diff --git a/design/qwen-code-electron-desktop-implementation-plan.md b/design/qwen-code-electron-desktop-implementation-plan.md
index 4a3c1b0f3..c28a9d44c 100644
--- a/design/qwen-code-electron-desktop-implementation-plan.md
+++ b/design/qwen-code-electron-desktop-implementation-plan.md
@@ -72,7 +72,7 @@ order, verification, decisions, and remaining work.
 
 ### Slice 3: ACP Process Client Wrapper
 
-- Status: pending
+- Status: complete
 - Goal: implement a desktop-local ACP child-process client around
   `qwen --acp --channel=Desktop`.
 - Files:
@@ -213,6 +213,18 @@ order, verification, decisions, and remaining work.
   - `npm run typecheck` passed across workspaces.
   - `npm run build` passed across the configured build order. Existing VS Code
     companion lint warnings were reported by its build script, with no errors.
+- 2026-04-25 Slice 3:
+  - `npm install --ignore-scripts --workspace=@qwen-code/desktop` passed.
+  - `npx prettier --check design/qwen-code-electron-desktop-implementation-plan.md scripts/build.js packages/desktop` passed.
+  - `npm run test --workspace=packages/desktop` passed: 2 files, 12 tests.
+  - `npm run lint --workspace=packages/desktop` passed.
+  - `npm run typecheck --workspace=packages/desktop` passed.
+  - `npm run build --workspace=packages/desktop` passed.
+  - `npm exec --workspace=packages/desktop -- electron --version` passed:
+    `v41.3.0`.
+  - `npm run typecheck` passed across workspaces.
+  - `npm run build` passed across the configured build order. Existing VS Code
+    companion lint warnings were reported by its build script, with no errors.
 
 ## Self Review Notes
 
@@ -234,10 +246,17 @@ order, verification, decisions, and remaining work.
     placeholders until ACP is connected.
   - Renderer displays runtime summary from REST only and still obtains the
     server token only through preload.
+- 2026-04-25 Slice 3:
+  - `AcpProcessClient` follows the existing Qwen ACP boundary:
+    `ClientSideConnection`, `ndJsonStream`, and `qwen --acp`.
+  - The wrapper defaults permission requests to cancellation until the
+    permission bridge slice supplies a UI-backed resolver.
+  - Startup failures race initialize against child exit; later process exits
+    clear connection state without leaving a rejected startup promise.
 
 ## Remaining Work
 
-- Commit Slice 2.
-- Continue with Slice 3 ACP process client wrapper.
+- Commit Slice 3.
+- Continue with Slice 4 session REST API.
 - Continue through the ACP, session, WebSocket, permission, settings, and
   packaging slices until the architecture MVP is fully verified.
diff --git a/package-lock.json b/package-lock.json
index b29b93aee..27bcde59a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -18786,6 +18786,7 @@
       "name": "@qwen-code/desktop",
       "version": "0.15.2",
       "dependencies": {
+        "@agentclientprotocol/sdk": "^0.14.1",
         "@qwen-code/webui": "file:../webui",
         "react": "^19.1.0",
         "react-dom": "^19.1.0"
diff --git a/packages/desktop/package.json b/packages/desktop/package.json
index 72cbb81ba..3e6b6d045 100644
--- a/packages/desktop/package.json
+++ b/packages/desktop/package.json
@@ -17,6 +17,7 @@
     "typecheck": "tsc --noEmit --project tsconfig.main.json && tsc --noEmit --project tsconfig.renderer.json"
   },
   "dependencies": {
+    "@agentclientprotocol/sdk": "^0.14.1",
     "@qwen-code/webui": "file:../webui",
     "react": "^19.1.0",
     "react-dom": "^19.1.0"
diff --git a/packages/desktop/src/server/acp/AcpProcessClient.test.ts b/packages/desktop/src/server/acp/AcpProcessClient.test.ts
new file mode 100644
index 000000000..ec0b5d62a
