diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index c5788a67..0f7174fd 100644
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -120,6 +120,7 @@ export async function loadCliConfig(
   settings: Settings,
   extensions: ExtensionConfig[],
   geminiIgnorePatterns: string[],
+  sessionId: string,
 ): Promise<Config> {
   loadEnvironment();
 
@@ -148,6 +149,7 @@ export async function loadCliConfig(
   const mcpServers = mergeMcpServers(settings, extensions);
 
   return new Config({
+    sessionId,
     contentGeneratorConfig,
     embeddingModel: DEFAULT_GEMINI_EMBEDDING_MODEL,
     sandbox: argv.sandbox ?? settings.sandbox,
diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index f0044780..eb4f6bb6 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -31,6 +31,7 @@ import {
   WebFetchTool,
   WebSearchTool,
   WriteFileTool,
+  sessionId,
 } from '@gemini-cli/core';
 
 export async function main() {
@@ -57,6 +58,7 @@ export async function main() {
     settings.merged,
     extensions,
     geminiIgnorePatterns,
+    sessionId,
   );
 
   // Initialize centralized FileDiscoveryService
@@ -180,5 +182,6 @@ async function loadNonInteractiveConfig(
     nonInteractiveSettings,
     extensions,
     config.getGeminiIgnorePatterns(),
+    config.getSessionId(),
   );
 }
diff --git a/packages/cli/src/ui/App.test.tsx b/packages/cli/src/ui/App.test.tsx
index 0fcb0e61..fefb2fe2 100644
--- a/packages/cli/src/ui/App.test.tsx
+++ b/packages/cli/src/ui/App.test.tsx
@@ -190,6 +190,7 @@ describe('App UI', () => {
       userMemory: '',
       geminiMdFileCount: 0,
       showMemoryUsage: false,
+      sessionId: 'test-session-id',
       // Provide other required fields for ConfigParameters if necessary
     }) as unknown as MockServerConfig;
 
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
index 4d677f1e..69fb6d06 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
@@ -493,7 +493,7 @@ Add any other context about the problem here.
         description: 'save conversation checkpoint. Usage: /save [tag]',
         action: async (_mainCommand, subCommand, _args) => {
           const tag = (subCommand || '').trim();
-          const logger = new Logger();
+          const logger = new Logger(config?.getSessionId() || '');
           await logger.initialize();
           const chat = await config?.getGeminiClient()?.getChat();
           const history = chat?.getHistory() || [];
@@ -519,7 +519,7 @@ Add any other context about the problem here.
           'resume from conversation checkpoint. Usage: /resume [tag]',
         action: async (_mainCommand, subCommand, _args) => {
           const tag = (subCommand || '').trim();
-          const logger = new Logger();
+          const logger = new Logger(config?.getSessionId() || '');
           await logger.initialize();
           const conversation = await logger.loadCheckpoint(tag);
           if (conversation.length === 0) {
diff --git a/packages/cli/src/ui/hooks/useLogger.ts b/packages/cli/src/ui/hooks/useLogger.ts
index ea6227ce..ea6d6057 100644
--- a/packages/cli/src/ui/hooks/useLogger.ts
+++ b/packages/cli/src/ui/hooks/useLogger.ts
@@ -5,6 +5,7 @@
  */
 
 import { useState, useEffect } from 'react';
+import { sessionId } from '@gemini-cli/core';
 import { Logger } from '@gemini-cli/core';
 
 /**
@@ -14,7 +15,7 @@ export const useLogger = () => {
   const [logger, setLogger] = useState<Logger | null>(null);
 
   useEffect(() => {
-    const newLogger = new Logger();
+    const newLogger = new Logger(sessionId);
     /**
      * Start async initialization, no need to await. Using await slows down the
      * time from launch to see the gemini-cli prompt and it's better to not save
diff --git a/packages/core/src/config/config.test.ts b/packages/core/src/config/config.test.ts
index df3b3de3..2827f581 100644
--- a/packages/core/src/config/config.test.ts
+++ b/packages/core/src/config/config.test.ts
@@ -49,6 +49,7 @@ describe('Server Config (config.ts)', () => {
   const USER_MEMORY = 'Test User Memory';
   const TELEMETRY = false;
   const EMBEDDING_MODEL = 'gemini-embedding';
+  const SESSION_ID = 'test-session-id';
   const baseParams: ConfigParameters = {
     contentGeneratorConfig: {
       apiKey: API_KEY,
@@ -62,6 +63,7 @@ describe('Server Config (config.ts)', () => {
     fullContext: FULL_CONTEXT,
     userMemory: USER_MEMORY,
     telemetry: TELEMETRY,
+    sessionId: SESSION_ID,
   };
 
