test(web): offline import-safety guard for proteus.web

tests/web/test_import_safety.py

@@ -0,0 +1,28 @@
+"""Importing the web layer must not pull matplotlib or a provider SDK (offline
+invariant — same discipline as tests/viz/test_import_safety.py)."""
+from __future__ import annotations
+
+import sys
+
+
+def test_importing_web_pulls_no_heavy_or_network_deps():
+    # Drop any pre-loaded matplotlib and proteus.web so we observe a fresh
+    # import graph even when earlier tests have cached these modules.
+    for mod in list(sys.modules):
+        if mod == "matplotlib" or mod.startswith("matplotlib."):
+            del sys.modules[mod]
+    for mod in list(sys.modules):
+        if mod == "proteus.web" or mod.startswith("proteus.web."):
+            del sys.modules[mod]
+
+    import proteus.web            # noqa: F401
+    import proteus.web.server     # noqa: F401
+
+    assert "matplotlib" not in sys.modules, (
+        "importing proteus.web pulled in matplotlib; keep the web layer offline"
+    )
+    # provider SDKs are never imported by the web layer
+    for sdk in ("openai", "anthropic", "google", "ollama"):
+        assert sdk not in sys.modules, (
+            f"importing proteus.web pulled in provider SDK {sdk!r}"
+        )