--- /dev/null
+++ b/packages/desktop/src/server/acp/AcpProcessClient.test.ts
@@ -0,0 +1,265 @@
+/**
+ * @license
+ * Copyright 2026 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { EventEmitter } from 'node:events';
+import type { ChildProcess, SpawnOptions } from 'node:child_process';
+import { PassThrough } from 'node:stream';
+import { describe, expect, it, vi } from 'vitest';
+import { PROTOCOL_VERSION } from '@agentclientprotocol/sdk';
+import type {
+  Agent,
+  Client,
+  ClientSideConnection,
+  InitializeResponse,
+  RequestPermissionRequest,
+  SessionNotification,
+} from '@agentclientprotocol/sdk';
+import {
+  AcpProcessClient,
+  type AcpProcessClientOptions,
+} from './AcpProcessClient.js';
+
+type AcpSdkConnection = Pick<
+  ClientSideConnection,
+  | 'authenticate'
+  | 'cancel'
+  | 'extMethod'
+  | 'initialize'
+  | 'loadSession'
+  | 'newSession'
+  | 'prompt'
+  | 'setSessionMode'
+  | 'unstable_listSessions'
+  | 'unstable_setSessionModel'
+>;
+
+interface Harness {
+  client: AcpProcessClient;
+  child: ChildProcess;
+  connection: AcpSdkConnection;
+  capturedClients: Client[];
+  spawnProcess: ReturnType<typeof vi.fn>;
+}
+
+describe('AcpProcessClient', () => {
+  it('spawns qwen ACP with the Desktop channel and initializes SDK', async () => {
+    const harness = createHarness({
+      cwd: '/workspace',
+      extraArgs: ['--model', 'qwen-plus'],
+      env: { QWEN_TEST_FLAG: '1' },
+    });
+
+    await harness.client.connect();
+
+    expect(harness.spawnProcess).toHaveBeenCalledWith(
+      process.execPath,
+      ['/tmp/qwen.js', '--acp', '--channel=Desktop', '--model', 'qwen-plus'],
+      expect.objectContaining({
+        cwd: '/workspace',
+        shell: false,
+        stdio: ['pipe', 'pipe', 'pipe'],
+      }),
+    );
+    expect(harness.connection.initialize).toHaveBeenCalledWith({
+      protocolVersion: PROTOCOL_VERSION,
+      clientCapabilities: {},
+    });
+  });
+
+  it('forwards ACP client callbacks to desktop handlers', async () => {
+    const harness = createHarness();
+    const onSessionUpdate = vi.fn();
+    const onPermissionRequest = vi
+      .fn()
+      .mockResolvedValue({ outcome: { outcome: 'cancelled' } });
+    const onExtNotification = vi.fn();
+    harness.client.onSessionUpdate = onSessionUpdate;
+    harness.client.onPermissionRequest = onPermissionRequest;
+    harness.client.onExtNotification = onExtNotification;
+
+    await harness.client.connect();
+    const acpClient = harness.capturedClients[0];
+    const sessionUpdate = {
+      sessionId: 'session-1',
+      update: { sessionUpdate: 'agent_message_chunk' },
+    } as unknown as SessionNotification;
+    const permissionRequest = {
+      sessionId: 'session-1',
+      options: [],
+    } as unknown as RequestPermissionRequest;
+
+    await acpClient.sessionUpdate(sessionUpdate);
+    await acpClient.requestPermission(permissionRequest);
+    await acpClient.extNotification('authenticate/update', { ok: true });
+
+    expect(onSessionUpdate).toHaveBeenCalledWith(sessionUpdate);
+    expect(onPermissionRequest).toHaveBeenCalledWith(permissionRequest);
+    expect(onExtNotification).toHaveBeenCalledWith('authenticate/update', {
+      ok: true,
+    });
+  });
+
+  it('wraps session and prompt ACP methods', async () => {
+    const harness = createHarness();
+    await harness.client.connect();
+
+    await harness.client.newSession('/workspace');
+    await harness.client.loadSession('session-1', '/workspace');
+    await harness.client.listSessions({
+      cwd: '/workspace',
+      cursor: 4,
+      size: 20,
+    });
+    await harness.client.prompt('session-1', 'hello');