   beforeEach(() => {
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 66dac829..d42fbbec 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -55,6 +55,7 @@ export class MCPServerConfig {
 }
 
 export interface ConfigParameters {
+  sessionId: string;
   contentGeneratorConfig: ContentGeneratorConfig;
   embeddingModel: string;
   sandbox?: boolean | string;
@@ -83,6 +84,7 @@ export interface ConfigParameters {
 
 export class Config {
   private toolRegistry: Promise<ToolRegistry>;
+  private readonly sessionId: string;
   private readonly contentGeneratorConfig: ContentGeneratorConfig;
   private readonly embeddingModel: string;
   private readonly sandbox: boolean | string | undefined;
@@ -111,6 +113,7 @@ export class Config {
   private fileDiscoveryService: FileDiscoveryService | null = null;
 
   constructor(params: ConfigParameters) {
+    this.sessionId = params.sessionId;
     this.contentGeneratorConfig = params.contentGeneratorConfig;
     this.embeddingModel = params.embeddingModel;
     this.sandbox = params.sandbox;
@@ -155,6 +158,10 @@ export class Config {
     }
   }
 
+  getSessionId(): string {
+    return this.sessionId;
+  }
+
   getContentGeneratorConfig(): ContentGeneratorConfig {
     return this.contentGeneratorConfig;
   }
diff --git a/packages/core/src/core/client.test.ts b/packages/core/src/core/client.test.ts
index 024544ed..0362f72a 100644
--- a/packages/core/src/core/client.test.ts
+++ b/packages/core/src/core/client.test.ts
@@ -108,6 +108,7 @@ describe('Gemini Client (client.ts)', () => {
         getUserAgent: vi.fn().mockReturnValue('test-agent'),
         getUserMemory: vi.fn().mockReturnValue(''),
         getFullContext: vi.fn().mockReturnValue(false),
+        getSessionId: vi.fn().mockReturnValue('test-session-id'),
       };
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
       return mock as any;
diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index 8de8e503..d69d571c 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -162,6 +162,7 @@ export class GeminiClient {
       return new GeminiChat(
         await this.contentGenerator,
         this.model,
+        this.config.getSessionId(),
         {
           systemInstruction,
           ...this.generateContentConfig,
diff --git a/packages/core/src/core/geminiChat.test.ts b/packages/core/src/core/geminiChat.test.ts
index dbed31b1..49341939 100644
--- a/packages/core/src/core/geminiChat.test.ts
+++ b/packages/core/src/core/geminiChat.test.ts
@@ -21,11 +21,12 @@ describe('GeminiChat', () => {
   let chat: GeminiChat;
   const model = 'gemini-pro';
   const config: GenerateContentConfig = {};
+  const sessionId = 'test-session-id';
 
   beforeEach(() => {
     vi.clearAllMocks();
     // Reset history for each test by creating a new instance
-    chat = new GeminiChat(mockModelsModule, model, config, []);
+    chat = new GeminiChat(mockModelsModule, model, sessionId, config, []);
   });
 
   afterEach(() => {
@@ -120,7 +121,7 @@ describe('GeminiChat', () => {
       chat.recordHistory(userInput, newModelOutput); // userInput here is for the *next* turn, but history is already primed
 
       // Reset and set up a more realistic scenario for merging with existing history
-      chat = new GeminiChat(mockModelsModule, model, config, []);
+      chat = new GeminiChat(mockModelsModule, model, sessionId, config, []);
       const firstUserInput: Content = {
         role: 'user',
         parts: [{ text: 'First user input' }],
@@ -163,7 +164,7 @@ describe('GeminiChat', () => {
         role: 'model',
         parts: [{ text: 'Initial model answer.' }],
       };
-      chat = new GeminiChat(mockModelsModule, model, config, [
+      chat = new GeminiChat(mockModelsModule, model, sessionId, config, [
         initialUser,
         initialModel,
       ]);
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index 47f3f3a6..a78a7884 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -18,6 +18,7 @@ import {
 import { retryWithBackoff } from '../utils/retry.js';
 import { isFunctionResponse } from '../utils/messageInspectors.js';
 import { ContentGenerator } from './contentGenerator.js';
+import { Logger } from './logger.js';
 
