Claude Bridge

API gateway that intercepts Claude Code CLI and exposes it through Anthropic Messages API.

Overview

Claude Bridge wraps the Claude Code CLI (not the SDK) and exposes it through an Anthropic-compatible REST API. It acts as an interceptor, translating HTTP API requests into CLI subprocess calls. Each request is handled as a single, stateless task to Claude Code.

Features

• CLI Interceptor - Wraps Claude Code CLI, not the Python SDK
• Anthropic Messages API compatibility - Drop-in replacement for Anthropic API
• Anthropic SDK compatible - Works seamlessly with the official Anthropic Python SDK
• Streaming support - Server-Sent Events (SSE) for real-time responses
• Stateless architecture - Each request is independent
• No SDK dependency - Direct subprocess calls to claude CLI
• Full Claude Code capabilities - All CLI features available

Quick Start (No Installation Required)

Run Claude Bridge instantly with uvx (no installation needed):

uvx claude-bridge

This will download, install, and run the server in an isolated environment.

Note: uvx requires the package to be published to PyPI. For local development, use uv run claude-bridge instead.

---

Installation

Prerequisites

• Python 3.12+
• uv (recommended) - Fast Python package installer and runner: pip install uv
• Claude CLI - Install from claude.com
  • The claude command must be available in your PATH
  • Authenticate using: claude setup-token

Option 1: Run with uvx (Recommended - No Installation)

# Run directly without installing
uvx claude-bridge

Option 2: Install Locally

Using uv (recommended):

uv pip install -e .

Or for development:

uv pip install -e ".[dev]"

This will install the claude-bridge CLI command in your virtual environment.

Alternatively, using pip:

pip install -e ".[dev]"

Usage

Start the server

With uvx (no installation required):

uvx claude-bridge

After local installation:

claude-bridge

Or with uv run:

uv run claude-bridge

Or directly with Python:

python main.py

The server will start on http://localhost:8000 by default.

Configuration

Create a .env file in the project root (or use environment variables):

# Application settings
DEBUG=false
HOST=0.0.0.0
PORT=8000

# Claude CLI settings
CLAUDE_CLI_PATH=claude  # Path to claude binary
CLAUDE_CWD=/path/to/working/directory

---

⚠️ File Upload Configuration (Required)

File upload is disabled by default for security. To enable:

1. Configure via .env file OR command-line arguments

Option A: Using .env file (persistent)

# Required for file upload
CLAUDE_ALLOWED_TOOLS_STR=Read
CLAUDE_ALLOWED_DIRECTORIES_STR=/tmp

# Permission mode (required for non-interactive API)
CLAUDE_PERMISSION_MODE=bypassPermissions

Option B: Using CLI arguments (override .env, higher priority)

claude-bridge --allowed-tools Read --allowed-directories /tmp

Note: CLI arguments take precedence over environment variables.

2. Understand Security Implications

What you're allowing:

• CLAUDE_ALLOWED_TOOLS_STR=Read - Claude can read files (but not write/execute)
• CLAUDE_ALLOWED_DIRECTORIES_STR=/tmp - Claude can only access /tmp directory
• CLAUDE_PERMISSION_MODE=bypassPermissions - No interactive permission prompts (required for API mode)

What is protected:

• ❌ Claude cannot execute code (no Bash tool)
• ❌ Claude cannot modify files (no Write/Edit tools)
• ❌ Claude cannot access other directories (only those you specify)

3. Adjust for Your Environment

macOS/Linux:

CLAUDE_ALLOWED_DIRECTORIES_STR=/tmp

Windows:

CLAUDE_ALLOWED_DIRECTORIES_STR=C:\Temp

Custom temp directory:

CLAUDE_ALLOWED_DIRECTORIES_STR=/var/myapp/temp

Multiple directories (comma-separated):

CLAUDE_ALLOWED_DIRECTORIES_STR=/tmp,/var/app-temp

4. Start Server

After configuring .env or using CLI arguments:

claude-bridge

You should see:

INFO: Claude CLI permissions configured: tools=[Read], directories=[/tmp], mode=bypassPermissions
INFO: File upload is ENABLED

Troubleshooting

Error: "CLAUDE_ALLOWED_TOOLS_STR not configured" → Add CLAUDE_ALLOWED_TOOLS_STR=Read to your .env file, OR → Use CLI argument: --allowed-tools Read

Error: "contains non-existent directory" → Verify the directory exists: ls -la /tmp

