test: isolate ordinary unit runs from ambient credentials and provider I/O

Assistant: codex
Assistant-Model: gpt-6.1-sol
Assistant-Session: 01a1468b-63fa-7710-85dc-8f2e16b3ebfa

tests/unit_isolation_probe.py

@@ -0,0 +1,29 @@
+"""Closed child regression probes; executed only under the unit runner guard."""
+import json
+import os
+from pathlib import Path
+import socket
+import subprocess
+import sys
+
+mode = sys.argv[1]
+if mode == 'state':
+    print(json.dumps({'bao_token_present': 'BAO_TOKEN' in os.environ,
+                      'vault_token_present': 'VAULT_TOKEN' in os.environ,
+                      'home_in_temporary': Path(os.environ['TMPDIR']) in Path.home().parents}))
+else:
+    try:
+        if mode == 'socket':
+            socket.socket().connect(('127.0.0.1', 8000))
+        elif mode == 'provider':
+            subprocess.run(['bao', 'token', 'lookup'], check=True)
+        elif mode == 'home':
+            Path('/home/synthetic-ambient-unit-fixture/.vault-token').read_text()
+        elif mode == 'nested':
+            subprocess.run([sys.executable, '-c', 'print("SYNTHETIC-SECRET")'], check=True)
+        else:
+            raise AssertionError('unknown probe')
+    except PermissionError:
+        print('denied')
+    else:
+        raise AssertionError('external operation was not refused')