gstack/docs/ship-policy.md

# The repo ship policy: `.gstack/ship-policy.json`

`/ship` reads one machine-readable file per repository that says how releases
are stamped and merged: the bump level, the queue mode, the repo's own release
tool, the paths where version mentions are rewritten, the CHANGELOG, a paired
mirror, the history policy and the preregistered evals. Without the file
nothing changes: every key has a default that reproduces today's behavior.

The file is **read from the committed copy on the base branch**
(`origin/<base>`), never from the PR's working tree, so a PR cannot smuggle a
command into its own gate. **File presence never authorizes execution:**
`gstack-restamp` runs `release_tool` only under `/ship` or with
`--allow-repo-commands`; standalone it lists the commands and exits 3 with
`repo commands not executed (pass --allow-repo-commands)`. A PR that
introduces or changes the policy runs under the reviewed bootstrap path
(`--policy-from head --allow-repo-commands`) and its receipt says
`policy: head (unreviewed)`.

Tools: `gstack-ship-policy init|validate|show-effective|check-history`,
`gstack-restamp`, `gstack-tree-receipt`, `gstack-ship-receipt`,
`gstack-ship-queue` ([shared merge queue](#run-a-shared-merge-queue), [merge trains](#run-a-merge-train)),
`gstack-evidence bundle|ancestor`. They share the exit table (`0` ok, `1`
fail, `2` usage, `3` refused or needs a flag) and end every error line with a
code from [troubleshooting.md](troubleshooting.md#queue-aware-ship-policy-restamp-tree-receipt-ship-receipt).

<a id="schema-v1"></a>
## Schema v1

`gstack-ship-policy init` writes every key at its default; `init --explain`
prints this table. JSON carries no comments, so examples live in
`.gstack/ship-policy.example.json`. Unknown keys are errors, and there is no
extension mechanism: a key from a newer gstack, or a misspelled one, fails
closed (`POLICY_INVALID`) instead of being ignored. Every key has an
introducing version (`init --explain` and `validate` print it). A key newer
than 1.91.98.0 set to a non-default value requires `min_gstack_version` at
least at its introducing version, and a gstack older than `min_gstack_version`
refuses the file (`POLICY_GSTACK_TOO_OLD`). `validate` ends with
`MIN_READER: gstack <version>`, the floor every lane reading the policy needs.

| Key | Values | Default | Meaning |
|---|---|---|---|
| `bump` | `patch` \| `ask` | `ask` | `patch` skips the MINOR/MAJOR prompt in `/ship` Step 12 and `gstack-restamp --next` bumps PATCH; `ask` keeps the prompt. |
| `queue_mode` | `claim-at-open` \| `stamp-at-merge` | `claim-at-open` | See [stamp-at-merge](#stamp-at-merge). `claim-at-open` is today's queue (`gstack-next-version` claims a slot when the PR opens). |
| `release_tool` | command or `null` | `null` | The repo's own release command (`bun run release:restamp`). Runs in an isolated staging worktree under the [release-tool contract](#release-tool-contract). |
| `release_outputs` | globs | `[]` | Paths the release tool may write beyond the version files, lockfiles, CHANGELOG and `stamp_paths`. Anything else is `RESTAMP_OUTPUT_OUTSIDE_ALLOWED`. |
| `stamp_paths` | globs | `[]` | Where exact `(was X)`, `since: X` and `vX` mentions of the branch's tentative version are rewritten on a restamp. |
| `changelog` | path or `null` | `CHANGELOG.md` | Re-headed on a restamp: the PR's `## [Unreleased]` (or old-version) section moves to the top as `## [<version>] - <date>`. |
| `mirror` | relative path or `null` | `null` | A paired checkout to restamp identically (tier 2: validated and confined today, not yet run). |
| `history` | `merge-only` \| `squash-ok` | `squash-ok` | `merge-only` makes `/ship` refuse a squash or rebase plan; `gstack-ship-policy check-history` reports a rewritten branch (`HISTORY_POLICY_VIOLATION`). |
| `preregistration_shas` | commit ids | `[]` | Each must be an ancestor of HEAD before push: `gstack-evidence ancestor --from-policy`; the ship receipt records the result. |
| `stamp_sensitive_gates` | evidence labels | `[]` | Gates that read VERSION or generated bytes (gstack's own `tests` lane does, through the agents-digest freshness test). The tree receipt never marks them reusable. |
| `pr_count` | `{ default_pr_count, split_requires_owner }` | `{1, true}` | The PR-count row in plan reviews. |
| `maintainers` | GitHub logins | `[]` | Maintainer set for `/review` contributor mode; empty means repository push permission. |
| `stamp_files` | globs | `[]` | The repo's stamp rule: when set, only these files may differ by a stamp (list the version file, manifests, plugin trees and the files holding the PR's own `since:` rows). It applies before every other stamp rule, so a doc `vX` mention outside it is a difference. |
| `stamp_patterns` | literal templates | `[]` | At most 16 templates of at most 128 characters, each with exactly one `{version}` slot (`"version": "{version}"`, `since: '{version}'`, `<!-- x-stamp: {version} -->`); matched literally at a version boundary, never as a regex. The restamp writer and the tree receipt use them beside the built-in forms. |
| `restamp_command` | command or `null` | `null` | The repo's own restamp, run first in the staging worktree; see [restamp_command](#restamp-command). |
| `migrations` | `{ dir, id }` or `null` | `null` | The migration directory and a regex with exactly one capture group for the number in a file name (`"^v(\\d+)-"`); `gstack-pregate regate` reports `MIGRATION_COLLISION`. |
| `gate_command` | command or `null` | `null` | The repo's full pre-merge gate. `gstack-ship-queue gate-ahead` and `ready` print it for the caller to run (in the background or in CI); gstack never executes it. Needs `min_gstack_version`. |
| `full_e2e` | `true` \| `false` | `false` | `true`: every merge needs a passing full-gate result bound to a tree equal to the merging one modulo stamps; `gstack-ship-queue ready`, `stamp` and `verify` refuse without one (`QUEUE_GATE_MISSING`): a gate-ahead record, or the lane's `--gate-exit 0 --gate-log <file>` from its run on the gated head. Needs `min_gstack_version`. |
| `min_gstack_version` | version or `null` | `null` | The oldest gstack that may read the file; see the compatibility rule above. |
| `train` | `{ gate_workflow, free_workflow, full_gate_check, record_artifact, max_size, fill_hours, screen_selection, trial_reservation_usd }` or `null` | `null` | Turns on [merge trains](#run-a-merge-train), read from the base revision only. Every field is required and an unknown field is `POLICY_INVALID`: `max_size` 1 to 6, `fill_hours` above 0 and at most 24, `screen_selection` `gstack-paid` \| `none`, `trial_reservation_usd` above 0 and at most 100. `null` keeps the per-PR queue exactly as it is. Needs `min_gstack_version`. |

