diff --git a/.github/workflows/ci-nightly.yml b/.github/workflows/ci-nightly.yml
index 0188ebf2524..bf9d42e9f56 100644
--- a/.github/workflows/ci-nightly.yml
+++ b/.github/workflows/ci-nightly.yml
@@ -46,7 +46,7 @@ jobs:
         run: |
           python -m pip install pytest
           # Standalone CI tool tests; skip repo-root conftest.py (imports cuda.pathfinder).
-          python -m pytest -v --noconftest ci/tools/tests
+          python -m pytest -v --noconftest ci/tools/tests toolshed/tests
 
   find-wheels:
     runs-on: ubuntu-latest
diff --git a/toolshed/check_precommit_installed.py b/toolshed/check_precommit_installed.py
index 19d7cfc20b6..f6145ca58df 100644
--- a/toolshed/check_precommit_installed.py
+++ b/toolshed/check_precommit_installed.py
@@ -20,25 +20,39 @@
 MARKER = b"File generated by pre-commit"
 
 
-def _git_hooks_dir() -> str:
-    result = subprocess.run(
-        ["git", "rev-parse", "--git-path", "hooks"],  # noqa: S607
-        capture_output=True,
-        check=True,
-        text=True,
-    )
-    return result.stdout.strip()
+def _git_hooks_dir() -> str | None:
+    """Resolve the git hooks directory, or None if git cannot tell us.
+
+    Anything that stops git from answering -- not inside a work tree, git
+    missing from PATH, a broken repository -- leaves us unable to confirm the
+    hook is installed, which is the same outcome as "not installed". This
+    check is advisory (see the module docstring), so it must never turn a
+    `pre-commit run` into a failure.
+    """
+    try:
+        result = subprocess.run(
+            ["git", "rev-parse", "--git-path", "hooks"],  # noqa: S607
+            capture_output=True,
+            check=True,
+            text=True,
+        )
+    except (OSError, subprocess.SubprocessError):
+        return None
+    return result.stdout.strip() or None
 
 
 def main() -> int:
     hooks_dir = _git_hooks_dir()
-    hook_path = f"{hooks_dir}/pre-commit"
 
-    try:
-        with open(hook_path, "rb") as f:
-            installed = MARKER in f.read()
-    except FileNotFoundError:
-        installed = False
+    installed = False
+    if hooks_dir is not None:
+        try:
+            with open(f"{hooks_dir}/pre-commit", "rb") as f:
+                installed = MARKER in f.read()
+        except OSError:
+            # Unreadable, a directory, a dangling symlink: all mean we cannot
+            # confirm an installed hook, and none of them justify failing.
+            installed = False
 
     if not installed:
         print(
diff --git a/toolshed/tests/test_check_precommit_installed.py b/toolshed/tests/test_check_precommit_installed.py
new file mode 100644
index 00000000000..d204ec7a2d4
--- /dev/null
+++ b/toolshed/tests/test_check_precommit_installed.py
@@ -0,0 +1,86 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+import check_precommit_installed as mod
+
+WARNING_TEXT = "pre-commit git hook is not installed"
+
+
+def _write_hook(hooks_dir, body=mod.MARKER):
+    hooks_dir.mkdir(parents=True, exist_ok=True)
+    (hooks_dir / "pre-commit").write_bytes(body)
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_installed_hook_is_quiet(tmp_path, monkeypatch, capsys):
+    hooks = tmp_path / "hooks"
+    _write_hook(hooks, b"#!/bin/sh\n# File generated by pre-commit\n")
+    monkeypatch.setattr(mod, "_git_hooks_dir", lambda: str(hooks))
+
+    assert mod.main() == 0
+    assert WARNING_TEXT not in capsys.readouterr().err
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_missing_hook_warns_and_succeeds(tmp_path, monkeypatch, capsys):
+    monkeypatch.setattr(mod, "_git_hooks_dir", lambda: str(tmp_path / "hooks"))
+
+    assert mod.main() == 0
+    assert WARNING_TEXT in capsys.readouterr().err
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_foreign_hook_warns_and_succeeds(tmp_path, monkeypatch, capsys):
+    """A hook installed by something other than pre-commit lacks the marker."""
+    hooks = tmp_path / "hooks"
+    _write_hook(hooks, b"#!/bin/sh\necho hand-written hook\n")
+    monkeypatch.setattr(mod, "_git_hooks_dir", lambda: str(hooks))
+
+    assert mod.main() == 0
+    assert WARNING_TEXT in capsys.readouterr().err
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_outside_a_git_work_tree_warns_and_succeeds(tmp_path, monkeypatch, capsys):
+    """`git rev-parse` exits 128 outside a work tree.
+
+    check=True turned that into a CalledProcessError traceback and a non-zero
+    exit, even though this check is advisory and main() returns 0 on both of
+    its own branches.
+    """
+    monkeypatch.chdir(tmp_path)
+
+    assert mod.main() == 0
+    assert WARNING_TEXT in capsys.readouterr().err
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_git_missing_from_path_warns_and_succeeds(monkeypatch, capsys):
+    def no_git(*args, **kwargs):
+        raise FileNotFoundError(2, "No such file or directory: 'git'")
+
+    monkeypatch.setattr(subprocess, "run", no_git)
+
+    assert mod.main() == 0
+    assert WARNING_TEXT in capsys.readouterr().err
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_unreadable_hook_path_warns_and_succeeds(tmp_path, monkeypatch, capsys):
+    """The open() guard only caught FileNotFoundError, so anything else that
+    makes the path unreadable escaped as a traceback."""
+    hooks = tmp_path / "hooks"
+    (hooks / "pre-commit").mkdir(parents=True)  # a directory, not a file
+    monkeypatch.setattr(mod, "_git_hooks_dir", lambda: str(hooks))
+
+    assert mod.main() == 0
+    assert WARNING_TEXT in capsys.readouterr().err