diff --git a/packages/agent-core-v2/src/app/sessionLifecycle/sessionLifecycleService.ts b/packages/agent-core-v2/src/app/sessionLifecycle/sessionLifecycleService.ts
index 69b3aec21..dec2ade2b 100644
--- a/packages/agent-core-v2/src/app/sessionLifecycle/sessionLifecycleService.ts
+++ b/packages/agent-core-v2/src/app/sessionLifecycle/sessionLifecycleService.ts
@@ -35,7 +35,7 @@
  *
  * Every materialization (create/resume/fork-target) first takes the session's
  * cross-process write lease under `session-leases/` and registers that lease
- * as the session's write gate. Close/archive stop producers, flush the
+ * as the session's write admission. Close/archive stop producers, flush the
  * session's append-log tail, seal new write admission, await already-admitted
  * I/O, and then release the lease. Any release failure converges internally to
  * a dirty-marked abandoned release; callers never need a second teardown
@@ -81,7 +81,7 @@ import { IHostEnvironment } from '#/os/interface/hostEnvironment';
 import { IHostFileSystem, type HostDirEntry } from '#/os/interface/hostFileSystem';
 import { IAppendLogStore } from '#/persistence/interface/appendLogStore';
 import { IAtomicDocumentStore } from '#/persistence/interface/atomicDocumentStore';
-import { IWriteGateRegistry } from '#/persistence/interface/writeGate';
+import { IStorageWriteAdmission } from '#/persistence/interface/storageWriteAdmission';
 import {
   type CrossProcessLockInspection,
   ICrossProcessLockService,
@@ -145,7 +145,6 @@ type SessionReleaseStage =
   | 'dispose-scope'
   | 'will-release'
   | 'flush'
-  | 'seal'
   | 'drain-writes'
   | 'lease-lost'
   | 'shutdown';
@@ -197,7 +196,7 @@ export class SessionLifecycleService extends Disposable implements ISessionLifec
     @ITelemetryService private readonly telemetry: ITelemetryService,
     @ILogService private readonly log: ILogService,
     @ICrossProcessLockService private readonly locks: ICrossProcessLockService,
-    @IWriteGateRegistry private readonly writeGates: IWriteGateRegistry,
+    @IStorageWriteAdmission private readonly writeAdmission: IStorageWriteAdmission,
     @ISessionLeaseContactProvider
     private readonly leaseContact: ISessionLeaseContactProvider,
   ) {
@@ -276,7 +275,7 @@ export class SessionLifecycleService extends Disposable implements ISessionLifec
     const lease = await this.acquireSessionLease(opts.sessionId);
     let registration: IDisposable;
     try {
-      registration = this.writeGates.register(sessionScope, lease);
+      registration = this.writeAdmission.registerSession(sessionScope, lease);
     } catch (error) {
       lease.release();
       throw error;
@@ -505,10 +504,8 @@ export class SessionLifecycleService extends Disposable implements ISessionLifec
       await this.announceWillRelease({ sessionId, reason: kind });
       stage = 'flush';
       await this.flushSessionTail(sessionId, entry.scope);
-      stage = 'seal';
-      entry.lease.seal();
       stage = 'drain-writes';
-      await entry.lease.drained();
+      await entry.lease.sealAndDrain();
     } catch (error) {
       await this.abandonSession(entry, stage, error);
       throw new Error2(
@@ -551,8 +548,7 @@ export class SessionLifecycleService extends Disposable implements ISessionLifec
     await this.writeDirtyMarker(entry, reason, stage);
     await this.announceWillRelease({ sessionId, reason: 'dirty-abort' });
     await Promise.allSettled(taskServices.map((tasks) => tasks.flushPersistence()));
-    entry.lease.seal();
-    await entry.lease.drained();
+    await entry.lease.sealAndDrain();
     this.finishSessionRelease(entry);
     if (reason === 'flush-failed') {
       this.telemetry.track2('session_dirty_abort', {
@@ -607,7 +603,7 @@ export class SessionLifecycleService extends Disposable implements ISessionLifec
     try {
       entry.registration.dispose();
     } catch (error) {
-      this.log.warn('failed to unregister session write gate', {
+      this.log.warn('failed to unregister session write admission', {
         sessionId: entry.handle.id,
         error: String(error),
       });
diff --git a/packages/agent-core-v2/src/app/workspace/fileWorkspacePersistence.ts b/packages/agent-core-v2/src/app/workspace/fileWorkspacePersistence.ts
index d41b6f63e..b174439de 100644
--- a/packages/agent-core-v2/src/app/workspace/fileWorkspacePersistence.ts
+++ b/packages/agent-core-v2/src/app/workspace/fileWorkspacePersistence.ts
@@ -33,7 +33,7 @@ export class FileWorkspacePersistence implements IWorkspacePersistence {
   constructor(@IAtomicDocumentStore private readonly docs: IAtomicDocumentStore) {}
 
   runExclusive<T>(op: () => Promise<T>): Promise<T> {
-    return this.docs.runExclusive(WORKSPACE_CATALOG_SCOPE, WORKSPACE_CATALOG_KEY, op);
+    return this.docs.withExclusiveKeyMutation(WORKSPACE_CATALOG_SCOPE, WORKSPACE_CATALOG_KEY, op);
   }
 
   async load(): Promise<WorkspaceCatalog | undefined> {
diff --git a/packages/agent-core-v2/src/index.ts b/packages/agent-core-v2/src/index.ts
index ef8364fa1..73437e86a 100644
--- a/packages/agent-core-v2/src/index.ts
+++ b/packages/agent-core-v2/src/index.ts
@@ -338,10 +338,11 @@ export * from '#/persistence/interface/appendLogStore';
 export * from '#/persistence/interface/atomicDocumentStore';
 export * from '#/persistence/interface/queryStore';
 export * from '#/persistence/interface/blobStore';
-export * from '#/persistence/interface/writeGate';
+export * from '#/persistence/interface/sessionWriteAdmission';
+export * from '#/persistence/interface/storageWriteAdmission';
 export * from '#/persistence/backends/node-fs/fileStorageService';
 export * from '#/persistence/backends/node-fs/appendLogStore';
-export * from '#/persistence/backends/node-fs/writeGateRegistryService';
+export * from '#/persistence/backends/node-fs/storageWriteAdmissionService';
 export * from '#/persistence/backends/node-fs/atomicDocumentStore';
 export * from '#/persistence/backends/node-fs/blobStoreService';
 export * from '#/persistence/backends/node-fs/projectLocalConfigService';
diff --git a/packages/agent-core-v2/src/persistence/backends/memory/inMemoryStorageService.ts b/packages/agent-core-v2/src/persistence/backends/memory/inMemoryStorageService.ts
index f53acfdb7..9e80581d8 100644
--- a/packages/agent-core-v2/src/persistence/backends/memory/inMemoryStorageService.ts
+++ b/packages/agent-core-v2/src/persistence/backends/memory/inMemoryStorageService.ts
@@ -133,8 +133,12 @@ export class InMemoryStorageService implements IFileSystemStorageService {
     };
   }
 