Containment, checked by `validate` and again at write time: paths and globs are
repo-relative with no `..` segment, under 256 characters, at most 64 per list,
and a glob's regex expansion under 512 characters; `release_tool` is under 512
characters with no newline; a matched file that resolves through a symlink to
outside the repository is refused (`POLICY_CONTAINMENT`). A mirror may start
with `..` (a sibling checkout) but has no interior `..`; mirror writes are
confined to that directory.

## gstack's own files

gstack's policy (`.gstack/ship-policy.json`, tracked beside `generated.json`
and `pregate.json` under the otherwise ignored `.gstack/`) runs the repo on
stamp-at-merge: the version is allocated once, when the PR is next in the queue,
every bump is PATCH, and `/review` reads the maintainer set from the file. It
names the one release tool `gstack-version-bump --regen-digest` used to
hard-code:

```json
{
  "bump": "patch",
  "queue_mode": "stamp-at-merge",
  "release_tool": "bun scripts/gen-agents-digest.ts",
  "release_outputs": ["agents-digest/gstack-AGENTS.md"],
  "stamp_paths": [],
  "changelog": "CHANGELOG.md",
  "history": "squash-ok",
  "stamp_sensitive_gates": ["tests"]
}
```

`.gstack/ship-policy.example.json` shows every key set the way a serial-merge
repo with a release script, docs mentions and a mirror would set them.

### Queue-side procedure for gstack

Who does what under `stamp-at-merge`, for the PR author and for the thread
running the merge queue:

1. **Open.** The branch carries a tentative stamp of the base's version plus
   PATCH (`gstack-version-bump write --version <base+patch> --regen-digest`)
   and its CHANGELOG section headed with that version directly under
   `# Changelog`; `## [Unreleased]` is also accepted. Nothing is claimed and
   `gstack-next-version` is not consulted; the tentative version is only the
   guess that makes the common case free. CI runs on this head as usual.
2. **Register.** The queue records the PR and its intended order.
3. **Stamp when next.** With every check green on the current head and
   `origin/main` at the SHA the queue assumed, the PR owner (never the queue)
   runs on the branch:
   `gstack-restamp --next --base main --allow-repo-commands --pr <n> --expect-base <main-sha> --expect-order <pr,...>`.
   When the base has not moved past the tentative stamp it prints
   `RESTAMP: X -> X (noop)` and `FILES: (none)`, and the green head is the
   merge candidate with no further CI. When the base moved, it stamps base +
   PATCH, re-heads the CHANGELOG above the base's top entry, reruns the
   release tool, prints `STAMP_VERSION: <X>` and the stamp diff, and refuses
   with `QUEUE_STALE` (nothing written) when the base or order moved after
   `--expect-base` was read. The owner commits and pushes the stamp commit,
   lets CI run on it, and reports `READY #<n> <sha> STAMP_VERSION=<X>`.
4. **Merge.** The queue verifies on that exact SHA: `VERSION` equals
   `STAMP_VERSION`, the CHANGELOG's top heading is `[<X>]` and the heading
   below it is the base's current version, every check is green on that SHA,
   and, when a stamp commit was pushed, it changed only `VERSION`,
   `package.json`, `CHANGELOG.md` and the release outputs
   (`gstack-tree-receipt --gated <green-head> --current <sha>` prints the
   per-file verdict). It then squash-merges with the merge API's expected-head
   `sha` set to that SHA, so a late push is rejected by the server. "VERSION
   above main" is replaced by "VERSION equals the restamp's STAMP_VERSION on
   the SHA being merged, and that version is base + PATCH at merge time".
5. **Not next.** A PR waiting behind another may gate ahead locally with
   `gstack-restamp --after <predecessor-pr>`; it pushes nothing. When the
   predecessor lands, the waiting PR merges `origin/main` in (never a rebase),
   keeping its own CHANGELOG section above the newly merged one, and step 3
   runs.

