fix(cli): map rewind turns after compression

packages/cli/src/acp-integration/acpAgent.test.ts

@@ -844,9 +844,10 @@ describe('QwenAgent MCP SSE/HTTP support', () => {
         sendAvailableCommandsUpdate: vi.fn().mockResolvedValue(undefined),
         replayHistory: vi.fn().mockResolvedValue(undefined),
         installRewriter: vi.fn(),
-        captureHistorySnapshot: vi
-          .fn()
-          .mockReturnValue([{ role: 'user', parts: [{ text: 'before' }] }]),
+        captureHistorySnapshot: vi.fn().mockReturnValue({
+          history: [{ role: 'user', parts: [{ text: 'before' }] }],
+          modelFacingUserTurnCount: 1,
+        }),
         restoreHistory: vi.fn(),
         rewindToTurn: vi
           .fn()
@@ -1719,7 +1720,10 @@ describe('QwenAgent MCP SSE/HTTP support', () => {
     expect(lastSessionMock?.rewindToTurn).toHaveBeenCalledWith(1);
     expect(response).toEqual({
       success: true,
-      historyBeforeRewind: [{ role: 'user', parts: [{ text: 'before' }] }],
+      historyBeforeRewind: {
+        history: [{ role: 'user', parts: [{ text: 'before' }] }],
+        modelFacingUserTurnCount: 1,
+      },
       targetTurnIndex: 1,
       apiTruncateIndex: 2,
     });
@@ -1843,6 +1847,85 @@ describe('QwenAgent MCP SSE/HTTP support', () => {
     await agentPromise;
   });
 
+  it('restoreSessionHistory extension method restores history snapshots', async () => {
+    const sessionId = '11111111-1111-1111-1111-111111111111';
+    await setupSessionMocks(sessionId);
+
+    const agentPromise = runAcpAgent(
+      mockConfig,
+      makeSessionSettings(),
+      mockArgv,
+    );
+    await vi.waitFor(() => expect(capturedAgentFactory).toBeDefined());
+
+    const agent = capturedAgentFactory!({
+      get closed() {
+        return mockConnectionState.promise;
+      },
+    }) as AgentLike;
+
+    await agent.newSession({ cwd: '/tmp', mcpServers: [] });
+    const snapshot = {
+      history: [{ role: 'user', parts: [{ text: 'restored' }] }],
+      modelFacingUserTurnCount: 1,
+    };
+    const response = await agent.extMethod('restoreSessionHistory', {
+      sessionId,
+      history: snapshot,
+      cwd: '/tmp',
+    });
+
+    expect(lastSessionMock?.restoreHistory).toHaveBeenCalledWith(snapshot);
+    expect(response).toEqual({ success: true });
+
+    mockConnectionState.resolve();
+    await agentPromise;
+  });
+
+  it('restoreSessionHistory rejects invalid history snapshot turn counts', async () => {
+    const sessionId = '11111111-1111-1111-1111-111111111111';
+    await setupSessionMocks(sessionId);
+
+    const agentPromise = runAcpAgent(
+      mockConfig,
+      makeSessionSettings(),
+      mockArgv,
+    );
+    await vi.waitFor(() => expect(capturedAgentFactory).toBeDefined());
+
+    const agent = capturedAgentFactory!({
+      get closed() {
+        return mockConnectionState.promise;
+      },
+    }) as AgentLike;
+
+    await agent.newSession({ cwd: '/tmp', mcpServers: [] });
+
+    for (const modelFacingUserTurnCount of [
+      NaN,
+      Infinity,
+      -Infinity,
+      -1,
+      1.5,
+      Number.MAX_SAFE_INTEGER + 1,
+    ]) {
+      await expect(
+        agent.extMethod('restoreSessionHistory', {
+          sessionId,
+          history: {
+            history: [],
+            modelFacingUserTurnCount,
+          },
+        }),
+      ).rejects.toThrow('Invalid or missing history');
+    }
+
+    expect(lastSessionMock?.restoreHistory).not.toHaveBeenCalled();
+
+    mockConnectionState.resolve();
+    await agentPromise;
+  });
+
   it('restoreSessionHistory rejects invalid session ids', async () => {
     await setupSessionMocks('11111111-1111-1111-1111-111111111111');
 

packages/cli/src/acp-integration/acpAgent.ts

@@ -74,7 +74,11 @@ import type { ApprovalModeValue } from './session/types.js';
 import { z } from 'zod';
 import type { CliArgs } from '../config/config.js';
 import { loadCliConfig } from '../config/config.js';
-import { Session, buildAvailableCommandsSnapshot } from './session/Session.js';
+import {
+  Session,
+  buildAvailableCommandsSnapshot,
+  type HistorySnapshot,
+} from './session/Session.js';
 import {
   formatAcpModelId,
   parseAcpBaseModelId,
@@ -1541,7 +1545,24 @@ class QwenAgent implements Agent {
             'Invalid or missing sessionId',
           );
         }
-        if (!Array.isArray(history)) {
+        const isHistorySnapshot =
+          !!history &&
+          typeof history === 'object' &&
+          !Array.isArray(history) &&
+          Array.isArray((history as { history?: unknown }).history) &&
+          Number.isInteger(
+            (history as { modelFacingUserTurnCount?: unknown })
+              .modelFacingUserTurnCount,
+          ) &&
+          Number.isFinite(
+            (history as { modelFacingUserTurnCount?: unknown })
+              .modelFacingUserTurnCount as number,
+          ) &&
+          ((history as { modelFacingUserTurnCount?: unknown })
+            .modelFacingUserTurnCount as number) >= 0 &&
+          ((history as { modelFacingUserTurnCount?: unknown })
+            .modelFacingUserTurnCount as number) <= Number.MAX_SAFE_INTEGER;
+        if (!Array.isArray(history) && !isHistorySnapshot) {
           throw RequestError.invalidParams(
             undefined,
             'Invalid or missing history',
@@ -1555,7 +1576,7 @@ class QwenAgent implements Agent {
           );
         }
 
-        session.restoreHistory(history as Content[]);
+        session.restoreHistory(history as Content[] | HistorySnapshot);
         return { success: true };
       }
       case 'getAccountInfo': {