Kevin Gu

Kevin Gu
Occupation	Technology entrepreneur
Known for	Co-founder of Joindex (ThirdLayer)

Kevin Gu is a technology entrepreneur and co-founder of Joindex, operating under the company name ThirdLayer, an applied research and product lab building tools for human–AI collaboration. The company's first product, Dex, is a browser-based AI copilot designed to function as an "AI coworker" within Google Chrome. Joindex was part of the Y Combinator Winter 2025 batch.

Career

Gu co-founded ThirdLayer alongside Regina Lin. The company, founded in 2025 and based in the San Francisco Bay Area, describes itself as an applied research and product lab focused on the next interface for human–AI collaboration.

ThirdLayer's primary product is Dex, a Chrome extension that integrates AI assistance directly into the user's web browser. The company positions Dex as analogous to "Cursor for knowledge work" — a reference to the AI-powered code editor — but optimized for general knowledge work rather than software development. Dex is designed to operate across multiple browser tabs and web-based tools, including Salesforce, Google Sheets, Google Docs, Apollo, Notion, and Linear.

According to the company, most existing web agents are designed for discrete, "set-and-forget" tasks, whereas Dex aims to handle the more fluid nature of real work that spans multiple tools and evolving decisions. The product accepts input through voice, text, and user actions, and is intended to understand user intent contextually. Key technical goals for the platform include long-term cross-modal memory grounded in real workflows, a new interaction layer intended to replace static user interfaces with a collaborative canvas, and personalization systems that learn how individual users approach tasks and navigate software.

Dex was publicly launched in February 2025. The product is available as a Chrome extension through the Chrome Web Store under the name "Dex."

ThirdLayer participated in Y Combinator's Winter 2025 batch, where it was categorized under artificial intelligence, productivity, and consumer products. As of available records, specific fundraising amounts and company valuation have not been publicly disclosed.