Until this policy is on `origin/main`, `gstack-restamp --next` reads the base's
`bump: ask` and falls back to a MICRO bump; pass `--bump patch` on the first
PR stamped after the flip if its base predates it.

<a id="run-a-shared-merge-queue"></a>
## Run a shared merge queue

`gstack-ship-queue` strings `gstack-restamp`, `gstack-tree-receipt` and the
ship receipt into the coordinator protocol, so nobody proves a stamp diff by
hand. Lanes own their PRs and never merge; the coordinator owns the order and
every merge. Each step ends in a line the other side acts on, then
`GSTACK_RESULT: skill=ship-queue status=complete|refused run=<path>`. Nothing
here pushes.

**1. Lane: report ready (unstamped).** After the gate and pregate pass on the
pushed head:

```bash
gstack-pregate run --allow-repo-commands
git push
gstack-ship-queue ready --pr 42
```

```
READY #42 <head> STAMP_VERSION=unstamped
pr: https://github.com/<owner>/<repo>/pull/42
head: <head>
version: unstamped
base: origin/main@<sha>
ci: green at <head12> (passed=31 failed=0 pending=0 skipped=2)
PREGATE: pass tree=<tree12> head=<head12> checks=6
gate: command="<gate_command>" full_e2e=no gate-ahead=none
SHIP_RECEIPT: pr=42 head=<head12> …
```

It refuses (`QUEUE_NOT_READY`) when the working tree has tracked edits, HEAD
is not the PR's pushed head, CI at that exact head is not green, or the pregate
result is not a current pass. Send the block as printed.

**2. Lane behind another PR: gate ahead.** Gate the tree the queue will have
once the predecessor lands, while it is still open:

```bash
git fetch origin pull/41/head
gstack-ship-queue gate-ahead --after 41 --pr 42 --predecessor-ref FETCH_HEAD --allow-repo-commands
```

prints `GATE_AHEAD: pr=42 attempt=<id> gated=<sha> tree=<tree> merge_tree=<tree>
predecessor=#41@<sha12> version=<N+1>`, the attempt's own `worktree:`, its
`record:` file, `GATE_COMMAND:` (the policy's `gate_command`) and the exact
`next:` line. Run the gate there, in the background or in CI, then bind it:

```bash
(cd <worktree> && <gate command>) > gate.log 2>&1
gstack-ship-queue gate-ahead --record --pr 42 --attempt <id> --exit $? --log gate.log
```

`GATE_RECORD: pr=42 attempt=<id> exit=0 gated_tree=<tree> log_sha256=<sha256>
current=yes`. The record keeps the log and removes only that attempt's
worktree, and refuses (`GATE_AHEAD_ATTEMPT_INVALID`) when the worktree no
longer holds the gated commit. If the predecessor moves, prepare a new
attempt; attempts never share a worktree, the newest is current, and
recording an older one later prints `current=no (superseded by <id>)`.
`gate-ahead --list --pr 42` shows them all. Send the record file with READY.

**3. Coordinator: call the slot.** Name the version, the base sha and the
order: "#42 next at 1.2.7.0, base `<sha>`, order 41,42".

**4. Lane: stamp.** A gate-ahead lane first merges `origin/main` (with the
predecessor in it) into its branch, never a rebase. Then:

```bash
gstack-ship-queue stamp --pr 42 --version 1.2.7.0 --expect-gated <gated> \
  --expect-base <sha> --expect-order 41,42 --allow-repo-commands
```

`<gated>` is the head the gate ran on: the pushed head the lane gated, or the
record's `gated=` after a gate-ahead. The preflight refuses before anything is
written unless the tree to stamp equals the gated one modulo stamps, the base
is `<sha>` and, under `full_e2e`, a passing gate result is bound to the gated
head. Then it runs the restamp, commits, reruns the tree receipt and prints

```
QUEUE_STAMP: 42 1.2.7.0 head=<sha> gated=<sha> tree=same-modulo-stamps receipt=<sha256>
```

Each stage is journaled in `.gstack/tmp/ship-queue/stamp-42.json`; the
identical command resumes at the first unfinished stage, or returns the stored
`QUEUE_STAMP` when it already finished. A refusal prints
`QUEUE_STAMP_REFUSED: 42 head=<sha> committed=no|yes <sha> stage=<stage>`
and the coded line (`QUEUE_STALE` carries a `recompute:` command). Push the
stamp commit, wait for CI on it, run `ready` again
(`READY #42 <head> STAMP_VERSION=1.2.7.0`) and send it with the
`QUEUE_STAMP` line.

