diff --git a/.changeset/21464-component-props-form-family-typed.md b/.changeset/21464-component-props-form-family-typed.md
new file mode 100644
index 0000000000..24ff21831f
--- /dev/null
+++ b/.changeset/21464-component-props-form-family-typed.md
@@ -0,0 +1,43 @@
+---
+'@objectstack/spec': minor
+---
+
+feat(spec)!: four members of an `object-form` page block take the shape the form reads instead of any value — `contentLayout`, `submitBehavior`, `navigateOnSuccess` and `mobile` (#21464)
+
+Clause-②: yes (narrowing)
+
+<!-- adr-0087: registered ui-object-form-members-typed -->
+
+**BREAKING** — an accept-set narrowing on a published authoring surface, shipped as `minor` under the repo's launch-window convention for accept-set narrowings. What reads the row: the component-props gate on `objectstack validate`, `objectstack build` and `objectstack lint`, which reports a refused value as an advisory `component-props-invalid` / `component-props-unknown-key` finding. A stored page still saves and loads, because a page component's `properties` is not parsed on the metadata save or load path.
+
+**`@objectstack/spec`**
+
+- **Four members are typed.** `ComponentPropsMap['object-form']` declared `contentLayout`, `submitBehavior`, `navigateOnSuccess` and `mobile` as `z.unknown()`, although the form reads each with one shape. Any value passed, and an off-shape one was answered with a silent default: a `submitBehavior` whose `kind` the form does not know showed the thank-you panel; a misspelled `contentLayout` stacked the modal's sections; a `navigateOnSuccess` that is not a string failed the submit after the record had been written; a misspelled `mobile` member was ignored.
+- **`submitBehavior` is the form view's own block, by reference** — `{ kind: 'thank-you', title?, message? }`, `{ kind: 'redirect', url, delayMs? }`, `{ kind: 'continue' }` or `{ kind: 'next-record' }` — with the same rule on a `redirect` `url` a form view carries: a relative path, interpolating declared record fields as `{{record.field_name}}`.
+- **The measured shape, where no form view declares the member:** `contentLayout` is `'simple'` or `'tabbed'`; `navigateOnSuccess` is a relative path string (`{id}` / `{recordId}` interpolate the saved record's id); `mobile` is `{ stickyActions?, stepper?, stepperMinFields?, stepperFieldsPerStep?, fullscreenLongText? }`, with `stepper` `true`, `false` or `'auto'` and the two counts positive integers.
+- **`ObjectFormProps`** carries these types on the four members instead of `unknown`.
+- **The form's `fields` and `sections`, and the master-detail form's `fields` and `sections`, are not narrowed** and still accept any value. The form draws a top-level `fields` entry written as `{ name }` by that name, and it draws an inline runtime field (`{ name, type, … }`) written inside a section's `fields` as it stands — two shapes the typed members (field-name strings; the form view's section, whose field entry is keyed by `field`) would refuse. Each is held until that read is ruled. The master-detail form hands both members to its form unchanged, so they are held with the form's.
+- **`customFields` is not narrowed either.** Its entries are the console's runtime form field (keyed by `name`), which the spec has not declared; it is typed once the spec declares it.
+
+## FROM → TO
+
+| you wrote on an `object-form` | write instead |
+|:--|:--|
+| `submitBehavior: 'thank-you'` | `submitBehavior: { kind: 'thank-you' }` |
+| `submitBehavior: { kind: 'toast' }` (any `kind` outside the four) | one of `thank-you`, `redirect`, `continue`, `next-record` |
+| `submitBehavior: { kind: 'thank-you', heading: 'Done' }` | `{ kind: 'thank-you', title: 'Done' }` |
+| `submitBehavior: { kind: 'redirect', url: 'https://app.example.com/done' }` | a relative path: `url: '/done'` |
+| `contentLayout: 'tabs'` | `contentLayout: 'tabbed'` |
+| `navigateOnSuccess: { url: '/orders/{id}' }` | `navigateOnSuccess: '/orders/{id}'`, or `submitBehavior: { kind: 'redirect', url: '/orders/{{record.id}}' }` |
+| `mobile: { stepper: 'yes' }` | `mobile: { stepper: true }`, or `'auto'` for phone-width viewports only |
+| `mobile: { stepperFieldsPerStep: 0 }` | delete the key (one field a step is the default), or a positive integer |
+
+The one-line fix: write each member as the table above shows. No conversion is registered, because an off-shape value has no rewrite that both keeps what the form shows today and honours what the author wrote; the D3 entry `ui-object-form-members-typed` carries that judgment.
+
+## Who is affected, measured
+
+A writer is a page-component node: an object literal naming the type, a literal annotated with the block's type, a `schema={{…}}` on the block's React component, a call into a local helper that builds the node, or a direct parse through the row. Each member's value is read through same-file constants and local helpers. The control is `objectName` on the same nodes.
+
+- **objectstack** at `e909aa0a23`, over `examples/`, `packages/` (with `packages/apps/`), `content/`, `skills/` and `apps/`: 16 `object-form` nodes (the control on 13). Three values among the four members: the showcase's new-project wizard `submitBehavior` (a thank-you panel) and two copies of it in the lint and spec tests. All three parse.
+- **objectui** at the `.objectui-sha` pin `89cad75d55`: 539 `object-form` nodes (the control on 522). Across the four members there are 73 values: 60 are static, and 56 of them parse. The 4 that do not are test fixtures of a protocol-relative redirect (`//example.com/thanks`), each asserting that the form refuses it and navigates nowhere. Of the 13 values that are not static, 9 are relative redirects that parse by inspection, and 4 are redirect fixtures the form refuses (three same-origin absolute URLs and one protocol-relative one). No refused value is one the form draws.
+- **Deployed metadata** was not measured.
