The protocol your design agent hands off through
Your design agent talks to your coding agent through a connection neither of them built and neither of them owns anymore. That sentence would have been wrong fourteen months ago. It got true in two separate moves, eight months apart, and almost nobody outside infrastructure noticed either one.
Anthropic gave up owning the thing it invented
The Model Context Protocol is the plumbing that lets a Claude Design session pull your component library, or lets any agent call any external tool, in a standard way instead of a one-off integration per pair of tools. Anthropic built it. On December 9, 2025, Anthropic gave it away, donating MCP to a new, vendor-neutral Agentic AI Foundation under the Linux Foundation, alongside Block's and OpenAI's competing agent projects. Amazon, Google, Microsoft and OpenAI signed on as platinum members of the same foundation governing a protocol Anthropic used to fully control.
By the time of the donation, MCP already had over 97 million monthly SDK downloads and roughly 10,000 active servers. That is the actual reason the donation mattered: a plumbing standard that popular gets safer for everyone once no single company can unilaterally change it out from under the rest.
What changes when nobody owns the pipe
A proprietary integration can be changed by the company that owns it, on their schedule, for their reasons. A neutral standard has to change through a process every stakeholder agreed to, which is slower and less convenient for the original owner and considerably more trustworthy for everyone building on top of it.
That is the trade a foundation model company makes when it hands over its own protocol: it gives up the ability to move first for the ability to have every other agent vendor keep building against the same target instead of forking their own.
The protocol itself got rebuilt eight months later
On July 28, 2026, under that new governance, MCP shipped its most structural change yet: it dropped the session entirely. Earlier versions opened a handshake and held a connection while a client and server talked. The new spec makes every request self-contained, carrying its own protocol version and identity, and adds a way for a server to ask a user a mid-call question without keeping a connection open to wait for the answer.
That is not a cosmetic change. A stateless protocol is one that can be cached, routed through a gateway, and scaled the way the rest of the web already is. A session-based one can't.
| Before 2026-07-28 | From 2026-07-28 | |
|---|---|---|
| Connection model | Handshake, then a held-open session | Every request self-contained |
| Session identity | Mcp-Session-Id header | None; identity travels per request |
| Asking the user mid-call | Required holding the stream open | Server returns input_required and resumes |
| Routing | Gateway must parse JSON to route | Method and tool name in HTTP headers |
| Caching list results | Not specified | ttlMs and cacheScope on responses |
| Roots, Sampling, Logging | Supported | Deprecated, 12-month minimum sunset |
Why this is a workflow decision, not a footnote
If you're building or buying a design tool that connects to anything else through MCP, this changes what "supports MCP" actually promises: a server built against the old, session-based model does not automatically work against the new stateless one.
The five-minute action is checking, today, which spec version any MCP-connected tool in your stack claims to implement, and whether that claim was made before or after July 28, 2026. A tool that hasn't said which version it's on hasn't finished this migration yet, whatever its marketing page currently says.