docs: M5d-2: read only the implementer-log header

Task 06 opened the whole implementer log (~360 kB) after reading supporting
modules; OpenCode returned "Context size has been exceeded" and made no
commit. AGENTS.md and tasks 06-10 now say to read the first 12 lines only.

Co-Authored-By: Grok 4.6 <noreply@x.ai>

AGENTS.md

@@ -9,7 +9,9 @@ Unix sockets. You are implementing it one task at a time.
    nothing else. Do not start the next task.
 2. Do the steps in order. Where a step shows a command and its expected output, run it and compare.
 3. Do not read `docs/design.md` or other plans unless the task tells you to. The task file quotes
-   what you need.
+   what you need. Do not read `docs/implementer-log.md` until the log-and-commit step, and then
+   only the first 12 lines (the title through the header row). The rest of that file will fill
+   the session.
 4. If something in the task is impossible, contradictory, or fails twice in the same way, **stop**.
    Do not improvise, do not change a test, do not weaken a check. Add your row to
    `docs/implementer-log.md` with status `stopped`, say what you tried and what happened, commit
@@ -97,7 +99,7 @@ These come from defects found in review. The evidence is in `docs/implementer-le
   anchor the edit on another line.
 - Write your log row from `git diff` after staging, naming only what the diff shows.
 - Add the log row immediately under the table header (newest first). Do not insert it by date
-  among older rows.
+  among older rows. Read only the first 12 lines of `docs/implementer-log.md` to do that.
 - After `gate: ok`, do not run `cargo test --workspace` only to count tests. If HEAD already has
   this task's commit and a `done` row, stop.
 
@@ -131,10 +133,11 @@ Useful while working: `cargo test -p <crate> --test <file>` runs one test file,
 
 ## The implementer log
 
-Before you commit, add one row immediately under the header of the table in
-`docs/implementer-log.md` (newest first) and include the file in the commit. Do not insert the
-row by date among older rows. Be honest: the log is how the owner judges the process, and a wrong
-row is worse than a bad one.
+Before you commit, read only the first 12 lines of `docs/implementer-log.md` (title through the
+header row). Insert one row immediately under the header (newest first) and include the file in
+the commit. Do not insert the row by date among older rows. Do not read the rest of the file: it
+is large enough to fill the session. Be honest: the log is how the owner judges the process, and
+a wrong row is worse than a bad one.
 
 | Column | What to write |
 |---|---|

docs/implementer-lessons.md

@@ -101,6 +101,7 @@ How it is used:
 | T59 | After `gate: ok`, the task is done counting. Do not tell the implementer to run `cargo test --workspace` (or the gate) again only to compare a number. AGENTS.md already forbids a second gate "only to count"; say the same of the workspace test run. | M5c-2: all twelve sessions ran `cargo test --workspace` after a passing gate to rediscover the total, even with T50's wording in the task. |
 | T60 | The driver must not truncate a task's run log, and must not start a task whose commit and `done` row are already in HEAD. A power-loss resume continues the existing log file; it does not open it for write from offset zero, and it skips a task that is already committed. | M5c-2 task 05: `.state/runs/M5c2/05-memoryd-honcho-readers.log` is four `=== …` resume sections after HEAD was at task 12; the original transcript is gone. Commit `b370c60` was already complete. |
 | T61 | Name where the log row goes: immediately under the header, newest first. The implementer otherwise inserts by date among older rows. | M5d-1 task 06. |
+| T62 | The implementer log is hundreds of kilobytes. A task that needs a row must say to read only the first 12 lines (title through the header). Reading the whole file exceeds the session context and the driver reports "made no commit". | M5d-2 task 06: after reading the task and supporting modules it opened `docs/implementer-log.md` and OpenCode returned `Context size has been exceeded.`; HEAD did not move. |
 
 ## What worked and should be kept
 

docs/plans/M5d2/06-loopd-scheduler-heartbeat.md

@@ -38,6 +38,12 @@ Tests call `tick(ctx, now)` with injected time. No sleeps (T27).
   `crates/loopd/src/main.rs`, `docs/implementer-log.md`.
 - Do not touch: any other file.
 
