Constraining the Coding Agent: The Ralph Loop and Why Determinism Matters
In late 2025, agentic coding tools went from impressive demos to daily infrastructure. The problem nobody talked about enough: when an LLM agent has write access to a codebase and no formal constraints, reproducibility breaks down. The Ralph Loop is a story-driven harness intended to bound that variability through one model invocation per attempt, scoped writes, and atomic state. These constraints make runs easier to inspect; they do not make an unpinned model deterministic.