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diff --git a/packages/core/src/services/chatRecordingService.ts b/packages/core/src/services/chatRecordingService.ts
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+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { type Config } from '../config/config.js';
+import { type Status } from '../core/coreToolScheduler.js';
+import { type ThoughtSummary } from '../core/turn.js';
+import { getProjectHash } from '../utils/paths.js';
+import path from 'node:path';
+import fs from 'node:fs';
+import { randomUUID } from 'node:crypto';
+import { PartListUnion } from '@google/genai';
+
+/**
+ * Token usage summary for a message or conversation.
+ */
+export interface TokensSummary {
+  input: number; // promptTokenCount
+  output: number; // candidatesTokenCount
+  cached: number; // cachedContentTokenCount
+  thoughts?: number; // thoughtsTokenCount
+  tool?: number; // toolUsePromptTokenCount
+  total: number; // totalTokenCount
+}
+
+/**
+ * Base fields common to all messages.
+ */
+export interface BaseMessageRecord {
+  id: string;
+  timestamp: string;
+  content: string;
+}
+
+/**
+ * Record of a tool call execution within a conversation.
+ */
+export interface ToolCallRecord {
+  id: string;
+  name: string;
+  args: Record<string, unknown>;
+  result?: PartListUnion | null;
+  status: Status;
+  timestamp: string;
+  // UI-specific fields for display purposes
+  displayName?: string;
+  description?: string;
+  resultDisplay?: string;
+  renderOutputAsMarkdown?: boolean;
+}
+
+/**
+ * Message type and message type-specific fields.
+ */
+export type ConversationRecordExtra =
+  | {
+      type: 'user';
+    }
+  | {
+      type: 'gemini';
+      toolCalls?: ToolCallRecord[];
+      thoughts?: Array<ThoughtSummary & { timestamp: string }>;
+      tokens?: TokensSummary | null;
+      model?: string;
+    };
+
+/**
+ * A single message record in a conversation.
+ */
+export type MessageRecord = BaseMessageRecord & ConversationRecordExtra;
+
+/**
+ * Complete conversation record stored in session files.
+ */
+export interface ConversationRecord {
+  sessionId: string;
+  projectHash: string;
+  startTime: string;
+  lastUpdated: string;
+  messages: MessageRecord[];
+}
+
+/**
+ * Data structure for resuming an existing session.
+ */
+export interface ResumedSessionData {
+  conversation: ConversationRecord;
+  filePath: string;
+}
+
+/**
+ * Service for automatically recording chat conversations to disk.
+ *
+ * This service provides comprehensive conversation recording that captures:
+ * - All user and assistant messages
+ * - Tool calls and their execution results
+ * - Token usage statistics
+ * - Assistant thoughts and reasoning
+ *
+ * Sessions are stored as JSON files in ~/.gemini/tmp/<project_hash>/chats/
+ */
+export class ChatRecordingService {
+  private conversationFile: string | null = null;
+  private cachedLastConvData: string | null = null;
+  private sessionId: string;
+  private projectHash: string;
+  private queuedThoughts: Array<ThoughtSummary & { timestamp: string }> = [];
+  private queuedTokens: TokensSummary | null = null;
+  private config: Config;
+
+  constructor(config: Config) {
+    this.config = config;
+    this.sessionId = config.getSessionId();
+    this.projectHash = getProjectHash(config.getProjectRoot());
+  }
+
+  /**
+   * Initializes the chat recording service: creates a new conversation file and associates it with
+   * this service instance, or resumes from an existing session if resumedSessionData is provided.
