Ably vs Resend
Side-by-side trajectory, velocity, and editorial themes.
Ably is spinning up an AI-agent transport layer at 0.x speed
Ably is iterating hard on a new AI Transport SDK — four releases (0.2 through 0.5) in about a month — aimed at making agent conversations durable, resumable, and branchable over its realtime channels. Alongside it, the core Pub/Sub and Chat SDKs keep getting steady, mostly incremental maintenance: React hook ergonomics, presence reliability fixes, and better LiveObjects visibility in the dashboard.
The AI Transport line is the story. Each release layers on capability that matters for production agents — declarative codecs, external data hydration, and now durable execution that survives process restarts inside frameworks like Temporal and Vercel's WDK. Ably is positioning its realtime infrastructure as the transport substrate for AI agents, not just chat and pub/sub, while keeping the mature core SDKs stable. The frequent breaking changes signal a product still finding its API shape.
Expect the AI Transport SDK to keep its fast breaking-change cadence toward a 1.0 with a stabilized session/run API, and likely SDKs beyond JS as the surface settles. The entries don't yet indicate a GA date.
Resend goes agent-native with a hosted, OAuth-backed MCP server for email.
Resend is a developer-first email API that has spent the last quarter widening on two fronts. It is building an agent-native surface — an official Claude Code plugin, mentions in AI chats, and now a hosted MCP server — while also creeping past transactional email into audience tooling with CSV contact import, in-email charts, and richer editor previews. The core remains a clean API for sending mail.
The direction is Resend-as-infrastructure that both humans and agents call directly. The MCP thread — a plugin in May, a hosted server in July — turns email into a tool an LLM can invoke over OAuth rather than hand-rolled keys, while the contacts and broadcast work points at competing with marketing-email incumbents, not just transactional senders. Distribution is shifting toward embedding where developers already are, via Vercel's marketplace and Auth0.
Expect the MCP surface to grow from sending into contact and analytics operations, and the audience and broadcast side to keep maturing toward a full marketing-email offering.
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