@@ -0,0 +1,20 @@
+---
+'@objectstack/rest': patch
+---
+
+fix(rest)!: an async import job for an unregistered object is refused with 404 `OBJECT_NOT_FOUND` before any job is created (#27501)
+
+Clause-②: no (narrowing) — `POST /data/:object/import/jobs` now refuses an object name the runtime does not register, where it used to answer `201` and persist a job. Nothing is widened.
+Metadata-protocol: none
+
+<!-- adr-0087: not-required (no-migration-prescription) No key of any schema is added, removed, renamed or re-shaped, and no export or type changes: one REST door now refuses, up front, an object name that every row of its job was already refused for. There is nothing for a migration to rewrite and no tombstone. -->
+
+**BREAKING** accept-set narrowing at one REST data door (`@objectstack/rest`).
+
+- **Before.** `POST /data/no_such_object/import/jobs` answered `201` with a job id and persisted a `sys_import_job` row. The job then ran, every row failed with `OBJECT_NOT_FOUND`, and the job read `succeeded`.
+- **Now.** The door answers `404` with `error.code: 'OBJECT_NOT_FOUND'`, the same envelope `POST /data/no_such_object` answers, before the body is parsed. No job row is written and no worker runs.
+- **Unchanged.** A registered object gets `201` and a job exactly as before. A job whose rows partly fail still ends `succeeded`, as before.
+- **Who sees it.** An import client that sends an object name nothing is behind, for example a typo. Such a request used to look accepted while it could import nothing.
+- **Also refused up front.** An object of a disabled package now gets the data door's `404 OBJECT_PACKAGE_DISABLED` instead of a job (re-enable the package). A legacy `ns__short` object addressed by its short name alone gets `404 OBJECT_NOT_FOUND`, because the door counts an object only under its own name, as the API-exposure gate does (send the full registered name).
+
+**The remedy.** Send the object's registered name, the one `POST /data/:object` accepts.
@@ -80,7 +80,9 @@ import { sendError as sendEnvelopeError, sendOk } from '@objectstack/types';
 // [#26594] The read path's ONE no-row answer, for a row that left the caller's
 // sight between the record read and the projection.
 import { recordNotFoundError } from '@objectstack/core';
-import { logError } from './log.js';
+// [#27501] The data door's answer for a name no object is behind.
+import { objectNotFoundError } from '@objectstack/core';
+import { logError, logWarn } from './log.js';
 import {
     DATA_EXPORT_PARAMS,
     IMPORT_JOB_OBJECT,
@@ -308,6 +310,42 @@ function importUndoFailure(id: string, action: ImportUndoFailure['action'], erro
     return { id, action, code: answer.code, error: answer.message };
 }
 
+/**
+ * [#27501] Refuse an import job for an object nothing is behind, with the data
+ * door's own answer for that name: `objectNotFoundError` (`@objectstack/core`),
+ * the one factory the protocol's existence gate and the engine's verbs throw,
+ * classified by the same `handleRouteError` — 404 `OBJECT_NOT_FOUND`, the same
+ * envelope `POST /data/OBJ` answers.
+ *
+ * The object is read by name as the exposure gate reads it (the execution face
+ * where the protocol has one, else `getMetaItem`), and counts only under its
+ * own name. A read the protocol refuses `OBJECT_PACKAGE_DISABLED` (its
+ * by-name read's answer for an object of a disabled package, and the data
+ * door's code for it too) propagates as thrown. Any other thrown read fails
+ * OPEN and logs, as the exposure gate's same read does (`loadObjectItem`,
+ * #3545): it is no answer about existence, and each row's data call still
+ * gives the data door's own. A protocol with no by-name read cannot answer,
+ * and is not asked.
+ */
+async function assertImportObjectExists(p: any, objectName: string, environmentId: string | undefined): Promise<void> {
+    const byName = typeof p.getMetaItemForExecution === 'function'
+        ? p.getMetaItemForExecution
+        : typeof p.getMetaItem === 'function' ? p.getMetaItem : undefined;
+    if (!byName) return;
+    let envelope: any;
+    try {
+        envelope = await byName.call(p, { type: 'object', name: objectName, ...(environmentId ? { environmentId } : {}) });
+    } catch (err) {
+        if ((err as { code?: unknown } | null)?.code === 'OBJECT_PACKAGE_DISABLED') throw err;
+        logWarn('[REST] import job: object metadata read failed — not refused up front '
+            + '(each row\'s data call still answers for the object)', (err as Error)?.message ?? err);
+        return;
+    }
+    const item = envelope?.item;
+    if (item !== null && typeof item === 'object' && item.name === objectName) return;
+    throw objectNotFoundError(objectName);
+}
+
 /**
  * Register object-specific action endpoints that don't fit the generic CRUD
  * shape — `RestServer#registerDataActionEndpoints`' body, called by that method
@@ -592,6 +630,14 @@ export function registerDataActionEndpoints(this: DataActionRouteHost, basePath:
                 }
                 if (await this.enforceApiAccess(req, res, p, environmentId, 'import', context)) return;
 