-  runExclusive<T>(scope: string, key: string, op: () => Promise<T>): Promise<T> {
-    return enqueueKeyedOperation(this.operationQueues, this.watchKey(scope, key), op);
+  withExclusiveKeyMutation<T>(
+    scope: string,
+    key: string,
+    mutation: () => Promise<T>,
+  ): Promise<T> {
+    return enqueueKeyedOperation(this.operationQueues, this.watchKey(scope, key), mutation);
   }
 
   private notifyWatchers(scope: string, key: string): void {
diff --git a/packages/agent-core-v2/src/persistence/backends/node-fs/atomicDocumentStore.ts b/packages/agent-core-v2/src/persistence/backends/node-fs/atomicDocumentStore.ts
index 527d66403..e56a4552d 100644
--- a/packages/agent-core-v2/src/persistence/backends/node-fs/atomicDocumentStore.ts
+++ b/packages/agent-core-v2/src/persistence/backends/node-fs/atomicDocumentStore.ts
@@ -82,18 +82,22 @@ class AtomicDocumentStoreBase implements IAtomicDocumentStore {
     key: string,
     mutate: (current: T | undefined) => T | Promise<T>,
   ): Promise<T> {
-    return this.runExclusive(scope, key, async () => {
+    return this.withExclusiveKeyMutation(scope, key, async () => {
       const next = await mutate(await this.get<T>(scope, key));
       await this.set(scope, key, next);
       return next;
     });
   }
 
-  runExclusive<T>(scope: string, key: string, op: () => Promise<T>): Promise<T> {
-    if (this.storage.runExclusive !== undefined) {
-      return this.storage.runExclusive(scope, key, op);
+  withExclusiveKeyMutation<T>(
+    scope: string,
+    key: string,
+    mutation: () => Promise<T>,
+  ): Promise<T> {
+    if (this.storage.withExclusiveKeyMutation !== undefined) {
+      return this.storage.withExclusiveKeyMutation(scope, key, mutation);
     }
-    return enqueueKeyedOperation(this.operationQueues, `${scope}\0${key}`, op);
+    return enqueueKeyedOperation(this.operationQueues, `${scope}\0${key}`, mutation);
   }
 
   async delete(scope: string, key: string): Promise<void> {
diff --git a/packages/agent-core-v2/src/persistence/backends/node-fs/fileStorageService.ts b/packages/agent-core-v2/src/persistence/backends/node-fs/fileStorageService.ts
index 02564700d..cf9f7fd42 100644
--- a/packages/agent-core-v2/src/persistence/backends/node-fs/fileStorageService.ts
+++ b/packages/agent-core-v2/src/persistence/backends/node-fs/fileStorageService.ts
@@ -10,8 +10,9 @@
  *                fsync, so the replacement is both atomic and durable.
  *   - `append` → `open('a')` + write + `fh.sync()` (when `durable`), plus a
  *                one-time directory fsync per scope.
- *   - `runExclusive` → the shared cross-process lock protocol on
- *                      `<value-path>.lock`, bounding lock waits to 10 seconds.
+ *   - `withExclusiveKeyMutation` → the shared cross-process lock protocol
+ *                                  on `<value-path>.lock`, bounding waits to
+ *                                  10 seconds.
  *   - `watch`  → chokidar on the parent directory, filtered to the exact key and
  *                debounced, so it survives atomic-replace renames and observes a
  *                file that does not exist yet at subscription time.
@@ -21,8 +22,8 @@
  * agent-execution-environment abstraction does not expose. Higher-level code
  * (wire journal, blob store) goes through the Store / Storage interfaces above
  * this backend, never `node:fs` directly. Session-rooted mutations run through
- * the App-scoped write-gate registry, which rejects writes after sealing and
- * tracks admitted I/O until it settles.
+ * the App-scoped write admission, which rejects writes after sealing and
+ * tracks admitted physical I/O until it settles.
  */
 
 import { createReadStream, mkdirSync, statSync } from 'node:fs';
@@ -48,7 +49,7 @@ import type {
   StorageWriteOptions,
 } from '#/persistence/interface/storage';
 import { StorageError, StorageErrors, toStorageIoError } from '#/persistence/interface/storage';
-import { IWriteGateRegistry } from '#/persistence/interface/writeGate';
+import { IStorageWriteAdmission } from '#/persistence/interface/storageWriteAdmission';
 
 const WATCH_DEBOUNCE_MS = 150;
 const STORAGE_LOCK_WAIT_TIMEOUT_MS = 10_000;
@@ -78,8 +79,8 @@ export class FileStorageService implements IFileSystemStorageService {
     private readonly dirMode?: number,
     private readonly fileMode?: number,
     @optional(ICrossProcessLockService) private readonly locks?: ICrossProcessLockService,
-    @optional(IWriteGateRegistry)
-    private readonly writeGates?: IWriteGateRegistry,
+    @optional(IStorageWriteAdmission)
+    private readonly writeAdmission?: IStorageWriteAdmission,
   ) {}
 
   async read(scope: string, key: string): Promise<Uint8Array | undefined> {
@@ -119,7 +120,7 @@ export class FileStorageService implements IFileSystemStorageService {
     _options: StorageWriteOptions = {},
   ): Promise<void> {
     const filePath = this.path(scope, key);
-    await this.runWrite(scope, async () => {
+    await this.withPhysicalWrite(scope, async () => {
       try {
         await mkdir(dirname(filePath), { recursive: true, mode: this.dirMode });
         await atomicWrite(filePath, data, undefined, this.fileMode);
@@ -138,7 +139,7 @@ export class FileStorageService implements IFileSystemStorageService {
   ): Promise<void> {
     const filePath = this.path(scope, key);
     const dir = dirname(filePath);
-    await this.runWrite(scope, async () => {
+    await this.withPhysicalWrite(scope, async () => {
       try {
         await mkdir(dir, { recursive: true, mode: this.dirMode });
         const fh = await open(filePath, 'a', this.fileMode);
@@ -172,7 +173,7 @@ export class FileStorageService implements IFileSystemStorageService {
 
   async delete(scope: string, key: string): Promise<void> {
     const filePath = this.path(scope, key);
-    await this.runWrite(scope, async () => {
+    await this.withPhysicalWrite(scope, async () => {
       try {
         await unlink(filePath);
       } catch (error) {
@@ -254,10 +255,14 @@ export class FileStorageService implements IFileSystemStorageService {
     };
   }
 
