boxmaker/docs/plans/M5d2/01-loopd-session-slot.md

# M5d-2 task 01: `run_turn` sends `session.slot()`

**Branch:** `m5d2`. Check it: `git branch --show-current` prints `m5d2` and `git status --short`
is empty; otherwise stop. Never switch branch.
**Commit subject:** `loopd: live turns use the session's slot`
**Log row:** the Task cell is `M5d2/01-loopd-session-slot`.

## Goal

Heartbeat and cron run on the background slot (spec 4). Live Mattermost and `bxctl chat`
sessions keep `cfg.slots.main`. Today `run_turn` always sends `slots.main`. This task makes it
send `session.slot()`: the slot stored on that session's `SessionStart` (M5d-1 task 02).

Nothing else changes. Compaction's summary call already uses `slots.background`. The scheduler
does not exist yet.

## Every place that changes

| Place | What happens there |
|---|---|
| `crates/loopd/src/turn.rs` | `ChatRequest.slot` is `session.slot()` (edit T1) |
| `crates/loopd/tests/session_slot.rs` | new, given |
| everything else | **no change**: not `session.rs`, not `compact.rs`, not channel |

## Files

- Copy, from `docs/plans/M5d2/files/` (the same path under it): the new test
  `crates/loopd/tests/session_slot.rs`.
- Modify: `crates/loopd/src/turn.rs`, `docs/implementer-log.md`.
- Do not touch: any other file.

## Facts you need

- **`Session::slot()`** returns the `u32` stored on create / on the current epoch's
  `SessionStart`. It is already `pub` (M5d-1 task 02).
- **`messages_with_carry`** stays as it is. Only the `slot:` line changes.
- **Existing turn tests** create sessions with `cfg.slots.main` (0). They still send 0.
- The items the edits use. This table is complete.

  | Item | What it does |
  |---|---|
  | `Session::slot` | the live slot for this session |
  | `ChatRequest.slot` | becomes `id_slot` on the wire |

## The edits, exactly

Each quoted "before" block occurs exactly once after M5d-1 task 08.

### `crates/loopd/src/turn.rs`

**T1.** The lines

```rust
        let request = ChatRequest {
            slot: rt.cfg.slots.main,
            messages: messages_with_carry(baseline, session.records(), session.carry()),
            tools: baseline.tools.clone(),
            thinking: true,
        };
```

become

```rust
        let request = ChatRequest {
            slot: session.slot(),
            messages: messages_with_carry(baseline, session.records(), session.carry()),
            tools: baseline.tools.clone(),
            thinking: true,
        };
```

## Steps

- [ ] **1. Copy the given test.** From the repository root, one command:

  ```sh
  cp docs/plans/M5d2/files/crates/loopd/tests/session_slot.rs crates/loopd/tests/
  ```

  Then `git status --short` lists one new file, `crates/loopd/tests/session_slot.rs`.
- [ ] **2. See it fail.** `cargo test -p loopd --test session_slot`, with a shell timeout of
  600000 ms: the four tests compile (they call `session.slot()`, which exists) and three fail.
  `a_session_created_on_the_background_slot_sends_that_slot` fails: `id_slot` is `0`, not `1`.
  `a_main_slot_session_still_sends_main` passes. `the_request_slot_follows_session_start_not_the_config_main`
  fails: `id_slot` is `0`, not `7`. `a_heartbeat_turn_between_two_main_turns_does_not_change_the_main_prefix`
  fails: the heartbeat request's `id_slot` is `0`, not `1`.
- [ ] **3. The edit.** Make edit T1. `cargo check -p loopd` prints no error and no warning.
- [ ] **4. The tests.** `cargo test -p loopd --test session_slot --test turn --test channel
  --test compact_turn`: every test passes, 4 in `session_slot` and the others as before.
- [ ] **5. Check.** `git diff --stat` lists exactly `crates/loopd/src/turn.rs`.
- [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, with a shell timeout of 600000 ms.
  Expected last line: `gate: ok`. The test count is **1512** after this task, 1508 before it,
  and the 4 new ones are the tests of `session_slot.rs`. To count, add up the `N passed` of
  every `test result:` line the gate's `cargo test --workspace` printed, and add 1. Never run
  the gate again only to count.
- [ ] **7. Log and commit.** Add your row to `docs/implementer-log.md`; its Task cell is
  `M5d2/01-loopd-session-slot`. Stage with
  `git add crates/loopd docs/implementer-log.md Cargo.lock`, then commit as `AGENTS.md` says.
  `Cargo.lock` does not change in this task; the `git add` is harmless.

## Done when

- `make gate` prints `gate: ok` with 1512 tests.
- `git diff HEAD~1 --stat` lists only `crates/loopd/src/turn.rs`,
  `crates/loopd/tests/session_slot.rs` and `docs/implementer-log.md`.

## Stop and report if

- The branch check at the top fails.
- A "before" block is not in its file exactly as shown, or is there more than once.
- Step 2 shows a different result: the tests do not compile, or a different assertion fails.
- `cargo check` in step 3 prints an error or a warning. Quote it, and stop.
- A test fails in step 4. Do not change the test: stop, and give the failing tests' names and
  their messages.
- The fix seems to need a change anywhere else. It does not; stop and say why you think so.
- A test outside `session_slot.rs` fails in the gate: check once whether it fails without your
  change (`git stash -u`, run it, `git stash pop`), then stop and report both results.
- The gate passes with a count other than 1512.

## What the given tests pin

A session created with `cfg.slots.background` sends that slot; one created with `cfg.slots.main`
still sends main; a session created with slot `7` sends `7` even when `cfg.slots.main` is `0`; a
heartbeat turn between two main turns does not change the main session's message prefix.