"Don't build another one of the world's pointless health apps. Build the AI daughter who takes care of Dad's health — projected as an app." — Dad, the north star
The One-Sentence Version
Forge is an engine that owns structured health facts — symptoms, training sessions, doses, measurements, medical documents, meals — while the brain that interprets all of it lives somewhere else entirely. Say that split out loud, because it is the whole design: Forge owns the health facts; cwkPippa owns the judgment. Everything else in this quest is a consequence of taking that one boundary seriously.
Look at what Forge deliberately is not. It is not a second Pippa — no soul, no memory vault, no model router of its own. It is not a symptom checker — it never returns a ranked list of conditions. It is not a medication reminder — there is no schedule table and no adherence machinery. It is not a rich prose editor — long writing round-trips to a sibling built for it. It is not a fitness tracker whose reason to exist is syncing a wearable. Strip away everything a sibling already owns, and what remains is the real product: a health domain, honestly kept.
Four Layers, Kept Distinct
The domain model has four layers, and keeping them separate is the architecture:
A raw crumb is never overwritten. An interpretation can be thrown away and regenerated from the crumb it read. An aggregate is pure math you could run by hand. Narration is the only layer where judgment speaks — and it always points back down at the crumb IDs it stands on. Once you can see those four layers clearly, the rest of Forge stops looking like a pile of features and starts looking like one honest pipeline.
Why an Engine, Not an App
Calling Forge an engine instead of an app is not swagger. An app is defined by its screens; an engine is defined by what it owns. Screens are replaceable — the Stream composer, the Analysis tab, a future briefing view are all clients of the same crumb store. Define Forge by its UI and every redesign forces you to redraw the definition. Define it by ownership — crumbs, interpretations, analyses, and the lineage between them — and you get a boundary that outlives every redesign. It is the same lens that made Ember an image engine and Waystone a travel engine: the model is the product, the view is output.