OpenCode Cowork Proxy Worker

This project lets Claude use OpenCode Go models, and some OpenCode Zen models.

Claude normally speaks the Anthropic API format. OpenCode Go mostly speaks OpenAI-compatible API format. This small Cloudflare Worker sits in the middle and translates between them.

I covered how to set this up in Claude in How to Use Claude Code for Free with OpenCode.

Image / Vision Support

When you attach an image in Claude Code and send it through this proxy, the request is automatically routed to Qwen3.5 Plus (qwen3.5-plus) — a vision-capable model on OpenCode Go. This happens transparently: the proxy detects image blocks in your request, translates them to OpenAI's image format, and overrides the model to Qwen3.5 Plus so the model can actually see the image.

No configuration needed — it just works as long as you have an OpenCode Go subscription.

Free Models

We support a pay-as-you-go model. Below are the prices per 1M tokens for completely free models available through OpenCode Zen.

These models are available at https://opencode.ai/zen/v1/chat/completions via the /zen prefix. For the full model list and latest pricing, see the OpenCode Zen endpoint docs.

Set Up In Claude

If you want the fastest working setup, use minimax-m2.5-free as the first model.

1. Deploy this Worker to Cloudflare.
2. Copy your deployed Worker URL.
3. In Claude, open Configure third-party Inference.
4. Choose the gateway / third-party inference option.
5. Set the base URL to YOUR_DEPLOYED_WORKER_URL/zen.
6. Set the auth scheme to x-api-key.
7. Paste your OpenCode API key.
8. Add minimax-m2.5-free as the model name.

Important: do not add /v1/messages to the URL. Claude adds that path automatically.

Quick Claude Configuration

Use these values in Claude's Configure third-party Inference screen:

For the default example above, use /zen because minimax-m2.5-free is a Zen model. Use /go for OpenCode Go models instead. Do not add /v1/messages yourself. Claude adds the API path automatically.

What This Does

The Worker accepts Claude's Anthropic-style requests at /v1/messages, converts them to OpenAI-style requests, and sends them to OpenCode Go by default.

You can choose an OpenCode upstream by adding a prefix to the Worker URL:

For example, use YOUR_DEPLOYED_WORKER_URL/go for Go models and YOUR_DEPLOYED_WORKER_URL/zen for Zen models.

It also handles tool calls, streaming, and DeepSeek reasoning output so coding-agent workflows work correctly.

Important: this proxy has been live-tested with minimax-m2.7. Other OpenCode Go models are included from the public OpenCode Go model list, but provider behavior can vary, especially around streaming usage/token accounting.

Important Zen Limitation

OpenCode Zen support is partial.

This proxy currently works with Zen models that use the OpenAI-compatible /chat/completions endpoint.

Known Zen model categories that should work through /zen:

Known Zen model categories that do not work yet through this proxy:

Use /go for OpenCode Go. Use /zen only for Zen models listed as OpenAI-compatible chat models in the OpenCode Zen endpoint docs.

For Developers (OpenCode Cowork Proxy Worker)

Technically, this is a Cloudflare Worker gateway that lets Anthropic/Claude clients talk to OpenAI-compatible APIs, and lets OpenAI clients talk to Anthropic-compatible APIs.

The default upstream is OpenCode Go:

https://opencode.ai/zen/go/v1

This means Claude can be configured to use OpenCode Go models through this proxy without additional server-side configuration.

Claude / Anthropic SDK  ->  /v1/messages           ->  OpenAI-compatible upstream
OpenAI SDK              ->  /v1/chat/completions   ->  OpenAI-compatible upstream
OpenAI SDK              ->  /v1/chat/completions   ->  Anthropic upstream with x-upstream-format: anthropic

Detailed Claude Setup

Use Claude's Configure third-party Inference flow and add the Worker as a custom gateway.

Configure the gateway like this:

Do not include /v1/messages in the Claude base URL. Claude will call /v1/messages; the Worker handles that path.

Use /go for OpenCode Go subscription models. Use /zen only for OpenCode Zen models available through the OpenAI-compatible /chat/completions endpoint. Zen GPT /responses, Zen Claude /messages, and Zen Gemini model-specific endpoints are not supported yet.

Manual Model Setup

Claude may not discover the OpenCode Go models automatically. Add the model manually in Configure third-party Inference.

