next_node_id mismatches are a common model hallucination that the retry prompt doesn't reliably fix. On the final (3rd) attempt, accept the branch with strict=False so only truly fatal errors (missing fields, dead ends, bad JSON) cause a hard failure. Cross-reference issues are minor and fixable in the tree editor. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>