Merge origin/main e474a4f (v1.91.336.0, #3594 landed) into gsta154-train-stamps; CHANGELOG: main's plus this PR's [Unreleased] entry

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -1,5 +1,23 @@
 # Changelog
 
+## [Unreleased]
+
+**Merge trains can stamp every slot themselves under `changelog_fragments`: `train build` builds a stamped prefix for each slot and `train land` publishes it, so no lane stamps a PR by hand.** gstack's own policy still leaves the key off (docs/ship-policy.md#changelog-fragments).
+
+### Added
+- **Stamped merge trains** (`lib/ship-queue-train-stamp.ts`, `lib/ship-queue-train-land.ts`): under `changelog_fragments`, `train build` also builds S_i = stamp(merge(S_(i-1), pin_i)) for every slot, checks each is the merge modulo stamps, keeps every earlier release entry byte for byte and equals the plain prefix outside release paths (`QUEUE_TRAIN_STAMP_MISMATCH`), refuses a symlinked release file before stamping, and gates S_k. `train land --train <nonce> --pr <n>` publishes slot i's S_i exactly. It makes a deterministic stamp commit on [pin, main], journals it before it is pushed under the pin's lease with the `evals-no-debounce` label, waits for checks, merges with `--match-head-commit` and confirms main's tree; a rerun adopts its own stamp head, a PR retargeted off the base refuses, and any other main freezes the queue as before. It first verifies the whole record against git (T0 and S_1..S_k must be the gated head's first-parent chain, each S_i's second parent slot i's pin) and uses only that chain, and it merges only when every name in the new `changelog_fragments.required_checks` is present and green on the stamp commit. `verify --train` refuses a stamped train and names `train land`; `train bisect` of a stamped train tests T0 and S_1..S_k.
+
+### Changed
+- **The main backstop covers a stamped train's merges by exact tree** (`scripts/train-backstop.ts`, `scripts/train-gate.ts`): a record's S_i prefixes cover main only when its tree is exactly S_i; plain T_i prefixes still cover modulo stamps.
+- **A train merge keeps a pin's manifest edits** (`lib/ship-queue-train.ts`): a `package.json` or lockfile conflict against the previous prefix merges three-way with the prefix's version (the same `mergeManifest` land uses) instead of taking the prefix's whole file; anything else that conflicts is a train conflict.
+- **Version Gate reads a stacked child's stamp commit by its own fragments**: a parent's fragment the base has already released is skipped rather than counted again.
+
+### Tests
+- `test/ship-queue-train-stamp.test.ts`: S2 keeps S1's release and runs the versions in order with each slot's bump; a stacked child folds only its own fragment; a four-part package.json base keeps four parts in every S_i, read from S_(i-1); a pin's manifest edit beside the version line survives the previous slot's bump; a symlinked CHANGELOG refuses before anything is written outside; a tampered earlier version or a product change is refused.
+- `test/ship-queue-train-land.test.ts`: build records S1 and S2 and gates S2; land publishes each slot exactly with the label; a foreign push is never overwritten; a merge outside the train freezes the queue; a failed stamp commit pushes nothing; a rerun after the push or after the journal resumes; a retargeted PR refuses; a red stamped train bisects its stamped chain; a plain train refuses `train land`.
+- `test/train-backstop.test.ts`: main equal to S1 is covered; the same tree with another VERSION is gated; a chain mixing stamped and plain prefixes is refused.
+- `test/version-gate-fragments.test.ts`: a stacked child's stamp counts only its own fragment once its parent has landed.
+
 ## [1.91.336.0] - 2026-10-30
 
 **A repository can now assign its version when a PR merges instead of inside the PR: PRs carry unversioned CHANGELOG fragments and `gstack-ship-queue land` stamps, pushes and merges.** Today every PR picks a version before it merges, so each merge makes the next PR's version stale and its lane redoes the stamp (a median 14.5 minutes from stamp commit to merge over 30 slots, Oct 27-29; the queue froze on hand-made stamps in #3422 and #3487). With `changelog_fragments` on, two PRs cut from one base cannot collide, and nobody stamps by hand. gstack's own policy does not turn it on in this release (docs/ship-policy.md#changelog-fragments).
@@ -11,12 +29,8 @@
 - **/ship writes the fragment** (`lib/ship-policy.ts`, `ship/SKILL.md.tmpl`): under the key, `show-effective` prints a `ship: changelog_fragments` line, so Step 12 writes no version and Step 13 writes `<dir>/<branch-slug>.md` (linted with `gstack-prose-lint --gate`) instead of an `[Unreleased]` section; the skill's policy paragraph now says its `ship:` lines bind Steps 12–16.
 - **`restamp_command` gets `GSTACK_RESTAMP_BASE_SHA`**, the release predecessor, so a repo counter such as a SAVE_VERSION computes predecessor + 1 from the base and never from the branch.
 - New result codes with troubleshooting anchors: `CHANGELOG_FRAGMENT_INVALID`, `QUEUE_LAND_LOCKED`, `QUEUE_LAND_CONFLICT`, `QUEUE_LAND_DRIFT`, `QUEUE_LAND_BASE_BUSY`.
-- **Stamped merge trains** (`lib/ship-queue-train-stamp.ts`, `lib/ship-queue-train-land.ts`): under `changelog_fragments`, `train build` also builds S_i = stamp(merge(S_(i-1), pin_i)) for every slot, checks each is the merge modulo stamps, keeps every earlier release entry byte for byte and equals the plain prefix outside release paths (`QUEUE_TRAIN_STAMP_MISMATCH`), refuses a symlinked release file before stamping, and gates S_k. `train land --train <nonce> --pr <n>` publishes slot i's S_i exactly. It makes a deterministic stamp commit on [pin, main], journals it before it is pushed under the pin's lease with the `evals-no-debounce` label, waits for checks, merges with `--match-head-commit` and confirms main's tree; a rerun adopts its own stamp head, a PR retargeted off the base refuses, and any other main freezes the queue as before. It first verifies the whole record against git (T0 and S_1..S_k must be the gated head's first-parent chain, each S_i's second parent slot i's pin) and uses only that chain, and it merges only when every name in the new `changelog_fragments.required_checks` is present and green on the stamp commit. `verify --train` refuses a stamped train and names `train land`; `train bisect` of a stamped train tests T0 and S_1..S_k.
 
