We Built the Most Feature-complete iMessage Adapter for Vercel Chat SDK

TL;DR: Photon's iMessage adapter for Vercel's Chat SDK just got a major upgrade, now built on Spectrum. It's the most feature-complete iMessage integration in the Chat SDK ecosystem — tapbacks, message effects, mini-app cards, typing indicators, chat backgrounds, webhooks, and SMS/RCS fallback — backed by production infrastructure and free to start with unlimited daily messages.

About Photon

Photon builds cross-channel messaging infrastructure that puts AI agents where people already are — iMessage, WhatsApp, Telegram, and beyond. Spectrum is how we open that up to every developer.

If you are building an AI agent that talks to real people, at some point you will need it to reach them where they already are. Not in a browser tab. Not in a standalone app. In iMessage.

Sending an iMessage programmatically is not the hard part. The hard part is doing it reliably at scale — maintaining mac fleets, handling delivery edge cases, managing number reputation, falling back to SMS/RCS when iMessage is unavailable, and supporting the full depth of native iMessage features beyond plain text. Most iMessage APIs stop at "send and receive." Building one that is production-grade, feature-complete, and stable enough to run an always-on agent is a fundamentally different engineering problem.

We have spent the last year solving that problem. Today we are shipping a major upgrade to @photon-ai/chat-adapter-imessage, the iMessage adapter for Chat SDK. It is the most feature-complete iMessage adapter available for Chat SDK, and it is free to start.

What Chat SDK does and why adapters matter

Chat SDK is Vercel's TypeScript library for building bots that work across messaging platforms from a single codebase. You write your agent logic once — message handlers, streaming responses, state management — and adapters handle the platform-specific translation. Photon's iMessage adapter is one of the first platform adapters launched with Vercel's Chat SDK, alongside Slack, Discord, Teams, Telegram, WhatsApp, and others.

iMessage has always been the hardest platform to cover. Sending iMessages reliably from a server process is a genuinely difficult infrastructure problem — persistent connections, delivery guarantees, number management, and native feature support all have to be solved before the adapter layer even begins.

Our adapter is the most feature-rich and reliable iMessage adapter available for Chat SDK. It is built on Spectrum, Photon's open-source multi-channel agent framework — the same infrastructure that powers production iMessage agents for companies shipping today. Spectrum handles the hard parts — messaging streaming, message routing, delivery confirmation, SMS/RCS fallback — so the adapter can expose the full depth of native iMessage capabilities through a clean Chat SDK interface.

What changed in the upgrade

This release upgrades the adapter to Spectrum, our next-generation messaging infrastructure built for iMessage. The result is the most feature-complete and reliable iMessage integration available in the Chat SDK ecosystem.

Here is what the adapter now supports — no other Chat SDK iMessage adapter covers even half of this list:

| Capability | Status |
|---|---|
| Direct messages | ✅ |
| Cold-start DMs ( | ✅ |
| File uploads | ✅ |
| Tapback reactions (add/remove) | ✅ Remote |
| Message editing | ✅ Remote |
| Message unsend | ✅ Remote |
| Typing indicators | ✅ Remote |
| Mark read | ✅ Remote |
| Message effects (confetti, fireworks, lasers…) | ✅ Remote |
| Mini-app cards | ✅ Remote |
| Chat background customization | ✅ Remote |
| Polls via modals | ✅ Remote |
| Voice messages | ✅ Remote |
| Webhooks (Spectrum Cloud) | ✅ |
| SMS/RCS fallback | ✅ |

Most iMessage integrations stop at "send and receive text." This adapter gives your agent the full range of native iMessage behavior — effects, tapbacks, rich cards, typing indicators, chat wallpapers — the things that make an iMessage conversation feel like an iMessage conversation, not a stripped-down proxy. And it does it reliably, backed by infrastructure purpose-built for always-on iMessage delivery.