-  async runExclusive<T>(scope: string, key: string, op: () => Promise<T>): Promise<T> {
+  async withExclusiveKeyMutation<T>(
+    scope: string,
+    key: string,
+    mutation: () => Promise<T>,
+  ): Promise<T> {
     const filePath = this.path(scope, key);
     const lockPath = `${filePath}.lock`;
-    await this.runWrite(scope, async () => {});
+    this.assertCanWriteNow(scope);
     if (this.locks === undefined) {
       throw new StorageError(
         StorageErrors.codes.STORAGE_IO_FAILED,
@@ -270,8 +275,8 @@ export class FileStorageService implements IFileSystemStorageService {
         lockPath,
         { wait: { timeoutMs: STORAGE_LOCK_WAIT_TIMEOUT_MS } },
         async () => {
-          await this.runWrite(scope, async () => {});
-          return op();
+          this.assertCanWriteNow(scope);
+          return mutation();
         },
       );
     } catch (error) {
@@ -302,8 +307,12 @@ export class FileStorageService implements IFileSystemStorageService {
     return join(this.baseDir, scope);
   }
 
-  private runWrite<T>(scope: string, write: () => Promise<T>): Promise<T> {
-    return this.writeGates?.run(scope, write) ?? write();
+  private assertCanWriteNow(scope: string): void {
+    this.writeAdmission?.assertCanWriteNow(scope);
+  }
+
+  private withPhysicalWrite<T>(scope: string, io: () => Promise<T>): Promise<T> {
+    return this.writeAdmission?.withPhysicalWrite(scope, io) ?? io();
   }
 
   private async syncDirOnce(dir: string): Promise<void> {
diff --git a/packages/agent-core-v2/src/persistence/backends/node-fs/storageWriteAdmissionService.ts b/packages/agent-core-v2/src/persistence/backends/node-fs/storageWriteAdmissionService.ts
new file mode 100644
index 000000000..2e0b997f9
--- /dev/null
+++ b/packages/agent-core-v2/src/persistence/backends/node-fs/storageWriteAdmissionService.ts
@@ -0,0 +1,76 @@
+/**
+ * `storage` domain (L1) — `IStorageWriteAdmission` implementation.
+ *
+ * Routes session-rooted storage scopes to admissions registered by session
+ * lifecycle. Double registration is a bug, missing session admissions fail
+ * closed, and root or non-session storage scopes execute directly. Bound at
+ * App scope.
+ */
+
+import { InstantiationType } from '#/_base/di/extensions';
+import { BugIndicatingError } from '#/_base/errors/errors';
+import { toDisposable, type IDisposable } from '#/_base/di/lifecycle';
+import { LifecycleScope, registerScopedService } from '#/_base/di/scope';
+import { Error2, ErrorCodes } from '#/errors';
+import type { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
+import { IStorageWriteAdmission } from '#/persistence/interface/storageWriteAdmission';
+
+export class StorageWriteAdmissionService implements IStorageWriteAdmission {
+  declare readonly _serviceBrand: undefined;
+
+  private readonly admissions = new Map<string, ISessionWriteAdmission>();
+
+  registerSession(sessionScope: string, admission: ISessionWriteAdmission): IDisposable {
+    if (this.admissions.has(sessionScope)) {
+      throw new BugIndicatingError(`write admission already registered for ${sessionScope}`);
+    }
+    this.admissions.set(sessionScope, admission);
+    return toDisposable(() => {
+      if (this.admissions.get(sessionScope) === admission) this.admissions.delete(sessionScope);
+    });
+  }
+
+  assertCanWriteNow(scope: string): void {
+    this.admissionFor(scope)?.assertCanWriteNow();
+  }
+
+  async withPhysicalWrite<T>(scope: string, io: () => Promise<T>): Promise<T> {
+    const admission = this.admissionFor(scope);
+    return admission === undefined ? io() : admission.withPhysicalWrite(io);
+  }
+
+  private admissionFor(scope: string): ISessionWriteAdmission | undefined {
+    const sessionScope = sessionScopeFromStorageScope(scope);
+    if (sessionScope === undefined) return undefined;
+    const admission = this.admissions.get(sessionScope);
+    if (admission === undefined) {
+      throw new Error2(ErrorCodes.SESSION_LEASE_LOST, 'session has no registered write admission', {
+        details: { sessionId: sessionScope.slice(sessionScope.lastIndexOf('/') + 1) },
+      });
+    }
+    return admission;
+  }
+}
+
+function sessionScopeFromStorageScope(scope: string): string | undefined {
+  if (scope === '') return undefined;
+  const parts = scope.split('/');
+  if (
+    parts.length < 3 ||
+    parts[0] !== 'sessions' ||
+    parts[1] === '' ||
+    parts[2] === undefined ||
+    parts[2] === ''
+  ) {
+    return undefined;
+  }
+  return parts.slice(0, 3).join('/');
+}
+
+registerScopedService(
+  LifecycleScope.App,
+  IStorageWriteAdmission,
+  StorageWriteAdmissionService,
+  InstantiationType.Eager,
+  'storage',
+);
diff --git a/packages/agent-core-v2/src/persistence/backends/node-fs/writeGateRegistryService.ts b/packages/agent-core-v2/src/persistence/backends/node-fs/writeGateRegistryService.ts
deleted file mode 100644
index 53e3eb262..000000000
--- a/packages/agent-core-v2/src/persistence/backends/node-fs/writeGateRegistryService.ts
+++ /dev/null
@@ -1,69 +0,0 @@
-/**
- * `storage` domain (L1) — `IWriteGateRegistry` implementation.
- *
- * Routes session-rooted storage scopes to the write gate registered by the
- * session lifecycle. Double registration is a bug, missing session gates fail
- * closed, and root or non-session storage scopes execute without a gate.
- * Bound at App scope.
- */
-
-import { BugIndicatingError } from '#/_base/errors/errors';
-import { InstantiationType } from '#/_base/di/extensions';
-import { toDisposable, type IDisposable } from '#/_base/di/lifecycle';
-import { LifecycleScope, registerScopedService } from '#/_base/di/scope';
-import { Error2, ErrorCodes } from '#/errors';
-import {
-  type ISessionWriteGate,
-  IWriteGateRegistry,
-} from '#/persistence/interface/writeGate';
-
-export class WriteGateRegistryService implements IWriteGateRegistry {
-  declare readonly _serviceBrand: undefined;
-
-  private readonly gates = new Map<string, ISessionWriteGate>();
-
-  register(sessionScope: string, gate: ISessionWriteGate): IDisposable {
-    if (this.gates.has(sessionScope)) {
-      throw new BugIndicatingError(`write gate already registered for ${sessionScope}`);
-    }
-    this.gates.set(sessionScope, gate);
-    return toDisposable(() => {
-      if (this.gates.get(sessionScope) === gate) this.gates.delete(sessionScope);
-    });
-  }
-
-  async run<T>(scope: string, write: () => Promise<T>): Promise<T> {
-    const sessionScope = sessionScopeFromStorageScope(scope);
-    if (sessionScope === undefined) return write();
-    const gate = this.gates.get(sessionScope);
-    if (gate === undefined) {
-      throw new Error2(ErrorCodes.SESSION_LEASE_LOST, 'session has no registered write gate', {
-        details: { sessionId: sessionScope.slice(sessionScope.lastIndexOf('/') + 1) },
-      });
-    }
-    return gate.run(write);
-  }
-}
-
-function sessionScopeFromStorageScope(scope: string): string | undefined {
-  if (scope === '') return undefined;
-  const parts = scope.split('/');
-  if (
-    parts.length < 3 ||
-    parts[0] !== 'sessions' ||
-    parts[1] === '' ||
-    parts[2] === undefined ||
-    parts[2] === ''
-  ) {
-    return undefined;
-  }
-  return parts.slice(0, 3).join('/');
-}
-
-registerScopedService(
-  LifecycleScope.App,
-  IWriteGateRegistry,
-  WriteGateRegistryService,
-  InstantiationType.Eager,
-  'storage',
-);
diff --git a/packages/agent-core-v2/src/persistence/interface/atomicDocumentStore.ts b/packages/agent-core-v2/src/persistence/interface/atomicDocumentStore.ts
index 2a413f13a..88792a252 100644
--- a/packages/agent-core-v2/src/persistence/interface/atomicDocumentStore.ts
+++ b/packages/agent-core-v2/src/persistence/interface/atomicDocumentStore.ts
@@ -29,7 +29,11 @@ export interface IAtomicDocumentStore {
     key: string,
     mutate: (current: T | undefined) => T | Promise<T>,
   ): Promise<T>;
-  runExclusive<T>(scope: string, key: string, op: () => Promise<T>): Promise<T>;
+  withExclusiveKeyMutation<T>(
+    scope: string,
+    key: string,
+    mutation: () => Promise<T>,
+  ): Promise<T>;
   delete(scope: string, key: string): Promise<void>;
   list(scope: string, prefix?: string): Promise<readonly string[]>;
   watch(scope: string, key: string): Event<void>;
diff --git a/packages/agent-core-v2/src/persistence/interface/sessionWriteAdmission.ts b/packages/agent-core-v2/src/persistence/interface/sessionWriteAdmission.ts
new file mode 100644
index 000000000..77a7ea0f5
--- /dev/null
+++ b/packages/agent-core-v2/src/persistence/interface/sessionWriteAdmission.ts
@@ -0,0 +1,19 @@
+/**
+ * `storage` domain (L1) — per-session physical-write admission contract.
+ *
+ * Defines the Session-scoped admission capability used to reject new writes
+ * after sealing, track admitted physical I/O, and await its drain.
+ */
+
+import { createDecorator, type ServiceIdentifier } from '#/_base/di/instantiation';
+
+export interface ISessionWriteAdmission {
+  readonly _serviceBrand: undefined;
+
+  assertCanWriteNow(): void;
+  withPhysicalWrite<T>(io: () => Promise<T>): Promise<T>;
+  sealAndDrain(): Promise<void>;
+}
+
+export const ISessionWriteAdmission: ServiceIdentifier<ISessionWriteAdmission> =
+  createDecorator<ISessionWriteAdmission>('sessionWriteAdmission');
diff --git a/packages/agent-core-v2/src/persistence/interface/storage.ts b/packages/agent-core-v2/src/persistence/interface/storage.ts
index 5bbe5a849..c3b7392fc 100644
--- a/packages/agent-core-v2/src/persistence/interface/storage.ts
+++ b/packages/agent-core-v2/src/persistence/interface/storage.ts
@@ -7,8 +7,9 @@
  *
  *   - `write`  — atomic whole-value replacement (the `Config` access pattern).
  *   - `append` — ordered, durable byte extension   (the `Record` access pattern).
- *   - `runExclusive` — keyed read-modify-write exclusion when the backend can
- *                      coordinate independent processes.
+ *   - `withExclusiveKeyMutation` — keyed read-modify-write exclusion when the
+ *                                  backend can coordinate independent
+ *                                  processes.
  *
  * They are not interchangeable: building `append` on top of `write` is O(n)
  * per append, and building `write` on top of `append` yields awkward "read
@@ -130,7 +131,11 @@ export interface IFileSystemStorageService {
   list(scope: string, prefix?: string): Promise<readonly string[]>;
   delete(scope: string, key: string): Promise<void>;
   watch?(scope: string, key: string): Event<void>;
-  runExclusive?<T>(scope: string, key: string, op: () => Promise<T>): Promise<T>;
+  withExclusiveKeyMutation?<T>(
+    scope: string,
+    key: string,
+    mutation: () => Promise<T>,
+  ): Promise<T>;
   flush(): Promise<void>;
   close(): Promise<void>;
 }
diff --git a/packages/agent-core-v2/src/persistence/interface/storageWriteAdmission.ts b/packages/agent-core-v2/src/persistence/interface/storageWriteAdmission.ts
new file mode 100644
index 000000000..64e9e29c5
--- /dev/null
+++ b/packages/agent-core-v2/src/persistence/interface/storageWriteAdmission.ts
@@ -0,0 +1,22 @@
+/**
+ * `storage` domain (L1) — App-scoped storage write-admission contract.
+ *
+ * Routes session-rooted storage scopes to their per-session admission while
+ * leaving root and non-session scopes unrestricted. Missing session
+ * registrations fail closed.
+ */
+
+import { createDecorator, type ServiceIdentifier } from '#/_base/di/instantiation';
+import type { IDisposable } from '#/_base/di/lifecycle';
+import type { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
+
+export interface IStorageWriteAdmission {
+  readonly _serviceBrand: undefined;
+
+  registerSession(sessionScope: string, admission: ISessionWriteAdmission): IDisposable;
+  assertCanWriteNow(scope: string): void;
+  withPhysicalWrite<T>(scope: string, io: () => Promise<T>): Promise<T>;
+}
+
+export const IStorageWriteAdmission: ServiceIdentifier<IStorageWriteAdmission> =
+  createDecorator<IStorageWriteAdmission>('storageWriteAdmission');
diff --git a/packages/agent-core-v2/src/persistence/interface/writeGate.ts b/packages/agent-core-v2/src/persistence/interface/writeGate.ts
deleted file mode 100644
index 6e871e056..000000000
--- a/packages/agent-core-v2/src/persistence/interface/writeGate.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-/**
- * `persistence/interface` — session write-admission gate contract.
- *
- * Defines the per-session `ISessionWriteGate` that fences and tracks physical
- * writes, plus the App-scoped `IWriteGateRegistry` used by storage backends to
- * route a storage scope to its owning session gate. Session scopes without a
- * registered gate fail closed; root and non-session scopes are not gated.
- */
-
-import { createDecorator, type ServiceIdentifier } from '#/_base/di/instantiation';
-import type { IDisposable } from '#/_base/di/lifecycle';
-
-export interface ISessionWriteGate {
-  run<T>(write: () => Promise<T>): Promise<T>;
-  seal(): void;
-  drained(): Promise<void>;
-}
-
-export const ISessionWriteGate: ServiceIdentifier<ISessionWriteGate> =
-  createDecorator<ISessionWriteGate>('sessionWriteGate');
-
-export const IWriteGateRegistry: ServiceIdentifier<IWriteGateRegistry> =
-  createDecorator<IWriteGateRegistry>('writeGateRegistry');
-
-export interface IWriteGateRegistry {
-  readonly _serviceBrand: undefined;
-
-  register(sessionScope: string, gate: ISessionWriteGate): IDisposable;
-  run<T>(scope: string, write: () => Promise<T>): Promise<T>;
-}
diff --git a/packages/agent-core-v2/src/session/sessionLease/sessionLease.ts b/packages/agent-core-v2/src/session/sessionLease/sessionLease.ts
index 16b04d8fc..1cc1a9c15 100644
--- a/packages/agent-core-v2/src/session/sessionLease/sessionLease.ts
+++ b/packages/agent-core-v2/src/session/sessionLease/sessionLease.ts
@@ -3,7 +3,7 @@
  *
  * Defines `ISessionLeaseService`, the Session-scope seeded ownership view,
  * and the `SessionLease` object that satisfies it together with the
- * `ISessionWriteGate` used by storage: an App-owned wrapper
+ * `ISessionWriteAdmission` used by storage: an App-owned wrapper
  * (`SessionLifecycleService` builds it; it is deliberately not a DI service)
  * around the cross-process lock handle at
  * `<homeDir>/session-leases/<sessionId>.lock`. `assertWritable` is the hard
@@ -11,7 +11,8 @@
  * sentinel fails closed with
  * `session.lease_lost`, marks the lease lost, seals write admission, and fires
  * the loss callback exactly once so the owning session tears itself down.
- * The gate tracks admitted writes so lifecycle release can await their drain.
+ * The admission tracks physical writes so lifecycle release can await their
+ * drain.
  *
  * No default is registered for either Session-scoped view: every production
  * session scope is seeded by `sessionLifecycle` via {@link sessionLeaseSeed};
@@ -28,7 +29,7 @@ import type {
   CrossProcessLockInspection,
   ICrossProcessLockHandle,
 } from '#/os/interface/crossProcessLock';
-import { ISessionWriteGate } from '#/persistence/interface/writeGate';
+import { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
 
