diff --git a/packages/daemon/src/lib/acp/acp-command.ts b/packages/daemon/src/lib/acp/acp-command.ts
index 599c844027..ea1d8c4e12 100644
--- a/packages/daemon/src/lib/acp/acp-command.ts
+++ b/packages/daemon/src/lib/acp/acp-command.ts
@@ -3,7 +3,6 @@ import { getAcpCommandIdentity } from '@hyperneo/shared/acp';
 
 export { getAcpCommandIdentity, parseAcpCommand } from '@hyperneo/shared/acp';
 
-/* @public - consumed by ACP provider sync in a later stack PR */
 export function getAcpCommandIdentityDigest(commandLine: string): string {
   return createHash('sha256').update(getAcpCommandIdentity(commandLine)).digest('hex');
 }
diff --git a/packages/daemon/src/lib/acp/acp-query-runner.ts b/packages/daemon/src/lib/acp/acp-query-runner.ts
index 2671b6719a..4e87942905 100644
--- a/packages/daemon/src/lib/acp/acp-query-runner.ts
+++ b/packages/daemon/src/lib/acp/acp-query-runner.ts
@@ -34,7 +34,7 @@ import {
   resolveSpaceMcpSessionPolicy,
 } from '../space/runtime/space-mcp-session-policy';
 import { AcpClient, type AcpClientOptions } from './acp-client';
-import { parseAcpCommand } from './acp-command';
+import { getAcpCommandIdentityDigest, parseAcpCommand } from './acp-command';
 import { AcpQueryAdapter } from './acp-query-adapter';
 import { AcpMcpProxyBridge, shouldProxy } from './mcp-proxy-bridge';
 
@@ -352,6 +352,8 @@ function acpInstructionBlocks(queryOptions: Options): AcpContentBlock[] {
 type AcpClientFactory = (options: AcpClientOptions) => AcpClient;
 
 export class AcpQueryRunner {
+  private pendingAcpIdentityMetadata = false;
+
   private _lastConsumedUserMessage: {
     uuid: string;
     content: string | MessageContent[];
@@ -456,6 +458,23 @@ export class AcpQueryRunner {
         throw new Error('Set HYPERNEO_ACP_COMMAND to enable ACP agents.');
       }
       const { command, args } = parseAcpCommand(acpCommand);
+      const commandIdentity = getAcpCommandIdentityDigest(acpCommand);
+      const storedIdentity = session.metadata?.acpCommandIdentity;
+      if (storedIdentity !== commandIdentity) {
+        if (session.acpSessionId && storedIdentity !== undefined) {
+          session.acpSessionId = undefined;
+          session.metadata = {
+            ...session.metadata,
+            acpInstructionsSent: undefined,
+            acpContextUsageEstimate: undefined,
+          };
+        }
+        session.metadata = {
+          ...session.metadata,
+          acpCommandIdentity: commandIdentity,
+        };
+        this.pendingAcpIdentityMetadata = true;
+      }
       const preCleanupAuth = {
         ANTHROPIC_AUTH_TOKEN: process.env.ANTHROPIC_AUTH_TOKEN,
         CLAUDE_CODE_OAUTH_TOKEN: process.env.CLAUDE_CODE_OAUTH_TOKEN,
@@ -1045,8 +1064,13 @@ export class AcpQueryRunner {
 
   private persistAcpSessionId(acpSessionId: string | undefined): void {
     const { session, db } = this.ctx;
-    if (session.acpSessionId === acpSessionId) return;
+    if (session.acpSessionId === acpSessionId && !this.pendingAcpIdentityMetadata) return;
     session.acpSessionId = acpSessionId;
+    if (this.pendingAcpIdentityMetadata) {
+      this.pendingAcpIdentityMetadata = false;
+      db.updateSession(session.id, { acpSessionId, metadata: session.metadata });
+      return;
+    }
     db.updateSession(session.id, { acpSessionId });
   }
 
