diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7782894..4c244ed 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -10,6 +10,15 @@ on:
   pull_request:
     branches: [main, master]
   workflow_dispatch:
+    inputs:
+      # Sent by percy/cli's SDK regression fan-out. Accepted for dispatch
+      # compatibility but unused: these tests exercise the GraalJS scripts in
+      # a vm harness and never install @percy/cli.
+      branch:
+        description: CLI branch (ignored by this suite)
+        required: false
+        type: string
+        default: master
 
 jobs:
   test: