@@ -0,0 +1,29 @@
+---
+'@objectstack/spec': minor
+'@objectstack/cli': minor
+'@objectstack/platform-objects': minor
+---
+
+feat(spec): a greyed action says why — `disabledReason` beside `disabled`
+
+Clause-②: yes (widening)
+Metadata-protocol: added
+
+`ActionSchema` gains one optional key, `disabledReason`: the sentence a greyed action shows to say why it is unavailable, beside the `disabled` predicate that greys it. An action that does not declare it parses exactly as before, and the console keeps its default reason, "Not available for this record".
+
+```ts
+defineAction({
+  name: 'submit_for_approval',
+  label: 'Submit for approval',
+  objectName: 'clm_contract',
+  disabled: "record.legal_review_status != 'approved'",
+  disabledReason: 'An approved legal review is required before the contract enters approval.',
+});
+```
+
+- **An `I18nLabel`.** A plain string or an inline locale map (`{ en, 'zh-CN' }`). A blank string is refused at parse: `''` or whitespace only. Omit the key to keep the default. The locale-map arm is the `InlineLocaleMapSchema` every `I18nLabel` takes, so a map is not checked for blank values. `disabledMessage`, `disabledTooltip`, `disabledHint` and `disabledText` are renamed onto it.
+- **Translated with the copy keys.** The slot is `objects.OBJECT._actions.ACTION.disabledReason` (`globalActions.ACTION.disabledReason` for an action with no `objectName`), beside `confirmText` and `successMessage`. `translateAction` overlays it, and `os i18n extract` (`@objectstack/cli`) scaffolds it for an action that declares one and seeds nothing for one that does not.
+- **Display only.** It does not change what `disabled` evaluates to and is never read as a condition: `os validate` checks `disabled`, not `disabledReason`. It is not access control either. A call that reaches the server anyway is refused by the action's own rules (its body or hook, `requiredPermissions`), never by this text.
+- **Studio.** The action editor's Placement section gains a "Disabled Reason" row under "Disabled", translated in `@objectstack/platform-objects` for zh-CN, ja-JP and es-ES.
+
+Nothing renders the key yet. The console's greyed-action surfaces (the record header, the record section bar, the declared actions bar and the four `action:*` renderers) read it in the follow-up change. Until then the liveness ledger marks it `planned` with `authorWarn`, so `os validate` warns an author who declares it that nothing shows it yet.
@@ -245,6 +245,7 @@ interface Action {
   visible?: ExpressionInput;    // Visibility predicate (CEL)
   requiresFeature?: string;     // Public auth feature flag gate — lowered into `visible` at parse time
   disabled?: boolean | ExpressionInput; // Disabled when TRUE (CEL)
+  disabledReason?: I18nLabel;   // Why it is greyed — hover title + accessible description (display only)
 
   // Bulk
   bulkEnabled?: boolean;        // Apply to multiple selected records
@@ -333,6 +334,21 @@ disabled: "record.status != 'paid'"
 Predicates are **bare CEL** — `record.status == 'paid'`, not `${record.status == 'paid'}` and not `{record.status} == 'paid'` (in CEL, `{…}` is a map literal). A `${…}`-wrapped or brace-wrapped predicate is not evaluated as a boolean.
 </Callout>
 
+#### Saying why: `disabledReason`
+
+A greyed action says **why** with `disabledReason`, the sentence beside the `disabled` predicate. It is meant for the button's hover title and its accessible description (a menu item, under its label). The console does not show it yet: until its greyed-action readers ship, every greyed action shows the console's default reason, "Not available for this record", and `os validate` warns an author who declares the key.
+
+```yaml
+name: submit_for_approval
+label: Submit for approval
+disabled: "record.legal_review_status != 'approved'"
+disabledReason: An approved legal review is required before the contract enters approval.
+```
+
+- It is an `I18nLabel`: a plain string, translated at `objects.<object>._actions.<action>.disabledReason` (`globalActions.<action>.disabledReason` for an action with no `objectName`), or an inline locale map. `os i18n extract` scaffolds the key.
+- A blank string (`''` or whitespace only) is refused at parse. Omit the key to keep the default.
+- It is **display only**. It does not change what `disabled` evaluates to, nothing reads it as a condition, and it is not access control: a call that reaches the server anyway is refused by the action's own rules (its body or hook, `requiredPermissions`), never by this text.
+
 #### Evaluation context
 
