feat(opencode): forward Claude Code session ID as x-opencode-session

[alecchen]

What

OpenCode Go uses an x-opencode-session header to group requests by conversation, and has said requests without it may error after 09/06. Claude Code 2.1.259 already sends the conversation UUID as x-claude-code-session-id on every /v1/messages request. The proxy was dropping that header. This change forwards it verbatim to OpenCode Go.

The value is stable across turns in one conversation and differs between conversations. It is the same UUID Claude Code uses for its local transcript.

Design

• Resolve the inbound header once in HandleMessages, right after the X-Request-ID block and before any dispatch. Carry it on context.Context via core.WithSessionID / SessionIDFromContext, so every provider call and every fallback attempt sees the same value.
• Set x-opencode-session in every OpenCode Go request builder: the provider's executeAnthropic, streamAnthropic, and doRequest (chat and Responses), plus the legacy client's ChatCompletion, SendAnthropicRequest, ResponsesCompletion, and GeminiCompletion.
• OpenCode Go only. Zen, Bedrock, and OpenRouter are untouched; the legacy client guards on config.ProviderOpenCodeGo.
• Missing inbound header falls back to a per-request UUID, so the upstream header is always present. No hashing, no proxy state, no mapping.
• The inbound value is forwarded verbatim, with no truncation or validation.

Tests

• Provider tests cover the Go chat, anthropic, and responses wire formats, for execute and stream. An empty context omits the header. Zen and Bedrock confirm it stays off those providers.
• Handler tests cover streaming and non-streaming propagation, same and different inbound sessions, the UUID fallback, and fallback attempts sharing one session. A fake provider confirms the context reaches Stream. A Zen request omits the header end to end.
• Client tests extend the OpenRouter attribution table with x-opencode-session absent, and check opencode-go sets it while opencode-zen does not.

go test -race ./... passes across all packages. make lint and gofmt are clean.

🤖 Generated with Claude Code