diff --git a/pyproject.toml b/pyproject.toml
index 698beff..c67fca4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,6 +33,14 @@ dependencies = [
 dev = [
     "pytest>=7.0",
     "pytest-cov>=4.0",
+    # CI test deps (Linux runners). Without these, pytest tests/ fails:
+    #  - pytest-asyncio: test_solaris_ordering async tests ("not natively supported")
+    #  - numpy: test_frame_validator ("No module named 'numpy'")
+    #  - anthropic: test_host_layer ("anthropic SDK is not installed") -- the
+    #    vendored SDK is Windows-only binaries, unusable on the Linux CI runner.
+    "pytest-asyncio>=0.21",
+    "numpy>=1.24",
+    "anthropic>=0.40.0",
 ]
 websocket = [
     "websockets>=11.0",
diff --git a/python/synapse/inspector/tool_inspect_stage.py b/python/synapse/inspector/tool_inspect_stage.py
index 3aa9387..77a34ea 100644
--- a/python/synapse/inspector/tool_inspect_stage.py
+++ b/python/synapse/inspector/tool_inspect_stage.py
@@ -198,6 +198,9 @@ def _synapse_extract_node(n):
 
 
 def _synapse_extract_flat_ast(target_path):
+    # hou / json / SCHEMA_VERSION / _synapse_extract_node all resolve via the
+    # globals() re-publish before the top-level try (split globals/locals exec
+    # would otherwise hide them inside this function). See that note for why.
     parent = hou.node(target_path)
     if parent is None:
         return json.dumps({
@@ -222,6 +225,27 @@ def _synapse_extract_flat_ast(target_path):
     }, sort_keys=True)
 
 
+# The bridge execs this script with split globals/locals -- exec(code, G, L)
+# where G != L (see handlers.py _run_compiled / api_adapter _run_in_namespace).
+# Top-level defs, imports and constants bind into L, but functions resolve
+# names via their __globals__ (= G), so from INSIDE the functions the other
+# top-level function (_synapse_extract_node), the module constants
+# (SCHEMA_VERSION, _MAX_ERR_LEN) and the imports are all invisible -> NameError,
+# swallowed as extraction_script_crash. `globals()` here (module level) IS G,
+# so re-publish the names the functions need into G. Without this, a clean
+# scene crashes at the _synapse_extract_node call and any errored/warned node
+# double-faults on _MAX_ERR_LEN inside its own except handler.
+globals().update({
+    "hou": hou,
+    "json": json,
+    "traceback": traceback,
+    "SCHEMA_VERSION": SCHEMA_VERSION,
+    "_MAX_ERR_LEN": _MAX_ERR_LEN,
+    "_synapse_extract_node": _synapse_extract_node,
+    "_synapse_extract_flat_ast": _synapse_extract_flat_ast,
+})
+
+
 try:
     print(_synapse_extract_flat_ast(%(target_path_literal)s))
 except Exception as ex:
diff --git a/python/synapse/server/render_notify.py b/python/synapse/server/render_notify.py
index 4d606b4..13a2453 100644
--- a/python/synapse/server/render_notify.py
+++ b/python/synapse/server/render_notify.py
@@ -139,7 +139,7 @@ def send_toast(title: str, body: str) -> bool:
             capture_output=True,
             text=True,
             timeout=10,
-            creationflags=subprocess.CREATE_NO_WINDOW if os.name == "nt" else 0,
+            creationflags=(getattr(subprocess, "CREATE_NO_WINDOW", 0) if os.name == "nt" else 0),
         )
         if result.returncode != 0:
             logger.debug("Toast PowerShell failed: %s", result.stderr[:200])
diff --git a/tests/test_design_system.py b/tests/test_design_system.py
index e2b1ce4..5b59c31 100644
--- a/tests/test_design_system.py
+++ b/tests/test_design_system.py
@@ -20,7 +20,16 @@
 
