# Show HN: FableCut – A browser video editor AI agents can drive (zero deps) > Source: > Published: 2026-07-09 13:23:10+00:00 **A browser video editor that AI agents can drive.** FableCut is a Premiere-style non-linear video editor that runs entirely in your browser — and exposes its whole timeline as one JSON document. Edit it by hand, from the UI, or let an AI agent (Claude Code, Claude Desktop, or anything that speaks MCP/REST) cut your video for you while you watch the timeline update live. Zero npm dependencies. One `node server.js` . That's it. Most "AI video" tools hide the edit behind an API. FableCut flips that: the **project file is the interface**. `project.json` describes media, clips, tracks, effects, keyframes and transitions — any process that can write JSON can edit video, and the open browser UI hot-reloads within ~150 ms via server-sent events. A human and an agent can work on the same timeline at the same time. **Editing** - 4 video tracks + 3 audio tracks, drag/trim/split/snap, undo/redo **Timeline multi-select**— rubber-band marquee (drag on empty track area),`Ctrl/Cmd/Shift+click` to add/remove clips,`Ctrl+A` to select all,`Esc` to deselect. Drag any selected clip to move the whole group;`Delete` removes all selected;`S` splits all selected at the playhead. Inspector shows an "N clips selected" banner.- Beat & cue markers (tap `M` on the beat during playback) with edge snapping - Real decoded audio waveforms on clips - Canvas aspect presets (16:9, 9:16 reels, 4:5, 1:1) + safe-area guides **Look** - 12 one-click filter presets (cinematic, teal-orange, noir, vintage, cyberpunk…) **Adjustment layers**— one clip grades everything below it, Premiere-style- Full grade controls: brightness/contrast/saturation/hue, **temperature & tint**, blur, grayscale/sepia/invert,** vignette**, animated** film grain** - Blend modes (screen, multiply, overlay…), fit modes (contain/cover/stretch), per-edge cropping, corner radius, flip H/V **Chroma key**(green screen) with tolerance/softness + spill suppression** AI background removal**(person cut-out, in-browser via MediaPipe) **Motion** - Keyframe animation on ~25 properties with easing **Speed ramps**— keyframe`speed` and the engine time-remaps video*and*the export audio mix (the fast-into-slow-mo reel move)**Camera shake** and**RGB-split/chromatic aberration**, both animatable- 17 transitions: fades, slides, wipes (4 directions), zoom, iris, spin, blur, whip-pan, **glitch**,** pop** **Text** - Kinetic captions: typewriter, word-pop, word-slide, karaoke, **letter-pop**,** wave**,** bounce**,** shake** **Neon glow** for that TikTok caption look- Font editor: system fonts, drop-in custom fonts ( `library/fonts/` ), and**any Google Font by name**— loaded automatically - Gradient fills, outline, background pills, letter-spacing, line-height, weights, italic, uppercase, alignment, soft shadows **Animated SVG clips** - A first-class `svg` clip kind: CSS-`@keyframes` -animated SVGs render**frame-accurately** in preview and export (the compositor freezes the animation at any time). Agents can author their own vector overlays — lower-thirds, confetti, sparkles — as plain`.svg` files. Starters included. **Remake a reference video** - Give it a reference edit (a reel you like) and get back an **edit blueprint**: shot boundaries, music beats + BPM, a loudness curve, per-shot energy, the drop — plus the reference's** music track extracted**into your media, ready to rebuild the same idea with your own footage. Zero extra dependencies (ffmpeg does the decoding; onset/tempo detection is plain Node).