Two ways to run it

The adapter auto-detects its mode from environment variables:

Cloud (recommended)

Connect to Spectrum Cloud with a project ID and secret. Runs anywhere — Vercel, AWS, your laptop. No Mac required.

import { Chat } from "chat"; import { createiMessageAdapter } from "@photon-ai/chat-adapter-imessage"; const bot = new Chat({ userName: "mybot", adapters: { imessage: createiMessageAdapter({ local: false, projectId: process.env.IMESSAGE_PROJECT_ID, projectSecret: process.env.IMESSAGE_PROJECT_SECRET, }), }, }); bot.onNewMention(async (thread, message) => { await thread.post("Hello from iMessage!"); });

Local

Runs directly on a Mac, reading the local iMessage database and sending via on-device APIs. No external server, no credentials. Great for development.

const bot = new Chat({ userName: "mybot", adapters: { imessage: createiMessageAdapter({ local: true }), }, });

Webhooks: the serverless-native path

One of the biggest additions in this release is first-class webhook support. In cloud mode, Spectrum Cloud delivers inbound messages to your HTTPS endpoint as signed JSON — no long-lived connections, no cron jobs, no gateway processes to babysit.

// app/api/imessage/webhook/route.ts import { after } from "next/server"; import { bot } from "@/lib/bot"; export async function POST(request: Request): Promise<Response> { return bot.webhooks.imessage(request, { waitUntil: (task) => after(() => task), }); }
The adapter verifies the X-Spectrum-Signature HMAC on every delivery, rejects stale requests, and routes messages into your bot. Spectrum Cloud retries failed deliveries with backoff and delivers at-least-once. For serverless deployments on Vercel, this is the cleanest path — your agent wakes up on demand, processes the message, and goes back to sleep.

Even from a webhook delivery, your bot can still reply, react, edit, and show typing — the adapter rebuilds the thread from its chat GUID via spectrum-ts. This is the kind of deep iMessage integration that no other Chat SDK adapter provides.

Free to start, scales when you do

This is where the Spectrum integration changes the economics.

Photon's Free tier gives you:

Unlimited daily messages
Full direct messaging iMessage API access
RCS and SMS fallback
iOS 26 features (polls, background customization, and more)
Up to 10 users
Zero cost

If you are an individual developer building an agent, or a small team prototyping a product, you do not pay anything. You get the full feature set of the adapter, backed by production infrastructure, with no trial period and no credit card.

Pro ($25/mo) extends that to 100 users with fast-track support. Business ($250/line/mo) adds dedicated iMessage lines, group messaging API, cold outreach, and mini-app support. Enterprise brings custom SLAs, the lowest throttling, dedicated numbers you own, and what we believe is one of the most reliable iMessage API infrastructures in the world — purpose-built for agents that need to be always-on.

The pricing is flat and predictable. No per-message fees, no hidden platform charges, no sales call required to get started.

Get started

Sign up at app.photon.codes — takes 30 seconds
Set your IMESSAGE_PROJECT_IDandIMESSAGE_PROJECT_SECRET
Write your bot

Install it from npm. The full README and feature matrix are on GitHub, and the configuration reference is in the docs.

If you have been waiting for an iMessage adapter for Chat SDK that is actually feature-complete and production-ready, this is it.

Spectrum is open source. The adapter is MIT licensed. Start building at photon.codes.

FAQ

What is the Photon iMessage adapter for Chat SDK? It's an adapter that lets bots built on Vercel's Chat SDK send and receive on iMessage. Built on Spectrum, it's the most feature-complete iMessage integration in the Chat SDK ecosystem — you write your agent logic once and it handles the iMessage-specific translation.

Which iMessage features does it support? Direct messages, cold-start DMs, file uploads, tapback reactions, message editing and unsend, typing indicators, read receipts, message effects, mini-app cards, chat background customization, polls, voice messages, webhooks, and SMS/RCS fallback.

Do I need a Mac to run it? No. In Cloud mode the adapter connects to Spectrum Cloud and runs anywhere — Vercel, AWS, or your laptop. Local mode runs on a Mac against the local iMessage database and is handy for development.

How do webhooks work? In cloud mode, Spectrum Cloud delivers inbound messages to your HTTPS endpoint as signed JSON, verified with an X-Spectrum-Signature HMAC and delivered at-least-once with retries — the cleanest path for serverless deployments on Vercel.

Is it free? Yes to start. The Free tier includes unlimited daily messages, full direct-messaging iMessage API access, RCS/SMS fallback, iOS 26 features, and up to 10 users at zero cost. Pro is $25/mo, Business is $250/line/mo, and Enterprise adds custom SLAs and dedicated numbers.

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