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Guide CI: retrieve a missing PR base before selecting rendered builds #2183
Description
The Guide workflow can fail in Select rendered guide build before compilation or rendering: its depth-100 checkout does not always contain github.event.pull_request.base.sha, and the unchanged git diff reports fatal: bad object. Observed on #2017 in Guide run 41338974404; earlier #1887 reviews record the same failure.
Bounded scope: make the exact event-base commit available before the existing changed-file comparison, reusing the shallow exact-base fetch pattern already present in native CI. Preserve the comparison endpoints/path set, workflow permissions and triggers, publication behavior and required native checks. Retrieval/diff errors must fail the selector, never silently choose a render mode. No history repair or shared Git-storage manipulation.
Acceptance: reproduce the missing-base failure in an independent repository, then exercise the actual selector on missing/present bases with relevant and irrelevant changes, non-PR events and an unavailable base. Verify that it preserves true changed-file selection, leaves HEAD unchanged and fails closed. Obtain independent review of the small workflow/test change.
Worker roadmap_crypto, session crypto-guide-base-20261101; branch fix/guide-shallow-base-20261101 in the private full-network crypto lane. Search found no existing bounded selector follow-up. This is a CI usability fix, with no Lean, mathematical, security-game or curated-abstract impact.
Activity
SamuelSchlesinger commentedon Nov 1, 2026
active— workerroadmap_crypto, sessioncrypto-guide-base-20261101, branchfix/guide-shallow-base-20261101in the private full-network crypto lane. I am reproducing the recorded #2017 shallow checkout before changing the selector. Native CI already distinguishes the synthetic merge's current base parent from a stale event-base SHA; the reproduction will also check that the selected paths belong to the PR, rather than later main commits.SamuelSchlesinger commentedon Nov 1, 2026
roadmap_crypto: confirmed the recorded failure in a new independent repository using the official197f1e83checkout at depth 100: the event-base commit05896cefis absent, so the unchanged selector exits 128 before writing a mode. Fetching that exact base restores the originalrender=falsedecision with HEAD unchanged.Fix
99e69c4eadds only fetch-on-missing before the existing diff. Six actual-workflow/Git regressions and hygiene pass. Default full validation and separate-context coordinator review are in progress; the comparison policy, permissions, triggers and publication remain unchanged.SamuelSchlesinger commentedon Nov 1, 2026
roadmap_crypto: #2196 at99e69c4ehas independent coordinator approval. The PR owns validation and scope; current hosted checks and coordinator integration remain. This issue stays open until the fix lands.ci(guide): fetch a missing PR base before build selection (cslib-comm…