opencode consumes RAC on two surfaces — a generated context file opencode reads, and the lore MCP server it connects to. A stranger can reproduce this from the file alone.

pip install rac-core   # the `rac` CLI and the `lore` MCP server

A repository with a RAC corpus under decisions/ (run decided quickstart, or use this repository's own decisions/).

decided export decisions/ --agent-rules

This writes several agent-context files; opencode reads AGENTS.md at the project root natively as its instructions. No extra step — the recorded decisions reach opencode's agent as instructions. The managed block keeps your own content intact; re-run on change (decided export decisions/ --agent-rules --check fails CI on drift).

opencode keys MCP servers under an mcp block, with a local (stdio) server given as a command array. Add it to opencode.json in the repo root (a sample is in opencode.example.json):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "asdecided": {
      "type": "local",
      "command": ["rac", "mcp", "--root", "."],
      "enabled": true
    }
  }
}

• Project: opencode.json in the repo root (commit it to share with the team).
• Global: ~/.config/opencode/opencode.json — use an absolute --root path.
• Or run opencode mcp add and follow the prompts; opencode mcp list shows the server and its connection status.

It exposes the five read-only lore tools (get_summary, search_artifacts, get_artifact, get_related, find_decisions); the server re-reads the corpus on every call and never writes to the repo.

RAC supplies context and enforces after the edit (ADR-067). There is no platform API to veto an opencode agent edit before it lands, so opencode relies on the post-edit guard: decided validate / decided relationships --validate and the GitHub Action / pre-merge gate, the same as any contributor. (A pre-edit veto is Claude-Code-specific — see examples/claude-code/.)

Run the bundled grounding demo — same task twice, once unconnected and once with lore connected — and watch the connected run respect a recorded decision the unconnected run violates: examples/guide/.

• Engine half — mechanically verified (2026-07-04). The decided-mcp invocation this recipe prescribes was smoke-tested over stdio against examples/guide/: the five lore tools respond and search_artifacts / get_artifact / get_related return the grounding decision. This is the RAC-owned half every recipe shares.
• Harness half — not yet verified. Running the grounding demo through opencode itself (config parsing plus a live agent) needs the released client and an API key — a human/CI step. Until it is done, this recipe keeps the verify against marker below and stays out of docs/ecosystem.md.