+    await harness.client.cancel('session-1');
+    await harness.client.setMode('session-1', 'yolo');
+    await harness.client.setModel('session-1', 'qwen-plus');
+
+    expect(harness.connection.newSession).toHaveBeenCalledWith({
+      cwd: '/workspace',
+      mcpServers: [],
+    });
+    expect(harness.connection.loadSession).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+      cwd: '/workspace',
+      mcpServers: [],
+    });
+    expect(harness.connection.unstable_listSessions).toHaveBeenCalledWith({
+      cwd: '/workspace',
+      cursor: '4',
+      _meta: { size: 20 },
+    });
+    expect(harness.connection.prompt).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+      prompt: [{ type: 'text', text: 'hello' }],
+    });
+    expect(harness.connection.cancel).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+    });
+    expect(harness.connection.setSessionMode).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+      modeId: 'yolo',
+    });
+    expect(harness.connection.unstable_setSessionModel).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+      modelId: 'qwen-plus',
+    });
+  });
+
+  it('clears connection state and kills the process on disconnect', async () => {
+    const harness = createHarness();
+    await harness.client.connect();
+
+    harness.client.disconnect();
+
+    expect(harness.child.kill).toHaveBeenCalledOnce();
+    expect(harness.client.isConnected).toBe(false);
+  });
+
+  it('reports child process exits through onDisconnected', async () => {
+    const harness = createHarness();
+    const onDisconnected = vi.fn();
+    harness.client.onDisconnected = onDisconnected;
+    await harness.client.connect();
+
+    harness.child.emit('exit', 143, 'SIGTERM');
+
+    expect(onDisconnected).toHaveBeenCalledWith(143, 'SIGTERM');
+    expect(harness.client.isConnected).toBe(false);
+  });
+
+  it('rejects connect when the ACP process exits before initialize completes', async () => {
+    const harness = createHarness();
+    vi.mocked(harness.connection.initialize).mockReturnValue(
+      new Promise<InitializeResponse>(() => {}),
+    );
+
+    const connectPromise = harness.client.connect();
+    harness.child.stderr?.emit('data', Buffer.from('startup failed'));
+    harness.child.emit('exit', 1, null);
+
+    await expect(connectPromise).rejects.toThrow(
+      'Qwen ACP process exited unexpectedly',
+    );
+  });
+});
+
+function createHarness(
+  options: Partial<AcpProcessClientOptions> = {},
+): Harness {
+  const child = createFakeChild();
+  const connection = createFakeConnection();
+  const capturedClients: Client[] = [];
+  const spawnProcess = vi.fn(
+    (_command: string, _args: string[], _options: SpawnOptions) => child,
+  );
+  const createConnection: AcpProcessClientOptions['createConnection'] = (
+    clientFactory: (agent: Agent) => Client,
+  ) => {
+    capturedClients.push(clientFactory({} as Agent));
+    return connection;
+  };
+
+  return {
+    child,
+    connection,
+    capturedClients,
+    spawnProcess,
+    client: new AcpProcessClient({
+      cliEntryPath: '/tmp/qwen.js',
+      startupDelayMs: 0,
+      validateCliPath: false,
+      spawnProcess,
+      createConnection,
+      ...options,
+    }),
+  };
+}
+
+function createFakeConnection(): AcpSdkConnection {
+  return {
+    authenticate: vi.fn().mockResolvedValue({}),
+    cancel: vi.fn().mockResolvedValue(undefined),
+    extMethod: vi.fn().mockResolvedValue({ success: true }),
+    initialize: vi.fn().mockResolvedValue({
+      protocolVersion: PROTOCOL_VERSION,
+      agentInfo: {
+        name: 'qwen-code',
+        title: 'Qwen Code',
