fix: make the worktree conflict guard fail closed; unpin the installer tests

bin/worktree.sh

@@ -306,13 +306,23 @@ worktree_remove() {
 # Used by conflict-guard steps. A task is "claimed" if its entry has a
 # `worktree:` field; legacy non-worktree tasks are emitted with worktree-path
 # set to the literal string "-".
-worktree_list_claimed() {
+# worktree_registry_path
+# Echoes the resolved PyAutoMind/active.md, or returns 3 (printing nothing) when
+# it cannot be found. Split out so a caller can tell "nothing is claimed" apart
+# from "I could not read the registry" — see worktree_check_conflict.
+worktree_registry_path() {
   local active="$PYAUTO_MAIN/PyAutoMind/active.md"
   # Back-compat: fall back to the pre-rename PyAutoPrompt/ path if present.
   [[ -f "$active" ]] || active="$PYAUTO_MAIN/PyAutoPrompt/active.md"
-  if [[ ! -f "$active" ]]; then
-    return 0
-  fi
+  [[ -f "$active" ]] || return 3
+  printf '%s\n' "$active"
+}
+
+worktree_list_claimed() {
+  local active
+  # Returns 3, NOT 0, when the registry is unreadable — empty output must never
+  # be mistaken for "nothing is claimed".
+  active="$(worktree_registry_path)" || return 3
   awk '
     # Claim rows are buffered and flushed at the end of each task entry:
     # `worktree:` may appear either side of the `repos:` block, so it is not
@@ -363,13 +373,41 @@ worktree_list_claimed() {
   ' "$active"
 }
 
-# worktree_check_conflict <task-name> <repo1> [repo2 ...]
+# worktree_check_conflict [--allow-missing-registry] <task-name> <repo1> [repo2 ...]
 # Exits 0 if none of the requested repos are claimed by a different task.
 # Exits 1 and prints the conflicts to stderr otherwise.
+# Exits 3 when the registry cannot be resolved — see below.
+#
+# THIS GUARD FAILS CLOSED. It used to return 0 when `active.md` could not be
+# found, which meant a cloud/web/CI session (where the roots are not under the
+# default $HOME/Code/PyAutoLabs) got "no conflict" from a guard that had read
+# nothing. That is worse than no guard, because the workflow documents this
+# call and the skills act on its answer: two sessions could each be told the
+# same repo was free. It now reports the failure and returns non-zero, so the
+# caller stops instead of proceeding on a green light it never earned.
 worktree_check_conflict() {
+  local allow_missing=0
+  if [[ "${1:-}" == "--allow-missing-registry" ]]; then
+    allow_missing=1
+    shift
+  fi
   local task="$1"
   shift
   local want repo existing_task existing_repo existing_branch existing_wt rc=0
+
+  if ! worktree_registry_path >/dev/null; then
+    if (( allow_missing )); then
+      echo "worktree_check_conflict: no registry under \$PYAUTO_MAIN — proceeding UNGUARDED (--allow-missing-registry)" >&2
+      return 0
+    fi
+    echo "worktree_check_conflict: CANNOT VERIFY — no active.md found." >&2
+    echo "  tried: $PYAUTO_MAIN/PyAutoMind/active.md" >&2
+    echo "         $PYAUTO_MAIN/PyAutoPrompt/active.md" >&2
+    echo "  PYAUTO_MAIN=${PYAUTO_MAIN:-<unset>}" >&2
+    echo "  Set PYAUTO_MAIN to the directory holding your PyAutoMind checkout," >&2
+    echo "  or pass --allow-missing-registry to proceed without the guard." >&2
+    return 3
+  fi
   for want in "$@"; do
     while IFS=$'\t' read -r existing_task existing_repo existing_branch existing_wt; do
       if [[ "$existing_repo" == "$want" && "$existing_task" != "$task" ]]; then

skills/WORKFLOW.md

@@ -223,6 +223,13 @@ Task worktrees keep parallel work isolated (`PyAutoBrain/bin/worktree.sh`):
 **dev workflow's own git mechanics** — feature-development work, **not** Build.
 Build is reached only for the release/packaging step (PyPI/tags/notebooks).
 
+`worktree_check_conflict` **fails closed**: it reads `active.md` under
+`$PYAUTO_MAIN` (default `$HOME/Code/PyAutoLabs`) and exits `3` with
+`CANNOT VERIFY` when that registry cannot be resolved, instead of reporting
+"no conflict" from a read that never happened (#225). In `web-github` / `ci-only`
+environments set `PYAUTO_MAIN` to the directory holding the PyAutoMind checkout,
+or pass `--allow-missing-registry` to proceed knowingly unguarded.
+
 ## Repo → GitHub owner mapping
 
 <!-- repos_sync:begin -->

skills/start_dev/reference.md

@@ -105,6 +105,8 @@ PyAutoMind. Shared organ boundary and the execution-environment model are in
 
    This prints one line per `(task, repo, branch, worktree_path)` quadruple currently registered in `active.md`. For each affected repo the new plan wants to touch, check whether a different task already claims it via a `worktree:` field. If so, flag it as a **hard conflict** — the new task cannot start until the other one ships.
 
