Photon raised $4.5 million in a seed round to expand its messaging infrastructure platform for AI agents across iMessage, RCS, SMS and WhatsApp. The round was co-led by Gradient and A*, with participation from Vercel, HongShan, Z Fellows, Llama Ventures, Karman and angel investors. Photon said it has powered chat experiences for more than 1 million end users in under a year.
Revenue and message volume have climbed sharply: Photon reported a 10x increase in revenue between May and August, and message volume grew fivefold in the most recent month.
Photon’s product and SDK
Photon said it will use the funding to scale iMessage business messaging for regulated industries, launch its Spectrum SDK and onboard additional design partners. The company positions the Spectrum SDK as a single developer interface across iMessage, RCS, SMS, WhatsApp and other channels, addressing the fragmentation that forces developers to maintain separate integrations for each platform — a problem made worse by the lack of an official third-party iMessage API and shifting access requirements on other services.
In June, Photon launched what it described as the first mini-app API on iMessage, allowing developers to move beyond plain-text conversations and add buttons, forms and live interfaces directly inside message threads.
“We started Photon because a friend could not tell our agent from a person in his own iMessage thread, and that told us where agents actually belong. Every team building an agent hits the same wall, which is that the audience is in messaging and messaging is closed. We built the layer that opens it, and the developers arriving without us asking are the signal that this was the missing piece.”
Daniel Tian, Co-Founder and CEO of Photon
Adoption, integrations and compliance
Photon currently serves 50 paying customers and reported churn below 3%. One customer, Ditto, has more than 140,000 active users and has sent more than 4 million messages through Photon. The company said it has expanded integrations across the developer ecosystem: it is the official iMessage adapter for Vercel’s Chat SDK and the default iMessage layer for Nous Research’s Hermes Agent, and it integrates with Mastra, Convex, Render and Telnyx.
Photon is SOC 2 Type II certified and HIPAA compliant. The company was founded by Daniel Tian and Ryan Zhu and is headquartered in San Francisco.
“Photon is bringing AI capabilities to channels which have already onboarded more than a billion users, like iMessage and RCS. These channels offer consumers a far richer experience than traditional AI interfaces and developers the opportunity to meet their users where they already are. We are very excited about what Photon enables and the journey ahead.”
Vig Sachidananda, Partner at Gradient
