test+docs(sandbox): add FR3 invariant regression tests + tech-stack note

conductor/tech-stack.md

@@ -86,6 +86,12 @@
 - **Thread-Local Context Isolation:** Utilizes `threading.local()` for managing per-thread AI client context (e.g., source tier tagging), ensuring thread safety during concurrent multi-agent execution.
 - **Asynchronous Tool Execution Engine:** Refactored MCP tool dispatch and AI client loops to use `asyncio.gather` and `asyncio.to_thread`, enabling parallel execution of independent tool calls within a single AI turn to reduce latency.
 
+## pyproject.toml pytest addopts (added 2026-06-19, per test_sandbox_hardening_20260619)
+
+`[tool.pytest.ini_options].addopts = "--basetemp=tests/artifacts/_pytest_tmp"`.
+
+**Rationale:** Per `conductor/code_styleguides/workspace_paths.md`, ALL test infrastructure paths must live under `./tests/`. pytest's `tmp_path` and `tmp_path_factory` fixtures default to `%TEMP%\pytest-of-<user>\` on Windows. This `addopts` redirects them under `./tests/` so the FR1 runtime guard's allowlist (also `./tests/`) is a single rule.
+
 ## Architectural Patterns
 
 - **Centralized Registry Management:** Consolidation of critical application constants (e.g., `PROVIDERS`, `AGENT_TOOL_NAMES`) into `src/models.py` as a single source of truth, eliminating redundant list definitions across the UI and Controller.

tests/test_test_sandbox.py

@@ -192,3 +192,57 @@ def test_sloppy_py_parses_config_flag() -> None:
     found_set_override_call = True
  assert found_config_arg, "sloppy.py must have a --config argparse argument"
  assert found_set_override_call, "sloppy.py must call paths.set_config_override(args.config)"
+
+
+def test_pyproject_toml_basetemp_is_under_tests() -> None:
+ """pyproject.toml contains --basetemp=tests/artifacts/_pytest_tmp."""
+ pyproject = Path(__file__).resolve().parent.parent / "pyproject.toml"
+ text = pyproject.read_text(encoding="utf-8")
+ assert "--basetemp=tests/artifacts/_pytest_tmp" in text, (
+  "pyproject.toml must set addopts = '--basetemp=tests/artifacts/_pytest_tmp' "
+  "so the FR1 runtime guard's allowlist can be a single rule."
+ )
+
+
+def test_isolate_workspace_does_not_use_tmp_path_factory_for_infra() -> None:
+ """isolate_workspace fixture does not use tmp_path_factory.mktemp."""
+ import ast
+ conftest = Path(__file__).resolve().parent / "conftest.py"
+ tree = ast.parse(conftest.read_text(encoding="utf-8"))
+ for node in ast.walk(tree):
+  if isinstance(node, ast.FunctionDef) and node.name == "isolate_workspace":
+   body = node.body
+   if body and isinstance(body[0], ast.Expr) and isinstance(body[0].value, ast.Constant):
+    body = body[1:]
+   body_src = "\n".join(ast.unparse(stmt) for stmt in body)
+   assert "tmp_path_factory.mktemp" not in body_src, (
+    "isolate_workspace must not use tmp_path_factory.mktemp; "
+    "use _ISOLATION_WORKSPACE under tests/artifacts/ instead."
+   )
+   assert "_ISOLATION_WORKSPACE" in body_src, (
+    "isolate_workspace should reference _ISOLATION_WORKSPACE"
+   )
+   return
+ raise AssertionError("isolate_workspace fixture not found in conftest.py")
+
+
+def test_appcontroller_init_does_not_load_config() -> None:
+ """AppController.__init__ must not call init_state() or load_config() —
+ fixtures apply before App.__init__; loading config in AppController.__init__
+ would race against the autouse isolate_workspace."""
+ import ast
+ app_controller = Path(__file__).resolve().parent.parent / "src" / "app_controller.py"
+ tree = ast.parse(app_controller.read_text(encoding="utf-8"))
+ for node in ast.walk(tree):
+  if isinstance(node, ast.FunctionDef) and node.name == "__init__":
+   src = ast.unparse(node)
+   assert "init_state()" not in src, (
+    "AppController.__init__ must not call init_state() "
+    "(this would trigger config reads before fixtures apply)"
+   )
+   assert "load_config()" not in src, (
+    "AppController.__init__ must not call load_config() "
+    "(this would trigger config reads before fixtures apply)"
+   )
+   return
+ raise AssertionError("AppController.__init__ not found")