ThirdLayer

ThirdLayer is an applied research and product lab building the next interface for human–AI collaboration.

Our first product is Dex, an AI copilot for the browser. Think Cursor for knowledge work, optimized for speed and embedded directly where you work.

Most web agents are built for set-and-forget tasks. But real work is fluid and messy:spread across tabs, tools, and evolving decisions. Dex transforms your browser into an intelligent, multimodal workspace that understands your intent through voice, text, and action. It enhances familiar interfaces, automates tedious steps, and removes the friction of handoffs.

Beneath the surface, Dex is more than a browser agent : it’s a foundation for:

● Long-term, cross-modal memory grounded in real workflows

● A new interaction layer to replace static UI with a collaborative canvas

● Personalization: understanding how individuals approach tasks and navigate software

We're building the infrastructure for adaptive, intent-aware systems that work the way you do.

High-Level Overview

ThirdLayer is an applied research and product lab founded in 2025 that builds Dex, an AI browser copilot designed to transform the web browser into an intelligent, context-aware workspace. Dex serves knowledge workers such as founders, operators, researchers, and students who juggle multiple tools and browser tabs, helping them reduce context-switching and enhance productivity by embedding AI directly into their workflows. The product solves the problem of fragmented work environments where switching between apps and tabs breaks focus and slows down progress, by providing a seamless AI layer that understands user intent and remembers preferences to proactively assist in tasks[1][2][5].

As a portfolio company, ThirdLayer is backed by Y Combinator and leading investors in deep tech, focusing on AI, human-computer interaction (HCI), and productivity enhancement. Its impact on the startup ecosystem lies in pioneering AI-native workspaces that blend research and product design, pushing the boundaries of how AI can augment human cognition and workflow efficiency[2].

Origin Story

ThirdLayer was founded in 2025 by Kevin Gu and Regina Lin in San Francisco, CA. Both founders bring strong backgrounds in AI and product innovation, with the team having experience and connections to top quant trading firms, frontier research labs, and academic institutions such as MIT Media Lab, Stanford SAIL, and Berkeley BAIR. The idea for ThirdLayer emerged from recognizing the limitations of current AI interfaces, which are often siloed in static UIs and prompt boxes, failing to integrate smoothly into real-world workflows. Early traction includes acceptance into Y Combinator Winter 2025 batch and building a small but focused team to develop Dex, which has quickly gained attention for its novel approach to AI-assisted browsing[1][2][4].

Core Differentiators

• Product Differentiators: Dex is not just an AI assistant but a *context engine* that orchestrates multiple AI agents, maintains a living memory of workflows, and predicts user intent to deliver personalized, adaptive assistance within the browser environment[2].
• Developer Experience: Designed for seamless integration, Dex enhances existing tools rather than replacing them, minimizing friction and learning curves for users.
• Speed and Ease of Use: By embedding directly into the browser and automating context switches, Dex accelerates workflows and reduces cognitive load.
• Community Ecosystem: ThirdLayer collaborates with top research and design advisors from leading AI and HCI institutions, fostering innovation and credibility in the AI tools space[2].

Role in the Broader Tech Landscape

ThirdLayer rides the wave of AI augmentation and human-computer interaction evolution, addressing a critical bottleneck in productivity: the fragmented digital workspace. As AI models advance rapidly, the timing is ideal for rethinking interfaces to move beyond static prompts toward dynamic, context-aware systems that integrate deeply into everyday tools. Market forces such as the rise of remote work, increasing complexity of digital workflows, and demand for productivity tools favor ThirdLayer’s approach. By pioneering multiagent orchestration and intent-aware AI within browsers, ThirdLayer influences the broader ecosystem by setting new standards for AI-native work environments and workflow automation[2][3].

Quick Take & Future Outlook

Looking ahead, ThirdLayer is poised to expand Dex’s capabilities, likely incorporating more sophisticated multiagent coordination and deeper integrations with popular productivity tools. Trends such as increasing AI adoption in knowledge work, demand for seamless workflow automation, and advances in long-term context memory will shape their journey. Their influence may evolve from a niche AI tool to a foundational platform for AI-augmented work, potentially redefining how digital workspaces operate. This aligns with their mission to augment human cognition by embedding AI as an extension of the mind, making Dex an indispensable copilot for the future of work[2].

In summary, ThirdLayer’s Dex addresses a critical gap in AI usability by transforming browsers into intelligent, proactive workspaces, positioning the company at the forefront of AI-driven productivity innovation.