 ### Changed
-- **The main backstop covers a stamped train's merges by exact tree** (`scripts/train-backstop.ts`, `scripts/train-gate.ts`): a record's S_i prefixes cover main only when its tree is exactly S_i; plain T_i prefixes still cover modulo stamps.
-- **A train merge keeps a pin's manifest edits** (`lib/ship-queue-train.ts`): a `package.json` or lockfile conflict against the previous prefix merges three-way with the prefix's version (the same `mergeManifest` land uses) instead of taking the prefix's whole file; anything else that conflicts is a train conflict.
-- **Version Gate reads a stacked child's stamp commit by its own fragments**: a parent's fragment the base has already released is skipped rather than counted again.
 - **Version Gate runs on every PR** (the path filter is gone), so under `changelog_fragments` a PR that touches no release file still proves it carries a fragment. An unstamped head keeps its release fields at its merge base and adds a valid fragment (legacy `[Unreleased]` passes; a `[bot]` author needs none); a merge-step stamp commit must have parents [pin, base] and carry the base plus its fragments' effective bump, so a lane that stamps its own head fails. Without the key nothing changes.
 
 ### Tests
@@ -24,10 +38,6 @@
 - `test/ship-queue-land.test.ts` (bare origin and a gh shim): happy path; two PRs from one base without a collision; a legacy stamp plus a dependency edit; a title-derived entry; a product conflict; the lock and `--break-lock`; the base moving during CI; a foreign push never overwritten; a missing receipt; drift, `--repair` and the lock release; the census; a receipt that fails #3567's depth check refuses; a base with a four-part package.json in `stamp_files` lands four parts (#3557), gstack's own shape stays three; one run without `--no-wait` merges; a PR on another base refuses; `--break-lock` refuses a drift lock; a conflict releases the lock; a stacked parent's fragment refuses; a lost journal resumes; `merge-only` merges with `--merge`; a merge GitHub completed behind an error reply reconciles; `--break-lock` refuses a holder mid-merge; `--repair` resumes after a failed PR create and its PR takes over from a clean checkout; a symlinked legacy VERSION refuses in `--dry-run`; a `package.json` version source keeps its dependency edits.
 - `test/version-gate-fragments.test.ts`: fragment heads, premature version changes, a bot author, an advanced base, an invalid fragment, the stamp commit's effective bump (open version claims do not apply to it), and the workflow's missing path filter.
 - `test/restamp-command-boundary.test.ts`: the hook reads its counter from `GSTACK_RESTAMP_BASE_SHA`, not the branch.
-- `test/ship-queue-train-stamp.test.ts`: S2 keeps S1's release and runs the versions in order with each slot's bump; a stacked child folds only its own fragment; a four-part package.json base keeps four parts in every S_i, read from S_(i-1); a pin's manifest edit beside the version line survives the previous slot's bump; a symlinked CHANGELOG refuses before anything is written outside; a tampered earlier version or a product change is refused.
-- `test/ship-queue-train-land.test.ts`: build records S1 and S2 and gates S2; land publishes each slot exactly with the label; a foreign push is never overwritten; a merge outside the train freezes the queue; a failed stamp commit pushes nothing; a rerun after the push or after the journal resumes; a retargeted PR refuses; a red stamped train bisects its stamped chain; a plain train refuses `train land`.
-- `test/train-backstop.test.ts`: main equal to S1 is covered; the same tree with another VERSION is gated; a chain mixing stamped and plain prefixes is refused.
-- `test/version-gate-fragments.test.ts`: a stacked child's stamp counts only its own fragment once its parent has landed.
 
 ## [1.91.335.0] - 2026-10-30