@@ -0,0 +1,11 @@
+---
+'@objectstack/spec': patch
+---
+
+fix(spec): a stored form view whose subform grid columns use the `field` spelling is respelled to `name` on the way in, as a relationship field's `inlineColumns` already are (#20901)
+
+**`@objectstack/spec`**
+
+- **New ADR-0087 conversion `form-view-subform-columns-canonicalized` (protocol 18, retired from the authoring path).** A form view's `subforms[].columns` accepted any value through 17.5.0 and now takes the inline grid column contract, which refuses `{ field: 'x' }` with the prescription naming `name`. The conversion rewrites that entry as `{ name: 'x' }`, every other key kept, wherever a form view travels as data at rest: a stored `view` row (its `form`, each `formViews` entry, a form view item's `config`, a flattened form overlay), an assembled manifest's `viewItems`, and `os migrate meta --from 17`, which lists the edit. A built artifact whose declared protocol floor is 17.5.0 or lower is converted too, not refused. An entry that already carries `name` is left alone, including one that carries both `field` and `name`: the parse names both keys, and the author picks one. It is the same respelling `field-column-lists-canonicalized` applies to a relationship field's `inlineColumns`, and both entries run one shared rule.
+- **Authored sources are unchanged:** `defineStack` and `objectstack validate` do not replay a retired conversion, so a source that writes `field` on a subform column is still refused with the prescription. Write `name`.
+- **Two step-18 migration entries now read true.** `inline-grid-column-currency-scale-refused` no longer says a column declaring no `type` keeps its `scale`: over a `currency` field of the child object, `defineStack` refuses it, under `inline-grid-column-identity-only-currency-scale-refused`, which the entry now names. `form-view-subform-columns-closed` names this conversion as the one mechanical edit on its carrier.
@@ -355,7 +355,13 @@ describe('major 18 in the conversions registry — two retirements, no merge dri
       expect(placementFindings(side)).toEqual([]);
     }
     expect(sortFindings(retireAtListEnd(SOURCE, A, NEXT_ORDER))).not.toEqual([]);
+    // A's entry follows its neighbour's, so a neighbour placed by the rule is
+    // found too: its entry is now followed by A's, and A is defined elsewhere.
+    const neighbour = IDENTS[k - 1]!;
     expect(placementFindings(retireAtDefinitionsEnd(SOURCE, A, NEXT_ORDER))).toEqual([
+      ...(PLACED_BEFORE_THE_RULE.has(neighbour)
+        ? []
+        : [`${neighbour} is defined above ${IDENTS[k]}; define it directly above ${A}'s definition, the entry that follows it`]),
       `${A} is defined above nothing (it is the last conversion defined); define it directly above ${IDENTS[k]}'s `
         + 'definition, the entry that follows it',
     ]);
 
@@ -7623,6 +7623,36 @@ const translationComponentSubmitLabelRemoved: MetadataConversion = {
   },
 };
 
+/**
+ * The inline grid column's one mechanical respelling, shared by both of its
+ * carriers — a relationship field's `inlineColumns`
+ * ({@link fieldColumnListsCanonicalized}) and a form view's `subforms[].columns`
+ * ({@link formViewSubformColumnsCanonicalized}) — so the two conversions cannot
+ * drift on what they rewrite, as the two carriers cannot on what they accept
+ * (both reference `InlineGridColumnSchema`).
+ *
+ * `{ field: 'x' }` → `{ name: 'x' }`, every other key kept. An entry already
+ * carrying `name` is left alone — rewriting a live key on the strength of a
+ * stale one would guess; the parse refuses the mixed shape loudly instead.
+ * Returns the same array when nothing was respelled (copy-on-write).
+ */
+function respellInlineGridColumns(
+  columns: readonly unknown[],
+  path: string,
+  emit: (detail: ConversionApplication) => void,
+): readonly unknown[] {
+  let changed = false;
+  const next = columns.map((entry, i) => {
+    if (!isDict(entry) || typeof entry.field !== 'string' || 'name' in entry) return entry;
+    const renamed = renameKey(entry, 'field', 'name');
+    if (!renamed) return entry;
+    emit({ from: 'field', to: 'name', path: `${path}[${i}].name` });
+    changed = true;
+    return renamed;
+  });
+  return changed ? next : columns;
+}
+
 /**
  * `field.inlineColumns[]` / `field.relatedListColumns[]` — the mechanical half
  * of the #9227 strict-element narrowing (protocol 18).