 /**
  * Returns true if the response is valid, false otherwise.
@@ -117,14 +118,17 @@ export class GeminiChat {
   // A promise to represent the current state of the message being sent to the
   // model.
   private sendPromise: Promise<void> = Promise.resolve();
+  private logger: Logger;
 
   constructor(
     private readonly contentGenerator: ContentGenerator,
     private readonly model: string,
+    sessionId: string,
     private readonly config: GenerateContentConfig = {},
     private history: Content[] = [],
   ) {
     validateHistory(history);
+    this.logger = new Logger(sessionId);
   }
 
   /**
diff --git a/packages/core/src/core/logger.test.ts b/packages/core/src/core/logger.test.ts
index d7bb8ef6..a3198277 100644
--- a/packages/core/src/core/logger.test.ts
+++ b/packages/core/src/core/logger.test.ts
@@ -78,15 +78,20 @@ async function readLogFile(): Promise<LogEntry[]> {
   }
 }
 
+vi.mock('../utils/session.js', () => ({
+  sessionId: 'test-session-id',
+}));
+
 describe('Logger', () => {
   let logger: Logger;
+  const testSessionId = 'test-session-id';
 
   beforeEach(async () => {
     vi.resetAllMocks();
     vi.useFakeTimers();
     vi.setSystemTime(new Date('2025-01-01T12:00:00.000Z'));
     await cleanupLogFile();
-    logger = new Logger();
+    logger = new Logger(testSessionId);
     await logger.initialize();
   });
 
@@ -111,7 +116,7 @@ describe('Logger', () => {
         /* ignore */
       }
 
-      const newLogger = new Logger();
+      const newLogger = new Logger(testSessionId);
       await newLogger.initialize();
 
       const dirExists = await fs
@@ -130,9 +135,8 @@ describe('Logger', () => {
     });
 
     it('should load existing logs and set correct messageId for the current session', async () => {
-      const fixedTime = new Date('2025-01-01T10:00:00.000Z');
-      vi.setSystemTime(fixedTime);
-      const currentSessionId = Math.floor(fixedTime.getTime() / 1000);
+      const currentSessionId = 'session-123';
+      const anotherSessionId = 'session-456';
       const existingLogs: LogEntry[] = [
         {
           sessionId: currentSessionId,
@@ -142,7 +146,7 @@ describe('Logger', () => {
           message: 'Msg1',
         },
         {
-          sessionId: currentSessionId - 100,
+          sessionId: anotherSessionId,
           messageId: 5,
           timestamp: new Date('2025-01-01T09:00:00.000Z').toISOString(),
           type: MessageSenderType.USER,
@@ -158,7 +162,7 @@ describe('Logger', () => {
       ];
       await fs.mkdir(path.join(process.cwd(), GEMINI_DIR), { recursive: true });
       await fs.writeFile(TEST_LOG_FILE_PATH, JSON.stringify(existingLogs));
-      const newLogger = new Logger();
+      const newLogger = new Logger(currentSessionId);
       await newLogger.initialize();
       expect(newLogger['messageId']).toBe(2);
       expect(newLogger['logs']).toEqual(existingLogs);
@@ -166,11 +170,9 @@ describe('Logger', () => {
     });
 
     it('should set messageId to 0 for a new session if log file exists but has no logs for current session', async () => {
-      const fixedTime = new Date('2025-01-01T14:00:00.000Z');
-      vi.setSystemTime(fixedTime);
       const existingLogs: LogEntry[] = [
         {
-          sessionId: Math.floor(fixedTime.getTime() / 1000) - 500,
+          sessionId: 'some-other-session',
           messageId: 5,
           timestamp: new Date().toISOString(),
           type: MessageSenderType.USER,
@@ -179,7 +181,7 @@ describe('Logger', () => {
       ];
       await fs.mkdir(path.join(process.cwd(), GEMINI_DIR), { recursive: true });
       await fs.writeFile(TEST_LOG_FILE_PATH, JSON.stringify(existingLogs));
-      const newLogger = new Logger();
+      const newLogger = new Logger('a-new-session');
       await newLogger.initialize();
       expect(newLogger['messageId']).toBe(0);
       newLogger.close();
@@ -203,7 +205,7 @@ describe('Logger', () => {
       const consoleDebugSpy = vi
         .spyOn(console, 'debug')
         .mockImplementation(() => {});
-      const newLogger = new Logger();
+      const newLogger = new Logger(testSessionId);
       await newLogger.initialize();
       expect(consoleDebugSpy).toHaveBeenCalledWith(
         expect.stringContaining('Invalid JSON in log file'),
@@ -232,7 +234,7 @@ describe('Logger', () => {
       const consoleDebugSpy = vi
         .spyOn(console, 'debug')
         .mockImplementation(() => {});
-      const newLogger = new Logger();
+      const newLogger = new Logger(testSessionId);
       await newLogger.initialize();
       expect(consoleDebugSpy).toHaveBeenCalledWith(
         `Log file at ${TEST_LOG_FILE_PATH} is not a valid JSON array. Starting with empty logs.`,
@@ -259,7 +261,7 @@ describe('Logger', () => {
       const logsFromFile = await readLogFile();
       expect(logsFromFile.length).toBe(1);
       expect(logsFromFile[0]).toMatchObject({
-        sessionId: logger['sessionId'],
+        sessionId: testSessionId,
         messageId: 0,
         type: MessageSenderType.USER,
         message: 'Hello, world!',
@@ -283,7 +285,8 @@ describe('Logger', () => {
     });
 
