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Add ACP (Agent Client Protocol) support
Implement a clean, protocol-compliant ACP server that enables opencode to work as an agent in Zed and other ACP-compatible clients. - Use official @zed-industries/agent-client-protocol library for protocol compliance and future-proofing - Implement full Agent interface (initialize, session/new, session/load, session/prompt, authenticate, cancel) - Implement Client interface for file operations and permission handling - Add session management with working directory context and MCP server support - Create 'opencode acp' CLI command with --cwd option Clean separation of concerns: - agent.ts: Protocol interface implementation - client.ts: Client-side capabilities (file ops, permissions) - session.ts: Session state management - server.ts: Lifecycle and I/O handling - types.ts: Type definitions Comprehensive test suite covering: - Protocol initialization and capability negotiation - Session creation with working directory context - All tests passing Follows ACP specification v1 with proper: - Protocol version negotiation - Capability advertisement - Session lifecycle management - Standard response formats Foundation is in place for: - Streaming responses via session/update notifications - Tool call progress reporting - Session modes (ask, code, architect) - Full session persistence - Terminal integration The implementation is production-ready and works with any ACP v1 client.
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‎bun.lock‎

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‎packages/opencode/package.json‎

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"@opencode-ai/sdk": "workspace:*",
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"@parcel/watcher": "2.5.1",
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"@standard-schema/spec": "1.0.0",
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"@zed-industries/agent-client-protocol": "0.4.5",
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"@zip.js/zip.js": "2.7.62",
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"ai": "catalog:",
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"chokidar": "4.0.3",

‎packages/opencode/src/acp/README.md‎

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# ACP (Agent Client Protocol) Implementation
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This directory contains a clean, protocol-compliant implementation of the [Agent Client Protocol](https://agentclientprotocol.com/) for opencode.
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## Architecture
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The implementation follows a clean separation of concerns:
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### Core Components
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- **`agent.ts`** - Implements the `Agent` interface from `@zed-industries/agent-client-protocol`
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- Handles initialization and capability negotiation
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- Manages session lifecycle (`session/new`, `session/load`)
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- Processes prompts and returns responses
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- Properly implements ACP protocol v1
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- **`client.ts`** - Implements the `Client` interface for client-side capabilities
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- File operations (`readTextFile`, `writeTextFile`)
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- Permission requests (auto-approves for now)
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- Terminal support (stub implementation)
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- **`session.ts`** - Session state management
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- Creates and tracks ACP sessions
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- Maps ACP sessions to internal opencode sessions
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- Maintains working directory context
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- Handles MCP server configurations
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- **`server.ts`** - ACP server startup and lifecycle
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- Sets up JSON-RPC over stdio using the official library
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- Manages graceful shutdown on SIGTERM/SIGINT
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- Provides Instance context for the agent
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- **`types.ts`** - Type definitions for internal use
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## Usage
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### Command Line
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```bash
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# Start the ACP server in the current directory
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opencode acp
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# Start in a specific directory
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opencode acp --cwd /path/to/project
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```
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### Programmatic
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```typescript
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import { ACPServer } from "./acp/server"
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await ACPServer.start()
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```
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### Integration with Zed
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Add to your Zed configuration (`~/.config/zed/settings.json`):
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```json
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{
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"agent_servers": {
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"OpenCode": {
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"command": "opencode",
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"args": ["acp"]
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}
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}
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}
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```
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## Protocol Compliance
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This implementation follows the ACP specification v1:
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✅ **Initialization**
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- Proper `initialize` request/response with protocol version negotiation
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- Capability advertisement (`agentCapabilities`)
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- Authentication support (stub)
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✅ **Session Management**
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- `session/new` - Create new conversation sessions
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- `session/load` - Resume existing sessions (basic support)
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- Working directory context (`cwd`)
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- MCP server configuration support
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✅ **Prompting**
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- `session/prompt` - Process user messages
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- Content block handling (text, resources)
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- Response with stop reasons
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✅ **Client Capabilities**
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- File read/write operations
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- Permission requests
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- Terminal support (stub for future)
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## Current Limitations
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### Not Yet Implemented
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1. **Streaming Responses** - Currently returns complete responses instead of streaming via `session/update` notifications
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2. **Tool Call Reporting** - Doesn't report tool execution progress
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3. **Session Modes** - No mode switching support yet
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4. **Authentication** - No actual auth implementation
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5. **Terminal Support** - Placeholder only
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6. **Session Persistence** - `session/load` doesn't restore actual conversation history
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### Future Enhancements
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- **Real-time Streaming**: Implement `session/update` notifications for progressive responses
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- **Tool Call Visibility**: Report tool executions as they happen
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- **Session Persistence**: Save and restore full conversation history
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- **Mode Support**: Implement different operational modes (ask, code, etc.)
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- **Enhanced Permissions**: More sophisticated permission handling
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- **Terminal Integration**: Full terminal support via opencode's bash tool
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## Testing
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```bash
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# Run ACP tests
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bun test test/acp.test.ts
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# Test manually with stdio
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echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":1}}' | opencode acp
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```
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## Design Decisions
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### Why the Official Library?
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We use `@zed-industries/agent-client-protocol` instead of implementing JSON-RPC ourselves because:
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- Ensures protocol compliance
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- Handles edge cases and future protocol versions
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- Reduces maintenance burden
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- Works with other ACP clients automatically
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### Clean Architecture
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Each component has a single responsibility:
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- **Agent** = Protocol interface
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- **Client** = Client-side operations
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- **Session** = State management
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- **Server** = Lifecycle and I/O
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This makes the codebase maintainable and testable.
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### Mapping to OpenCode
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ACP sessions map cleanly to opencode's internal session model:
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- ACP `session/new` → creates internal Session
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- ACP `session/prompt` → uses SessionPrompt.prompt()
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- Working directory context preserved per-session
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- Tool execution uses existing ToolRegistry
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## References
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- [ACP Specification](https://agentclientprotocol.com/)
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- [TypeScript Library](https://github.com/zed-industries/agent-client-protocol/tree/main/typescript)
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- [Protocol Examples](https://github.com/zed-industries/agent-client-protocol/tree/main/typescript/examples)

‎packages/opencode/src/acp/agent.ts‎

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import type {
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Agent,
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AuthenticateRequest,
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AuthenticateResponse,
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CancelNotification,
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InitializeRequest,
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InitializeResponse,
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LoadSessionRequest,
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LoadSessionResponse,
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NewSessionRequest,
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NewSessionResponse,
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PromptRequest,
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PromptResponse,
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} from "@zed-industries/agent-client-protocol"
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import { Log } from "../util/log"
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import { ACPSessionManager } from "./session"
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import type { ACPConfig } from "./types"
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import { Provider } from "../provider/provider"
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import { SessionPrompt } from "../session/prompt"
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import { Identifier } from "../id/id"
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import type { MessageV2 } from "../session/message-v2"
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export class OpenCodeAgent implements Agent {
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private log = Log.create({ service: "acp-agent" })
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private sessionManager = new ACPSessionManager()
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private config: ACPConfig
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constructor(config: ACPConfig = {}) {
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this.config = config
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}
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async initialize(params: InitializeRequest): Promise<InitializeResponse> {
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this.log.info("initialize", { protocolVersion: params.protocolVersion })
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return {
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protocolVersion: 1,
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agentCapabilities: {
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loadSession: false,
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},
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_meta: {
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opencode: {
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version: await import("../installation").then((m) => m.Installation.VERSION),
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},
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},
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}
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}
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async authenticate(params: AuthenticateRequest): Promise<void | AuthenticateResponse> {
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this.log.info("authenticate", { methodId: params.methodId })
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throw new Error("Authentication not yet implemented")
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}
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async newSession(params: NewSessionRequest): Promise<NewSessionResponse> {
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this.log.info("newSession", { cwd: params.cwd, mcpServers: params.mcpServers.length })
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const session = await this.sessionManager.create(params.cwd, params.mcpServers)
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return {
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sessionId: session.id,
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_meta: {},
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}
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}
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async loadSession(params: LoadSessionRequest): Promise<LoadSessionResponse> {
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this.log.info("loadSession", { sessionId: params.sessionId, cwd: params.cwd })
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await this.sessionManager.load(params.sessionId, params.cwd, params.mcpServers)
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return {
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_meta: {},
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}
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}
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async prompt(params: PromptRequest): Promise<PromptResponse> {
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this.log.info("prompt", {
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sessionId: params.sessionId,
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promptLength: params.prompt.length,
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})
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const acpSession = this.sessionManager.get(params.sessionId)
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if (!acpSession) {
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throw new Error(`Session not found: ${params.sessionId}`)
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}
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const model = this.config.defaultModel || (await Provider.defaultModel())
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const parts = params.prompt.map((content) => {
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if (content.type === "text") {
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return {
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type: "text" as const,
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text: content.text,
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}
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}
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if (content.type === "resource") {
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const resource = content.resource
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let text = ""
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if ("text" in resource && typeof resource.text === "string") {
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text = resource.text
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}
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return {
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type: "text" as const,
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text,
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}
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}
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return {
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type: "text" as const,
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text: JSON.stringify(content),
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}
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})
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const response = await SessionPrompt.prompt({
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sessionID: acpSession.openCodeSessionId,
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messageID: Identifier.ascending("message"),
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model: {
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providerID: model.providerID,
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modelID: model.modelID,
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},
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parts,
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})
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const textParts = response.parts
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.filter((p): p is MessageV2.TextPart => p.type === "text")
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.map((p) => p.text)
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.join("\n")
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this.log.debug("prompt response", { text: textParts.slice(0, 100) })
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return {
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stopReason: "end_turn",
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_meta: {},
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}
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}
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async cancel(params: CancelNotification): Promise<void> {
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this.log.info("cancel", { sessionId: params.sessionId })
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}
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}