@@ -7667,16 +7697,8 @@ const fieldColumnListsCanonicalized: MetadataConversion = {
       let next: Dict = def;
       const inline = def.inlineColumns;
       if (Array.isArray(inline)) {
-        let changed = false;
-        const cols = inline.map((entry, i) => {
-          if (!isDict(entry) || typeof entry.field !== 'string' || 'name' in entry) return entry;
-          const renamed = renameKey(entry, 'field', 'name');
-          if (!renamed) return entry;
-          emit({ from: 'field', to: 'name', path: `${path}.inlineColumns[${i}].name` });
-          changed = true;
-          return renamed;
-        });
-        if (changed) next = { ...next, inlineColumns: cols };
+        const cols = respellInlineGridColumns(inline, `${path}.inlineColumns`, emit);
+        if (cols !== inline) next = { ...next, inlineColumns: cols };
       }
       const related = def.relatedListColumns;
       if (Array.isArray(related)) {
@@ -9820,6 +9842,163 @@ const connectorConnectionTimeoutMsRemoved: MetadataConversion = {
   },
 };
 
+/**
+ * `subforms[].columns[].field` → `name` on every form view — the mechanical
+ * half of the #20901 closure of the form-view carrier (protocol 18).
+ *
+ * `FormViewSchema.subforms[].columns` was `z.array(z.any())` through 17.5.0 and
+ * now references `InlineGridColumnSchema`, whose alias table refuses `field`
+ * with a prescription naming `name`. That is the break a relationship field's
+ * `inlineColumns` took in #9227, and the respelling is the same one: it runs
+ * through {@link respellInlineGridColumns}, shared with
+ * {@link fieldColumnListsCanonicalized}. ADR-0087's pre-GA policy owes a
+ * lossless break a `retiredFromLoadPath` chain step in the same release.
+ *
+ * **Its own entry, not a wider walk in `field-column-lists-canonicalized`,**
+ * because `retiredAfter` is one fact per entry (ADR-0087, amended 2026-09-30):
+ * that entry's carriers stopped accepting `field` after 17.0.0, and the census
+ * pins that published value, while this carrier accepted it through 17.5.0. The
+ * artifact-ingestion door opens its window per entry by `retiredAfter`, so under
+ * the older stamp an artifact whose declared floor is 17.5.0 would meet the
+ * refusal instead of this rewrite on a runtime still labelled 17.5.0.
+ *
+ * **Reach: every FORM payload.** {@link mapViewPayloads} reaches `form`,
+ * `formViews.*`, a form view item's `config` and a flattened form overlay — the
+ * stored-row seam wraps a `view` row as `{ views: [row] }` in any of those
+ * spellings — and the assembled-manifest `viewItems` channel
+ * ({@link ASSEMBLED_VIEW_ITEMS_KEY}) carries the last two. A list payload is
+ * never judged. `FormViewSchema` is the only schema that declares `subforms`.
+ *
+ * `retiredFromLoadPath`: the parse refuses `field` with the prescription, so a
+ * live author is taught rather than rewritten. The entry exists so stored rows
+ * and assembled artifacts replay clean, and so `os migrate meta` lists the edit.
+ * Idempotent by construction: the rewrite leaves no `field` on the entry.
+ */
+const formViewSubformColumnsCanonicalized: MetadataConversion = {
+  id: 'form-view-subform-columns-canonicalized',
+  toMajor: 18,
+  retiredFromLoadPath: true,
+  retiredAfter: '17.5.0',
+  surface: 'view.form.subforms[].columns[].field / view.formViews.<key>.subforms[].columns[].field',
+  summary:
+    "form-view subform grid column entries respelled 'field' → 'name', the grid's column identity "
+    + '(the carrier accepted any value until it took the inline grid column contract; a '
+    + "relationship field's inlineColumns get the same respelling from field-column-lists-canonicalized)",
+  apply(stack, emit) {
+    const respellSubforms = (form: Dict, path: string): Dict => {
+      const subforms = form.subforms;
+      if (!Array.isArray(subforms)) return form;
+      let changed = false;
+      const next = subforms.map((subform, j) => {
+        if (!isDict(subform) || !Array.isArray(subform.columns)) return subform;
+        const columns = respellInlineGridColumns(subform.columns, `${path}.subforms[${j}].columns`, emit);
+        if (columns === subform.columns) return subform;
+        changed = true;
+        return { ...subform, columns };
+      });
+      return changed ? { ...form, subforms: next } : form;
+    };
+    const withViews = mapViewPayloads(stack, (payload, kind, path) =>
+      kind === 'form' ? respellSubforms(payload, path) : payload);
+    return mapCollection(withViews, ASSEMBLED_VIEW_ITEMS_KEY, (item, path) => {
+      if (item.viewKind !== 'form') return item;
+      if (isDict(item.config)) {
+        const config = respellSubforms(item.config, `${path}.config`);
+        return config === item.config ? item : { ...item, config };
+      }
+      // A flattened form overlay — the body IS the payload. A present but
+      // malformed `config` is neither shape and is left for the parse.
