quest: plan recording kix follow-up sessions in a PR comment

quest/m0/model-routing/README.md

@@ -80,4 +80,5 @@ are mostly judgment.
 - [Route by size](/quest/m0/model-routing/models.md) - `/quest-spawn` starts each quest on the first entry of its size's ranked list that can run
 - [Review score](/quest/m0/model-routing/review-score.md) - every `quest review` round scores the change out of 10
 - [Commits and PRs record their models](/quest/m0/model-routing/implementer.md) - commit trailers and PR records name each harness, model, and effort, and the PR's size
+- [kix records its follow-up sessions](/quest/m0/model-routing/kix-sessions.md) - kix `iterate` and `merge` jobs that change an existing PR record their `Implementer:` line in a PR comment
 - [moq-dev pins](/quest/m0/model-routing/pins.md) - moq-dev/moq and moq-dev/moq.pro bump their `quest` pin to pick up the routing

quest/m0/model-routing/kix-sessions.md

@@ -0,0 +1,54 @@
+# [S] kix records its follow-up sessions
+
+## Goal
+
+When a kix `iterate` or `merge` job publishes changes to an existing PR,
+kix posts or updates one PR comment carrying that session's `Implementer:`
+line (harness, model, and effort), so every session that changed the PR is on
+record. Whatever reads the PR's implementers reads the PR body's `## Models`
+section plus that comment: the `--exclude-model` rule in `quest context`'s
+Reviews section, so a local review never picks a model a kix session coded
+with, the [model check](/quest/m1/model-check.md), and
+[`quest usage`](/quest/m1/usage.md). The PR body and its `## Review` record
+stay untouched.
+
+## Plan
+
+Decided 2026-11-04 (user, /quest-complete follow-up of
+[moq-dev/quest#494](https://github.com/moq-dev/quest/pull/494)). #494 records
+each implementing session in the PR body's `## Models` section, and the kix
+runner adds its line when a job opens or updates a PR's text. But on an
+existing PR, kix `iterate` and `merge` jobs write no PR text (the runner's
+`deliver` sends no `pull` for them, `src/runner/job.ts`, so
+`cloudflare/src/jobs/publish.ts` never calls `GitHubService.deliver`), and
+editing the body would make the App its last editor, which voids the
+author's own `## Review` record (`cloudflare/src/github/review.ts`). These
+sessions are the second implementers the record exists to catch.
+
+- How should those sessions be recorded?
+  - ✅ A kix PR comment that the audits also read
+  - Rejected: editing only the body's `## Models` section and exempting such
+    edits from the review-record check; leaving them unrecorded
+- Which milestone?
+  - ✅ m0, in this epic beside the record it completes
+  - Rejected: m1
+
+Implementation guidance:
+
+- One comment per PR, found by a hidden marker and updated in place, with
+  one `Implementer:` line per session in the `## Models` line format.
+- Record a session when it first publishes changes, at a `checkpoint` as
+  well as at `deliver`, matching the rule that each session adds its line
+  when it first pushes; a merge job that only lands adds none. The runner
+  already computes the line for `deliver`, so it can send it with each
+  publication and let the Worker post it.
+- Readers take the marked comment only when a GitHub App wrote it, since
+  any commenter can copy a hidden marker.
+- Update `quest/m1/model-check.md` and `quest/m1/usage.md` to read the
+  comment too, and `quest context`'s `## Models` rule and its
+  `--exclude-model` rule ("each implementing model the PR body records")
+  to name it.
+
+## Required
+
+- [Commits and PRs record their models](/quest/m0/model-routing/implementer.md) - this builds on its `## Models` record and the runner's reporting