diff --git a/content/docs/references/ui/component.mdx b/content/docs/references/ui/component.mdx
index ba4022cdce..7531d2b515 100644
--- a/content/docs/references/ui/component.mdx
+++ b/content/docs/references/ui/component.mdx
@@ -539,7 +539,7 @@ Sort field and direction pair
 | **drawerWidth** | `string \| number` | optional | Drawer width (drawer) |
 | **modalSize** | `Enum<'sm' \| 'default' \| 'lg' \| 'xl' \| 'full'>` | optional | Modal size (modal) |
 | **modalCloseButton** | `boolean` | optional | Show the modal close button (modal) |
-| **contentLayout** | `any` | optional | Modal content layout config (modal) |
+| **contentLayout** | `Enum<'simple' \| 'tabbed'>` | optional | How the modal presentation lays out its sections (modal) — 'simple' stacks them (the default); 'tabbed' puts each section on its own tab once more than one section has a field to show |
 | **confirmOnDiscard** | `boolean` | optional | Confirm before discarding edits (drawer/modal) |
 | **submitText** | `string \| Record<string, string>` | optional | Submit button label |
 | **cancelText** | `string \| Record<string, string>` | optional | Cancel button label |
@@ -548,14 +548,32 @@ Sort field and direction pair
 | **showSubmit** | `boolean` | optional | Show the submit button |
 | **showCancel** | `boolean` | optional | Show the cancel button |
 | **showReset** | `boolean` | optional | Show the reset button |
-| **submitBehavior** | `any` | optional | What happens after a successful submit (`{ kind: 'thank-you' \| …, title?, message? }`) |
+| **submitBehavior** | `{ kind: 'thank-you'; title?: string; message?: string } \| { kind: 'redirect'; url: string; delayMs?: integer } \| { kind: 'continue' } \| { kind: 'next-record' }` | optional | What happens after a successful submit — the same block a form view's `submitBehavior` declares: `{ kind: 'thank-you', title?, message? }`, `{ kind: 'redirect', url, delayMs? }` (a relative `url`, interpolating declared record fields as `{{record.field_name}}`), `{ kind: 'continue' }` or `{ kind: 'next-record' }`. Takes precedence over `navigateOnSuccess` and `resetOnSuccess` |
 | **successMessage** | `string \| Record<string, string>` | optional | Toast message on successful submit |
 | **resetOnSuccess** | `boolean` | optional | Reset the form after a successful submit |
-| **navigateOnSuccess** | `any` | optional | Navigate after a successful submit |
+| **navigateOnSuccess** | `string` | optional | Relative path to navigate to after a successful create/update — `{id}` / `{recordId}` are replaced with the saved record's id, URL-escaped; an absolute URL is refused at submit and reported on the success toast. Ignored when `submitBehavior` is set — prefer `submitBehavior` |
 | **readOnly** | `boolean` | optional | Render every field read-only |
 | **initialValues** | `Record<string, any>` | optional | Prefill values (create mode) |
 | **initialData** | `Record<string, any>` | optional | Alternate spelling of `initialValues` the renderer also reads |
-| **mobile** | `any` | optional | Mobile presentation overrides |
+| **mobile** | `{ stickyActions?: boolean; stepper?: boolean \| 'auto'; stepperMinFields?: integer; stepperFieldsPerStep?: integer; … }` | optional | Phone presentation options, each opt-in — `{ stickyActions?, stepper?, stepperMinFields?, stepperFieldsPerStep?, fullscreenLongText? }`. Read by the flat (simple, sectionless) form |
+
+### Nested Shape: `ObjectFormProps.submitBehavior[kind='redirect']`
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **kind** | `'redirect'` | ✅ |  |
+| **url** | `string` | ✅ | Where the browser goes after a successful submit. Ruled 2026-08-11: (1) RELATIVE paths only — it must start with `/`, and absolute or protocol-relative URLs are refused, which is what closes the open-redirect face; (2) interpolation ONLY from declared record fields, spelled `{{record.field_name}}`, and every interpolated value is URL-escaped when the redirect is built; (3) a verbatim redirect on the resolved relative path is the intended consumption. To send the browser OUT of the app, use an app navigation item (`{ type: 'url', url }`) instead. |
+| **delayMs** | `integer` | optional |  |
+
+### Nested Shape: `ObjectFormProps.mobile`
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **stickyActions** | `boolean` | optional | Pin the submit / cancel bar to the bottom of a phone-width viewport |
+| **stepper** | `boolean \| 'auto'` | optional | One-step-at-a-time wizard for a flat form — `true` always, `'auto'` only on a phone-width viewport once the form has `stepperMinFields` fields, `false` (the default) never |
+| **stepperMinFields** | `integer` | optional | The field count at which `stepper: 'auto'` steps up (default 8) |
+| **stepperFieldsPerStep** | `integer` | optional | Fields shown per stepper step (default 1) |
+| **fullscreenLongText** | `boolean` | optional | Offer a fullscreen editor on textarea and rich-text fields |
 
 
 ---
diff --git a/docs/audits/2026-07-unknown-key-strictness-ledger.counts/ui.md b/docs/audits/2026-07-unknown-key-strictness-ledger.counts/ui.md
index b7dba0b3b2..a2b753ec14 100644
--- a/docs/audits/2026-07-unknown-key-strictness-ledger.counts/ui.md
+++ b/docs/audits/2026-07-unknown-key-strictness-ledger.counts/ui.md
@@ -21,7 +21,7 @@ The `strict` column is the one the campaign schedules against; it counts both th
 
 | Dir | Sites | strict | passthrough | catchall | strip |
 |---|---|---|---|---|---|
-| `ui/` | 191 | 180 | 4 | 0 | 7 |
+| `ui/` | 192 | 181 | 4 | 0 | 7 |
 
 ## `ui/` — sites
 
@@ -36,7 +36,7 @@ classify and is not listed (it becomes reportable the day it grows its first sit
 | `app.zod.ts` | 19 |
 | `bulk-action.zod.ts` | 4 |
 | `chart.zod.ts` | 8 |
-| `component.zod.ts` | 61 |
+| `component.zod.ts` | 62 |
 | `dashboard.zod.ts` | 11 |
 | `dataset.zod.ts` | 4 |
 | `i18n.zod.ts` | 1 |
@@ -46,7 +46,7 @@ classify and is not listed (it becomes reportable the day it grows its first sit
 | `sharing.zod.ts` | 1 |
 | `view.zod.ts` | 60 |
 | `widget.zod.ts` | 1 |
-| **total** | **191** |
+| **total** | **192** |
 
 ## `ui/` — open
 
@@ -54,7 +54,7 @@ Per file, how many of its sites still silently discard unknown keys. The `Class`
 column that decides the bucket split is hand-written in the ledger; the arithmetic
 over it is here.
 
-**7 strip of 191**, in 4 file(s).
+**7 strip of 192**, in 4 file(s).
 
 | File | Strip | Sites |
 |---|---|---|
@@ -62,7 +62,7 @@ over it is here.
