Component Shape — 7 Orthogonal Axes
In blueprint: these are the presets'
componentShapeaxes. The named triage rules (max-params,max-statements,max-lines) land in the generated lint config as entry points; the verdicts compile into your handbook and agent contract.
How a component / composable should be shaped, in seven axes. A set, not a pipeline: each axis is an independent yes/no design decision — never infer that one axis holds because another does. Numbering is identity, not order, and trivial changes need not force the full pass.
Almost everything here is ◐/○ — component shape is design judgment, which is exactly belief #7. Lint metrics are entry points; the verdict stays with review.
1. Ownership Inversion — the unit that needs derived state owns the derivation
Do not precompute in the parent and drill the result down; the child imports the hook and derives it itself. Field-tested: a 17-prop component down to 7.
2. IO Shrinkage — narrow the inputs, shrink the outputs
Three moves: split a multi-concern unit; collapse parallel raw states carrying an invariant into one modeled state; merge symmetric twins into one object of the same shape. Count and size are weak signals — whether the state is modeled is the review call. Triage: max-params.
3. SRP Decomposition — split on responsibility boundaries, not size
Naming test: if you cannot name it without "and", it wants splitting. Dissolving code into an existing home is also a split. Exception: writable state that must stay in sync — force-splitting it manufactures sync bugs. Triage: max-statements.
4. Orchestration Shell — a page only orchestrates
Route/id resolution, the loading shell, shared sources, cross-child lifecycle — never deriving values on behalf of each child. Field-tested: a 6666-line detail page down to 552. Triage: max-lines on pages.
5. Scoped Writable State — the lowest common owner of writers and readers
Hoist only what is genuinely shared across a boundary; state that must survive a route change goes to the URL or a store. "Might be shared later" is YAGNI — hoist when the sharing arrives.
6. Lifecycle Internalization — if lifecycle is part of the responsibility, build it in
The caller receives a unit that is already running and cleans itself up — not a kit of handlers to wire into onMounted / useEffect. Field-tested: 19 exports down to a one-line call.
7. Pure Helpers ≠ Composables — keep pure functions out of reactive units
One exported function does not demand one file: responsibility splits at the function level; the file splits only when max-lines approaches. Expose the decision a unit makes, not its raw ingredients.
Lint vs review, across all seven axes: a unit can be small, low-complexity, low fan-out — all green — and still be a raw-state dump, or store its derivation in a mutable ref. Metrics cannot see any of that. A lint warning is where review starts.