diff --git a/action.yml b/action.yml
index 6f4cccb..d9256c4 100644
--- a/action.yml
+++ b/action.yml
@@ -26,9 +26,24 @@ inputs:
 runs:
   using: 'composite'
   steps:
+  - name: Get PR info for fork support
+    if: github.event.issue.pull_request
+    id: pr-info
+    shell: bash
+    env:
+      GH_TOKEN: ${{ github.token }}
+    run: |
+      PR_DATA=$(gh api repos/${{ github.repository }}/pulls/${{ github.event.issue.number }})
+      echo "pr_head_owner=$(echo "$PR_DATA" | jq -r '.head.repo.owner.login')" >> $GITHUB_OUTPUT
+      echo "pr_head_repo=$(echo "$PR_DATA" | jq -r '.head.repo.name')" >> $GITHUB_OUTPUT
+      echo "pr_head_ref=$(echo "$PR_DATA" | jq -r '.head.ref')" >> $GITHUB_OUTPUT
+      echo "is_fork=$(echo "$PR_DATA" | jq -r '.head.repo.fork')" >> $GITHUB_OUTPUT
+
   - name: Checkout code
     uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     with:
+      repository: ${{ github.event.issue.pull_request && steps.pr-info.outputs.is_fork == 'true' && format('{0}/{1}', steps.pr-info.outputs.pr_head_owner, steps.pr-info.outputs.pr_head_repo) || github.event.pull_request.head.repo.full_name || github.repository }}
+      ref: ${{ github.event.issue.pull_request && steps.pr-info.outputs.pr_head_ref || github.event.pull_request.head.ref || github.ref }}
       fetch-depth: 0
 
   - name: Copy Claude config to home directory
@@ -51,6 +66,7 @@ runs:
     env:
       GH_TOKEN: ${{ github.token }}
       PR_NUMBER: "${{ github.event.issue.number || github.event.pull_request.number }}"
+      GH_REPO: ${{ github.repository }}
     run: ${GITHUB_ACTION_PATH}/scripts/diff.sh
 
   - name: Hide Previous Reviews