bop-on

# bop O(N) — keep loops linear When adding behavior to a per-card loop (dispatcher, merge-gate, reap, status), never introduce per-item syscalls. The loop body should do O(1) memory work per card; all I/O flushes once per iteration. ## Approved patterns ### 1. Collect then flush ```rust let mut events: Vec<Event> = Vec::new(); for card in cards { process(card); // existing work events.push(build_event(card)); // O(1) memory, no I/O } flush_events(&events); // one write, one POST ``` ### 2. Opt-in gate ```rust let enabled = lineage::is_enabled(); // check once for card in cards { process(card); if enabled { events.push(...); // zero work when disabled } } ``` ### 3. Defer to background ```rust let (tx, rx) = mpsc::channel(); std::thread::spawn(move || { for ev in rx { write(ev); } }); for card in cards { process(card); let _ = tx.send(build_event(card)); // non-blocking } ``` ## Anti-patterns — reject these in review | Anti-pattern | Why it's O(2N) | Fix | |---|---|---| | File append per card in loop | N extra fsync calls | Collect → flush | | `Command::spawn` per card | N fork+exec calls | Batch or defer | | Serialize JSON per card unconditionally | N allocs when no consumer | Opt-in gate | | HTTP POST per card | N network round-trips | Batch POST | | Re-read config file per card | N file reads | Cache at loop top | ## Where this applies in bop - `run_dispatcher()` — processes up to `max_workers` cards per iteration - `run_merge_gate()` — processes all done/ cards per iteration - `reap_orphans()` — scans all running/ cards - `print_state_group()` — reads all cards in a state dir for `bop status` - `cmd_doctor()` acceptance criteria lint — iterates pending/ cards ## COW note `fs::rename` is metadata-only on APFS/ext4/btrfs — no bytes copied, COW reflinks preserved. It's already O(1). Don't wrap it in anything that adds O(N) I/O.