+   */
+  initialize(resumedSessionData?: ResumedSessionData): void {
+    try {
+      if (resumedSessionData) {
+        // Resume from existing session
+        this.conversationFile = resumedSessionData.filePath;
+        this.sessionId = resumedSessionData.conversation.sessionId;
+
+        // Update the session ID in the existing file
+        this.updateConversation((conversation) => {
+          conversation.sessionId = this.sessionId;
+        });
+
+        // Clear any cached data to force fresh reads
+        this.cachedLastConvData = null;
+      } else {
+        // Create new session
+        const chatsDir = path.join(this.config.getProjectTempDir(), 'chats');
+        fs.mkdirSync(chatsDir, { recursive: true });
+
+        const timestamp = new Date()
+          .toISOString()
+          .slice(0, 16)
+          .replace(/:/g, '-');
+        const filename = `session-${timestamp}-${this.sessionId.slice(
+          0,
+          8,
+        )}.json`;
+        this.conversationFile = path.join(chatsDir, filename);
+
+        this.writeConversation({
+          sessionId: this.sessionId,
+          projectHash: this.projectHash,
+          startTime: new Date().toISOString(),
+          lastUpdated: new Date().toISOString(),
+          messages: [],
+        });
+      }
+
+      // Clear any queued data since this is a fresh start
+      this.queuedThoughts = [];
+      this.queuedTokens = null;
+    } catch (error) {
+      console.error('Error initializing chat recording service:', error);
+      throw error;
+    }
+  }
+
+  private getLastMessage(
+    conversation: ConversationRecord,
+  ): MessageRecord | undefined {
+    return conversation.messages.at(-1);
+  }
+
+  private newMessage(
+    type: ConversationRecordExtra['type'],
+    content: string,
+  ): MessageRecord {
+    return {
+      id: randomUUID(),
+      timestamp: new Date().toISOString(),
+      type,
+      content,
+    };
+  }
+
+  /**
+   * Records a message in the conversation.
+   */
+  recordMessage(message: {
+    type: ConversationRecordExtra['type'];
+    content: string;
+    append?: boolean;
+  }): void {
+    if (!this.conversationFile) return;
+
+    try {
+      this.updateConversation((conversation) => {
+        if (message.append) {
+          const lastMsg = this.getLastMessage(conversation);
+          if (lastMsg && lastMsg.type === message.type) {
+            lastMsg.content += message.content;
+            return;
+          }
+        }
+        // We're not appending, or we are appending but the last message's type is not the same as
+        // the specified type, so just create a new message.
+        const msg = this.newMessage(message.type, message.content);
+        if (msg.type === 'gemini') {
+          // If it's a new Gemini message then incorporate any queued thoughts.
+          conversation.messages.push({
+            ...msg,
+            thoughts: this.queuedThoughts,
+            tokens: this.queuedTokens,
+            model: this.config.getModel(),
+          });
+          this.queuedThoughts = [];
+          this.queuedTokens = null;
+        } else {
+          // Or else just add it.
+          conversation.messages.push(msg);
+        }
+      });
+    } catch (error) {
+      console.error('Error saving message:', error);
+      throw error;
+    }
+  }
+
+  /**
+   * Records a thought from the assistant's reasoning process.
+   */
+  recordThought(thought: ThoughtSummary): void {
+    if (!this.conversationFile) return;
+
+    try {
+      this.queuedThoughts.push({
+        ...thought,
+        timestamp: new Date().toISOString(),
+      });
+    } catch (error) {
+      if (this.config.getDebugMode()) {
+        console.error('Error saving thought:', error);
+        throw error;
+      }
+    }
+  }
+
+  /**
+   * Updates the tokens for the last message in the conversation (which should be by Gemini).
+   */
+  recordMessageTokens(tokens: {
+    input: number;
+    output: number;
+    cached: number;
+    thoughts?: number;
+    tool?: number;
+    total: number;
+  }): void {
+    if (!this.conversationFile) return;
+
+    try {
+      this.updateConversation((conversation) => {
+        const lastMsg = this.getLastMessage(conversation);
+        // If the last message already has token info, it's because this new token info is for a
+        // new message that hasn't been recorded yet.
+        if (lastMsg && lastMsg.type === 'gemini' && !lastMsg.tokens) {
+          lastMsg.tokens = tokens;
+          this.queuedTokens = null;
+        } else {
+          this.queuedTokens = tokens;
+        }
+      });
+    } catch (error) {
+      console.error('Error updating message tokens:', error);
+      throw error;
+    }
+  }
+
+  /**
+   * Adds tool calls to the last message in the conversation (which should be by Gemini).
+   */
+  recordToolCalls(toolCalls: ToolCallRecord[]): void {
+    if (!this.conversationFile) return;
+
+    try {
+      this.updateConversation((conversation) => {
+        const lastMsg = this.getLastMessage(conversation);
+        // If a tool call was made, but the last message isn't from Gemini, it's because Gemini is
+        // calling tools without starting the message with text.  So the user submits a prompt, and
+        // Gemini immediately calls a tool (maybe with some thinking first).  In that case, create
+        // a new empty Gemini message.
+        // Also if there are any queued thoughts, it means this tool call(s) is from a new Gemini
+        // message--because it's thought some more since we last, if ever, created a new Gemini
+        // message from tool calls, when we dequeued the thoughts.
