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MCP Went Stateless: Migrating to the 2026-07-28 Spec (and Proving It Works)
TL;DR: MCP migrated to a stateless, era-based protocol in the 2026-07-28 spec, introducing legacy and modern eras and per-request self-contained envelopes. It adds new client/server packages, mandatory discovery and headers, and deprecates several features, framing the change as a dual-era protocol shift with security improvements.
The update moves from stateful sessions to stateless requests, split into legacy and modern eras. Each request carries capabilities in the envelope, supported by new client/server packages. Server discovery and required headers on HTTP POSTs become mandatory, while several features are deprecated on a one-year clock. A notable security concern is an unsigned requestState blob that could be exploited due to its travel pattern. The migration emphasizes a dual-era compatibility model and a stateless wire format for requests.
Question for the room: What has been your strategy for handling the two-era model in a gateway or gateway-less integration, and where did you encounter the biggest gotchas during migration?
— via dev.to
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