AI agent receives GitLab MR webhook with action='update' but empty 'changes': {} payload, breaking logic expecting changes details (e.g., label/assignee/reviewer/state diffs). Triggers unexpectedly without useful delta info, causing skipped automations or false processing.

GitLab intentionally triggers MR 'update' webhooks for certain activities (approvals, rule changes, thread resolutions, re-reviews) where no tracked attributes change, resulting in empty 'changes' object despite documentation warning receivers to always inspect it. Some changes (e.g., certain assignee/reviewer updates in group hooks) inconsistently populate 'changes' due to backend logic or version-specific behavior around Oct 2024 (GitLab ~17.5).