feat: add Grok (xAI) API adapter with custom model mapping (claude-code-best#152)

Add xAI Grok as a new API provider. Reuses OpenAI-compatible message/tool
converters and stream adapter with Grok-specific client and model mapping.

Default model mapping:
  opus   → grok-4.20-reasoning
  sonnet → grok-3-mini-fast
  haiku  → grok-3-mini-fast

Users can customize mapping via:
  - GROK_MODEL env var (override all)
  - GROK_MODEL_MAP env var (JSON family map, e.g. {"opus":"grok-4"})
  - GROK_DEFAULT_{FAMILY}_MODEL env vars

Activation: CLAUDE_CODE_USE_GROK=1 or modelType: "grok" in settings.json
Also integrates with /provider command for runtime switching.

Author: uk0

src/commands/provider.ts

@@ -15,6 +15,8 @@ function getEnvVarForProvider(provider: string): string {
       return 'CLAUDE_CODE_USE_FOUNDRY'
     case 'gemini':
       return 'CLAUDE_CODE_USE_GEMINI'
+    case 'grok':
+      return 'CLAUDE_CODE_USE_GROK'
     default:
       throw new Error(`Unknown provider: ${provider}`)
   }
@@ -48,6 +50,7 @@ const call: LocalCommandCall = async (args, context) => {
     delete process.env.CLAUDE_CODE_USE_FOUNDRY
     delete process.env.CLAUDE_CODE_USE_OPENAI
     delete process.env.CLAUDE_CODE_USE_GEMINI
+    delete process.env.CLAUDE_CODE_USE_GROK
     return {
       type: 'text',
       value: 'API provider cleared (will use environment variables).',
@@ -59,6 +62,7 @@ const call: LocalCommandCall = async (args, context) => {
     'anthropic',
     'openai',
     'gemini',
+    'grok',
     'bedrock',
     'vertex',
     'foundry',
@@ -87,6 +91,19 @@ const call: LocalCommandCall = async (args, context) => {
     }
   }
 
+  // Check env vars when switching to grok (including settings.env)
+  if (arg === 'grok') {
+    const mergedEnv = getMergedEnv()
+    const hasKey = !!(mergedEnv.GROK_API_KEY || mergedEnv.XAI_API_KEY)
+    if (!hasKey) {
+      updateSettingsForSource('userSettings', { modelType: 'grok' })
+      return {
+        type: 'text',
+        value: `Switched to Grok provider.\nWarning: Missing env var: GROK_API_KEY (or XAI_API_KEY)\nConfigure it via settings.json env or set manually.`,
+      }
+    }
+  }
+
   // Check env vars when switching to gemini (including settings.env)
   if (arg === 'gemini') {
     const mergedEnv = getMergedEnv()
@@ -104,13 +121,14 @@ const call: LocalCommandCall = async (args, context) => {
   // Handle different provider types
   // - 'anthropic', 'openai', 'gemini' are stored in settings.json (persistent)
   // - 'bedrock', 'vertex', 'foundry' are env-only (do NOT touch settings.json)
-  if (arg === 'anthropic' || arg === 'openai' || arg === 'gemini') {
+  if (arg === 'anthropic' || arg === 'openai' || arg === 'gemini' || arg === 'grok') {
     // Clear any cloud provider env vars to avoid conflicts
     delete process.env.CLAUDE_CODE_USE_BEDROCK
     delete process.env.CLAUDE_CODE_USE_VERTEX
     delete process.env.CLAUDE_CODE_USE_FOUNDRY
     delete process.env.CLAUDE_CODE_USE_OPENAI
     delete process.env.CLAUDE_CODE_USE_GEMINI
+    delete process.env.CLAUDE_CODE_USE_GROK
     // Update settings.json
     updateSettingsForSource('userSettings', { modelType: arg })
     // Ensure settings.env gets applied to process.env
@@ -122,6 +140,7 @@ const call: LocalCommandCall = async (args, context) => {
     delete process.env.OPENAI_API_KEY
     delete process.env.OPENAI_BASE_URL
     delete process.env.CLAUDE_CODE_USE_GEMINI
+    delete process.env.CLAUDE_CODE_USE_GROK
     process.env[getEnvVarForProvider(arg)] = '1'
     // Do not modify settings.json - cloud providers controlled solely by env vars
     applyConfigEnvironmentVariables()
@@ -136,9 +155,9 @@ const provider = {
   type: 'local',
   name: 'provider',
   description:
-    'Switch API provider (anthropic/openai/gemini/bedrock/vertex/foundry)',
+    'Switch API provider (anthropic/openai/gemini/grok/bedrock/vertex/foundry)',
   aliases: ['api'],
-  argumentHint: '[anthropic|openai|gemini|bedrock|vertex|foundry|unset]',
+  argumentHint: '[anthropic|openai|gemini|grok|bedrock|vertex|foundry|unset]',
   supportsNonInteractive: true,
   load: () => Promise.resolve({ call }),
 } satisfies Command

