Mosaic AI raises $75M Series B to ship 'Muse' design co-pilot for UX teams

AI · 5 min read

Mosaic AI closed a $75 million Series B led by Index Ventures with participation from Sequoia and existing backers. The startup says the new capital will accelerate development of Muse, a context-aware design assistant that plugs into Figma, Sketch and popular prototyping tools.

Muse can generate high-fidelity UI variations, produce copy snippets aligned with brand voice, and suggest accessibility improvements based on live prototypes. Mosaic claims Muse uses a hybrid approach — a fine-tuned LLM for language and a diffusion-guided model for pixel-level UI suggestions — and keeps customer assets on private instances to meet enterprise security requirements.

The company emphasized collaboration: Muse includes version-aware suggestions, team-wide style enforcement, and an audit trail for AI-generated changes. Mosaic also announced a beta of an API that lets product managers feed user-research transcripts to Muse so it can prioritize design changes around real user pain points.