 export const LEASE_CREATING_RETRY_AFTER_MS = 1000;
 
@@ -100,7 +101,7 @@ export interface ISessionLeaseService {
 export const ISessionLeaseService: ServiceIdentifier<ISessionLeaseService> =
   createDecorator<ISessionLeaseService>('sessionLeaseService');
 
-export class SessionLease implements ISessionWriteGate, ISessionLeaseService {
+export class SessionLease implements ISessionWriteAdmission, ISessionLeaseService {
   declare readonly _serviceBrand: undefined;
 
   readonly lockId: string;
@@ -145,12 +146,16 @@ export class SessionLease implements ISessionWriteGate, ISessionLeaseService {
     }
   }
 
-  async run<T>(write: () => Promise<T>): Promise<T> {
-    if (this._sealed) throw this.writeGateClosedError();
+  assertCanWriteNow(): void {
+    if (this._sealed) throw this.writeAdmissionClosedError();
     this.assertWritable();
+  }
+
+  async withPhysicalWrite<T>(io: () => Promise<T>): Promise<T> {
+    this.assertCanWriteNow();
     this.inFlightWrites++;
     try {
-      return await write();
+      return await io();
     } finally {
       this.inFlightWrites--;
       if (this.inFlightWrites === 0) {
@@ -160,28 +165,33 @@ export class SessionLease implements ISessionWriteGate, ISessionLeaseService {
     }
   }
 
-  seal(): void {
+  sealAndDrain(): Promise<void> {
+    this.sealWrites();
+    return this.whenDrained();
+  }
+
+  private sealWrites(): void {
     this._sealed = true;
   }
 
-  drained(): Promise<void> {
+  private whenDrained(): Promise<void> {
     if (this.inFlightWrites === 0) return Promise.resolve();
     return new Promise<void>((resolve) => {
       this.drainWaiters.add(resolve);
     });
   }
 
-  private writeGateClosedError(): Error2 {
+  private writeAdmissionClosedError(): Error2 {
     return new Error2(
       ErrorCodes.SESSION_LEASE_LOST,
-      `session ${this.sessionId} write gate is sealed`,
+      `session ${this.sessionId} write admission is sealed`,
       { details: { sessionId: this.sessionId } },
     );
   }
 
   private markLost(): void {
     this._lost = true;
-    this.seal();
+    this.sealWrites();
     if (this._lossFired) return;
     this._lossFired = true;
     this.onLeaseLost(this.sessionId);
@@ -189,7 +199,7 @@ export class SessionLease implements ISessionWriteGate, ISessionLeaseService {
 