 | `app.zod.ts` | 1 | 19 |
 | `view.zod.ts` | 4 | 60 |
 | `widget.zod.ts` | 1 | 1 |
-| **total** | **7** | **191** |
+| **total** | **7** | **192** |
 
 | Bucket | Sites |
 |---|---|
diff --git a/packages/spec/dropped-refinements.baseline.json b/packages/spec/dropped-refinements.baseline.json
index 8b331234f2..f90453139c 100644
--- a/packages/spec/dropped-refinements.baseline.json
+++ b/packages/spec/dropped-refinements.baseline.json
@@ -2,8 +2,8 @@
   "description": "Shrink-only ledger of every PUBLISHED JSON Schema that is STILL WIDER than the Zod type it was generated from, because a rule written as `.refine()` reaches the runtime and not the file (#18670). `z.toJSONSchema()` has no arm for a `custom` check: a plain record, the same record with a `.refine()`, and the same record with an ABORTING `.refine()` all project byte-identically (measured on zod 4.4.3, the version packages/spec resolves). So a document one of these files ACCEPTS can still be refused at parse time, and an author -- or an AI -- validating against packages/spec/json-schema/** finds out a release later. Each `sites` path is a position under that schema at which a refinement is dropped; the same paths are written onto the artifact itself as `x-dropped-refinements`. Item 2 closed the first patterns: a refinement DECLARED through the closed list in src/shared/refinement-projection.ts is emitted into the published file, reads `projected` rather than `dropped`, and its row LEAVES this ledger in the same PR -- which is why the ledger shrinks and never grows on a repair. Every refinement outside that closed list stays here, and adding an arm to the list is a public-contract decision, not a refactor. Hand-edited on purpose and with no `gen:` script: a generator would let a new gap be admitted by running a command instead of by a decision, which is the silence this ledger exists to end. Adding, removing or moving a site fails packages/spec/scripts/build-schemas.ts until the line moves with it, and the failure prints the corrected entry in full. ⛔ Do not delete or weaken a refinement to shorten this file -- the runtime rule is correct; it is the projection that is silent, and the remedy is to teach the closed list a NAMED pattern, never to drop the rule.",
   "measured": {
     "zod": "4.4.3",
-    "publishedSchemasWithDroppedRefinements": 217,
-    "droppedRefinementSites": 653,
+    "publishedSchemasWithDroppedRefinements": 218,
+    "droppedRefinementSites": 654,
     "refinementSitesThatDidProject": 369,
     "refinementSitesWithNoJsonFormToCompare": 0
   },
@@ -1364,6 +1364,11 @@
         "filter.element"
       ]
     },
+    "ui/ObjectFormProps": {
+      "sites": [
+        "submitBehavior.options[1].url"
+      ]
+    },
     "ui/ObjectGanttProps": {
       "sites": [
         "filter.element",
diff --git a/packages/spec/src/migrations/entries/semantic/18.ui-object-form-members-typed.ts b/packages/spec/src/migrations/entries/semantic/18.ui-object-form-members-typed.ts
new file mode 100644
index 0000000000..a579243d97
--- /dev/null
+++ b/packages/spec/src/migrations/entries/semantic/18.ui-object-form-members-typed.ts
@@ -0,0 +1,53 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+import type { SemanticMigration } from '../../types.js';
+
+// #21464 — four members of the `object-form` page block were `z.unknown()`
+// although the form reads each with a fixed shape, so an off-shape value passed
+// the component-props gate and the form fell back or ignored it in silence. The
+// row now takes the form view's own `submitBehavior` by reference and the
+// measured shape for `contentLayout`, `navigateOnSuccess` and `mobile`. The
+// form's `fields` and `sections` and the master-detail form's two are held at
+// `z.unknown()` (the form draws a `{ name }` field entry and an inline runtime
+// field inside a section, which the typed shapes would refuse), and
+// `customFields` waits for the spec to declare objectui's runtime form field.
+// D3 only: page-component `properties` is not parsed on the metadata save or
+// load path, so a stored page is never refused; an off-shape value has no
+// rewrite that says what the author meant; and the authored census found no
+// authored value to respell — the refused values are fixtures probing that the
+// form refuses them.
+export const entry: SemanticMigration = {
+  id: 'ui-object-form-members-typed',
+  surface: 'page `object-form` components — `properties.contentLayout`, `.submitBehavior`, '
+    + '`.navigateOnSuccess` and `.mobile` (which used to accept any value)',
+  replacement: 'the shape the form reads: `contentLayout` `\'simple\'` or `\'tabbed\'`; `submitBehavior` the '
+    + 'form view\'s own block — `{ kind: \'thank-you\', title?, message? }`, `{ kind: \'redirect\', url, '
+    + 'delayMs? }` with a relative `url`, `{ kind: \'continue\' }` or `{ kind: \'next-record\' }`; '
+    + '`navigateOnSuccess` a relative path string; `mobile` `{ stickyActions?, stepper?, stepperMinFields?, '
+    + 'stepperFieldsPerStep?, fullscreenLongText? }`, with `stepper` `true`, `false` or `\'auto\'` and the two '
+    + 'counts positive integers. Write a `submitBehavior` `kind` as one of the four; move a `redirect` '
+    + 'destination to a relative path; write `heading` as `title`.',
+  reason: 'The form reads these members with one shape, and the page-component row declared them '
+    + '`z.unknown()`, so any value passed the component-props gate and the form answered an off-shape one '
+    + 'with a silent default: a `submitBehavior` `kind` it does not know fell through to the thank-you panel; '
+    + 'a misspelled `contentLayout` such as `\'tabs\'` stacked the sections; a `navigateOnSuccess` that is not a '
+    + 'string threw after the record was written, so the submit reported a failure; and a `mobile` member it '
+    + 'does not read, or a `stepper` outside `true` / `false` / `\'auto\'`, was ignored. The row now takes '
+    + 'the form view\'s own `submitBehavior` by reference — the block the renderers already judge a redirect '
+    + '`url` through — so one value is judged the same way on the form view and the block, and the measured '
+    + 'shape for the other three. The form\'s `fields` and `sections` and the master-detail form\'s two stay '
+    + 'open, because the form draws a `{ name }` field entry and an inline runtime field inside a section, '
+    + 'which the typed shapes would refuse; and `customFields` stays open until the spec declares the '
+    + 'runtime form field its entries are. It is read where every page component\'s props are: the '
+    + 'component-props gate reports a refused value as an advisory `component-props-invalid` / '
+    + '`component-props-unknown-key` finding on `objectstack validate`, `objectstack build` and '
+    + '`objectstack lint`, and a stored page still saves and loads, because a page component\'s '
+    + '`properties` is not parsed on the metadata save or load path. No conversion is registered: nothing '
+    + 'on the load path refuses the shape, and an off-shape value has no rewrite that both keeps what the '
+    + 'form shows today and honours what the author wrote — which is the judgment this entry leaves to the '
+    + 'upgrader. Deployed metadata NOT MEASURED.',
+  acceptanceCriteria: 'Every `object-form` node validates: `objectstack validate` reports no '
+    + '`component-props-invalid` / `component-props-unknown-key` finding under the four members\' paths. '
+    + 'Each form that set one of them now shows it: the post-submit behaviour it names, the modal\'s tabbed '
+    + 'sections, the navigation after a save, and the phone presentation.',
+};
diff --git a/packages/spec/src/migrations/registry.ts b/packages/spec/src/migrations/registry.ts
index d4adb357c6..09cc405144 100644
--- a/packages/spec/src/migrations/registry.ts
+++ b/packages/spec/src/migrations/registry.ts
@@ -6138,6 +6138,22 @@ const STEP18_RATIONALE: readonly RationaleFragment[] = [
       + '`columns` untouched) on `object-form` page components, on every form payload a view '
       + 'carries, and on the assembled-manifest `viewItems` channel.',
   },
+  {
+    id: 'ui-object-form-members-typed',
+    order: 67,
+    text:
+      'It also types four members of the `object-form` page block (#21464, the third stage of the '
+      + '`ComponentPropsMap` `z.unknown()` close-out): `contentLayout`, `submitBehavior`, '
+      + '`navigateOnSuccess` and `mobile` were `z.unknown()`, although the form reads each with one shape, '
+      + 'so a `submitBehavior` `kind` the form does not know passed every door and fell through to the '
+      + 'thank-you panel. `submitBehavior` takes the form view\'s own block by reference; the other three '
+      + 'take the measured shape. The form\'s `fields` and `sections` and the master-detail form\'s two '
+      + 'stay open — the form draws a `{ name }` field entry and an inline runtime field inside a section, '
+      + 'which the typed shapes would refuse — and `customFields` stays open until the spec declares the '
+      + 'runtime form field its entries are. Read by the component-props gate (advisory); a stored page '
+      + 'still saves and loads, so no conversion is registered. Its D3 record is the semantic entry '
+      + '`ui-object-form-members-typed`.',
+  },
   {
     id: 'ui-object-grid-export-options-closed',
     order: 59,
@@ -19479,6 +19495,55 @@ const step18: MigrationStep = {
         + 'group per value of that field, and a board that showed one swimlane shows one swimlane per value — '
         + 'check that this is the grouping you meant.',
     },
+    // #21464 — four members of the `object-form` page block were `z.unknown()`
+    // although the form reads each with a fixed shape, so an off-shape value passed
+    // the component-props gate and the form fell back or ignored it in silence. The
+    // row now takes the form view's own `submitBehavior` by reference and the
+    // measured shape for `contentLayout`, `navigateOnSuccess` and `mobile`. The
+    // form's `fields` and `sections` and the master-detail form's two are held at
+    // `z.unknown()` (the form draws a `{ name }` field entry and an inline runtime
+    // field inside a section, which the typed shapes would refuse), and
+    // `customFields` waits for the spec to declare objectui's runtime form field.
