@@ -0,0 +1,22 @@
+---
+'@objectstack/spec': patch
+'@objectstack/service-datasource': patch
+---
+
+fix(service-datasource): a plugin-driver datasource connected or reconnected through the connection service keeps the engine's correctness floor (#27666)
+
+Clause-②: yes (narrowing) — `EngineDatasourceDef` (`@objectstack/spec/contracts`) gains an optional `driver` key, and a plugin-driver datasource connected through the datasource-connection service is now held behind the #27277 floor, so its accepted reads and writes narrow as that floor's changeset describes
+Metadata-protocol: none
+
+<!-- adr-0087: not-required (no-migration-prescription) No key of any authored schema is added, removed, renamed or re-shaped; the new key is on an engine-facing contract that the connection service fills itself. A datasource that now gets the floor needs no metadata change, so there is nothing for a migration to rewrite. -->
+
+**BREAKING** for a host whose datasource-driver factory builds plugin drivers: those datasources are now floored (a read matching more than 1000 rows answers 422 `EXTERNAL_ROW_CAP_EXCEEDED`, predicate bulk writes and `aggregate` are refused by name), as manifest-declared ones already were.
+
+The engine holds a plugin driver on a non-managed datasource behind a correctness floor (row cap, the query re-applied in memory, remote write refusals mapped) when the datasource definition it stores names a driver id that is not built in. Only the engine's own manifest install path carried that id. The datasource-connection service registered the definition without it, and `EngineDatasourceDef` had no such key, so a datasource created at runtime through datasource management was never floored, and one edited and reconnected lost the floor (the eviction drops the stored definition, and the connect that follows had no id to keep). Nothing said so: a driver that ignored `where` could answer rows outside the caller's sharing or row-level scope.
+
+- `EngineDatasourceDef` (`@objectstack/spec/contracts`) gains an optional `driver`, the datasource's driver id. An engine never reads an absent key as "built in": a caller that registers only the write-gate facts keeps the id stored before it.
+- `DatasourceConnectionService.connect` registers the definition with `record.driver`. `reconnect`'s keep-old-pool restore registers the OLD record's driver id (`previous.driver`; `previous` now carries it), not the new record's, because the kept pool was built from the old record.
+
+A built-in driver (memory, sqlite, sqlite-wasm, postgres, mysql, mongodb, turso) and a managed datasource are unchanged: the floor engages only for a driver id a server plugin published on a datasource whose `schemaMode` is not `managed`. A host that registers no driver factory for plugin ids (the default) sees no change today.
+
+What to do: nothing. A host whose factory builds plugin drivers gets the floor on those datasources from the connection service's next connect.
@@ -3,7 +3,7 @@
 /**
  * `applyDriverQueryInMemory` — the engine's own reading of a driver query over
  * rows already in memory: `where`, `orderBy`, `offset` / `limit` and `fields`,
- * in that order (ADR-0015 Tier A, epic #27261 P1).
+ * in that order (epic #27261 Tier A, P1).
  *
  * ## Why the engine owns this
  *
 
@@ -9248,10 +9248,13 @@ export class ObjectQL implements IObjectQLEngine {
    */
   registerDatasourceDef(def: DatasourceDef): void {
     if (!def?.name) return;
-    // [#27277] A def that names no driver keeps the id stored before it: the
-    // datasource-connection service re-registers a def without `driver` after
-    // a connect (`EngineDatasourceDef` has no such key), and reading that
-    // absence as "not a plugin driver" would take the floor back off.
+    // [#27277] A def that names no driver keeps the id stored before it: a
+    // caller registering only the write-gate facts after a connect must not
+    // take the floor back off, so an absent key never reads as "not a plugin
+    // driver". It is a keep, not a source: `unregisterDriver` drops the stored
+    // def, so a connect that follows an eviction has nothing to keep — the
+    // datasource-connection service names `driver` on every registration
+    // ([#27666], `EngineDatasourceDef.driver`).
     const driver = def.driver ?? this.datasourceDefs.get(def.name)?.driver;
     this.datasourceDefs.set(def.name, { driver, schemaMode: def.schemaMode, external: def.external });
     this.applyExternalDriverFloor(def.name);
 
@@ -2,7 +2,7 @@
 
 /**
  * [#27277] The refusals the engine's floor over a plugin driver raises
- * (`external-driver-floor.ts`, ADR-0015 Tier A, epic #27261 P1).
+ * (`external-driver-floor.ts`, epic #27261 Tier A, P1; ruling 6487532394 on #27277).
  *
  * All are 4xx: the caller can change the request and try again, and the
  * message is theirs to read. That is what keeps them apart from the third
 