     it('should handle logger not initialized', async () => {
-      const uninitializedLogger = new Logger();
+      const uninitializedLogger = new Logger(testSessionId);
+      uninitializedLogger.close(); // Ensure it's treated as uninitialized
       const consoleDebugSpy = vi
         .spyOn(console, 'debug')
         .mockImplementation(() => {});
@@ -296,15 +299,13 @@ describe('Logger', () => {
     });
 
     it('should simulate concurrent writes from different logger instances to the same file', async () => {
-      const logger1 = new Logger(); // logger1
-      vi.setSystemTime(new Date('2025-01-01T13:00:00.000Z'));
+      const concurrentSessionId = 'concurrent-session';
+      const logger1 = new Logger(concurrentSessionId);
       await logger1.initialize();
-      const s1 = logger1['sessionId'];
 
-      const logger2 = new Logger(); // logger2, will share same session if time is same
-      vi.setSystemTime(new Date('2025-01-01T13:00:00.000Z'));
+      const logger2 = new Logger(concurrentSessionId);
       await logger2.initialize();
-      expect(logger2['sessionId']).toEqual(s1);
+      expect(logger2['sessionId']).toEqual(logger1['sessionId']);
 
       // Log from logger1
       await logger1.logMessage(MessageSenderType.USER, 'L1M1'); // L1 internal msgId becomes 1, writes {s1, 0}
@@ -361,43 +362,34 @@ describe('Logger', () => {
   });
 
   describe('getPreviousUserMessages', () => {
-    it('should retrieve user messages, sorted newest first by session, then timestamp, then messageId', async () => {
-      const loggerSort = new Logger();
-      vi.setSystemTime(new Date('2025-01-01T10:00:00.000Z'));
+    it('should retrieve all user messages from logs, sorted newest first', async () => {
+      // This test now verifies that messages from different sessions are included
+      // and sorted correctly by timestamp, as the session-based sorting was removed.
+      const loggerSort = new Logger('session-1');
       await loggerSort.initialize();
-      const s1 = loggerSort['sessionId']!;
       await loggerSort.logMessage(MessageSenderType.USER, 'S1M0_ts100000'); // msgId 0
-      vi.advanceTimersByTime(10);
-      await loggerSort.logMessage(MessageSenderType.USER, 'S1M1_ts100010'); // msgId 1
-      loggerSort.close(); // Close to ensure next initialize starts a new session if time changed
-
-      vi.setSystemTime(new Date('2025-01-01T11:00:00.000Z'));
-      await loggerSort.initialize(); // Re-initialize for a new session
-      const s2 = loggerSort['sessionId']!;
-      expect(s2).not.toEqual(s1);
-      await loggerSort.logMessage(MessageSenderType.USER, 'S2M0_ts110000'); // msgId 0 for s2
-      vi.advanceTimersByTime(10);
+      vi.advanceTimersByTime(1000);
+      await loggerSort.logMessage(MessageSenderType.USER, 'S1M1_ts101000'); // msgId 1
+      vi.advanceTimersByTime(1000);
+      await loggerSort.logMessage(MessageSenderType.USER, 'S2M0_ts102000'); // msgId 0 for s2
+      vi.advanceTimersByTime(1000);
       await loggerSort.logMessage(
         'model' as MessageSenderType,
-        'S2_Model_ts110010',
+        'S2_Model_ts103000',
       );
-      vi.advanceTimersByTime(10);
-      await loggerSort.logMessage(MessageSenderType.USER, 'S2M1_ts110020'); // msgId 1 for s2
+      vi.advanceTimersByTime(1000);
+      await loggerSort.logMessage(MessageSenderType.USER, 'S2M1_ts104000'); // msgId 1 for s2
       loggerSort.close();
 