+    // D3 only: page-component `properties` is not parsed on the metadata save or
+    // load path, so a stored page is never refused; an off-shape value has no
+    // rewrite that says what the author meant; and the authored census found no
+    // authored value to respell — the refused values are fixtures probing that the
+    // form refuses them.
+    {
+      id: 'ui-object-form-members-typed',
+      surface: 'page `object-form` components — `properties.contentLayout`, `.submitBehavior`, '
+        + '`.navigateOnSuccess` and `.mobile` (which used to accept any value)',
+      replacement: 'the shape the form reads: `contentLayout` `\'simple\'` or `\'tabbed\'`; `submitBehavior` the '
+        + 'form view\'s own block — `{ kind: \'thank-you\', title?, message? }`, `{ kind: \'redirect\', url, '
+        + 'delayMs? }` with a relative `url`, `{ kind: \'continue\' }` or `{ kind: \'next-record\' }`; '
+        + '`navigateOnSuccess` a relative path string; `mobile` `{ stickyActions?, stepper?, stepperMinFields?, '
+        + 'stepperFieldsPerStep?, fullscreenLongText? }`, with `stepper` `true`, `false` or `\'auto\'` and the two '
+        + 'counts positive integers. Write a `submitBehavior` `kind` as one of the four; move a `redirect` '
+        + 'destination to a relative path; write `heading` as `title`.',
+      reason: 'The form reads these members with one shape, and the page-component row declared them '
+        + '`z.unknown()`, so any value passed the component-props gate and the form answered an off-shape one '
+        + 'with a silent default: a `submitBehavior` `kind` it does not know fell through to the thank-you panel; '
+        + 'a misspelled `contentLayout` such as `\'tabs\'` stacked the sections; a `navigateOnSuccess` that is not a '
+        + 'string threw after the record was written, so the submit reported a failure; and a `mobile` member it '
+        + 'does not read, or a `stepper` outside `true` / `false` / `\'auto\'`, was ignored. The row now takes '
+        + 'the form view\'s own `submitBehavior` by reference — the block the renderers already judge a redirect '
+        + '`url` through — so one value is judged the same way on the form view and the block, and the measured '
+        + 'shape for the other three. The form\'s `fields` and `sections` and the master-detail form\'s two stay '
+        + 'open, because the form draws a `{ name }` field entry and an inline runtime field inside a section, '
+        + 'which the typed shapes would refuse; and `customFields` stays open until the spec declares the '
+        + 'runtime form field its entries are. It is read where every page component\'s props are: the '
+        + 'component-props gate reports a refused value as an advisory `component-props-invalid` / '
+        + '`component-props-unknown-key` finding on `objectstack validate`, `objectstack build` and '
+        + '`objectstack lint`, and a stored page still saves and loads, because a page component\'s '
+        + '`properties` is not parsed on the metadata save or load path. No conversion is registered: nothing '
+        + 'on the load path refuses the shape, and an off-shape value has no rewrite that both keeps what the '
+        + 'form shows today and honours what the author wrote — which is the judgment this entry leaves to the '
+        + 'upgrader. Deployed metadata NOT MEASURED.',
+      acceptanceCriteria: 'Every `object-form` node validates: `objectstack validate` reports no '
+        + '`component-props-invalid` / `component-props-unknown-key` finding under the four members\' paths. '
+        + 'Each form that set one of them now shows it: the post-submit behaviour it names, the modal\'s tabbed '
+        + 'sections, the navigation after a save, and the phone presentation.',
+    },
     // #21229 — an `object-grid` page block's `exportOptions` was `z.unknown()`, so a
     // bare format array (the list view's legacy spelling, which the list view lifts
     // to `{ formats }`) was accepted on the grid, whose renderer reads
diff --git a/packages/spec/src/ui/component-form-family-typed-members.pin.test.ts b/packages/spec/src/ui/component-form-family-typed-members.pin.test.ts
new file mode 100644
index 0000000000..8dbaa06bc6
--- /dev/null
+++ b/packages/spec/src/ui/component-form-family-typed-members.pin.test.ts
@@ -0,0 +1,175 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#21464, stage 3] Four of the form family's nine `z.unknown()` members are
+ * typed: `object-form` `contentLayout`, `submitBehavior`, `navigateOnSuccess`
+ * and `mobile`. The other five stay in the enumeration pin's ledger: the
+ * form's `fields` and `sections` and the master-detail form's two are held,
+ * because the form draws a value each typed shape would refuse (a `{ name }`
+ * field entry; an inline runtime field inside a section), and `customFields`
+ * waits with the objectui-held contracts (its entries are objectui's runtime
+ * `FormField`, which the spec has not declared).
+ *
+ * ## The defect this file closes
+ *
+ * Each of the four is read with one shape (measured at the `.objectui-sha` pin
+ * `89cad75d55`; the read points are in the members' docblocks), and the row
+ * declared them `z.unknown()`. So a `submitBehavior` whose `kind` the form does
+ * not know, a `contentLayout: 'tabs'`, a numeric `navigateOnSuccess` and a
+ * misspelled `mobile` member all passed the component-props gate, and the form
+ * fell back to its thank-you panel, stacked the sections, threw after the
+ * record was written, or ignored the key — with no report.
+ *
+ * ## What is pinned, and why each half
+ *
+ * - §1 THE DECLARED SHAPES PARSE: every shape a measured writer authors parses
+ *   byte-identical — none of the four carries a default, so the parsed value
+ *   IS the authored one. A refusal pin with no lit control passes just as well
+ *   when the door refuses everything.
+ * - §2 THE REFUSALS: an off-shape value of each member is refused with the
+ *   code AND the path, so a refusal for the wrong reason reds.
+ * - §3 ONE SCHEMA: `submitBehavior` holds the form view's own def by identity,
+ *   and the two shapes declared here hold exactly the measured vocabulary.
+ * - §4 THE REGISTRATION: the ADR-0087 D3 entry step 18 carries.
