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OpenCode

Open-source AI coding agent — add AntSeed as a custom OpenAI-compatible provider.

Coding agentsOpenAI Chat Completions~3 min

OpenCode is an MIT-licensed terminal coding agent built on the Vercel AI SDK. It supports 75+ providers out of the box and lets you register custom ones via opencode.json.

AntSeed plugs in as a custom provider using the @ai-sdk/openai-compatible adapter — the same one OpenCode recommends for any OpenAI-compatible endpoint (LM Studio, llama.cpp, Atomic Chat, etc.). No environment variables, no ANTHROPIC_BASE_URL: the config lives in JSON.

Each model you want to use must be listed under models. The id has to match what the buyer proxy returns from GET /v1/models — i.e. a service id advertised by your currently-pinned peer.

Run AntSeed first

Every integration assumes a buyer proxy at http://localhost:8377. One-time setup, ~2 minutes.

Step 1

Install OpenCode

  • Install OpenCode
    npm install -g opencode-ai
  • Verify it runs
    opencode --version

Step 2

Point OpenCode at AntSeed

opencode.json (project root, or ~/.config/opencode/opencode.json for global)
{ "$schema": "https://opencode.ai/config.json", "provider": { "antseed": { "npm": "@ai-sdk/openai-compatible", "name": "AntSeed (peer-to-peer)", "options": { "baseURL": "http://localhost:8377/v1" }, "models": { "claude-sonnet-4-6": { "name": "Claude Sonnet 4.6 (via AntSeed)" }, "deepseek-v4-flash": { "name": "DeepSeek v4 Flash (via AntSeed)" }, "gpt-oss-120b": { "name": "gpt-oss 120B (via AntSeed)" } } } } }

Step 3

Pick a model

claude-sonnet-4-6claude-opus-4-7deepseek-v4-flashgpt-oss-120b

The keys under `models` must exactly match service ids returned by `curl http://localhost:8377/v1/models`. If your pinned peer doesn't advertise an id, OpenCode will list it but every call to it returns `404 model_not_found`.

The exact list of models depends on which peer you pin. Run antseed network browse or open the live network page to see what's available right now.

Verify

Test it

  • Confirm the proxy lists the same ids your config references
    curl -s http://localhost:8377/v1/models | jq '.data[].id'
    Example response
    "claude-opus-4-7" "claude-sonnet-4-6" "deepseek-v4-flash" "gpt-oss-120b"

    Add or remove entries under `models` in `opencode.json` so they match this list.

  • Launch OpenCode in your project
    opencode

    Inside the TUI, run `/models` and pick one of the AntSeed entries. OpenCode remembers your last selection per project.

How OpenCode talks to AntSeed

  • Wire format sent by OpenCode: OpenAI Chat Completions (hits /v1/chat/completions on the buyer proxy)
  • Best-fit services: any service whose protocols array contains openai-chat-completions. That's what the peer advertises as natively-supported — zero translation overhead, no transform edge cases.
  • How to check a peer: run antseed network peer <peerId> --json and look at matchingServices[].protocols for each model. The browse command shows the same data per peer in providerServiceApiProtocols.
  • What happens when protocols don't match: AntSeed's @antseed/api-adapter translates between OpenAI Chat Completions and the service's native protocol on the fly. So a request from OpenCode can still reach a service that only advertises anthropic-messages — just with a small transform step.
  • One known caveat: services whose only advertised protocol is openai-responses require streaming. If OpenCode sends a non-streaming request and the proxy routes it to one of those services, the call fails with HTTP 400: Stream must be set to true. Pick a service whose protocols includes openai-chat-completions (or another non-responses protocol) to avoid this.

If it goes wrong

Troubleshooting

  • AntSeed doesn't appear in `/connect` or `/models`OpenCode only loads providers declared in `opencode.json`. Make sure the file is in your project root (or `~/.config/opencode/opencode.json`) and that the JSON is valid — a stray comma silently disables the whole provider.
  • Model is listed but every call returns `model_not_found`The pinned peer doesn't advertise that service id. Run `antseed network peer <peerId>` to see what it actually offers, or pin a different peer.
  • OpenCode prompts for an API keyThe proxy ignores auth, but the AI SDK sometimes asks anyway. Either skip the prompt (press enter on empty input) or set `"apiKey": "antseed"` inside `options` in `opencode.json`.

Reference

Links

OpenCode docs → Custom providerOpenCode repo

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