diff --git a/packages/daemon/tests/unit/lib/acp/acp-query-runner.test.ts b/packages/daemon/tests/unit/lib/acp/acp-query-runner.test.ts
index cf3587dee6..be17bf1337 100644
--- a/packages/daemon/tests/unit/lib/acp/acp-query-runner.test.ts
+++ b/packages/daemon/tests/unit/lib/acp/acp-query-runner.test.ts
@@ -11,6 +11,7 @@ import type { QueryOptionsBuilder } from '../../../../src/lib/agent/query-option
 import type { AskUserQuestionHandler } from '../../../../src/lib/agent/ask-user-question-handler';
 import type { QueryRunnerContext } from '../../../../src/lib/agent/query-runner';
 import type { AcpClient, AcpClientOptions } from '../../../../src/lib/acp/acp-client';
+import { getAcpCommandIdentityDigest } from '../../../../src/lib/acp/acp-command';
 import {
   AcpQueryRunner,
   convertMcpServersForAcp,
@@ -841,7 +842,128 @@ describe('AcpQueryRunner', () => {
     expect(ctx.session.acpSessionId).toBe('acp-session-1');
     expect(ctx.db.updateSession).toHaveBeenCalledWith('session-1', {
       acpSessionId: 'acp-session-1',
+      metadata: expect.objectContaining({
+        acpCommandIdentity: getAcpCommandIdentityDigest('mock-acp --stdio'),
+      }),
+    });
+  });
+
+  test('creates a new ACP session when the persisted command identity changes', async () => {
+    const client = createMockClient();
+    client.canLoadSession.mockImplementation(() => true);
+    const { runner, ctx } = createRunnerFixture({
+      client,
+      session: {
+        acpSessionId: 'persisted-acp-session',
+        metadata: {
+          acpCommandIdentity: getAcpCommandIdentityDigest('other-acp --stdio'),
+          acpInstructionsSent: true,
+          acpContextUsageEstimate: 12000,
+        },
+      } as Partial<Session>,
+      queryOptions: {
+        cwd: '/tmp/acp-session',
+        mcpServers: {},
+        systemPrompt: { type: 'preset', preset: 'none', append: 'Follow current rules.' },
+      },
+    });
+
+    await runner.start();
+    await ctx.queryPromise;
+
+    expect(client.loadSession).not.toHaveBeenCalled();
+    expect(client.resumeSession).not.toHaveBeenCalled();
+    expect(client.createSession).toHaveBeenCalledWith('/tmp/acp-session', []);
+    expect(ctx.db.updateSession).toHaveBeenCalledWith('session-1', {
+      acpSessionId: 'acp-session-1',
+      metadata: expect.objectContaining({
+        acpCommandIdentity: getAcpCommandIdentityDigest('mock-acp --stdio'),
+        acpContextUsageEstimate: undefined,
+      }),
     });
+    for (const call of ctx.db.updateSession.mock.calls) {
+      expect(call[1]).not.toMatchObject({ acpSessionId: undefined });
+    }
+    expect(ctx.session.metadata.acpInstructionsSent).toBe(true);
+    expect(client.sendPrompt.mock.calls[0][0]).toEqual([
+      {
+        type: 'text',
+        text: 'HyperNeo session instructions:\n\nFollow current rules.',
+      },
+      { type: 'text', text: 'hello' },
+    ]);
+  });
+
+  test('preserves an existing session whose command identity matches', async () => {
+    const client = createMockClient();
+    client.canLoadSession.mockImplementation(() => true);
+    client.loadSession.mockImplementation(async (sessionId: string) => ({
+      sessionId,
+      configOptions: [],
+    }));
+    const { runner, ctx } = createRunnerFixture({
+      client,
+      session: {
+        acpSessionId: 'persisted-acp-session',
+        metadata: {
+          messageCount: 2,
+          acpCommandIdentity: getAcpCommandIdentityDigest('mock-acp --stdio'),
+        },
+      } as Partial<Session>,
+    });
+
+    await runner.start();
+    await ctx.queryPromise;
+
+    expect(client.loadSession).toHaveBeenCalledWith(
+      'persisted-acp-session',
+      '/tmp/acp-session',
+      []
+    );
+    expect(client.createSession).not.toHaveBeenCalled();
+    expect(ctx.session.metadata.acpCommandIdentity).toBe(
+      getAcpCommandIdentityDigest('mock-acp --stdio')
+    );
+  });
+
+  test('keeps the old ACP session id when the replacement command fails to start', async () => {
+    const client = createMockClient();
+    client.initialize.mockImplementation(async () => {
+      throw new Error('replacement agent unavailable');
+    });
+    const { runner, ctx } = createRunnerFixture({
+      client,
+      session: {
+        acpSessionId: 'persisted-acp-session',
+        metadata: {
+          acpCommandIdentity: getAcpCommandIdentityDigest('other-acp --stdio'),
+        },
+      } as Partial<Session>,
+    });
+
+    await runner.start();
+    await ctx.queryPromise;
+
+    for (const call of ctx.db.updateSession.mock.calls) {
+      expect(call[1]).not.toMatchObject({ acpSessionId: undefined });
+      expect(call[1]).not.toHaveProperty('metadata');
+    }
+    expect(ctx.session.acpSessionId).toBe(undefined);
+    expect(ctx.session.metadata.acpCommandIdentity).toBe(
+      getAcpCommandIdentityDigest('mock-acp --stdio')
+    );
+  });
+
+  test('persists only a digest of the ACP command identity', async () => {
+    process.env.HYPERNEO_ACP_COMMAND = 'devin acp --token topsecret';
+    const { runner, ctx } = createRunnerFixture();
+
+    await runner.start();
+    await ctx.queryPromise;
+
+    const identity = ctx.session.metadata.acpCommandIdentity as string;
+    expect(identity).toBe(getAcpCommandIdentityDigest('devin acp --token topsecret'));
+    expect(identity).not.toContain('topsecret');
   });
 
   test('loads an existing ACP session instead of creating a new one', async () => {
@@ -912,6 +1034,9 @@ describe('AcpQueryRunner', () => {
     expect(ctx.session.acpSessionId).toBe('resumed-acp-session');
     expect(ctx.db.updateSession).toHaveBeenCalledWith('session-1', {
       acpSessionId: 'resumed-acp-session',
+      metadata: expect.objectContaining({
+        acpCommandIdentity: getAcpCommandIdentityDigest('mock-acp --stdio'),
+      }),
     });
   });
 
diff --git a/packages/shared/src/types.ts b/packages/shared/src/types.ts
index 92514f4704..d6b6e8e068 100644
--- a/packages/shared/src/types.ts
+++ b/packages/shared/src/types.ts
@@ -317,6 +317,7 @@ export interface SessionMetadata {
   costBaseline?: number;
   refusalRewindTargetUuid?: string | null;
   acpInstructionsSent?: boolean;
+  acpCommandIdentity?: string;
   pastSdkSessionIds?: string[];
   acpContextUsageEstimate?: number;
   worktreeChoice?: {