feat(plan): support automatic model switching for Plan Mode (#20240)

packages/core/src/config/config.test.ts

@@ -2533,6 +2533,29 @@ describe('Config Quota & Preview Model Access', () => {
       expect(config.isPlanEnabled()).toBe(false);
     });
   });
+
+  describe('getPlanModeRoutingEnabled', () => {
+    it('should default to true when not provided', async () => {
+      const config = new Config(baseParams);
+      expect(await config.getPlanModeRoutingEnabled()).toBe(true);
+    });
+
+    it('should return true when explicitly enabled in planSettings', async () => {
+      const config = new Config({
+        ...baseParams,
+        planSettings: { modelRouting: true },
+      });
+      expect(await config.getPlanModeRoutingEnabled()).toBe(true);
+    });
+
+    it('should return false when explicitly disabled in planSettings', async () => {
+      const config = new Config({
+        ...baseParams,
+        planSettings: { modelRouting: false },
+      });
+      expect(await config.getPlanModeRoutingEnabled()).toBe(false);
+    });
+  });
 });
 
 describe('Config JIT Initialization', () => {

packages/core/src/config/config.ts

@@ -153,6 +153,7 @@ export interface SummarizeToolOutputSettings {
 
 export interface PlanSettings {
   directory?: string;
+  modelRouting?: boolean;
 }
 
 export interface TelemetrySettings {
@@ -734,6 +735,7 @@ export class Config {
   private readonly experimentalJitContext: boolean;
   private readonly disableLLMCorrection: boolean;
   private readonly planEnabled: boolean;
+  private readonly planModeRoutingEnabled: boolean;
   private readonly modelSteering: boolean;
   private contextManager?: ContextManager;
   private terminalBackground: string | undefined = undefined;
@@ -823,6 +825,7 @@ export class Config {
     this.agents = params.agents ?? {};
     this.disableLLMCorrection = params.disableLLMCorrection ?? true;
     this.planEnabled = params.plan ?? false;
+    this.planModeRoutingEnabled = params.planSettings?.modelRouting ?? true;
     this.enableEventDrivenScheduler = params.enableEventDrivenScheduler ?? true;
     this.skillsSupport = params.skillsSupport ?? true;
     this.disabledSkills = params.disabledSkills ?? [];
@@ -2318,6 +2321,10 @@ export class Config {
     return this.experiments?.flags[ExperimentFlags.USER_CACHING]?.boolValue;
   }
 
+  async getPlanModeRoutingEnabled(): Promise<boolean> {
+    return this.planModeRoutingEnabled;
+  }
+
   async getNumericalRoutingEnabled(): Promise<boolean> {
     await this.ensureExperimentsLoaded();