   release(): void {
     if (this._released) return;
-    this.seal();
+    this.sealWrites();
     this._released = true;
     this.handle.release();
   }
@@ -202,6 +212,6 @@ export function sessionLeasePath(homeDir: string, sessionId: string): string {
 export function sessionLeaseSeed(lease: SessionLease): ScopeSeed {
   return [
     [ISessionLeaseService as ServiceIdentifier<unknown>, lease],
-    [ISessionWriteGate as ServiceIdentifier<unknown>, lease],
+    [ISessionWriteAdmission as ServiceIdentifier<unknown>, lease],
   ];
 }
diff --git a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
index 9c2c4eb68..f1f3a21b3 100644
--- a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
+++ b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
@@ -14,7 +14,7 @@
  * a no-op (no write, no mirror, no event), so resuming a session — which
  * re-registers its agents as they materialize — never bumps `updatedAt` and
  * never reorders session listings. Every durable write is fenced by the
- * storage backend's per-session write gate, so an instance that lost or
+ * storage backend's per-session write admission, so an instance that lost or
  * released the session lease fails closed instead of overwriting a live
  * peer's state. Bound at Session scope.
  *
diff --git a/packages/agent-core-v2/test/agent/profile/binding.test.ts b/packages/agent-core-v2/test/agent/profile/binding.test.ts
index 8e2f4545c..2bf212f1e 100644
--- a/packages/agent-core-v2/test/agent/profile/binding.test.ts
+++ b/packages/agent-core-v2/test/agent/profile/binding.test.ts
@@ -52,6 +52,16 @@ function createAtomicDocumentStore(): AtomicDocumentStore {
     set: async <T>(scope: string, key: string, value: T) => {
       documents.set(documentKey(scope, key), structuredClone(value));
     },
+    update: async <T>(scope: string, key: string, mutate: (current: T | undefined) => T | Promise<T>) => {
+      const next = await mutate(documents.get(documentKey(scope, key)) as T | undefined);
+      documents.set(documentKey(scope, key), structuredClone(next));
+      return next;
+    },
+    withExclusiveKeyMutation: async <T>(
+      _scope: string,
+      _key: string,
+      mutation: () => Promise<T>,
+    ) => mutation(),
     delete: async (scope: string, key: string) => {
       documents.delete(documentKey(scope, key));
     },
diff --git a/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts b/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
index 75030dbc9..aff67f27d 100644
--- a/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
+++ b/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
@@ -46,10 +46,11 @@ import { IAppendLogStore } from '#/persistence/interface/appendLogStore';
 import { IAtomicDocumentStore } from '#/persistence/interface/atomicDocumentStore';
 import { IProjectLocalConfigService } from '#/app/projectLocalConfig/projectLocalConfig';
 import { JsonAtomicDocumentStore } from '#/persistence/backends/node-fs/atomicDocumentStore';
-import { ISessionWriteGate, IWriteGateRegistry } from '#/persistence/interface/writeGate';
+import { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
+import { IStorageWriteAdmission } from '#/persistence/interface/storageWriteAdmission';
 import { AppendLogStore } from '#/persistence/backends/node-fs/appendLogStore';
 import { FileStorageService } from '#/persistence/backends/node-fs/fileStorageService';
-import { WriteGateRegistryService } from '#/persistence/backends/node-fs/writeGateRegistryService';
+import { StorageWriteAdmissionService } from '#/persistence/backends/node-fs/storageWriteAdmissionService';
 import { ISessionWorkspaceContext } from '#/session/workspaceContext/workspaceContext';
 import { SessionWorkspaceContextService } from '#/session/workspaceContext/workspaceContextService';
 import { IWorkspaceService, type Workspace } from '#/app/workspace/workspace';
@@ -300,7 +301,7 @@ function atomicDocumentStoreStub(): IAtomicDocumentStore {
     get: () => Promise.resolve(undefined),
     set: () => Promise.resolve(),
     update: (_scope, _key, mutate) => Promise.resolve(mutate(undefined)),
-    runExclusive: (_scope, _key, op) => op(),
+    withExclusiveKeyMutation: (_scope, _key, mutation) => mutation(),
     delete: () => Promise.resolve(),
     list: () => Promise.resolve([]),
     watch: () => (_listener) => ({ dispose: () => {} }),
@@ -513,7 +514,7 @@ describe('SessionLifecycleService', () => {
       stubPair(ILogService, stubLog()),
       stubPair(IFlagService, stubFlag(false)),
       stubPair(ICrossProcessLockService, stubCrossProcessLock()),
-      stubPair(IWriteGateRegistry, new WriteGateRegistryService()),
+      stubPair(IStorageWriteAdmission, new StorageWriteAdmissionService()),
       stubPair(ISessionLeaseContactProvider, new SessionLeaseContactProvider()),
       ...extra,
     ]);
@@ -1370,7 +1371,7 @@ describe('SessionLifecycleService', () => {
       return [
         stubPair(IBootstrapService, tmpBootstrapStub(root)),
         stubPair(ICrossProcessLockService, new CrossProcessLockService()),
-        stubPair(IWriteGateRegistry, new WriteGateRegistryService()),
+        stubPair(IStorageWriteAdmission, new StorageWriteAdmissionService()),
         ...over,
       ];
     }
@@ -1378,11 +1379,11 @@ describe('SessionLifecycleService', () => {
     function realAlsSeeds(root: string): {
       seeds: ReturnType<typeof stubPair>[];
       appendLog: AppendLogStore;
-      registry: WriteGateRegistryService;
+      registry: StorageWriteAdmissionService;
       storage: FileStorageService;
       docs: JsonAtomicDocumentStore;
     } {
-      const registry = new WriteGateRegistryService();
+      const registry = new StorageWriteAdmissionService();
       const locks = new CrossProcessLockService();
       const storage = new FileStorageService(root, undefined, undefined, locks, registry);
       const appendLog = new AppendLogStore(storage);
@@ -1391,7 +1392,7 @@ describe('SessionLifecycleService', () => {
         seeds: [
           stubPair(IBootstrapService, tmpBootstrapStub(root)),
           stubPair(ICrossProcessLockService, locks),
-          stubPair(IWriteGateRegistry, registry),
+          stubPair(IStorageWriteAdmission, registry),
           stubPair(IAppendLogStore, appendLog),
           stubPair(IAtomicDocumentStore, docs),
         ],
@@ -1574,7 +1575,7 @@ describe('SessionLifecycleService', () => {
       const root = await makeTmpRoot();
       const svc = build(realInstanceSeeds(root));
       const handle = await svc.create({ sessionId: 's1', workDir: '/tmp/proj' });
-      const writeGate = handle.accessor.get(ISessionWriteGate);
+      const writeAdmission = handle.accessor.get(ISessionWriteAdmission);
       let finishWrite!: () => void;
       const writeBlocked = new Promise<void>((resolve) => {
         finishWrite = resolve;
@@ -1583,7 +1584,7 @@ describe('SessionLifecycleService', () => {
       const writeEntered = new Promise<void>((resolve) => {
         enterWrite = resolve;
       });
-      const write = writeGate.run(async () => {
+      const write = writeAdmission.withPhysicalWrite(async () => {
         enterWrite();
         await writeBlocked;
       });
@@ -1596,7 +1597,7 @@ describe('SessionLifecycleService', () => {
       let sealed = false;
       for (let attempt = 0; attempt < 10 && !sealed; attempt++) {
         try {
-          await writeGate.run(async () => {});
+          writeAdmission.assertCanWriteNow();
         } catch (error) {
           expect(error).toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
           sealed = true;
@@ -1629,7 +1630,7 @@ describe('SessionLifecycleService', () => {
       });
       expect(svc.get('s1')).toBeUndefined();
       await expect(
-        registry.run('sessions/wd_stub/s1/agents/main', async () => {}),
+        registry.withPhysicalWrite('sessions/wd_stub/s1/agents/main', async () => {}),
       ).rejects.toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
       expect(await docs.get<{ custom?: { dirtyAbort?: { reason?: string } } }>(
         'sessions/wd_stub/s1',
@@ -1674,7 +1675,7 @@ describe('SessionLifecycleService', () => {
       await svc.closeAll();
 
