| name | stacked-pr-loop |
| description | Recurring check-in on a stack of dependent PRs — rebase children onto updated parents, surface CI state, flag anything waiting on a human-only gate, and report only what changed since last time. Meant to be handed to a time-based loop, not run once. |
| disable-model-invocation | true |
Stacked-PR loop
A stack is a chain of PRs where each depends on the one below it merging first (main <- A <- B <- C). Left unattended, a stack rots two ways: a lower PR updates and the ones above it go stale, or CI needs a nudge (a manual trigger comment, a required check that didn't fire) and nobody's watching. This is one check-in pass, meant to run on an interval, not a one-shot fix.
Step 1 — Map the current stack
List the PRs in the chain and their actual base branches (not assumed order — read each PR's base). Note which ones are merged, open, or closed-unmerged; a closed-unmerged PR downstream of it needs re-basing onto whatever the next real base is.
Done when you have the true current shape of the stack, bottom to top.
Step 2 — Rebase anything behind its base
For each open PR whose base has moved since the PR's branch was last updated (the base PR merged, or main advanced and this is the bottom of the stack): rebase the branch onto the current base and push. Do this bottom-up — rebasing a PR before the one below it is settled just means redoing the work.
Done when every open PR in the stack is rebased onto its actual current base, or you've confirmed it already was.
Step 3 — Pull real CI state, not a cached rollup
For each PR, get the live per-check state against its current head (a rebase invalidates prior runs). If a check is required but hasn't run, that's a red flag, not a pass — don't read absence as success.
Step 4 — Flag human-only gates explicitly
Some CI systems require a maintainer-posted trigger comment for a check to run at all (a bot/fork-safety gate). If a PR's CI never fired and the repo uses one of these gates, name it as the specific thing blocking progress — don't just report "CI hasn't run." This is a gate only a human can clear; the loop's job is surfacing that it's waiting, not working around it.
Step 5 — Report deltas only
Compare against the last pass. Report:
- Changed since last check — a PR went green, went red, got rebased, or is newly waiting on a human gate.
- Ready to merge — bottom of the stack, green, rebased onto current
main. Merge bottom-up only if you have standing authorization to merge without asking each time; otherwise surface it and stop.
- Unchanged — skip it in the report; repeating the same status every cycle just trains you to stop reading.
Stop condition for the loop as a whole: the entire stack has merged, or a full pass produces no state changes from the previous one.