src/services/api/claude.ts

@@ -1350,6 +1350,12 @@ async function* queryModel(
     return
   }
 
+  if (getAPIProvider() === 'grok') {
+    const { queryModelGrok } = await import('./grok/index.js')
+    yield* queryModelGrok(messagesForAPI, systemPrompt, filteredTools, signal, options)
+    return
+  }
+
   // Instrumentation: Track message count after normalization
   logEvent('tengu_api_after_normalize', {
     postNormalizedMessageCount: messagesForAPI.length,

src/services/api/grok/__tests__/client.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, test, beforeEach, afterEach } from 'bun:test'
+import { getGrokClient, clearGrokClientCache } from '../client.js'
+
+describe('getGrokClient', () => {
+  const originalEnv = { ...process.env }
+
+  beforeEach(() => {
+    clearGrokClientCache()
+    process.env.GROK_API_KEY = 'test-key'
+    delete process.env.GROK_BASE_URL
+  })
+
+  afterEach(() => {
+    clearGrokClientCache()
+    process.env = { ...originalEnv }
+  })
+
+  test('creates client with default base URL', () => {
+    const client = getGrokClient()
+    expect(client).toBeDefined()
+    expect(client.baseURL).toBe('https://api.x.ai/v1')
+  })
+
+  test('uses GROK_BASE_URL when set', () => {
+    process.env.GROK_BASE_URL = 'https://custom.grok.api/v1'
+    clearGrokClientCache()
+    const client = getGrokClient()
+    expect(client.baseURL).toBe('https://custom.grok.api/v1')
+  })
+
+  test('returns cached client on second call', () => {
+    const client1 = getGrokClient()
+    const client2 = getGrokClient()
+    expect(client1).toBe(client2)
+  })
+
+  test('clearGrokClientCache resets cache', () => {
+    const client1 = getGrokClient()
+    clearGrokClientCache()
+    process.env.GROK_BASE_URL = 'https://other.api/v1'
+    const client2 = getGrokClient()
+    expect(client1).not.toBe(client2)
+  })
+})

src/services/api/grok/__tests__/modelMapping.test.ts

@@ -0,0 +1,67 @@
+import { describe, expect, test, beforeEach, afterEach } from 'bun:test'
+import { resolveGrokModel } from '../modelMapping.js'
+
+describe('resolveGrokModel', () => {
+  const originalEnv = { ...process.env }
+
+  beforeEach(() => {
+    delete process.env.GROK_MODEL
+    delete process.env.GROK_MODEL_MAP
+    delete process.env.GROK_DEFAULT_SONNET_MODEL
+    delete process.env.GROK_DEFAULT_OPUS_MODEL
+    delete process.env.GROK_DEFAULT_HAIKU_MODEL
+    delete process.env.ANTHROPIC_DEFAULT_SONNET_MODEL
+    delete process.env.ANTHROPIC_DEFAULT_OPUS_MODEL
+    delete process.env.ANTHROPIC_DEFAULT_HAIKU_MODEL
+  })
+
+  afterEach(() => {
+    process.env = { ...originalEnv }
+  })
+
+  test('GROK_MODEL env var takes highest priority', () => {
+    process.env.GROK_MODEL = 'grok-custom'
+    expect(resolveGrokModel('claude-sonnet-4-6')).toBe('grok-custom')
+  })
+
+  test('maps opus models to grok-4.20-reasoning', () => {
+    expect(resolveGrokModel('claude-opus-4-6')).toBe('grok-4.20-reasoning')
+  })
+
+  test('maps sonnet models to grok-3-mini-fast', () => {
+    expect(resolveGrokModel('claude-sonnet-4-6')).toBe('grok-3-mini-fast')
+  })
+
+  test('maps haiku models to grok-3-mini-fast', () => {
+    expect(resolveGrokModel('claude-haiku-4-5-20251001')).toBe('grok-3-mini-fast')
+  })
+
+  test('GROK_MODEL_MAP overrides family mapping', () => {
+    process.env.GROK_MODEL_MAP = '{"opus":"grok-4","sonnet":"grok-3","haiku":"grok-mini"}'
+    expect(resolveGrokModel('claude-opus-4-6')).toBe('grok-4')
+    expect(resolveGrokModel('claude-sonnet-4-6')).toBe('grok-3')
+    expect(resolveGrokModel('claude-haiku-4-5-20251001')).toBe('grok-mini')
+  })
+
+  test('GROK_MODEL_MAP ignores invalid JSON', () => {
+    process.env.GROK_MODEL_MAP = 'not-json'
+    expect(resolveGrokModel('claude-opus-4-6')).toBe('grok-4.20-reasoning')
+  })
+
+  test('GROK_DEFAULT_{FAMILY}_MODEL overrides default map', () => {
+    process.env.GROK_DEFAULT_OPUS_MODEL = 'grok-2-latest'
+    expect(resolveGrokModel('claude-opus-4-6')).toBe('grok-2-latest')
+  })
+
+  test('passes through unknown model names', () => {
+    expect(resolveGrokModel('some-unknown-model')).toBe('some-unknown-model')
+  })
+
+  test('strips [1m] suffix before lookup', () => {
+    expect(resolveGrokModel('claude-sonnet-4-6[1m]')).toBe('grok-3-mini-fast')
+  })
+
+  test('falls back to family default for unlisted model', () => {
+    expect(resolveGrokModel('claude-opus-99-20300101')).toBe('grok-4.20-reasoning')
+  })
+})

src/services/api/grok/client.ts

@@ -0,0 +1,44 @@
+import OpenAI from 'openai'
+import { getProxyFetchOptions } from 'src/utils/proxy.js'
+
+/**
+ * Environment variables:
+ *
+ * GROK_API_KEY (or XAI_API_KEY): Required. API key for the xAI Grok endpoint.
+ * GROK_BASE_URL: Optional. Defaults to https://api.x.ai/v1.
+ */
+
+const DEFAULT_BASE_URL = 'https://api.x.ai/v1'
+
+let cachedClient: OpenAI | null = null
+
+export function getGrokClient(options?: {
+  maxRetries?: number
+  fetchOverride?: typeof fetch
+  source?: string
+}): OpenAI {
+  if (cachedClient) return cachedClient
+
+  const apiKey = process.env.GROK_API_KEY || process.env.XAI_API_KEY || ''
+  const baseURL = process.env.GROK_BASE_URL || DEFAULT_BASE_URL
+
+  const client = new OpenAI({
+    apiKey,
+    baseURL,
+    maxRetries: options?.maxRetries ?? 0,
+    timeout: parseInt(process.env.API_TIMEOUT_MS || String(600 * 1000), 10),
+    dangerouslyAllowBrowser: true,
+    fetchOptions: getProxyFetchOptions({ forAnthropicAPI: false }) as RequestInit,
+    ...(options?.fetchOverride && { fetch: options.fetchOverride }),
+  })
+
+  if (!options?.fetchOverride) {
+    cachedClient = client
+  }
+
+  return client
+}
+
+export function clearGrokClientCache(): void {
+  cachedClient = null
+}