review: M6a subagents

docs/implementer-lessons.md

@@ -33,9 +33,9 @@ How it is used:
 | I15 | Never write the model's chat-template tags out whole (the think and tool-call tags, the angle-bar turn markers) in code, comments, commands or the log. Build them from pieces (`concat!("<", "think")`) and name them in words. Text holding them turns into the model's own control tokens when it reads it. | M5a task 04: the given test held the tags; Ornith's reasoning ended at the test file's closing think tag, and it lost track of the file and made no change. `docs/research/2026-09-24-chat-template-tokens.md`. | yes | M5a tasks 05 to 22: not seen again. |
 | I16 | When a test outside your task fails, check once whether it fails without your change (stash, run, unstash), then stop and report both results. Do not keep experimenting, and never add a file the task does not list, not even a temporary one. | M5a task 21: the session did the check, then spent about 80 minutes on experiments and wrote two diagnostic test files into `crates/bxctl/tests/` until the owner stopped the run; the cause was outside the repository (review finding 4). M5a task 16 did it right: one check, its log row, a stop. | yes | M5c-1: the stash left the new untracked tests behind and a baseline printed no total (task 15; now `git stash -u` in AGENTS.md, T53); the two flaky tests were rerun and named, not stopped on (now an exception for a test the README lists, T52). |
 | I17 | Write your log row from `git diff` after staging, naming only what the diff shows. A row written from memory describes what you meant to do. | M5a task 10's row describes checks that are not in `serve.rs`; task 13's says two runbook fragments were copied, and neither was (review findings 5 and 6 of 2026-09-24). | yes | M5c-1: task 10 logged one gate run and ran three, task 12 logged three and ran four and "Deviations: none" after anchoring an edit on its own line, and task 14's row blames the task for its own spacing error. M5c-2: every row's first gate is `pass`; task 01 still ran the gate twice, and every session ran `cargo test --workspace` after `gate: ok` only to count (T59). |
-| I18 | After `gate: ok`, do not run `cargo test --workspace` (or the gate) only to count tests. The gate's total is the count. If HEAD already has this task's commit and a `done` row, stop; do not start the task again. | M5c-2: every session re-ran the workspace tests after a passing gate (T50 still driving extra work). Task 05's run log is a resume after HEAD was already at task 12; Laguna did not re-commit, and the original transcript was truncated. | yes | M5d-1: tasks 03, 07 and 08 ran the gate two or three times with first-gate pass. M5d-2: task 04 ran the gate twice with first-gate pass. |
+| I18 | After `gate: ok`, do not run `cargo test --workspace` (or the gate) only to count tests. The gate's total is the count. If HEAD already has this task's commit and a `done` row, stop; do not start the task again. | M5c-2: every session re-ran the workspace tests after a passing gate (T50 still driving extra work). Task 05's run log is a resume after HEAD was already at task 12; Laguna did not re-commit, and the original transcript was truncated. | yes | M5d-1: tasks 03, 07 and 08 ran the gate two or three times with first-gate pass. M5d-2: task 04 ran the gate twice with first-gate pass. M6a: no; five tasks, one gate each, first-gate pass. |
 | I19 | Add the log row immediately under the table header (newest first). Do not insert it by date among older rows. | M5d-1 task 06: the row was inserted after M4b/03. | yes | M5d-2: task 04's commit duplicated 03's identical `done` row. |
-| I20 | After a turn, do every bookkeeping step the task lists, including when the outcome is `Err`, unless the task says only on Ok. Gating `last_heartbeat` on success is a judgement the task did not ask for. | M5d-2 finding 1: heartbeat sets `last_heartbeat` and pushes `Heartbeat` only on `outcome.is_ok()`. | yes | |
+| I20 | After a turn, do every bookkeeping step the task lists, including when the outcome is `Err`, unless the task says only on Ok. Gating `last_heartbeat` on success is a judgement the task did not ask for. | M5d-2 finding 1: heartbeat sets `last_heartbeat` and pushes `Heartbeat` only on `outcome.is_ok()`. | yes | M6a: not exercised. |
 
 ## Tips for writing tasks