Launch HN: Mosaic (YC W25) – Agentic Video Editing (mosaic.so)

We were engineers at Tesla and one day had a fun idea to make a YouTube video of Cybertrucks in Palo Alto. We recorded hours of cars driving by, but got stuck on how to scrub through all this raw footage to edit it down to just the Cybertrucks.

We got frustrated trying to accomplish simple tasks in video editors like DaVinci Resolve and Adobe Premiere Pro. Features are hidden behind menus, buttons, and icons, and we often found ourselves Googling or asking ChatGPT how to do certain edits.

We thought that surely now, with multimodal AI, we could accelerate this process. Better yet, an AI video editor could automatically apply edits based off what it sees and hears in your video. The idea quickly snowballed and we began our side quest to build “Cursor for Video Editing”.

We put together a prototype and to our amazement, it was able to analyze and add text overlays based on what it saw or heard in the video. We could now automate our Cybertruck counting with a single chat prompt. That prototype is shown here: https://www.youtube.com/watch?v=GXr7q7Dl9X0.

After that, we spent a chunk of time building our own timeline-based video editor and making our multimodal copilot powerful and stateful. In natural language, we could now ask chat to help with AI asset generation, enhancements, searching through assets, and automatically applying edits like dynamic text overlays. That version is shown here: https://youtu.be/X4ki-QEwN40.

After talking to users though, we realized that the chat UX has limitations for video: (1) the longer the video, the more time it takes to process. Users have to wait too long between chat responses. (2) Users have set workflows that they use across video projects. Especially for people who have to produce a lot of content, the chat interface is a bottleneck rather than an accelerant.

That took us back to first principles to rethink what a “non-linear editor” really means. The result: a node-based canvas which enables you to create and run your own multimodal video editing agents. https://screen.studio/share/SP7DItVD.

Each tile in the canvas represents a video editing operation and is configurable, so you still have creative control. You can also branch and run edits in parallel, creating multiple variants from the same raw footage to A/B test different prompts, models, and workflows. In the canvas, you can see inline how your content evolves as the agent goes through each step.

The idea is that canvas will run your video editing on autopilot, and get you 80-90% of the way there. Then you can adjust and modify it in an inline timeline editor. We support exporting your timeline state out to traditional editing tools like DaVinci Resolve, Adobe Premiere Pro, and Final Cut Pro.

We’ve also used multimodal AI to build in visual understanding and intelligence. This gives our system a deep understanding of video concepts, emotions, actions, spoken word, light levels, shot types.

We’re doing a ton of additional processing in our pipeline, such as saliency analysis, audio analysis, and determining objects of significance—all to help guide the best edit. These are things that we as human editors internalize so deeply we may not think twice about it, but reverse...