+   **The guard fails closed (#225).** `worktree_check_conflict` resolves `active.md` under `$PYAUTO_MAIN` (default `$HOME/Code/PyAutoLabs`). When it cannot find the registry it exits **3** with `CANNOT VERIFY`, rather than reporting "no conflict" from a read that never happened — outside local-dev, set `PYAUTO_MAIN` to the directory holding your PyAutoMind checkout. `--allow-missing-registry` proceeds **unguarded** and says so; use it only when you have confirmed by other means that nothing else claims the repos. Exit `1` is a real conflict; `0` is genuinely clear.
+
    Then, for each affected repo, also run:
    ```bash
    git -C <repo_path> branch --sort=-committerdate | head -5

tests/test_skill_install.py

@@ -45,11 +45,33 @@ def test_local_skill_links_resolve():
     assert broken == []
 
 
+def _pyauto_root(tmp_path):
+    """A fixture PYAUTO_ROOT whose `PyAutoBrain/` is this checkout.
+
+    Without this the installer falls back to `DEFAULT_PYAUTO_ROOT`
+    (`bin/../..`, i.e. this repo's grandparent) and looks for
+    `<grandparent>/PyAutoBrain/skills`. That resolves only when the checkout
+    happens to be *named* `PyAutoBrain` and sits one level under the root —
+    true on a laptop, false for a clone at any other path (a cloud session
+    cloning to `pyautobrain` finds nothing, so the Brain skills are never
+    scanned and the assertions below have nothing to assert on).
+
+    Pinning the root makes these tests depend on the installer's behaviour
+    rather than on where the repo happens to be checked out. Same pattern as
+    `test_invalid_codex_name_does_not_suppress_claude_surfaces` below.
+    """
+    root = tmp_path / "PyAutoLabs"
+    root.mkdir(parents=True, exist_ok=True)
+    (root / "PyAutoBrain").symlink_to(BRAIN_HOME, target_is_directory=True)
+    return root
+
+
 def test_installer_keeps_commands_and_installs_both_skill_homes(tmp_path):
     claude_home = tmp_path / "claude"
     codex_home = tmp_path / "codex"
     env = os.environ | {
         "HOME": str(tmp_path / "home"),
+        "PYAUTO_ROOT": str(_pyauto_root(tmp_path)),
         "CLAUDE_HOME": str(claude_home),
         "CODEX_HOME": str(codex_home),
     }
@@ -85,6 +107,7 @@ def test_installer_preserves_non_symlink_destinations(tmp_path):
     marker.write_text("keep\n")
     env = os.environ | {
         "HOME": str(tmp_path / "home"),
+        "PYAUTO_ROOT": str(_pyauto_root(tmp_path)),
         "CLAUDE_HOME": str(claude_home),
         "CODEX_HOME": str(codex_home),
     }

tests/test_worktree_conflict_guard.py

@@ -200,7 +200,37 @@ def test_entry_claiming_no_repos_yields_no_claims(tmp_path):
     assert _claims(tmp_path, NO_CLAIMS) == []
 
 
-def test_missing_active_md_yields_no_claims(tmp_path):
+def test_missing_active_md_reports_failure_rather_than_no_claims(tmp_path):
+    """A missing registry is NOT the same as "nothing is claimed".
+
+    This test previously asserted the opposite — `returncode == 0` with empty
+    output — and that pinned behaviour turned out to BE the defect (#225).
+    `worktree_check_conflict` consumes this function, so returning 0 meant a
+    session whose roots are not under `$PYAUTO_MAIN` got "no conflict" from a
+    guard that had read nothing. Empty output must never be mistaken for a
+    clean registry, so the listing now signals the failure in its exit code.
+    """
     proc = _run(tmp_path, None, "worktree_list_claimed")
+    assert proc.returncode != 0
+    assert proc.stdout == ""       # still emits no bogus rows
+
+
+def test_conflict_guard_fails_closed_when_the_registry_is_missing(tmp_path):
+    """The defect, at the level the skills actually call.
+
+    Documented in `start_dev` step 6 and `start_library` step 1, and its answer
+    decides whether a task may start — so "I could not check" has to stop the
+    caller, not wave it through.
+    """
+    proc = _run(tmp_path, None, "worktree_check_conflict some-task PyAutoFit")
+    assert proc.returncode != 0
+    assert "CANNOT VERIFY" in proc.stderr
+    assert "PYAUTO_MAIN" in proc.stderr      # names what to set
+
+
+def test_conflict_guard_can_be_forced_past_a_missing_registry(tmp_path):
+    """The escape hatch is explicit and loud — never the default."""
+    proc = _run(tmp_path, None,
+                "worktree_check_conflict --allow-missing-registry t PyAutoFit")
     assert proc.returncode == 0
-    assert proc.stdout == ""
+    assert "UNGUARDED" in proc.stderr