FUSION: a skill-based research agent for publicly obtainable nuclear-physics codes
Authors: Jin Lei
Organizations: School of Physics Science and Engineering, Tongji University, Shanghai 200092, China. · Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences, Huizhou 516000, Guangdong Province, China.
Running an unfamiliar nuclear-physics code is rarely difficult because of the physics alone. One must find and build the program, learn its input conventions, and decide whether a plausible output is actually correct. A general-purpose coding agent helps with the first two tasks but may make the last one harder: it can write an input file that runs with the wrong physical convention. FUSION addresses this problem with code-specific skills. A skill obtains the code from its public source, starts from a verified input, runs and parses the calculation, records known failure modes, and must reproduce a stated benchmark to a stated tolerance before reporting a result. The current release covers twenty codes, spanning optical models and reactions, nuclear structure, fission and statistical models, astrophysics and R-matrix analysis, and heavy-ion transport. It also includes an offline, searchable collection of 61 167 pages derived from the nucl-th literature. User notes and credentials remain outside the public repository. FUSION is available under the MIT license at https://github.com/jinleiphys/FUSION; documentation is at https://vibeinscience.com. Here I describe the design, the checks behind the current release, and one complete calculation from input to comparison with measured data.
Figures & tables
Figure 1: The failure mode and the fix. (a) A general-purpose assistant writes the input from memory; the code runs and prints a number, and a wrong convention is invisible. (b) A FUSION skill starts from a verified example deck and ends with a benchmark check whose agreement is stated in significant figures.
Figure 2: The three layers. The engine and the nuclear-physics layer ship in the clone; the private layer is a mount point the platform defines but never fills. The physics codes belong to none of the three and are obtained from their authors.
Figure 3: Anatomy of a skill, using FRESCO as the example. The layout is typical rather than fixed: a scope document, verified examples, reference notes, and scripts that install, run and check, with the potential-parameter script carrying its own self-test.
Figure 4: The twenty codes with a FUSION skill, grouped by area, with the language each is written in. The selection is bounded by an openness rule, not by a ranking: a code qualifies only if it is publicly obtainable, builds from source on the target platform, and has a published paper.
Figure 5: How a skill is verified before it ships. The adversarial review loops back to the build until a round returns no new defect of the kind the previous round repaired.
Figure 6: Adversarial review of one skill (SMASH), round by round. Pink marks defects introduced by the fixes of the previous round. The review stops when a round returns without a new defect of that kind.
Figure 7: What each skill’s benchmark rests on. Green: reproduction of a stored result (the code’s own reference, a published number, or bit identity across builds). Pink: a check that does not depend on any stored output (a physics invariant, an analytic solution, measured data, or an independent code). The right column gives the recorded agreement.
Figure 8: What ships (left) and how the 703 430 in-corpus citations divide by type (right). A contrasts edge records disagreement with the cited paper and survived a focused second-pass check.
Figure 9: One page of the knowledge base, with the origin of each part. Only the metadata and the abstract are the paper’s own; the digest sections are model-written and say so in the header; the citation sections are computed from the corpus.
Figure 10: The figure the session produced. Green is the zero-free-parameter KD02 prediction computed with FRESCO through the skill; pink points are EXFOR measurements. Left: 24 MeV, enriched 90 Zr, full angular range (Wang and Rapaport, EXFOR 13160.004). Right: 55 MeV, natural Zr, forward angles (Ibaraki et al., TIARA, EXFOR 22480.005). There is no 50 MeV panel because no measurement exists at that energy.