+ *
+ * The enumeration pin (`component-props-unknown-members.pin.test.ts`) holds the
+ * other half: these four left its ledger, so a member reverted to
+ * `z.unknown()` reds there.
+ */
+
+import { describe, it, expect } from 'vitest';
+import type { z } from 'zod';
+
+import { ComponentPropsMap, ObjectFormPropsSchema } from './component.zod';
+import { FormViewSchema } from './view.zod';
+import { MIGRATIONS_BY_MAJOR } from '../migrations/registry';
+
+const BASE = { objectName: 'account' } as const;
+const parse = (props: Record<string, unknown>) => ComponentPropsMap['object-form'].safeParse({ ...BASE, ...props });
+
+/** The issue codes and paths a refusal carries, so a refusal for the WRONG reason reds. */
+function issues(result: z.ZodSafeParseResult<unknown>): { code: string; path: string }[] {
+  if (result.success) return [];
+  return result.error.issues.map((i) => ({ code: i.code, path: i.path.join('.') }));
+}
+
+// ───────────────────────────────────────────────────────────────────────────
+// §1 the declared shapes parse
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§1 each member accepts every shape a measured writer authors', () => {
+  const BYTE_IDENTICAL: ReadonlyArray<readonly [label: string, props: Record<string, unknown>]> = [
+    ['contentLayout \'tabbed\'', { contentLayout: 'tabbed' }],
+    ['contentLayout \'simple\'', { contentLayout: 'simple' }],
+    // The showcase's own wizard page (`examples/app-showcase/src/ui/pages/new-project-wizard.page.ts`).
+    ['a thank-you panel with a title and a message', {
+      submitBehavior: { kind: 'thank-you', title: 'Project created', message: 'Your new project is ready.' },
+    }],
+    ['a bare thank-you panel', { submitBehavior: { kind: 'thank-you' } }],
+    ['a relative redirect with a delay', { submitBehavior: { kind: 'redirect', url: '/apps/x/done', delayMs: 241 } }],
+    ['a redirect interpolating declared record fields', {
+      submitBehavior: { kind: 'redirect', url: '/t/{{record.slug}}?ref={{record.id}}' },
+    }],
+    ['continue', { submitBehavior: { kind: 'continue' } }],
+    ['next-record', { submitBehavior: { kind: 'next-record' } }],
+    ['a navigateOnSuccess template', { navigateOnSuccess: '/apps/x/o/record/{id}' }],
+    ['mobile fullscreenLongText', { mobile: { fullscreenLongText: true } }],
+    ['mobile stickyActions', { mobile: { stickyActions: true } }],
+    ['an empty mobile block (its presence marks the wrapper)', { mobile: {} }],
+    ['mobile stepper true with a minimum', { mobile: { stepper: true, stepperMinFields: 99 } }],
+    ['mobile stepper auto with a minimum', { mobile: { stepper: 'auto', stepperMinFields: 3 } }],
+    ['mobile stepper with fields per step', { mobile: { stepper: true, stepperFieldsPerStep: 2 } }],
+    ['mobile stepper false', { mobile: { stepper: false } }],
+  ];
+
+  for (const [label, props] of BYTE_IDENTICAL) {
+    it(`parses ${label}, byte-identical`, () => {
+      const r = parse(props);
+      expect(issues(r)).toEqual([]);
+      expect(r.success && r.data).toStrictEqual({ ...BASE, ...props });
+    });
+  }
+
+  it('an absent member stays absent', () => {
+    const r = parse({});
+    expect(issues(r)).toEqual([]);
+    expect(r.success && Object.keys(r.data)).toEqual(['objectName']);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §2 the refusals
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§2 each member refuses an off-shape value', () => {
+  const REFUSED: ReadonlyArray<readonly [label: string, props: Record<string, unknown>, code: string, path: string]> = [
+    ['a contentLayout outside the two', { contentLayout: 'tabs' }, 'invalid_value', 'contentLayout'],
+    ['a contentLayout object', { contentLayout: { mode: 'tabbed' } }, 'invalid_value', 'contentLayout'],
+    ['a submitBehavior kind the form does not know', { submitBehavior: { kind: 'toast' } }, 'invalid_union', 'submitBehavior.kind'],
+    ['a submitBehavior with no kind', { submitBehavior: { title: 'Done' } }, 'invalid_union', 'submitBehavior.kind'],
+    ['a bare-string submitBehavior', { submitBehavior: 'thank-you' }, 'invalid_type', 'submitBehavior'],
+    ['a protocol-relative redirect', { submitBehavior: { kind: 'redirect', url: '//example.com/thanks' } }, 'custom', 'submitBehavior.url'],
+    ['an absolute redirect', { submitBehavior: { kind: 'redirect', url: 'https://app.example.com/thanks' } }, 'custom', 'submitBehavior.url'],
+    ['a negative redirect delay', { submitBehavior: { kind: 'redirect', url: '/done', delayMs: -1 } }, 'too_small', 'submitBehavior.delayMs'],
+    ['a thank-you `heading`', { submitBehavior: { kind: 'thank-you', heading: 'Done' } }, 'unrecognized_keys', 'submitBehavior'],
+    ['options on continue', { submitBehavior: { kind: 'continue', title: 'Again' } }, 'unrecognized_keys', 'submitBehavior'],
+    ['a numeric navigateOnSuccess', { navigateOnSuccess: 42 }, 'invalid_type', 'navigateOnSuccess'],
+    ['an object navigateOnSuccess', { navigateOnSuccess: { url: '/x' } }, 'invalid_type', 'navigateOnSuccess'],
+    ['a stepper outside true / false / auto', { mobile: { stepper: 'yes' } }, 'invalid_union', 'mobile.stepper'],
+    ['a mobile member the form does not read', { mobile: { sticky: true } }, 'unrecognized_keys', 'mobile'],
+    ['zero fields per step', { mobile: { stepper: true, stepperFieldsPerStep: 0 } }, 'too_small', 'mobile.stepperFieldsPerStep'],
+    ['a fractional minimum', { mobile: { stepperMinFields: 2.5 } }, 'invalid_type', 'mobile.stepperMinFields'],
+    ['a boolean mobile', { mobile: true }, 'invalid_type', 'mobile'],
+  ];
+
+  for (const [label, props, code, path] of REFUSED) {
+    it(`refuses ${label} — ${code} at ${path}`, () => {
+      const r = parse(props);
+      expect(r.success).toBe(false);
+      expect(issues(r)).toEqual([{ code, path }]);
+    });
+  }
+
+  it('says a thank-you `heading` is its `title`', () => {
+    const r = parse({ submitBehavior: { kind: 'thank-you', heading: 'Done' } });
+    expect(r.success ? '' : r.error.issues[0]!.message).toMatch(/`heading` → `title`/);
+  });
+
+  it('LIT CONTROL — an unknown top-level key is still refused at the row itself', () => {
+    expect(issues(parse({ contentLayout: 'tabbed', notAFormKey: 1 }))).toEqual([{ code: 'unrecognized_keys', path: '' }]);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §3 one schema, not a copy of its shape
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§3 the members hold the form view\'s own def, and the measured vocabulary', () => {
+  const form = () => ObjectFormPropsSchema.shape;
+
+  it('submitBehavior is the form view\'s own member — the same def', () => {
+    expect(form().submitBehavior.unwrap()._zod.def).toBe(FormViewSchema.shape.submitBehavior.unwrap()._zod.def);
+  });
+
+  it('contentLayout declares exactly the read\'s two layouts', () => {
+    expect([...form().contentLayout.unwrap().options].sort()).toEqual(['simple', 'tabbed']);
+  });
+
+  it('a mobile block declares exactly the five members the form reads', () => {
+    expect(Object.keys(form().mobile.unwrap().shape).sort())
+      .toEqual(['fullscreenLongText', 'stepper', 'stepperFieldsPerStep', 'stepperMinFields', 'stickyActions']);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §4 the registration
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§4 the ADR-0087 entry', () => {
+  it('is registered as the D3 entry step 18 carries, beside the earlier stages\' entries', () => {
+    const ids = MIGRATIONS_BY_MAJOR[18]!.semantic.map((s) => s.id);
+    expect(ids).toContain('ui-object-form-members-typed');
+    expect(ids).toContain('ui-object-grid-kanban-calendar-list-members-typed');
+    expect(ids).toContain('ui-object-map-gantt-tree-navigation-typed');
+  });
+});
diff --git a/packages/spec/src/ui/component-props-unknown-members.pin.test.ts b/packages/spec/src/ui/component-props-unknown-members.pin.test.ts
index 3938c5e1d3..9671e85282 100644
--- a/packages/spec/src/ui/component-props-unknown-members.pin.test.ts
+++ b/packages/spec/src/ui/component-props-unknown-members.pin.test.ts
@@ -35,7 +35,11 @@
  * `rowActions` / `bulkActions` / `batchActions`, `object-kanban` `columns`,
  * `object-calendar` `calendar`) in
  * `component-list-family-typed-members.pin.test.ts`. The family's ninth,
- * `object-grid` `columns`, is held below.
