Photon, a San Francisco-based AI infrastructure and developer tools startup, has raised $4.5 million in Seed funding to help developers build AI agents that work directly inside messaging apps.

The round was co-led by Gradient Ventures and A*, with participation from Vercel, HongShan, Z Fellows, Llama Ventures, and Karman.

Photon plans to use the funding to improve its platform, expand its developer tools ecosystem and grow its engineering team.

Founded by CEO Daniel Tian and Ryan Zhu, Photon develops Spectrum, a developer framework and API that allows companies to connect AI agents with messaging platforms such as iMessage, WhatsApp, Telegram, SMS/RCS, email and voice services.

The platform gives developers tools to build, deploy and monitor AI agents through a unified system. It also supports interactive features inside chat conversations, including booking menus, calendars and other mini-app experiences.

Photon started as an open-source project after its founders developed an iMessage bot and released the technology on GitHub. The company says the open-source version now accounts for 98% of platform usage, while more than 40,000 developers have signed up for its platform.

The company also says its platform has experienced rapid growth, with revenue increasing tenfold over four months and message volume rising fivefold in the past month.

Photon’s customers include Corgi Insurance, Boardy, Ditto and Rho. The platform also records more than 450,000 monthly npm downloads, according to the company.

Photon says the long-term goal is to make messaging platforms a place where users can interact with AI agents and complete tasks without having to switch between multiple standalone apps. The company is also exploring communication between AI agents, such as a travel assistant coordinating with separate agents to arrange flights and hotels.

The new funding will support Photon as it continues developing infrastructure for AI agents and expanding its developer community.