@@ -0,0 +1,25 @@
+---
+'@objectstack/runtime': patch
+---
+
+fix(runtime): `callData`'s exposure refusal for the object a request addresses carries the data door's code, `OBJECT_API_DISABLED` (404) or `OBJECT_API_METHOD_NOT_ALLOWED` (405), on the dispatcher's `/data` routes, the `/mcp` data tools and declared endpoints (#23528)
+
+Clause-②: no
+
+**What was wrong.** An object can declare `apiEnabled: false` or an `apiMethods` whitelist. The runtime dispatcher's exposure check for the object a request addresses (`refuseUnexposedDataAction`, which every `callData` asks first) refused with a status and a message but no `code`. So:
+
+- the dispatcher's `/data` routes derived a code from the status: `404 RESOURCE_NOT_FOUND` / `405 METHOD_NOT_ALLOWED`;
+- the `/mcp` data tools rendered the message alone;
+- a declared endpoint whose target is an object answered the derived code too.
+
+`RestServer` and the MCP stdio tools answer the same declaration `OBJECT_API_DISABLED` / `OBJECT_API_METHOD_NOT_ALLOWED`, and so did the dispatcher's own refusal of a nested-relation filter on an unexposed object.
+
+**What a caller reads now.** Every one of these doors answers the data door's code with the same status as before:
+
+| door | declaration | FROM | TO |
+|:--|:--|:--|:--|
+| dispatcher `/data` (and declared endpoints) | `apiEnabled: false` | `404`, `error.code` `RESOURCE_NOT_FOUND` | `404`, `error.code` `OBJECT_API_DISABLED` |
+| dispatcher `/data` (and declared endpoints) | verb outside `apiMethods` | `405`, `error.code` `METHOD_NOT_ALLOWED` | `405`, `error.code` `OBJECT_API_METHOD_NOT_ALLOWED` |
+| `/mcp` data tools | either | `isError: true`; the text is the message | `isError: true`; the text is `{ "error": { "code", "message", "status" } }` |
+
+The status and the message do not change. The thrown value is now an `Error` carrying `code`, `status`, the addressed object as `object`, and the effective operation set as `allowed` on a 405. A caller that branched on `RESOURCE_NOT_FOUND` / `METHOD_NOT_ALLOWED` for an exposure refusal on these doors should branch on the two `OBJECT_API_*` codes, as it already does for `RestServer`.
@@ -24,9 +24,12 @@
  *    `{ error: { code, message, status } }` with `isError`. The table is held
  *    equal to the registered tool list, so a tool added later needs a row.
  *  - The same catches render a code-less throw as its bare message,
- *    byte-identical to `errorResult(messageOf(err))`. That includes the value
- *    the HTTP bridge's exposure gate throws today, `{ statusCode, message }`
- *    with no `code`. Nothing is invented for it.
+ *    byte-identical to `errorResult(messageOf(err))`. Nothing is invented for it.
+ *  - [#23528] The HTTP bridge's exposure gate (`@objectstack/runtime`'s
+ *    `refuseUnexposedDataAction`, which `callData` asks first) used to be such
+ *    a throw, `{ statusCode, message }` with no `code`. It now throws the data
+ *    door's coded refusal, and renders as one. The producer side is pinned in
+ *    runtime's `action-execution-addressed-exposure-refusal.test.ts`.
  *  - The data tools and `list_actions` WITHHOLD `details`. Measured on `/mcp`,
  *    a `PERMISSION_DENIED` carries the caller's `positions` and
  *    `permissionSets` there, which the runtime dispatcher drops from the wire.
@@ -195,11 +198,36 @@ describe('MCP tools over HTTP /mcp: a coded refusal carries its code (#23509)',
   // One site is enough below: every catch renders through the one reader.
   const query = SITES.find((s) => s.tool === 'query_records')!;
 
-  it('the HTTP bridge exposure gate\'s `{ statusCode, message }` (no `code`) answers its bare message: nothing is invented', async () => {
-    const thrown = { statusCode: 404, message: "Object 'task' is not exposed via the API" };
-    expect(await callTool(query, thrown)).toEqual({
-      content: [{ type: 'text', text: "Object 'task' is not exposed via the API" }],
-      isError: true,
+  // [#23528] Moved to the coded rendering. This row pinned the gate's old
+  // `{ statusCode: 404, message }` as its bare message. The gate now throws
+  // an `Error` carrying the data door's `code` and `status`, the addressed
+  // object as `object`, and `allowed` on a 405; the thrown values below are
+  // that shape, with the gate's own messages.
