acp

/acp (bro)

All mechanics live in the bro CLI. This skill is policy only.

bro acp proxy -- <agent cmd> puts bro on the ACP wire (specs bro-rs8sp.md, bro-bhyo1.md): the client spawns bro as the agent, bro spawns the real agent, and every JSON-RPC message crosses untouched — requests, notifications, _-methods, _meta, and error envelopes, verbatim in both directions. The one rewrite is the seam: the session's first session/prompt gets ONE prepended text block carrying the same session-start + prompt-submit context bro hooks emits, probed inside session/new's cwd. Later prompts carry prompt-submit context only.

Command

Command	What it does
bro acp proxy -- <agent cmd…>	Foreground proxy — stdin/stdout IS the upstream wire. -- is mandatory; the tail is exec'd directly (no shell), env BRO_HOOKS=0 so the downstream tree never re-runs hooks. Exit 0 = client ended the wire; 1 = downstream died first; 2 = usage

Wiring a client

Point the client's "custom agent" at bro the same way it would name any ACP server:

• devin: devin acp is itself an agent — bro acp proxy -- devin acp chains bro in front of it for a Devin-driven session.
• kilo: bro acp proxy -- kilo acp.
• Zed / JetBrains / Neovim: add bro as an external agent with the same argv shape — the client's own config syntax for a stdio ACP server.

Run the proxy anywhere — the seam probes session/new's cwd, not the proxy's own, so a session opened in another repo gets THAT repo's context or nothing (fail-open, same as the hook).

What crosses the seam — and what doesn't

• Session context collects in-process (the hook collectors as a library — no bro hooks subprocess), once per session, on the first prompt only. A session/cancel landing while the seam collects answers the held prompt stopReason:'cancelled' — the wire never shows a prompt after its cancel.
• session/update chunks never pay probe cost — the seam maps to wire-level events, not deltas.
• Permission policy (bro-9qopj), tool-call guards and the stop gate (bro-u2eps), and agent mode (bro-tegz2) are separate beads — permission requests forward verbatim today.

Telemetry

• acp.proxy.session / acp.proxy.turn otel spans wrap each session and prompt; session/update feeds agentTurnPlane (by: 'acp proxy').
• An unbadged run (no BRO_AGENT_ID — a human driving the proxy) still journals: <git-common>/bro/proxy/acp-<session>.events.jsonl.