diff --git a/packages/core/index.ts b/packages/core/index.ts
index c6b74ba366..c78ddfc4d6 100644
--- a/packages/core/index.ts
+++ b/packages/core/index.ts
@@ -16,7 +16,7 @@ export {
   DEFAULT_TRUNCATE_TOOL_OUTPUT_LINES,
   DEFAULT_TRUNCATE_TOOL_OUTPUT_THRESHOLD,
 } from './src/config/config.js';
-export { getIdeInfo } from './src/ide/detect-ide.js';
+export { detectIdeFromEnv, getIdeInfo } from './src/ide/detect-ide.js';
 export { logIdeConnection } from './src/telemetry/loggers.js';
 export {
   IdeConnectionEvent,
diff --git a/packages/vscode-ide-companion/src/extension.test.ts b/packages/vscode-ide-companion/src/extension.test.ts
index 8377c01e97..8e28adc17a 100644
--- a/packages/vscode-ide-companion/src/extension.test.ts
+++ b/packages/vscode-ide-companion/src/extension.test.ts
@@ -7,6 +7,15 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 import * as vscode from 'vscode';
 import { activate } from './extension.js';
+import { DetectedIde, detectIdeFromEnv } from '@google/gemini-cli-core';
+
+vi.mock('@google/gemini-cli-core', async () => {
+  const actual = await vi.importActual('@google/gemini-cli-core');
+  return {
+    ...actual,
+    detectIdeFromEnv: vi.fn(() => DetectedIde.VSCode),
+  };
+});
 
 vi.mock('vscode', () => ({
   window: {
@@ -187,6 +196,23 @@ describe('activate', () => {
       expect(showInformationMessageMock).not.toHaveBeenCalled();
     });
 
+    it.each([
+      {
+        ide: DetectedIde.CloudShell,
+      },
+      { ide: DetectedIde.FirebaseStudio },
+    ])('does not show the notification for $ide', async ({ ide }) => {
+      vi.mocked(detectIdeFromEnv).mockReturnValue(ide);
+      vi.mocked(context.globalState.get).mockReturnValue(undefined);
+      const showInformationMessageMock = vi.mocked(
+        vscode.window.showInformationMessage,
+      );
+
+      await activate(context);
+
+      expect(showInformationMessageMock).not.toHaveBeenCalled();
+    });
+
     it('should not show an update notification if the version is older', async () => {
       vi.spyOn(global, 'fetch').mockResolvedValue({
         ok: true,
diff --git a/packages/vscode-ide-companion/src/extension.ts b/packages/vscode-ide-companion/src/extension.ts
index 66020cb94f..b7dcb97bfc 100644
--- a/packages/vscode-ide-companion/src/extension.ts
+++ b/packages/vscode-ide-companion/src/extension.ts
@@ -9,11 +9,22 @@ import { IDEServer } from './ide-server.js';
 import semver from 'semver';
 import { DiffContentProvider, DiffManager } from './diff-manager.js';
 import { createLogger } from './utils/logger.js';
+import { detectIdeFromEnv, DetectedIde } from '@google/gemini-cli-core';
 
 const CLI_IDE_COMPANION_IDENTIFIER = 'Google.gemini-cli-vscode-ide-companion';
 const INFO_MESSAGE_SHOWN_KEY = 'geminiCliInfoMessageShown';
 export const DIFF_SCHEME = 'gemini-diff';
 
+/**
+ * IDE environments where the installation greeting is hidden.  In these
+ * environments we either are pre-installed and the installation message is
+ * confusing or we just want to be quiet.
+ */
+const HIDE_INSTALLATION_GREETING_IDES: ReadonlySet<DetectedIde> = new Set([
+  DetectedIde.FirebaseStudio,
+  DetectedIde.CloudShell,
+]);
+
 let ideServer: IDEServer;
 let logger: vscode.OutputChannel;
 
@@ -133,7 +144,10 @@ export async function activate(context: vscode.ExtensionContext) {
     log(`Failed to start IDE server: ${message}`);
   }
 
-  if (!context.globalState.get(INFO_MESSAGE_SHOWN_KEY)) {
+  const infoMessageEnabled =
+    !HIDE_INSTALLATION_GREETING_IDES.has(detectIdeFromEnv());
+
+  if (!context.globalState.get(INFO_MESSAGE_SHOWN_KEY) && infoMessageEnabled) {
     void vscode.window.showInformationMessage(
       'Gemini CLI Companion extension successfully installed.',
     );