@@ -485,3 +485,102 @@ describe('[#27277] a re-registration that names no driver keeps the floor', () =
     expect(ids(await engine.find('tree_node', { where: { kind: 'branch' } }))).toEqual(['n2', 'n5']);
   });
 });
+
+describe('[#27666] the datasource-connection service\'s registrations floor a plugin driver, and a reconnect keeps it', () => {
+  const TREE_PKG = {
+    id: 'tree_pkg',
+    name: 'Tree',
+    objects: [{
+      name: 'tree_node',
+      datasource: 'tree',
+      external: { remoteName: 'nodes', writable: true },
+      fields: { kind: { type: 'text' }, label: { type: 'text' }, weight: { type: 'number' } },
+    }],
+  };
+  /** What `DatasourceConnectionService.connect` registers after `registerDriver`: the def WITH its driver id. */
+  const connectDef = (driver: string) => ({ name: 'tree', driver, schemaMode: 'external', external: { allowWrites: true } });
+
+  it('a runtime-origin datasource (no manifest def): driver, then the connect def naming the driver id', async () => {
+    const engine = new ObjectQL();
+    const remote = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(remote.driver);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+    engine.registerApp(TREE_PKG as any);
+    const held = engine.getDriverByName('tree')!;
+    expect(isExternalDriverFloor(held)).toBe(true);
+    expect(unwrapExternalDriverFloor(held)).toBe(remote.driver);
+    expect(ids(await engine.find('tree_node', { where: { kind: 'branch' } }))).toEqual(['n2', 'n5']);
+  });
+
+  it('a reconnect (unregisterDriver, then the connect sequence) is still floored', async () => {
+    const engine = new ObjectQL();
+    const first = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(first.driver);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+    engine.registerApp(TREE_PKG as any);
+    expect(isExternalDriverFloor(engine.getDriverByName('tree')!)).toBe(true);
+
+    // `reconnect`: the eviction door drops the driver AND the stored def …
+    expect(engine.unregisterDriver('tree')).toBe(true);
+    expect(engine.getDriverByName('tree')).toBeUndefined();
+    // … then `connect` registers the rebuilt pool and the def again, driver id included.
+    const rebuilt = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(rebuilt.driver);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+
+    const held = engine.getDriverByName('tree')!;
+    expect(isExternalDriverFloor(held)).toBe(true);
+    expect(unwrapExternalDriverFloor(held)).toBe(rebuilt.driver);
+    expect(ids(await engine.find('tree_node', { where: { kind: 'branch' } }))).toEqual(['n2', 'n5']);
+    expect(rebuilt.sent).toHaveLength(1);
+  });
+
+  it('the failed-rebuild restore (unregisterDriver, then the OLD pool and its def back) is still floored', async () => {
+    const engine = new ObjectQL();
+    const old = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(old.driver);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+    engine.registerApp(TREE_PKG as any);
+
+    engine.unregisterDriver('tree');
+    // `restoreOldPool`: the kept driver instance and the def it was serving under, `previous.driver` included.
+    engine.registerDriver(old.driver, false);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+
+    const held = engine.getDriverByName('tree')!;
+    expect(isExternalDriverFloor(held)).toBe(true);
+    expect(unwrapExternalDriverFloor(held)).toBe(old.driver);
+    expect(ids(await engine.find('tree_node', { where: { kind: 'branch' } }))).toEqual(['n2', 'n5']);
+  });
+
+  it('control: after the eviction a re-registration that names no driver has nothing to keep, and the where-ignoring driver answers every row', async () => {
+    // The defect's mechanism, pinned so the positive cases above are known to
+    // depend on the driver id reaching `registerDatasourceDef`: the engine's
+    // "keep the stored id" only keeps what the eviction left, which is nothing.
+    const engine = new ObjectQL();
+    const first = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(first.driver);
+    engine.registerDatasourceDef(connectDef('spike_tree'));
+    engine.registerApp(TREE_PKG as any);
+    engine.unregisterDriver('tree');
+    const rebuilt = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(rebuilt.driver);
+    engine.registerDatasourceDef({ name: 'tree', schemaMode: 'external', external: { allowWrites: true } });
+    expect(engine.getDriverByName('tree')).toBe(rebuilt.driver);
+    expect(ids(await engine.find('tree_node', { where: { kind: 'branch' } }))).toHaveLength(TREE_ROWS.length);
+  });
+
+  it('a built-in driver through the same connect and reconnect sequences stays the registered instance itself', () => {
+    const engine = new ObjectQL();
+    const first = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(first.driver);
+    engine.registerDatasourceDef(connectDef('sqlite'));
+    engine.registerApp(TREE_PKG as any);
+    expect(engine.getDriverByName('tree')).toBe(first.driver);
+    engine.unregisterDriver('tree');
+    const rebuilt = remoteDriver('tree', TREE_ROWS);
+    engine.registerDriver(rebuilt.driver);
+    engine.registerDatasourceDef(connectDef('sqlite'));
+    expect(engine.getDriverByName('tree')).toBe(rebuilt.driver);
+  });
+});
@@ -2,7 +2,7 @@
 
 /**
  * [#27277] The engine's correctness floor over a plugin driver on an external
- * datasource (ADR-0015 Tier A, epic #27261 P1).
+ * datasource (epic #27261 Tier A, P1; ruling 6487532394 on #27277).
  *
  * ## Which drivers
  *
 
@@ -300,7 +300,7 @@ export type {
   PrimaryDatasourceUnresolvedReason,
 } from './driver-connect-errors.js';
 // [#27277] The engine's floor over a plugin driver on an external datasource
-// (ADR-0015 Tier A): the in-memory reading of a driver query it applies, and
+// (epic #27261 Tier A): the in-memory reading of a driver query it applies, and
 // the two 422 refusals it raises (registered in ERROR_CODE_LEDGER), plus
 // [#27471] the 400 read refusal (the standard INVALID_QUERY).
 export { applyDriverQueryInMemory } from './driver-query-in-memory.js';
 
@@ -195,8 +195,13 @@ describe('DatasourceConnectionService.connect', () => {
     // Driver registered under the DATASOURCE name (engine routes by driver.name).
     expect(engine!.drivers.has('warehouse')).toBe(true);
     expect(engine!.drivers.get('warehouse')!.name).toBe('warehouse');
-    // Datasource definition recorded for the write gate.
-    expect(engine!.defs).toEqual([{ name: 'warehouse', schemaMode: 'external', external: externalDs.external }]);
+    // Datasource definition recorded for the write gate — and, [#27666], with
+    // the driver id the engine keys its plugin-driver floor on: for a
+    // runtime-origin datasource this registration is the only one the engine
+    // ever sees, so a def without `driver` would serve a plugin driver unfloored.
+    expect(engine!.defs).toEqual([
+      { name: 'warehouse', driver: 'sqlite', schemaMode: 'external', external: externalDs.external },
+    ]);
     // Bound external objects got read metadata synced (DDL-free).
     expect(engine!.synced).toEqual(['ext_customer']);
   });
 
@@ -334,13 +334,50 @@ describe('#13804 — updateDatasource rebuilds the live pool when connectivity c
     const state = rig.connection.getConnectionState('analytics')!;
     expect(state.status).toBe('failed-degraded');
     // 3. Not pool-less: the datasource def the old pool was serving under is
-    //    restored alongside the driver (`unregisterDriver` removes both).
+    //    restored alongside the driver (`unregisterDriver` removes both) —
+    //    [#27666] its driver id included, which is what the engine keys its
+    //    plugin-driver floor on.
     expect(rig.engine.defs.get('analytics')).toMatchObject({
       name: 'analytics',
+      driver: 'sqlite',
       schemaMode: 'external',
     });
   });
 
+  it('[#27666] the def registered after a rebuild names the NEW driver id; the def restored after a failed rebuild names the OLD one', async () => {
+    // The engine floors a non-managed datasource whose def names a driver id
+    // that is not built in. `unregisterDriver` drops the stored def, so the
+    // id has to travel with every registration this path makes — the rebuilt
+    // pool's from `next`, the kept pool's from `previous` — or a plugin
+    // driver is served unfloored after a reconfigure, and nothing says so.
+    const rig = makeRig({
+      failWhen: (spec) => (spec.config as { filename?: string }).filename === '/tmp/bad.db',
+    });
+    await rig.service.createDatasource(
+      draft({ driver: 'driver.port_schedule', schemaMode: 'external', external: { allowWrites: false } }),
+    );
+    expect(rig.engine.defs.get('analytics')).toMatchObject({ driver: 'driver.port_schedule', schemaMode: 'external' });
+
+    // A reconfigure that changes the driver and succeeds: the def names the new id.
+    const rebuilt = await rig.service.updateDatasource('analytics', {
+      driver: 'driver.port_schedule_v2',
+      config: { filename: '/tmp/new.db' },
+    });
+    expect(rebuilt.status).toBe('ok');
+    expect(rig.engine.drivers.get('analytics')!.builtFrom.driver).toBe('driver.port_schedule_v2');
+    expect(rig.engine.defs.get('analytics')).toMatchObject({ driver: 'driver.port_schedule_v2', schemaMode: 'external' });
+
+    // A reconfigure that changes the driver and fails: the kept pool's def
+    // names the id it was built from, not the one that never came up.
+    const failed = await rig.service.updateDatasource('analytics', {
+      driver: 'driver.port_schedule_v3',
+      config: { filename: '/tmp/bad.db' },
+    });
+    expect(failed.status).toBe('error');
+    expect(rig.engine.drivers.get('analytics')!.builtFrom.driver).toBe('driver.port_schedule_v2');
+    expect(rig.engine.defs.get('analytics')).toMatchObject({ driver: 'driver.port_schedule_v2', schemaMode: 'external' });
+  });
+
   it('a supplied secret alone forces a rebuild — rewrap-in-place changes what the ref dereferences to', async () => {
     const rig = makeRig({ stableSecretRef: true });
     await rig.service.createDatasource(
 