+**Read only what the step names.** Step 1 is the `cp`. Do not open `docs/implementer-log.md`,
+`docs/runbook.md`, or `crates/loopd/src/{turn,session,compact,baseline,config}.rs` to start.
+The facts table is complete. At step 7, read only the first 12 lines of
+`docs/implementer-log.md` (title through the header row) and insert the new row immediately
+under the header. The rest of that file fills the session (~360 kB).
+
 ## Facts you need
 
 - **`Context::hold`.** Same insert as `handle`: if the id is already in `busy`, `Err(Busy)`;
@@ -199,7 +205,8 @@ pass so it runs once.
 - [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, timeout 600000 ms. Last line
   `gate: ok`. Test count **1551** (1545 before, plus 6). After `gate: ok`, do not add up
   `test result:` lines.
-- [ ] **7. Log and commit.** Task cell `M5d2/06-loopd-scheduler-heartbeat`. Stage with
+- [ ] **7. Log and commit.** Task cell `M5d2/06-loopd-scheduler-heartbeat`. Read only the first
+  12 lines of `docs/implementer-log.md`; insert the row under the header. Stage with
   `git add crates/loopd docs/runbook.md docs/implementer-log.md Cargo.lock`, then commit as
   `AGENTS.md` says.
 

docs/plans/M5d2/07-loopd-scheduler-cron.md

@@ -28,6 +28,9 @@ is not busy). Speaker `None`. Same time-line prefix as heartbeat.
 - Modify: `crates/loopd/src/scheduler.rs`, `docs/implementer-log.md`.
 - Do not touch: any other file.
 
+**Read only what the step names.** Step 1 is the `cp`. At the log step, read only the first 12
+lines of `docs/implementer-log.md`. Do not load the rest of that file.
+
 ## Facts you need
 
 - **Load.** `jobs::load(&ctx.cfg.paths.home.join("jobs"))`. On `Err`, log `loopd: {e}` and
@@ -84,7 +87,8 @@ Do not change heartbeat behaviour. Do not add a sleep.
 - [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, timeout 600000 ms. Last line
   `gate: ok`. Test count **1557** (1551 before, plus 6). After `gate: ok`, do not add up
   `test result:` lines.
-- [ ] **7. Log and commit.** Task cell `M5d2/07-loopd-scheduler-cron`. Stage with
+- [ ] **7. Log and commit.** Task cell `M5d2/07-loopd-scheduler-cron`. Read only the first 12
+  lines of `docs/implementer-log.md`; insert the row under the header. Stage with
   `git add crates/loopd docs/implementer-log.md Cargo.lock`, then commit as `AGENTS.md` says.
 
 ## Done when

docs/plans/M5d2/08-loopd-tool-summary.md

@@ -232,7 +232,8 @@ Facts). The `Err(TurnError::SessionFull)` arm gets the same `missing` call befor
 - [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, timeout 600000 ms. Last line
   `gate: ok`. Test count **1563** (1557 before, plus 6). After `gate: ok`, do not add up
   `test result:` lines.
-- [ ] **7. Log and commit.** Task cell `M5d2/08-loopd-tool-summary`. Stage with
+- [ ] **7. Log and commit.** Task cell `M5d2/08-loopd-tool-summary`. Read only the first 12
+  lines of `docs/implementer-log.md`; insert the row under the header. Stage with
   `git add crates/loopd config/summarise.md docs/implementer-log.md Cargo.lock`, then commit
   as `AGENTS.md` says.
 

docs/plans/M5d2/09-memoryd-summary-index.md

@@ -119,7 +119,8 @@ results are indexed. A comment that does not fit its code: stop.
 - [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, timeout 600000 ms. Last line
   `gate: ok`. Test count **1568** (1563 before, plus 5). After `gate: ok`, do not add up
   `test result:` lines.
-- [ ] **7. Log and commit.** Task cell `M5d2/09-memoryd-summary-index`. Stage with
+- [ ] **7. Log and commit.** Task cell `M5d2/09-memoryd-summary-index`. Read only the first 12
+  lines of `docs/implementer-log.md`; insert the row under the header. Stage with
   `git add crates/memoryd docs/implementer-log.md Cargo.lock`, then commit as `AGENTS.md`
   says.
 

docs/plans/M5d2/10-memoryd-tiers.md

@@ -228,7 +228,8 @@ Do not edit `cli_memory.rs`. This file is the M5c pin of the same USAGE string.
 - [ ] **6. Run the gate.** `cargo fmt --all`, then `make gate`, timeout 600000 ms. Last line
   `gate: ok`. Test count **1574** (1568 before, plus 6). After `gate: ok`, do not add up
   `test result:` lines.
-- [ ] **7. Log and commit.** Task cell `M5d2/10-memoryd-tiers`. Stage with
+- [ ] **7. Log and commit.** Task cell `M5d2/10-memoryd-tiers`. Read only the first 12 lines of
+  `docs/implementer-log.md`; insert the row under the header. Stage with
   `git add crates/bxcore crates/memoryd crates/bxctl config/jobs docs/implementer-log.md
   Cargo.lock`, then commit as `AGENTS.md` says.