-      // To test the sorting thoroughly, especially the session part, we'll read the file
-      // as if it was written by multiple sessions and then initialize a new logger to load them.
-      const combinedLogs = await readLogFile();
-      const finalLogger = new Logger();
-      // Manually set its internal logs to simulate loading from a file with mixed sessions
-      finalLogger['logs'] = combinedLogs;
-      finalLogger['initialized'] = true; // Mark as initialized to allow getPreviousUserMessages to run
+      // A new logger will load all previous logs regardless of session
+      const finalLogger = new Logger('final-session');
+      await finalLogger.initialize();
 
       const messages = await finalLogger.getPreviousUserMessages();
       expect(messages).toEqual([
-        'S2M1_ts110020',
-        'S2M0_ts110000',
-        'S1M1_ts100010',
+        'S2M1_ts104000',
+        'S2M0_ts102000',
+        'S1M1_ts101000',
         'S1M0_ts100000',
       ]);
       finalLogger.close();
@@ -410,7 +402,8 @@ describe('Logger', () => {
     });
 
     it('should return empty array if logger not initialized', async () => {
-      const uninitializedLogger = new Logger();
+      const uninitializedLogger = new Logger(testSessionId);
+      uninitializedLogger.close();
       const messages = await uninitializedLogger.getPreviousUserMessages();
       expect(messages).toEqual([]);
       uninitializedLogger.close();
@@ -443,7 +436,8 @@ describe('Logger', () => {
     });
 
     it('should not throw if logger is not initialized', async () => {
-      const uninitializedLogger = new Logger();
+      const uninitializedLogger = new Logger(testSessionId);
+      uninitializedLogger.close();
       const consoleErrorSpy = vi
         .spyOn(console, 'error')
         .mockImplementation(() => {});
@@ -521,7 +515,8 @@ describe('Logger', () => {
     });
 
     it('should return an empty array if logger is not initialized', async () => {
-      const uninitializedLogger = new Logger();
+      const uninitializedLogger = new Logger(testSessionId);
+      uninitializedLogger.close();
       const consoleErrorSpy = vi
         .spyOn(console, 'error')
         .mockImplementation(() => {});
diff --git a/packages/core/src/core/logger.ts b/packages/core/src/core/logger.ts
index ee4ce98c..dd57860b 100644
--- a/packages/core/src/core/logger.ts
+++ b/packages/core/src/core/logger.ts
@@ -17,7 +17,7 @@ export enum MessageSenderType {
 }
 
 export interface LogEntry {
-  sessionId: number;
+  sessionId: string;
   messageId: number;
   timestamp: string;
   type: MessageSenderType;
@@ -28,12 +28,14 @@ export class Logger {
   private geminiDir: string | undefined;
   private logFilePath: string | undefined;
   private checkpointFilePath: string | undefined;
-  private sessionId: number | undefined;
+  private sessionId: string | undefined;
   private messageId = 0; // Instance-specific counter for the next messageId
   private initialized = false;
   private logs: LogEntry[] = []; // In-memory cache, ideally reflects the last known state of the file
 
-  constructor() {}
+  constructor(sessionId: string) {
+    this.sessionId = sessionId;
+  }
 
   private async _readLogFile(): Promise<LogEntry[]> {
     if (!this.logFilePath) {
@@ -51,7 +53,7 @@ export class Logger {
       }
       return parsedLogs.filter(
         (entry) =>
-          typeof entry.sessionId === 'number' &&
+          typeof entry.sessionId === 'string' &&
           typeof entry.messageId === 'number' &&
           typeof entry.timestamp === 'string' &&
           typeof entry.type === 'string' &&
@@ -93,7 +95,6 @@ export class Logger {
     if (this.initialized) {
       return;
     }
-    this.sessionId = Math.floor(Date.now() / 1000);
     this.geminiDir = path.resolve(process.cwd(), GEMINI_DIR);
     this.logFilePath = path.join(this.geminiDir, LOG_FILE_NAME);
     this.checkpointFilePath = path.join(this.geminiDir, CHECKPOINT_FILE_NAME);
@@ -195,11 +196,9 @@ export class Logger {
     return this.logs
       .filter((entry) => entry.type === MessageSenderType.USER)
       .sort((a, b) => {
-        if (b.sessionId !== a.sessionId) return b.sessionId - a.sessionId;
         const dateA = new Date(a.timestamp).getTime();
         const dateB = new Date(b.timestamp).getTime();
-        if (dateB !== dateA) return dateB - dateA;
-        return b.messageId - a.messageId;
+        return dateB - dateA;
       })
       .map((entry) => entry.message);
   }
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 376ad218..60959281 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -51,3 +51,4 @@ export * from './tools/mcp-tool.js';
 
