diff --git a/.github/workflows/sync_docs_analyze.yml b/.github/workflows/sync_docs_analyze.yml
index 30fc5e87..1bec5e70 100644
--- a/.github/workflows/sync_docs_analyze.yml
+++ b/.github/workflows/sync_docs_analyze.yml
@@ -94,7 +94,13 @@ jobs:
 
           else
             echo "🆕 New PR event - analyzing full changes"
-            COMPARE_BASE="$PR_BASE"
+
+            # Use merge-base to find where branch diverged from main
+            # This allows stale branches to trigger automation without false "mixed content" errors
+            MERGE_BASE=$(git merge-base "$PR_BASE" "$PR_HEAD")
+            echo "Branch diverged from main at: $MERGE_BASE"
+
+            COMPARE_BASE="$MERGE_BASE"
             COMPARE_HEAD="$PR_HEAD"
             IS_INCREMENTAL="false"
           fi