`node analyze.js ref.mp4` ,`POST /api/analyze` , or the`fablecut_analyze_reference` MCP tool. **Asset library** `library/` folders surface as tabs in the UI:**Elements**(overlay art),** Sound FX**,** SVG**— drop files in, the open editor refreshes live **Export** - Fast export: browser renders every frame + an offline audio mix, ffmpeg encodes a frame-accurate CRF-18 MP4 (keeps rendering if you switch tabs) - Realtime MediaRecorder fallback when ffmpeg isn't available ``` git clone https://github.com/ronak-create/FableCut.git cd FableCut node server.js # → http://localhost:7777 ``` Requirements: **Node 18+** and a Chromium-based browser. **ffmpeg on PATH** is optional but recommended (fast export + upload remuxing). AI background removal fetches its model from a CDN on first use. Drop media into the window (or `./media/` ), drag clips onto the timeline, edit, export. Everything an agent needs is in ** CLAUDE.md** — the complete schema, semantics and recipes. Point any capable model at that file and it can operate the editor end to end. Three equivalent control surfaces: - **MCP**(best for Claude Code / Claude Desktop) — register the bundled zero-dependency MCP server once: ``` claude mcp add -s user fablecut -- node "/fablecut/mcp-server.js" ``` Tools: `fablecut_status` (auto-starts the editor),`fablecut_docs` ,`fablecut_get_project` ,`fablecut_set_project` ,`fablecut_patch_project` ,`fablecut_import_media` ,`fablecut_analyze_reference` .The surface is **token-efficient by design**: agents patch the timeline with small ops (`fablecut_patch_project` ) instead of round-tripping the whole document, read a compact one-line-per-clip summary (`fablecut_get_project {compact:true}` ), and fetch only the manual sections they need (`fablecut_docs {section:"props"}` ). - **The file**— read`project.json` , modify, bump`revision` , write. The UI live-reloads. - **REST**—`GET/PUT /api/project` ,`POST /api/upload` ,`GET /api/library` , SSE at`/api/events` . See CLAUDE.md for the full list. Example: ask Claude Code *"cut these six clips to the beat markers, add a teal-orange grade, put a word-pop caption on top and a whoosh on every cut"* — and watch the timeline rebuild itself. Or hand it a reference: *"here's a reel I like — analyze it and remake it with my clips, same music"*. The agent calls `fablecut_analyze_reference` , gets the blueprint (cuts, beats, BPM, energy, drop, extracted music), and rebuilds the structure shot-for-shot with your footage. **Conflict-safe concurrent editing**: the UI, the MCP tools, and direct `project.json` writes all agree on a `revision` counter. If you edit a clip in the UI while an agent is mid-task, the agent's next write is rejected (409 from the REST API / a conflict error from `fablecut_set_project` ) instead of silently overwriting your change. The UI similarly detects when an agent write supersedes a not-yet-saved local tweak and tells you with a toast instead of dropping it silently. ``` server.js zero-dependency HTTP server: static hosting, REST API, SSE, ffmpeg export pipeline app.js the editor: timeline UI, compositor, keyframes, text engine, SVG rasterizer, chroma key, exporters index.html single-page UI style.css dark editor theme mcp-server.js stdio MCP server exposing the editor to AI agents analyze.js reference-video analyzer: shots, beats/BPM, energy, drop, music extraction (module + CLI) CLAUDE.md the agent manual (schema + recipes) — also served by fablecut_docs project.json your timeline (created on first run; gitignored) media/ project footage (gitignored) analysis/ cached edit blueprints from /api/analyze (gitignored) library/ default assets: elements/ sfx/ svg/ fonts/ exports/ finished renders (gitignored) ``` SVGs animate with plain CSS `@keyframes` . One convention: never hardcode `animation-delay` — set `--d: 0.4s` instead, and the compositor drives time by pausing all animations and rebasing their delays. Full rules + a skeleton in [CLAUDE.md](/ronak-create/FableCut/blob/main/CLAUDE.md#authoring-animated-svgs-the-svg-clip-kind); working examples in [ library/svg/](/ronak-create/FableCut/blob/main/library/svg). - The repo ships with **20 Google Fonts**(`library/fonts/` , OFL — see`LICENSES.md` there) and a set of self-authored SVG overlays and animated elements (`library/elements/` ,`library/svg/` , MIT like the rest of the repo). `library/sfx/` is yours to fill (gitignored): sound-effect sites typically don't allow redistributing their files in a public repo, so FableCut doesn't —`library/sfx/README.md` lists good free sources.- Export runs in the browser because the compositor *is*the browser; agents ask you to click Export (or render directly with ffmpeg from`media/` ).