+ * `object-grid` `columns`, is held below. The form family (`object-form`
+ * `contentLayout` / `submitBehavior` / `navigateOnSuccess` / `mobile`) in
+ * `component-form-family-typed-members.pin.test.ts`; its `fields` and
+ * `sections`, and the master-detail form's two, are held below, and its
+ * `customFields` waits with the objectui-held contracts.
  *
  * ## The STAGED reason is debt, not a verdict
  *
@@ -124,9 +128,8 @@ function unknownMembers(schema: unknown): UnknownMember[] {
  */
 const STAGES = {
   'object-metric': 'the metric tile\'s four config blocks; the dashboard widget\'s `compareTo` and the chart\'s `aggregate` / `drillDown` are the by-reference candidates, and `trend` has no spec declaration, so it is typed to the renderer\'s read',
-  'object-form': 'the form and master-detail form rows; `FormViewSchema` (`sections`, `submitBehavior`) is the by-reference candidate',
-  'objectui-held': 'element contracts whose only declaration is still objectui\'s (`GanttMarker`, `TimelineMappingSchema`, the timeline items, and `UIActionSchema`, an objectui interface that borrows some members from the spec `Action`); the spec declares each first, contract-first, then the row takes it',
-  'held-for-decision': 'a by-reference shape exists, but measured writers author values it refuses — the narrowing waits for a ruling',
+  'objectui-held': 'element contracts whose only declaration is still objectui\'s (`GanttMarker`, `TimelineMappingSchema`, the timeline items, `UIActionSchema` — an objectui interface that borrows some members from the spec `Action` — and the runtime form field `FormField`, identity key `name`); the spec declares each first, contract-first, then the row takes it',
+  'held-for-decision': 'a typed shape exists (by reference, or the renderer\'s own declared type), but measured writers author values it refuses that the renderer draws — the narrowing waits for a ruling',
 } as const;
 type Stage = keyof typeof STAGES;
 
@@ -227,14 +230,11 @@ on(['object-metric'], ['aggregate'], staged('object-metric', 'plugin-dashboard/s
 on(['object-metric'], ['trend'], staged('object-metric', 'plugin-dashboard/src/ObjectMetricWidget.tsx:254 (typed :176)'));
 on(['object-metric'], ['drillDown'], staged('object-metric', 'plugin-dashboard/src/ObjectMetricWidget.tsx:265 (`ObjectMetricDrillDownConfig`, :218)'));
 on(['object-metric'], ['compareTo'], staged('object-metric', 'plugin-dashboard/src/ObjectMetricWidget.tsx:267 (`CompareToConfig`, :241)'));
-on(['object-form'], ['fields[]'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:961'));
-on(['object-form'], ['customFields'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:755, :1180'));
-on(['object-form'], ['sections[]'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:364, :1518'));
-on(['object-form'], ['contentLayout'], staged('object-form', 'plugin-form/src/ModalForm.tsx:854 (`\'simple\' | \'tabbed\'`, :151)'));
-on(['object-form'], ['submitBehavior'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:1312-1313'));
-on(['object-form'], ['navigateOnSuccess'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:1373, :1412-1424'));
-on(['object-form'], ['mobile'], staged('object-form', 'plugin-form/src/ObjectForm.tsx:1857'));
-on(['object-master-detail-form'], ['sections[]', 'fields[]'], staged('object-form', 'plugin-form/src/MasterDetailForm.tsx:1692-1693, into the parent form'));
+// The form's inline members are objectui's runtime form field (`FormField`,
+// identity key `name`), merged over the generated set and drawn whole; the spec
+// declares no such field — its own form field is keyed by `field`, and the
+// merge never matches it — so the spec declares that contract first.
+on(['object-form'], ['customFields'], staged('objectui-held', 'plugin-form/src/customFieldsMerge.ts:78-108 (`FormField`, by `name`), from ObjectForm.tsx:755, :1180'));
 on(['object-gantt'], ['markers[]'], staged('objectui-held', 'plugin-gantt/src/ObjectGantt.tsx:2497 (`GanttMarker`)'));
 on(['object-timeline'], ['items[]'], staged('objectui-held', 'plugin-timeline/src/ObjectTimeline.tsx:587'));
 on(['object-timeline'], ['mapping'], staged('objectui-held', 'plugin-timeline/src/ObjectTimeline.tsx:551, :576-579'));
@@ -255,6 +255,27 @@ on(['object-kanban'], ['conditionalFormatting'], staged('held-for-decision', 'pl
 // `ListColumn` declares no `options`, so the narrowing would refuse a value the
 // grid draws: held until objectstack-ai/objectui#11544 is ruled.
 on(['object-grid'], ['columns[]'], staged('held-for-decision', 'plugin-grid/src/ObjectGrid.tsx:2158 (`normalizeColumns`), `columns[].options` drawn by the group-header formatter at :2997-3001'));
+// The renderer's own declared type for the form's `fields` is field-name
+// strings (`ObjectFormSchema.fields: string[]`), but its read also draws a
+// `{ name }` entry by that name, and measured writers author one: objectui's
+// published page-builder guide (`skills/objectui/guides/page-builder.md:263`),
+// its field-security and system-managed payload pins, and the `{ name }` row it
+// pins as behaviour (`plugin-form/src/__tests__/objectFormFieldsMembers-8071.test.tsx:165-167`).