       await expect(
-        registry.run('sessions/wd_stub/s1', async () => {}),
+        registry.withPhysicalWrite('sessions/wd_stub/s1', async () => {}),
       ).rejects.toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
       expect(await docs.get<{ custom?: { dirtyAbort?: { reason?: string } } }>(
         'sessions/wd_stub/s1',
@@ -1692,7 +1693,7 @@ describe('SessionLifecycleService', () => {
       await Promise.all([svc.close('s1'), svc.closeAll()]);
 
       await expect(
-        registry.run('sessions/wd_stub/s1', async () => {}),
+        registry.withPhysicalWrite('sessions/wd_stub/s1', async () => {}),
       ).rejects.toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
       await expectLeaseFree(root, 's1');
     });
diff --git a/packages/agent-core-v2/test/harness/agent.ts b/packages/agent-core-v2/test/harness/agent.ts
index 274c70a19..99eadc118 100644
--- a/packages/agent-core-v2/test/harness/agent.ts
+++ b/packages/agent-core-v2/test/harness/agent.ts
@@ -111,6 +111,7 @@ import {
   ISessionBtwService,
   ISessionContext,
   ISessionLeaseService,
+  ISessionWriteAdmission,
   ISessionProcessRunner,
   IAgentScopeContext,
   IAgentShellCommandService,
@@ -124,6 +125,7 @@ import {
   IAgentBuiltinToolsRegistrar,
   IAgentUserToolService,
   IAgentUsageService,
+  IStorageWriteAdmission,
   ISessionWorkspaceContext,
   AgentLLMRequesterService,
   LifecycleScope,
@@ -532,7 +534,7 @@ export function homeDirServices(homeDir: string | undefined): TestAgentServiceOv
         reg.defineInstance(id, value);
       }
       const file = (): SyncDescriptor<IFileSystemStorageService> =>
-        new SyncDescriptor(FileStorageService, [homeDir], true);
+        new SyncDescriptor(FileStorageService, [homeDir, undefined, undefined], true);
       reg.defineDescriptor(IFileSystemStorageService, file());
       reg.define(IBlobStore, BlobStoreService);
     }
@@ -956,6 +958,7 @@ export class AgentTestContext {
   private readonly root: Scope;
   private readonly session: Scope;
   private readonly agent: Scope;
+  private readonly sessionWriteAdmissionRegistration: IDisposable;
   private readonly disposables: IDisposable[] = [];
   private suppressWireSnapshot = false;
   private pluginSessionStartRegistered = false;
@@ -1072,6 +1075,10 @@ export class AgentTestContext {
       .get(ITelemetryService)
       .withContext({ agent_id: agentId });
     const sessionScope = bootstrap.sessionScope(workspaceId, sessionId);
+    const sessionLease = stubSessionLeaseService();
+    this.sessionWriteAdmissionRegistration = this.root.accessor
+      .get(IStorageWriteAdmission)
+      .registerSession(sessionScope, sessionLease);
     this.session = this.root.createChild(LifecycleScope.Session, sessionId, {
       extra: collectScopeSeed(
         [
@@ -1086,7 +1093,8 @@ export class AgentTestContext {
               scope: (subKey?: string): string =>
                 subKey === undefined || subKey === '' ? sessionScope : `${sessionScope}/${subKey}`,
             });
-            reg.defineInstance(ISessionLeaseService, stubSessionLeaseService());
+            reg.defineInstance(ISessionLeaseService, sessionLease);
+            reg.defineInstance(ISessionWriteAdmission, sessionLease);
             reg.defineInstance(ISessionInteractionService, this.createInteractionService());
             reg.defineInstance(ISessionApprovalService, this.createApprovalService());
             reg.defineInstance(ISessionQuestionService, this.createQuestionService());
@@ -1701,6 +1709,7 @@ export class AgentTestContext {
       disposable.dispose();
     }
     await this.closeWire();
+    this.sessionWriteAdmissionRegistration.dispose();
     this.root.dispose();
   }
 
diff --git a/packages/agent-core-v2/test/persistence/backends/node-fs/fileStorageService.test.ts b/packages/agent-core-v2/test/persistence/backends/node-fs/fileStorageService.test.ts
index 0ab05893d..d53f1e6ec 100644
--- a/packages/agent-core-v2/test/persistence/backends/node-fs/fileStorageService.test.ts
+++ b/packages/agent-core-v2/test/persistence/backends/node-fs/fileStorageService.test.ts
@@ -5,9 +5,10 @@ import { join } from 'pathe';
 import { afterEach, beforeEach, describe, expect, it } from 'vitest';
 
 import { Error2, ErrorCodes } from '#/errors';
+import { CrossProcessLockService } from '#/os/backends/node-local/crossProcessLockService';
 import { FileStorageService } from '#/persistence/backends/node-fs/fileStorageService';
-import { WriteGateRegistryService } from '#/persistence/backends/node-fs/writeGateRegistryService';
-import type { ISessionWriteGate } from '#/persistence/interface/writeGate';
+import { StorageWriteAdmissionService } from '#/persistence/backends/node-fs/storageWriteAdmissionService';
+import type { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
 
 const isWin = process.platform === 'win32';
 const encoder = new TextEncoder();
@@ -91,7 +92,7 @@ describe('FileStorageService — error translation', () => {
   });
 });
 
-describe('FileStorageService — session write fencing', () => {
+describe('FileStorageService — session write admission', () => {
   let dir: string;
 
   beforeEach(async () => {
@@ -102,21 +103,25 @@ describe('FileStorageService — session write fencing', () => {
     await rm(dir, { recursive: true, force: true });
   });
 
-  it('runs write, append, and delete through the session gate', async () => {
-    const registry = new WriteGateRegistryService();
+  it('runs write, append, and delete through session write admission', async () => {
+    const registry = new StorageWriteAdmissionService();
     let writable = true;
-    const gate: ISessionWriteGate = {
-      run: async (write) => {
-        if (!writable) {
-          throw new Error2(ErrorCodes.SESSION_LEASE_LOST, 'session lease lost');
-        }
-        return write();
-      },
-      seal: () => {},
-      drained: async () => {},
+    const assertCanWriteNow = (): void => {
+      if (!writable) {
+        throw new Error2(ErrorCodes.SESSION_LEASE_LOST, 'session lease lost');
+      }
     };
-    const registration = registry.register('sessions/workspace/session', gate);
-    expect(() => registry.register('sessions/workspace/session', gate)).toThrow(
+    const admission: ISessionWriteAdmission = {
+      _serviceBrand: undefined,
+      assertCanWriteNow,
+      withPhysicalWrite: async (io) => {
+        assertCanWriteNow();
+        return io();
+      },
+      sealAndDrain: async () => {},
+    };
+    const registration = registry.registerSession('sessions/workspace/session', admission);
+    expect(() => registry.registerSession('sessions/workspace/session', admission)).toThrow(
       /already registered/,
     );
     const svc = new FileStorageService(dir, undefined, undefined, undefined, registry);
@@ -143,8 +148,8 @@ describe('FileStorageService — session write fencing', () => {
     });
   });
 
