Support COPILOT_MODEL=auto in AWF validation and api-proxy resolution

containers/api-proxy/model-resolver.js

@@ -270,6 +270,18 @@ function resolveModel(requestedModel, aliases, availableModels, currentProvider,
   const key = requestedModel.toLowerCase();
   const fallbackConfig = normalizeFallbackConfig(modelFallbackConfig);
 
+  if (key === 'auto') {
+    log.push('[model-resolver] special pass-through: "auto"');
+    return {
+      resolvedModel: requestedModel,
+      candidates: [requestedModel],
+      log,
+      fallback: fallbackConfig.enabled
+        ? { activated: false, selection_method: 'middle_power_median', reason: 'direct_match' }
+        : undefined,
+    };
+  }
+
   // Loop detection
   if (chain.includes(key)) {
     log.push(`[model-resolver] loop detected: "${requestedModel}" already in chain [${chain.join(' → ')}]`);

containers/api-proxy/model-resolver.test.js

@@ -127,6 +127,13 @@ describe('resolveModel', () => {
     expect(result.resolvedModel).toBe('gpt-4o');
   });
 
+  it('should treat the Copilot auto model as a pass-through', () => {
+    const result = resolveModel('auto', aliases, availableModels, 'copilot');
+    expect(result).not.toBeNull();
+    expect(result.resolvedModel).toBe('auto');
+    expect(result.fallback.activated).toBe(false);
+  });
+
   it('should be case-insensitive for alias lookup', () => {
     const result = resolveModel('SONNET', aliases, availableModels, 'copilot');
     expect(result).not.toBeNull();
@@ -358,6 +365,12 @@ describe('rewriteModelInBody', () => {
     expect(result).toBeNull(); // No rewrite needed
   });
 
+  it('should not rewrite the Copilot auto model', () => {
+    const body = Buffer.from(JSON.stringify({ model: 'auto', messages: [] }));
+    const result = rewriteModelInBody(body, 'copilot', aliases, availableModels);
+    expect(result).toBeNull();
+  });
+
   it('should return null for non-JSON body', () => {
     const body = Buffer.from('not json');
     const result = rewriteModelInBody(body, 'copilot', aliases, availableModels);

containers/api-proxy/server.startup-model-validation.test.js

@@ -67,6 +67,16 @@ describe('validateRequestedModel', () => {
     }));
   });
 
+  it('treats the Copilot auto model as available without requiring it in provider model lists', () => {
+    process.env.AWF_REQUESTED_MODEL = 'auto';
+    cachedModels.copilot = ['gpt-4o', 'gpt-4o-mini'];
+    validateRequestedModel();
+    expect(logRequest).toHaveBeenCalledWith('info', 'model_validation', expect.objectContaining({
+      requested_model: 'auto',
+      resolved_via: 'direct',
+    }));
+  });
+
   it('searches across multiple providers', () => {
     process.env.AWF_REQUESTED_MODEL = 'claude-sonnet-4-5';
     cachedModels.copilot = ['gpt-4o'];

src/commands/validators/config-assembly-model-detection.test.ts

@@ -225,6 +225,27 @@ describe('config-assembly', () => {
       );
     });
 
+    it('should allow COPILOT_MODEL=auto', () => {
+      mockBuildConfigOnce({
+        copilotGithubToken: 'github_pat_testtoken',
+      });
+
+      const agentOptions = createMinimalAgentOptions();
+      agentOptions.additionalEnv = { COPILOT_MODEL: 'auto' };
+
+      expect(() => {
+        assembleAndValidateConfig(
+          {},
+          'echo test',
+          createMinimalLogAndLimits(),
+          createMinimalNetworkOptions(),
+          agentOptions,
+        );
+      }).not.toThrow();
+
+      expect(logger.error).not.toHaveBeenCalled();
+    });
+
     it('should allow COPILOT_MODEL that matches a runtime alias key and resolves to a valid concrete model', () => {
       mockBuildConfigOnce({
         copilotGithubToken: 'github_pat_testtoken',

src/copilot-model.test.ts

@@ -16,6 +16,11 @@ describe('validateCopilotModel', () => {
     expect(result).toEqual({ valid: true, resolvedModel: 'gpt-5.3-codex' });
   });
 
+  it('accepts the Copilot auto model', () => {
+    const result = validateCopilotModel(' auto ');
+    expect(result).toEqual({ valid: true, resolvedModel: 'auto' });
+  });
+
   it.each([
     'gpt-4.5',
     'gpt-5.1',

src/copilot-model.ts

@@ -42,6 +42,7 @@ const RETIRED_COPILOT_MODEL_ALIASES: Record<string, string> = {
  * explicitly listed as a non-CLI model in the test's exclusion set).
  */
 const SUPPORTED_COPILOT_MODELS = new Set([
+  'auto',
   'gpt-4',
   'gpt-4.1',
   'gpt-4.5',