Add Google Gemini as an API provider (via Anthropic-compatible gateway)

.env.example

@@ -30,7 +30,7 @@
 # ANTHROPIC_DEFAULT_HAIKU_MODEL=claude-3-5-haiku@20241022
 
 # ===================
-# Alternative API Providers (Azure, GLM, Ollama, Kimi, Custom)
+# Alternative API Providers (Azure, GLM, Ollama, Kimi, Gemini, Custom)
 # ===================
 # Configure via Settings UI (recommended) or set env vars below.
 # When both are set, env vars take precedence.
@@ -61,3 +61,11 @@
 # ANTHROPIC_DEFAULT_OPUS_MODEL=kimi-k2.5
 # ANTHROPIC_DEFAULT_SONNET_MODEL=kimi-k2.5
 # ANTHROPIC_DEFAULT_HAIKU_MODEL=kimi-k2.5
+#
+# Google Gemini (via an Anthropic-compatible LiteLLM proxy):
+#   GEMINI_API_KEY=... litellm --model gemini/gemini-2.5-pro --alias gemini-2.5-pro --port 4000
+# ANTHROPIC_BASE_URL=http://localhost:4000
+# ANTHROPIC_AUTH_TOKEN=your-litellm-master-key
+# ANTHROPIC_DEFAULT_OPUS_MODEL=gemini-2.5-pro
+# ANTHROPIC_DEFAULT_SONNET_MODEL=gemini-2.5-pro
+# ANTHROPIC_DEFAULT_HAIKU_MODEL=gemini-2.5-pro

CLAUDE.md

@@ -418,18 +418,23 @@ Run coding agents via Google Cloud Vertex AI:
 
 **Note:** Use `@` instead of `-` in model names for Vertex AI.
 
-### Alternative API Providers (GLM, Ollama, Kimi, Custom)
+### Alternative API Providers (GLM, Ollama, Kimi, Gemini, Custom)
 
 Alternative providers are configured via the **Settings UI** (gear icon > API Provider section). Select a provider, set the base URL, auth token, and model — no `.env` changes needed.
 
-**Available providers:** Claude (default), GLM (Zhipu AI), Ollama (local models), Kimi (Moonshot), Custom
+**Available providers:** Claude (default), GLM (Zhipu AI), Ollama (local models), Kimi (Moonshot), Gemini (Google, via LiteLLM), Custom
 
 **Ollama notes:**
 - Requires Ollama v0.14.0+ with Anthropic API compatibility
 - Install: https://ollama.com → `ollama serve` → `ollama pull qwen3-coder`
 - Recommended models: `qwen3-coder`, `deepseek-coder-v2`, `codellama`
 - Performance depends on local hardware (GPU recommended)
 
+**Gemini notes:**
+- Google has no Anthropic Messages-compatible endpoint, so Gemini goes through an Anthropic-compatible gateway (LiteLLM proxy, default `http://localhost:4000`)
+- Start: `GEMINI_API_KEY=... litellm --model gemini/gemini-2.5-pro --alias gemini-2.5-pro --port 4000`
+- Auth token is sent as `ANTHROPIC_AUTH_TOKEN` (the LiteLLM master key, if set); base URL and model are editable in the UI
+
 ## Claude Code Integration
 
