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+# GPUI desktop port — architecture & plan
+
+Captured 2026-07-28. Owner decisions this session:
+
+- **Full 1:1 port** of the editor to GPUI. Linux-first; macOS/Windows not targeted for now, BSD parked (GPUI support unproven).
+- **In-process ffmpeg** via `ffmpeg-next` for decode AND encode. No subprocess.
+- **Licensing is not a constraint** — x264 (GPL) is the H.264 encoder; quality over AppImage-ability. The documented OpenH264 dead end (ignores bitrate, undershoots ~10x) is bypassed entirely.
+- Web version stays and keeps working; the browser editor remains a feature.
+
+## Why the port
+
+Browser inconsistency (WebGPU quirks, encoder behavior varying by browser)
+keeps producing walls. A native app gives one controlled runtime: wgpu +
+ffmpeg, one decoder, one encoder, one compositor.
+
+## What "backend" means here
+
+There is no server worth porting: the Next.js backend is an auth scaffold
+(no flows implemented), a health route, and a sounds proxy (sounds are
+feature-flagged off). The real "backend" is the offline project store
+(IndexedDB) — on desktop it becomes a plain filesystem layout per project.
+So: no Rust server, no API. Everything lives in the app process.
+
+## Crate map
+
+Existing, reused natively as-is (already target-agnostic):
+
+- `rust/crates/time` — media time, frame rate, timecode
+- `rust/crates/compositor` + `effects` + `masks` + `gpu` — wgpu compositor,
+  WGSL effect pipeline, SDF mask feathering. The web drives this through
+  wasm; desktop links it directly.
+
+New crates:
+
+- `scene` — project/scene graph model, serde, `.ocp` project.json compat
+  (round-trip proven against the web's SerializedProject shape).
+- `timeline` — tracks, elements, placement, snapping, split/trim/resize,
+  ripple, grouping. Pure logic, no UI.
+- `animation` — keyframes, bezier interpolation, channel sampling.
+- `commands` — undo/redo command stack (ports `apps/web/src/commands`).
+- `media` — ffmpeg-next demux/decode, frame pipeline to GPU textures,
+  thumbnails, waveform extraction.
+- `audio` — decode, mixing, rate stretching, mastering.
+- `encode` — export pipeline: compositor frames → x264/VP9, muxing.
+- `transfer` — `.ocp` zip container build/parse (cross-compat with the web's
+  fflate archives proven in both directions).
+- `storage` — project dirs on disk, per-project media store, autosave,
+  `.ocp` import/export (replaces IndexedDB; stays offline-first).
+- `text` — text layout/measure/raster via cosmic-text (ports
+  `apps/web/src/text`).
+- `graphics` — gradient parser + shape raster via tiny-skia (ports
+  `apps/web/src/graphics` + `gradients`).
+- `effect-defs` — effect definitions registry: params → WGSL pass
+  descriptors (ports `apps/web/src/effects/definitions`).
+- `mask-defs` — mask shape renderers via tiny-skia (ports
+  `apps/web/src/masks/builtin` + `freeform`).
+- `renderer` — scene → node tree → resolve at time t → compositor
+  FrameDescriptor (ports `apps/web/src/services/renderer`). Integration hub;
+  starts once the leaf crates land.
+- `playback` — clock, frame scheduling, audio sync.
+
+`apps/desktop` (GPUI) holds UI only; all logic lives in crates so the web
+version can adopt them later via wasm where it makes sense.
+
+## Compositor → GPUI bridge
+
+GPUI does not expose its internal GPU device. v1 approach: the compositor
+owns its own wgpu device, renders the frame to an offscreen texture,
+reads back, and paints it as a `gpui::Image` in a custom element. ~8 MB
+per 1080p frame — fine for preview; revisit if profiling says otherwise.
+
+## Milestones (each runnable)
+
+1. **Environment** — nix devshell with rust + GPUI native deps + ffmpeg dev.
+2. **Domain model** — `scene` crate: full project/scene/element model
+   ported from `apps/web/src/timeline/types.ts` + scene managers, `.ocp`
+   round-trip compat proven against web-generated archives.
+3. **Timeline core** — `timeline`, `animation`, `commands` crates with
+   ported unit tests (web test suite is the behavior spec).
+4. **Media** — `media`/`audio` crates: decode → texture, waveform,
+   thumbnails.
+5. **Compositor bridge** — scene resolve → wgpu frame → GPUI preview.
+6. **GPUI UI** — projects screen, editor layout, timeline UI (drag, trim,
+   split, snap, ripple), preview overlays/selection, all panels.
+7. **Export** — `encode` crate + dialog, x264 quality ladder.
+8. **Features** — versions, voiceover (cpal), clipboard, keybindings,
+   `.ocp` import/export.
+9. **Packaging** — .desktop entry, binary distribution. AppImage optional.
+
+## Port rules
+
+- Web behavior is the spec. Where the web has unit tests, port the test
+  with the code.
+- Flagged-off web features (sounds, stickers, effects domains) are NOT
+  ported — they are slated for deletion upstream of us.
+- `.ocp` archives must round-trip between web and desktop.
+- No parallel divergence in shared crates: `compositor`/`time` changes must
+  keep compiling for `wasm32`.