+  it('the HTTP bridge exposure gate\'s 404 answers OBJECT_API_DISABLED with its status', async () => {
+    const thrown = Object.assign(new Error('object is not exposed via the API'), {
+      code: 'OBJECT_API_DISABLED',
+      status: 404,
+      object: 'task',
+    });
+    const result = await callTool(query, thrown);
+    expect(result.isError).toBe(true);
+    expect(result.content).toHaveLength(1);
+    expect(JSON.parse(result.content[0].text)).toEqual({
+      error: { code: 'OBJECT_API_DISABLED', message: 'object is not exposed via the API', status: 404 },
+    });
+  });
+
+  it('the HTTP bridge exposure gate\'s 405 answers OBJECT_API_METHOD_NOT_ALLOWED with its status', async () => {
+    const thrown = Object.assign(new Error("API operation 'list' is not allowed for this object"), {
+      code: 'OBJECT_API_METHOD_NOT_ALLOWED',
+      status: 405,
+      object: 'task',
+      allowed: ['get'],
+    });
+    const result = await callTool(query, thrown);
+    expect(result.isError).toBe(true);
+    expect(JSON.parse(result.content[0].text)).toEqual({
+      error: { code: 'OBJECT_API_METHOD_NOT_ALLOWED', message: "API operation 'list' is not allowed for this object", status: 405 },
     });
   });
 
 
@@ -42,8 +42,8 @@
  * A throw that is NOT a declared envelope keeps the arm's answer: a bare
  * `Error` is still `500 INTERNAL_ERROR` carrying `code` and `message` only, with
  * no `cause` in the body; a throw that declares `statusCode` and no registered
- * code (the shape `callData`'s exposure gate throws) keeps the status it
- * declared. The declared 503 also carries no `cause`: the session read's own
+ * code (the shape `callData` throws when no data service resolves) keeps the
+ * status it declared. The declared 503 also carries no `cause`: the session read's own
  * failure stays off the wire.
  *
  * ## The auth-mount arm
 
@@ -0,0 +1,163 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#23528] `callData`'s ADDRESSED-object exposure refusal
+ * (`refuseUnexposedDataAction`) is the data door's: an `Error` carrying `code`
+ * and `status`, the addressed object as `object`, and the effective operation
+ * set as `allowed` on a 405. Its nested-relation target refusal already
+ * answered that way (`action-execution-calldata-relation-target-exposure.test.ts`),
+ * and so do `RestServer` and the MCP stdio face for the same declaration.
+ *
+ * ## What was open
+ *
+ * The gate threw `{ statusCode, message }` with no `code`. Each door then
+ * answered it without the data door's code:
+ *
+ *  - the runtime dispatcher's `/data` door derived `404 RESOURCE_NOT_FOUND` /
+ *    `405 METHOD_NOT_ALLOWED` from the status
+ *    (`domains/data-write-request-gate.test.ts` pins both doors on a real store);
+ *  - the `/mcp` tools render a thrown `code` since #23509, and rendered this
+ *    refusal as its message alone (`buildMcpBridge` calls `callData` on every
+ *    data verb, pinned below).
+ *
+ * The status and the message are unchanged. Every row asserts `code` and
+ * `status` and that neither the protocol nor the engine was asked.
