diff --git a/.changeset/quiet-locks-follow-state.md b/.changeset/quiet-locks-follow-state.md
new file mode 100644
index 000000000..4c4df8bb5
--- /dev/null
+++ b/.changeset/quiet-locks-follow-state.md
@@ -0,0 +1,5 @@
+---
+'@bradygaster/squad-sdk': patch
+---
+
+Coordinate memory index locks with the configured state backend.
diff --git a/packages/squad-sdk/src/memory/index.ts b/packages/squad-sdk/src/memory/index.ts
index b9e065d7e..d63f07597 100644
--- a/packages/squad-sdk/src/memory/index.ts
+++ b/packages/squad-sdk/src/memory/index.ts
@@ -536,6 +536,11 @@ export const REAL_COPILOT_UNAVAILABLE_REASON =
 const HOST_INJECTED_CLIENT_MISSING_REASON =
   'hostInjectedCopilotAdapter is enabled, but no host-injected Copilot memory client was supplied. This is not real provider=copilot persistence.';
 
+type MemoryIndexLockStore = { lockAsync?: (key: string) => Promise<() => void> };
+type MemoryIndexLockProvider = {
+  createLockStore?: (lockAnchor: string) => MemoryIndexLockStore | Promise<MemoryIndexLockStore>;
+};
+
 function isRealCopilotProviderSelected(config: MemoryGovernanceConfig): boolean {
   return config.defaultProvider === 'copilot';
 }
@@ -650,18 +655,22 @@ export class LocalMemoryStore {
    *
    * All callers that do readIndex() → mutate → writeIndex() must go through
    * this method so concurrent writers cannot interleave and lose entries.
-   * The file lock coordinates callers across store instances and processes
-   * sharing the same .squad directory.
+   * Backend adapters coordinate on the shared state ref; filesystem storage
+   * keeps its lock under the resolved .squad directory.
    */
   private async withIndexLock<T>(fn: () => Promise<T>): Promise<T> {
-    const resolvedSquadDir = path.resolve(this.squadDir);
-    let lockRoot = resolvedSquadDir;
-    try {
-      lockRoot = await realpath(resolvedSquadDir);
-    } catch (error) {
-      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error;
+    const lockProvider = this.storage as StorageProvider & MemoryIndexLockProvider;
+    let fileLock = await lockProvider.createLockStore?.(this.squadDir);
+    if (!fileLock) {
+      const resolvedSquadDir = path.resolve(this.squadDir);
+      let lockRoot = resolvedSquadDir;
+      try {
+        lockRoot = await realpath(resolvedSquadDir);
+      } catch (error) {
+        if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error;
+      }
+      fileLock = createFileStateStore(lockRoot);
     }
-    const fileLock = createFileStateStore(lockRoot);
     const releaseFileLock = await fileLock.lockAsync!('backend/locks/memory-index');
     try {
       return await fn();
diff --git a/packages/squad-sdk/src/state-backend.ts b/packages/squad-sdk/src/state-backend.ts
index 246ea6d6c..c5a35d0cb 100644
--- a/packages/squad-sdk/src/state-backend.ts
+++ b/packages/squad-sdk/src/state-backend.ts
@@ -14,6 +14,7 @@ import path from 'node:path';
 import { FSStorageProvider } from './storage/fs-storage-provider.js';
 import type { StorageProvider, StorageStats } from './storage/storage-provider.js';
 import { StateKeyConflictError, StateBackendUncertaintyError } from './storage/storage-error.js';
+import type { BackendStateStore } from './backend/types.js';
 
 const storage = new FSStorageProvider();
 
@@ -1099,6 +1100,11 @@ export class OrphanBranchBackend implements StateBackend {
 export class StateBackendStorageAdapter implements StorageProvider {
   constructor(private backend: StateBackend, private squadDir: string) {}
 
