
+        });
+
+        expect(node.density).toBeUndefined();
+        // Not merely undefined — the key is never written, so the renderer's
+        // own default applies instead of an explicit `density: undefined`.
+        expect('density' in node).toBe(false);
+      },
+    );
+
+    // Control: a string in neither vocabulary already fell through before the
+    // four keys were deleted, and still does. Green on both sides of the
+    // change — it pins the fall-through itself, not the deletion.
+    it('leaves density unset for a rowHeight in no vocabulary at all', () => {
+      const node = new SpecBridge().transformListView({
+        name: 'off_spec_density',
+        rowHeight: 'gargantuan',
+      });
+
+      expect(node.density).toBeUndefined();
+      expect('density' in node).toBe(false);
+    });
+
     it('includes optional list properties', () => {
       const node = bridgeListView(
         {
diff --git a/packages/react/src/spec-bridge/bridges/list-view.ts b/packages/react/src/spec-bridge/bridges/list-view.ts
index b526a84a98..ee4b859b4e 100644
--- a/packages/react/src/spec-bridge/bridges/list-view.ts
+++ b/packages/react/src/spec-bridge/bridges/list-view.ts
@@ -8,7 +8,7 @@
 
 import type { SchemaNode } from '@object-ui/core';
 import type { BridgeContext, BridgeFn } from '../types';
-import type { ListView, ListColumn } from '@objectstack/spec/ui';
+import type { ListView, ListColumn, RowHeight } from '@objectstack/spec/ui';
 
 /**
  * Bridge input: the spec-canonical ListView (#2231 — the former hand-written
@@ -45,22 +45,36 @@ function mapColumn(col: ListColumn | string): Record<string, any> {
   return mapped;
 }
 
+/**
+ * The spec's five row heights collapsed onto the renderer's three densities.
+ *
+ * `Record<RowHeight, …>` on purpose (objectui#4352): the key set is the spec's,
+ * so a row height added upstream fails the build here instead of silently
+ * arriving with no density. The table used to carry four more keys —
+ * `comfortable`, `spacious`, `small`, `large` — which `RowHeightSchema` does
+ * not admit, so no spec-valid list view could ever reach them; they only
+ * survived because the parameter was widened back to `string` and the fixture
+ * asserting three of them compiled against nothing. Deleting them is AGENTS.md
+ * #0.1: a renderer-side dialect for off-spec metadata is a second de-facto
+ * contract, and one strict contract beats N. An off-spec `rowHeight` now falls
+ * through to `undefined` — the producer is where it gets fixed.
+ */
+const ROW_HEIGHT_TO_DENSITY: Record<
+  RowHeight,
+  'compact' | 'comfortable' | 'spacious'
+> = {
+  compact: 'compact',
+  short: 'compact',
+  medium: 'comfortable',
+  tall: 'spacious',
+  extra_tall: 'spacious',
+};
+
 function mapDensity(
-  rowHeight?: string,
+  rowHeight?: RowHeight,
 ): 'compact' | 'comfortable' | 'spacious' | undefined {
   if (!rowHeight) return undefined;
-  const map: Record<string, 'compact' | 'comfortable' | 'spacious'> = {
-    compact: 'compact',
-    short: 'compact',
-    comfortable: 'comfortable',
-    spacious: 'spacious',
-    small: 'compact',
-    medium: 'comfortable',
-    large: 'spacious',
-    tall: 'spacious',
-    extra_tall: 'spacious',
-  };
-  return map[rowHeight];
+  return ROW_HEIGHT_TO_DENSITY[rowHeight];
 }
 
 /** Transforms a ListView spec into a DataTable SchemaNode */