Skip to main content
Some work must not go through a generative model. A trim, a resize, a frame extraction, a caption overlay, or a format conversion must be exact and repeatable. For this, fal Agent runs Python in an isolated sandbox. You do not need to ask for code. Say what you want, and the agent decides whether a model or the sandbox is the right tool.

​
What is available

The sandbox is a Linux environment with Python and common media tools preinstalled:
  • Pillow and numpy for image work
  • ffmpeg and ImageMagick for video, audio, and batch image operations
  • matplotlib for charts
  • requests for fetching files
  • Hyperframes, a renderer that turns HTML and CSS compositions into MP4. The video-compositing skill governs its use
The agent can install additional Python and system packages inside the sandbox when a task needs them.

​
How results come back

Files the agent creates in the sandbox are uploaded to the fal CDN and appear in the chat as generation cells. The cell’s pill names the kind of work, such as video-edit, frame-extract, image-edit, or audio-edit. Sandbox outputs take an ordinal like any other output. You can pick them from the palette, and they are included in exports.

​
Video compositing

The video-compositing skill covers styled text and graphics over footage: captions and titles, lower thirds, animated logos, kinetic typography, montages, slideshows, and picture-in-picture layouts. The agent writes an HTML composition and renders it to MP4 with Hyperframes inside the sandbox. Pure generation, such as “a video of a dragon”, still goes to a video model, and a bare cut still goes to ffmpeg.

​
Photo editing

The photo-editing skill routes tonal, geometric, and compositing edits to the sandbox. Background removal, brightness and contrast, crop, straighten, and precise compositing are done in code. Edits that change what is in the image, such as “make it winter”, go to a generative edit model.

​
Limits

Each user gets their own sandbox. Sandboxes are not shared between accounts.

​
Privacy

Files enter the sandbox only when the agent downloads them for a task. Results are uploaded to your fal CDN space with the same retention as any other generation.