 Action predicates evaluate against the **record the action is attached to**. Both `record.<field>` and the bare field name resolve to the current record's value:
 
@@ -499,6 +499,7 @@ const result = ApiMethod.parse(data);
 | **requiresFeature** | `Enum<'twoFactor' \| 'organization' \| 'multiOrgEnabled' \| 'degradedTenancy' \| …>` | optional | Public auth feature flag gating this action; lowered into `visible` at parse time. |
 | **requiresMembershipReach** | `Enum<'invite_member' \| 'cancel_invitation' \| 'update_member_role' \| …>` | optional | Organization endpoint (a MEMBERSHIP_REACH row) whose membership-grade gate this action follows; lowered into `visible` over current_user.positions at parse time. |
 | **disabled** | `boolean \| string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Disabled predicate — `true`/`false` literal, CEL string, or `{dialect, source}` envelope. The action is shown but refused when it evaluates TRUE. Omit = never disabled. |
+| **disabledReason** | `string \| Record<string, string>` | optional | Display-only reason for a greyed action, for its hover title and accessible description while `disabled` evaluates TRUE (declared ahead of its console reader: no renderer shows it yet) — the default-language string, or an inline locale map; translated at `objects.OBJECT._actions.ACTION.disabledReason` (`globalActions.ACTION.disabledReason` for an object-less action). Not a gate: the server refuses a call on its own rules (hooks, `requiredPermissions`), and nothing reads this as a condition. Omit = the default reason, "Not available for this record". A blank reason is refused. |
 | **requiredPermissions** | `string[]` | optional | [ADR-0066 D4] Capabilities required to invoke this action. Enforced with 403 on the platform action route (script/flow/modal + MCP) and mirrored as a UI hide; a `type: api` action pointed at a custom endpoint must re-check it there. |
 | **ai** | `{ exposed?: boolean; description?: string; category?: Enum<'data' \| 'action' \| 'flow' \| 'integration' \| 'vector_search' \| 'analytics' \| 'utility'>; paramHints?: Record<string, object>; … }` | optional | AI exposure (opt-in). Set ai.exposed=true + ai.description to make this callable by agents. |
 | **recordIdParam** | `string` | optional | Body key to inject the row id into when running from a list_item context. |
 
@@ -346,6 +346,7 @@ const result = MetadataBulkResultSchema.parse(data);
 | **requiresFeature** | `Enum<'twoFactor' \| 'organization' \| 'multiOrgEnabled' \| 'degradedTenancy' \| …>` | optional | Public auth feature flag gating this action; lowered into `visible` at parse time. |
 | **requiresMembershipReach** | `Enum<'invite_member' \| 'cancel_invitation' \| 'update_member_role' \| …>` | optional | Organization endpoint (a MEMBERSHIP_REACH row) whose membership-grade gate this action follows; lowered into `visible` over current_user.positions at parse time. |
 | **disabled** | `boolean \| string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Disabled predicate — `true`/`false` literal, CEL string, or `{dialect, source}` envelope. The action is shown but refused when it evaluates TRUE. Omit = never disabled. |
+| **disabledReason** | `string \| Record<string, string>` | optional | Display-only reason for a greyed action, for its hover title and accessible description while `disabled` evaluates TRUE (declared ahead of its console reader: no renderer shows it yet) — the default-language string, or an inline locale map; translated at `objects.OBJECT._actions.ACTION.disabledReason` (`globalActions.ACTION.disabledReason` for an object-less action). Not a gate: the server refuses a call on its own rules (hooks, `requiredPermissions`), and nothing reads this as a condition. Omit = the default reason, "Not available for this record". A blank reason is refused. |
 | **requiredPermissions** | `string[]` | optional | [ADR-0066 D4] Capabilities required to invoke this action. Enforced with 403 on the platform action route (script/flow/modal + MCP) and mirrored as a UI hide; a `type: api` action pointed at a custom endpoint must re-check it there. |
 | **ai** | `{ exposed?: boolean; description?: string; category?: Enum<'data' \| 'action' \| 'flow' \| 'integration' \| 'vector_search' \| 'analytics' \| 'utility'>; paramHints?: Record<string, object>; … }` | optional | AI exposure (opt-in). Set ai.exposed=true + ai.description to make this callable by agents. |
 | **recordIdParam** | `string` | optional | Body key to inject the row id into when running from a list_item context. |
 
@@ -128,6 +128,7 @@ Translation data for a single field
 | **description** | `string` | optional | Translated action description — the explanatory line under the title in the action's param dialog |
 | **confirmText** | `string` | optional | Translated confirmation prompt |
 | **successMessage** | `string` | optional | Translated success toast/message |
+| **disabledReason** | `string` | optional | Translated reason for a greyed action, for its hover title and accessible description while its `disabled` predicate is TRUE (no renderer shows it yet) |
 | **outcomeMessages** | `Record<string, string>` | optional | Translated success copy per handler outcome, keyed by the snake_case outcome name the action's `outcomeMessages` declares |
 | **params** | `Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>` | optional | Action parameter translations keyed by parameter name |
 | **resultDialog** | `{ title?: string; description?: string; acknowledge?: string; fields?: Record<string, string> }` | optional | Translations for the action result dialog |
@@ -227,6 +228,7 @@ Translation data for a single object
 | **description** | `string` | optional | Translated action description — the explanatory line under the title in the action's param dialog |
 | **confirmText** | `string` | optional | Translated confirmation prompt |
 | **successMessage** | `string` | optional | Translated success toast/message |
+| **disabledReason** | `string` | optional | Translated reason for a greyed action, for its hover title and accessible description while its `disabled` predicate is TRUE (no renderer shows it yet) |
 | **outcomeMessages** | `Record<string, string>` | optional | Translated success copy per handler outcome, keyed by the snake_case outcome name the action's `outcomeMessages` declares |
 | **params** | `Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>` | optional | Action parameter translations keyed by parameter name |
 | **resultDialog** | `{ title?: string; description?: string; acknowledge?: string; fields?: Record<string, string> }` | optional | Translations for the action result dialog |
@@ -384,6 +386,7 @@ Translation data for a single object
 | **description** | `string` | optional | Translated action description — the explanatory line under the title in the action's param dialog |
 | **confirmText** | `string` | optional | Translated confirmation prompt |
 | **successMessage** | `string` | optional | Translated success toast/message |
+| **disabledReason** | `string` | optional | Translated reason for a greyed action, for its hover title and accessible description while its `disabled` predicate is TRUE (no renderer shows it yet) |
 | **outcomeMessages** | `Record<string, string>` | optional | Translated success copy per handler outcome, keyed by the snake_case outcome name the action's `outcomeMessages` declares |
 | **params** | `Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>` | optional | Action parameter translations keyed by parameter name |
 | **resultDialog** | `{ title?: string; description?: string; acknowledge?: string; fields?: Record<string, string> }` | optional | Translations for the action result dialog |
@@ -603,6 +606,7 @@ Translation data for a single object
 | **description** | `string` | optional | Translated action description — the explanatory line under the title in the action's param dialog |
 | **confirmText** | `string` | optional | Translated confirmation prompt |
 | **successMessage** | `string` | optional | Translated success toast/message |
+| **disabledReason** | `string` | optional | Translated reason for a greyed action, for its hover title and accessible description while its `disabled` predicate is TRUE (no renderer shows it yet) |
 | **outcomeMessages** | `Record<string, string>` | optional | Translated success copy per handler outcome, keyed by the snake_case outcome name the action's `outcomeMessages` declares |
 | **params** | `Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>` | optional | Action parameter translations keyed by parameter name |
 | **resultDialog** | `{ title?: string; description?: string; acknowledge?: string; fields?: Record<string, string> }` | optional | Translations for the action result dialog |
@@ -791,6 +795,7 @@ Translation data for a single object
 | **description** | `string` | optional | Translated action description — the explanatory line under the title in the action's param dialog |
 | **confirmText** | `string` | optional | Translated confirmation prompt |
 | **successMessage** | `string` | optional | Translated success toast/message |
+| **disabledReason** | `string` | optional | Translated reason for a greyed action, for its hover title and accessible description while its `disabled` predicate is TRUE (no renderer shows it yet) |
 | **outcomeMessages** | `Record<string, string>` | optional | Translated success copy per handler outcome, keyed by the snake_case outcome name the action's `outcomeMessages` declares |
 | **params** | `Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>` | optional | Action parameter translations keyed by parameter name |
 | **resultDialog** | `{ title?: string; description?: string; acknowledge?: string; fields?: Record<string, string> }` | optional | Translations for the action result dialog |
 
