# M2b task 11: four small fixes (review follow-up)

**Branch:** `m2b` (run `git switch m2b`; `git status --short` must be empty, otherwise stop)
**Commit subject:** `Fix four review findings: busy release, poison recovery, core.md errors, chat loop`

## Goal

The M2b review found four small defects. Two have a test to copy in; two are rules to apply. None
changes an interface.

## Files

- Copy (replacing the old ones): `crates/loopd/tests/baseline.rs`, `crates/bxctl/tests/chat.rs`
- Modify: `crates/loopd/src/channel.rs`, `crates/loopd/src/baseline.rs`,
  `crates/bxctl/src/chat.rs`, `crates/bxctl/src/main.rs`, `docs/implementer-log.md`

## The four fixes

1. **`channel.rs`: release the session before *every* final frame.** Task 07 said to drop the
   busy guard before `turn_done` or the turn's error, and that is done. But the error frames for
   a session that cannot be opened or created (`no_such_session`, `session_exists`, `internal`)
   are still sent while the session is marked busy. `bxctl chat --session <new id>` reads
   `no_such_session` and at once sends the same turn again with `resume: false`, so it can be
   answered `session_busy` by a server thread that has not returned yet. Drop the guard before
   each of those three writes. The rule: the last frame of a connection is never sent while the
   session is busy.
2. **`channel.rs`: a poisoned lock must not leave a session busy forever.** The guard's `Drop`
   does `if let Ok(mut busy) = self.ctx.busy.lock()`, which skips the removal when the lock is
   poisoned. Recover it with `unwrap_or_else(|p| p.into_inner())`, as `handle` already does.
3. **`baseline.rs`: a `memory/core.md` that exists but cannot be read is an error.** Today
   `if let Ok(text) = read_to_string(..)` treats an unreadable file like a missing one, so a
   session starts without the memory the owner curated, and nothing says so. If the file exists,
   a read failure is `BaselineError::Read(path, e)`. A missing file is still fine.
4. **`bxctl`: the interactive loop goes on after a failed turn, and `new_session_id` has no
   `expect`.** The spec says "A failed turn prints `bxctl: <error>` and the loop goes on"; today it
   exits 1. Report the error and continue; the session exists, so the next line resumes it. And
   `AGENTS.md` forbids `expect` in library code: replace the two in `new_session_id` with
   `unwrap_or_default()` for the clock and `unwrap_or_else` with a fixed valid id for the
   `SessionId` (it cannot fail, but the type must not be forced).

## Steps

- [ ] **1. Copy.**

```sh
git switch m2b
cp docs/plans/M2b/files/crates/loopd/tests/baseline.rs crates/loopd/tests/
cp docs/plans/M2b/files/crates/bxctl/tests/chat.rs crates/bxctl/tests/
```

- [ ] **2. See them fail.** `cargo test -p loopd --test baseline`: 1 of 7 fails,
  `an_unreadable_core_memory_file_is_an_error`. `cargo test -p bxctl --test chat`: 1 of 12 fails,
  `interactive_mode_survives_a_failed_turn`.
- [ ] **3. Make the four fixes.** Run `cargo fmt --all`.
- [ ] **4. See them pass.** `cargo test -p loopd --test baseline --test channel -p bxctl`.
  Expected: 7, 6 and 12 passed. Run the `channel` tests ten times in a row.
- [ ] **5. Run the gate.** `make gate`. Expected last line: `gate: ok`.
- [ ] **6. Log and commit.**

```sh
git add crates/loopd crates/bxctl docs/implementer-log.md
git commit
```

## Done when

- `make gate` prints `gate: ok` with 219 tests.
- `grep -n "expect(" crates/bxctl/src/chat.rs` prints nothing.
- `grep -c "drop(held)" crates/loopd/src/channel.rs` prints 4 (or the guard is scoped so that
  every final frame is written after it is gone).

## Stop and report if

- `interactive_mode_survives_a_failed_turn` cannot pass without changing what `--say` does.