An XRR fitting procedure for a laboratory LLM agent

A written procedure for fitting a measured X-ray reflectivity curve, elicited from an expert at the keyboard and written so that a language-model agent can follow it without further instruction. Thirteen numbered sections and a 22-item report template. From version 2.0 the laboratory's constants are in a separate preset file, validated against a schema, with a substrate library and a validator. The record carries the final procedure (v5.0.2) and the five versions the qualification, transfer and W/B4C sessions actually received, each with its checksum, together with what transferred between material systems and what did not: the conditioning steps transferred, the rules of verdict did not. The procedure is written against X-Ray Calc 3, the laboratory's X-ray reflectivity simulation and fitting program (https://github.com/OleksiyPenkov/X-RayCalc3). The program supplies the optical model, the cost function and the optimizer; the procedure supplies the conditioning of the curve and the acceptance of the fit, which the program does not decide.