 **Slash commands** (`.claude/commands/`):

README.md

@@ -332,14 +332,24 @@ When test progress increases, the agent sends:
 }
 ```
 
-### Alternative API Providers (GLM, Ollama, Kimi, Custom)
+### Alternative API Providers (GLM, Ollama, Kimi, Gemini, Custom)
 
 Alternative providers are configured via the **Settings UI** (gear icon > API Provider). Select your provider, set the base URL, auth token, and model directly in the UI — no `.env` changes needed.
 
-Available providers: **Claude** (default), **GLM** (Zhipu AI), **Ollama** (local models), **Kimi** (Moonshot), **Custom**
+Available providers: **Claude** (default), **GLM** (Zhipu AI), **Ollama** (local models), **Kimi** (Moonshot), **Gemini** (Google, via LiteLLM), **Custom**
 
 For Ollama, install [Ollama v0.14.0+](https://ollama.com), run `ollama serve`, and pull a coding model (e.g., `ollama pull qwen3-coder`). Then select "Ollama" in the Settings UI.
 
+For Google Gemini, run an Anthropic-compatible gateway such as [LiteLLM](https://docs.litellm.ai/) in front of the Gemini API (Google does not offer an Anthropic Messages endpoint, and the agents run on the Claude Agent SDK):
+
+```bash
+pip install 'litellm[proxy]'
+export GEMINI_API_KEY=your-gemini-api-key   # from aistudio.google.com
+litellm --model gemini/gemini-2.5-pro --alias gemini-2.5-pro --port 4000
+```
+
+Then select "Google Gemini (via LiteLLM)" in the Settings UI. The base URL defaults to `http://localhost:4000`; enter the LiteLLM master key as the API key if you configured one. Pick a listed model or type any model name your gateway serves (e.g. a `model_list` entry in a LiteLLM `config.yaml`). Tool-use quality and context handling depend on the model and gateway, so results may differ from Claude.
+
 ### Using Vertex AI
 
 Add these variables to your `.env` file to run agents via Google Cloud Vertex AI:

registry.py

@@ -827,6 +827,20 @@ def get_all_settings() -> dict[str, str]:
         ],
         "default_model": "qwen3-coder",
     },
+    "gemini": {
+        # Google does not expose an Anthropic Messages-compatible endpoint, so Gemini is
+        # reached through an Anthropic-compatible gateway such as LiteLLM (default port 4000)
+        # that translates /v1/messages requests to the Gemini API.
+        "name": "Google Gemini (via LiteLLM)",
+        "base_url": "http://localhost:4000",
+        "requires_auth": True,
+        "auth_env_var": "ANTHROPIC_AUTH_TOKEN",
+        "models": [
+            {"id": "gemini-2.5-pro", "name": "Gemini 2.5 Pro"},
+            {"id": "gemini-2.5-flash", "name": "Gemini 2.5 Flash"},
+        ],
+        "default_model": "gemini-2.5-pro",
+    },
     "custom": {
         "name": "Custom Provider",
         "base_url": "",

test_api_providers.py

@@ -0,0 +1,44 @@
+"""Tests for API provider presets and the SDK environment they produce."""
+
+import pytest
+
+import registry
+from registry import API_PROVIDERS, get_effective_sdk_env
+
+
+@pytest.mark.parametrize("provider_id", list(API_PROVIDERS))
+def test_provider_definitions_are_well_formed(provider_id):
+    provider = API_PROVIDERS[provider_id]
+    assert provider["name"]
+    model_ids = [m["id"] for m in provider["models"]]
+    if provider["default_model"]:
+        assert provider["default_model"] in model_ids
+
+
+def test_gemini_provider_uses_gateway_defaults(monkeypatch):
+    monkeypatch.setattr(registry, "get_all_settings", lambda: {"api_provider": "gemini"})
+
+    env = get_effective_sdk_env()
+
+    assert env["ANTHROPIC_BASE_URL"] == "http://localhost:4000"
+    assert env["ANTHROPIC_DEFAULT_OPUS_MODEL"] == "gemini-2.5-pro"
+    assert env["ANTHROPIC_DEFAULT_SONNET_MODEL"] == "gemini-2.5-pro"
+    assert env["ANTHROPIC_DEFAULT_HAIKU_MODEL"] == "gemini-2.5-pro"
+    # Ambient Anthropic/Vertex credentials must not leak into the gateway session
+    assert env["ANTHROPIC_API_KEY"] == ""
+    assert env["CLAUDE_CODE_USE_VERTEX"] == ""
+
+
+def test_gemini_provider_honours_user_overrides(monkeypatch):
+    monkeypatch.setattr(registry, "get_all_settings", lambda: {
+        "api_provider": "gemini",
+        "api_base_url": "https://litellm.internal.example.com",
+        "api_auth_token": "sk-litellm-master",
+        "api_model": "gemini-2.5-flash",
+    })
+
+    env = get_effective_sdk_env()
+
+    assert env["ANTHROPIC_BASE_URL"] == "https://litellm.internal.example.com"
