feat(core): support custom reasoning models by default (#19227)

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

@@ -10,6 +10,8 @@ import {
   resolveClassifierModel,
   isGemini3Model,
   isGemini2Model,
+  isCustomModel,
+  supportsModernFeatures,
   isAutoModel,
   getDisplayString,
   DEFAULT_GEMINI_MODEL,
@@ -25,6 +27,50 @@ import {
   DEFAULT_GEMINI_MODEL_AUTO,
 } from './models.js';
 
+describe('isCustomModel', () => {
+  it('should return true for models not starting with gemini-', () => {
+    expect(isCustomModel('testing')).toBe(true);
+    expect(isCustomModel('gpt-4')).toBe(true);
+    expect(isCustomModel('claude-3')).toBe(true);
+  });
+
+  it('should return false for Gemini models', () => {
+    expect(isCustomModel('gemini-1.5-pro')).toBe(false);
+    expect(isCustomModel('gemini-2.0-flash')).toBe(false);
+    expect(isCustomModel('gemini-3-pro-preview')).toBe(false);
+  });
+
+  it('should return false for aliases that resolve to Gemini models', () => {
+    expect(isCustomModel(GEMINI_MODEL_ALIAS_AUTO)).toBe(false);
+    expect(isCustomModel(GEMINI_MODEL_ALIAS_PRO)).toBe(false);
+  });
+});
+
+describe('supportsModernFeatures', () => {
+  it('should return true for Gemini 3 models', () => {
+    expect(supportsModernFeatures('gemini-3-pro-preview')).toBe(true);
+    expect(supportsModernFeatures('gemini-3-flash-preview')).toBe(true);
+  });
+
+  it('should return true for custom models', () => {
+    expect(supportsModernFeatures('testing')).toBe(true);
+    expect(supportsModernFeatures('some-custom-model')).toBe(true);
+  });
+
+  it('should return false for older Gemini models', () => {
+    expect(supportsModernFeatures('gemini-2.5-pro')).toBe(false);
+    expect(supportsModernFeatures('gemini-2.5-flash')).toBe(false);
+    expect(supportsModernFeatures('gemini-2.0-flash')).toBe(false);
+    expect(supportsModernFeatures('gemini-1.5-pro')).toBe(false);
+    expect(supportsModernFeatures('gemini-1.0-pro')).toBe(false);
+  });
+
+  it('should return true for modern aliases', () => {
+    expect(supportsModernFeatures(GEMINI_MODEL_ALIAS_PRO)).toBe(true);
+    expect(supportsModernFeatures(GEMINI_MODEL_ALIAS_AUTO)).toBe(true);
+  });
+});
+
 describe('isGemini3Model', () => {
   it('should return true for gemini-3 models', () => {
     expect(isGemini3Model('gemini-3-pro-preview')).toBe(true);

packages/core/src/config/models.ts

@@ -141,6 +141,29 @@ export function isGemini2Model(model: string): boolean {
   return /^gemini-2(\.|$)/.test(model);
 }
 
+/**
+ * Checks if the model is a "custom" model (not Gemini branded).
+ *
+ * @param model The model name to check.
+ * @returns True if the model is not a Gemini branded model.
+ */
+export function isCustomModel(model: string): boolean {
+  const resolved = resolveModel(model);
+  return !resolved.startsWith('gemini-');
+}
+
+/**
+ * Checks if the model should be treated as a modern model.
+ * This includes Gemini 3 models and any custom models.
+ *
+ * @param model The model name to check.
+ * @returns True if the model supports modern features like thoughts.
+ */
+export function supportsModernFeatures(model: string): boolean {
+  if (isGemini3Model(model)) return true;
+  return isCustomModel(model);
+}
+
 /**
  * Checks if the model is an auto model.
  *