+ */
+
+import { describe, expect, it, vi } from 'vitest';
+import { callData, type ActionExecutionDeps } from './action-execution.js';
+import { buildMcpBridge } from './domains/mcp.js';
+import type { HttpProtocolContext } from './http-dispatcher.js';
+
+const MEMBER = { userId: 'ax_member', isSystem: false, positions: [], permissions: [] } as any;
+const REQ = { request: {}, executionContext: MEMBER } as HttpProtocolContext;
+
+const object = (name: string, enable?: Record<string, unknown>) => ({
+    name,
+    label: name,
+    ...(enable ? { enable } : {}),
+    fields: {
+        id: { name: 'id', label: 'ID', type: 'text' },
+        name: { name: 'name', label: 'Name', type: 'text' },
+    },
+});
+
+/** The fixture: `ax_hidden` is not exposed at all, `ax_getonly` exposes `get` alone. */
+const SCHEMAS: Record<string, unknown> = {
+    ax_hidden: object('ax_hidden', { apiEnabled: false }),
+    ax_getonly: object('ax_getonly', { apiMethods: ['get'] }),
+};
+
+const HIDDEN = { code: 'OBJECT_API_DISABLED', status: 404, object: 'ax_hidden', allowed: undefined };
+const HIDDEN_MESSAGE = 'object is not exposed via the API';
+
+/**
+ * The protocol and engine `callData` would reach, each verb a spy, so a refusal
+ * is shown to ask neither. With the protocol present it serves every verb but
+ * `aggregate`, which takes the engine; so the engine carries only the reads.
+ */
+function makeHarness() {
+    const protocol = {
+        createData: vi.fn(async (req: any) => ({ object: req.object, id: 'n1', record: req.data })),
+        getData: vi.fn(async (req: any) => ({ object: req.object, id: req.id, record: { id: req.id } })),
+        updateData: vi.fn(async (req: any) => ({ object: req.object, id: req.id, record: req.data })),
+        deleteData: vi.fn(async (req: any) => ({ object: req.object, id: req.id, success: true })),
+        findData: vi.fn(async (req: any) => ({ object: req.object, records: [], total: 0, hasMore: false })),
+    };
+    const engine = {
+        registry: { getObject: (n: string) => SCHEMAS[n] },
+        find: vi.fn(async () => []),
+        aggregate: vi.fn(async () => []),
+    };
+    const services: Record<string, unknown> = {
+        metadata: { getObject: async (n: string) => SCHEMAS[n] },
+        protocol,
+        objectql: engine,
+    };
+    const deps: ActionExecutionDeps = {
+        resolveService: (async (_ctx: HttpProtocolContext, name: string) => services[name]) as any,
+        getObjectQL: async () => engine as any,
+    };
+    const asked = () => [...Object.values(protocol), engine.find, engine.aggregate]
+        .reduce((n, spy) => n + spy.mock.calls.length, 0);
+    return { deps, protocol, asked };
+}
+
+/** What a door reads off the refusal: the envelope pair and the two context fields. */
+const refusal = (e: any) => ({ code: e?.code, status: e?.status, object: e?.object, allowed: e?.allowed });
+
+/** Every action `callData` serves, with params naming `object`. */
+const VERBS: ReadonlyArray<readonly [string, (object: string) => Record<string, unknown>]> = [
+    ['create', (o) => ({ object: o, data: { name: 'x' } })],
+    ['get', (o) => ({ object: o, id: 'r1' })],
+    ['update', (o) => ({ object: o, id: 'r1', data: { name: 'x' } })],
+    ['delete', (o) => ({ object: o, id: 'r1' })],
+    ['query', (o) => ({ object: o, query: {} })],
+    ['find', (o) => ({ object: o, query: {} })],
+    ['aggregate', (o) => ({ object: o, aggregations: [{ function: 'count', alias: 'n' }] })],
+];
+
+describe('[#23528] callData refuses an addressed object its declaration does not expose with the data door\'s code', () => {
+    for (const [action, params] of VERBS) {
+        it(`${action} on an \`apiEnabled: false\` object: 404 OBJECT_API_DISABLED, nothing asked`, async () => {
+            const h = makeHarness();
+            const err: any = await callData(h.deps, REQ, action, params('ax_hidden'), undefined, undefined, MEMBER).catch((e) => e);