Common OpenCode Go model IDs:

For the latest list, see the OpenCode Go endpoint docs:

https://opencode.ai/docs/go/#endpoints

For OpenCode's own config files, model IDs use the opencode-go/<model-id> format. For Claude's third-party inference setup through this proxy, use the raw API model ID such as deepseek-v4-pro, kimi-k2.6, or qwen3.5-plus.

claude.json Example

You can also configure Claude with a claude.json gateway entry. Replace the Worker URL and API key with your own values.

{
  "inferenceProvider": "gateway",
  "inferenceGatewayBaseUrl": "YOUR_DEPLOYED_WORKER_URL/go",
  "inferenceGatewayApiKey": "YOUR_OPENCODE_GO_API_KEY",
  "inferenceGatewayAuthScheme": "x-api-key",
  "inferenceModels": [
    {
      "name": "glm-5.1"
    },
    {
      "name": "glm-5"
    },
    {
      "name": "kimi-k2.5"
    },
    {
      "name": "kimi-k2.6"
    },
    {
      "name": "deepseek-v4-pro"
    },
    {
      "name": "deepseek-v4-flash"
    },
    {
      "name": "mimo-v2-pro"
    },
    {
      "name": "mimo-v2-omni"
    },
    {
      "name": "mimo-v2.5-pro"
    },
    {
      "name": "mimo-v2.5"
    },
    {
      "name": "minimax-m2.7"
    },
    {
      "name": "minimax-m2.5"
    },
    {
      "name": "qwen3.6-plus"
    },
    {
      "name": "qwen3.5-plus"
    }
  ]
}

Deploy On Cloudflare

This project is intended to run as a Cloudflare Worker. Deploy it to Cloudflare using either the deploy button above or Cloudflare's Git-based Worker deployment flow.

Use these settings when connecting the repository in Cloudflare:

Do not deploy this as a normal Node.js web app. wrangler deploy builds and publishes the Worker from wrangler.toml.

Configuration

The Worker is zero-config by default. It forwards to OpenCode Go using OpenAI-compatible format. You can also route to OpenCode Zen by adding /zen to the Worker URL.

Optional request headers:

The API key is validated locally before any upstream call. Missing or short keys receive a 401 response.

Prefix routes:

API Endpoints

OpenAI SDK Usage

Point any OpenAI-compatible client at the gateway. By default, /v1/chat/completions passes through to OpenCode Go.

from openai import OpenAI

client = OpenAI(
    base_url="YOUR_DEPLOYED_WORKER_URL/v1",
    api_key="your-opencode-go-api-key",
)

response = client.chat.completions.create(
    model="deepseek-v4-pro",
    messages=[{"role": "user", "content": "Hello"}],
)

OpenAI SDK To Anthropic

Set x-upstream-format: anthropic and point x-upstream-url at an Anthropic-compatible API.

curl YOUR_DEPLOYED_WORKER_URL/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_ANTHROPIC_KEY" \
  -H "x-upstream-url: https://api.anthropic.com" \
  -H "x-upstream-format: anthropic" \
  -d '{"model":"claude-sonnet-4-20250514","messages":[{"role":"user","content":"Hello"}]}'

Translation Notes

The gateway handles:

• Anthropic Messages requests to OpenAI Chat Completions requests
• OpenAI Chat Completions responses to Anthropic Messages responses
• Tool calls and tool results in both directions
• Streaming SSE in both directions
• DeepSeek/OpenAI reasoning_content as Anthropic thinking blocks
• Prompt cache key injection for OpenAI-style prefix caching

Prompt Caching

When translating Anthropic to OpenAI, the gateway injects a prompt_cache_key derived from a hash of the system prompt. This keeps requests with the same system prompt routed to the same backend node when the upstream supports OpenAI-style prefix caching.

Cache hit tokens from OpenAI-compatible usage metadata are mapped back to Anthropic's cache_read_input_tokens field.

Development

npm install
npm test
npm run deploy -- --dry-run

Project structure:

src/
├── index.ts                          Main Worker router and auth gate
├── auth.ts                           API key extraction and validation
├── cache.ts                          Prompt cache key utilities
└── translate/
    ├── request/                      Request translators
    ├── response/                     Response translators
    └── stream/                       SSE stream translators
test/
├── auth.test.ts
├── cache.test.ts
├── index.test.ts
├── request.test.ts
├── response.test.ts
└── stream.test.ts

License

MIT. See LICENSE.