diff --git a/api.py b/api.py
index 5d3bcaf..7b05050 100644
--- a/api.py
+++ b/api.py
@@ -15,8 +15,12 @@ def build_view_router(cfg: dict):
 
     r = APIRouter()
 
+    # No `-> HTMLResponse` annotation: under postponed annotations it is a string FastAPI
+    # resolves against this MODULE's globals, where the function-local import isn't
+    # visible — and even with `response_class=` set, the unresolved annotation made the
+    # host's /openapi.json answer 500 on every agent running this plugin.
     @r.get("/view", response_class=HTMLResponse)
-    async def _view() -> HTMLResponse:
+    async def _view():
         return HTMLResponse(PAGE)
 
     return r
diff --git a/tests/test_api.py b/tests/test_api.py
index 2be4643..6dfe63d 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -15,6 +15,13 @@ def client(registry):
     return TestClient(app)
 
 
+def test_the_routers_leave_the_host_schema_buildable(client):
+    """A page route annotated `-> HTMLResponse` with a function-local import can't be
+    resolved when FastAPI builds the schema, and one such route takes the host's whole
+    /openapi.json down (found in QA on the desktop app, 2026-09-11)."""
+    assert "/plugins/learning_wiki/view" in client.app.openapi()["paths"]
+
+
 def test_view_served_on_declared_public_path(client):
     r = client.get("/plugins/learning_wiki/view")
     assert r.status_code == 200