Replit just shipped Agent 4, and the headline feature is not a new model , it is a fundamental rethink of how the platform works. Three things that used to be friction points have been rebuilt from scratch: how you design, how your team collaborates, and how planning and building relate to each other.

The old model was holding you back

Design Mode in Agent 3 was a separate tab in the editor. You'd switch into it, ask the Agent to create a design, iterate on it, and then convert it into an app when you were ready. It worked, but it had a real constraint: it was only compatible with web apps. If you were building anything else, Design Mode wasn't available to you.

Collaboration followed a fork-and-merge model. Each teammate copied the project into their own isolated environment, worked independently, and then had to manually resolve merge conflicts when bringing their changes back into the main branch. And planning was strictly sequential , you scoped out tasks, accepted a plan, and only then did the Agent start building.

Design Canvas: Figma inside your live app

Design Mode has been replaced by the Design Canvas , an infinite board that supports all artifact types, live previews, and direct manipulation tools. The key word is infinite: you are no longer confined to a tab or a single artifact type.

The canvas shows two types of content side by side: Artifact previews (interactive, running versions of your actual app that you can click through and interact with) and design mockups (lighter visual prototypes the Agent creates for fast exploration). The new design canvas is an infinite workspace where you can generate multiple design directions for any screen, compare them side by side, and fine-tune them with visual controls , all inside your live, working application. When you tweak a button color or nudge a layout on the canvas, it shows up immediately in the actual codebase. No handoff, no translation layer.