From d09c19c0c5a25be6f0dce68e9fe57ef8e61b2e16 Mon Sep 17 00:00:00 2001
From: Fu Yuchen <fuyuchen0904@163.com>
Date: Tue, 28 Apr 2026 09:22:17 +0800
Subject: [PATCH] fix(core,cli): stop stripping reasoning on switch and resume
 paths (#3682)

---
 packages/cli/src/ui/hooks/slashCommandProcessor.test.ts | 4 ++--
 packages/cli/src/ui/hooks/slashCommandProcessor.ts      | 1 -
 packages/core/src/config/config.test.ts                 | 4 ++--
 packages/core/src/config/config.ts                      | 8 +++-----
 4 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
index 0893c8e28..7b963cfd2 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
@@ -501,7 +501,7 @@ describe('useSlashCommandProcessor', () => {
       );
     });
 
-    it('should strip thoughts when handling "load_history" action', async () => {
+    it('should preserve thoughts when handling "load_history" action', async () => {
       const mockClient = {
         setHistory: vi.fn(),
         stripThoughtsFromHistory: vi.fn(),
@@ -531,7 +531,7 @@ describe('useSlashCommandProcessor', () => {
       });
 
       expect(mockClient.setHistory).toHaveBeenCalledTimes(1);
-      expect(mockClient.stripThoughtsFromHistory).toHaveBeenCalledWith();
+      expect(mockClient.stripThoughtsFromHistory).not.toHaveBeenCalled();
     });
 
     it('should handle a "quit" action', async () => {
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
index fb1281f16..f9d685b78 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
@@ -647,7 +647,6 @@ export const useSlashCommandProcessor = (
                   }
                 case 'load_history': {
                   config?.getGeminiClient()?.setHistory(result.clientHistory);
-                  config?.getGeminiClient()?.stripThoughtsFromHistory();
                   fullCommandContext.ui.clear();
                   result.history.forEach((item, index) => {
                     fullCommandContext.ui.addItem(item, index);
diff --git a/packages/core/src/config/config.test.ts b/packages/core/src/config/config.test.ts
index c3ce32493..873c403d8 100644
--- a/packages/core/src/config/config.test.ts
+++ b/packages/core/src/config/config.test.ts
@@ -531,7 +531,7 @@ describe('Server Config (config.ts)', () => {
       expect(vi.mocked(createContentGenerator)).toHaveBeenCalledTimes(1);
     });
 
-    it('should strip thoughts from history on model switch (#3304)', async () => {
+    it('should preserve thoughts from history on model switch', async () => {
       const config = new Config(baseParams);
 
       const mockContentConfig: ContentGeneratorConfig = {
@@ -567,7 +567,7 @@ describe('Server Config (config.ts)', () => {
 
       await config.switchModel(AuthType.QWEN_OAUTH, 'coder-model');
 
-      expect(stripSpy).toHaveBeenCalledTimes(1);
+      expect(stripSpy).not.toHaveBeenCalled();
     });
   });
 
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 27a97d205..a3b498b99 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -1423,11 +1423,9 @@ export class Config {
       return;
     }
 
-    // Strip thinking blocks from conversation history on model switch.
-    // reasoning_content is a non-standard field that causes strict
-    // OpenAI-compatible providers to reject requests with 422 errors
-    // when thought parts from a previous model leak into the payload (#3304).
-    this.geminiClient.stripThoughtsFromHistory();
+    // Keep full history (including thought parts) on model switch.
+    // Some OpenAI-compatible reasoning models (e.g. DeepSeek) require
+    // reasoning_content to be preserved across turns.
 
     // Hot update path: only supported for qwen-oauth.
     // For other auth types we always refresh to recreate the ContentGenerator.