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OpenCode Zen exposes its “Go” subscription models behind an OpenAI-compatible API. GoModel ships a native opencode_go provider that defaults the base URL, so you only need an API key.

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Configure

Or in config.yaml:
The default base URL is https://opencode.ai/zen/go/v1. Authentication uses Authorization: Bearer <api_key> with the key generated in the OpenCode Zen console.

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Models

GET /v1/models proxies OpenCode Zen’s model list, exposing IDs such as glm-5.1, kimi-k2.7-code, deepseek-v4-pro, and mimo-v2.5-pro. Restrict the advertised set with a configured list when you only want a subset:

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Endpoints

OpenCode Zen serves most models on OpenAI-style /chat/completions (Bearer auth) and a few models only on the Anthropic-native /messages endpoint (x-api-key auth). GoModel routes per model:
  • OpenAI-style models (GLM, Kimi, DeepSeek, MiMo, MiniMax, most Qwen) go to /chat/completions. /models and /v1/responses (translated to chat completions) use the same path.
  • Anthropic-only models are translated to the Anthropic Messages dialect and sent to /messages, mirroring how GoModel already serves native Anthropic. Both paths normalize to the same OpenAI-compatible response, so clients see one consistent surface regardless of which model they pick — whether they call /v1/chat/completions or /v1/messages.
The set of /messages-only models is currently maintained manually (default: qwen3.7-max) because OpenCode Zen does not yet expose per-model endpoint metadata. Override it when needed:
This manual split is temporary and will be replaced by metadata-driven routing once the upstream model list distinguishes endpoints.

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Session header

OpenCode Zen asks every client to send an x-opencode-session header so it can route one conversation to the same upstream and keep its prompt cache warm. Upstream has announced that requests without it may start failing. GoModel adds the header to every OpenCode Go request by default, on both the /chat/completions and /messages paths, using the first available value:
  1. An x-opencode-session header sent by the client (OpenCode itself, pi, and other tools that speak OpenCode Zen’s dialect) is forwarded verbatim.
  2. Otherwise the session GoModel detected through session keeping: OpenCode’s X-Session-Id, Claude Code’s session id, a session body field, or the content-derived auto-… id for agents that send no signal at all.
A request with no detectable session is sent without the header. GoModel also identifies itself with x-opencode-client (forwarding the client’s own value when present, gomodel otherwise) and a gomodel/<version> User-Agent, as the upstream usage guidelines require. Disable session forwarding only if upstream asks you to:

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Reasoning

Some OpenCode Zen models always think and reject requests that leave the reasoning parameter out:
GoModel therefore sends reasoning_effort: "low" on /chat/completions when a request carries no reasoning parameter at all. Models that ignore the parameter are unaffected. Raise the default per deployment:
Set it to none (or off) to inject nothing and forward requests untouched. Clients keep control when they ask for reasoning themselves: nothing is injected over an explicit reasoning.effort or a top-level reasoning_effort. GoModel’s recognized effort levels are mapped to their nearest equivalent in the low / high / max set OpenCode Zen accepts: Any other value (turbo, say) is forwarded unchanged for the upstream to judge. reasoning.effort is GoModel’s canonical field, so a request that sets both it and a top-level reasoning_effort is sent with the mapped reasoning.effort — the same precedence every other GoModel provider applies. Models routed to /messages use the Anthropic thinking dialect instead and are not affected by this mapping.

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Not supported

  • Embeddings (returns invalid_request_error).
Last modified on September 3, 2026