2026-07-20 — Prompt composition: variables, the registry, and the two-view Brain

The Prompt is now a typed composition. Owners build their strategy from named ; the platform's rulebook lives in a runtime-editable APPEND-ONLY registry; every published agent version freezes exactly what it renders (user_vars + universal_pins, both hash-covered), and a registry edit becomes a prompted upgrade — apply mints a pins-only new version, revert restores the prior exact bytes.

Built as a self-contained pipeline: the pure @numero/prompt-engine package (frames, grammar, render, validation — proven byte-identical to the historical prompt join by a parity fixture before anything moved), the prompt_variables/prompt_variable_revisions registry (migrations 0099/0101), publish-transaction validation (prompt_ref_undefined refusals leave the draft intact), seat-time pin resolution in hosted-agent-service, capture provenance, and the Lab's Basic ⇄ Fine-tune Brain composer over one useComposition state.

Current-state pages: prompt composition · agent versions · decision capture