From e58fca68ceb33f8540826fe973a5d8d0665c0145 Mon Sep 17 00:00:00 2001
From: Sehoon Shon <sshon@google.com>
Date: Wed, 14 Jan 2026 19:07:51 -0500
Subject: [PATCH] feat(config): add 'auto' alias for default model selection
 (#16661)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
 packages/cli/src/config/config.test.ts | 14 ++++++++++++++
 packages/cli/src/config/config.ts      | 12 +++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/packages/cli/src/config/config.test.ts b/packages/cli/src/config/config.test.ts
index d3040aabf0..78a4847fd2 100644
--- a/packages/cli/src/config/config.test.ts
+++ b/packages/cli/src/config/config.test.ts
@@ -1313,6 +1313,20 @@ describe('loadCliConfig model selection', () => {
 
     expect(config.getModel()).toBe('gemini-2.5-flash-preview');
   });
+
+  it('selects the default auto model if provided via auto alias', async () => {
+    process.argv = ['node', 'script.js', '--model', 'auto'];
+    const argv = await parseArguments({} as Settings);
+    const config = await loadCliConfig(
+      {
+        // No model provided via settings.
+      },
+      'test-session',
+      argv,
+    );
+
+    expect(config.getModel()).toBe('auto-gemini-2.5');
+  });
 });
 
 describe('loadCliConfig folderTrust', () => {
diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index 40601eea1c..fc21e43fce 100755
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -36,6 +36,7 @@ import {
   type HookDefinition,
   type HookEventName,
   type OutputFormat,
+  GEMINI_MODEL_ALIAS_AUTO,
 } from '@google/gemini-cli-core';
 import type { Settings } from './settings.js';
 import { saveModelChange, loadSettings } from './settings.js';
@@ -617,12 +618,13 @@ export async function loadCliConfig(
   const defaultModel = settings.general?.previewFeatures
     ? PREVIEW_GEMINI_MODEL_AUTO
     : DEFAULT_GEMINI_MODEL_AUTO;
-  const resolvedModel: string =
-    argv.model ||
-    process.env['GEMINI_MODEL'] ||
-    settings.model?.name ||
-    defaultModel;
+  const specifiedModel =
+    argv.model || process.env['GEMINI_MODEL'] || settings.model?.name;
 
+  const resolvedModel =
+    specifiedModel === GEMINI_MODEL_ALIAS_AUTO
+      ? defaultModel
+      : specifiedModel || defaultModel;
   const sandboxConfig = await loadSandboxConfig(settings, argv);
   const screenReader =
     argv.screenReader !== undefined