feat: Add LiteLLM AI Gateway support

src/__tests__/config.test.ts

@@ -29,9 +29,9 @@ describe("config", () => {
     expect(getConfig().ai?.gateway).toBe("openrouter");
   });
 
-  it("configure sets ai.gateway to opencodezen", () => {
-    configure({ ai: { gateway: "opencodezen" } });
-    expect(getConfig().ai?.gateway).toBe("opencodezen");
+  it("configure sets ai.gateway to litellm", () => {
+    configure({ ai: { gateway: "litellm" } });
+    expect(getConfig().ai?.gateway).toBe("litellm");
   });
 
   it("configure merges without overwriting other keys", () => {

src/__tests__/models.test.ts

@@ -0,0 +1,50 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { resolveModel } from "../models";
+import { configure, resetConfig } from "../config";
+import { ConfigurationError } from "../errors";
+
+describe("models", () => {
+  const originalEnv = process.env;
+
+  beforeEach(() => {
+    vi.resetModules();
+    process.env = { ...originalEnv };
+    resetConfig();
+  });
+
+  afterEach(() => {
+    process.env = originalEnv;
+  });
+
+  it("throws ConfigurationError if litellm gateway is used but LITELLM_BASE_URL is missing", () => {
+    configure({ ai: { gateway: "litellm" } });
+    delete process.env.LITELLM_BASE_URL;
+
+    expect(() => resolveModel("google/gemini-3-flash")).toThrow(ConfigurationError);
+    expect(() => resolveModel("google/gemini-3-flash")).toThrow(/LITELLM_BASE_URL isn't set/);
+  });
+
+  it("resolves model using litellm gateway when LITELLM_BASE_URL is provided", () => {
+    configure({ ai: { gateway: "litellm" } });
+    process.env.LITELLM_BASE_URL = "http://localhost:4000/v1";
+    // It should not throw and return a wrapped language model
+    const model = resolveModel("google/gemini-3-flash");
+    expect(model).toBeDefined();
+    // Vercel AI SDK language models are objects with an execute property among others
+    expect(typeof model).toBe("object");
+  });
+
+  it("accepts model IDs when routing via litellm gateway", () => {
+    configure({ ai: { gateway: "litellm" } });
+    process.env.LITELLM_BASE_URL = "http://localhost:4000/v1";
+
+    // We can't easily inspect the internal modelId of the wrapped model in a unit test
+    // without mocking the openai package, but we can verify it doesn't crash
+    const model = resolveModel("google/gemini-3-flash");
+    expect(model).toBeDefined();
+
+    // And standard names should work too
+    const bedrockModel = resolveModel("bedrock/claude-3-sonnet");
+    expect(bedrockModel).toBeDefined();
+  });
+});

src/config.ts

@@ -11,7 +11,7 @@ export type EmailProvider = {
   extractContent: (params: { email: string; prompt: string }) => Promise<string>;
 };
 
-export type AIGateway = "vercel" | "openrouter" | "opencodezen" | "cloudflare" | "none";
+export type AIGateway = "vercel" | "openrouter" | "cloudflare" | "litellm" | "none";
 
 /**
  * Execution mode for browser automation.

src/models.ts

@@ -20,12 +20,13 @@ let _openrouter: ReturnType<typeof createOpenRouter> | null = null;
 let _opencodezen: ReturnType<typeof createOpenAI> | null = null;
 let _cloudflareGoogle: ReturnType<typeof createGoogleGenerativeAI> | null = null;
 let _cloudflareAnthropic: ReturnType<typeof createAnthropic> | null = null;
+let _litellm: ReturnType<typeof createOpenAI> | null = null;
 
