The vendored HttpCtrl mock is fragile in several ways that cause cascading setup failures (broker behaviour is fine): - **Mock started after the CSR is registered** — the broker's first forward can race the mock startup. Start the mock first, or add a readiness wait. - **`OSError` on mock-server bind** (D001_02_exc / D002_02_exc / D012_01_exc) — a single port clash cascades the whole setup; make `Start Context Source Mock Server` resilient (retry / rebind). - **`Set Stub Reply` is exact-match on path+query** so it doesn't match the broker's canonical forwarded URL — match by prefix or regex. - **Query-response stubs supply a single object, not an array** (D011_01_* / D011_02_red_01) — serialise the body / wrap as an array before stubbing.