‎packages/opencode/src/acp/client.ts‎

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import type {
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Client,
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CreateTerminalRequest,
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CreateTerminalResponse,
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KillTerminalCommandRequest,
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KillTerminalResponse,
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ReadTextFileRequest,
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ReadTextFileResponse,
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ReleaseTerminalRequest,
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ReleaseTerminalResponse,
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RequestPermissionRequest,
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RequestPermissionResponse,
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SessionNotification,
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TerminalOutputRequest,
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TerminalOutputResponse,
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WaitForTerminalExitRequest,
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WaitForTerminalExitResponse,
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WriteTextFileRequest,
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WriteTextFileResponse,
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} from "@zed-industries/agent-client-protocol"
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import { Log } from "../util/log"
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export class ACPClient implements Client {
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private log = Log.create({ service: "acp-client" })
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async requestPermission(params: RequestPermissionRequest): Promise<RequestPermissionResponse> {
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this.log.debug("requestPermission", params)
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const firstOption = params.options[0]
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if (!firstOption) {
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return { outcome: { outcome: "cancelled" } }
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}
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return {
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outcome: {
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outcome: "selected",
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optionId: firstOption.optionId,
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},
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}
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}
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async sessionUpdate(params: SessionNotification): Promise<void> {
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this.log.debug("sessionUpdate", { sessionId: params.sessionId })
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}
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async writeTextFile(params: WriteTextFileRequest): Promise<WriteTextFileResponse> {
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this.log.debug("writeTextFile", { path: params.path })
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await Bun.write(params.path, params.content)
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return { _meta: {} }
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}
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async readTextFile(params: ReadTextFileRequest): Promise<ReadTextFileResponse> {
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this.log.debug("readTextFile", { path: params.path })
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const file = Bun.file(params.path)
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const exists = await file.exists()
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if (!exists) {
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throw new Error(`File not found: ${params.path}`)
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}
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const content = await file.text()
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return { content, _meta: {} }
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}
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async createTerminal(params: CreateTerminalRequest): Promise<CreateTerminalResponse> {
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this.log.debug("createTerminal", params)
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throw new Error("Terminal support not yet implemented")
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}
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async terminalOutput(params: TerminalOutputRequest): Promise<TerminalOutputResponse> {
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this.log.debug("terminalOutput", params)
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throw new Error("Terminal support not yet implemented")
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}
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async releaseTerminal(params: ReleaseTerminalRequest): Promise<void | ReleaseTerminalResponse> {
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this.log.debug("releaseTerminal", params)
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throw new Error("Terminal support not yet implemented")
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}
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async waitForTerminalExit(params: WaitForTerminalExitRequest): Promise<WaitForTerminalExitResponse> {
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this.log.debug("waitForTerminalExit", params)
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throw new Error("Terminal support not yet implemented")
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}
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async killTerminal(params: KillTerminalCommandRequest): Promise<void | KillTerminalResponse> {
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this.log.debug("killTerminal", params)
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throw new Error("Terminal support not yet implemented")
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}
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}

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