diff --git a/scripts/tests/test_build_catalog_check_path.py b/scripts/tests/test_build_catalog_check_path.py
index 2ed5cafd8..8a0ae5fde 100644
--- a/scripts/tests/test_build_catalog_check_path.py
+++ b/scripts/tests/test_build_catalog_check_path.py
@@ -169,6 +169,18 @@ def _active_runs(workflow: Path | None = None) -> list[str]:
     stepping around it. No shell parsing, and the ambiguous cases resolve by execution.
     """
     doc = yaml.safe_load((workflow or WORKFLOW).read_text())
+
+    # The workflow's TRIGGERS, before its jobs. A `decisions-guard` job that is perfectly healthy
+    # gates nothing if the workflow stopped running on pull requests, and starting at `jobs:` cannot
+    # see that. Note `on` parses to the boolean True in YAML 1.1 (the Norway problem's cousin), so
+    # the key is looked up both ways rather than assumed.
+    triggers = (doc or {}).get("on", (doc or {}).get(True)) or {}
+    names = set(triggers) if isinstance(triggers, dict) else {triggers} if isinstance(triggers, str) else set(triggers)
+    assert "pull_request" in names, (
+        "pr-checks.yml no longer runs on `pull_request`, so NO gate in it — including the catalog "
+        f"guard — fires on a PR. Triggers found: {sorted(str(n) for n in names)}"
+    )
+
     jobs = (doc or {}).get("jobs") or {}
     job = jobs.get("decisions-guard")
     assert job is not None, (
@@ -250,7 +262,11 @@ def _ci_check_command(workflow: Path | None = None) -> list[str]:
         "the catalog step's script interpolates an Actions expression, which cannot be expanded "
         f"outside the runner — this proof would be executing something else: {script!r}"
     )
-    return ["bash", "-c", script.replace("python3", sys.executable)]
+    # Substitute the interpreter only where `python3` is a bare command word. A plain
+    # `str.replace` rewrites EVERY occurrence, including inside a path — `/usr/bin/python3` would
+    # become `/usr/bin/<venv>/bin/python3` and fail with ENOENT, a red blaming the catalog guard for
+    # something this line did.
+    return ["bash", "-c", re.sub(r"(?<![\w/])python3\b", sys.executable, script)]
 
 
 def _proof_holds(workflow: Path, repo: Path) -> bool:
@@ -345,6 +361,10 @@ _STEP = (
                 1,
             ),
         ),
+        (
+            "the WORKFLOW no longer runs on pull requests",
+            lambda s: s.replace("on:\n  pull_request:", "on:\n  workflow_dispatch:", 1),
+        ),
         (
             "the command survives only as HEREDOC DATA",
             lambda s: s.replace(
diff --git a/scripts/tests/test_worktree_ownership_guard.py b/scripts/tests/test_worktree_ownership_guard.py
index 60f6dab12..9a461c352 100644
--- a/scripts/tests/test_worktree_ownership_guard.py
+++ b/scripts/tests/test_worktree_ownership_guard.py
@@ -63,8 +63,9 @@ def _env() -> dict:
     to the REAL `$HOME/.cache/ersatztv/hook-fire/` log instead of the fixture's tmp dir. That is not
     untidiness: it is #776's defect reintroduced in the file that is meant to prove #776's hooks,
     and it corrupts the `hook-fire-log.sh report` surface this repo cites as the observability claim
-    for every guard still graded NONE. Measured before the fix: 1,488 records for the two fake
-    session ids below in the production log.
+    for every guard still graded NONE. The reproduction, rather than a figure whose evidence has
+    since been deleted: reintroduce the snapshot and run this file, then count records for the two
+    synthetic session ids below — 58 per run, on macOS and Linux alike.
     """
     return {**os.environ, "CLAUDE_PROJECT_DIR": str(REPO_ROOT)}