diff --git a/examples/app-showcase/src/objects/task.object.ts b/examples/app-showcase/src/objects/task.object.ts
index 216ce539a..8bb437cea 100644
--- a/examples/app-showcase/src/objects/task.object.ts
+++ b/examples/app-showcase/src/objects/task.object.ts
@@ -33,7 +33,11 @@ export const Task = ObjectSchema.create({
     project: Field.masterDetail('showcase_project', {
       label: 'Project',
       required: true,
-      inlineEdit: true,
+      // Pin the editable-grid form factor (fast bulk line-item entry, with the
+      // column chooser + per-row expand). Left at `true`, the smart default
+      // would pick `form` for this fat child — the right call for many apps;
+      // here we keep the grid demo. Use `'form'` to force the per-row form.
+      inlineEdit: 'grid',
       inlineTitle: 'Tasks',
       relatedListTitle: 'Tasks',
       relatedListColumns: ['title', 'status', 'priority', 'assignee', 'due_date'],
diff --git a/packages/spec/src/data/field.zod.ts b/packages/spec/src/data/field.zod.ts
index 67eab2ea9..0f17b7326 100644
--- a/packages/spec/src/data/field.zod.ts
+++ b/packages/spec/src/data/field.zod.ts
@@ -405,15 +405,24 @@ export const FieldSchema = lazySchema(() => z.object({
   deleteBehavior: z.enum(['set_null', 'cascade', 'restrict']).optional().default('set_null').describe('What happens if referenced record is deleted'),
   /**
    * Master-detail INLINE EDITING. On a child's `master_detail`/`lookup` field
-   * (whose `reference` is the parent object), set `inlineEdit: true` to declare
-   * "this child is entered/edited inline within the parent's form". The
-   * parent's standard create/edit form then renders an editable grid for these
-   * children and saves parent + children in ONE atomic transaction — no form
-   * view config and no bespoke page. The intent lives here in the data model;
-   * forms derive the UI. Use for true line-item/composition children (invoice
-   * lines, order items); leave off for associations (comments, attachments).
+   * (whose `reference` is the parent object), declare that "this child is
+   * entered/edited inline within the parent's form". The parent's standard
+   * create/edit form then renders the children and saves parent + children in
+   * ONE atomic transaction — no form view config and no bespoke page. The intent
+   * lives here in the data model; forms derive the UI.
+   *
+   * The value also selects the EDITING FORM FACTOR:
+   *   - `true`   → auto: the UI picks `grid` or `form` from the child's shape
+   *                (rich types / many fields → `form`, else `grid`).
+   *   - `'grid'` → an editable line-item grid (fast bulk entry; thin children
+   *                like invoice lines / order items).
+   *   - `'form'` → a compact read-only list; "Add" / per-row edit opens the
+   *                child's FULL form (fat children with rich types, e.g. long
+   *                text, attachments, many fields).
+   * Use for true line-item/composition children; leave off for associations
+   * (comments, attachments) — surface those as detail-page related lists.
    */
-  inlineEdit: z.boolean().optional().describe('Edit these child records inline within the parent object\'s form (atomic master-detail).'),
+  inlineEdit: z.union([z.boolean(), z.enum(['grid', 'form'])]).optional().describe('Edit these child records inline within the parent\'s form (atomic master-detail). true = auto-pick grid/form by child shape; \'grid\' = editable line-item grid; \'form\' = list + per-row full form.'),
   /** Optional section title for the inline grid (defaults to the child object label). */
   inlineTitle: z.string().optional().describe('Title for the inline master-detail grid'),
   /** Optional explicit grid columns for the inline editor (derived from the child object when omitted). */
diff --git a/skills/objectstack-data/rules/relationships.md b/skills/objectstack-data/rules/relationships.md
index ad8796229..f855fc899 100644
--- a/skills/objectstack-data/rules/relationships.md
+++ b/skills/objectstack-data/rules/relationships.md
@@ -230,6 +230,25 @@ A form view may still set `subforms` to override the derived columns/order, but
 the relationship `inlineEdit` is the primary, zero-config path. See the
 objectstack-ui skill (Master-Detail Forms) for the rendering side.
 
+#### Inline-edit form factor (`grid` vs `form`)
+
+`inlineEdit` also picks how the children are entered:
+
+```typescript
+inlineEdit: true       // auto — pick grid/form from the child's shape (default)
+inlineEdit: 'grid'     // editable line-item grid (fast bulk entry; thin children)
+inlineEdit: 'form'     // read-only list; "Add" / per-row edit opens the FULL form
+```
+
+- **`'grid'`** — spreadsheet-like editable grid. Best for *thin* line items
+  (invoice/order lines): few columns, high volume, keyboard-fast.
+- **`'form'`** — compact read-only list; Add / per-row edit opens the child's
+  complete form. Best for *fat* children (long text, attachments, many fields)
+  that don't fit a narrow grid cell.
+- **`true`** / omitted — **smart default**: picks `form` when the child has
+  rich/form-only fields (textarea, file, image, json, location…) or more than ~8
+  editable fields, else `grid`. Set the string to override.
+
 ### Detail-page related lists (the read-side mirror)
 
 Where `inlineEdit` is the **write** side (child pulled into the parent's entry
diff --git a/skills/objectstack-ui/SKILL.md b/skills/objectstack-ui/SKILL.md
index b0d4646b4..aefa6a1ab 100644
--- a/skills/objectstack-ui/SKILL.md
+++ b/skills/objectstack-ui/SKILL.md
@@ -71,8 +71,12 @@ custom page or form config. Prefer, in order:
    DATA MODEL — set `inlineEdit: true` on the child's `master_detail` field that
    references the parent (see the objectstack-data skill → Relationships →
    Inline Editing). Every standard New/Edit form for the parent (modal, drawer,
-   full-page) then auto-renders an editable child grid and saves parent +
-   children in one atomic `/api/v1/batch`. **No view metadata needed.**
+   full-page) then auto-renders the children and saves parent + children in one
+   atomic `/api/v1/batch`. **No view metadata needed.** The value picks the
+   form factor: `'grid'` (editable line-item grid — thin children), `'form'`
+   (read-only list whose Add / per-row edit opens the child's FULL form — fat
+   children with rich types), or `true` (smart default: `form` when the child
+   has rich/form-only fields or >~8 fields, else `grid`).
 
 2. **Form view `subforms` (override / tuning).** Add to a form view only when you
    need to override the derived columns/order, or expose a child the