 # ── Setup ─────────────────────────────────────────────────
 
-_SYNAPSE_HOME = os.path.join(os.path.expanduser("~"), ".synapse")
+# Prefer the DEPLOYED copy (~/.synapse) so this also validates a real install;
+# fall back to the REPO source when nothing is deployed (CI runners, fresh dev
+# checkouts). The layout is identical either way: <base>/{design,houdini,install.py}.
+_DEPLOYED_HOME = os.path.join(os.path.expanduser("~"), ".synapse")
+_REPO_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+_SYNAPSE_HOME = (
+    _DEPLOYED_HOME
+    if os.path.isdir(os.path.join(_DEPLOYED_HOME, "design"))
+    else _REPO_ROOT
+)
 _DESIGN_DIR = os.path.join(_SYNAPSE_HOME, "design")
 _HOUDINI_DIR = os.path.join(_SYNAPSE_HOME, "houdini")
 _SVG_DIR = os.path.join(_DESIGN_DIR, "icons", "svg")
diff --git a/tests/test_inspect_mock.py b/tests/test_inspect_mock.py
index f5decff..f832f45 100644
--- a/tests/test_inspect_mock.py
+++ b/tests/test_inspect_mock.py
@@ -646,3 +646,91 @@ def test_error_message_length_capped(self):
                 error_state="error",
                 error_message="x" * 501,
             )
+
+
+# -----------------------------------------------------------------------------
+# Split-scope exec — the extraction script must survive the bridge's
+# exec(code, globals, locals) with globals != locals (handlers.py _run_compiled
+# / api_adapter _run_in_namespace). Regression for the inspector crash where
+# _synapse_extract_node / SCHEMA_VERSION / _MAX_ERR_LEN were defined at the
+# script's top level (-> locals) but referenced from inside its functions
+# (-> resolved via globals), yielding extraction_script_crash on EVERY scene
+# (and a double-fault on errored nodes via _MAX_ERR_LEN in the except handler).
+# The transport-mocked tests above never exec the real script, so they missed it.
+# -----------------------------------------------------------------------------
+
+
+class TestExtractionScriptSplitScope:
+    @staticmethod
+    def _child(name, node_type="null", errs=(), warns=()):
+        from unittest.mock import MagicMock
+        c = MagicMock()
+        c.name.return_value = name
+        c.type.return_value.name.return_value = node_type
+        c.path.return_value = "/stage/" + name
+        c.errors.return_value = list(errs)
+        c.warnings.return_value = list(warns)
+        c.isDisplayFlagSet.return_value = False
+        c.isBypassed.return_value = False
+        c.lastModifiedPrims.return_value = []
+        c.inputs.return_value = []
+        c.outputs.return_value = []
+        return c
+
+    def _run_template(self, children):
+        """Exec the REAL extraction template the way the bridge does: split
+        globals/locals, with `hou` NOT injected into globals (the inspector
+        transport doesn't). Returns the parsed JSON the script prints."""
+        import io
+        import sys
+        import types
+        from contextlib import redirect_stdout
+
+        from synapse.inspector.tool_inspect_stage import _EXTRACTION_SCRIPT_TEMPLATE
+
+        parent = type("P", (), {})()
+        parent.children = lambda: list(children)
+        mock_hou = types.ModuleType("hou")
+        mock_hou.node = lambda p: parent if p == "/stage" else None
+
+        script = _EXTRACTION_SCRIPT_TEMPLATE % {
+            "schema_version": SCHEMA_VERSION,
+            "target_path_literal": repr("/stage"),
+        }
+        saved = sys.modules.get("hou")
+        sys.modules["hou"] = mock_hou
+        try:
+            g = {"__builtins__": __builtins__}  # split scope; hou NOT in globals
+            l = {}
+            buf = io.StringIO()
+            with redirect_stdout(buf):
+                exec(compile(script, "<inspect_split_scope>", "exec"), g, l)
+        finally:
+            if saved is not None:
+                sys.modules["hou"] = saved
+            else:
+                sys.modules.pop("hou", None)
+        return json.loads(buf.getvalue().strip())
+
+    def test_clean_scene_does_not_crash(self):
+        data = self._run_template([self._child("a"), self._child("b")])
+        assert data.get("synapse_error") != "extraction_script_crash", data
+        assert data["schema_version"] == SCHEMA_VERSION
+        assert len(data["nodes"]) == 2
+        assert all(n["error_state"] == "clean" for n in data["nodes"])
+
+    def test_errored_and_warned_nodes_survive_split_scope(self):
+        # The error/warning paths AND the per-node except handler reference
+        # _MAX_ERR_LEN -- a top-level constant invisible inside the function
+        # under split scope. Pre-fix this double-faulted into a script crash.
+        data = self._run_template([
+            self._child("clean"),
+            self._child("boom", errs=["kaboom detail"]),
+            self._child("warn", warns=["a warning"]),
+        ])
+        assert data.get("synapse_error") != "extraction_script_crash", data
+        by_name = {n["node_name"]: n for n in data["nodes"]}
+        assert by_name["boom"]["error_state"] == "error"
+        assert "kaboom detail" in (by_name["boom"]["error_message"] or "")
+        assert by_name["warn"]["error_state"] == "warning"
+        assert by_name["clean"]["error_state"] == "clean"
diff --git a/tests/test_layout_and_matlib.py b/tests/test_layout_and_matlib.py
index fb023c1..ca8c0bd 100644
--- a/tests/test_layout_and_matlib.py
+++ b/tests/test_layout_and_matlib.py
@@ -249,7 +249,7 @@ class TestMaterialLibraryAutoPopulate:
     """Test that create_node('materiallibrary') auto-scaffolds MaterialX."""
 
