# MCP 2026-07-28 makes the protocol stateless: no handshake, no sessions, and every request carries its own version > MCP revision 2026-07-28 removes the initialize handshake and Mcp-Session-Id sessions, adds server/discover, subscriptions/listen and multi round-trip requests, and deprecates Roots, Sampling, Logging, HTTP+SSE and Dynamic Client Registration. ## Answer MCP revision **2026-07-28** makes the protocol stateless. The `initialize` handshake and the `Mcp-Session-Id` session are gone. Every request carries its protocol version and client capabilities in `_meta`, and every server must implement `server/discover`. Server-to-client requests are replaced by multi round-trip requests. This page describes the changes against **2025-11-25**, and it was checked against the specification's "latest" pages, which describe 2026-07-28. ## Details ### Major changes - **No handshake.** Requests carry `io.modelcontextprotocol/protocolVersion` and `io.modelcontextprotocol/clientCapabilities` in `_meta`. Clients SHOULD add `io.modelcontextprotocol/clientInfo`, and servers SHOULD add `io.modelcontextprotocol/serverInfo` to each result's `_meta`. An unsupported version returns `UnsupportedProtocolVersionError` (`-32022`). - **`server/discover`** returns `supportedVersions`, `capabilities` and optional `instructions`. Servers MUST implement it, and clients may skip it. - **No sessions, no GET stream, no resumability.** `Mcp-Session-Id` and `Last-Event-ID` are removed. Servers that need cross-call state hand out their own handles as ordinary tool arguments. - **`subscriptions/listen`** replaces the GET endpoint and `resources/subscribe`. The client opts in with `toolsListChanged`, `promptsListChanged`, `resourcesListChanged` or `resourceSubscriptions`. - **Removed:** `ping`, `logging/setLevel` and `notifications/roots/list_changed`. Log level is set per request with `io.modelcontextprotocol/logLevel` in `_meta`. - **Tasks** move to the official extension `io.modelcontextprotocol/tasks`. - **Multi round-trip requests** replace server-initiated requests. See [[mcp-multi-round-trip-requests]]. - **`resultType`** is required on every result: `"complete"` or `"input_required"`. Clients treat a missing value from an older server as `"complete"`. - **Caching:** `tools/list`, `prompts/list`, `resources/list`, `resources/read` and `resources/templates/list` results must carry `ttlMs` and `cacheScope` (`"public"` or `"private"`). - **HTTP headers:** every POST needs `Mcp-Method`. `tools/call`, `resources/read` and `prompts/get` also need `Mcp-Name`. A mismatch with the body gets `400` and error `-32020`. ### Deprecated, not removed Roots, Sampling and Logging (SEP-2577), the HTTP+SSE transport, the `includeContext` values `"thisServer"` and `"allServers"`, and Dynamic Client Registration (in favor of Client ID Metadata Documents). The registry lists the earliest removal for Roots, Sampling, Logging and Dynamic Client Registration as the first revision released on or after 2027-07-28. ### Migration checklist | Area | A 2025-11-25 implementation must | |---|---| | Server startup | Keep `initialize` only for legacy clients. Add `server/discover` | | Every request | Client: send `_meta` version and capabilities. Server: read them per request, never from stored state | | HTTP headers | Client: send `MCP-Protocol-Version`, `Mcp-Method`, `Mcp-Name`. Server: validate them against the body | | Sessions | Stop minting `Mcp-Session-Id`. Answer GET and DELETE with `405` | | Server requests | Replace `sampling/createMessage`, `elicitation/create` and `roots/list` with `InputRequiredResult` | | Notifications | Client: open `subscriptions/listen` instead of a GET stream | | Results | Add `resultType`. Add `ttlMs` and `cacheScope` to list and read results | | Removed methods | Stop calling `ping` and `logging/setLevel`. Move tasks to the extension | | Errors | Resource not found is now `-32602`, no longer `-32002` | ### Serving both eras A dual-era server chooses by how the client opens. A request with modern `_meta` is served statelessly. An `initialize` request selects legacy behavior, scoped to the stdio process or the HTTP session. Both may run on one endpoint. A dual-era client tries a modern request first. On HTTP it reads the body of a `400`: a recognized modern error means a modern server, and anything else means fall back to `initialize`. On stdio it probes with `server/discover`. It should cache the result per origin or process. A modern-only server should name its supported versions in the error it returns to `initialize`, because legacy clients cannot fall forward. ## See also - [[mcp-initialize-handshake]] - [[mcp-streamable-http-sessions]] - [[mcp-multi-round-trip-requests]] - [[mcp-connection-errors]] ## Sources - [MCP Specification 2026-07-28 — Key changes](https://modelcontextprotocol.io/specification/2026-07-28/changelog) - [MCP Specification 2026-07-28 — Versioning and Compatibility](https://modelcontextprotocol.io/specification/2026-07-28/basic/versioning) - [MCP Specification 2026-07-28 — Streamable HTTP](https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http) - [MCP Specification 2026-07-28 — Discovery](https://modelcontextprotocol.io/specification/2026-07-28/server/discover) - [MCP Specification 2026-07-28 — Subscriptions](https://modelcontextprotocol.io/specification/2026-07-28/basic/patterns/subscriptions) - [MCP Specification 2026-07-28 — Deprecated Features](https://modelcontextprotocol.io/specification/2026-07-28/deprecated) ## Sources - [MCP Specification 2026-07-28 — Key changes](https://modelcontextprotocol.io/specification/2026-07-28/changelog) - [MCP Specification 2026-07-28 — Versioning and Compatibility](https://modelcontextprotocol.io/specification/2026-07-28/basic/versioning) - [MCP Specification 2026-07-28 — Streamable HTTP](https://modelcontextprotocol.io/specification/2026-07-28/basic/transports/streamable-http) - [MCP Specification 2026-07-28 — Discovery](https://modelcontextprotocol.io/specification/2026-07-28/server/discover) - [MCP Specification 2026-07-28 — Subscriptions](https://modelcontextprotocol.io/specification/2026-07-28/basic/patterns/subscriptions) - [MCP Specification 2026-07-28 — Deprecated Features](https://modelcontextprotocol.io/specification/2026-07-28/deprecated)