feat: Add ACP (Agent Client Protocol) support (#2947)

Co-authored-by: opencode-bot <devnull@opencode.local>
Co-authored-by: Dax Raad <d@ironbay.co>
Co-authored-by: GitHub Action <action@github.com>

packages/opencode/src/acp/agent.ts

@@ -0,0 +1,141 @@
+import type {
+  Agent,
+  AgentSideConnection,
+  AuthenticateRequest,
+  AuthenticateResponse,
+  CancelNotification,
+  InitializeRequest,
+  InitializeResponse,
+  LoadSessionRequest,
+  LoadSessionResponse,
+  NewSessionRequest,
+  NewSessionResponse,
+  PromptRequest,
+  PromptResponse,
+} from "@zed-industries/agent-client-protocol"
+import { Log } from "../util/log"
+import { ACPSessionManager } from "./session"
+import type { ACPConfig } from "./types"
+import { Provider } from "../provider/provider"
+import { SessionPrompt } from "../session/prompt"
+import { Identifier } from "../id/id"
+
+export class OpenCodeAgent implements Agent {
+  private log = Log.create({ service: "acp-agent" })
+  private sessionManager = new ACPSessionManager()
+  private connection: AgentSideConnection
+  private config: ACPConfig
+
+  constructor(connection: AgentSideConnection, config: ACPConfig = {}) {
+    this.connection = connection
+    this.config = config
+  }
+
+  async initialize(params: InitializeRequest): Promise<InitializeResponse> {
+    this.log.info("initialize", { protocolVersion: params.protocolVersion })
+
+    return {
+      protocolVersion: 1,
+      agentCapabilities: {
+        loadSession: false,
+      },
+      _meta: {
+        opencode: {
+          version: await import("../installation").then((m) => m.Installation.VERSION),
+        },
+      },
+    }
+  }
+
+  async authenticate(params: AuthenticateRequest): Promise<void | AuthenticateResponse> {
+    this.log.info("authenticate", { methodId: params.methodId })
+    throw new Error("Authentication not yet implemented")
+  }
+
+  async newSession(params: NewSessionRequest): Promise<NewSessionResponse> {
+    this.log.info("newSession", { cwd: params.cwd, mcpServers: params.mcpServers.length })
+
+    const session = await this.sessionManager.create(params.cwd, params.mcpServers)
+
+    return {
+      sessionId: session.id,
+      _meta: {},
+    }
+  }
+
+  async loadSession(params: LoadSessionRequest): Promise<LoadSessionResponse> {
+    this.log.info("loadSession", { sessionId: params.sessionId, cwd: params.cwd })
+
+    await this.sessionManager.load(params.sessionId, params.cwd, params.mcpServers)
+
+    return {
+      _meta: {},
+    }
+  }
+
+  async prompt(params: PromptRequest): Promise<PromptResponse> {
+    this.log.info("prompt", {
+      sessionId: params.sessionId,
+      promptLength: params.prompt.length,
+    })
+
+    const acpSession = this.sessionManager.get(params.sessionId)
+    if (!acpSession) {
+      throw new Error(`Session not found: ${params.sessionId}`)
+    }
+
+    const model = this.config.defaultModel || (await Provider.defaultModel())
+
+    const parts = params.prompt.map((content) => {
+      if (content.type === "text") {
+        return {
+          type: "text" as const,
+          text: content.text,
+        }
+      }
+      if (content.type === "resource") {
+        const resource = content.resource
+        let text = ""
+        if ("text" in resource && typeof resource.text === "string") {
+          text = resource.text
+        }
+        return {
+          type: "text" as const,
+          text,
+        }
+      }
+      return {
+        type: "text" as const,
+        text: JSON.stringify(content),
+      }
+    })
+
+    await SessionPrompt.prompt({
+      sessionID: acpSession.openCodeSessionId,
+      messageID: Identifier.ascending("message"),
+      model: {
+        providerID: model.providerID,
+        modelID: model.modelID,
+      },
+      parts,
+      acpConnection: {
+        connection: this.connection,
+        sessionId: params.sessionId,
+      },
+    })
+
+    this.log.debug("prompt response completed")
+
+    // Streaming notifications are now handled during prompt execution
+    // No need to send final text chunk here
+
+    return {
+      stopReason: "end_turn",
+      _meta: {},
+    }
+  }
+
+  async cancel(params: CancelNotification): Promise<void> {
+    this.log.info("cancel", { sessionId: params.sessionId })
+  }
+}