+            expect(err).toBeInstanceOf(Error);
+            expect(refusal(err)).toEqual(HIDDEN);
+            expect(err.message).toBe(HIDDEN_MESSAGE);
+            expect(h.asked()).toBe(0);
+        });
+    }
+
+    it('create on an object exposing `get` alone: 405 OBJECT_API_METHOD_NOT_ALLOWED naming the effective set, nothing asked', async () => {
+        const h = makeHarness();
+        const err: any = await callData(h.deps, REQ, 'create', { object: 'ax_getonly', data: { name: 'x' } }, undefined, undefined, MEMBER)
+            .catch((e) => e);
+        expect(err).toBeInstanceOf(Error);
+        expect(refusal(err)).toEqual({ code: 'OBJECT_API_METHOD_NOT_ALLOWED', status: 405, object: 'ax_getonly', allowed: ['get'] });
+        expect(err.message).toBe("API operation 'create' is not allowed for this object");
+        expect(h.asked()).toBe(0);
+    });
+
+    it('CONTROL: the verb the whitelist grants is served', async () => {
+        const h = makeHarness();
+        await callData(h.deps, REQ, 'get', { object: 'ax_getonly', id: 'r1' }, undefined, undefined, MEMBER);
+        expect(h.protocol.getData).toHaveBeenCalledTimes(1);
+    });
+
+    it('CONTROL: a system context is not asked, so the hidden object is served', async () => {
+        const h = makeHarness();
+        await callData(h.deps, REQ, 'query', { object: 'ax_hidden', query: {} }, undefined, undefined, { isSystem: true } as any);
+        expect(h.protocol.findData).toHaveBeenCalledTimes(1);
+    });
+});
+
+/**
+ * The `/mcp` face: `buildMcpBridge` is the bridge `handleMcp` hands the MCP
+ * tools, and each data member reaches `callData`. The tools render a thrown
+ * string `code` and numeric `status` as `{ error: { code, message, status } }`
+ * (`@objectstack/mcp`'s `thrownRefusalEnvelope`, pinned in its
+ * `mcp-coded-refusal.test.ts`), so the bridge must hand them the coded refusal.
+ */
+describe('[#23528] the /mcp bridge hands its tools the coded refusal on every data member', () => {
+    const MEMBERS: ReadonlyArray<readonly [string, (bridge: any) => Promise<unknown>]> = [
+        ['query', (b) => b.query('ax_hidden', {})],
+        ['get', (b) => b.get('ax_hidden', 'r1')],
+        ['aggregate', (b) => b.aggregate('ax_hidden', { aggregations: [{ function: 'count', alias: 'n' }] })],
+        ['create', (b) => b.create('ax_hidden', { name: 'x' })],
+        ['update', (b) => b.update('ax_hidden', 'r1', { name: 'x' })],
+        ['remove', (b) => b.remove('ax_hidden', 'r1')],
+    ];
+
+    for (const [member, call] of MEMBERS) {
+        it(`${member}: 404 OBJECT_API_DISABLED, nothing asked`, async () => {
+            const h = makeHarness();
+            const bridge = buildMcpBridge(h.deps as any, REQ);
+            const err: any = await call(bridge).catch((e) => e);
+            expect(err).toBeInstanceOf(Error);
+            expect(refusal(err)).toEqual(HIDDEN);
+            expect(err.message).toBe(HIDDEN_MESSAGE);
+            expect(h.asked()).toBe(0);
+        });
+    }
+});
@@ -239,31 +239,42 @@ async function refuseUnservedRelationTargets(
     }
 }
 
+/**
+ * [#23528] The data door's two exposure codes, by the gate's verdict: `404
+ * OBJECT_API_DISABLED` for an object whose `apiEnabled` is `false`, and `405
+ * OBJECT_API_METHOD_NOT_ALLOWED` with the effective operation set as `allowed`
+ * for a verb its `apiMethods` leaves out. That is the pairing `RestServer`
+ * answers for the same declaration (`apiAccessDenialFromEnable`).
+ *
+ * The ONE table both exposure refusals in this file stamp: the addressed
+ * object's ({@link refuseUnexposedDataAction}) and a nested-relation
+ * condition's target's ({@link unservedRelationTargetError}). One table, so one
+ * `callData` never answers the same verdict with two codes. A denial from
+ * {@link checkApiExposure} carries exactly one of these two statuses.
