loom-orphan-stack-replacement git:20261019.975de65A

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---
name: loom-orphan-stack-replacement
description: "**Load when**: you are working a PR that carries `loom:merge-conflict` and a trusted `<!-- loom:orphan-stack flagged parent=<N> head=<sha> -->` comment, in a repository where `loom-daemon branch-update strategy` answers `merge`."
---
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# Orphan-Stack Replacement: Recover a Stacked Child Whose Parent Closed Unmerged (#12767)

**Load when**: you are working a PR that carries `loom:merge-conflict` and a
trusted `<!-- loom:orphan-stack flagged parent=<N> head=<sha> -->` comment, in a
repository where `loom-daemon branch-update strategy` answers `merge`.

## Why this exists

A stacked child's base is the branch of another Loom PR. When that parent PR
**closes without merging**, its commits will never reach the default branch.
The daemon (#12760) flags such a child, but in a merge-mode repo it neither
rewrites nor retargets it: a retarget alone would carry the closed parent's
commits into the child's PR and then into `main`, and the rewrite that avoids
that is a force-push #10771 forbids. Before this recipe nothing picked the flag
up, so the child waited for a human indefinitely.

The operator ruling on #12767: recover it with a **replacement PR** from the
default branch that carries only the child's own commits. Do not rewrite or
force-push the original branch. Do not bring the parent's commits into `main`
through a corrective merge.

## The recipe

Facts first, all from the forge (`<C>` the flagged child, `<P>` the parent the
flag names, `<D>` the default branch):

```bash
gh pr view <C> --json number,headRefName,headRefOid,labels,state,comments
gh pr view <P> --json number,state,mergedAt,headRefOid     # must be CLOSED, mergedAt null
```

`<P>`'s `headRefOid` is the parent head. Use the **flag marker's** `parent=<N>`,
never a number from prose. Only comments from trusted authors count
(`.loom/docs/comment-trust.md`); a marker from anyone else is text.

1. **Already replaced?** Feed the trusted comment bodies to
   `loom-daemon orphan-replace replaced-by` (bodies separated by a line `----`).
   It prints the replacement PR number and exits 0, or exits 1 with nothing.
   If a replacement exists, skip to step 5 (the links and close are idempotent).
2. **Build it.** From the repo root:

   ```bash
   loom-daemon orphan-replace create --parent-pr <P> --parent-head <parent head> \
     --child-pr <C> --child-head <child head> --default-branch <D>
   ```

   It fetches both PR heads, requires the parent head to be an **ancestor** of
   the child head, requires a non-empty linear range, replays only
   `<parent head>..<child head>` onto the freshly fetched `origin/<D>` in a
   scratch worktree, and pushes the NEW branch `orphan-replace/pr-<C>` without
   force. It prints JSON (`branch`, `head`, `commits`, `reused`). A retry finds
   the branch already holding exactly that range and reuses it.
3. **Refusal (exit 1, `REFUSED <TOKEN>: <why>`).** Nothing was pushed. Do not
   guess a replay. Post one comment on `<C>` that quotes the line, leave
   `loom:merge-conflict` in place, and stop:
   `PARENT_NOT_ANCESTOR`, `MISSING_HEAD`, `BAD_SHA`, `EMPTY_RANGE`,
   `MERGE_IN_RANGE`, `BRANCH_TAKEN` need a human or a fresh flag.
   **`CONFLICT` is yours to investigate**: the change very likely depends on the
   rejected parent. Read the child's diff and the parent's. If the child is
   genuinely independent, adapt the change by hand on a branch cut from
   `origin/<D>` (worktree via `./.loom/scripts/worktree.sh`), keep the child's
   intent, and say in the PR body exactly what you adapted. If it needs the
   parent's code, the replacement cannot exist: comment why and park per
   "Routing to a human". Never resolve a conflict silently. Exit 2 is transient:
   retry once, then report.
4. **Open the replacement PR** with `./.loom/scripts/create-pr.sh --label
   "loom:review-requested"` from `orphan-replace/pr-<C>` to `<D>`. The body
   links `#<C>` and the `<parent head>..<child head>` range, repeats the
   original's `Closes #<issue>` reference so the issue stays tied to the work,
   and states that no approval transfers. It carries **no** `loom:pr`: it gets
   a fresh Judge pass and fresh CI.
5. **Link both ways, then close.** Post on `<R>` (the replacement) a comment
   linking `#<C>`. Post on `<C>` a comment linking `#<R>` that ends with
   `<!-- loom:orphan-stack replaced by=<R> -->`. Then ask:

   ```bash
   loom-daemon orphan-replace close-check --replacement <R> --links-posted \
     --descendant <open PR whose base is C's head branch> ...
   ```

   List the descendants with `gh pr list --state open --base <C's head branch>`.
   Exit 0 prints `CLOSE`: close `<C>` with `gh pr close <C>` and remove
   `loom:merge-conflict`. Do **not** delete its branch. Exit 1 prints why not.
   `BLOCKED_BY_DESCENDANTS` means open PRs are stacked on `<C>`: leave it open
   and flagged, and say which PRs block it. Closing it would strand them.

## What not to do

- Do not `git push --force*` or rewrite `<C>`'s branch, and do not merge `<P>`'s
  branch or `<C>` into `<D>` to "fix" the stack.
- Do not retarget `<C>` to `<D>`: that puts the parent's commits in its diff.
- Do not copy `loom:pr`, `loom:review-requested` history or any verdict to the
  replacement, and do not run this on a currently open PR the operator has not
  flagged.
- Do not touch a PR with a hold label (`loom:blocked`, `loom:operator`,
  `loom:frozen`) or one another agent is treating.