diff --git a/.github/workflows/hypatia-scan.yml b/.github/workflows/hypatia-scan.yml
index 9b99cfd..d22fb15 100644
--- a/.github/workflows/hypatia-scan.yml
+++ b/.github/workflows/hypatia-scan.yml
@@ -25,5 +25,9 @@ permissions:
 
 jobs:
   hypatia:
-    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@5a93d9d57cc04de4002d6d0ecd336fc7a8698910
+    # INTERIM: pinned to the last working SHA. standards@5a93d9d's hypatia
+    # reusable pins a non-existent actions/cache SHA (d4373f2…), which hard-fails
+    # this check at startup. Restore the @5a93d9d pin once standards repins
+    # actions/cache to v4.2.0 (1bd1e32a3bdc45362d1e726936510720a7c30a57).
+    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@915139d73560e65a8240b8fc7768698658502c89
     secrets: inherit