Do not fallback for manual models (#84)

* Update display name for alias model

* fix tests

packages/core/src/availability/policyCatalog.ts

@@ -66,6 +66,10 @@ export function getModelPolicyChain(
   return cloneChain(DEFAULT_CHAIN);
 }
 
+export function createSingleModelChain(model: string): ModelPolicyChain {
+  return [definePolicy({ model, isLastResort: true })];
+}
+
 /**
  * Provides a default policy scaffold for models not present in the catalog.
  */

packages/core/src/availability/policyHelpers.test.ts

@@ -25,7 +25,7 @@ const createMockConfig = (overrides: Partial<Config> = {}): Config =>
 
 describe('policyHelpers', () => {
   describe('resolvePolicyChain', () => {
-    it('inserts the active model when missing from the catalog', () => {
+    it('returns a single-model chain for a custom model', () => {
       const config = createMockConfig({
         getModel: () => 'custom-model',
       });
@@ -53,6 +53,25 @@ describe('policyHelpers', () => {
       expect(chain[0]?.model).toBe('gemini-2.5-pro');
       expect(chain[1]?.model).toBe('gemini-2.5-flash');
     });
+
+    it('starts chain from preferredModel when model is "auto"', () => {
+      const config = createMockConfig({
+        getModel: () => DEFAULT_GEMINI_MODEL_AUTO,
+      });
+      const chain = resolvePolicyChain(config, 'gemini-2.5-flash');
+      expect(chain).toHaveLength(1);
+      expect(chain[0]?.model).toBe('gemini-2.5-flash');
+    });
+
+    it('wraps around the chain when wrapsAround is true', () => {
+      const config = createMockConfig({
+        getModel: () => DEFAULT_GEMINI_MODEL_AUTO,
+      });
+      const chain = resolvePolicyChain(config, 'gemini-2.5-flash', true);
+      expect(chain).toHaveLength(2);
+      expect(chain[0]?.model).toBe('gemini-2.5-flash');
+      expect(chain[1]?.model).toBe('gemini-2.5-pro');
+    });
   });
 
   describe('buildFallbackPolicyContext', () => {
@@ -67,6 +86,17 @@ describe('policyHelpers', () => {
       expect(context.candidates.map((p) => p.model)).toEqual(['c']);
     });
 
+    it('wraps around when building fallback context if wrapsAround is true', () => {
+      const chain = [
+        createDefaultPolicy('a'),
+        createDefaultPolicy('b'),
+        createDefaultPolicy('c'),
+      ];
+      const context = buildFallbackPolicyContext(chain, 'b', true);
+      expect(context.failedPolicy?.model).toBe('b');
+      expect(context.candidates.map((p) => p.model)).toEqual(['c', 'a']);
+    });
+
     it('returns full chain when model is not in policy list', () => {
       const chain = [createDefaultPolicy('a'), createDefaultPolicy('b')];
       const context = buildFallbackPolicyContext(chain, 'x');

packages/core/src/availability/policyHelpers.ts

@@ -13,8 +13,17 @@ import type {
   ModelPolicyChain,
   RetryAvailabilityContext,
 } from './modelPolicy.js';
-import { createDefaultPolicy, getModelPolicyChain } from './policyCatalog.js';
-import { DEFAULT_GEMINI_MODEL, resolveModel } from '../config/models.js';
+import {
+  createDefaultPolicy,
+  createSingleModelChain,
+  getModelPolicyChain,
+} from './policyCatalog.js';
+import {
+  DEFAULT_GEMINI_MODEL,
+  DEFAULT_GEMINI_MODEL_AUTO,
+  PREVIEW_GEMINI_MODEL_AUTO,
+  resolveModel,
+} from '../config/models.js';
 import type { ModelSelectionResult } from './modelAvailabilityService.js';
 
 /**
@@ -31,15 +40,20 @@ export function resolvePolicyChain(
   const modelFromConfig =
     preferredModel ?? config.getActiveModel?.() ?? config.getModel();
 
-  const isPreviewRequest =
-    modelFromConfig.includes('gemini-3') ||
-    modelFromConfig.includes('preview') ||
-    modelFromConfig === 'fiercefalcon';
+  let chain;
+
+  if (
+    config.getModel() === PREVIEW_GEMINI_MODEL_AUTO ||
+    config.getModel() === DEFAULT_GEMINI_MODEL_AUTO
+  ) {
+    chain = getModelPolicyChain({
+      previewEnabled: config.getModel() === PREVIEW_GEMINI_MODEL_AUTO,
+      userTier: config.getUserTier(),
+    });
+  } else {
+    chain = createSingleModelChain(modelFromConfig);
+  }
 
-  const chain = getModelPolicyChain({
-    previewEnabled: isPreviewRequest,
-    userTier: config.getUserTier(),
-  });
   const activeModel = resolveModel(modelFromConfig);
 
   const activeIndex = chain.findIndex((policy) => policy.model === activeModel);