**5. Coordinator: verify, then merge.** From the coordinator's own clone:

```bash
gstack-ship-queue verify --pr 42 --gated <gated> --receipt <sha256> --expect-head <head> [--gate-exit 0 --gate-log <file>]
gstack-ship-queue verify --pr 42 --record <gate-ahead record> --receipt <sha256> --expect-head <head>
```

It fetches `refs/pull/42/head` and reruns the tree receipt there, so
`QUEUE_STAMP` is never a pasted claim: `VERIFY: 42 1.2.7.0 head=<sha>
gated=<sha> tree=same-modulo-stamps receipt=<same sha256>`. Under `full_e2e`,
`--gated` also needs the lane's passing gate log from its run on that head
(`--gate-exit 0 --gate-log <file>`), else `QUEUE_GATE_MISSING`. With a gate-ahead
record, whose gated commit never left the lane's machine, it first recomputes
the merge with `git merge-tree --write-tree <branch head> <predecessor head>`
and compares it with the recorded merge tree, rebuilds the gated tree from
the recorded stamp patch and compares it with the recorded `gated_tree`,
proves that patch is stamps only, checks the predecessor did not move, and
prints `merge_tree:`, `gated_tree:` and `gate:` lines. The last line is
`MERGE_CONDITION: sha=<head>`: merge with that expected head. Any
`QUEUE_VERIFY_MISMATCH` means do not merge.

**Rolling out `gate_command` and `full_e2e`.** Commit them (with
`min_gstack_version` at their introducing version, which `init --explain`
prints) only after every lane's gstack is at least that version, the crew's
install floor (`GSTACK_MIN_REVISION`). A lane on an older gstack refuses the
policy by name rather than reading it differently.

<a id="run-a-merge-train"></a>
## Run a merge train

A merge train gates several READY PRs with one full gate instead of one gate
each. The coordinator merges the pinned, unstamped PR heads in slot order onto
main in a scratch worktree, records each prefix tree (T0 is main, Tk is the
train head), runs the free tests and then one full gate on the train head, and
merges the PRs one at a time, each only while main's tree equals the prefix
the gate covered modulo stamps. A red train is bisected on its red cases only.

The surface is off unless the base revision's `.gstack/ship-policy.json`
declares a `train` block. Without one, `train …` and `verify --train` refuse
with `QUEUE_TRAIN_OFF`, and `ready --pr <n>` prints exactly the per-PR READY
block above (`--screen`, `--no-screen` and `--broad` are ignored with a
warning on stderr). A block for gstack itself would read:

```json
"train": {
  "gate_workflow": "evals.yml", "free_workflow": "free-tests.yml",
  "full_gate_check": "gstack/full-gate", "record_artifact": "gstack-train-record",
  "max_size": 5, "fill_hours": 3, "screen_selection": "gstack-paid",
  "trial_reservation_usd": 1.5
},
"min_gstack_version": "<the version that introduced train>"
```

gstack's own policy carries this block. It went live after the workflow side
(the train-nonce record, the `cases` and `prefix_shas` inputs, the dispatched
screen) merged and one dry-run train passed: two unstamped scratch docs PRs on
a scratch base whose `route` step read the policy from that base instead of
the default branch. `gate_workflow` is dispatched with
`evals_all`, `expected_sha` and `nonce` (bisects add `cases` and
`prefix_shas`, screens add `screen_pr`, `screen_merge_sha` and
`screen_policy`). That run publishes `full_gate_check` as a check run on the
train head and the train record as the `record_artifact` artifact only when
its census is complete and green; gstack reads both and never writes a
check. `screen_selection: gstack-paid` computes gstack's paid case selection
for the screen recommendation; `none` leaves the choice to the lane.
`trial_reservation_usd` is what the bisect reserves for a trial without cost
data.

Every command prints its lines, the coded error line on stderr, then
`NEXT: <command>` and `GSTACK_RESULT: skill=ship-queue status=… run=<record>`.
Records live under `$GSTACK_STATE_ROOT/ship-queue/` (`trains/<nonce>/train.json`
with one attempt record per dispatch, `ready/` receipts and `freeze/`) and
are mirrored to origin as git notes on `refs/notes/gstack-trains` before any
remote effect, so a lost machine loses nothing: `train status` on a clean
state root rebuilds them. `GSTACK_SHIP_QUEUE_NOW` pins the clock for tests.

**1. Lane: READY with a screen choice.** Under a train policy READY needs an
explicit choice:

```bash
gstack-ship-queue ready --pr 42                    # prints SCREEN: lines and the recommendation, refuses
gstack-ship-queue ready --pr 42 --no-screen        # READY receipt; the PR rides unscreened
gstack-ship-queue ready --pr 42 --screen [--broad] # dispatches one paid screen on the PR's merge SHA
```

Without a choice it prints the `SCREEN:` selection (with
`screen_selection: gstack-paid`, the skill's own cases and `recommend
--screen` or `--no-screen`: `--screen` when the screen selects a skill's own
cases) and refuses with `READY_SCREEN_CHOICE_REQUIRED`. The price line says
the dollar figure is pending the cost replay; until it lands, `SCREEN:` shows
case counts and the recommendation only. A lane that already ran focused
local cases says so in the READY block and may pass `--no-screen`. `--screen`
dispatches `gate_workflow` with `screen_pr`, `screen_merge_sha` (the
`refs/pull/<n>/merge` SHA) and `screen_policy` (`narrow`, or `broad` with
`--broad`, today's full PR selection). The nonce key carries the purpose and
the policy, so a repeat follows the same run and a broad screen never adopts
a narrow one. The READY block gains `screen: …`, and the receipt is written
locally and to the notes ref. `--dry-run` prints the dispatch without sending
it.

