diff --git a/src/__tests__/local-agent-tool-calling.test.ts b/src/__tests__/local-agent-tool-calling.test.ts
index e3353ab..a5791d2 100644
--- a/src/__tests__/local-agent-tool-calling.test.ts
+++ b/src/__tests__/local-agent-tool-calling.test.ts
@@ -134,3 +134,23 @@ describe('local-model (HTTP) backbone surfaces toolCalls — the keyless-path fi
     expect(sys.content).toContain('nmap_scan');
   });
 });
+
+describe('xai provider (Grok Build) — routes to xAI OpenAI-compatible API with the key', () => {
+  const origFetch = global.fetch;
+  afterEach(() => { global.fetch = origFetch; });
+  it('hits api.x.ai with the bearer key and surfaces native tool_calls', async () => {
+    const spy = vi.fn(async (_url: string, _init: { headers: Record<string, string> }) => ({
+      ok: true,
+      json: async () => ({
+        model: 'grok-build-0.1',
+        choices: [{ message: { content: '', tool_calls: [{ id: 'c1', function: { name: 'nmap_scan', arguments: '{"target":"x"}' } }] }, finish_reason: 'tool_calls' }],
+      }),
+    } as unknown as Response));
+    global.fetch = spy as unknown as typeof fetch;
+    const be = new LLMBackbone({ provider: 'xai', model: 'grok-build-0.1', apiKey: 'xai-test-key-1234567890', baseUrl: 'https://api.x.ai/v1' } as never);
+    const res = await be.chatWithTools([{ role: 'user', content: 'scan' }], TOOLS as never);
+    expect(res.toolCalls?.[0]?.name).toBe('nmap_scan');
+    expect(spy.mock.calls[0][0]).toContain('api.x.ai');
+    expect((spy.mock.calls[0][1] as { headers: Record<string, string> }).headers.Authorization).toContain('xai-test-key');
+  });
+});
diff --git a/src/config/index.ts b/src/config/index.ts
index 9189860..94f6d35 100755
--- a/src/config/index.ts
+++ b/src/config/index.ts
@@ -22,6 +22,7 @@ export interface TempestSettings {
     venice?: string;
     anthropic?: string;
     openai?: string;
+    xai?: string;
   };
 
   // Default LLM settings
@@ -54,6 +55,12 @@ export interface TempestSettings {
     defaultModel: string;
   };
 
+  // xAI — Grok Build / Grok models (OpenAI-compatible API)
+  xai: {
+    baseUrl: string;
+    defaultModel: string;
+  };
+
   // Codex CLI/account subscription backend
   codex: {
     command: string;
@@ -112,6 +119,11 @@ const DEFAULT_SETTINGS: TempestSettings = {
     defaultModel: 'gpt-4-turbo-preview',
   },
 
+  xai: {
+    baseUrl: 'https://api.x.ai/v1',
+    defaultModel: 'grok-build-0.1',
+  },
+
   codex: {
     command: 'codex',
     defaultModel: 'codex-default',
@@ -389,6 +401,16 @@ export const AVAILABLE_MODELS: Record<LLMProvider, ModelInfo[]> = {
       capabilities: ['testing'],
     },
   ],
+  xai: [
+    {
+      id: 'grok-build-0.1',
+      name: 'Grok Build (grok-build-0.1, 256K)',
+      provider: 'xAI',
+      contextWindow: 256000,
+      maxOutput: 8192,
+      capabilities: ['reasoning', 'code', 'analysis', 'agents', 'tools'],
+    },
+  ],
   local: [
     {
       id: 'local-model',
@@ -486,6 +508,7 @@ class ConfigManager {
     // Environment variables (including values loaded from ~/.t3mp3st/.env above)
     // are intentionally process-local. getApiKey() already gives env vars highest
     // priority, so do not persist them into Conf's apiKeys store as a side effect.
+    // (XAI_API_KEY / Grok Build follows the same safe path — see the envVarMap in getApiKey.)
     this.envLoaded = true;
   }
 
@@ -513,7 +536,7 @@ class ConfigManager {
   /**
    * Set an API key for a provider
    */
-  setApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai', key: string): void {
+  setApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai', key: string): void {
     const apiKeys = this.config.get('apiKeys');
     apiKeys[provider] = key;
     this.config.set('apiKeys', apiKeys);
@@ -522,13 +545,14 @@ class ConfigManager {
   /**
    * Get an API key for a provider
    */
-  getApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai'): string | undefined {
+  getApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai'): string | undefined {
     // First check environment variables (highest priority)
     const envVarMap = {
       openrouter: 'OPENROUTER_API_KEY',
       venice: 'VENICE_API_KEY',
       anthropic: 'ANTHROPIC_API_KEY',
       openai: 'OPENAI_API_KEY',
+      xai: 'XAI_API_KEY',
     };
 
