diff --git a/.github/workflows/_test_backend.yml b/.github/workflows/_test_backend.yml
index 6323c007f4a..9b439f8bb6c 100644
--- a/.github/workflows/_test_backend.yml
+++ b/.github/workflows/_test_backend.yml
@@ -11,6 +11,11 @@ on:
         description: 'JSON array of flows to test'
         required: true
         type: string
+      exclude:
+        description: 'JSON array of {flow, suite} pairs to drop from the matrix'
+        required: false
+        type: string
+        default: '[]'
       ref:
         description: 'Git ref to checkout'
         required: false
@@ -50,6 +55,7 @@ jobs:
       matrix:
         flow: ${{ fromJSON(inputs.flows) }}
         suite: [models, operators]
+        exclude: ${{ fromJSON(inputs.exclude) }}
 
     uses: pytorch/test-infra/.github/workflows/linux_job_v2.yml@main
     with:
@@ -126,6 +132,7 @@ jobs:
       matrix:
         flow: ${{ fromJSON(inputs.flows) }}
         suite: [models, operators]
+        exclude: ${{ fromJSON(inputs.exclude) }}
 
     uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
     with:
diff --git a/.github/workflows/test-backend-coreml.yml b/.github/workflows/test-backend-coreml.yml
index c215d0f7f46..dcb17b1d344 100644
--- a/.github/workflows/test-backend-coreml.yml
+++ b/.github/workflows/test-backend-coreml.yml
@@ -45,6 +45,10 @@ jobs:
         ${{ github.event_name == 'schedule'
             && '["coreml", "coreml_static_int8"]'
             || '["coreml"]' }}
+      # The operators suite under coreml_static_int8 has never finished inside the
+      # 180 minute limit, so it is cancelled every night after burning about three
+      # macOS runner hours for no result. See issue #21623.
+      exclude: '[{"flow": "coreml_static_int8", "suite": "operators"}]'
       ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
       timeout: 180
       run-macos: true