**2. Coordinator: build.** Name the pins exactly as READY reported them:

```bash
gstack-ship-queue train build --prs 41@<sha>,42@<sha>,43@<sha> --dry-run
gstack-ship-queue train build --prs 41@<sha>,42@<sha>,43@<sha>
```

It prints `ORDER:` (the slot order to announce: screened PRs first in READY
order, then unscreened; when `max_size` or more unscreened PRs wait they form
their own train and `HELD:` lists them; `--order <pr>,<pr>,...` naming every
pinned PR once replaces that rule, for a PR that must merge before another,
and the train's later `NEXT:` rebuilds keep it), one `PREFIX: T<i> <commit>
tree=<tree>` per prefix and one `SLOT:` per PR. `--dry-run` adds the
`ESTIMATE:` line and writes, pushes and dispatches nothing. Otherwise it
writes `train.json`, pushes `train/<nonce>`, dispatches `free_workflow` there
and waits (`--free-timeout <s>`, default 2700) for a green
`workflow_dispatch` run on that exact SHA, then dispatches the full gate
through eval-bg's nonce. A train under `max_size` waits until its oldest READY
has waited `fill_hours` (`QUEUE_TRAIN_WAITING`); `--urgent` dispatches a
one-PR train at once. The same pins on the same base return the live train
instead of a second one; `train build --train <nonce>` resumes a train from
its record. Refusals, all before any spend: `QUEUE_TRAIN_UNTRUSTED` (a fork
head), `QUEUE_TRAIN_MOVED` (a head moved from its pin), `QUEUE_NOT_READY` (no
READY receipt at that head), `QUEUE_TRAIN_CONFLICT` (the printed
`QUEUE_TRAIN_CONFLICT: train <id> stopped at #<pr> (conflicts: <files>) after
merging #<a>,#<b>; nothing dispatched, no branch pushed; fix: …` line names
the build without that PR) and `QUEUE_TRAIN_FREE_RED` (free tests red,
missing, cancelled or on another SHA). In a merge, version files take the
prefix's side and the CHANGELOG merges by section, since the stamp at merge
rewrites both; a PR whose CHANGELOG drops or renames a released heading (or
carries a released entry's text in a section of its own) is a CHANGELOG
conflict, never merged with the damage. READY receipts and train records are
keyed on origin's GitHub owner/repo, so lanes whose origin uses another URL
form (git.capy.ai, ssh, a token URL) share the coordinator's queue.

**3. Coordinator: status and verdict.**

```bash
gstack-ship-queue train status [--train <nonce>]
gstack-ship-queue train verdict --train <nonce>
```

`status` never spends. When a dispatch was attempted but its run never showed
up (`QUEUE_TRAIN_DISPATCH_UNKNOWN`), it lists the workflow's dispatch runs and
either adopts the run carrying the nonce or marks the dispatch `absent`; only
an absent dispatch is sent again, by `train build --train <nonce>`, under the
same nonce. `verdict` reads the run, its record and the `full_gate_check`
check: `GREEN` only for a complete census bound to the train nonce, head and
tree; `QUEUE_TRAIN_PENDING` while it runs; `QUEUE_TRAIN_INCOMPLETE` for INFRA
or INCOMPLETE panels, unbound, partial or cancelled shards, a slice killed
before upload, or no record (never green); `QUEUE_TRAIN_RED` with the red
cases.

**4. A red train: bisect, then at most one rebuild.**

```bash
gstack-ship-queue train bisect --train <nonce> --spend-cap 5 --dry-run
gstack-ship-queue train bisect --train <nonce> --spend-cap 5
gstack-ship-queue train rebuild --train <nonce>
```

The bisect dispatches the red cases (`cases`) on every prefix T0..Tk
(`prefix_shas`), one trial each, after checking every prefix is an ancestor
of `train/<nonce>` (`QUEUE_TRAIN_PREFIX_INVALID`). It reserves every
case×prefix trial (unknown costs at `trial_reservation_usd`) and launches only
the prefixes that fit the cap (`QUEUE_TRAIN_BISECT_CAPPED`; completed prefixes
are kept and a rerun with a higher cap runs only the rest). Rerun it to read
the results. The pattern decides: `ATTRIBUTED #<pr>` only when monotone
(green before, red from that PR on), and `NEXT:` builds the train without it;
red on every prefix with T0 included is `QUEUE_TRAIN_RED_ON_MAIN` (fix forward
on main first); anything else is `QUEUE_TRAIN_UNATTRIBUTED`. An all-green
bisect earns exactly one unchanged rebuild (`train rebuild`, reporting both
runs); a non-monotone pattern earns none and goes to a repair lane. Every
other rebuild is `QUEUE_TRAIN_REBUILD_REFUSED`, and a second red stays red.
An INFRA/INCOMPLETE-only census earns the single re-dispatch
EVAL_POLICY.infraRedispatch allows: `train rebuild --train <nonce> --infra`.
The rebuild-once rule lives in the train module beside that constant until
EVAL_POLICY records it. Bisect results never turn a train green.