+      return item.config === undefined ? respellSubforms(item, path) : item;
+    });
+  },
+  fixture: {
+    before: {
+      views: [
+        {
+          object: 'crm_invoice',
+          // A container: the default form and a named form view.
+          form: {
+            type: 'simple',
+            subforms: [{
+              childObject: 'crm_invoice_line',
+              columns: [
+                // The `field` spelling, every other key kept.
+                { field: 'product' },
+                { field: 'quantity', label: 'Qty' },
+                // Already name-keyed — untouched.
+                { name: 'unit_price' },
+                // Both keys — untouched: which column was meant is the
+                // author's call, and the parse names both keys.
+                { field: 'amount', name: 'total' },
+              ],
+            }],
+          },
+          formViews: {
+            quick: { type: 'simple', subforms: [{ childObject: 'crm_invoice_line', columns: [{ field: 'product' }] }] },
+          },
+        },
+      ],
+      viewItems: [
+        // An assembled form view item record, and a flattened form overlay.
+        {
+          name: 'crm_invoice.entry',
+          object: 'crm_invoice',
+          viewKind: 'form',
+          config: { type: 'simple', subforms: [{ childObject: 'crm_invoice_line', columns: [{ field: 'product' }] }] },
+        },
+        {
+          name: 'crm_invoice.edit',
+          object: 'crm_invoice',
+          viewKind: 'form',
+          type: 'simple',
+          subforms: [{ childObject: 'crm_invoice_line', columns: [{ field: 'product' }] }],
+        },
+      ],
+    },
+    after: {
+      views: [
+        {
+          object: 'crm_invoice',
+          form: {
+            type: 'simple',
+            subforms: [{
+              childObject: 'crm_invoice_line',
+              columns: [
+                { name: 'product' },
+                { name: 'quantity', label: 'Qty' },
+                { name: 'unit_price' },
+                { field: 'amount', name: 'total' },
+              ],
+            }],
+          },
+          formViews: {
+            quick: { type: 'simple', subforms: [{ childObject: 'crm_invoice_line', columns: [{ name: 'product' }] }] },
+          },
+        },
+      ],
+      viewItems: [
+        {
+          name: 'crm_invoice.entry',
+          object: 'crm_invoice',
+          viewKind: 'form',
+          config: { type: 'simple', subforms: [{ childObject: 'crm_invoice_line', columns: [{ name: 'product' }] }] },
+        },
+        {
+          name: 'crm_invoice.edit',
+          object: 'crm_invoice',
+          viewKind: 'form',
+          type: 'simple',
+          subforms: [{ childObject: 'crm_invoice_line', columns: [{ name: 'product' }] }],
+        },
+      ],
+    },
+    // One per respelled column: two in the container's `form`, one in its named
+    // form view, one in the assembled record and one in the assembled overlay.
+    // The name-keyed and the two-key entries emit none.
+    expectedNotices: 5,
+  },
+};
+
 /**
  * `hook.timeout` → `hook.timeoutMs` (protocol 18, #14478; maintainer ruling
  * 2026-09-02, recorded on the card as "ruled B").
@@ -13074,6 +13253,7 @@ const MAJOR_18_CONVERSIONS: readonly OrderedConversion[] = [
   { conversion: flowDecisionModeInclusiveExplicit, order: 45 },
   { conversion: formLayoutInlineGridToVertical, order: 40 },
   { conversion: formViewOptionDefaultRemoved, order: 17 },
+  { conversion: formViewSubformColumnsCanonicalized, order: 51 },
   { conversion: hookTimeoutToTimeoutMs, order: 21 },
   { conversion: jobTimeoutToTimeoutMs, order: 22 },
   { conversion: listViewSortStringClauseToArray, order: 30 },