chore: import upstream snapshot with attribution

2026-07-13 12:58:35 +08:00
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+# Translation limitations
+
+What the skill explicitly cannot translate, separated from the
+blocker-list (which is enforced by `lint_source.py`). These are
+_known_ gaps — surface them to the user as translation notes
+when translating the surrounding composition.
+
+## React patterns the skill refuses
+
+See [escape-hatch.md](escape-hatch.md). Any of these triggers
+a bow-out:
+
+- `useState`, `useReducer` driving animation
+- `useEffect` / `useLayoutEffect` with non-empty deps (side effects)
+- async `calculateMetadata`
+- Third-party React UI libraries (MUI, Chakra, Mantine, antd, shadcn, Radix, NextUI)
+
+`@remotion/lambda` is no longer in this list — it's a warning, not a
+blocker, because Lambda config is orthogonal to composition rendering.
+The skill drops the imports and `renderMediaOnLambda(...)` calls and
+writes a `TRANSLATION_NOTES.md` entry. See
+[escape-hatch.md](escape-hatch.md).
+
+## Patterns that work with caveats
+
+### Volume ramps on `<Audio>`
+
+Remotion accepts a function for `volume`:
+
+```tsx
+<Audio src={...} volume={(f) => interpolate(f, [0, 30], [0, 1])} />
+```
+
+HF supports static `data-volume` only. Translation: bake the ramp into
+the audio file at translation time using `ffmpeg afade`, OR drop the
+ramp with a note. The dropped-ramp path produces audibly different
+output but visually-identical video, so SSIM passes — just flag it.
+
+### `<Loop>` with stateful children
+
+```tsx
+<Loop durationInFrames={30}>
+  <CounterThatIncrementsViaUseRef />
+</Loop>
+```
+
+Loop with `repeat: -1` works for _visual_ repetition. If the looped
+child has cross-iteration state (a counter, a randomness seed), HF
+won't reproduce it identically per iteration. Bow out unless the
+child is fully deterministic per-iteration.
+
+### Remotion's `<Img>` with crossOrigin
+
+```tsx
+<Img src="https://other-domain.com/x.png" crossOrigin="anonymous" />
+```
+
+HF's renderer doesn't enforce CORS the same way Remotion does. Most
+public images work; private images served with auth headers won't.
+If the source uses `crossOrigin="use-credentials"`, the asset needs
+to be downloaded and inlined at translation time.
+
+### Custom `presentation` in `<TransitionSeries>`
+
+```tsx
+const customPresentation: PresentationComponent = ({ children, presentationProgress }) => {
+  return <div style={{ filter: `blur(${(1 - presentationProgress) * 20}px)` }}>{children}</div>;
+};
+```
+
+Pure presentations (transform/filter/opacity computed from progress)
+translate to GSAP tweens cleanly. Presentations that read
+`useCurrentFrame()` internally or have stateful children don't —
+bow out.
+
+### Code-split components (`React.lazy`)
+
+```tsx
+const HeavyChart = React.lazy(() => import("./HeavyChart"));
+```
+
+`React.lazy` is async and doesn't fit the deterministic-render model.
+Translate to a regular import; the resulting HF composition will
+just include all the code upfront.
+
+## Patterns that always work
+
+- `<AbsoluteFill>` and `<Sequence>` (any nesting)
+- `useCurrentFrame()` derivations: `interpolate`, `spring`, `Easing`,
+  `interpolateColors`, manual math
+- `<Audio>`, `<Video>`, `<Img>`, `<IFrame>` with simple props
+- `staticFile()` references
+- Custom React subcomponents that are pure functions of props
+- Custom hooks that are pure derivations of `useCurrentFrame`
+- `@remotion/lottie` (translates to HF's Lottie adapter)
+- `@remotion/google-fonts/<Family>` (translates to `<link>` or `@font-face`)
+- Sync `calculateMetadata` (resolved at translation time)
+- `<TransitionSeries>` with built-in presentations (`fade`, `slide`,
+  `wipe`, `clockWipe`, `flip`, `iris`)
+
+## What the skill never tries to translate
+
+These are out-of-scope by design:
+
+- **HDR rendering** — HF supports HDR but Remotion doesn't, so there's
+  nothing to translate from.
+- **Variable frame rate** — both tools assume constant fps.
+- **Multi-composition `<Composition>` lists** — translate one at a
+  time. The skill prompts the user to choose which composition.
+- **Remotion Studio props panel** — visual prop editing in HF Studio
+  needs different infrastructure; out of scope.
+
+## Reporting gaps to the user
+
+When translation produces _something_ but the something has gaps, write
+a `TRANSLATION_NOTES.md` next to the output:
+
+```markdown
+# Translation notes
+
+The following Remotion patterns were translated with caveats:
+
+- `<Audio volume={(f) => ...}>` (line 15): volume ramp dropped — added
+  static `data-volume="0.5"`. To preserve the ramp, run
+  `ffmpeg -i music.wav -af "afade=t=in:st=0:d=1" music.faded.wav` and
+  swap the source file.
+- `<HeavyChart>` (line 30): translated as inline HTML. The original
+  React.lazy boundary was dropped — bundle size unchanged because HF
+  serves a single HTML file.
+
+If any of these caveats matter, consider the runtime interop pattern
+instead.
+```
+
+This file is also generated by the skill alongside the HF output, not
+held in the corpus.