     // Force a fully UNCONFIGURED server (no key from env OR the saved store) — used by
@@ -547,7 +571,7 @@ class ConfigManager {
   /**
    * Check if a provider has a valid API key configured
    */
-  hasApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai'): boolean {
+  hasApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai'): boolean {
     const key = this.getApiKey(provider);
     return !!key && key.length > 10;
   }
@@ -555,7 +579,7 @@ class ConfigManager {
   /**
    * Remove an API key
    */
-  removeApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai'): void {
+  removeApiKey(provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai'): void {
     const apiKeys = this.config.get('apiKeys');
     delete apiKeys[provider];
     this.config.set('apiKeys', apiKeys);
@@ -571,6 +595,7 @@ class ConfigManager {
     if (this.hasApiKey('venice')) providers.push('venice');
     if (this.hasApiKey('anthropic')) providers.push('anthropic');
     if (this.hasApiKey('openai')) providers.push('openai');
+    if (this.hasApiKey('xai')) providers.push('xai');
 
     // Codex uses the local Codex CLI/account auth instead of API-key storage.
     providers.push('codex');
@@ -612,6 +637,12 @@ class ConfigManager {
         baseUrl = this.config.get('openai').baseUrl;
         actualModel = model || this.config.get('openai').defaultModel;
         break;
+      case 'xai':
+        // Grok Build / Grok — xAI's OpenAI-compatible API (native tool-calling).
+        apiKey = this.getApiKey('xai');
+        baseUrl = this.config.get('xai').baseUrl;
+        actualModel = model || this.config.get('xai').defaultModel;
+        break;
       case 'codex':
         actualModel = model || this.config.get('codex').defaultModel;
         break;
@@ -657,7 +688,7 @@ class ConfigManager {
     const flag = (process.env.TEMPEST_MODEL_FALLBACK || '').trim().toLowerCase();
     if (!flag || ['0', 'false', 'off', 'no'].includes(flag)) return [];
     const chain: FallbackEntry[] = [];
-    const add = (p: 'openrouter' | 'venice' | 'anthropic' | 'openai') => {
+    const add = (p: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai') => {
       if (p === primary || !this.hasApiKey(p)) return;
       chain.push({
         provider: p,
@@ -670,6 +701,7 @@ class ConfigManager {
     add('venice');
     add('anthropic');
     add('openai');
+    add('xai');
     return chain;
   }
 
@@ -787,8 +819,8 @@ OPENAI_API_KEY=
 export const config = new ConfigManager();
 
 // Helper functions for quick access
-export const getApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai') => config.getApiKey(provider);
-export const setApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai', key: string) => config.setApiKey(provider, key);
-export const hasApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai') => config.hasApiKey(provider);
+export const getApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai') => config.getApiKey(provider);
+export const setApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai', key: string) => config.setApiKey(provider, key);
+export const hasApiKey = (provider: 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai') => config.hasApiKey(provider);
 export const getLLMConfig = (provider?: LLMProvider, model?: string) => config.getLLMConfig(provider, model);
 export const getConfiguredProviders = () => config.getConfiguredProviders();
diff --git a/src/llm/index.ts b/src/llm/index.ts
index 3404255..3e781fc 100755
--- a/src/llm/index.ts
+++ b/src/llm/index.ts
@@ -1201,6 +1201,8 @@ export class LLMBackbone extends EventEmitter<LLMEvents> {
         return new AnthropicAdapter(config);
       case 'openai':
         return new OpenAIAdapter(config);
+      case 'xai':
+        return new OpenAIAdapter(config); // xAI (Grok Build / grok-*) is OpenAI-compatible
       case 'codex':
         return new CodexAdapter(config);
       case 'mock':
diff --git a/src/types/index.ts b/src/types/index.ts
index 2e6d638..e8cfdea 100755
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -6,7 +6,7 @@
 // LLM CONFIGURATION
 // =============================================================================
 
-export type LLMProvider = 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'codex' | 'mock' | 'local' | 'local-agent';
+export type LLMProvider = 'openrouter' | 'venice' | 'anthropic' | 'openai' | 'xai' | 'codex' | 'mock' | 'local' | 'local-agent';
 
 export interface LLMConfig {
   provider: LLMProvider;