+// Typing the member to strings would refuse a value the form draws.
+on(['object-form'], ['fields[]'], staged('held-for-decision', 'plugin-form/src/ObjectForm.tsx:961-981 and flatFields.ts:71-79, a `{ name }` entry drawn by that name'));
+// The form view's own `sections` is the by-reference shape, and every section
+// key the form reads is declared there — but a section's `fields` also draws an
+// inline runtime form field `{ name, type, … }` as it stands ("shape 3"), which
+// the form view's field entry (keyed by `field`) refuses; objectui's README
+// (`plugin-form/README.md:764`) and its submit-target pins
+// (`plugin-form/src/submitTargetRefusal.test.tsx:331-358`) author that shape
+// and assert that it renders and submits.
+on(['object-form'], ['sections[]'], staged('held-for-decision', 'plugin-form/src/sectionFields.ts:367-369 (shape 3), reached from ObjectForm.tsx:364, :1518 and every sectioned arm'));
+// The master-detail form hands both to its parent `object-form` verbatim, so
+// each is read exactly as that block's member is, and held with it; its own
+// `fields` writers author the `{ name }` entry too
+// (`plugin-form/src/__tests__/topLevelFieldsWarnCoverage-8847.test.tsx:254-257`).
+on(['object-master-detail-form'], ['sections[]', 'fields[]'], staged('held-for-decision', 'plugin-form/src/MasterDetailForm.tsx:1692-1693, into the parent form, read as `object-form`\'s'));
 
 /** Every `z.unknown()` member of every row, keyed as the ledger keys it. */
 function census(): Map<string, UnknownMember> {
diff --git a/packages/spec/src/ui/component.zod.ts b/packages/spec/src/ui/component.zod.ts
index 285edfb205..2594178cfc 100644
--- a/packages/spec/src/ui/component.zod.ts
+++ b/packages/spec/src/ui/component.zod.ts
@@ -34,6 +34,11 @@ import {
   RowHeightSchema,
   RowColorConfigSchema,
   ListViewSchema,
+  // [#21464] `object-form.submitBehavior` is the form view's own member (read
+  // off `FormViewSchema.shape`, the one place that declares the post-submit
+  // union): both form renderers switch on exactly that union, so one
+  // declaration judges the form view and the block.
+  FormViewSchema,
 } from './view.zod';
 // [#21445] `object-grid.bulkActionDefs` is the list view's bulk-action def,
 // by identity — the element `ListViewSchema.bulkActionDefs` declares.
@@ -5283,6 +5288,44 @@ const OBJECT_FORM_LAYOUT_RETIRED: ReadonlyMap<string, string> = new Map([
     + 'Run `os migrate meta --from 17` to list the mechanical edits for existing sources; apply them by hand.'],
 ]);
 
+/**
+ * [#21464] An `object-form`'s `mobile` block — the five members the form reads
+ * at the `.objectui-sha` pin `89cad75d55` (`plugin-form/src/ObjectForm.tsx:1857-1942`,
+ * the flat arm only), and nothing else. No form view declares the block, so
+ * the shape is the read's own, as objectui declares it (`ObjectFormSchema.mobile`):
+ *
+ * - `stickyActions` pins the submit / cancel bar to the bottom of the viewport
+ *   (`:1935`, `:1941`);
+ * - `stepper` routes a flat form through the wizard: `true` always (a desktop
+ *   viewport included), `'auto'` only on a phone-width viewport once the form
+ *   has `stepperMinFields` fields (`:1874-1884`, default 8);
+ *   `stepperFieldsPerStep` is the fields per step (`:1876`, default 1 — the
+ *   read clamps a smaller count to 1);
+ * - `fullscreenLongText` offers the fullscreen editor on every long-text field
+ *   (`:1858-1869`).
+ *
+ * The block's presence marks the wrapper (`data-mobile-form`, `:1942`), so an
+ * empty `{}` is legal and changes nothing else. Module-private, as
+ * {@link ObjectKanbanLaneSchema} is.
+ */
+const ObjectFormMobileSchema = lazySchema(() => strictObject({
+  surface: 'this `object-form` `mobile` block',
+  history:
+    'Until this shape was declared, `mobile` was `z.unknown()`: a misspelled member or a `stepper` '
+    + 'value outside `true` / `false` / `\'auto\'` passed, and the form rendered without it.',
+}, {
+  stickyActions: z.boolean().optional()
+    .describe('Pin the submit / cancel bar to the bottom of a phone-width viewport'),
+  stepper: z.union([z.boolean(), z.literal('auto')]).optional()
+    .describe("One-step-at-a-time wizard for a flat form — `true` always, `'auto'` only on a phone-width viewport once the form has `stepperMinFields` fields, `false` (the default) never"),
+  stepperMinFields: z.number().int().positive().optional()
+    .describe("The field count at which `stepper: 'auto'` steps up (default 8)"),
+  stepperFieldsPerStep: z.number().int().positive().optional()
+    .describe('Fields shown per stepper step (default 1)'),
+  fullscreenLongText: z.boolean().optional()
+    .describe('Offer a fullscreen editor on textarea and rich-text fields'),
+}));
+
 /**
  * `object-form` (objectui `plugin-form/src/ObjectForm.tsx` @ `eb7f586b`, plus
  * the sub-forms it forwards the whole bag into: `TabbedForm`, `WizardForm`,
@@ -5318,8 +5361,36 @@ export const ObjectFormPropsSchema = lazySchema(() => strictObject({
   }).optional()
     .describe("Field layout — 'vertical' (the renderer default) or 'horizontal'. Multi-column is not a layout value: set `columns`"),
   columns: z.number().optional().describe('Number of field columns (multi-column forms), honoured under either `layout`'),
+  /**
+   * [#21464] HELD at `z.unknown()` entries, in the enumeration pin's ledger as
+   * held for a ruling. The renderer's own declared type is field-name strings
+   * (objectui `ObjectFormSchema.fields: string[]`), but its read also draws a
+   * `{ name }` entry by that name (`plugin-form/src/ObjectForm.tsx:961-981`,
+   * `flatFields.ts:71-79` at the pin `89cad75d55`), and measured writers author
+   * one — objectui's published page-builder guide among them — so typing the
+   * member to strings would refuse a value the form draws.
+   */
   fields: z.array(z.unknown()).optional().describe('Limit/order the fields shown'),
+  /**
+   * [#21464] Kept `z.unknown()`, in the enumeration pin's ledger with the
+   * objectui-held contracts: each member is objectui's runtime form field
+   * (`FormField`, identity key `name`), drawn whole by the form renderer
+   * (`plugin-form/src/customFieldsMerge.ts:78-108` at the pin `89cad75d55`).
+   * The spec declares no such field — its own form field (`FormFieldSchema`,
+   * `view.zod.ts`) is keyed by `field` and is never matched by the merge — so
+   * the spec declares that contract first, then this member takes it.