 // Export telemetry functions
 export * from './telemetry/index.js';
+export { sessionId } from './utils/session.js';
diff --git a/packages/core/src/telemetry/constants.ts b/packages/core/src/telemetry/constants.ts
index ac8f7490..97bdaa8c 100644
--- a/packages/core/src/telemetry/constants.ts
+++ b/packages/core/src/telemetry/constants.ts
@@ -4,10 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { randomUUID } from 'crypto';
-
 export const SERVICE_NAME = 'gemini-cli';
-export const sessionId = randomUUID();
 
 export const EVENT_USER_PROMPT = 'gemini_code.user_prompt';
 export const EVENT_TOOL_CALL = 'gemini_code.tool_call';
diff --git a/packages/core/src/telemetry/index.ts b/packages/core/src/telemetry/index.ts
index 7b2ab0e7..cbb7b4d2 100644
--- a/packages/core/src/telemetry/index.ts
+++ b/packages/core/src/telemetry/index.ts
@@ -28,4 +28,3 @@ export {
 } from './types.js';
 export { SpanStatusCode, ValueType } from '@opentelemetry/api';
 export { SemanticAttributes } from '@opentelemetry/semantic-conventions';
-export { sessionId } from './constants.js';
diff --git a/packages/core/src/telemetry/sdk.ts b/packages/core/src/telemetry/sdk.ts
index 8cd20b7b..704661c5 100644
--- a/packages/core/src/telemetry/sdk.ts
+++ b/packages/core/src/telemetry/sdk.ts
@@ -26,7 +26,7 @@ import {
 } from '@opentelemetry/sdk-metrics';
 import { HttpInstrumentation } from '@opentelemetry/instrumentation-http';
 import { Config } from '../config/config.js';
-import { SERVICE_NAME, sessionId } from './constants.js';
+import { SERVICE_NAME } from './constants.js';
 import { initializeMetrics } from './metrics.js';
 import { logCliConfiguration } from './loggers.js';
 
@@ -68,7 +68,7 @@ export function initializeTelemetry(config: Config): void {
   const resource = new Resource({
     [SemanticResourceAttributes.SERVICE_NAME]: SERVICE_NAME,
     [SemanticResourceAttributes.SERVICE_VERSION]: process.version,
-    'session.id': sessionId,
+    'session.id': config.getSessionId(),
   });
 
   const otlpEndpoint = config.getTelemetryOtlpEndpoint();
diff --git a/packages/core/src/tools/tool-registry.test.ts b/packages/core/src/tools/tool-registry.test.ts
index 4ff8b897..f4cedcd4 100644
--- a/packages/core/src/tools/tool-registry.test.ts
+++ b/packages/core/src/tools/tool-registry.test.ts
@@ -136,6 +136,7 @@ const baseConfigParams: ConfigParameters = {
   userMemory: '',
   geminiMdFileCount: 0,
   approvalMode: ApprovalMode.DEFAULT,
+  sessionId: 'test-session-id',
 };
 
 describe('ToolRegistry', () => {
diff --git a/packages/core/src/utils/nextSpeakerChecker.test.ts b/packages/core/src/utils/nextSpeakerChecker.test.ts
index 2514c99d..a19045d1 100644
--- a/packages/core/src/utils/nextSpeakerChecker.test.ts
+++ b/packages/core/src/utils/nextSpeakerChecker.test.ts
@@ -71,6 +71,7 @@ describe('checkNextSpeaker', () => {
     chatInstance = new GeminiChat(
       mockModelsInstance, // This is the instance returned by mockGoogleGenAIInstance.getGenerativeModel
       'gemini-pro', // model name
+      'test-session-id',
       {},
       [], // initial history
     );
diff --git a/packages/core/src/utils/session.ts b/packages/core/src/utils/session.ts
new file mode 100644
index 00000000..57726019
--- /dev/null
+++ b/packages/core/src/utils/session.ts
@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { randomUUID } from 'crypto';
+
+export const sessionId = randomUUID();