+    assert env["ANTHROPIC_AUTH_TOKEN"] == "sk-litellm-master"
+    assert env["ANTHROPIC_DEFAULT_SONNET_MODEL"] == "gemini-2.5-flash"

ui/src/components/SettingsModal.tsx

@@ -25,6 +25,7 @@ const PROVIDER_INFO_TEXT: Record<string, string> = {
   kimi: 'Get an API key at kimi.com',
   glm: 'Get an API key at open.bigmodel.cn',
   ollama: 'Run models locally. Install from ollama.com',
+  gemini: 'Runs through an Anthropic-compatible gateway such as LiteLLM. The gateway holds your Gemini key (aistudio.google.com); enter the gateway key below, if any.',
   custom: 'Connect to any OpenAI-compatible API endpoint.',
 }
 
@@ -116,8 +117,8 @@ export function SettingsModal({ isOpen, onClose }: SettingsModalProps) {
   const currentProviderInfo: ProviderInfo | undefined = providers.find(p => p.id === currentProvider)
   const isAlternativeProvider = currentProvider !== 'claude'
   const showAuthField = isAlternativeProvider && currentProviderInfo?.requires_auth
-  const showBaseUrlField = currentProvider === 'custom' || currentProvider === 'azure'
-  const showCustomModelInput = currentProvider === 'custom' || currentProvider === 'ollama'
+  const showBaseUrlField = currentProvider === 'custom' || currentProvider === 'azure' || currentProvider === 'gemini'
+  const showCustomModelInput = currentProvider === 'custom' || currentProvider === 'ollama' || currentProvider === 'gemini'
 
   return (
     <Dialog open={isOpen} onOpenChange={(open) => !open && onClose()}>
@@ -332,7 +333,7 @@ export function SettingsModal({ isOpen, onClose }: SettingsModalProps) {
                         type="text"
                         value={customBaseUrlInput}
                         onChange={(e) => setCustomBaseUrlInput(e.target.value)}
-                        placeholder={currentProvider === 'azure' ? 'https://your-resource.services.ai.azure.com/anthropic' : 'https://api.example.com/v1'}
+                        placeholder={currentProvider === 'azure' ? 'https://your-resource.services.ai.azure.com/anthropic' : currentProvider === 'gemini' ? 'http://localhost:4000' : 'https://api.example.com/v1'}
                         className="flex-1 py-1.5 px-3 text-sm border rounded-md bg-background"
                       />
                       <Button

ui/src/components/views/SettingsView.tsx

@@ -23,6 +23,7 @@ const PROVIDER_INFO_TEXT: Record<string, string> = {
   kimi: 'Get an API key at kimi.com',
   glm: 'Get an API key at open.bigmodel.cn',
   ollama: 'Run models locally. Install from ollama.com',
+  gemini: 'Runs through an Anthropic-compatible gateway such as LiteLLM. The gateway holds your Gemini key (aistudio.google.com); enter the gateway key below, if any.',
   custom: 'Connect to any OpenAI-compatible API endpoint.',
 }
 
@@ -113,8 +114,8 @@ export function SettingsView() {
   const currentProviderInfo: ProviderInfo | undefined = providers.find(p => p.id === currentProvider)
   const isAlternativeProvider = currentProvider !== 'claude'
   const showAuthField = isAlternativeProvider && currentProviderInfo?.requires_auth
-  const showBaseUrlField = currentProvider === 'custom' || currentProvider === 'azure'
-  const showCustomModelInput = currentProvider === 'custom' || currentProvider === 'ollama'
+  const showBaseUrlField = currentProvider === 'custom' || currentProvider === 'azure' || currentProvider === 'gemini'
+  const showCustomModelInput = currentProvider === 'custom' || currentProvider === 'ollama' || currentProvider === 'gemini'
 
   return (
     <div className="flex-1 overflow-y-auto">
@@ -341,7 +342,7 @@ export function SettingsView() {
                             type="text"
                             value={customBaseUrlInput}
                             onChange={(e) => setCustomBaseUrlInput(e.target.value)}
-                            placeholder={currentProvider === 'azure' ? 'https://your-resource.services.ai.azure.com/anthropic' : 'https://api.example.com/v1'}
+                            placeholder={currentProvider === 'azure' ? 'https://your-resource.services.ai.azure.com/anthropic' : currentProvider === 'gemini' ? 'http://localhost:4000' : 'https://api.example.com/v1'}
                             className="flex-1 py-1.5 px-3 text-sm border rounded-md bg-background"
                           />
                           <Button