diff --git a/.github/workflows/auto-assign-author.yml b/.github/workflows/auto-assign-author.yml
index ec3bcd54e43..daf0d7c50a6 100644
--- a/.github/workflows/auto-assign-author.yml
+++ b/.github/workflows/auto-assign-author.yml
@@ -16,10 +16,15 @@ jobs:
     runs-on: ubuntu-latest
     # Only internal-branch PRs (fork PRs get a read-only token and their author
     # isn't a collaborator, so assignment can't apply), and only when the author
-    # left it unassigned.
-    if: github.event.pull_request.head.repo.full_name == github.repository && github.event.pull_request.assignees[0] == null
+    # left it unassigned. Skip bot/agent authors: assigning an agent (e.g. a
+    # Copilot coding-agent PR) requires a user token, which GITHUB_TOKEN is not.
+    if: >-
+      github.event.pull_request.head.repo.full_name == github.repository
+      && github.event.pull_request.assignees[0] == null
+      && github.event.pull_request.user.type != 'Bot'
     steps:
       - uses: actions/github-script@v7
+        continue-on-error: true
         with:
           script: |
             await github.rest.issues.addAssignees({