diff --git a/.github/workflows/ui-preview-smoke.yml b/.github/workflows/ui-preview-smoke.yml
index da192552c7..a2e4b13e1c 100644
--- a/.github/workflows/ui-preview-smoke.yml
+++ b/.github/workflows/ui-preview-smoke.yml
@@ -31,6 +31,17 @@ jobs:
       actions: read
 
     steps:
+      # claude-code-action requires a valid git working tree (it configures
+      # git user before running). We only drive Playwright at the Vercel
+      # preview URL — we never execute repo code — so checking out the base
+      # branch is sufficient and avoids running any fork-supplied code under
+      # pull_request_target.
+      - name: Checkout base branch
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.repository.default_branch }}
+          persist-credentials: false
+
       - name: Resolve PR metadata + body
         id: pr
         uses: actions/github-script@v9