@@ -56,6 +56,7 @@ const result = ActionSchema.parse(data);
 | **requiresFeature** | `Enum<'twoFactor' \| 'organization' \| 'multiOrgEnabled' \| 'degradedTenancy' \| 'oidcProvider' \| 'sso' \| 'ssoEnforced' \| 'deviceAuthorization' \| 'admin' \| 'phoneNumber' \| … +2 more>` | optional | Public auth feature flag gating this action; lowered into `visible` at parse time. |
 | **requiresMembershipReach** | `Enum<'invite_member' \| 'cancel_invitation' \| 'update_member_role' \| 'transfer_ownership' \| 'remove_member' \| 'create_team' \| 'update_team' \| 'remove_team' \| … +4 more>` | optional | Organization endpoint (a MEMBERSHIP_REACH row) whose membership-grade gate this action follows; lowered into `visible` over current_user.positions at parse time. |
 | **disabled** | `boolean \| string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Disabled predicate — `true`/`false` literal, CEL string, or `{dialect, source}` envelope. The action is shown but refused when it evaluates TRUE. Omit = never disabled. |
+| **disabledReason** | `string \| Record<string, string>` | optional | Display-only reason for a greyed action, for its hover title and accessible description while `disabled` evaluates TRUE (declared ahead of its console reader: no renderer shows it yet) — the default-language string, or an inline locale map; translated at `objects.OBJECT._actions.ACTION.disabledReason` (`globalActions.ACTION.disabledReason` for an object-less action). Not a gate: the server refuses a call on its own rules (hooks, `requiredPermissions`), and nothing reads this as a condition. Omit = the default reason, "Not available for this record". A blank reason is refused. |
 | **requiredPermissions** | `string[]` | optional | [ADR-0066 D4] Capabilities required to invoke this action. Enforced with 403 on the platform action route (script/flow/modal + MCP) and mirrored as a UI hide; a `type: api` action pointed at a custom endpoint must re-check it there. |
 | **ai** | `{ exposed?: boolean; description?: string; category?: Enum<'data' \| 'action' \| 'flow' \| 'integration' \| 'vector_search' \| 'analytics' \| 'utility'>; paramHints?: Record<string, object>; … }` | optional | AI exposure (opt-in). Set ai.exposed=true + ai.description to make this callable by agents. |
 | **recordIdParam** | `string` | optional | Body key to inject the row id into when running from a list_item context. |
 
@@ -72,7 +72,7 @@ export default defineStack({
 | Picklist option labels | `objects.<name>.fields.<field>.options.<value>` |
 | View titles, descriptions, empty states | `objects.<name>._views.<view>` |
 | Bulk-action copy on a list view (button, confirm prompt, dialog fields) | `objects.<name>._views.<view>.bulkActions.<def>.label` / `.confirmText` / `.confirmLabel` / `.params.<param>.label` / `.help` / `.placeholder` — a bulk param's hint is `help`, not `helpText` |
-| Action labels, confirm text, success messages | `objects.<name>._actions.<action>` |
+| Action labels, confirm text, success messages, disabled reasons | `objects.<name>._actions.<action>` |
 | Action result dialogs (title / description / acknowledge / field labels) | `objects.<name>._actions.<action>.resultDialog` |
 | Form sections | `objects.<name>._sections.<section>` |
 | Custom validation-rule messages | `objects.<name>._validations.<rule>.message` |