     @pytest.fixture
-    def mock_env(self):
+    def mock_env(self, monkeypatch):
         """Set up mock hou environment for handler testing."""
         # Stub hdefereval for synchronous execution
         if "hdefereval" not in sys.modules:
@@ -262,6 +262,16 @@ def mock_env(self):
         from synapse.server import main_thread
         main_thread._HOU_AVAILABLE = True
         main_thread._USE_DEFERRED = False
+
+        # Rebind the `hou` the node handler actually uses to THIS module's stub,
+        # scoped via monkeypatch so it auto-restores after the test and never
+        # leaks to later suites. handlers_node binds `hou` at import time from
+        # sys.modules["hou"]; in the full suite it can be bound to a different
+        # stub, so patch.object(_mock_hou, "node", ...) would never reach the
+        # handler -> hou.node() returns a default mock -> raw createNode chain.
+        from synapse.server import handlers_node
+        monkeypatch.setattr(handlers_node, "hou", _mock_hou, raising=False)
+        monkeypatch.setattr(handlers_node, "HOU_AVAILABLE", True, raising=False)
         return _mock_hou
 
     def _make_parent_node(self):
diff --git a/tests/test_render.py b/tests/test_render.py
index 07b2787..317890f 100644
--- a/tests/test_render.py
+++ b/tests/test_render.py
@@ -202,7 +202,8 @@ def _parm(n):
              patch.object(_handlers_hou, "frame", return_value=frame, create=True), \
              patch.object(_handlers_hou, "text", MagicMock(expandString=MagicMock(return_value="/tmp/houdini_temp")), create=True), \
              patch("pathlib.Path.exists", return_value=True), \
-             patch("pathlib.Path.stat", return_value=MagicMock(st_size=1024)):
+             patch("pathlib.Path.stat", return_value=MagicMock(st_size=1024)), \
+             patch("pathlib.Path.mkdir", return_value=None):
             return handler._handle_render(payload)
 
     def test_returns_image_path_and_engine(self, handler):
@@ -298,6 +299,7 @@ def _fake_exists(self_path):
              patch.object(_handlers_hou, "text", MagicMock(expandString=MagicMock(return_value="/tmp/houdini_temp")), create=True), \
              patch("pathlib.Path.exists", _fake_exists), \
              patch("pathlib.Path.stat", return_value=MagicMock(st_size=2048)), \
+             patch("pathlib.Path.mkdir", return_value=None), \
              patch("time.sleep"):
             result = handler._handle_render({"node": "/stage/usdrender_rop1"})
 
@@ -322,6 +324,7 @@ def test_no_flipbook_fallback_for_non_usdrender(self, handler):
              patch.object(_handlers_hou, "text", MagicMock(expandString=MagicMock(return_value="/tmp/houdini_temp")), create=True), \
              patch("pathlib.Path.exists", return_value=False), \
              patch("pathlib.Path.stat", return_value=MagicMock(st_size=0)), \
+             patch("pathlib.Path.mkdir", return_value=None), \
              patch("time.sleep"):
             with pytest.raises(RuntimeError, match="output wasn't created"):
                 handler._handle_render({"node": "/out/mantra1"})