feat: unifiber v1

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  schedule:
+    - cron: '0 6 * * *' # daily: React Native nightly changes every day
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        mode: [development, production]
+        rn: ['0.87', '0.86']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - run: bun install --frozen-lockfile
+      - run: npm run typecheck
+      - run: npm test
+        env:
+          UNIFIBER_MODE: ${{ matrix.mode }}
+          UNIFIBER_RN: ${{ matrix.rn }}
+
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - run: bun install --frozen-lockfile
+      - run: npm run coverage
+
+  nightly:
+    # RN nightly + the React it targets (RN bundles a renderer built from React main). Never blocks a merge.
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    strategy:
+      fail-fast: false
+      matrix:
+        mode: [development, production]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - run: bun install --frozen-lockfile
+      - name: React Native nightly + the React it targets
+        run: |
+          REACT_RANGE="$(npm view react-native@nightly peerDependencies.react)"
+          REACT_VERSION="$(npm view "react@${REACT_RANGE}" version --json | node -e "const v = JSON.parse(require('fs').readFileSync(0, 'utf8')); console.log(Array.isArray(v) ? v.at(-1) : v)")"
+          bun add -d react-native@nightly @react-native/babel-preset@nightly "react@${REACT_VERSION}"
+          node -e "console.log('react-native', require('react-native/package.json').version, '/ react', require('react/package.json').version)"
+      - run: npm test
+        env:
+          UNIFIBER_MODE: ${{ matrix.mode }}

.gitignore

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+node_modules/
+bench/out/
+coverage/
+*.lcov
+.DS_Store

LICENSE

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+MIT License
+
+Copyright (c) 2026 Jacek Pudysz
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+<div align="center">
+
+# unifiber
+
+**One small, tested place for everything React Native styling libraries read from React's private fiber tree.**
+
+Built for [Unistyles](https://github.com/jpudysz/react-native-unistyles) and Uniwind Pro.
+
+`React 19` · `React Native 0.86 – 0.87` · `iOS + Android` · `Hermes-first` · `MIT`
+
+</div>
+
+---
+
+## Why this exists
+
+Unistyles and Uniwind both do something React Native doesn't officially support: they update the native shadow tree **without a React render**. Theme switches, breakpoints and insets reach native views in a single commit. To do that, both read React's private fiber fields: `__internalInstanceHandle`, `stateNode.node`, `memoizedState`, `return`, `alternate` and more.
+
+Until now, each library kept its own copy of those reads. They drifted apart, and both had bugs that only show up on real apps.
+
+unifiber is the one module that knows what a fiber looks like. It answers questions such as "which native view is this ref?", "is it hidden, and why?" and "what must refresh?". It's tested against **React Native's own components** and **Unistyles' real code**. A daily CI run against React Native nightly catches changes to React's internals before they ship.
+
+## API
+
+`Fiber` and `Reanimated` are plain objects. A **`Host`** is a native view's creation fiber behind an opaque type: free to keep, and stable, so the same view is always the same `Host` (`===` and `WeakMap` keys work).
+
+### ref → Host
+| | |
+|---|---|
+| `getHostFor(ref)` | Native-view refs, RN composites (ScrollView, FlatList / SectionList / VirtualizedList, ImageBackground, KeyboardAvoidingView, RefreshControl), and class components that render their view directly (Button on Android). Call once per link and keep the result. |
+| `getShadowNodeFor(ref)` | Hot path when you don't keep a Host. |
+| `getHostForInstanceHandle(handle)` | For fibers handed back from C++ (`ShadowNodeFamily::getInstanceHandle`). |
+| `getContentContainerFor(ref)` | ScrollView / list content container, through RN's public `getInnerViewRef()`. |
+
+### Host → native
+| | |
+|---|---|
+| `getShadowNode(host)` | The node in React's `stateNode.node` wrapper. |
+| `getShadowNodes(host, out?)` | Every node React may diff against or re-attach: one after a commit, two while a render is in flight. |
+| `getNativeTag(host)` | `undefined` once the view has unmounted. |
+| `getParentHost(host)` | The nearest native view above (ActivityIndicator's wrapper, on both platforms). |
+| `patchRenderedProps(host, patch)` | Replaces React's diff baseline on both halves. **The only write**, used by Uniwind's baseline. |
+
+### Hidden state
+| | |
+|---|---|
+| `isHidden(host)` | Inside a Suspense fallback, a frozen screen or a hidden `<Activity>`: suspend instead of unlinking. |
+| `isSuspended` · `isFrozen` · `isInHiddenActivity` | Why. Frozen means react-freeze (react-native-screens `freezeOnBlur`, react-navigation). |
+| `collectVisibleAncestors(hosts, visit)` | Batch refresh. Each visible native view from `hosts` up to the root, visited once, in one shared pass. |
+| `collectAncestors(hosts, visit)` | The same walk, with hidden views included. These are the semantics of Uniwind's `collectHostNodes` today. |
+
+### Diagnostics
+| | |
+|---|---|
+| `verify(host, expected)` | Style keys React would re-send, i.e. undo, on this view's next render. |
+| `getOwners(host)` | *Development builds only:* the components that created the view, e.g. `['ProfileCard', 'ProfileScreen']`. |
+| `getCreationStack(host)` | *Development builds only:* where the JSX was written, for Metro to symbolicate. |
+
+### Adapters: when a 3rd-party component owns the view
+Reanimated's `AnimatedComponent` keeps its own copy of a view's style for CSS transitions, so a native-only theme change gets overridden. The adapter keeps that copy in sync, so the theme change **animates** instead.
+
+```ts
+const owners = Fiber.createOwnerRegistry({
+    name: 'unistyles',
+    epoch: () => themeVersion,                     // bump on every runtime change
+    contexts: [ScopedThemeContext],
+    contextKey: (_ctx, scope) => scope?.name,      // stable scopes are renamed in place
+    resolve: (props, read) => freshStyles(props, read(ScopedThemeContext)),
+}, [Reanimated.cssAdapter], warnOnce)
+
+owners.link(host)        // in the link path: ~86 ns for a plain view
+owners.refresh(hosts)    // after a native-only update
+```
+
+An adapter that throws is switched off for the session and reported once. Private Reanimated fields are pinned by a contract test against the 4.5.1 and 4.7.0 sources.
+
+## Compatibility
+
+| | |
+|---|---|
+| React | 19.2, and 19.3.1 with RN nightly (fiber tags pinned for 19.x) |
+| React Native | 0.87.1, 0.86.3 · iOS, Android · development and production. CI also runs React Native **nightly** (main) every day; 0.89.0-nightly-20261016 passes |
+| Reanimated | 4.5.1, 4.7.0 |
+| Unistyles | 3.5.3 and `main` (its real code runs in the suite) |
+| Uniwind | its lookups copied verbatim into the suite |
+| Engine | Hermes (legacy Hermes benchmarked) |
+
+## License
+
+MIT