+   */
   customFields: z.unknown().optional().describe('Custom field definitions merged into the generated set'),
+  /**
+   * [#21464] HELD at `z.unknown()` entries, in the enumeration pin's ledger as
+   * held for a ruling. The form view's own `sections` (`FormSectionSchema`) is
+   * the by-reference shape, and every section key the renderer reads is
+   * declared there, but a section's `fields` also draws an inline runtime form
+   * field `{ name, type, … }` as it stands (`plugin-form/src/sectionFields.ts:367-369`
+   * at the pin `89cad75d55`, its "shape 3"), which the form view's field entry
+   * (keyed by `field`) refuses; objectui's README and its own pins author that
+   * shape and assert that it renders and submits.
+   */
   sections: z.array(z.unknown()).optional()
     .describe('Form sections ({ label, description?, fields } — wizard steps / tab panes)'),
   title: I18nLabelSchema.optional().describe('Form title'),
@@ -5335,7 +5406,15 @@ export const ObjectFormPropsSchema = lazySchema(() => strictObject({
   drawerWidth: z.union([z.string(), z.number()]).optional().describe('Drawer width (drawer)'),
   modalSize: z.enum(['sm', 'default', 'lg', 'xl', 'full']).optional().describe('Modal size (modal)'),
   modalCloseButton: z.boolean().optional().describe('Show the modal close button (modal)'),
-  contentLayout: z.unknown().optional().describe('Modal content layout config (modal)'),
+  /**
+   * [#21464] Typed to the read: the modal presentation is its only reader,
+   * and it tests `schema.contentLayout === 'tabbed' && groups.length > 1`
+   * (`plugin-form/src/ModalForm.tsx:854` at the pin `89cad75d55`, declared
+   * `'simple' | 'tabbed'` at `:151`); any other value stacks the sections, so
+   * a misspelled `'tabs'` used to draw the stacked layout with no report.
+   */
+  contentLayout: z.enum(['simple', 'tabbed']).optional()
+    .describe("How the modal presentation lays out its sections (modal) — 'simple' stacks them (the default); 'tabbed' puts each section on its own tab once more than one section has a field to show"),
   confirmOnDiscard: z.boolean().optional().describe('Confirm before discarding edits (drawer/modal)'),
   submitText: I18nLabelSchema.optional().describe('Submit button label'),
   cancelText: I18nLabelSchema.optional().describe('Cancel button label'),
@@ -5344,15 +5423,42 @@ export const ObjectFormPropsSchema = lazySchema(() => strictObject({
   showSubmit: z.boolean().optional().describe('Show the submit button'),
   showCancel: z.boolean().optional().describe('Show the cancel button'),
   showReset: z.boolean().optional().describe('Show the reset button'),
-  submitBehavior: z.unknown().optional()
-    .describe("What happens after a successful submit ({ kind: 'thank-you' | …, title?, message? })"),
+  /**
+   * [#21464] The form view's own `submitBehavior` member, by reference
+   * (`FormViewSchema.shape.submitBehavior`, the union discriminated on
+   * `kind`). Both form renderers switch on `kind` and read exactly that
+   * union's members — `url` and `delayMs` on `redirect`, `title` and `message`
+   * on `thank-you` (`plugin-form/src/ObjectForm.tsx:1312-1370` and
+   * `WizardForm.tsx:1005-1065` at the pin `89cad75d55`) — and judge a redirect
+   * `url` at submit by parsing a form view through this same schema
+   * (`submitRedirect.ts:202`), so one declaration judges the form view, this
+   * block and the renderer's own verdict. A `kind` outside the four fell
+   * through to the thank-you arm in silence.
+   */
+  submitBehavior: FormViewSchema.shape.submitBehavior
+    .describe("What happens after a successful submit — the same block a form view's `submitBehavior` declares: `{ kind: 'thank-you', title?, message? }`, `{ kind: 'redirect', url, delayMs? }` (a relative `url`, interpolating declared record fields as `{{record.field_name}}`), `{ kind: 'continue' }` or `{ kind: 'next-record' }`. Takes precedence over `navigateOnSuccess` and `resetOnSuccess`"),
   successMessage: I18nLabelSchema.optional().describe('Toast message on successful submit'),
   resetOnSuccess: z.boolean().optional().describe('Reset the form after a successful submit'),
-  navigateOnSuccess: z.unknown().optional().describe('Navigate after a successful submit'),
+  /**
+   * [#21464] Typed to the read: `resolveSuccessNavigate`
+   * (`plugin-form/src/successBehavior.ts:118-131` at the pin `89cad75d55`,
+   * called from `ObjectForm.tsx:1373` and `WizardForm.tsx:1071`) takes a
+   * string template, replaces `{id}` / `{recordId}` with the saved record's
+   * id (URL-escaped) and follows the result only when it is a relative
+   * reference; a declared value it refuses is reported on the success toast
+   * (`ObjectForm.tsx:1412-1429`). Any other value reached `template.replace`
+   * after the record had been written, and the submit then reported a failure.
+   * It is read only when `submitBehavior` is absent, and the renderer marks it
+   * deprecated in that key's favour.
+   */
+  navigateOnSuccess: z.string().optional()
+    .describe("Relative path to navigate to after a successful create/update — `{id}` / `{recordId}` are replaced with the saved record's id, URL-escaped; an absolute URL is refused at submit and reported on the success toast. Ignored when `submitBehavior` is set — prefer `submitBehavior`"),
   readOnly: z.boolean().optional().describe('Render every field read-only'),
   initialValues: z.record(z.string(), z.unknown()).optional().describe('Prefill values (create mode)'),
   initialData: z.record(z.string(), z.unknown()).optional().describe('Alternate spelling of `initialValues` the renderer also reads'),
-  mobile: z.unknown().optional().describe('Mobile presentation overrides'),
+  /** [#21464] The five members the form reads — see {@link ObjectFormMobileSchema}. */
+  mobile: ObjectFormMobileSchema.optional()
+    .describe('Phone presentation options, each opt-in — `{ stickyActions?, stepper?, stepperMinFields?, stepperFieldsPerStep?, fullscreenLongText? }`. Read by the flat (simple, sectionless) form'),
 }));
 /** Author state (ADR-0122: the bare name is the author state). */
 export type ObjectFormProps = z.input<typeof ObjectFormPropsSchema>;
@@ -5503,6 +5609,13 @@ export const ObjectMasterDetailFormPropsSchema = lazySchema(() => strictObject({
     error: (issue) =>
       typeof issue.input === 'string' ? MASTER_DETAIL_FORM_TYPE_RETIRED.get(issue.input) : undefined,
   }).optional().describe("Parent form presentation — the two variants the renderer honours for the parent half"),
+  /**
+   * [#21464] `sections` and `fields` are handed to the parent `object-form`
+   * verbatim (`plugin-form/src/MasterDetailForm.tsx:1692-1693` at the pin
+   * `89cad75d55`), so each is read exactly as that block's member is — and is
+   * HELD with it, in the enumeration pin's ledger, for the same reason (see
+   * {@link ObjectFormPropsSchema}'s `sections` and `fields`).
+   */
   sections: z.array(z.unknown()).optional().describe('Parent form sections'),
   fields: z.array(z.unknown()).optional().describe('Parent fields shown'),
   details: z.array(masterDetailDetailEntry()).optional()