+                // [#27501] The object must exist before a job does. The exposure
+                // gate above passes an unknown object through by design (#3770),
+                // and the data door's existence refusal only fires inside the
+                // per-row writes — AFTER the 201 and the persisted job, so the
+                // job read `succeeded` with every row refused. Refused here, up
+                // front, before the body is parsed and before any job row exists.
+                await assertImportObjectExists(p, objectName, environmentId);
+
                 // [#24348] The synchronous door's control opt-out gate, asked at
                 // the same point: before the body is parsed and before a job row
                 // exists, so a refused request creates no job and writes no row.
 
@@ -127,6 +127,7 @@ async function boot(decorateDriver?: (driver: any) => void) {
     list: find('GET', '/api/v1/data/import/jobs'),
     cancel: find('POST', '/api/v1/data/import/jobs/:jobId/cancel'),
     undo: find('POST', '/api/v1/data/import/jobs/:jobId/undo'),
+    dataCreate: find('POST', '/api/v1/data/:object'),
   };
 }
 
@@ -460,3 +461,50 @@ describe('async import job — real engine + protocol integration', () => {
     for (const w of restoreWrites) expect(w.context?.preserveAudit).toBeUndefined();
   });
 });
+
+/**
+ * The async create door resolves the object BEFORE it persists a job: an
+ * object name the runtime does not register is refused up front with the
+ * answer the data door gives the same name (`POST /data/OBJ`, 404
+ * `OBJECT_NOT_FOUND`), and no `sys_import_job` row is written — rather than a
+ * 201, a job id and a job whose every row then fails on that same refusal.
+ */
+describe('async import job — an unregistered object is refused before a job exists', () => {
+  let ctx: Awaited<ReturnType<typeof boot>>;
+  beforeEach(async () => {
+    ctx = await boot();
+    expect(ctx.create && ctx.dataCreate).toBeTruthy();
+  });
+
+  const jobRows = async () => ctx.engine.find('sys_import_job', { where: {} });
+  const call = (route: any, object: string, body: any) => {
+    const res = makeRes();
+    return route.handler({ params: { object }, body } as any, res).then(() => res);
+  };
+
+  it('answers 404 OBJECT_NOT_FOUND, the data door\'s answer, and persists no job row', async () => {
+    expect(await jobRows()).toHaveLength(0);
+
+    const res = await call(ctx.create, 'no_such_object', { format: 'csv', csv: 'title\nx\n' });
+    expect(res._status).toBe(404);
+    expect(res._json?.error?.code ?? res._json?.code).toBe('OBJECT_NOT_FOUND');
+
+    // The same envelope the data door answers for the same name, byte for byte.
+    const door = await call(ctx.dataCreate, 'no_such_object', { title: 'x' });
+    expect(door._status).toBe(404);
+    expect(res._json).toEqual(door._json);
+
+    // Counted at the engine: the refusal wrote no job.
+    expect(await jobRows()).toHaveLength(0);
+  });
+
+  it('control: a registered object still gets 201 and exactly one job row', async () => {
+    const res = await call(ctx.create, 'task', { format: 'json', rows: [{ id: 'k1', title: 'kept' }] });
+    expect(res._status).toBe(201);
+    expect(res._json).toMatchObject({ object: 'task', status: 'pending', total: 1 });
+    await waitForTerminal(ctx.progress, res._json.jobId);
+    const rows = await jobRows();
+    expect(rows).toHaveLength(1);
+    expect(rows[0]).toMatchObject({ id: res._json.jobId, object_name: 'task' });
+  });
+});