-  it('fails closed without a session gate and leaves non-session scopes untouched', async () => {
-    const registry = new WriteGateRegistryService();
+  it('fails closed without session admission and leaves non-session scopes unrestricted', async () => {
+    const registry = new StorageWriteAdmissionService();
     const svc = new FileStorageService(dir, undefined, undefined, undefined, registry);
 
     await expect(
@@ -152,4 +157,43 @@ describe('FileStorageService — session write fencing', () => {
     ).rejects.toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
     await expect(svc.write('cron/workspace', 'task.json', encoder.encode('{}'))).resolves.toBeUndefined();
   });
+
+  it('revalidates session admission after acquiring the exclusive key mutation', async () => {
+    const registry = new StorageWriteAdmissionService();
+    let checks = 0;
+    const admission: ISessionWriteAdmission = {
+      _serviceBrand: undefined,
+      assertCanWriteNow: () => {
+        checks++;
+        if (checks > 1) {
+          throw new Error2(
+            ErrorCodes.SESSION_LEASE_LOST,
+            'session admission sealed while waiting',
+          );
+        }
+      },
+      withPhysicalWrite: (io) => io(),
+      sealAndDrain: async () => {},
+    };
+    registry.registerSession('sessions/workspace/session', admission);
+    const svc = new FileStorageService(
+      dir,
+      undefined,
+      undefined,
+      new CrossProcessLockService(),
+      registry,
+    );
+    let mutationRan = false;
+
+    await expect(
+      svc.withExclusiveKeyMutation(
+        'sessions/workspace/session',
+        'state.json',
+        async () => {
+          mutationRan = true;
+        },
+      ),
+    ).rejects.toMatchObject({ code: ErrorCodes.SESSION_LEASE_LOST });
+    expect(mutationRan).toBe(false);
+  });
 });
diff --git a/packages/agent-core-v2/test/session/agentLifecycle/agentLifecycle.test.ts b/packages/agent-core-v2/test/session/agentLifecycle/agentLifecycle.test.ts
index da0f93ec7..a82b3c78d 100644
--- a/packages/agent-core-v2/test/session/agentLifecycle/agentLifecycle.test.ts
+++ b/packages/agent-core-v2/test/session/agentLifecycle/agentLifecycle.test.ts
@@ -221,8 +221,11 @@ describe('AgentLifecycleService', () => {
         atomicDocs.set(`${scope}/${key}`, next);
         return next;
       },
-      runExclusive: async <T>(_scope: string, _key: string, op: () => Promise<T>): Promise<T> =>
-        op(),
+      withExclusiveKeyMutation: async <T>(
+        _scope: string,
+        _key: string,
+        mutation: () => Promise<T>,
+      ): Promise<T> => mutation(),
       delete: async (scope: string, key: string): Promise<void> => {
         atomicDocs.delete(`${scope}/${key}`);
       },
diff --git a/packages/agent-core-v2/test/session/sessionLease/sessionLease.test.ts b/packages/agent-core-v2/test/session/sessionLease/sessionLease.test.ts
index 1cf4617db..df3f10695 100644
--- a/packages/agent-core-v2/test/session/sessionLease/sessionLease.test.ts
+++ b/packages/agent-core-v2/test/session/sessionLease/sessionLease.test.ts
@@ -71,28 +71,27 @@ describe('SessionLease', () => {
     expect(thrownError(() => lease.assertWritable()).code).toBe(ErrorCodes.SESSION_LEASE_LOST);
   });
 
-  it('seal rejects new writes while drained waits for an admitted write', async () => {
+  it('sealAndDrain rejects new writes while waiting for an admitted physical write', async () => {
     const lease = await acquire();
     let enterWrite!: () => void;
     const writeEntered = new Promise<void>((resolve) => {
       enterWrite = resolve;
     });
     let finishWrite!: () => void;
-    const writeGate = new Promise<void>((resolve) => {
+    const physicalWriteBlocked = new Promise<void>((resolve) => {
       finishWrite = resolve;
     });
-    const write = lease.run(async () => {
+    const write = lease.withPhysicalWrite(async () => {
       enterWrite();
-      await writeGate;
+      await physicalWriteBlocked;
     });
     await writeEntered;
 
-    lease.seal();
     let drained = false;
-    const drain = lease.drained().then(() => {
+    const drain = lease.sealAndDrain().then(() => {
       drained = true;
     });
-    await expect(lease.run(async () => {})).rejects.toMatchObject({
+    await expect(lease.withPhysicalWrite(async () => {})).rejects.toMatchObject({
       code: ErrorCodes.SESSION_LEASE_LOST,
     });
     expect(drained).toBe(false);
diff --git a/packages/agent-core-v2/test/session/sessionLease/stubs.ts b/packages/agent-core-v2/test/session/sessionLease/stubs.ts
index c03a39bf6..da90cfe4c 100644
--- a/packages/agent-core-v2/test/session/sessionLease/stubs.ts
+++ b/packages/agent-core-v2/test/session/sessionLease/stubs.ts
@@ -1,20 +1,28 @@
 /**
- * `sessionLease` test stubs — no-op `ISessionLeaseService` for unit tests.
+ * `sessionLease` test stubs — no-op session lease and write admission.
  *
  * Lives under `test/` (not `src/`). The default stub reports no lease info
- * and passes every `assertWritable` gate; tests that exercise fencing pass an
- * `assertWritable` override that throws. Import from a relative path.
+ * and admits every write; tests that exercise fencing override the relevant
+ * gate. Import from a relative path.
  */
 
+import type { ISessionWriteAdmission } from '#/persistence/interface/sessionWriteAdmission';
 import { ISessionLeaseService } from '#/session/sessionLease/sessionLease';
 
 export function stubSessionLeaseService(
-  overrides: Partial<ISessionLeaseService> = {},
-): ISessionLeaseService {
-  return {
+  overrides: Partial<ISessionLeaseService & ISessionWriteAdmission> = {},
+): ISessionLeaseService & ISessionWriteAdmission {
+  const lease: ISessionLeaseService & ISessionWriteAdmission = {
     _serviceBrand: undefined,
     info: undefined,
     assertWritable: () => {},
+    assertCanWriteNow: () => lease.assertWritable(),
+    withPhysicalWrite: async (io) => {
+      lease.assertCanWriteNow();
+      return io();
+    },
+    sealAndDrain: async () => {},
     ...overrides,
   };
+  return lease;
 }