**Stamping a slot.** When the slot is called, the lane stamps it at main plus PATCH. Slot 1's pin applies cleanly to main. From slot 2 on, main already carries the earlier slots' stamps, so the pin conflicts on CHANGELOG.md and GitHub can't merge it. The lane merges main into the pin first, then stamps:

```bash
git fetch origin main
git merge --no-ff --no-commit origin/main        # expect a CHANGELOG.md conflict only
bun --no-env-file --config=/dev/null -e "import { mergeChangelogs } from './lib/changelog-check'; import { spawnSync } from 'node:child_process'; import { writeFileSync } from 'node:fs'; const s = (n) => spawnSync('git', ['show', ':' + n + ':CHANGELOG.md'], { encoding: 'utf8', maxBuffer: 1 << 26, timeout: 30000 }).stdout; const m = mergeChangelogs(s(2), s(3), s(1)); if (!m) { console.error('CHANGELOG needs a hand merge'); process.exit(1); } writeFileSync('CHANGELOG.md', m);"
git add CHANGELOG.md && git commit --no-edit
gstack-restamp --next --base main --pr 42 --expect-base <main sha> --expect-order <order> --allow-repo-commands
git add CHANGELOG.md VERSION package.json <release outputs> && git commit -m "v<X> stamp" && git push
```

A conflict in any file other than CHANGELOG.md means the merge isn't the train's prefix. Stop and report it. When the helper says the CHANGELOG needs a hand merge, take main's CHANGELOG unchanged and put your own entry above it. `verify` accepts the resulting head because it contains main and its tree equals T<i> modulo stamps, with its CHANGELOG judged as main's plus lines your pin added, however the conflict was resolved; the `head:` line says "T<i> with main merged in".

**5. Coordinator: verify, merge, verify again.** For each slot in order:

```bash
gstack-ship-queue verify --pr 41 --train <nonce>   # MERGE_CONDITION: sha=<head>
# merge #41 with that expected head; gstack-restamp stamps it at merge
gstack-ship-queue verify --pr 41 --train <nonce>   # VERIFY_TRAIN: #41 merged; main's tree is T1 …
```

Before a merge, main's tree must equal the prefix before the PR modulo stamps
and the PR must be at its pin (stamps aside) or contain main and be T<i>
modulo stamps (its pin with main merged in; its CHANGELOG must be main's with
only lines from the pin's own CHANGELOG diff above it); after it, main's tree
must equal the prefix after it. Anything else is `QUEUE_TRAIN_TREE_MISMATCH`
(or `QUEUE_TRAIN_MOVED`). When nothing of the train has merged, that is a plain
refusal: build a new train on current main. When earlier slots already
merged, main holds a prefix no gate covered on its own, so verify freezes the
queue: the freeze goes to local state and the notes ref first, then the full
gate is dispatched on main's SHA at once (the backstop), and the
`QUEUE_TRAIN_FROZEN:` line lists the merged PRs, main's tree and the backstop
run. While frozen, ordinary trains and other trains' merges are refused
(`QUEUE_TRAIN_FROZEN`). Admit one repair PR at its exact head:

```bash
gstack-ship-queue train build --repair --prs 44@<sha>
```

It runs the normal free tests, full gate and verification on main plus the
repair. When verify confirms the repair merged, it prints `FREEZE: cleared`
and `NEXT:` builds a train of the PRs still unmerged.

**6. Clean up.** `gstack-ship-queue train prune [--train <nonce>] [--dry-run]`
deletes the `train/<nonce>` branches of merged, superseded and dropped trains
(`WOULD-DELETE:`, `DELETED:`, `GONE:`).

**Escape hatches.** Remove the `train` block on the base branch to return
every lane to the per-PR queue at once. `--urgent` ships one PR alone,
`--no-screen` skips the paid screen, `--broad` widens it to today's selection,
and `train build --prs <list without it>` drops a PR at any step.

