diff --git a/pyproject.toml b/pyproject.toml
index 687aa2f..914bfbf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,7 +30,10 @@ dependencies = [
     "python-dotenv>=1.0.0",
     "sqlalchemy>=2.0.0",
     "alembic>=1.12.0",
-    "fastapi>=0.100.0",
+    # 0.137.0 regressed include_router: routed endpoints no longer appear in
+    # app.routes (they still serve, but introspection breaks). Pin below it
+    # until a fixed release lands. See test_app_factory metrics route checks.
+    "fastapi>=0.100.0,<0.137.0",
     "starlette>=0.40.0,<1.0.0",
     "uvicorn[standard]>=0.23.0",
     "paho-mqtt>=2.0.0",