@fulcrum-agent-os/opencode-plugin

opencode plugin for the Fulcrum Agent OS — injects the canonical Fulcrum-first system rider into every LLM turn, verifies its integrity, and emits telemetry when the primary injection path silently fails.

Install

// opencode.jsonc
{
  "plugin": ["@fulcrum-agent-os/opencode-plugin"]
}

Bun auto-installs the package at opencode startup; no separate npm install step.

Manual / dogfood install (clone the Fulcrum repo instead):

// opencode.jsonc
{
  "plugin": ["./plugins/fulcrum.ts"]
}

What it does

• System rider — reads .opencode/rules/fulcrum-rule-*.md (or the canonical agent-integration/rules/ in dogfood mode), concatenates them sorted by filename, and prepends the result inside a <fulcrum-system-rider> fence on every LLM call via experimental.chat.system.transform.
• Integrity chain — computes SHA-256 of the rider and verifies against a sibling .ridersum file if present. Mismatch logs a warning but never blocks the agent (AD-3 fail-open).
• Fallback telemetry — if experimental.chat.system.transform fires zero times in a session, the session.idle handler emits an opencode_rider_never_injected graph event so the measurement harness can detect silent primary-path failures.
• Tool policy bridge — per-tool tool.execute.before + tool.execute.after hooks shell to fulcrum hook auto for secret scanning, CoS team-invoke guards, and post-tool memory writes.
• Workspace snapshot — appends live get_workspace_status output (active / blocked run counts) after the rider.
• Shell env — exposes FULCRUM_WORKSPACE_ID / FULCRUM_PROJECT_ID so subprocesses can find the workspace without reading config.

Configuration

| Env var | Default | Effect | |---|---|---| | FULCRUM_NO_RECALL_NUDGE | unset | Set to 1 to suppress the Fulcrum-first stderr nudge while keeping telemetry opt-out events logged. | | FULCRUM_BIAS_VARIANT | auto | auto (default): try passive injection, fall back to nudge. A: nudge-only. B: alias for auto. | | OPENCODE_SESSION_ID | (injected by opencode) | Session identifier passed to every Fulcrum hook invocation. |

License

MIT — see LICENSE.