<a id="ship"></a>
## What `/ship` reads from it

`/ship` Step 3 runs `show-effective --base <base>` and follows its `ship:` lines,
which carry the workflow consequences the skill prose would otherwise spell out:

| Line | Effect |
|---|---|
| `ship: history merge-only: …` | never rebase, squash or force-push; `check-history --plan <merge\|squash\|rebase>` refuses a rewrite plan (`HISTORY_POLICY_VIOLATION`, exit 3) |
| `ship: queue_mode stamp-at-merge: …` | Step 12 items 1–4 are replaced by `gstack-restamp --next --base <base> --pr <n> --expect-base <sha>` when the PR is next, `--after <predecessor-pr>` when it is not; the restamp's own `next:` line says what follows (NEW_VERSION, CHANGELOG entry text only, the merge's expected head) |
| `ship: shared merge queue: …` | in a coordinator-run queue, `gstack-ship-queue ready`, `gate-ahead` and `stamp` replace the restamp calls; see [Run a shared merge queue](#run-a-shared-merge-queue) |
| `ship: gate-ahead: …` | with `.gstack/tmp/gate-ahead.json` present, Step 16 reuses only the lanes `gstack-tree-receipt … --json > .gstack/tmp/tree-receipt.json` marks reusable; stamp-sensitive and not-eligible lanes run live; `--force-gate <reason>` is the coordinator's call |
| `ship: bump patch: …` | Step 12 never asks for MINOR or MAJOR; PATCH or MICRO by size |
| `ship: preregistration: …` | `gstack-evidence ancestor --from-policy --base <base>` must print only `ANCESTOR: ok` before push |
| `ship: release_tool: …` | the command runs only inside `gstack-restamp` (staging worktree, outputs confined to `release_outputs`) |

The PR body's first section is the ship receipt (`gstack-ship-receipt write … --body`),
written by the pr-body section of `/ship` after the body is composed.

## What `/land-and-deploy` reads from it

Step 3.4 runs `show-effective --base <base>` before the merge and prints one
`VERSION_CHECK:` verdict for the PR head:

| Policy | Stops when | Passes |
|---|---|---|
| `queue_mode: stamp-at-merge` | the head's VERSION is not the base's version plus one bump, or the changelog's top two headings at the head are not that version and then the base's top entry (`STOP stamp stale`: run `gstack-restamp --next` on the branch, push the stamp, rerun) | an exact stamp; other open PRs' tentative stamps are ignored |
| `queue_mode: claim-at-open` (and no policy file) | another open PR holds the same VERSION, or the base is already at or above it (`VERSION drift detected`: rerun `/ship`) | any unique VERSION above the base, including a MICRO bump or one below a sibling's claim |

An invalid policy, an unreadable claim list or a missing VERSION is `unavailable`:
the skill reports it and CI's version gate is the backstop. A base at or above the
branch VERSION still stops.

<a id="stamp-at-merge"></a>
## `queue_mode: stamp-at-merge`

Under `stamp-at-merge` nothing is claimed when a PR opens. The stamp happens
when the PR is next, from the base branch's version at that moment, through
the repo's own release tool, across every stamp location at once:

```bash
gstack-restamp --next --base main --allow-repo-commands --pr 42 \
  --expect-base <sha of origin/main the queue assumed> --expect-order 40,41,42
```

prints `ship, next in queue at <version>`, `STAMP_VERSION: <version>`, one
line per stage, the diff limited to stamp files, `MERGE_CONDITION: sha=<head>`
(pass it to the merge API's expected-head `sha` so a check-to-merge race is
rejected by the server) and the `GSTACK_RESULT:` line. `claims: ignored
(stamp-at-merge)` says the legacy claim reader was not consulted. When the base
or the order moved, the result is `QUEUE_STALE` (exit 3) with the exact
`recompute` command; nothing is written.

Stages, each journaled in `.gstack/tmp/restamp-journal.json`:

0. **restamp_command** (only when the policy sets it): the repo's own restamp, see [restamp_command](#restamp-command).
1. **version**: `gstack-version-bump write --version <X>` in the staging worktree (VERSION, the manifest, npm lockfiles); skipped when `restamp_command` owns the version.
2. **release_tool**: the policy command, under the contract below.
3. **changelog**: the PR's `[Unreleased]` or old-version section moves to the top under `<X>`, above its predecessor's entry. Duplicate headings (`CHANGELOG_DUPLICATE_HEADING`) and a top entry that is not `<X>` (`CHANGELOG_TOP_MISMATCH`) are errors.
4. **stamp_paths**: exact `(was X)`, `since: X` and `vX` rewrites, plus every `stamp_patterns` template, within `stamp_paths` and `stamp_files`. `X` is the branch's own tentative stamp (its VERSION when it moved past base), else `--was <X>`, else the version an unstamped branch would have taken next (`base + bump`); mentions of a version the base never released (not a CHANGELOG heading at base, not a tag) are rewritten too, so a queue reorder that moves the base under a branch still finds its `since:` fields. Only the repo's own version width counts, so a 3-digit dependency pin in a 4-digit repo is never a candidate.
5. **mirror**: tier 2; declared and validated, reported as not run.
6. **apply**: every changed file is written to the branch only after all stages validated, each against the fingerprinted preimage; a file edited meanwhile is `RESTAMP_CONFLICT` and the applied writes roll back (rollback refuses to overwrite a file whose bytes differ from the recorded postimage).

Idempotent: a second run with the same version is `noop`. `--dry-run` prints
the full diff and writes nothing (not even the journal). `--version <X>` stamps
exactly X; `--bump` overrides the level; `--queue-mode` overrides the policy.

