fix(models): prevent /models crash from non-string saved model values (#691)

* fix(models): guard GitHub default model setting against non-string values

* test(models): avoid brittle GitHub default assertion in model guard test

src/utils/model/model.github.test.ts

@@ -0,0 +1,57 @@
+import { afterEach, beforeEach, expect, test } from 'bun:test'
+
+import { saveGlobalConfig } from '../config.js'
+import { getDefaultMainLoopModelSetting, getUserSpecifiedModelSetting } from './model.js'
+
+const env = {
+  CLAUDE_CODE_USE_GITHUB: process.env.CLAUDE_CODE_USE_GITHUB,
+  CLAUDE_CODE_USE_OPENAI: process.env.CLAUDE_CODE_USE_OPENAI,
+  CLAUDE_CODE_USE_GEMINI: process.env.CLAUDE_CODE_USE_GEMINI,
+  CLAUDE_CODE_USE_BEDROCK: process.env.CLAUDE_CODE_USE_BEDROCK,
+  CLAUDE_CODE_USE_VERTEX: process.env.CLAUDE_CODE_USE_VERTEX,
+  CLAUDE_CODE_USE_FOUNDRY: process.env.CLAUDE_CODE_USE_FOUNDRY,
+  OPENAI_MODEL: process.env.OPENAI_MODEL,
+}
+
+beforeEach(() => {
+  process.env.CLAUDE_CODE_USE_GITHUB = '1'
+  delete process.env.CLAUDE_CODE_USE_OPENAI
+  delete process.env.CLAUDE_CODE_USE_GEMINI
+  delete process.env.CLAUDE_CODE_USE_BEDROCK
+  delete process.env.CLAUDE_CODE_USE_VERTEX
+  delete process.env.CLAUDE_CODE_USE_FOUNDRY
+  delete process.env.OPENAI_MODEL
+  saveGlobalConfig(current => ({
+    ...current,
+    model: ({ bad: true } as unknown) as string,
+  }))
+})
+
+afterEach(() => {
+  process.env.CLAUDE_CODE_USE_GITHUB = env.CLAUDE_CODE_USE_GITHUB
+  process.env.CLAUDE_CODE_USE_OPENAI = env.CLAUDE_CODE_USE_OPENAI
+  process.env.CLAUDE_CODE_USE_GEMINI = env.CLAUDE_CODE_USE_GEMINI
+  process.env.CLAUDE_CODE_USE_BEDROCK = env.CLAUDE_CODE_USE_BEDROCK
+  process.env.CLAUDE_CODE_USE_VERTEX = env.CLAUDE_CODE_USE_VERTEX
+  process.env.CLAUDE_CODE_USE_FOUNDRY = env.CLAUDE_CODE_USE_FOUNDRY
+  process.env.OPENAI_MODEL = env.OPENAI_MODEL
+  saveGlobalConfig(current => ({
+    ...current,
+    model: undefined,
+  }))
+})
+
+test('github default model setting ignores non-string saved model', () => {
+  const model = getDefaultMainLoopModelSetting()
+  expect(typeof model).toBe('string')
+  expect(model).not.toBe('[object Object]')
+  expect(model.length).toBeGreaterThan(0)
+})
+
+test('user specified model ignores non-string saved model', () => {
+  const model = getUserSpecifiedModelSetting()
+  if (model !== undefined && model !== null) {
+    expect(typeof model).toBe('string')
+    expect(model).not.toBe('[object Object]')
+  }
+})