feat: lightweight react-reconciler-compatible reconciler

[aidenybai]

Summary

Adds bippy/reconciler: a compact react-reconciler-compatible reconciler (~13.7 kB ESM / 5.2 kB gzip vs react-reconciler's ~398 kB min / 65 kB gzip), inspired by Cody Bennett's react-nylon.

import { createReconciler } from "bippy/reconciler";

const reconciler = createReconciler(hostConfig); // same host-config shape as react-reconciler
const root = reconciler.createContainer(container);
reconciler.updateContainer(<App />, root);

• Own tiny fiber tree that satisfies bippy's isFiber, plus DevTools-hook injection (getRDTHook().inject + onCommitFiberRoot), so bippy instrument() observes custom renderers built on it.
• React 19 dispatcher interop (__CLIENT_INTERNALS... with legacy __SECRET_INTERNALS... fallback) with a broad hook dispatcher (useState/useReducer/useEffect/useLayoutEffect/useInsertionEffect/useContext/useSyncExternalStore/useTransition/useOptimistic/use/...).
• Supports function/class components, keyed reconciliation, iterables/fragments, refs (attach/detach/swap), context (provider + Context.Consumer render props), portals, error boundaries, basic thenable/Suspense handling, flushSync/act.
• Class lifecycles: componentDidMount / componentDidUpdate / componentWillUnmount (including for class components nested inside host instances — deletion now walks the whole subtree for effect cleanup/lifecycles via commitDeletionEffects, separate from host-node removal).
• React 19 ref-as-prop compat: refs are read from props.ref (never the deprecated warning element.ref getter) and stripped from host props.

Compatibility

Not 1:1 with React's reconciler — lanes/priorities, hydration, and host context are intentionally omitted to stay tiny. Representative tests ported from react-reconciler's suite (ReactFragment, ReactFiberRefs, class components/setState callback/lifecycles, ReactHooksWithNoopRenderer, ReactNewContext, ReactFlushSync, ReactIncrementalSideEffects, ReactMemo) run against a noop host config in tests/react-reconciler-compat.test.tsx — all pass. Porting them surfaced and fixed real gaps:

• stale dispatch: updater functions captured on mount now resolve state from queue.lastRenderedState instead of a stale fiber's memoizedState
• context value updates were dropped on re-render (_context lost in updateElement)
• Context.Consumer element types were collapsed to their $$typeof symbol and never rendered
• ref swaps (ref={ref1} → ref={ref2}) now detach the old ref, and refs only re-attach when changed (callback refs no longer re-fire every commit)

Testing

• pnpm --filter bippy test: 629 passed, 2 skipped
• pnpm check, tsc --noEmit, pnpm --filter bippy build all green

Link to Devin session: https://app.devin.ai/sessions/0965b0b326de4f2fa5da504f2d60cd55
Open in Devin Desktop: https://app.devin.ai/desktop/session/0965b0b326de4f2fa5da504f2d60cd55?variant=devin
Requested by: @aidenybai

[devin-ai-integration]

Original prompt from Aiden Bai

in bippy, create a lighter weight version of react-reconciler but w full compat. cody j barret had something similar fo rthis

then impl a react-nil clone but interare and super lgithweigth. then PR

[devin-ai-integration]

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Project	Deployment	Actions	Updated (UTC)
bippy	Ready	Preview	Aug 28, 2026 8:57am

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commit: 5d74d60