### Gate-ahead: `--after <pr>`

A reorder is cheap only when the gate can run before the predecessor merges.
`gstack-restamp --after <pr> --predecessor-ref <ref>` merges HEAD and the
predecessor's head in a throwaway worktree (`.gstack/tmp/gate-ahead-worktree`),
resolving only version-file and CHANGELOG-ordering conflicts, stamps N+1
relative to the predecessor's version there, commits, and records
`.gstack/tmp/gate-ahead.json` (`predecessor_head`, `branch_head`,
`gated_head`, `gated_tree`, `version`, `evidence_branch_key`). The PR branch's
history is never touched, so squash-history PRs stay clean. The gate runs in
that worktree; `gstack-evidence bundle` there exports the evidence.

<a id="release-tool-contract"></a>
### The release-tool contract

The release tool runs in an isolated staging worktree seeded from the working
tree's content fingerprint (`gstack-wtree`), with the repo's ignored
`node_modules` linked in. Its outputs are enumerated: the version files,
lockfiles, the CHANGELOG, `stamp_paths` and `release_outputs`. A write outside
that set refuses the whole restamp before anything reaches the branch
(`RESTAMP_OUTPUT_OUTSIDE_ALLOWED`); a non-zero exit is
`RESTAMP_RELEASE_TOOL_FAILED`. Preimages and postimages of every write are
recorded in the journal. Pinning the command string does not freeze its
implementation (`bun run release:restamp` still runs the PR's package script),
so the receipt names the policy revision, the command, its working directory
and the trust scope (`policy: base origin/main@<sha>` or `head (unreviewed)`).

<a id="restamp-command"></a>
### `restamp_command`: the repo owns the stamp

A repo whose own tool knows its stamp locations sets `restamp_command`.
`gstack-restamp` runs it as the first stage inside its staging worktree, a
clean checkout of HEAD, with the allocated version as the last argument and in
`GSTACK_RESTAMP_VERSION`. The caller's HEAD, index and worktree must be clean
first (`RESTAMP_CONFLICT`, nothing written); the generic path keeps its
working-tree fingerprint seed. Anything the command stages or commits in the
staging worktree is folded back into plain edits; then output confinement
applies as for the release tool (`RESTAMP_OUTPUT_OUTSIDE_ALLOWED`), the
version file must hold the target version (`RESTAMP_VERSION_SOURCE`), and a
non-zero exit is `RESTAMP_RELEASE_TOOL_FAILED`. In every failure nothing
reaches the branch. gstack's version writer is skipped; the CHANGELOG and
`stamp_paths` stages still run (a no-op when the tool already did the work).
Read from the base branch and run only with `--allow-repo-commands`, like
`release_tool`. A tool that fetches, merges the base branch or needs a version
of its own choosing cannot run here; give it a mode that takes the version and
writes only stamps.

<a id="tree-receipt"></a>
## The tree receipt

```bash
gstack-tree-receipt --from .gstack/tmp/gate-ahead.json --predecessor-pr 41 --bundle evidence-bundle.json
gstack-tree-receipt --gated <sha> --current HEAD --json
```

Compares two **committed heads** (a working-tree fingerprint can name objects
unreachable once the gate VM is gone) and prints the gated and current heads,
both tree ids, the version pair, the predecessor the gate assumed, the diff
limited to stamp files, one line per file with its rule and verdict, one line
per gate, then two verdict lines:

```
TREE: same-modulo-stamps | changed (<residual paths>)
gate-reuse: eligible (reusable: tests; rerun: digest) | not-eligible (<what changed>) — fix: <rerun command> (GATE_REUSE_NOT_ELIGIBLE)
```

Hunks are classified per file type: the version file (old → new only), the
manifest (`version` key only), npm and bun lockfiles (root `version` keys
only, where `gstack-version-bump` writes; a dependency entry is `changed`),
the CHANGELOG (a heading move or re-heading, compared as an order-independent
multiset of entries), `stamp_paths` and `release_outputs` (every
removed/added pair must be an exact `(was X)` / `since: X` / `vX` rewrite with
X the gated version and the replacement the current one, so a dependency pin
that happens to equal the old version is `changed`; `stamp_patterns`
templates count as stamp forms too). With `stamp_files` set, a file outside it
is `changed (stamp_files: not in the repo's stamp_files allowlist)` whatever
its diff. Any other byte is a change.

Equivalence is decided per gate. A lane in `stamp_sensitive_gates` always
`rerun`s; a verified lane is `reusable` only when the tree is same-modulo-stamps
and the execution identity in the bundle equals the current one: Bun and Node
versions, OS and arch, every lockfile's identity (root version normalized
away), the `.github/workflows` tree id, runtime pin files and
`package.json#engines`, and the runner image when either side knows it. Without
a bundle the identity is unknown and the receipt is `not-eligible`. When the
recorded predecessor head is no longer the predecessor PR's head (checked
through `--predecessor-ref` or `gh pr view --predecessor-pr`) the receipt
prints `PREDECESSOR MOVED <old> -> <new> — fix: gstack-restamp --after <pr>
again (RESTAMP_PREDECESSOR_MOVED)` and refuses `eligible`.