diff --git a/.github/workflows/fork-ci.yml b/.github/workflows/fork-ci.yml
index faf9915f5b1..74f66be6160 100644
--- a/.github/workflows/fork-ci.yml
+++ b/.github/workflows/fork-ci.yml
@@ -7,7 +7,12 @@ env:
 
 on:
   workflow_dispatch:
+  # Full PR CI is for our implementation layer. Candidate and Tim imports are
+  # verified after they are folded into fork/integration; including their
+  # permanent stack PRs here creates duplicate runs on every stack rewrite.
   pull_request:
+    branches:
+      - fork/changes
 
 concurrency:
   group: ci-${{ github.event.pull_request.number || github.ref }}
diff --git a/.github/workflows/mobile-eas-preview.yml b/.github/workflows/mobile-eas-preview.yml
index a36ef326715..0e6afb6c3e4 100644
--- a/.github/workflows/mobile-eas-preview.yml
+++ b/.github/workflows/mobile-eas-preview.yml
@@ -2,6 +2,10 @@ name: Mobile EAS Preview
 
 on:
   pull_request:
+    # Preview builds belong to feature PRs. The permanent fork stack PRs target
+    # lower provenance layers and must not create a preview run on every rebase.
+    branches:
+      - fork/changes
     types: [opened, reopened, synchronize, labeled, unlabeled]
 
 jobs: