Files
msd-core/gsd-core/references/execute-phase-between-wave-reset.md
0xdhx 238bee7b03 fix(#4881): trust worktree.baseRef:"head" in harness mode; a WorktreeCreate hook withholds it and only a measured fork base restores it (#4921)
* fix(#4881): trust worktree.baseRef:"head" in harness mode and keep the #4868 observation as what restores it under a WorktreeCreate hook

The pre-dispatch base check still derived its harness-mode verdict from the
retired #48 premise that the harness never reads worktree.baseRef: with
"head" set and HEAD diverged from origin/HEAD it degraded every wave with
baseref-head-ignored-by-harness. #4868 inserted an observation of a clean
prior harness worktree at HEAD ahead of that comparison, but an
execute-phase run never has one at the moment it checks — the base-check
runs before any dispatch, a degraded wave creates no worktrees, and a wave
that did run in worktrees has them removed and HEAD moved before the next
check — so the common case was unchanged (#4881 repro states 1 and 4).

Re-scope of the closed #4752 onto current next, with #4868 kept:

- branch a trusts "head" in both isolation modes, the way the harness is
  measured to behave (#4588: three settings layers, three OSes), and the
  spawn-time exit-42 guard stays the observation-based backstop;
- a Claude Code WorktreeCreate hook in any settings file the check reads,
  or a file that does not parse, withholds that trust — the hook creates
  the worktree without applying the setting — and the inferred comparison
  runs, degrading with baseref-head-bypassed-by-hook;
- the #4868 observation (b2) now sits behind branch a: it is reached only
  when "head" was not trusted outright, and on a hook host it is what
  restores the trust — a hook that forks from HEAD leaves exactly that
  evidence, one that forks elsewhere never does. Its per-HEAD cache is
  unchanged. It is skipped under an explicit --observed-fork-base, which
  outranks an inference from a prior worktree;
- --observed-fork-base <sha> threads a measured fork base through the
  evaluation (strict full-hex, TypeError otherwise).

Tests: the #4868 rows are unchanged and still reachable (they run with the
setting unset); the #4752 rows re-land, with the one exit-128 row updated
to the degrade #4734 pinned since; a new #4881 block pins the start-of-run
state (baseref-head, git never consulted), the hook + observation
composition in both directions, and that an explicit observation skips
the probe.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RPXQQPzHGintWtbhBoQCRS

* docs(#4881): rewrite the eight surfaces that still state the harness ignores worktree.baseRef:"head"

Every prose surface #4868 left untouched still asserted the retired #48
premise as verified fact, starting with the step file the orchestrator
reads. Each now describes the measured behaviour, the WorktreeCreate-hook
exception, the --observed-fork-base input, and the #4868 observation as
what lifts the hook degrade; docs/CLI-TOOLS.md gains the
fork-from-head-observed reason row #4868 did not document.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RPXQQPzHGintWtbhBoQCRS

* chore(#4881): set changeset fragment pr to 4921

* fix(#4881): withhold the #4868 observation under the hook interlock

The hook interlock this PR added withheld the worktree.baseRef:"head"
trust but still let b2's prior-worktree observation restore it, and that
observation cannot be attributed to the hook. The evidence is a clean
agent worktree sitting at the orchestrator HEAD; nothing on disk records
which creator left it there, so one the plain harness created BEFORE a
WorktreeCreate hook was configured — with HEAD unmoved since — reads as
evidence for the hook. It was the one fail-open branch in a mechanism
documented as fail-closed.

Keying the observation cache by hook configuration does not close it.
observeHarnessForkFromHead has two legs: a HEAD-keyed cache and a live
probe over .claude/worktrees/agent-*. A hook-keyed cache simply misses,
and the miss falls through to the probe, which re-finds the same stale
worktree and re-confirms. The probe takes no hook input at all. So the
observation is not consulted under the interlock rather than re-keyed:
on a hook host the only admissible positive signal is an explicit
--observed-fork-base measurement of the dispatch in hand, and absent one
the inferred comparison runs and a mismatch degrades with
baseref-head-bypassed-by-hook, leaving the spawn-time exit-42 guard as
the backstop.

Scoped to the case branch a. declined to trust: "head" set AND a hook
(or an unparseable layer) in the harness's path. With no "head" setting
b2 is #4868's own arm and is unchanged, hook or not — re-scoping that
trust is a separate question this PR does not open, and a test pins the
boundary.

Cost, stated: a hook host with "head" set, on a branch diverged from
origin/HEAD and passing no observation, now runs sequentially. It still
runs parallel when HEAD matches origin/HEAD. No workflow threads an
observation today.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NuT9wTyrMaxjAPevqeH4YZ

* refactor(#4881): drop the now-unused forkRef message-builder parameter

buildMsgBaserefHeadIgnored stopped reading forkRef when the message was
made mode-neutral, and the parameter was retained with `void forkRef;`
for symmetry with its two sibling builders, which do read it. Symmetry
is not reason enough to keep a dead parameter on a module-private
function with one caller, so drop it (#4921 review).

Behaviour is unchanged; the message text is pinned by an existing
full-string assertion, which is what covers the only real risk here —
transposing the two remaining arguments at the call site.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NuT9wTyrMaxjAPevqeH4YZ

* test(#4881): exercise both FULL_SHA_RE alternatives at their boundaries

The invalid-observation list pinned 39 and 41 hex around the 40-hex
SHA-1 arm but left the 64-hex SHA-256 arm's own +/-1 boundary
unexercised, which the repo's boundary-coverage convention asks for
(#4921 review). Adds 63, 65 and a 64-length non-hex string.

The regex already rejected all three -- this is coverage of correct
behaviour, not a fix -- so it carries no negative control against a
pre-fix base. That it is not vacuous was shown instead by widening the
arm to {63,65}, under which the row fails by name.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NuT9wTyrMaxjAPevqeH4YZ

* docs(#4881): finish the surface sweep the hook interlock owes

Self-found by this round's own pre-push adversarial review, over six passes.
Eight sites, four classes.

FIVE were prose still asserting the stance the interlock overturned, which
reads as live canon to anyone arriving cold: docs/CLI-TOOLS.md,
docs/CONFIGURATION.md and gsd-core/references/planning-config.md each still
said the hook degrade is lifted "unless/until a clean prior harness worktree is
observed"; observeHarnessForkFromHead's own header still said a qualifying
worktree "can only exist if the harness forked from HEAD"; and a test name
still called the observation "required on a hook host" when it is now
inadmissible there. My own sweep had grepped for "restores"/"lifts" and missed
every one -- the ordinary failure of a grep, which returns what you thought to
search for.

The SIXTH is the same class one step worse: gsd-core/workflows/execute-plan.md
still said flatly that Claude Code's isolation="worktree" "forks from
origin/HEAD, not live local HEAD" -- in a paragraph THIS PR already edits, a
few sentences after the clause it corrected. A tombstone makes only its own
line clean; adjoining text asserting the dead stance is the other half of the
same defect. Now qualified on the setting, with the hook exception named.

The SEVENTH is a proof-strength overstatement that predates this PR, with a
driven counterexample: a worktree created from an older base and since `git
checkout --detach`ed onto HEAD is clean, sits at HEAD, and satisfies the probe
identically, so "can only exist" was false. The worktree's own reflog does
retain that original checkout -- the information is not lost, the probe simply
does not consult it.

The EIGHTH is that the header described only one of the function's two legs. A
cache hit returns the prior conclusion without reading any worktree, so "the
probe reads a worktree's present state" was true of the live probe and false of
the cache. The header now separates them, and names the cache's blindness as a
third reason the observation is inadmissible under a hook.

Gaps seven and eight are inherited from #4868 and accepted there for the
no-hook case. Nothing about the mechanism changes here; only what the header
claims for it.

No behavioural change -- comments, prose, and one test's registered name.

Emitted-Drift-Ack-Growth: execute-plan.md — the Pattern A paragraph gained a qualifying
 clause: it stated flatly that Claude Code forks from origin/HEAD, which is the premise
 this PR retires, a few sentences after the clause the PR had already corrected.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NuT9wTyrMaxjAPevqeH4YZ

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>
Co-authored-by: Tom Boucher <trekkie@nomorestars.com>
2026-09-23 20:15:28 -04:00

2.7 KiB

7b. Pre-wave dependency check (waves 2+ only): Before wave N+1, run gsd_run query verify.key-links {phase_dir}/{plan}-PLAN.md for each upcoming plan. If any PRIOR-wave artifact link fails, present: - ## Cross-Plan Wiring Gap with plan/link/from/pattern rows - Options: investigate+fix before continue, or continue with cascade risk Skip key-links that reference files in the CURRENT (upcoming) wave.

7c. Between-wave manifest reset and worktree base refresh (waves 2+ only — #1369):

REQUIRED before each wave transition when USE_WORKTREES != "false" and ISOLATION = "harness-worktree" (#2652 — keyed on the negotiated isolation model, not the runtime name).

Wave N's WAVE_WORKTREE_MANIFEST was consumed by worktree.cleanup-wave in step 5.5. It must be unset so wave N+1's step 3 creates a fresh manifest for the new wave's worktrees. Without this, the wave N+1 manifest guard (step 5.5, #3384) blocks on the stale/empty consumed file.

After wave N merges and tracking commits, the orchestrator HEAD has advanced past the commit the Claude Code harness may have cached as the worktree fork base at session start. New worktrees spawned for wave N+1 could fork from the stale pre-wave-N HEAD, causing every executor to trip the worktree_branch_check FATAL guard immediately (symptom: HEAD is <old-sha>, expected <new-sha>).

# Unset per-wave manifest so wave N+1 creates a fresh one (#3384, #1369).
unset WAVE_WORKTREE_MANIFEST

# Between-wave base re-check (#1369, #3659, #4588): after wave N merges and tracking
# commits, HEAD has advanced. Re-asserting worktree.baseRef:"head" is NOT done here — the
# setting is either already in place (honored by GSD-created worktrees and by the Claude
# Code harness, #4588) or
# deliberately absent; a re-write would not change the fork base. The safety re-check
# below compares HEAD against the fork base and degrades the remaining waves whenever
# they diverge, avoiding the base-mismatch FATAL in executor agents.
if [ "$ISOLATION" = "harness-worktree" ] && [ "$USE_WORKTREES" != "false" ]; then
  _BETWEEN_DEGRADE=$(gsd_run query worktree.base-check --mode "$ISOLATION" --pick shouldDegrade 2>/dev/null || echo "false")
  if [ "$_BETWEEN_DEGRADE" = "true" ]; then
    _DEGRADE_MSG=$(gsd_run query worktree.base-check --mode "$ISOLATION" --pick message 2>/dev/null || true)
    [ -n "$_DEGRADE_MSG" ] && printf '%s\n' "$_DEGRADE_MSG" >&2
    printf 'Degrading to sequential mode for remaining waves: HEAD advanced past worktree fork base after wave %s merge (#1369).\n' "${N}" >&2
    # Both must move together (#2652): dispatch keys on ISOLATION.
    USE_WORKTREES=false
    ISOLATION=none
  fi
fi