provider

/provider (bro)

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

bro proxies the Anthropic Messages API: a claude pointed at a bro listener talks to the configured upstream through bro — the proxy owns auth (the client presents bro's session token; the upstream sees the real credential from the server env), never the protocol. SSE streams, tool_use, and /v1/models discovery all pass through untouched.

Two planes produce an endpoint:

• host listener — bro provider serve: user-scoped, repo-free, bound to the well-known port 4545 by default. Exactly one per provider state directory — provider.json.lock enforces it. The permanent wiring. State at $XDG_STATE_HOME/bro/provider.json (0600). There is no dedicated start step — bro provider ensure (the apiKeyHelper) resolve-or-spawns it on demand.
• repo serve — bro serve: the facade host; wires /v1/* too when the server env carries an upstream key (serve.json records provider: true). Repo-scoped, ephemeral port — the fallback and the per-run-port escape hatch (explicit ANTHROPIC_BASE_URL pin), not the everyday endpoint.

The /v1 plane itself is whichever plane is configured: a serve.backend /providers.<name> acp conductor (read from the global config layer — the spawning repo's config never leaks into a machine-level service) or the env-key byte-proxy to BRO_PROVIDER_UPSTREAM (default api.anthropic.com) with BRO_PROVIDER_API_KEY.

Commands

Command	What it does
bro provider serve [--port N]	Foreground host listener on 127.0.0.1 (default 4545). Refuses while another listener is live in the same provider state directory and when nothing is configured to serve (no serve.backend/providers.* in global config, no upstream key in env). Rarely invoked by hand — ensure spawns it.
bro provider ensure [--port N]	Resolve-or-spawn the host listener, print the session token — the apiKeyHelper. Probe → detached spawn → poll → token on stdout; failures exit 1 on stderr.
bro provider url	Print the endpoint ANTHROPIC_BASE_URL should point at
bro provider token	Print the session token — self-heals through the ensure path on a dead listener, same helper contract
bro provider env	Print export ANTHROPIC_BASE_URL=… + export ANTHROPIC_AUTH_TOKEN=… — eval "$(bro provider env)"-able; a comment carries the settings.json block
bro provider env --json	Print the ~/.claude/settings.json block verbatim — {"env":{"ANTHROPIC_BASE_URL":…},"apiKeyHelper":"bro provider ensure"}

Resolution — cwd-aware

url/token/env all pick the same endpoint:

1. ANTHROPIC_BASE_URL set in env → exact url match (localhost, default port, and trailing slash normalized — the path must match too: a base carrying one never selects a listener that serves root-anchored /v1/*) against the live host listener, then the cwd repo's live serve — the helper tracks the client's actual target, never guesses;
2. unset → the live host listener — one gateway per provider state directory;
3. else the cwd repo's live serve with the provider plane wired;
4. else exit 1 — a wrong token is worse than a nonzero exit.

The one-time wire

{
  "env": { "ANTHROPIC_BASE_URL": "http://127.0.0.1:4545" },
  "apiKeyHelper": "bro provider ensure"
}

in ~/.claude/settings.json — nothing else, ever. The first auth refresh after a boot spawns the listener; every claude (any repo, any pane) flows through the same one. The token stays dynamic — the helper resolves it per call from the live state file, so listener restarts never stale the client.

Trust boundary (same as serve)

Loopback bind only — 127.0.0.1, no --host. Every /v1/* request must present the session token as Authorization: Bearer or x-api-key (claude sends whichever its credential resolution produced); the 0600 state file means "can read the token" = same-UID local process. Loopback Host and Origin checks keep browsers out.