using-ccproxy-api

name: using-ccproxy-api description: >- Guides users through ccproxy as an OpenAI-compatible and Anthropic-compatible LLM API server with SDK integration, OAuth authentication, sentinel key substitution, model routing, and troubleshooting. Use when installing ccproxy, configuring SDK clients (Anthropic, OpenAI, LiteLLM, Agent SDK) against ccproxy, setting up per-project instances, debugging authentication errors, setting up OAuth token forwarding, or understanding the hook pipeline and shaping system.

Using ccproxy as an LLM API Server

ccproxy exposes an OpenAI-compatible and Anthropic-compatible API via a mitmproxy-based interceptor. Any SDK or HTTP client that supports custom base_url can use it.

Installation

System-wide (Home Manager)

Add ccproxy as a flake input and enable the Home Manager module:

# flake.nix
inputs.ccproxy.url = "github:starbaser/ccproxy";

# home configuration
programs.ccproxy = {
  enable = true;
  settings = {
    # Override defaults here (port, providers, transforms, etc.)
  };
};

This installs the ccproxy binary, generates ~/.config/ccproxy/ccproxy.yaml from Nix, and creates a systemd --user service that auto-restarts on config changes.

Standalone (any Linux)

# Clone and enter devShell
git clone https://github.com/starbaser/ccproxy
cd ccproxy
nix develop   # or: direnv allow

# Initialize config
ccproxy init          # copies template to ~/.config/ccproxy/ccproxy.yaml
ccproxy init --force  # overwrites existing config

# Edit config
$EDITOR ~/.config/ccproxy/ccproxy.yaml

# Start
ccproxy start

Per-project instance

Each project can run its own ccproxy with isolated config, port, and transforms via the flake's mkConfig. Use ccproxy.defaultSettings.settings (top-level, no ${system} selector needed) as the base to inherit all defaults (hooks, shaping, providers, otel).

# project flake.nix
{
  inputs.ccproxy.url = "github:starbaser/ccproxy";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils, ccproxy }:
    let
      defaults = ccproxy.defaultSettings.settings;
    in
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        proxyConfig = ccproxy.lib.${system}.mkConfig {
          settings = defaults // {
            port = 4010;  # per-project: use 4010+ to avoid collisions
            inspector = defaults.inspector // {
              port = 8090;
              cert_dir = "./.ccproxy";
              transforms = [
                { match_path = "/v1/messages"; action = "redirect";
                  dest_provider = "anthropic"; dest_host = "api.anthropic.com";
                  dest_path = "/v1/messages"; }
              ];
            };
          };
        };
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            ccproxy.packages.${system}.default
            just process-compose
          ];
          shellHook = proxyConfig.shellHook;
        };
      });
}

mkConfig generates a Nix store ccproxy.yaml, and its shellHook symlinks it into .ccproxy/ and exports CCPROXY_CONFIG_DIR. The .envrc just needs use flake.

Add .ccproxy/ to .gitignore — the directory contains a Nix-generated symlink that is machine-specific and regenerated on nix develop:

# .gitignore
.ccproxy/

Port assignment conventions

Running the instance

# Foreground
ccproxy start

# Via process-compose (recommended for dev)
just up       # process-compose up --detached
just down     # process-compose down

# Check health
ccproxy status              # Rich panel
ccproxy status --json       # Machine-readable
ccproxy status --proxy      # Exit 0 if proxy up, 1 if down
ccproxy status --inspect    # Exit 0 if inspector up, 2 if down

process-compose.yml

Use ccproxy status --proxy as the readiness probe so dependent processes wait for the proxy to be healthy:

# process-compose.yml
version: "0.5"

processes:
  ccproxy:
    command: "ccproxy start"
    readiness_probe:
      exec:
        command: "ccproxy status --proxy"
      initial_delay_seconds: 5
      period_seconds: 30
      timeout_seconds: 10
      failure_threshold: 6
    availability:
      restart: on_failure
      backoff_seconds: 2
      max_restarts: 5

  myapp:
    command: "python -m myapp"
    depends_on:
      ccproxy:
        condition: process_healthy

Wiring SDK clients

Point any SDK at the per-project port with a sentinel key:

import anthropic

client = anthropic.Anthropic(
    api_key="sk-ant-oat-ccproxy-anthropic",
    base_url="http://localhost:4010",  # per-project port
)

Or via environment variables in shellHook / .envrc:

export ANTHROPIC_BASE_URL="http://localhost:4010"
export ANTHROPIC_API_KEY="sk-ant-oat-ccproxy-anthropic"

Configuration

All config lives in $CCPROXY_CONFIG_DIR/ccproxy.yaml (default ~/.config/ccproxy/ccproxy.yaml).

