Proactive checkpoint guard fires at each wave boundary before spawning agents. Self-assesses context pressure against context-budget.md degradation tiers and warns (warn, default) or auto-invokes /gsd:pause-work (auto) when POOR tier (70%+) is detected. Config key validated; defaults to \"warn\". Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>