References — fw-02 mini-react I: Elements, Rendering, Reconciliation, State

Primary sources first. Read the real implementation after you have written yours, never before.

Build-it-yourself guides (compare against yours after)

Rodrigo Pombo — Build your own React — the best step-by-step derivation available; deliberately mirrors React's real structure.
Preact source — a complete, production, 3 kB React-compatible implementation. Small enough to read fully, real enough to trust.

React internals

React Fiber Architecture — Andrew Clark. Still the clearest written explanation of the fiber data structure.
react-reconciler — the real thing. Dense; approach only after fw-04.
React docs — Preserving and resetting state — the user-facing consequence of reconciliation identity
React docs — Rendering lists / keys
React RFCs — design rationale, including hooks

Why a virtual DOM at all

React docs — Reconciliation (legacy) — the O(n) heuristic and its two assumptions
Rich Harris — Virtual DOM is pure overhead — the strongest argument against; read it and decide whether you agree, because fw-03 builds the alternative.

fw-04 — Batching, scheduling, deriving Fiber — stages 8–11, deliberately deferred
fw-03 — Reactivity & signals — the competing model
bi-04 — DOM internals — the DOM cost model this module's central bet depends on
fe-01 — Execution model (sibling project) — why React's scheduler uses MessageChannel, measured

When a claim here proves stale, record it in PROGRESS.md section 7.