ccproxy:
  host: 127.0.0.1
  port: 4000

  providers:
    anthropic:
      auth:
        type: command
        command: "jq -r '.claudeAiOauth.accessToken' ~/.claude/.credentials.json"
      host: api.anthropic.com
      path: /v1/messages
      provider: anthropic
    gemini:
      auth:
        type: command
        command: "jq -r '.access_token' ~/.gemini/oauth_creds.json"
      host: cloudcode-pa.googleapis.com
      path: "/v1internal:{action}"
      provider: gemini

  hooks:
    inbound:
      - ccproxy.hooks.inject_auth
      - ccproxy.hooks.extract_session_id
    outbound:
      - ccproxy.hooks.inject_mcp_notifications
      - ccproxy.hooks.verbose_mode
      - ccproxy.hooks.shape

  shaping:
    enabled: true
    shapes_dir: ~/.config/ccproxy/shapes

  inspector:
    port: 8083
    cert_dir: ~/.config/ccproxy
    transforms:
      - match_path: /v1/messages
        action: redirect
        dest_provider: anthropic
        dest_host: api.anthropic.com
        dest_path: /v1/messages

See reference/routing-and-config.md for transform rules, providers patterns, and hook parameters.

How authentication works

OAuth mode (subscription accounts -- Claude Max, Team, Enterprise):

1. Client sends sentinel key sk-ant-oat-ccproxy-{provider} as API key
2. inject_auth hook detects sentinel prefix, looks up real token from providers[name].auth
3. shape hook replays a captured {provider}.mflow shape: strips configured headers, injects content_fields from the incoming request, runs shape inner-DAG hooks (UUID regeneration, Anthropic billing-header re-signing, cache breakpoint normalization), stamps the result onto the outbound flow
4. Request reaches provider API with valid OAuth Bearer token and full identity envelope (user-agent, anthropic-beta, x-stainless-*, billing header, system prompt prefix)

API key mode (direct API keys):

1. Client sends real API key via x-api-key or Authorization header
2. Key passes through to the provider unchanged

Sentinel key format

sk-ant-oat-ccproxy-{provider}

Where {provider} matches a key in providers config. Common values:

• sk-ant-oat-ccproxy-anthropic -- uses providers.anthropic.auth token
• sk-ant-oat-ccproxy-gemini -- uses providers.gemini.auth token

Default hooks

hooks:
  inbound:
    - ccproxy.hooks.inject_auth
    - ccproxy.hooks.extract_session_id
  outbound:
    - ccproxy.hooks.gemini_cli
    - ccproxy.hooks.inject_mcp_notifications
    - ccproxy.hooks.verbose_mode
    - ccproxy.hooks.shape
    - ccproxy.hooks.commitbee_compat

• inject_auth -- substitutes sentinel key with real token, sets Authorization: Bearer {token} (or the custom auth.header), clears other auth headers, and stamps ccproxy auth metadata for routing/retry
• extract_session_id -- parses metadata.user_id for MCP notification routing
• gemini_cli -- wraps Gemini sentinel-key bodies in the v1internal envelope, conditionally masquerades google-genai-sdk/* UAs, rewrites paths to cloudcode-pa.googleapis.com
• inject_mcp_notifications -- injects buffered MCP terminal events as tool_use/tool_result pairs
• verbose_mode -- strips redact-thinking-* from anthropic-beta to enable full thinking output
• shape -- replays a captured shape ({provider}.mflow) onto the outbound flow, stamping identity headers, billing header, and system prompt prefix
• commitbee_compat -- last-mile compatibility shim for the commitbee tool

AuthAddon and GeminiAddon are full mitmproxy addons (not pipeline hooks) registered after the outbound stage: AuthAddon handles 401 detection / refresh / replay; GeminiAddon handles capacity fallback + cloudcode-pa envelope unwrap.

Shape replay -- where identity comes from

ccproxy does not synthesize Claude Code identity headers in code. Anthropic-bound traffic depends on a shape: a real mitmproxy.http.HTTPFlow from the Claude CLI persisted as a .mflow file. ccproxy ships a packaged default shape for Anthropic; a user-captured shape at ~/.config/ccproxy/shapes/anthropic.mflow overrides it. The shape hook replays the shape on every outbound flow, providing user-agent, anthropic-beta, x-stainless-*, the signed x-anthropic-billing-header, and the system prompt prefix.

If the shape in effect is from an outdated Claude CLI release, Anthropic will reject the request with 401/400. Capture (or refresh) a local override with:

ccproxy run --inspect -- claude -p "shape capture"
ccproxy shapes save anthropic

See docs/shaping.md for the canonical reference (capture workflow, shape inner-DAG hooks, billing salt configuration, custom hooks).

