- Photon has raised $4.5M in seed funding co-led by Gradient and A*.
- Its Spectrum SDK connects AI agents to iMessage, RCS, SMS, WhatsApp and more.
- Photon says revenue grew 10x from May to August, with 50 paying customers.
A friend of Photon’s founders could not tell their AI agent from a person in his own iMessage thread. That moment, the founders say, showed them where agents belong.
Now the San Francisco startup, which connects agents to iMessage, RCS, SMS, WhatsApp and other channels, has raised $4.5 million in seed funding co-led by Gradient and A*.
Vercel, HongShan, Z Fellows, Llama Ventures, Karman and angel investors also joined. Photon will use the money to scale iMessage business messaging for regulated industries, continue developing its Spectrum SDK, and onboard design partners. It did not disclose a valuation or its total funding to date.
Photon, a San Francisco-based messaging infrastructure startup, has raised $4.5 million in seed funding to make it easier for developers to deploy AI agents directly into the messaging channels where users already communicate.
The company was founded by Daniel Tian, co-founder and CEO, and Ryan Zhu. Tian says the problem is simple to state.
“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,” said Tian.
Why iMessage is the hard part
Shipping an AI agent still means asking someone to install and open an app. Messaging is where people already are, but it is the hardest place to reach. Apple has no public iMessage API for general agent use. Its Messages for Business product covers approved business conversations. Meta went further on WhatsApp, updating its Business API terms to bar general-purpose AI chatbots from January 15, 2026, while task-specific business bots stayed allowed.
Photon says the platforms that do offer an API have been narrowing it. Developers end up maintaining fragile per-channel plumbing, or they build for one channel and stop.
Photon’s answer is one integration. The Spectrum SDK gives developers a single interface across iMessage, RCS, SMS, WhatsApp and other channels, so an agent written once reaches users wherever they text. Ditto shows the pattern. Students text a number, and Photon’s blog says each gets one planned date a week.
In June, Photon shipped what it calls the first mini-app API on iMessage. Agents can send buttons, forms, and live interfaces that render within the thread, so users can complete a task without leaving the conversation. Photon’s website says mini apps need iOS 26.
Customers, partners and overlapping backers
Photon says it powers the chat experience for more than 1 million end users in under a year. It has 50 paying customers with churn under 3%, and message volume grew fivefold in September. Revenue grew 10x between May and August, but Photon did not disclose revenue, so that figure has no base to measure against.
Photon is the official iMessage adapter for Vercel’s Chat SDK and the default iMessage layer for Nous Research’s Hermes Agent, with further integrations across Mastra, Convex, Render and Telnyx. The company says it is SOC 2 Type II certified and HIPAA-compliant, which matters for the regulated industries it targets.
The investors bring AI and consumer-scale credentials. Gradient, the AI seed fund that started inside Google in 2017, has backed Lambda, Oura and Writer. A*, co-founded by Eventbrite co-founder Kevin Hartz, closed a $450 million third fund in May and has backed Ramp and Mercor. HongShan was formerly Sequoia China.
“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,” said Vig Sachidananda, partner at Gradient.
Rivals, and a channel Photon does not own
Linq announced a $20 million Series A led by TQ Ventures on February 2, 2026, and sells a similar layer for iMessage, RCS and SMS. It said AI agents on its platform reached 134,000 monthly active users and more than 30 million messages a month. Demand for the channel took off with assistants such as Poke, the iMessage-native assistant that launched with a $15 million seed round.
Bigger incumbents are moving too. Bird, which serves Meta, PayPal and Klarna, secured $450 million in debt in September and unveiled an agent toolkit. On WhatsApp, Wassist raised $1.1 million and Jelou raised $10 million.
Every company here builds on a channel it does not own. The WhatsApp rule change shows how fast a platform can rewrite its terms. Photon’s announcement does not say how it would respond if Apple or Meta tightened access, or how its revenue splits across channels.
A million end users in under a year gives Photon a head start. The harder question is the one TFN raised over Bird’s agent push: does the agent economy need its own messaging layer, or will Apple, Meta and the model providers absorb it?
