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msd-core/get-shit-done/references/worktree-path-safety.md
Tom Boucher ba0409e04e fix(#3097, #3099): add cwd-drift sentinel + absolute-path guard to executor worktree protocol (#3144)
* fix(#3097, #3099): add cwd-drift + absolute-path guards to executor worktree protocol

#3097 — cwd-drift sentinel (gsd-executor.md task_commit_protocol step 0a):
  A Bash cd out of the worktree makes [ -f .git ] false, silently skipping
  all HEAD/branch safety guards. Commits land on main's branch.
  Fix: on first commit, capture spawn-time toplevel into sentinel file at
  .git/worktrees/<name>/gsd-spawn-toplevel. Before every subsequent commit,
  verify ACTUAL_TL matches EXPECTED_TL. Exits 1 with recovery instructions
  if drift detected.

#3099 — absolute-path guard (gsd-executor.md task_commit_protocol step 0b):
  Absolute paths constructed from the orchestrator's pwd (main repo root)
  resolve to the main repo inside worktrees. Edit/Write lands in wrong dir;
  git commit sees a clean worktree tree; work silently lost or leaks to main.
  Fix: before any absolute-path Edit/Write, verify path starts with
  WT_ROOT=/Users/thbouc/projects/get-shit-done. Prefer relative paths.

Both guards are documented in references/worktree-path-safety.md, which
is now loaded into every executor spawn prompt via <execution_context>.
The <worktree_branch_check> footnote references all three steps (0/0a/0b).

execute-phase.md: extracted worktree bash commands to reference file
(safe embed — @ files are inlined before the executor processes the prompt).
The blank line in <required_reading> was removed to stay at the XL=1700 line
budget after adding the @ reference.

Suite: 6986/6986. Closes #3097. Closes #3099.

* fix(lint+executor+docs): allow-test-rule, fix [ -f .git ] guard, fail-closed abs-path check, fix INVENTORY count
2026-05-05 15:02:26 -04:00

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3.6 KiB
Markdown

# Worktree Path Safety
Guards for executor agents running inside Claude Code worktrees. Three checks
must run before any staging, Edit, or Write operation in worktree mode.
---
## Worktree branch check (run once at spawn-time)
FIRST ACTION: HEAD assertion MUST run before any reset/checkout. Worktrees
spawned by Claude Code's `isolation="worktree"` use the `worktree-agent-<id>`
namespace. If HEAD is on a protected ref (main/master/develop/trunk/release/*)
or detached, HALT — do NOT self-recover by force-rewinding via `git update-ref`,
that destroys concurrent commits in multi-active scenarios (#2924). Only after
this passes is `git reset --hard` safe (#2015 — affects all platforms).
```bash
HEAD_REF=$(git symbolic-ref --quiet HEAD || echo "DETACHED")
ACTUAL_BRANCH=$(git rev-parse --abbrev-ref HEAD)
if [ "$HEAD_REF" = "DETACHED" ] || echo "$ACTUAL_BRANCH" | grep -Eq '^(main|master|develop|trunk|release/.*)$'; then
echo "FATAL: worktree HEAD on '$ACTUAL_BRANCH' (expected worktree-agent-*); refusing to self-recover via 'git update-ref' (#2924)." >&2
exit 1
fi
if ! echo "$ACTUAL_BRANCH" | grep -Eq '^worktree-agent-[A-Za-z0-9._/-]+$'; then
echo "FATAL: worktree HEAD '$ACTUAL_BRANCH' is not in the worktree-agent-* namespace; refusing to commit (#2924)." >&2
exit 1
fi
ACTUAL_BASE=$(git merge-base HEAD {EXPECTED_BASE})
if [ "$ACTUAL_BASE" != "{EXPECTED_BASE}" ]; then
git reset --hard {EXPECTED_BASE}
[ "$(git rev-parse HEAD)" != "{EXPECTED_BASE}" ] && { echo "ERROR: could not correct worktree base"; exit 1; }
fi
```
Per-commit HEAD assertion: `agents/gsd-executor.md` `<task_commit_protocol>` step 0.
---
## cwd-drift sentinel — step 0a (#3097)
A prior Bash call may have `cd`'d out of the worktree into the main repo. When
that happens `[ -f .git ]` is false (main repo's `.git` is a directory), silently
skipping all worktree guards. The sentinel captures the spawn-time toplevel and
detects drift before every commit.
```bash
if [ -f .git ]; then # we are in a worktree
WT_GIT_DIR=$(git rev-parse --git-dir 2>/dev/null)
case "$WT_GIT_DIR" in
*.git/worktrees/*)
SENTINEL="$WT_GIT_DIR/gsd-spawn-toplevel"
[ ! -f "$SENTINEL" ] && git rev-parse --show-toplevel > "$SENTINEL" 2>/dev/null
EXPECTED_TL=$(cat "$SENTINEL" 2>/dev/null)
ACTUAL_TL=$(git rev-parse --show-toplevel 2>/dev/null)
if [ -n "$EXPECTED_TL" ] && [ "$ACTUAL_TL" != "$EXPECTED_TL" ]; then
echo "FATAL: cwd drifted from spawn-time worktree root (#3097)" >&2
echo " Spawn-time: $EXPECTED_TL" >&2
echo " Current: $ACTUAL_TL" >&2
echo "RECOVERY: cd \"$EXPECTED_TL\" before staging, then re-run this commit." >&2
exit 1
fi
;;
esac
fi
```
---
## Absolute-path guard — step 0b (#3099)
Edit/Write calls using absolute paths constructed from the **orchestrator's** `pwd`
(main repo root) will resolve to the main repo, not the worktree. Writes land in
the wrong directory; `git commit` from the worktree sees a clean tree and the work
is silently lost.
Before any Edit or Write using an absolute path:
```bash
WT_ROOT=$(git rev-parse --show-toplevel 2>/dev/null)
# Fail fast if ABS_PATH resolves outside the worktree
if [[ "$ABS_PATH" != "$WT_ROOT"* ]]; then
echo "WARNING: $ABS_PATH is outside the worktree ($WT_ROOT)" >&2
echo "Use a relative path or recompute the absolute path from WT_ROOT." >&2
fi
```
**Prefer relative paths** for all Edit/Write operations. When an absolute path is
unavoidable, always derive it from `git rev-parse --show-toplevel` run inside the
worktree — never from `pwd` captured in the orchestrator context.