This skill is specific to the s1a repository, where an agent is one module under s1a/agents/ that ends in a frozen SPEC, while the loop, decision-model layer, rethink rail, job folders and CLI are shared. It starts with a one-message intake of five facts: the task and what a finished episode looks like, where state comes from, how options are listed at each step, the score and any baseline, and whether a step needs arithmetic, constraint deduction, search or generated text, which counts as a stop.
A fit gate comes before any code. You write 8 to 12 hand-made cases as JSONL and run uv run s1a probe, which reports fits at 80 percent or more over at least 8 cases, too few cases below 8, or not a decision-model task. A wrong case that needed deduction or arithmetic stops the work even if the total passes. The agent then chooses a front (tool, browser or rail), copies the matching template, and writes the module, a test and a README row. Reference files describe the fit rule, the three fronts and state design.