+        if (
+          !lastMsg ||
+          lastMsg.type !== 'gemini' ||
+          this.queuedThoughts.length > 0
+        ) {
+          const newMsg: MessageRecord = {
+            ...this.newMessage('gemini' as const, ''),
+            // This isn't strictly necessary, but TypeScript apparently can't
+            // tell that the first parameter to newMessage() becomes the
+            // resulting message's type, and so it thinks that toolCalls may
+            // not be present.  Confirming the type here satisfies it.
+            type: 'gemini' as const,
+            toolCalls,
+            thoughts: this.queuedThoughts,
+            model: this.config.getModel(),
+          };
+          // If there are any queued thoughts join them to this message.
+          if (this.queuedThoughts.length > 0) {
+            newMsg.thoughts = this.queuedThoughts;
+            this.queuedThoughts = [];
+          }
+          // If there's any queued tokens info join it to this message.
+          if (this.queuedTokens) {
+            newMsg.tokens = this.queuedTokens;
+            this.queuedTokens = null;
+          }
+          conversation.messages.push(newMsg);
+        } else {
+          // The last message is an existing Gemini message that we need to update.
+
+          // Update any existing tool call entries.
+          if (!lastMsg.toolCalls) {
+            lastMsg.toolCalls = [];
+          }
+          lastMsg.toolCalls = lastMsg.toolCalls.map((toolCall) => {
+            // If there are multiple tool calls with the same ID, this will take the first one.
+            const incomingToolCall = toolCalls.find(
+              (tc) => tc.id === toolCall.id,
+            );
+            if (incomingToolCall) {
+              // Merge in the new data to keep preserve thoughts, etc., that were assigned to older
+              // versions of the tool call.
+              return { ...toolCall, ...incomingToolCall };
+            } else {
+              return toolCall;
+            }
+          });
+
+          // Add any new tools calls that aren't in the message yet.
+          for (const toolCall of toolCalls) {
+            const existingToolCall = lastMsg.toolCalls.find(
+              (tc) => tc.id === toolCall.id,
+            );
+            if (!existingToolCall) {
+              lastMsg.toolCalls.push(toolCall);
+            }
+          }
+        }
+      });
+    } catch (error) {
+      console.error('Error adding tool call to message:', error);
+      throw error;
+    }
+  }
+
+  /**
+   * Loads up the conversation record from disk.
+   */
+  private readConversation(): ConversationRecord {
+    try {
+      this.cachedLastConvData = fs.readFileSync(this.conversationFile!, 'utf8');
+      return JSON.parse(this.cachedLastConvData);
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
+        console.error('Error reading conversation file:', error);
+        throw error;
+      }
+
+      // Placeholder empty conversation if file doesn't exist.
+      return {
+        sessionId: this.sessionId,
+        projectHash: this.projectHash,
+        startTime: new Date().toISOString(),
+        lastUpdated: new Date().toISOString(),
+        messages: [],
+      };
+    }
+  }
+
+  /**
+   * Saves the conversation record; overwrites the file.
+   */
+  private writeConversation(conversation: ConversationRecord): void {
+    try {
+      if (!this.conversationFile) return;
+      // Don't write the file yet until there's at least one message.
+      if (conversation.messages.length === 0) return;
+
+      // Only write the file if this change would change the file.
+      if (this.cachedLastConvData !== JSON.stringify(conversation, null, 2)) {
+        conversation.lastUpdated = new Date().toISOString();
+        const newContent = JSON.stringify(conversation, null, 2);
+        this.cachedLastConvData = newContent;
+        fs.writeFileSync(this.conversationFile, newContent);
+      }
+    } catch (error) {
+      console.error('Error writing conversation file:', error);
+      throw error;
+    }
+  }
+
+  /**
+   * Convenient helper for updating the conversation without file reading and writing and time
+   * updating boilerplate.
+   */
+  private updateConversation(
+    updateFn: (conversation: ConversationRecord) => void,
+  ) {
+    const conversation = this.readConversation();
+    updateFn(conversation);
+    this.writeConversation(conversation);
+  }
+
+  /**
+   * Deletes a session file by session ID.
+   */
+  deleteSession(sessionId: string): void {
+    try {
+      const chatsDir = path.join(this.config.getProjectTempDir(), 'chats');
+      const sessionPath = path.join(chatsDir, `${sessionId}.json`);
+      fs.unlinkSync(sessionPath);
+    } catch (error) {
+      console.error('Error deleting session:', error);
+      throw error;
+    }
+  }
+}