Substrate

Substrate now builds Zo Computer, a personal cloud computer that combines an AI agent with files, a database and hosted services. Consumers and small-business operators use it to build websites, conduct research and organize finances. Users can generate media, transcribe audio and schedule automations, while connecting AI subscriptions or supplying their own model-provider API keys. Its scope extends beyond conversation: users can host applications and work directly in their computing environment.

Cofounders Rob Cheung, Zo’s CEO and a former founding engineer at Substack, and Ben Guo, the founding engineer of Stripe Terminal, originally built Substrate for developers composing AI workflows. Its SDK represented discrete tasks as computation-graph nodes; the backend used those graphs to optimize execution through colocation, graph rewriting and parallelism. The original platform was shut down before the team developed Zo Computer, which began launching in 2025. In August 2026, Guo announced he was closing his chapter at Zo.

Lightspeed led Substrate’s $8 million seed round in 2024. At that time, the investor named Substack and Maven as customers and reported throughput of billions of tokens per month across computation graphs. By April 2026, Zo was an eight-person company.