+ */
+function exposureRefusalFields(gate: ApiExposureDecision):
+    | { code: 'OBJECT_API_DISABLED'; status: 404 }
+    | { code: 'OBJECT_API_METHOD_NOT_ALLOWED'; status: 405; allowed: string[] } {
+    return gate.status === 404
+        ? { code: 'OBJECT_API_DISABLED', status: 404 }
+        : { code: 'OBJECT_API_METHOD_NOT_ALLOWED', status: 405, allowed: gate.allowedOperations ?? [] };
+}
+
 /**
  * [#22823] The data door's refusal of an unserved nested-relation condition
  * target, field for field (`refuseUnservedRelationTarget`): `code` and `status`
- * by the gate's verdict, the TARGET as `object` (the route's object is not the
- * one switched off), the condition's position as `param`, and the effective
- * operation set as `allowed` on a 405.
+ * by the gate's verdict ({@link exposureRefusalFields}), the TARGET as `object`
+ * (the route's object is not the one switched off), the condition's position
+ * as `param`, and the effective operation set as `allowed` on a 405.
  */
 function unservedRelationTargetError(target: string, param: string, gate: ApiExposureDecision): Error {
     const consequence = `, so the condition on it at '${param}' was not evaluated and the query was not run. `
         + 'Filter on the lookup\'s stored id instead, or remove the condition.';
-    const disabled = gate.status === 404;
-    const err: any = new Error(disabled
+    const refusal = exposureRefusalFields(gate);
+    const message = refusal.status === 404
         ? `Object '${target}' is not exposed via the API${consequence}`
-        : `API operation '${RELATION_CONDITION_TARGET_OPERATION}' is not allowed on object '${target}'${consequence}`);
-    if (disabled) {
-        err.code = 'OBJECT_API_DISABLED';
-        err.status = 404;
-    } else {
-        err.code = 'OBJECT_API_METHOD_NOT_ALLOWED';
-        err.status = 405;
-        err.allowed = gate.allowedOperations ?? [];
-    }
-    err.object = target;
-    err.param = param;
-    return err;
+        : `API operation '${RELATION_CONDITION_TARGET_OPERATION}' is not allowed on object '${target}'${consequence}`;
+    return Object.assign(new Error(message), refusal, { object: target, param });
 }
 
 /** The engine for a schema lookup, or `undefined` — a lookup failure is judged by the caller's fail-closed branch. */
@@ -290,6 +301,16 @@ async function resolveEngineQuietly(deps: ActionExecutionDeps, requestContext: H
  * about the body it sent. `RestServer` asks `enforceApiAccess` before its
  * twin gate for the same reason. Moved, not copied: this is the one place the
  * dispatcher's exposure decision is resolved.
+ *
+ * [#23528] The refusal is the data door's, as the nested-relation target's
+ * already was: an `Error` carrying `code` and `status` from
+ * {@link exposureRefusalFields}, the addressed object as `object`, and
+ * `allowed` on a 405. It used to throw `{ statusCode, message }` with no code,
+ * so the dispatcher's `/data` door answered `404 RESOURCE_NOT_FOUND` / `405
+ * METHOD_NOT_ALLOWED` (codes derived from the status) and the `/mcp` tools
+ * rendered the message alone, where `RestServer` and the MCP stdio face answer
+ * the same declaration `OBJECT_API_DISABLED` / `OBJECT_API_METHOD_NOT_ALLOWED`.
+ * The statuses do not move, and neither does the message.
  */
 export async function refuseUnexposedDataAction(deps: ActionExecutionDeps,
     requestContext: HttpProtocolContext,
@@ -308,7 +329,7 @@ export async function refuseUnexposedDataAction(deps: ActionExecutionDeps,
     }
     const gate = checkApiExposure(def, action);
     if (!gate.allowed) {
-        throw { statusCode: gate.status ?? 403, message: gate.reason ?? 'API access denied' };
+        throw Object.assign(new Error(gate.reason ?? 'API access denied'), exposureRefusalFields(gate), { object });
     }
 }