How Bolt Generates On-Brand Prototypes in 5 Minutes with Claude Agent SDK

Bolt by StackBlitz is a vibe coding tool that lets users build full applications in natural language. Its newest capability is a design system agent that allows PMs and designers to generate production-ready, on-brand prototypes without writing code—closing the gap between prototype and production that has kept non-engineers on the sidelines of the development lifecycle.

Most companies don't have their design system in one place. Typography lives in a Google Doc. Components are scattered across Figma files, Storybook instances, and GitHub repositories. Spacing guidelines might be in a wiki, or just in an engineer's head. The result: Bolt could generate code quickly, but without the company's actual design language, the output looked generic. Prototypes became throwaways—a PM builds something to communicate an idea, an engineer rewrites it entirely before it can ship. "Oftentimes if you just use Bolt, it doesn't have any idea about your company's design system," said Dominic Elm, Founding Engineer at StackBlitz.

StackBlitz had built its own internal agent but chose to rebuild on the Claude Agent SDK when it launched. The team is small, and the SDK meant they could inherit the full capability set that powers Claude Code without matching that investment. The design system agent ingests everything a company has—Storybook sites, GitHub repos, npm packages, Figma tokens, documentation files—and runs a thorough pass across each source, resolving conflicts, mapping design tokens, and building a consolidated intermediate representation of the full design system. Claude Opus 4.7 powers this research phase, chosen because it "showed the best results overall" for the sustained reasoning the work demands. The SDK's stop hook keeps the agent running across a long workflow and allows mid-run course corrections. Custom sub-agents handle parallel tasks while keeping the main context window clean.

The design system generation averages 53 minutes. Once it completes, the result lives inside Bolt as a browsable library of the company's components, sections, and pages. From that point on, any team member can prompt Bolt to build something—a car configurator, a comparison page, a landing variant—and the output follows the company's actual components, typography, and spacing. The agent then runs a review loop to check its own work against the design system before delivery. The result is a prototype that can go to production with minimal engineer rework. More than 10,000 users have already uploaded their own design systems to Bolt, and StackBlitz sees roughly 90% cache efficiency across these long-running workflows, keeping inference costs manageable.

"The goal is to get PMs and designers actually integrated into the development lifecycle and able to contribute to production code," said Elm. "That's the holy grail for almost everyone." StackBlitz deliberately designed Bolt not to be the source of truth for a company's design system—when teams update their design system, they reindex in Bolt and the agent does an incremental update, ensuring the output always reflects the latest standards.