quest: plan resending sessions once their branch's PR opens

quest/m0/benchmark/resend-sessions.md

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+# [M] Resend a session once its branch's PR opens
+
+## Goal
+
+A session whose last stop came before its branch's PR opened reaches Kixel
+Code's store with that PR in its record's `pulls`, so the PR's cost and
+time count it. Today the sender uploads such a session once with
+`pulls: []` and settles its queued stop, so it is never rebuilt. `quest
+start` opens the PR at claim time, so this mostly hits ad hoc sessions
+outside quests.
+
+Check: an ad hoc session on a fresh branch stops, then its PR opens; the
+next session sent from the same checkout's repository resends the first,
+and the store's copy names the PR, equal to what `quest usage --json`
+prints for it.
+
+## Plan
+
+Found in [kixel-ai/kixel.quest#36](https://github.com/kixel-ai/kixel.quest/pull/36),
+the record store; the maintainer decided there to fix it (✅ keep,
+rejected: drop). The gap dates from
+[moq-dev/quest#718](https://github.com/moq-dev/quest/pull/718), which
+settles each queued stop after one upload: list it under `## Caused by`.
+
+How it works today, in `src/cli/send.ts`: each pass rebuilds only queued
+sessions and their sub-agents, then settles their stops. It reads the PRs
+updated since the group's cursor (`read/`), so a PR opened after an
+upload is always read by the group's next pass, with no gap. The store
+keeps each session's latest upload, so a resend replaces, never doubles.
+
+Decided 2026-11-14 (/quest-plan, unattended, so each is a recommendation
+the PR's review can overturn):
+
+- Which sessions does the sender remember after uploading?
+  - ✅ Each queued session, as the root of the tree it emits, when any
+    session in that tree has a latest branch that headed no PR in the
+    read. `attribute` prefers the latest branch, so this catches a session
+    that moved to a new branch whose PR opens later. The whole tree is
+    remembered because `buildRecords` (`src/cli/records.ts`) passes PRs
+    from parent to sub-agent and back, so a parent on `main` takes its
+    PR from a sub-agent's fresh branch
+  - Rejected: only records with `pulls: []`, which misses the moved
+    session; only the session whose own branch lacks a PR, which leaves a
+    parent that inherits it at `pulls: []`
+- When is a remembered tree resent?
+  - ✅ On a pass for its group (endpoint, origin, prefix) whose PR read
+    holds a PR that some member's unresolved latest branch heads, by the
+    rule `attribute` uses, shared rather than copied. A PR on an older
+    branch triggers nothing, since `attribute` falling back to it is
+    already what was sent. The sender queues the root again, so the tree
+    goes through the normal path, rebuilding every member's record, and
+    widens token-max's window only once, when it is due. Waiting for the
+    group's next queued session is the "next `quest` run" the record
+    store's PR recommended
+  - Rejected: polling each remembered tree's group on a timer, which
+    spends GitHub quota every pass for a resend that can wait for the
+    repository's next session
+- When is a remembered tree forgotten?
+  - ✅ Each upload of a root decides afresh by the rule above, so a resend
+    that still leaves a member's latest branch without a PR keeps the
+    tree; it is dropped when token-max no longer lists the root (its
+    transcript was pruned), silently, since the first upload already sent
+    everything but the PR. The harness's transcript retention bounds what
+    is kept, with no constant of our own
+  - Rejected: forgetting after one resend, which loses a branch whose PR
+    opens later still; a fixed age; keeping it until its branch is
+    deleted, which costs a git or GitHub read per session
+- Milestone? ✅ m0 under the benchmark, whose end-to-end check needs every
+  PR's cost to be whole (rejected: m1).
+
+Keep what is remembered in the sender's state directory beside `pending/`,
+one small file per root, holding its `Pending` and, per unresolved member,
+what matching needs: its latest branch with its times and the
+repositories token-max resolved for it.
+
+## Related
+
+- [Record endpoint](/quest/m0/benchmark/records-endpoint.md) - turns the
+  sender on for each repository; this fixes what it sends