+  async createLockStore(lockAnchor: string): Promise<BackendStateStore> {
+    const { createStateBackendStore } = await import('./backend/state-backend-store.js');
+    return createStateBackendStore(this.backend, { lockAnchor });
+  }
+
   // ── Async operations ─────────────────────────────────────────────────────
   async createIfAbsent(filePath: string, data: string): Promise<void> {
     this.backend.createIfAbsent(this.toRelative(filePath, { operation: 'createIfAbsent' }), data);
diff --git a/test/backend.test.ts b/test/backend.test.ts
index 9bdf500ad..e65dd2979 100644
--- a/test/backend.test.ts
+++ b/test/backend.test.ts
@@ -1730,7 +1730,7 @@ describe('PR #2253 Copilot review thread regressions', () => {
     const fs = await import('node:fs');
     const os = await import('node:os');
     const path = await import('node:path');
-    const { OrphanBranchBackend, TwoLayerBackend } = await import('../packages/squad-sdk/src/state-backend.js');
+    const { OrphanBranchBackend, TwoLayerBackend, StateBackendStorageAdapter } = await import('../packages/squad-sdk/src/state-backend.js');
     const base = fs.mkdtempSync(path.join(os.tmpdir(), 'sq-wt-lock-'));
     try {
       const repoMain = path.join(base, 'main-repo');
@@ -1749,6 +1749,10 @@ describe('PR #2253 Copilot review thread regressions', () => {
       const storeWt = createStateBackendStore(new OrphanBranchBackend(repoWt), opts);
       const storeTwoLayerWt = createStateBackendStore(new TwoLayerBackend(repoWt), { ...opts, lockAnchor: path.join(repoWt, '.squad') });
       const storeAlias = createStateBackendStore(new OrphanBranchBackend(repoAlias), opts);
+      const adapterStoreWt = new StateBackendStorageAdapter(
+        new OrphanBranchBackend(repoWt), path.join(repoWt, '.squad'),
+      );
+      const adapterLockStoreWt = await adapterStoreWt.createLockStore(path.join(repoWt, '.squad'));
 
       const release = storeMain.lock!('backend/locks/shared-conv');
       try {
@@ -1756,6 +1760,7 @@ describe('PR #2253 Copilot review thread regressions', () => {
         expect(() => storeWt.lock!('backend/locks/shared-conv')).toThrow(/Timed out/);
         expect(() => storeTwoLayerWt.lock!('backend/locks/shared-conv')).toThrow(/Timed out/);
         expect(() => storeAlias.lock!('backend/locks/shared-conv')).toThrow(/Timed out/);
+        expect(() => adapterLockStoreWt.lock!('backend/locks/shared-conv')).toThrow(/Timed out/);
 
         // A different orphan branch ref has its own independent lock
         const storeOtherBranch = createStateBackendStore(new OrphanBranchBackend(repoWt, 'other-state'), opts);
diff --git a/test/state-backend.test.ts b/test/state-backend.test.ts
index 6f08078c7..94c9347e9 100644
--- a/test/state-backend.test.ts
+++ b/test/state-backend.test.ts
@@ -8,6 +8,7 @@ import { WorktreeBackend, GitNotesBackend, OrphanBranchBackend, TwoLayerBackend,
 import type { StateBackend, StateBackendType } from '../packages/squad-sdk/src/state-backend.js';
 import { resolveSquadState, clearResolveSquadCache } from '../packages/squad-sdk/src/resolution.js';
 import { ToolRegistry } from '../packages/squad-sdk/src/tools/index.js';
+import { LocalMemoryStore } from '../packages/squad-sdk/src/memory/index.js';
 
 const TMP = join(process.cwd(), `.test-state-backend-${randomBytes(4).toString('hex')}`);
 function git(args: string, cwd = TMP): string {
@@ -787,6 +788,25 @@ describe('ToolRegistry state tools with git-native backend', () => {
     expect(git('status --porcelain')).toBe('');
   });
 
+  it('uses the backend-aware lock store for memory index writes', { timeout: 30_000 }, async () => {
+    const backend = new OrphanBranchBackend(TMP);
+    const adapter = new StateBackendStorageAdapter(backend, squadDir());
+    const createLockStore = vi.spyOn(adapter, 'createLockStore');
+    const memory = new LocalMemoryStore(adapter, squadDir(), { rootKind: 'squad' });
+
+    const result = await memory.write({
+      content: 'Memory index locks must follow the configured state backend.',
+      title: 'Backend-aware memory lock',
+      requestedClass: 'LOCAL',
+    });
+
+    expect(result.stored).toBe(true);
+    expect(createLockStore).toHaveBeenCalledWith(squadDir());
+    expect(backend.read('memory/index.json')).toContain('Backend-aware memory lock');
+    expect(existsSync(join(squadDir(), 'backend', 'locks'))).toBe(false);
+    expect(git('status --porcelain')).toBe('');
+  });
+
   it('routes existing squad_decide writes through configured backend storage', { timeout: 20_000 }, async () => {
     const backend = new OrphanBranchBackend(TMP);
     const adapter = new StateBackendStorageAdapter(backend, squadDir());