bench/build.mjs

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+// esbuild bundle of a bench entry with the production renderer. Imports are hoisted: use metro.mjs for app numbers.
+import path from 'node:path'
+import { createRequire } from 'node:module'
+
+const require = createRequire(import.meta.url)
+const { ESBUILD, RN, REACT, SCHEDULER } = require('../test/harness/paths.cjs')
+const esbuild = require(ESBUILD)
+const map = {
+    react: path.join(REACT, 'cjs', 'react.production.js'),
+    scheduler: path.join(SCHEDULER, 'cjs', 'scheduler-unstable_mock.production.js'),
+    'react-native-renderer': path.join(RN, 'Libraries', 'Renderer', 'implementations', 'ReactFabric-prod.js'),
+}
+const [entry, out] = process.argv.slice(2)
+await esbuild.build({
+    entryPoints: [entry],
+    outfile: out,
+    bundle: true,
+    format: 'iife',
+    target: 'es2019', // Hermes: no class fields / ?? lowering issues
+    define: { 'process.env.NODE_ENV': '"production"', __DEV__: 'false' },
+    plugins: [{
+        name: 'rn',
+        setup(build) {
+            build.onResolve({ filter: /^(react|scheduler|react-native-renderer)$/ }, (a) => ({ path: map[a.path] }))
+            build.onResolve({ filter: /(ReactNativePrivateInterface|react-native\/react-private-interface)$/ }, () => ({ path: 'pi', namespace: 'stub' }))
+            build.onResolve({ filter: /(ReactNativePrivateInitializeCore|react-native\/setup-env)$/ }, () => ({ path: 'init', namespace: 'stub' }))
+            build.onLoad({ filter: /.*/, namespace: 'stub' }, (a) => ({
+                contents: a.path === 'pi' ? 'module.exports = globalThis.__unifiberPrivateInterface' : '',
+                loader: 'js',
+            }))
+        },
+    }],
+    logLevel: 'warning',
+})