NL2Test: 85.4% code adoption across nine months and 3,196 production regression tests.

An experience paper on a pipeline that takes a natural-language scenario plus captured production traffic, uses the LLM only for semantic interpretation and constrained code synthesis, and hands reliability-critical parts to deterministic algorithms: request filtering, dependency validation by value consistency, assertion-path validation. 85.4% code adoption, 82.4% exact match (42 of 51 scenarios), 98.0% producing usable drafts with minor edits. Two design choices worth copying: bind dynamic values from prior responses rather than hard-coding, and exclude non-deterministic fields from assertions. (arXiv 2607.24000)