Quick start

# Anthropic SDK (OAuth via sentinel key)
import anthropic
client = anthropic.Anthropic(
    api_key="sk-ant-oat-ccproxy-anthropic",
    base_url="http://localhost:4000",
)

# OpenAI SDK
from openai import OpenAI
client = OpenAI(
    api_key="sk-ant-oat-ccproxy-anthropic",
    base_url="http://localhost:4000",
)

SDK integration

Anthropic Python SDK

import anthropic

client = anthropic.Anthropic(
    api_key="sk-ant-oat-ccproxy-anthropic",
    base_url="http://localhost:4000",
)

response = client.messages.create(
    model="claude-sonnet-4-5-20250929",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}],
)

No extra headers needed -- the shape hook replays the captured Anthropic shape, supplying anthropic-beta, anthropic-version, the signed billing header, and the system prompt prefix automatically.

Streaming:

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

OpenAI Python SDK

from openai import OpenAI

client = OpenAI(
    api_key="sk-ant-oat-ccproxy-anthropic",
    base_url="http://localhost:4000",
)

response = client.chat.completions.create(
    model="claude-sonnet-4-5-20250929",
    messages=[{"role": "user", "content": "Hello"}],
)

Requires a transform rule to rewrite from OpenAI format to the destination provider format via lightllm.

LiteLLM SDK

import asyncio, litellm

async def main():
    response = await litellm.acompletion(
        model="claude-sonnet-4-5-20250929",
        messages=[{"role": "user", "content": "Hello"}],
        api_base="http://127.0.0.1:4000",
        api_key="sk-ant-oat-ccproxy-anthropic",
    )
    print(response.choices[0].message.content)

asyncio.run(main())

Note: litellm.anthropic.messages bypasses proxies. Always use litellm.acompletion().

Claude Agent SDK

import os
os.environ["ANTHROPIC_BASE_URL"] = "http://localhost:4000"
os.environ["ANTHROPIC_API_KEY"] = "sk-ant-oat-ccproxy-anthropic"

from claude_agent_sdk import query, ClaudeAgentOptions

async for message in query(
    prompt="Your prompt here",
    options=ClaudeAgentOptions(
        allowed_tools=["Read", "Glob"],
        permission_mode="default",
        cwd=os.getcwd(),
    ),
):
    # Handle AssistantMessage, ResultMessage, etc.
    pass

Environment variables (any SDK)

export ANTHROPIC_BASE_URL="http://localhost:4000"
export ANTHROPIC_API_KEY="sk-ant-oat-ccproxy-anthropic"
# OpenAI compat
export OPENAI_BASE_URL="http://localhost:4000"
export OPENAI_API_BASE="http://localhost:4000"

curl (raw HTTP)

curl http://localhost:4000/v1/messages \
  -H "Content-Type: application/json" \
  -H "x-api-key: sk-ant-oat-ccproxy-anthropic" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-5-20250929",
    "max_tokens": 100,
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Model routing

Model routing is configured via inspector.transforms in ccproxy.yaml. Each transform rule matches by match_host, match_path, and/or match_model, then rewrites to dest_provider/dest_model via the lightllm dispatch. First match wins. Unmatched reverse proxy flows get a 501 error; unmatched WireGuard flows pass through unchanged.

See reference/routing-and-config.md for transform configuration patterns.

Troubleshooting

Authentication failures are the most common issue. Follow this decision tree:

Error message?
│
├─ "This credential is only authorized for use with Claude Code"
│  ▶ See: Missing or stale captured shape (system prompt prefix not stamped)
│
├─ "OAuth is not supported" / "invalid x-api-key"
│  ▶ See: Missing or stale captured shape (anthropic-beta not stamped)
│
├─ 401 Unauthorized / token errors
│  ▶ See: Token issues
│
├─ Connection refused / timeout
│  ▶ See: Connectivity
│
└─ Other / unclear
   ▶ See: General diagnostics

See reference/troubleshooting.md for the full diagnostic guide with resolution steps for each branch.

Quick diagnostic commands

ccproxy status              # Verify proxy is running
ccproxy status --json       # Machine-readable status with URL
ccproxy logs -f             # Stream logs in real-time
ccproxy logs -n 50          # Last 50 lines

Known limitations (upstream flake issues)

1. Shape required for Anthropic — there is no synthetic-identity fallback. If the packaged default (or a user-captured override at ~/.config/ccproxy/shapes/anthropic.mflow) is stale for the current Claude CLI release, requests fail with 401/400. Refresh via ccproxy shapes save anthropic.
2. devConfig overwrites inspector atomically — top-level // merge on inspector drops sub-keys not re-specified. Deep merge each nested attrset explicitly: defaults.inspector // { ... }.
3. supportedSystems limited — only x86_64-linux and aarch64-linux; aarch64-darwin not supported.

Reference files

• reference/troubleshooting.md -- Full diagnostic decision tree with error-specific resolution steps
• reference/routing-and-config.md -- Model routing, config.yaml patterns, hook pipeline details