@@ -666,8 +666,13 @@ export class DatasourceConnectionService {
           : true;
       engine.registerDriver(engineDriver, opts.asDefault === true);
       if (!heldBefore) registeredByThisAttempt = engineDriver.name;
+      // [#27666] `driver` rides along: the engine keys its plugin-driver floor
+      // on the def's driver id, and this registration is the ONLY one a
+      // runtime-origin datasource gets (the manifest path never sees it), and
+      // the only one left after `reconnect`'s eviction dropped the stored def.
       engine.registerDatasourceDef?.({
         name,
+        driver: record.driver,
         schemaMode: record.schemaMode,
         external: record.external as { allowWrites?: boolean } | undefined,
       });
@@ -830,7 +835,7 @@ export class DatasourceConnectionService {
     record: ConnectableDatasource,
     opts: {
       context?: DatasourceConnectContext;
-      previous?: Pick<ConnectableDatasource, 'schemaMode' | 'external'>;
+      previous?: Pick<ConnectableDatasource, 'driver' | 'schemaMode' | 'external'>;
     } = {},
   ): Promise<ConnectResult> {
     const name = record.name;
@@ -848,8 +853,13 @@ export class DatasourceConnectionService {
 
     const restoreOldPool = (): void => {
       engine.registerDriver?.(oldDriver, false);
+      // [#27666] The OLD record's driver id, not `record.driver`: the kept
+      // pool was built from `previous`, and a reconfigure may have changed the
+      // driver. Without it the engine would read the restored def as "not a
+      // plugin driver" and serve the kept pool unfloored.
       engine.registerDatasourceDef?.({
         name,
+        driver: opts.previous?.driver,
         schemaMode: opts.previous?.schemaMode,
         external: opts.previous?.external as { allowWrites?: boolean } | undefined,
       });
Original file line number	Diff line number	Diff line change
`@@ -3,7 +3,7 @@`
`3`	`3`	`/**`
`4`	`4`	* `applyDriverQueryInMemory` — the engine's own reading of a driver query over
`5`	`5`	* rows already in memory: `where`, `orderBy`, `offset` / `limit` and `fields`,
`6`		`- * in that order (ADR-0015 Tier A, epic #27261 P1).`
	`6`	`+ * in that order (epic #27261 Tier A, P1).`
`7`	`7`	`*`
`8`	`8`	`* ## Why the engine owns this`
`9`	`9`	`*`
Original file line number	Diff line number	Diff line change
`@@ -2,7 +2,7 @@`
`2`	`2`
`3`	`3`	`/**`
`4`	`4`	`* [#27277] The refusals the engine's floor over a plugin driver raises`
`5`		- * (`external-driver-floor.ts`, ADR-0015 Tier A, epic #27261 P1).
	`5`	+ * (`external-driver-floor.ts`, epic #27261 Tier A, P1; ruling 6487532394 on #27277).
`6`	`6`	`*`
`7`	`7`	`* All are 4xx: the caller can change the request and try again, and the`
`8`	`8`	`* message is theirs to read. That is what keeps them apart from the third`
Original file line number	Diff line number	Diff line change
`@@ -2,7 +2,7 @@`
`2`	`2`
`3`	`3`	`/**`
`4`	`4`	`* [#27277] The engine's correctness floor over a plugin driver on an external`
`5`		`- * datasource (ADR-0015 Tier A, epic #27261 P1).`
	`5`	`+ * datasource (epic #27261 Tier A, P1; ruling 6487532394 on #27277).`
`6`	`6`	`*`
`7`	`7`	`* ## Which drivers`
`8`	`8`	`*`