Pattern: The "Gauntlet Loop" — Never Let the Builder Grade Itself, and Give the Critic a Real Artifact to Beat

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Matt Shumer's Gauntlet Loop, which went viral this week after a single-prompt Claude-built FPS drew 3.8M views, is a three-rule agentic pattern: the lead agent (not the human) decomposes the goal into independently judgeable pieces, each piece gets a specialist builder subagent plus a blind critic subagent with fresh context, and the critic only passes work that beats a concrete real-world reference it can inspect — actual Call of Duty screenshots for the game, or a reference site, writing sample, or test suite for other domains. There is no fixed round count; the loop runs until the output beats the bar or gains go negligible. Reported Claude Code settings are Opus 5 with `/effort ultracode` and the `/loop` skill for repetition; an r/ClaudeAI replication on a 3D platformer burned three consecutive 5-hour Opus windows, which is the real cost signal to plan around.