Merge pull request #45 from FammasMaz/feature/anthropic-endpoints

Anthropic endpoint for claude code

Author: Mirrowel

DOCUMENTATION.md

@@ -10,6 +10,7 @@ The project is a monorepo containing two primary components:
     *   **Batch Manager**: Optimizes high-volume embedding requests.
     *   **Detailed Logger**: Provides per-request file logging for debugging.
     *   **OpenAI-Compatible Endpoints**: `/v1/chat/completions`, `/v1/embeddings`, etc.
+    *   **Anthropic-Compatible Endpoints**: `/v1/messages`, `/v1/messages/count_tokens` for Claude Code and other Anthropic API clients.
     *   **Model Filter GUI**: Visual interface for configuring model ignore/whitelist rules per provider (see Section 6).
 2.  **The Resilience Library (`rotator_library`)**: This is the core engine that provides high availability. It is consumed by the proxy app to manage a pool of API keys, handle errors gracefully, and ensure requests are completed successfully even when individual keys or provider endpoints face issues.
 
@@ -816,6 +817,108 @@ When a custom cap triggers a cooldown longer than the exhaustion threshold, it a
 
 **Defaults:** See `src/rotator_library/config/defaults.py` for all configurable defaults.
 
+### 2.21. Anthropic API Compatibility (`anthropic_compat/`)
+
+A translation layer that enables Anthropic API clients (like Claude Code) to use any OpenAI-compatible provider through the proxy.
+
+#### Architecture
+
+The module consists of three components:
+
+| File | Purpose |
+|------|---------|
+| `models.py` | Pydantic models for Anthropic request/response formats (`AnthropicMessagesRequest`, `AnthropicMessage`, `AnthropicTool`, etc.) |
+| `translator.py` | Bidirectional format translation functions |
+| `streaming.py` | SSE format conversion for streaming responses |
+
+#### Request Translation (`translate_anthropic_request`)
+
+Converts Anthropic Messages API requests to OpenAI Chat Completions format:
+
+**Message Conversion:**
+- Anthropic `system` field → OpenAI system message
+- `content` blocks (text, image, tool_use, tool_result) → OpenAI format
+- Image blocks with base64 data → OpenAI `image_url` with data URI
+- Document blocks (PDF, etc.) → OpenAI `image_url` format
+
+**Tool Conversion:**
+- Anthropic `tools` with `input_schema` → OpenAI `tools` with `parameters`
+- `tool_choice.type: "any"` → `"required"`
+- `tool_choice.type: "tool"` → `{"type": "function", "function": {"name": ...}}`
+
+**Thinking Configuration:**
+- `thinking.type: "enabled"` → `reasoning_effort: "high"` + `thinking_budget`
+- `thinking.type: "disabled"` → `reasoning_effort: "disable"`
+- Opus models default to thinking enabled
+
+**Special Handling:**
+- Reorders assistant content blocks: thinking → text → tool_use
+- Injects `[Continue]` prompt for fresh thinking turns
+- Preserves thinking signatures for multi-turn conversations
+
+#### Response Translation (`openai_to_anthropic_response`)
+
+Converts OpenAI Chat Completions responses to Anthropic Messages format:
+
+**Content Blocks:**
+- `reasoning_content` → thinking block with signature
+- `content` → text block
+- `tool_calls` → tool_use blocks with parsed JSON input
+
+**Field Mapping:**
+- `finish_reason: "stop"` → `stop_reason: "end_turn"`
+- `finish_reason: "length"` → `stop_reason: "max_tokens"`
+- `finish_reason: "tool_calls"` → `stop_reason: "tool_use"`
+
+**Usage Translation:**
+- `prompt_tokens` minus `cached_tokens` → `input_tokens`
+- `completion_tokens` → `output_tokens`
+- `prompt_tokens_details.cached_tokens` → `cache_read_input_tokens`
+
+#### Streaming Wrapper (`anthropic_streaming_wrapper`)
+
+Converts OpenAI SSE streaming format to Anthropic's event-based format:
+
+**Event Types Generated:**
+```
+message_start      → Initial message metadata
+content_block_start → Start of text/thinking/tool_use block
+content_block_delta → Incremental content (text_delta, thinking_delta, input_json_delta)
+content_block_stop  → End of content block
+message_delta      → Final metadata (stop_reason, usage)
+message_stop       → End of message
+```
+
+**Features:**
+- Accumulates tool call arguments across chunks
+- Handles thinking/reasoning content from `delta.reasoning_content`
+- Proper block indexing for multiple content blocks
+- Cache token handling in usage statistics
+- Error recovery with proper message structure
+
+#### Client Integration
+
+The `RotatingClient` provides two methods for Anthropic compatibility:
+
+```python
+async def anthropic_messages(self, request, raw_request=None, pre_request_callback=None):
+    """Handle Anthropic Messages API requests."""
+    # 1. Translate Anthropic request to OpenAI format
+    # 2. Call acompletion() with translated request
+    # 3. Convert response back to Anthropic format
+    # 4. For streaming: wrap with anthropic_streaming_wrapper
+
+async def anthropic_count_tokens(self, request):
+    """Count tokens for Anthropic-format request."""
+    # Translates messages and tools, then uses token_count()
+```
+
+#### Authentication
+
+The proxy accepts both Anthropic and OpenAI authentication styles:
+- `x-api-key` header (Anthropic style)
+- `Authorization: Bearer` header (OpenAI style)
+
 ### 3.5. Antigravity (`antigravity_provider.py`)
 
 The most sophisticated provider implementation, supporting Google's internal Antigravity API for Gemini 3 and Claude models (including **Claude Opus 4.5**, Anthropic's most powerful model).

