From 49c26b48018258a9329f0fdee3d3d7b34fa511e6 Mon Sep 17 00:00:00 2001
From: Jerop Kipruto <jerop@google.com>
Date: Mon, 26 Jan 2026 18:45:24 -0500
Subject: [PATCH] feat(plan): refresh system prompt when approval mode changes
 (Shift+Tab) (#17585)

---
 packages/core/src/commands/memory.ts    |  2 +-
 packages/core/src/config/config.test.ts | 33 +++++++++++++++++++++++++
 packages/core/src/config/config.ts      | 17 +++++++++----
 packages/core/src/core/client.test.ts   |  4 +--
 packages/core/src/core/client.ts        |  2 +-
 5 files changed, 49 insertions(+), 9 deletions(-)

diff --git a/packages/core/src/commands/memory.ts b/packages/core/src/commands/memory.ts
index 6065cf0dab..a1c6573b4f 100644
--- a/packages/core/src/commands/memory.ts
+++ b/packages/core/src/commands/memory.ts
@@ -59,7 +59,7 @@ export async function refreshMemory(
     fileCount = result.fileCount;
   }
 
-  await config.updateSystemInstructionIfInitialized();
+  config.updateSystemInstructionIfInitialized();
   let content: string;
 
   if (memoryContent.length > 0) {
diff --git a/packages/core/src/config/config.test.ts b/packages/core/src/config/config.test.ts
index 97b2ab67bb..c5062c6d64 100644
--- a/packages/core/src/config/config.test.ts
+++ b/packages/core/src/config/config.test.ts
@@ -1269,6 +1269,39 @@ describe('setApprovalMode with folder trust', () => {
     expect(() => config.setApprovalMode(ApprovalMode.DEFAULT)).not.toThrow();
   });
 
+  it('should update system instruction when entering Plan mode', () => {
+    const config = new Config(baseParams);
+    vi.spyOn(config, 'isTrustedFolder').mockReturnValue(true);
+    const updateSpy = vi.spyOn(config, 'updateSystemInstructionIfInitialized');
+
+    config.setApprovalMode(ApprovalMode.PLAN);
+
+    expect(updateSpy).toHaveBeenCalled();
+  });
+
+  it('should update system instruction when leaving Plan mode', () => {
+    const config = new Config({
+      ...baseParams,
+      approvalMode: ApprovalMode.PLAN,
+    });
+    vi.spyOn(config, 'isTrustedFolder').mockReturnValue(true);
+    const updateSpy = vi.spyOn(config, 'updateSystemInstructionIfInitialized');
+
+    config.setApprovalMode(ApprovalMode.DEFAULT);
+
+    expect(updateSpy).toHaveBeenCalled();
+  });
+
+  it('should not update system instruction when switching between non-Plan modes', () => {
+    const config = new Config(baseParams);
+    vi.spyOn(config, 'isTrustedFolder').mockReturnValue(true);
+    const updateSpy = vi.spyOn(config, 'updateSystemInstructionIfInitialized');
+
+    config.setApprovalMode(ApprovalMode.AUTO_EDIT);
+
+    expect(updateSpy).not.toHaveBeenCalled();
+  });
+
   describe('registerCoreTools', () => {
     beforeEach(() => {
       vi.clearAllMocks();
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 6da474cbcf..b4be2cbdfc 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -1341,7 +1341,7 @@ export class Config {
     }
     if (this.geminiClient?.isInitialized()) {
       await this.geminiClient.setTools();
-      await this.geminiClient.updateSystemInstruction();
+      this.geminiClient.updateSystemInstruction();
     }
   }
 
@@ -1409,6 +1409,13 @@ export class Config {
     }
 
     this.policyEngine.setApprovalMode(mode);
+
+    const isPlanModeTransition =
+      currentMode !== mode &&
+      (currentMode === ApprovalMode.PLAN || mode === ApprovalMode.PLAN);
+    if (isPlanModeTransition) {
+      this.updateSystemInstructionIfInitialized();
+    }
   }
 
   /**
@@ -1491,10 +1498,10 @@ export class Config {
    * Updates the system instruction with the latest user memory.
    * Whenever the user memory (GEMINI.md files) is updated.
    */
-  async updateSystemInstructionIfInitialized(): Promise<void> {
+  updateSystemInstructionIfInitialized(): void {
     const geminiClient = this.getGeminiClient();
     if (geminiClient?.isInitialized()) {
-      await geminiClient.updateSystemInstruction();
+      geminiClient.updateSystemInstruction();
     }
   }
 
@@ -1803,7 +1810,7 @@ export class Config {
     }
 
     // Notify the client that system instructions might need updating
-    await this.updateSystemInstructionIfInitialized();
+    this.updateSystemInstructionIfInitialized();
   }
 
   /**
@@ -2142,7 +2149,7 @@ export class Config {
     const client = this.getGeminiClient();
     if (client?.isInitialized()) {
       await client.setTools();
-      await client.updateSystemInstruction();
+      client.updateSystemInstruction();
     } else {
       debugLogger.debug(
         '[Config] GeminiClient not initialized; skipping live prompt/tool refresh.',
diff --git a/packages/core/src/core/client.test.ts b/packages/core/src/core/client.test.ts
index 49d71ce1a9..ba30a63327 100644
--- a/packages/core/src/core/client.test.ts
+++ b/packages/core/src/core/client.test.ts
@@ -1842,7 +1842,7 @@ ${JSON.stringify(
       const { getCoreSystemPrompt } = await import('./prompts.js');
       const mockGetCoreSystemPrompt = vi.mocked(getCoreSystemPrompt);
 
-      await client.updateSystemInstruction();
+      client.updateSystemInstruction();
 
       expect(mockGetCoreSystemPrompt).toHaveBeenCalledWith(
         mockConfig,
@@ -1857,7 +1857,7 @@ ${JSON.stringify(
       const { getCoreSystemPrompt } = await import('./prompts.js');
       const mockGetCoreSystemPrompt = vi.mocked(getCoreSystemPrompt);
 
-      await client.updateSystemInstruction();
+      client.updateSystemInstruction();
 
       expect(mockGetCoreSystemPrompt).toHaveBeenCalledWith(
         mockConfig,
diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index 2adb5d8bad..d80b8b4002 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -300,7 +300,7 @@ export class GeminiClient {
     });
   }
 
-  async updateSystemInstruction(): Promise<void> {
+  updateSystemInstruction(): void {
     if (!this.isInitialized()) {
       return;
     }