diff --git a/.github/workflows/pr-autodiff.yaml b/.github/workflows/pr-autodiff.yaml
index 85c79d0..46c95c6 100644
--- a/.github/workflows/pr-autodiff.yaml
+++ b/.github/workflows/pr-autodiff.yaml
@@ -15,21 +15,20 @@ jobs:
       (github.event_name == 'pull_request') ||
       (github.event_name == 'issue_comment' &&
        contains(github.event.comment.body, '!pr-diff') &&
-       (github.event.comment.author_association == 'COLLABORATOR' || github.event.comment.author_association == 'MEMBER' || github.event.comment.author_association == 'OWNER') &&
+       (github.event.comment.author_association == 'CONTRIBUTOR' || github.event.comment.author_association == 'COLLABORATOR' || github.event.comment.author_association == 'MEMBER' || github.event.comment.author_association == 'OWNER') &&
        github.event.issue.pull_request)
     steps:
       - name: Get PR head SHA
         id: get-pr-sha
         run: |
-          if [ "${{ github.event_name }}" == "pull_request" ]; then
-            echo "pr_sha=${{ github.event.pull_request.head.sha }}" >> $GITHUB_OUTPUT
-            echo "Retrieved PR head SHA: ${{ github.event.pull_request.head.sha }}"
-          else
-            PR_URL="${{ github.event.issue.pull_request.url }}"
-            SHA=$(curl -s -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" $PR_URL | jq -r '.head.sha')
-            echo "pr_sha=$SHA" >> $GITHUB_OUTPUT
-            echo "Retrieved PR head SHA from API: $SHA"
-          fi
+          PR_URL="${{ github.event.issue.pull_request.url || github.event.pull_request.url }}"
+          # https://api.github.com/repos/OpenManus/pulls/1
+          RESPONSE=$(curl -s -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" $PR_URL)
+          SHA=$(echo $RESPONSE | jq -r '.head.sha')
+          TARGET_BRANCH=$(echo $RESPONSE | jq -r '.base.ref')
+          echo "pr_sha=$SHA" >> $GITHUB_OUTPUT
+          echo "target_branch=$TARGET_BRANCH" >> $GITHUB_OUTPUT
+          echo "Retrieved PR head SHA from API: $SHA, target branch: $TARGET_BRANCH"
       - name: Check out code
         uses: actions/checkout@v4
         with:
@@ -49,6 +48,7 @@ jobs:
           OPENAI_BASE_URL: ${{ secrets.OPENAI_BASE_URL }}
           GH_TOKEN: ${{ github.token }}
           PR_NUMBER: ${{ github.event.pull_request.number || github.event.issue.number }}
+          TARGET_BRANCH: ${{ steps.get-pr-sha.outputs.target_branch }}
         run: |-
           cat << 'EOF' > /tmp/_workflow_core.py
           import os
@@ -59,7 +59,7 @@ jobs:
 
           def get_diff():
               result = subprocess.run(
-                  ['git', 'diff', 'origin/main...HEAD'],
+                  ['git', 'diff', 'origin/' + os.getenv('TARGET_BRANCH') + '...HEAD'],
                   capture_output=True, text=True, check=True)
               return '\n'.join(
                   line for line in result.stdout.split('\n')