feat(acp): add session resume support (#18043)

Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

packages/cli/src/zed-integration/zedIntegration.ts

@@ -10,6 +10,7 @@ import type {
   ToolResult,
   ToolCallConfirmationDetails,
   FilterFilesOptions,
+  ConversationRecord,
 } from '@google/gemini-cli-core';
 import {
   AuthType,
@@ -32,6 +33,7 @@ import {
   createWorkingStdio,
   startupProfiler,
   Kind,
+  partListUnionToString,
 } from '@google/gemini-cli-core';
 import * as acp from '@agentclientprotocol/sdk';
 import { AcpFileSystemService } from './fileSystemService.js';
@@ -47,6 +49,10 @@ import { randomUUID } from 'node:crypto';
 import type { CliArgs } from '../config/config.js';
 import { loadCliConfig } from '../config/config.js';
 import { runExitCleanup } from '../utils/cleanup.js';
+import {
+  SessionSelector,
+  convertSessionToHistoryFormats,
+} from '../utils/sessionUtils.js';
 
 export async function runZedIntegration(
   config: Config,
@@ -107,7 +113,7 @@ export class GeminiAgent {
       protocolVersion: acp.PROTOCOL_VERSION,
       authMethods,
       agentCapabilities: {
-        loadSession: false,
+        loadSession: true,
         promptCapabilities: {
           image: true,
           audio: true,
@@ -146,23 +152,11 @@ export class GeminiAgent {
     mcpServers,
   }: acp.NewSessionRequest): Promise<acp.NewSessionResponse> {
     const sessionId = randomUUID();
-    const config = await this.newSessionConfig(sessionId, cwd, mcpServers);
-
-    let isAuthenticated = false;
-    if (this.settings.merged.security.auth.selectedType) {
-      try {
-        await config.refreshAuth(
-          this.settings.merged.security.auth.selectedType,
-        );
-        isAuthenticated = true;
-      } catch (e) {
-        debugLogger.error(`Authentication failed: ${e}`);
-      }
-    }
-
-    if (!isAuthenticated) {
-      throw acp.RequestError.authRequired();
-    }
+    const config = await this.initializeSessionConfig(
+      sessionId,
+      cwd,
+      mcpServers,
+    );
 
     if (this.clientCapabilities?.fs) {
       const acpFileSystemService = new AcpFileSystemService(
@@ -184,6 +178,88 @@ export class GeminiAgent {
     };
   }
 
+  async loadSession({
+    sessionId,
+    cwd,
+    mcpServers,
+  }: acp.LoadSessionRequest): Promise<acp.LoadSessionResponse> {
+    const config = await this.initializeSessionConfig(
+      sessionId,
+      cwd,
+      mcpServers,
+    );
+
+    const sessionSelector = new SessionSelector(config);
+    const { sessionData, sessionPath } =
+      await sessionSelector.resolveSession(sessionId);
+
+    if (this.clientCapabilities?.fs) {
+      const acpFileSystemService = new AcpFileSystemService(
+        this.connection,
+        sessionId,
+        this.clientCapabilities.fs,
+        config.getFileSystemService(),
+      );
+      config.setFileSystemService(acpFileSystemService);
+    }
+
+    const { clientHistory } = convertSessionToHistoryFormats(
+      sessionData.messages,
+    );
+
+    const geminiClient = config.getGeminiClient();
+    await geminiClient.initialize();
+    await geminiClient.resumeChat(clientHistory, {
+      conversation: sessionData,
+      filePath: sessionPath,
+    });
+
+    const session = new Session(
+      sessionId,
+      geminiClient.getChat(),
+      config,
+      this.connection,
+    );
+    this.sessions.set(sessionId, session);
+
+    // Stream history back to client
+    // eslint-disable-next-line @typescript-eslint/no-floating-promises
+    session.streamHistory(sessionData.messages);
+
+    return {};
+  }
+
+  private async initializeSessionConfig(
+    sessionId: string,
+    cwd: string,
+    mcpServers: acp.McpServer[],
+  ): Promise<Config> {
+    const selectedAuthType = this.settings.merged.security.auth.selectedType;
+    if (!selectedAuthType) {
+      throw acp.RequestError.authRequired();
+    }
+
+    // 1. Create config WITHOUT initializing it (no MCP servers started yet)
+    const config = await this.newSessionConfig(sessionId, cwd, mcpServers);
+
+    // 2. Authenticate BEFORE initializing configuration or starting MCP servers.
+    // This satisfies the security requirement to verify the user before executing
+    // potentially unsafe server definitions.
+    try {
+      await config.refreshAuth(selectedAuthType);
+    } catch (e) {
+      debugLogger.error(`Authentication failed: ${e}`);
+      throw acp.RequestError.authRequired();
+    }
+
+    // 3. Now that we are authenticated, it is safe to initialize the config
+    // which starts the MCP servers and other heavy resources.
+    await config.initialize();
+    startupProfiler.flush(config);
+
+    return config;
+  }
+
   async newSessionConfig(
     sessionId: string,
     cwd: string,
@@ -228,8 +304,6 @@ export class GeminiAgent {
 
     const config = await loadCliConfig(settings, sessionId, this.argv, { cwd });
 
