proving-it-works

A Claude Code plugin for making a movie that proves software actually works — and for catching the defects that make such movies worthless before you hand one to anybody.

See it work

imagethe movie the plugin made, playing inside the demo

▶ Watch the full two minutes, with sound · subtitles · how it was made

A clean container installs this plugin from the public marketplace, an agent inside it uses the skill to make a narrated movie of a small web app, and the skill's own checker verifies that movie. The loop above is that inner movie playing: real screenshots, a cursor you can watch, a local voice (there is no API key in that container), and subtitles burned into the picture.

Why

A movie is evidence, and every way it fails is silent. No crash, no red text: just an artifact that looks fine to whoever made it and is obviously broken to the first person who watches it.

This plugin exists because of a measured failure. Two agents were asked to record a narrated movie proving a small web app worked. One of them extracted frames and looked at them, ran ffprobe, checked the audio wasn't silent, asserted real DOM state at every step, and confirmed via the server log that a page reload had genuinely round-tripped. Every check passed. It shipped a movie whose picture froze three seconds in while the narration kept talking for another twenty.

Per-frame verification cannot see a defect that lives between frames. So the timeline check here is a script, not advice.

What's in it

A skill, proving-it-works-with-a-movie, that covers four routes:

...plus the parts that go wrong regardless of route: narration verbatim gates, measured (never guessed) pacing, cursor visibility, ffmpeg traps, and recording against a copy of your data rather than the real thing.

The scripts

check-movie

The mechanical gate. It samples picture and sound on one timeline and fails a movie when the action is crammed into the opening seconds while narration continues over a frozen picture, when the picture never changes at all, or when the audio is silent. It writes a contact sheet you are then expected to actually look at.

$ skills/proving-it-works-with-a-movie/scripts/check-movie demo.mp4
container  h264 1280x800, 26.8s, audio=yes
picture    reaches a new state in 2 of 26 seconds; last at 3s
sound      audible in 24 of 24 seconds; last at 23s
sheet      demo-check/contact-sheet.png
FAIL       every visible change happens in the first 3s (12% of runtime),
           then the picture is frozen for 23s while narration keeps talking
           for 20s of it. The demo is over before the explanation starts:
           pace the action to the narration.

NOT SHIPPABLE. Fix, regenerate, re-run.

It cannot tell you a movie is right — only that it isn't obviously broken. That is what the contact sheet and your own eyes are for.

Install

/plugin marketplace add prime-radiant-inc/proving-it-works
/plugin install proving-it-works

The skill then activates on its own when you ask for a demo, screencast, tutorial, or proof video.

It runs on every harness below; each one reads the same skill from skills/.

Requirements

• ffmpeg and ffprobe
• uv (runs check-movie; it declares its own dependencies inline)
• For the browser routes: Chrome plus a driver (Playwright or raw CDP)
• For narration: any TTS you like — see the skill's narrating.md for which kinds lie to you and how to catch them

Tests

tests/test-check-movie.sh

Synthesizes movies with known defects via ffmpeg's lavfi sources and asserts the checker's verdict on each. No fixtures committed, nothing downloaded.

Credits

The composited-stills and log-rendered-reel routes are adapted from rendering-a-demo-movie.md and recording-a-proof-movie.md in obra/superpowers PR #1931 (MIT). The rest comes from producing a real narrated product tutorial and from the baseline experiments described above.

License

MIT — see LICENSE.