MCP Changelog Tracker: Spec Versions, SDKs and Registry Status

This page tracks the Model Context Protocol (MCP) for engineers who run MCP servers: every specification revision from the first to the current one, the latest release of each official SDK in the modelcontextprotocol GitHub organisation, the state of the official registry, and the security advisories worth patching for. I update it whenever a release, advisory or status change lands, and every row links to the primary page I read. All dates are UTC. Last checked: 12 November 2026.

Latest changes

• 12 Nov 2026: MCP Inspector 2.15.0 shipped with four security fixes. The deprecated v1 line got its own security release, 1.0.5, on 11 Nov (source, 1.0.5). If you pinned the 2.13.0 from my Inspector debugging guide, move up.
• 11 Nov 2026: The maintainers moved the specification to a six-month release cycle, generally the last Tuesday of March and September, and set 30 March 2027 as the target for the next revision, 2027-03-30 (source).
• 11 Nov 2026: Reference servers v2.4.0 fixed six vulnerabilities across the filesystem, git and fetch servers (source).
• 10 Nov 2026: PHP SDK v0.10.0 split the code into Mcp\Schema, Mcp\Client and Mcp\Server namespaces, a breaking change for most imports, and now requires PHP 8.2 (source).
• 10 Nov 2026: The File Uploads Working Group published a draft io.modelcontextprotocol/files extension for revision 2026-07-28 and later. It is experimental and has no reference implementation yet (source).
• 7 Nov 2026: C# SDK v2.4.0 added experimental support for the Skills extension (source).
• 3 Nov 2026: C# SDK v2.3.1 and v1.4.2 patched a session hijacking flaw in the ASP.NET Core transport (source).
• 30 Oct 2026: The Ruby SDK was announced as Tier 1, joining TypeScript, Python, C#, Go and Rust (source).
• 23 Oct 2026: TypeScript SDK v2.4.0 added Skills over MCP (SEP-2640), with 1.32.2 for the 1.x line the same day (source).
• 21 Oct 2026: Inspector 1.0.3 fixed two critical advisories that let a malicious remote server run local commands (source). The pattern is the one I described in MCP Security in 2026: the tooling around the protocol is where the holes are.

MCP specification revisions

Revisions are named by date. The versioning page names 2026-07-28 as Current and defines past, complete revisions as Final, which is how I label the older rows. The GitHub release for each revision from 2025-03-26 onwards was published on the date in its name. For what the stateless rewrite means in practice, see Remote vs Local MCP Servers in 2026.

Official SDK versions

Latest stable release tag per SDK, read from GitHub releases on 12 November 2026. Tiers come from the SDKs page: Tier 1 commits to full feature support and a 100 percent conformance pass rate, Tier 3 is experimental, and the full requirements are on the SDK tiers page. The same page warns that SDKs adopt new revisions on their own schedules, so check the SDK's documentation before assuming 2026-07-28 support.

Registry, governance and client status

The registry count is my own: I paged the public API to the end and counted entries, so it is a measurement on the day, not an official figure.

# follow metadata.nextCursor until it is absent, counting servers[]
curl -s "https://registry.modelcontextprotocol.io/v0/servers?version=latest&limit=100"

Notable MCP security advisories

A selection, newest first: the critical ones, plus the high-severity SDK advisories that change what a server operator has to patch. Severity is the score given in the linked advisory. For incidents beyond MCP, the AI Agent Security Incident Log is the wider list.

How this page is maintained

Every row comes from a primary source I fetched on the "Last checked" date: the specification and changelog pages on modelcontextprotocol.io, GitHub releases and security advisories in the modelcontextprotocol organisation, the registry's own API, and NVD or vendor advisories for third-party software. I deliberately leave out pre-releases, third-party SDKs and frameworks, unofficial server directories, download counts, vendor marketing claims, and the low and medium severity advisories, of which the official repositories have published more than 30 since September 2026. Anything I could not confirm against a primary source is not on the page. Corrections and missing rows go to hello@ajayk.sh.

FAQ

What is the latest version of the MCP specification?

The current revision is 2026-07-28, released on 28 July 2026. It removed the initialize handshake and protocol-level sessions, so every request carries its own protocol version and capabilities. The next revision is targeted for 30 March 2027 under the new six-month release cycle.

Which MCP SDK versions support the 2026-07-28 spec?

The 2026-07-28 release post says the TypeScript, Python, Go and C# SDKs were updated on release day, and the Ruby SDK has supported it since 1.2.0. For the other SDKs, check each project's documentation, because SDKs adopt revisions on their own schedules and only Tier 1 SDKs commit to supporting a new revision by its release date.

Is the official MCP Registry generally available?

No. It launched in preview on 8 September 2025 and its documentation still carries the preview notice, with a warning that breaking changes or data resets may occur before general availability. It is not small, though: I counted 62,783 server entries through its API on 12 November 2026. The registry verifies who owns a namespace, not whether a server is safe, so treat an entry as an address and not as an endorsement.

Related: What Is MCP (Model Context Protocol)? A Plain-English Guide for 2026, MCP Security in 2026: The Protocol Got Hardened. The Ecosystem Didn't. and MCP Authorization Explained: OAuth 2.1, RFC 9728 and CIMD in 2026.