Advanced: Using All Permission Arguments

# Enable multiple tools and directories via CLI
claude-bridge \
  --allowed-tools "Read,Bash" \
  --disallowed-tools "Write,Edit" \
  --allowed-directories "/tmp,/var/app-data"

Permission errors in responses → Ensure your temp directory matches where files are created

Example: Upload File

curl -X POST http://localhost:8000/anthropic/v1/messages \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5-20250929",
    "max_tokens": 1024,
    "messages": [{
      "role": "user",
      "content": [{
        "type": "text",
        "text": "What is in this image?"
      }, {
        "type": "image",
        "source": {
          "type": "base64",
          "media_type": "image/png",
          "data": "iVBORw0KGgoAAAA...base64_image_data..."
        }
      }]
    }]
  }'

---

Authentication

The bridge uses the Claude CLI's existing authentication. Make sure you've authenticated:

# Authenticate Claude CLI
claude setup-token

# Verify it works
claude --version
claude --print "Hello, Claude!"

The bridge will automatically use the CLI's credentials. No need to configure API keys separately!

API Endpoints

POST /anthropic/v1/messages

Create a message using Claude Code.

Supported Model Names:

The bridge automatically maps Anthropic API model names to Claude CLI aliases:

• claude-sonnet-4 → sonnet (latest Sonnet)
• claude-opus-4 → opus (latest Opus)
• claude-haiku-4 → haiku (latest Haiku)
• Or use full model names like claude-sonnet-4-5-20250929 (recommended for stability)

Non-streaming request:

curl -X POST http://localhost:8000/anthropic/v1/messages \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5-20250929",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Hello, Claude!"}
    ]
  }'

Streaming request:

curl -X POST http://localhost:8000/anthropic/v1/messages \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5-20250929",
    "max_tokens": 1024,
    "stream": true,
    "messages": [
      {"role": "user", "content": "Count to 10"}
    ]
  }'

With system prompt:

curl -X POST http://localhost:8000/anthropic/v1/messages \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5-20250929",
    "max_tokens": 1024,
    "system": "You are a helpful assistant.",
    "messages": [
      {"role": "user", "content": "What is 2+2?"}
    ]
  }'

GET /health

Health check endpoint.

curl http://localhost:8000/health

Using with Anthropic SDK

The bridge is fully compatible with the official Anthropic Python SDK. Simply configure the client with a custom base_url:

import anthropic

client = anthropic.AsyncAnthropic(
    api_key="not-needed",  # Bridge uses CLI authentication
    base_url="http://localhost:8000/anthropic"
)

# Streaming example
async with client.messages.stream(
    model="claude-sonnet-4-5-20250929",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello!"}]
) as stream:
    async for text in stream.text_stream:
        print(text, end="", flush=True)

# Non-streaming example
message = await client.messages.create(
    model="claude-sonnet-4-5-20250929",
    max_tokens=1024,
    messages=[{"role": "user", "content": "What is 2+2?"}]
)
print(message.content[0].text)

Note: The bridge does not validate API keys. Authentication is handled by the Claude CLI itself via claude setup-token.

Development

Setup Pre-commit Hooks

This project uses pre-commit hooks for code quality and consistency:

# Install hooks (one-time setup)
pre-commit install

# Run manually on all files (optional)
pre-commit run --all-files

Hooks will automatically run on git commit and include:

• ✅ Code formatting (ruff)
• ✅ Linting (ruff)
• ✅ Type checking (mypy)
• ✅ Security scanning (bandit)
• ✅ File hygiene (trailing whitespace, EOF, etc.)
• ✅ Secret detection (detect-private-key)

Run tests

The project includes comprehensive unit and integration tests:

# Run all tests with coverage
pytest

# Run specific test categories
pytest tests/unit/          # Unit tests only
pytest tests/integration/   # Integration tests only

# Run with verbose output
pytest -v

# Run specific test file
pytest tests/unit/test_adapter.py

# Run without coverage report
pytest --no-cov

# Generate HTML coverage report
pytest --cov-report=html
# Then open htmlcov/index.html in your browser

Test Structure:

• tests/unit/ - Fast, isolated unit tests for individual components
• tests/integration/ - Integration tests with mocked external dependencies
• tests/fixtures/ - Sample data for tests
• tests/conftest.py - Shared pytest fixtures

Manual code quality checks

# Linting and formatting
ruff check src/ --fix
ruff format src/

# Type checking
mypy src/

# Security scanning
bandit -c pyproject.toml -r src/

License

MIT