{
  "status": "complete",
  "file": "crates/spt-daemon/src/broker.rs",
  "markers": [
    "CTRL_WRITE_WAIT: conn_id, sid, epoch, label=seq:<n>|control:<kind>, bytes_len, elapsed_us",
    "CTRL_WRITE_LOCKED: conn_id, sid, epoch, label, bytes_len, wait_us, elapsed_us",
    "CTRL_WRITE_DONE: conn_id, sid, epoch, label, bytes_len, wait_us, write_us, result=ok|error|superseded, elapsed_us",
    "PROBE_ENQUEUE: endpoint, ticket, accepted, result=accepted|dropped, bytes_len, elapsed_us",
    "PROBE_WRITE_START: endpoint, ticket, bytes_len, elapsed_us",
    "PROBE_WRITE_DONE: endpoint, ticket, bytes_len, write_us, result=ok|error, elapsed_us",
    "INJECT_SETTLE_TIMEOUT (gated extension): endpoint, baseline_high_water, current_high_water, last_probe_ticket, last_probe_accepted, elapsed_us"
  ],
  "signature_propagation": [
    "handle_conn mints AtomicU64 conn_id",
    "handle_conn -> dispatch_spawn -> OutputLog::become_controller -> controller_writer",
    "handle_conn -> dispatch_subscribe -> OutputLog::resolve_subscribe -> OutputLog::become_controller -> controller_writer",
    "ControllerSink retains conn_id",
    "InputWriter::spawn passes endpoint to input_writer; settle_before_inject uses InputWriter::enqueue_probe with tagged InputRecord"
  ],
  "behavior_guards": [
    "SPT_RCA_PTY_TRACE=1 is the sole observation gate",
    "No payload/user bytes are emitted; only lengths, IDs, endpoint, timing, and result labels",
    "Ungated controller path adds only a cached LazyLock gate read; handle_conn adds one relaxed atomic increment; ungated probes retain the original nonblocking enqueue/write behavior"
  ],
  "verification": "cargo check -p spt-daemon passed"
}