+        version: 'test',
+      },
+      agentCapabilities: {},
+      authMethods: [],
+    } satisfies InitializeResponse),
+    loadSession: vi.fn().mockResolvedValue({ sessionId: 'session-1' }),
+    newSession: vi.fn().mockResolvedValue({ sessionId: 'session-1' }),
+    prompt: vi.fn().mockResolvedValue({ stopReason: 'end_turn' }),
+    setSessionMode: vi.fn().mockResolvedValue({}),
+    unstable_listSessions: vi.fn().mockResolvedValue({ sessions: [] }),
+    unstable_setSessionModel: vi.fn().mockResolvedValue({}),
+  } as unknown as AcpSdkConnection;
+}
+
+function createFakeChild(): ChildProcess {
+  const child = new EventEmitter() as ChildProcess;
+  const stdin = new PassThrough();
+  const stdout = new PassThrough();
+  const stderr = new PassThrough();
+
+  Object.assign(child, {
+    stdin,
+    stdout,
+    stderr,
+    killed: false,
+    exitCode: null,
+    kill: vi.fn(() => {
+      Object.assign(child, { killed: true, exitCode: 0 });
+      return true;
+    }),
+  });
+
+  return child;
+}
diff --git a/packages/desktop/src/server/acp/AcpProcessClient.ts b/packages/desktop/src/server/acp/AcpProcessClient.ts
new file mode 100644
index 000000000..b101f2bed
--- /dev/null
+++ b/packages/desktop/src/server/acp/AcpProcessClient.ts
@@ -0,0 +1,356 @@
+/**
+ * @license
+ * Copyright 2026 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { spawn } from 'node:child_process';
+import type { ChildProcess, SpawnOptions } from 'node:child_process';
+import { existsSync } from 'node:fs';
+import { Readable, Writable } from 'node:stream';
+import {
+  ClientSideConnection,
+  ndJsonStream,
+  PROTOCOL_VERSION,
+} from '@agentclientprotocol/sdk';
+import type {
+  Agent,
+  AuthenticateResponse,
+  Client,
+  ClientCapabilities,
+  ContentBlock,
+  InitializeResponse,
+  ListSessionsResponse,
+  LoadSessionResponse,
+  NewSessionResponse,
+  PromptResponse,
+  RequestPermissionRequest,
+  RequestPermissionResponse,
+  SessionNotification,
+  SetSessionModeResponse,
+  SetSessionModelResponse,
+} from '@agentclientprotocol/sdk';
+
+type AcpSdkConnection = Pick<
+  ClientSideConnection,
+  | 'authenticate'
+  | 'cancel'
+  | 'extMethod'
+  | 'initialize'
+  | 'loadSession'
+  | 'newSession'
+  | 'prompt'
+  | 'setSessionMode'
+  | 'unstable_listSessions'
+  | 'unstable_setSessionModel'
+>;
+
+type CreateAcpConnection = (
+  clientFactory: (agent: Agent) => Client,
+  stdin: WritableStream,
+  stdout: ReadableStream<Uint8Array>,
+) => AcpSdkConnection;
+
+type SpawnProcess = (
+  command: string,
+  args: string[],
+  options: SpawnOptions,
+) => ChildProcess;
+
+export interface AcpProcessClientOptions {
+  cliEntryPath: string;
+  cwd?: string;
+  command?: string;
+  channel?: 'Desktop';
+  extraArgs?: string[];
+  env?: NodeJS.ProcessEnv;
+  startupDelayMs?: number;
+  validateCliPath?: boolean;
+  spawnProcess?: SpawnProcess;
+  createConnection?: CreateAcpConnection;
+}
+
+export interface ListSessionsOptions {
+  cwd?: string;
+  cursor?: number;
+  size?: number;
+}
+
+export class AcpProcessClient {
+  private child: ChildProcess | null = null;
+  private connection: AcpSdkConnection | null = null;
+  private readonly options: Required<
+    Pick<
+      AcpProcessClientOptions,
+      'channel' | 'startupDelayMs' | 'validateCliPath'
+    >
+  > &
+    Omit<
+      AcpProcessClientOptions,
+      'channel' | 'startupDelayMs' | 'validateCliPath'
+    >;
+
+  onSessionUpdate: (notification: SessionNotification) => void = () => {};
+  onPermissionRequest: (
+    request: RequestPermissionRequest,
+  ) => Promise<RequestPermissionResponse> = async () => ({
+    outcome: { outcome: 'cancelled' },
+  });
+  onExtNotification: (
+    method: string,
+    params: Record<string, unknown>,
+  ) => Promise<void> = async () => {};
+  onDisconnected: (code: number | null, signal: string | null) => void =
+    () => {};
+  onInitialized: (response: InitializeResponse) => void = () => {};
+
+  constructor(options: AcpProcessClientOptions) {
+    this.options = {
+      ...options,
+      channel: options.channel ?? 'Desktop',
+      startupDelayMs: options.startupDelayMs ?? 1000,
+      validateCliPath: options.validateCliPath ?? true,
+    };
+  }
+
+  get isConnected(): boolean {
+    return (
+      this.child !== null &&
+      !this.child.killed &&
+      this.child.exitCode === null &&
+      this.connection !== null
+    );
+  }
+
+  async connect(): Promise<InitializeResponse> {
+    if (this.child) {
+      this.disconnect();
+    }
+
+    if (
+      this.options.validateCliPath &&
+      !existsSync(this.options.cliEntryPath)
+    ) {
+      throw new Error(
+        `Qwen CLI ACP entry not found: ${this.options.cliEntryPath}`,
+      );
+    }
+
+    const child = this.spawnChild();
+    const stderrChunks: string[] = [];
+    let spawnError: Error | null = null;
+    let startupComplete = false;
+
+    const processExitPromise = new Promise<never>((_resolve, reject) => {
+      child.on('exit', (code: number | null, signal: string | null) => {
+        const stderrOutput = stderrChunks.join('').trim();
+        const stderrSuffix = stderrOutput
+          ? `\nCLI stderr: ${stderrOutput.slice(-500)}`
+          : '';
+
+        if (this.child === child) {
+          this.child = null;
+          this.connection = null;
+          this.onDisconnected(code, signal);
+        }
+
+        if (!startupComplete) {
+          reject(
+            new Error(
+              `Qwen ACP process exited unexpectedly (exit code: ${code}, signal: ${signal})${stderrSuffix}`,
+            ),
+          );
+        }
+      });
+    });
+
+    child.stderr?.on('data', (data: Buffer) => {
+      stderrChunks.push(data.toString());
+    });
+    child.on('error', (error: Error) => {
+      spawnError = error;
+    });
+
+    this.child = child;
+
+    if (this.options.startupDelayMs > 0) {
+      await delay(this.options.startupDelayMs);
+    }
+
+    if (spawnError) {
+      throw spawnError;
+    }
+    if (child.killed || child.exitCode !== null) {
+      throw new Error('Qwen ACP process failed to start.');
+    }
+
+    const connection = this.createSdkConnection(child);
+    this.connection = connection;
+
+    const initializeResponse = await Promise.race([
+      connection.initialize({
+        protocolVersion: PROTOCOL_VERSION,
+        clientCapabilities: this.getClientCapabilities(),
+      }),
+      processExitPromise,
+    ]).finally(() => {
+      startupComplete = true;
+    });
+
+    this.onInitialized(initializeResponse);
+    return initializeResponse;
+  }
+
+  disconnect(): void {
+    if (this.child) {
+      this.child.kill();
+    }
+
+    this.child = null;
+    this.connection = null;
+  }
+
+  async authenticate(methodId = 'default'): Promise<AuthenticateResponse> {
+    return this.ensureConnection().authenticate({ methodId });
+  }
+
+  async newSession(cwd: string): Promise<NewSessionResponse> {
+    return this.ensureConnection().newSession({ cwd, mcpServers: [] });
+  }
+
+  async loadSession(
+    sessionId: string,
+    cwd: string,
+  ): Promise<LoadSessionResponse> {
+    return this.ensureConnection().loadSession({
+      sessionId,
+      cwd,
+      mcpServers: [],
+    });
+  }
+
+  async listSessions(
+    options: ListSessionsOptions = {},
