Vercel's hosted MCP servers and the mcp-handler library now serve the stateless 2026-07-28 spec, no client-side changes required.
Vercel’s hosted MCP server and its mcp-handler
library now speak the Model Context Protocol’s biggest revision since launch: a rewrite that throws out persistent sessions in favor of stateless, self-contained requests (Vercel Changelog, Vercel MCP now supports the 2026-07-28 MCP specification). The spec landed July 28, 2026; Vercel shipped support within days, with mcp-handler@2.0.0
following on July 30 (Vercel Changelog, Latest MCP spec now supported in mcp-handler).
What changed #
The 2026-07-28 spec rips out MCP’s session model entirely: the initialize
/initialized
handshake and the Mcp-Session-Id
header are both gone. Every request is now a single, self-contained HTTP POST carrying its own protocol version, client identity and capabilities, so it can “land on any server instance behind a plain round-robin load balancer without needing shared storage” (Model Context Protocol Blog, The 2026-07-28 Specification, July 28, 2026). Roots, Sampling and Logging move out of the core spec into deprecated status, still working for at least 12 months, while Tasks graduates into a formal extension (io.modelcontextprotocol/tasks
) with a poll-based tasks/get
in place of server-initiated pushes.
Vercel’s hosted MCP server now serves both the new stateless protocol and the old 2025 one from a single endpoint, so existing clients built for the prior spec keep working unchanged while newer clients pick up statelessness automatically (Vercel Changelog). mcp-handler@2.0.0
, the library thousands of developers use to stand up MCP servers on Next.js, Nuxt and Svelte, adds native support for the same spec plus the MCP TypeScript SDK v2, while keeping a compatibility layer for 2025-era Streamable HTTP clients. The new major version requires Node.js 20+ and zod4, replaces @modelcontextprotocol/sdk
with @modelcontextprotocol/server
, and drops the deprecated HTTP+SSE transport outright: requests to /sse
and /message
now return 410 Gone
.
Not just Vercel #
The turnaround from spec publication to shipped support was fast because the design wasn’t Vercel’s alone. Engineers from Vercel, Cloudflare, Shopify and Amazon shaped the stateless direction over a public GitHub discussion the protocol’s co-creator opened in December 2024, with the maintainers formally committing to it at a transports meeting in December 2025 (VentureBeat, MCP just got its biggest update ever, July 2026). Cloudflare’s Agents SDK added support the same week, letting developers run MCP servers directly in Workers without transport-session overhead (Cloudflare Changelog, Cloudflare MCP servers support the new MCP 2026-07-28 Specification), and Amazon Bedrock AgentCore Gateway rolled out the same spec version to its customers days later (AWS Machine Learning Blog, How AgentCore Gateway supports the MCP 2026-07-28 spec).
Why it matters #
MCP’s original session model assumed an agent kept a live connection to one server instance, which is exactly the assumption serverless platforms are built to break. A stateful MCP server behind Vercel functions needed sticky routing or a shared session store just to survive a cold start or a second invocation landing on a different instance. Stateless requests remove that requirement: any function instance can answer any request, because the request carries everything the server needs to know.
Our take: the speed here is the story as much as the spec itself. A protocol revision that touches every MCP server in production usually takes a slow, painful migration; instead four infrastructure vendors had it live within a couple of weeks of publication, and Vercel kept both protocol versions on one endpoint so nobody’s existing client broke on launch day. That’s the tell that MCP is being treated as load-bearing infrastructure now, not an experimental add-on Vercel can afford to move slowly on.
Key Takeaways #
- The MCP 2026-07-28 spec removes protocol-level sessions (
initialize
handshake,Mcp-Session-Id
header) in favor of fully self-contained requests. - Vercel’s hosted MCP server and
mcp-handler@2.0.0
(July 30, 2026) both support the new spec while still serving 2025-era clients from the same endpoint. mcp-handler@2.0.0
requires Node.js 20+ and zod4, switches to MCP TypeScript SDK v2, and drops the deprecated HTTP+SSE transport.- Cloudflare’s Agents SDK and Amazon Bedrock AgentCore Gateway shipped support for the same spec within days, alongside Vercel.