README.md

@@ -4,19 +4,20 @@
 
 **One proxy. Any LLM provider. Zero code changes.**
 
-A self-hosted proxy that provides a single, OpenAI-compatible API endpoint for all your LLM providers. Works with any application that supports custom OpenAI base URLs—no code changes required in your existing tools.
+A self-hosted proxy that provides OpenAI and Anthropic compatible API endpoints for all your LLM providers. Works with any application that supports custom OpenAI or Anthropic base URLs—including Claude Code, Opencode,  and more—no code changes required in your existing tools.
 
 This project consists of two components:
 
-1. **The API Proxy** — A FastAPI application providing a universal `/v1/chat/completions` endpoint
+1. **The API Proxy** — A FastAPI application providing universal `/v1/chat/completions` (OpenAI) and `/v1/messages` (Anthropic) endpoints
 2. **The Resilience Library** — A reusable Python library for intelligent API key management, rotation, and failover
 
 ---
 
 ## Why Use This?
 
-- **Universal Compatibility** — Works with any app supporting OpenAI-compatible APIs: Opencode, Continue, Roo/Kilo Code, JanitorAI, SillyTavern, custom applications, and more
+- **Universal Compatibility** — Works with any app supporting OpenAI or Anthropic APIs: Claude Code, Opencode, Continue, Roo/Kilo Code, Cursor, JanitorAI, SillyTavern, custom applications, and more
 - **One Endpoint, Many Providers** — Configure Gemini, OpenAI, Anthropic, and [any LiteLLM-supported provider](https://docs.litellm.ai/docs/providers) once. Access them all through a single API key
+- **Anthropic API Compatible** — Use Claude Code or any Anthropic SDK client with non-Anthropic providers like Gemini, OpenAI, or custom models
 - **Built-in Resilience** — Automatic key rotation, failover on errors, rate limit handling, and intelligent cooldowns
 - **Exclusive Provider Support** — Includes custom providers not available elsewhere: **Antigravity** (Gemini 3 + Claude Sonnet/Opus 4.5), **Gemini CLI**, **Qwen Code**, and **iFlow**
 
@@ -177,12 +178,57 @@ In your configuration file (e.g., `config.json`):
 
 </details>
 
+<details>
+<summary><b>Claude Code</b></summary>
+
+Claude Code natively supports custom Anthropic API endpoints. The recommended setup is to edit your Claude Code `settings.json`:
+
+```json
+{
+  "env": {
+    "ANTHROPIC_AUTH_TOKEN": "your-proxy-api-key",
+    "ANTHROPIC_BASE_URL": "http://127.0.0.1:8000",
+    "ANTHROPIC_DEFAULT_OPUS_MODEL": "gemini/gemini-3-pro",
+    "ANTHROPIC_DEFAULT_SONNET_MODEL": "gemini/gemini-3-flash",
+    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "openai/gpt-5-mini"
+  }
+}
+```
+
+Now you can use Claude Code with Gemini, OpenAI, or any other configured provider.
+
+</details>
+
+<details>
+<summary><b>Anthropic Python SDK</b></summary>
+
+```python
+from anthropic import Anthropic
+
+client = Anthropic(
+    base_url="http://127.0.0.1:8000",
+    api_key="your-proxy-api-key"
+)
+
+# Use any provider through Anthropic's API format
+response = client.messages.create(
+    model="gemini/gemini-3-flash",  # provider/model format
+    max_tokens=1024,
+    messages=[{"role": "user", "content": "Hello!"}]
+)
+print(response.content[0].text)
+```
+
+</details>
+
 ### API Endpoints
 
 | Endpoint | Description |
 |----------|-------------|
 | `GET /` | Status check — confirms proxy is running |
-| `POST /v1/chat/completions` | Chat completions (main endpoint) |
+| `POST /v1/chat/completions` | Chat completions (OpenAI format) |
+| `POST /v1/messages` | Chat completions (Anthropic format) — Claude Code compatible |
+| `POST /v1/messages/count_tokens` | Count tokens for Anthropic-format requests |
 | `POST /v1/embeddings` | Text embeddings |
 | `GET /v1/models` | List all available models with pricing & capabilities |
 | `GET /v1/models/{model_id}` | Get details for a specific model |