-    await config.initialize();
-    startupProfiler.flush(config);
     return config;
   }
 
@@ -269,6 +343,73 @@ export class Session {
     this.pendingPrompt = null;
   }
 
+  async streamHistory(messages: ConversationRecord['messages']): Promise<void> {
+    for (const msg of messages) {
+      const contentString = partListUnionToString(msg.content);
+
+      if (msg.type === 'user') {
+        if (contentString.trim()) {
+          await this.sendUpdate({
+            sessionUpdate: 'user_message_chunk',
+            content: { type: 'text', text: contentString },
+          });
+        }
+      } else if (msg.type === 'gemini') {
+        // Thoughts
+        if (msg.thoughts) {
+          for (const thought of msg.thoughts) {
+            const thoughtText = `**${thought.subject}**\n${thought.description}`;
+            await this.sendUpdate({
+              sessionUpdate: 'agent_thought_chunk',
+              content: { type: 'text', text: thoughtText },
+            });
+          }
+        }
+
+        // Message text
+        if (contentString.trim()) {
+          await this.sendUpdate({
+            sessionUpdate: 'agent_message_chunk',
+            content: { type: 'text', text: contentString },
+          });
+        }
+
+        // Tool calls
+        if (msg.toolCalls) {
+          for (const toolCall of msg.toolCalls) {
+            const toolCallContent: acp.ToolCallContent[] = [];
+            if (toolCall.resultDisplay) {
+              if (typeof toolCall.resultDisplay === 'string') {
+                toolCallContent.push({
+                  type: 'content',
+                  content: { type: 'text', text: toolCall.resultDisplay },
+                });
+              } else if ('fileName' in toolCall.resultDisplay) {
+                toolCallContent.push({
+                  type: 'diff',
+                  path: toolCall.resultDisplay.fileName,
+                  oldText: toolCall.resultDisplay.originalContent,
+                  newText: toolCall.resultDisplay.newContent,
+                });
+              }
+            }
+
+            const tool = this.config.getToolRegistry().getTool(toolCall.name);
+
+            await this.sendUpdate({
+              sessionUpdate: 'tool_call',
+              toolCallId: toolCall.id,
+              status: toolCall.status === 'success' ? 'completed' : 'failed',
+              title: toolCall.displayName || toolCall.name,
+              content: toolCallContent,
+              kind: tool ? toAcpToolKind(tool.kind) : 'other',
+            });
+          }
+        }
+      }
+    }
+  }
+
   async prompt(params: acp.PromptRequest): Promise<acp.PromptResponse> {
     this.pendingPrompt?.abort();
     const pendingSend = new AbortController();
@@ -533,6 +674,33 @@ export class Session {
         ),
       );
 
+      this.chat.recordCompletedToolCalls(this.config.getActiveModel(), [
+        {
+          status: 'success',
+          request: {
+            callId,
+            name: fc.name,
+            args,
+            isClientInitiated: false,
+            prompt_id: promptId,
+          },
+          tool,
+          invocation,
+          response: {
+            callId,
+            responseParts: convertToFunctionResponse(
+              fc.name,
+              callId,
+              toolResult.llmContent,
+              this.config.getActiveModel(),
+            ),
+            resultDisplay: toolResult.returnDisplay,
+            error: undefined,
+            errorType: undefined,
+          },
+        },
+      ]);
+
       return convertToFunctionResponse(
         fc.name,
         callId,
@@ -551,6 +719,35 @@ export class Session {
         ],
       });
 
+      this.chat.recordCompletedToolCalls(this.config.getActiveModel(), [
+        {
+          status: 'error',
+          request: {
+            callId,
+            name: fc.name,
+            args,
+            isClientInitiated: false,
+            prompt_id: promptId,
+          },
+          tool,
+          response: {
+            callId,
+            responseParts: [
+              {
+                functionResponse: {
+                  id: callId,
+                  name: fc.name ?? '',
+                  response: { error: error.message },
+                },
+              },
+            ],
+            resultDisplay: error.message,
+            error,
+            errorType: undefined,
+          },
+        },
+      ]);
+
       return errorResponse(error);
     }
   }