Enforce runtime-only workspace directory creation policy

backend/tests/test_no_import_time_mkdir.py

@@ -0,0 +1,72 @@
+"""Guardrail: startup-loaded modules must not write filesystem at import time."""
+
+from __future__ import annotations
+
+import ast
+from pathlib import Path
+
+
+STARTUP_MODULES = [
+    "backend/app.py",
+    "backend/alwrity_utils/router_manager.py",
+    "backend/routers/seo_tools.py",
+    "backend/middleware/logging_middleware.py",
+    "backend/api/youtube/router.py",
+    "backend/api/youtube/handlers/avatar.py",
+    "backend/api/youtube/handlers/images.py",
+    "backend/api/youtube/handlers/audio.py",
+    "backend/utils/media_utils.py",
+]
+
+
+def _is_forbidden_call(node: ast.Call) -> bool:
+    func = node.func
+    if isinstance(func, ast.Attribute):
+        if isinstance(func.value, ast.Name) and func.value.id == "os" and func.attr == "makedirs":
+            return True
+        if func.attr == "mkdir":
+            return True
+    return False
+
+
+def _top_level_forbidden_calls(tree: ast.AST) -> list[tuple[int, str]]:
+    """Return forbidden calls that execute during module import.
+
+    We intentionally do not flag calls inside function/class bodies, because those
+    are runtime operations and safe for this policy.
+    """
+    violations: list[tuple[int, str]] = []
+
+    for statement in getattr(tree, "body", []):
+        # Skip function/class definitions: their bodies are not executed at import time.
+        if isinstance(statement, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef)):
+            continue
+
+        nodes_to_visit = [statement]
+        while nodes_to_visit:
+            node = nodes_to_visit.pop()
+
+            # Do not descend into nested function/class definitions.
+            if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef)):
+                continue
+
+            if isinstance(node, ast.Call) and _is_forbidden_call(node):
+                violations.append((node.lineno, ast.unparse(node.func)))
+
+            nodes_to_visit.extend(ast.iter_child_nodes(node))
+
+    return violations
+
+
+def test_no_import_time_mkdir_calls_in_startup_modules() -> None:
+    all_violations: list[str] = []
+
+    for rel in STARTUP_MODULES:
+        module_file = Path(rel)
+        source = module_file.read_text(encoding="utf-8")
+        tree = ast.parse(source)
+        violations = _top_level_forbidden_calls(tree)
+        for line, call in violations:
+            all_violations.append(f"{rel}:{line} -> {call}")
+
+    assert not all_violations, "Top-level filesystem writes found:\n" + "\n".join(all_violations)