 function getGoogleProvider() {
   if (!_google) {
     if (!process.env.GOOGLE_GENERATIVE_AI_API_KEY) {
       throw new ConfigurationError(
-        "GOOGLE_GENERATIVE_AI_API_KEY isn't set. Add it to your environment (for example: export GOOGLE_GENERATIVE_AI_API_KEY=your_key), or use a gateway: configure({ ai: { gateway: 'vercel' } }) with AI_GATEWAY_API_KEY, configure({ ai: { gateway: 'openrouter' } }) with OPENROUTER_API_KEY, or configure({ ai: { gateway: 'cloudflare' } }) with CLOUDFLARE_ACCOUNT_ID, CLOUDFLARE_AI_GATEWAY, GOOGLE_GENERATIVE_AI_API_KEY, and CLOUDFLARE_AI_GATEWAY_API_KEY. See .env.example for reference.",
+        "GOOGLE_GENERATIVE_AI_API_KEY isn't set. Add it to your environment (for example: export GOOGLE_GENERATIVE_AI_API_KEY=your_key), or use a gateway: configure({ ai: { gateway: 'vercel' } }) with AI_GATEWAY_API_KEY, configure({ ai: { gateway: 'openrouter' } }) with OPENROUTER_API_KEY, configure({ ai: { gateway: 'litellm' } }) with LITELLM_BASE_URL, or configure({ ai: { gateway: 'cloudflare' } }) with CLOUDFLARE_ACCOUNT_ID, CLOUDFLARE_AI_GATEWAY, GOOGLE_GENERATIVE_AI_API_KEY, and CLOUDFLARE_AI_GATEWAY_API_KEY. See .env.example for reference.",
       );
     }
     _google = createGoogleGenerativeAI({
@@ -39,7 +40,7 @@ function getAnthropicProvider() {
   if (!_anthropic) {
     if (!process.env.ANTHROPIC_API_KEY) {
       throw new ConfigurationError(
-        "ANTHROPIC_API_KEY isn't set. Add it to your environment (for example: export ANTHROPIC_API_KEY=your_key), or use a gateway: configure({ ai: { gateway: 'vercel' } }) with AI_GATEWAY_API_KEY, configure({ ai: { gateway: 'openrouter' } }) with OPENROUTER_API_KEY, or configure({ ai: { gateway: 'cloudflare' } }) with CLOUDFLARE_ACCOUNT_ID, CLOUDFLARE_AI_GATEWAY, ANTHROPIC_API_KEY, and CLOUDFLARE_AI_GATEWAY_API_KEY. See .env.example for reference.",
+        "ANTHROPIC_API_KEY isn't set. Add it to your environment (for example: export ANTHROPIC_API_KEY=your_key), or use a gateway: configure({ ai: { gateway: 'vercel' } }) with AI_GATEWAY_API_KEY, configure({ ai: { gateway: 'openrouter' } }) with OPENROUTER_API_KEY, configure({ ai: { gateway: 'litellm' } }) with LITELLM_BASE_URL, or configure({ ai: { gateway: 'cloudflare' } }) with CLOUDFLARE_ACCOUNT_ID, CLOUDFLARE_AI_GATEWAY, ANTHROPIC_API_KEY, and CLOUDFLARE_AI_GATEWAY_API_KEY. See .env.example for reference.",
       );
     }
     _anthropic = createAnthropic({
@@ -77,19 +78,19 @@ function getOpenRouterProvider() {
   return _openrouter;
 }
 
-function getOpenCodeZenProvider() {
-  if (!_opencodezen) {
-    if (!process.env.OPENCODEZEN_API_KEY) {
+function getLiteLLMProvider() {
+  if (!_litellm) {
+    if (!process.env.LITELLM_BASE_URL) {
       throw new ConfigurationError(
-        "OPENCODEZEN_API_KEY isn't set. Add it to your environment (for example: export OPENCODEZEN_API_KEY=your_key). See .env.example for reference.",
+        "LITELLM_BASE_URL isn't set. To use the LiteLLM gateway, add LITELLM_BASE_URL to your environment (e.g. export LITELLM_BASE_URL=http://localhost:4000/v1). You may also need to set LITELLM_API_KEY.",
       );
     }
-    _opencodezen = createOpenAI({
-      baseURL: "https://opencode.ai/zen/v1",
-      apiKey: process.env.OPENCODEZEN_API_KEY,
+    _litellm = createOpenAI({
+      apiKey: process.env.LITELLM_API_KEY || "dummy-key",
+      baseURL: process.env.LITELLM_BASE_URL,
     });
   }
-  return _opencodezen;
+  return _litellm;
 }
 
 /**
@@ -181,6 +182,13 @@ function resolveOpenRouterModelId(modelId: string): string {
   return OPENROUTER_MODEL_ALIASES[modelId] ?? modelId;
 }
 
+function resolveLiteLLMModelId(modelId: string): string {
+  if (modelId.startsWith("google/")) {
+    return modelId.replace("google/", "gemini/");
+  }
+  return modelId;
+}
+
 /**
  * Maps canonical model IDs (provider/model) to OpenCode Zen model IDs.
  * Zen strips the provider prefix and uses its own naming for some models.
@@ -241,8 +249,8 @@ export function resolveModel(modelId: string, gatewayOverride?: AIGateway): Lang
     return wrapModel(getOpenRouterProvider()(resolveOpenRouterModelId(modelId)));
   }
 
-  if (gatewayConfig === "opencodezen") {
-    return wrapModel(getOpenCodeZenProvider()(resolveOpenCodeZenModelId(modelId)));
+  if (gatewayConfig === "litellm") {
+    return wrapModel(getLiteLLMProvider()(resolveLiteLLMModelId(modelId)));
   }
 
   const [provider, ...rest] = modelId.split("/");