diff --git a/.github/workflows/pr-test-mlx.yml b/.github/workflows/pr-test-mlx.yml
index 55d21301ea..e25d34e186 100644
--- a/.github/workflows/pr-test-mlx.yml
+++ b/.github/workflows/pr-test-mlx.yml
@@ -35,8 +35,10 @@ on:
 permissions:
   contents: read
 
+# Per-PR groups cancel superseded runs; pushes to main key on the commit SHA so
+# every commit on main gets its own run and is never cancelled by a later push.
 concurrency:
-  group: mlx-tests-${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}
+  group: mlx-tests-${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.sha }}
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 jobs:
diff --git a/.github/workflows/pr-test-rust.yml b/.github/workflows/pr-test-rust.yml
index ba116cf0f0..ebc75441b8 100644
--- a/.github/workflows/pr-test-rust.yml
+++ b/.github/workflows/pr-test-rust.yml
@@ -19,8 +19,10 @@ on:
 permissions:
   contents: read
 
+# Per-PR groups cancel superseded runs; pushes to main key on the commit SHA so
+# every commit on main gets its own run and is never cancelled by a later push.
 concurrency:
-  group: gateway-tests-${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}
+  group: gateway-tests-${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.sha }}
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 env: