diff --git a/.changeset/24254-plugin-auth-hook-codes.md b/.changeset/24254-plugin-auth-hook-codes.md
new file mode 100644
index 00000000000..6c7ad14bc18
--- /dev/null
+++ b/.changeset/24254-plugin-auth-hook-codes.md
@@ -0,0 +1,16 @@
+---
+"@objectstack/spec": minor
+---
+
+feat(spec): register four organization and invitation-placement refusal codes under `@objectstack/plugin-auth`
+
+Clause-②: yes (widening)
+
+The error-code ledger (`ERROR_CODE_LEDGER`, and so `ErrorCode`) gains four `@objectstack/plugin-auth` codes. Each names a hook refusal that today answers a bare `403 FORBIDDEN` with a message and no `code`, so a client such as the console cannot tell it apart from any other refusal on the same endpoint:
+
+- `ORGANIZATION_CREATION_DISABLED`: creating an organization is refused for every caller, because the deployment's effective tenancy posture enforces no organization wall (`/auth/config` reports `features.multiOrgEnabled: false`).
+- `ORGANIZATION_SLUG_LOCKED_BY_ACTIVE_ENVIRONMENTS`: an organization's slug cannot change while the organization has an environment whose status is neither archived nor failed.
+- `INVITE_PLACEMENT_UNSUPPORTED`: fail-closed. The invitation carries a placement (a business unit and positions), and this deployment has no delegated-administration runtime to authorize it.
+- `INVITE_PLACEMENT_OUTSIDE_ISSUER_SCOPE`: the delegated-administration gate refused the invitation's placement, because the business unit or a position lies outside the issuer's delegated scope.
+
+Registration only: `@objectstack/plugin-auth` still throws these refusals without a code until #24243 stamps them. The same change names a standard code, which needs no ledger row, for the plugin's other four code-less refusals: `RATE_LIMIT_EXCEEDED` for both phone-OTP send walls, which stay indistinguishable; `SERVICE_UNAVAILABLE` for the slug guard's read fault; and `VALIDATION_ERROR` for the reserved `__global__` organization id or slug. No existing code changes, and no standard-catalog member is shadowed (none needs a synonym waiver).
diff --git a/content/docs/references/api/contract.mdx b/content/docs/references/api/contract.mdx
index 8926962d89d..b9d95113cd7 100644
--- a/content/docs/references/api/contract.mdx
+++ b/content/docs/references/api/contract.mdx
@@ -28,7 +28,7 @@ const result = ApiErrorSchema.parse(data);
 
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
-| **code** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +335 more>` | ✅ | Error code (e.g. VALIDATION_ERROR; StandardErrorCode ∪ the ledger the serving side registers — ERROR_CODE_LEDGER for framework packages) |
+| **code** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +339 more>` | ✅ | Error code (e.g. VALIDATION_ERROR; StandardErrorCode ∪ the ledger the serving side registers — ERROR_CODE_LEDGER for framework packages) |
 | **declaredCode** | `string` | optional | The producer-declared code, verbatim, when it is not a member of the closed `code` vocabulary — the open, author-authored channel (app-specific spellings; ADR-0112) |
 | **message** | `string` | ✅ | Readable error message |
 | **userMessage** | `string` | optional | Producer-marked user-facing refusal text, verbatim. Present exactly when the producer opted in at throw time; consumers render it to end users and keep their generic substitution for anything unmarked. Status-agnostic; never replaces `message`. |
@@ -221,6 +221,8 @@ const result = ApiErrorSchema.parse(data);
 * `INVITE_EMAIL_FAILED`
 * `INVITE_ISSUER_MEMBER_ONLY`
 * `INVITE_ISSUER_UNVERIFIED`
+* `INVITE_PLACEMENT_OUTSIDE_ISSUER_SCOPE`
+* `INVITE_PLACEMENT_UNSUPPORTED`
 * `INVITE_REQUIRES_EMAIL`
 * `INVITE_ROLE_ABOVE_ISSUER`
 * `INVITE_SMS_FAILED`
@@ -268,7 +270,9 @@ const result = ApiErrorSchema.parse(data);
 * `OBJECT_OWNERSHIP_CONFLICT`
 * `OBJECT_PACKAGE_DISABLED`
 * `OPENAPI_UNAVAILABLE`
+* `ORGANIZATION_CREATION_DISABLED`
 * `ORGANIZATION_OWNERSHIP_MIGRATION_REQUIRED`
+* `ORGANIZATION_SLUG_LOCKED_BY_ACTIVE_ENVIRONMENTS`
 * `OS_PROTOCOL_INCOMPATIBLE`
 * `PACKAGE_DELETE_FAILED`
 * `PACKAGE_DELETE_PARTIAL`
diff --git a/content/docs/references/api/error-code-ledger.mdx b/content/docs/references/api/error-code-ledger.mdx
index 1689493dfff..af0915a155b 100644
--- a/content/docs/references/api/error-code-ledger.mdx
+++ b/content/docs/references/api/error-code-ledger.mdx
@@ -388,6 +388,8 @@ const result = ErrorCode.parse(data);
 * `INVITE_EMAIL_FAILED`
 * `INVITE_ISSUER_MEMBER_ONLY`
 * `INVITE_ISSUER_UNVERIFIED`
+* `INVITE_PLACEMENT_OUTSIDE_ISSUER_SCOPE`
+* `INVITE_PLACEMENT_UNSUPPORTED`
 * `INVITE_REQUIRES_EMAIL`
 * `INVITE_ROLE_ABOVE_ISSUER`
 * `INVITE_SMS_FAILED`
@@ -435,7 +437,9 @@ const result = ErrorCode.parse(data);
 * `OBJECT_OWNERSHIP_CONFLICT`
 * `OBJECT_PACKAGE_DISABLED`
 * `OPENAPI_UNAVAILABLE`
+* `ORGANIZATION_CREATION_DISABLED`
 * `ORGANIZATION_OWNERSHIP_MIGRATION_REQUIRED`
+* `ORGANIZATION_SLUG_LOCKED_BY_ACTIVE_ENVIRONMENTS`
 * `OS_PROTOCOL_INCOMPATIBLE`
 * `PACKAGE_DELETE_FAILED`
 * `PACKAGE_DELETE_PARTIAL`
diff --git a/packages/spec/src/api/error-code-ledger.test.ts b/packages/spec/src/api/error-code-ledger.test.ts
index 94f3b8f9dba..1fa24b51f4e 100644
--- a/packages/spec/src/api/error-code-ledger.test.ts
+++ b/packages/spec/src/api/error-code-ledger.test.ts
@@ -243,6 +243,24 @@ describe('ErrorCode (standard ∪ registered)', () => {
     }
   });
 
+  it('accepts the organization and placement hook refusal codes, registered ahead of their plugin-auth producer', () => {
+    // #24254 is the spec half of #24243's split: four of plugin-auth's eight
+    // code-less hook refusals get a new row; the other four answer a standard
+    // member and need none. #24243 stamps them and asserts these exact strings
+    // by value — pinned here too.
+    for (const code of [
+      'INVITE_PLACEMENT_OUTSIDE_ISSUER_SCOPE',
+      'INVITE_PLACEMENT_UNSUPPORTED',
+      'ORGANIZATION_CREATION_DISABLED',
+      'ORGANIZATION_SLUG_LOCKED_BY_ACTIVE_ENVIRONMENTS',
+    ]) {
+      expect(ErrorCode.parse(code)).toBe(code);
+      expect(ERROR_CODE_LEDGER['@objectstack/plugin-auth'], `${code} registered under plugin-auth`).toContain(code);
+      // INVITE and ORGANIZATION are tokens no standard member carries — no waiver needed.
+      expect(standardSynonymOf(code), `${code} needs no waiver`).toBeUndefined();
+    }
+  });
+
   it('accepts the nine-code batch — every code that ships in dist, door or no door (ruled: the ledger is the published face)', () => {
     // The #16404 ruling (director seat, decision batch #62, 2026-09-07, option
     // D): the published face is this ledger, so a code that ships in `dist` is
diff --git a/packages/spec/src/api/error-code-ledger.zod.ts b/packages/spec/src/api/error-code-ledger.zod.ts
index 69956f14fc9..c1463e2555f 100644
--- a/packages/spec/src/api/error-code-ledger.zod.ts
+++ b/packages/spec/src/api/error-code-ledger.zod.ts
@@ -574,6 +574,11 @@ export const ERROR_CODE_LEDGER = {
     // each thrown 403 from `beforeCreateInvitation` with its code (#23945).
     'INVITE_ISSUER_MEMBER_ONLY',  // [#24082] 403: an issuer below admin grade may invite only as a plain `member`; the requested role does not outrank theirs but may carry capability of its own
     'INVITE_ISSUER_UNVERIFIED',   // [#24082] 403, fail-closed: the issuer's `sys_member` role was not established (the read answered with no usable row, or the composition has no data engine to read), so the invitation may confer nothing beyond `member`; a read that throws answers `SERVICE_UNAVAILABLE` (503) instead
+    // [#24254] The invitation placement gate's two refusals (ADR-0105 D8), thrown
+    // 403 from `beforeCreateInvitation` after the role cap, registered AHEAD of
+    // their producer: today both are a bare `FORBIDDEN`, and #24243 stamps these.
+    'INVITE_PLACEMENT_OUTSIDE_ISSUER_SCOPE', // [#24254] 403: the delegated-administration gate refused the invitation's placement intent (its business unit, or a position's permission sets, lies outside the issuer's `adminScope`, ADR-0090 D12), so no invitation is created; the gate's own verdict, not a failure to reach one
+    'INVITE_PLACEMENT_UNSUPPORTED', // [#24254] 403, fail-closed: the invitation carries placement intent (a business unit and positions) and this deployment has no delegated-administration runtime (plugin-security's `invitation-placement` service) to authorize it, so no invitation is created; the same invitation without placement is unaffected
     'INVITE_REQUIRES_EMAIL',
     'INVITE_ROLE_ABOVE_ISSUER',   // [#24082] 403: the requested role grades above the issuer's own (an invitation never confers authority above its issuer)
     'INVALID_REQUEST',
@@ -582,6 +587,11 @@ export const ERROR_CODE_LEDGER = {
     'LAST_LOCAL_CREDENTIAL',      // refusing to remove the user's only local credential
     'NO_IDENTITY',                // import row has neither email nor phone
     'NO_PENDING_VERIFICATION',    // pass-through from better-auth
+    // [#24254] The organization hooks' two refusals no standard member names
+    // (`beforeCreateOrganization`, `beforeUpdateOrganization`), registered AHEAD
+    // of their producer: today both are a bare `FORBIDDEN`, and #24243 stamps these.
+    'ORGANIZATION_CREATION_DISABLED', // [#24254] 403: the deployment's effective tenancy posture enforces no organization wall (ADR-0105), so creating an organization is refused for every caller; the same derivation `/auth/config` publishes as `features.multiOrgEnabled: false`, a deployment setting and not a grant the caller lacks
+    'ORGANIZATION_SLUG_LOCKED_BY_ACTIVE_ENVIRONMENTS', // [#24254] 403: a change to a new slug is refused while the organization has an active environment, meaning a `sys_environment` row with its `organization_id` whose `status` is neither `archived` nor `failed` (a row with no status counts), and no hostname is read; a guard read that could not answer is `SERVICE_UNAVAILABLE` (503) instead
     'PASSWORD_ALREADY_SET',       // pass-through from better-auth
     'PASSWORD_EXPIRED',
     'PASSWORD_POLICY_VIOLATION',