+  ): Promise<ListSessionsResponse> {
+    const params: Parameters<AcpSdkConnection['unstable_listSessions']>[0] = {
+      cwd: options.cwd ?? this.options.cwd ?? process.cwd(),
+    };
+
+    if (options.cursor !== undefined) {
+      params.cursor = String(options.cursor);
+    }
+    if (options.size !== undefined) {
+      params._meta = { ...(params._meta ?? {}), size: options.size };
+    }
+
+    return this.ensureConnection().unstable_listSessions(params);
+  }
+
+  async prompt(
+    sessionId: string,
+    prompt: string | ContentBlock[],
+  ): Promise<PromptResponse> {
+    const promptBlocks =
+      typeof prompt === 'string' ? [{ type: 'text', text: prompt }] : prompt;
+    return this.ensureConnection().prompt({
+      sessionId,
+      prompt: promptBlocks,
+    });
+  }
+
+  async cancel(sessionId: string): Promise<void> {
+    await this.ensureConnection().cancel({ sessionId });
+  }
+
+  async setMode(
+    sessionId: string,
+    modeId: string,
+  ): Promise<SetSessionModeResponse | void> {
+    return this.ensureConnection().setSessionMode({ sessionId, modeId });
+  }
+
+  async setModel(
+    sessionId: string,
+    modelId: string,
+  ): Promise<SetSessionModelResponse | void> {
+    return this.ensureConnection().unstable_setSessionModel({
+      sessionId,
+      modelId,
+    });
+  }
+
+  async extMethod<T extends Record<string, unknown>>(
+    method: string,
+    params: Record<string, unknown>,
+  ): Promise<T> {
+    return (await this.ensureConnection().extMethod(method, params)) as T;
+  }
+
+  private spawnChild(): ChildProcess {
+    const command = this.options.command ?? process.execPath;
+    const args = [
+      this.options.cliEntryPath,
+      '--acp',
+      `--channel=${this.options.channel}`,
+      ...(this.options.extraArgs ?? []),
+    ];
+    const env = { ...process.env, ...(this.options.env ?? {}) };
+
+    return (this.options.spawnProcess ?? spawn)(command, args, {
+      cwd: this.options.cwd ?? process.cwd(),
+      env,
+      shell: false,
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+  }
+
+  private createSdkConnection(child: ChildProcess): AcpSdkConnection {
+    const stdout = Readable.toWeb(child.stdout!) as ReadableStream<Uint8Array>;
+    const stdin = Writable.toWeb(child.stdin!) as WritableStream;
+    const createConnection =
+      this.options.createConnection ?? createSdkConnection;
+
+    return createConnection(
+      () => ({
+        sessionUpdate: (params: SessionNotification): Promise<void> => {
+          this.onSessionUpdate(params);
+          return Promise.resolve();
+        },
+        requestPermission: (
+          params: RequestPermissionRequest,
+        ): Promise<RequestPermissionResponse> =>
+          this.onPermissionRequest(params),
+        extNotification: (
+          method: string,
+          params: Record<string, unknown>,
+        ): Promise<void> => this.onExtNotification(method, params),
+      }),
+      stdin,
+      stdout,
+    );
+  }
+
+  private ensureConnection(): AcpSdkConnection {
+    if (!this.isConnected || !this.connection) {
+      throw new Error('Not connected to ACP agent');
+    }
+
+    return this.connection;
+  }
+
+  private getClientCapabilities(): ClientCapabilities {
+    return {};
+  }
+}
+
+function createSdkConnection(
+  clientFactory: (agent: Agent) => Client,
+  stdin: WritableStream,
+  stdout: ReadableStream<Uint8Array>,
+): AcpSdkConnection {
+  return new ClientSideConnection(clientFactory, ndJsonStream(stdin, stdout));
+}
+
+async function delay(ms: number): Promise<void> {
+  await new Promise((resolve) => setTimeout(resolve, ms));
+}