diff --git a/.github/workflows/trace-ace-v121-eval-only.yml b/.github/workflows/trace-ace-v121-eval-only.yml
index 4c7d0e74..4e66c1dd 100644
--- a/.github/workflows/trace-ace-v121-eval-only.yml
+++ b/.github/workflows/trace-ace-v121-eval-only.yml
@@ -1,12 +1,13 @@
 name: Trace Ace V121 Eval Only
 
 on:
-  push:
+  pull_request:
     branches: [agent/v121-cache-batch2]
     paths:
       - '.github/workflows/trace-ace-v121-eval-only.yml'
   workflow_dispatch:
 
+# Infrastructure-only rerun after allowing frozen string arrays in arrays.npz.
 concurrency:
   group: trace-ace-v121-eval-only
   cancel-in-progress: false
diff --git a/competitions/trace_the_ace/V121_EVAL_TRIGGER.txt b/competitions/trace_the_ace/V121_EVAL_TRIGGER.txt
new file mode 100644
index 00000000..dc3578ec
--- /dev/null
+++ b/competitions/trace_the_ace/V121_EVAL_TRIGGER.txt
@@ -0,0 +1 @@
+Infrastructure-only trigger marker for the isolated frozen V121 evaluation PR.
diff --git a/competitions/trace_the_ace/v121_staged_transport.py b/competitions/trace_the_ace/v121_staged_transport.py
index 0e5f1ee5..b6e377db 100644
--- a/competitions/trace_the_ace/v121_staged_transport.py
+++ b/competitions/trace_the_ace/v121_staged_transport.py
@@ -127,7 +127,9 @@ def load_embeddings(path: Path):
 def evaluate(a):
     d = Path(a.dir)
     X75 = load_npz(d / 'X75.npz'); Xr = load_npz(d / 'Xr.npz')
-    z = np.load(d / 'arrays.npz', allow_pickle=False)
+    # Infrastructure-only serialization repair: these frozen arrays contain strings
+    # (objectives/support/sessions), which NumPy stores as object arrays.
+    z = np.load(d / 'arrays.npz', allow_pickle=True)
     y=z['y']; objectives=z['objectives']; support=z['support']; sessions=z['sessions']
     E_obj, E_sem = load_embeddings(Path(a.embeddings))
     if len(y) != E_obj.shape[0] or len(y) != E_sem.shape[0]: