diff --git a/src/cliproxy/ai-providers/__tests__/extended-context-config.test.ts b/src/cliproxy/ai-providers/__tests__/extended-context-config.test.ts
index 9d241a3a..33e84ed2 100644
--- a/src/cliproxy/ai-providers/__tests__/extended-context-config.test.ts
+++ b/src/cliproxy/ai-providers/__tests__/extended-context-config.test.ts
@@ -168,6 +168,26 @@ describe('applyExtendedContextConfig', () => {
     expect(env.ANTHROPIC_MODEL).toBe('gemini-2.5-pro(high)[1m]');
   });
 
+  it('preserves a saved [1m] preference for supported Claude models in auto mode', () => {
+    const env: NodeJS.ProcessEnv = {
+      ANTHROPIC_MODEL: 'claude-sonnet-4-5-20250929[1m]',
+    };
+
+    applyExtendedContextConfig(env, 'claude', undefined);
+
+    expect(env.ANTHROPIC_MODEL).toBe('claude-sonnet-4-5-20250929[1m]');
+  });
+
+  it('strips a stale [1m] preference from unsupported native Gemini models', () => {
+    const env: NodeJS.ProcessEnv = {
+      ANTHROPIC_MODEL: 'gemini-2.5-flash[1m]',
+    };
+
+    applyExtendedContextConfig(env, 'gemini', undefined);
+
+    expect(env.ANTHROPIC_MODEL).toBe('gemini-2.5-flash');
+  });
+
   it('handles empty env vars gracefully', () => {
     const env: NodeJS.ProcessEnv = {};
     applyExtendedContextConfig(env, 'gemini', undefined);
diff --git a/src/cliproxy/config/extended-context-config.ts b/src/cliproxy/config/extended-context-config.ts
index 1b55b784..98115888 100644
--- a/src/cliproxy/config/extended-context-config.ts
+++ b/src/cliproxy/config/extended-context-config.ts
@@ -105,7 +105,7 @@ export function applyExtendedContextConfig(
     if (isNativeGeminiModel(modelId)) {
       envVars[key] = supportsExtendedContext(provider, modelId)
         ? applyExtendedContextSuffixShared(value)
-        : value;
+        : stripExtendedContextSuffix(value);
       continue;
     }