onecentdemo
jev-demofast drives your real product in a browser, outlines every element it uses, and renders the MP4. NVIDIA Nemotron on Nebius Token Factory writes the founder's script; Jev, a fast decision model, makes each click in about a quarter of a second.
A replay of real runs, at the timing they had. The log lines, Jev's answers, every frame and the video
come from each run's replay.json; the camera follows the outline the recorder drew. Added for this page: the typing
and the background music. The narration step is shown at 4× speed with its clock still counting real
seconds. The voice-over in each finished video was written and spoken by the tool.
It browses your site once like a visitor: pages, menus, listings and filters. Pages behind a login are noted, never forced. Point it at your repo and it reads every route from source instead.
NVIDIA Nemotron 3 Ultra on Nebius Token Factory reads your brief and what the site says, writes the voice-over a founder would give, and picks the screens that make the point.
On each screen Jev answers one question: is the goal done, is its form here, or is it somewhere else? It acts only when it is at least 50% sure, and never signs up, logs out or deletes.
Smooth, outlined frames, typed values blurred if you like, and the script spoken in one take over an MP4 you can download.
The whole tool is open source. Bring your own keys (Nebius Token Factory for Nemotron, Cloudflare for Jev); a demo costs cents to make.
Prefer we handle it? Send your product and the flows you want shown. We deliver narrated demo videos on your staging site, and re-record them when your product changes. Voice, pace and music to fit your brand; nothing touches production.
Hosted · $3 free
One sentence and your site's address in; a narrated demo out in about two minutes. Watch it map the site, write the founder's script, record and narrate, all in your browser. Add your GitHub repo and the script speaks in your README's words.
Four steps, about five minutes. Everything runs on your machine; only the model calls go out, to Nebius Token Factory and Cloudflare.
git clone https://github.com/q3learners/jev-demofast cd jev-demofast && uv sync export CLOUDFLARE_ACCOUNT_ID=... CLOUDFLARE_API_TOKEN=... export JDF_LLM_PROVIDER=nebius NEBIUS_API_KEY=...
A separate Chrome profile, so your own browser and logins stay untouched. Add --open with your
login page to sign in once; the profile remembers it.
uv run jev-demofast chrome
Nemotron writes the script and sketches the route once; Jev picks every click on the live page.
uv run jev-demofast demo "Show founders how OneCentDemo turns one sentence into a demo" \
--url https://onecentdemo.com/ --voice chris --out ours.mp4Map your app from its source in about a second, then Jev drives from the map with no route plan.
Passwords stay a {{PASSWORD}} placeholder and are typed straight into the field.
uv run jev-demofast index ../my-app --out app-index.json
DEMO_PASSWORD=... uv run jev-demofast demo \
"Sign in as test@example.com with password {{PASSWORD}}, then invite jane@example.com" \
--url http://localhost:3000/sign-in --index app-index.json --out invite.mp4Add any of these to the demo command:
--voice thalia--voice-speed 1.2--music track.mp3--dry-run