diff --git a/backend/requirements-dev.txt b/backend/requirements-dev.txt
index b54195c..296cea3 100644
--- a/backend/requirements-dev.txt
+++ b/backend/requirements-dev.txt
@@ -1,4 +1,6 @@
 -r requirements.txt
 pytest>=8,<10
 httpx>=0.27,<1
+# FastAPI/Starlette TestClient uses the httpx2 package in this runtime.
+httpx2>=2.13,<3
 ruff>=0.9,<1