First V2 Alpha Release

This is the first alpha of v2 of the MCP Python SDK.

Publishing this alpha changes nothing for existing users. Installers don't pick up pre-releases unless you explicitly opt in, so if you do nothing you stay on v1.x.

Why v2

The upcoming MCP spec release (2026-07-28) has significant protocol changes, including moving from a stateful, bidirectional protocol to stateless request/response. The v1 SDK is built around long-lived sessions, so supporting the new spec means replacing the SDK's core. Since that's breaking anyway, v2 also fixes some long-standing API problems.

What's in this alpha

• A new Dispatcher pipeline replaces ServerSession on the server side (ServerSession remains as a thin proxy). The same change is coming to ClientSession, which will most likely stay as a shim.
• The low level Server interface has changed quite a bit: handlers are now constructor parameters instead of decorators, and return values are no longer auto-wrapped.
• Server middleware, partially added.
• Type changes throughout, including snake_case field names and stricter validation.
• FastMCP is renamed to MCPServer.

The full list is in the migration guide, which is currently the most complete documentation for v2.

NOTE: that this alpha release only implements the 2025-11-25 spec revision. Support for 2026-07-28 feature will be added over time through each alpha release with full 2026-07-28 support targeted for beta release on 2026-06-30.

Stability and timeline

Right now v2 is very breaking, and each alpha will likely contain breaking changes from the previous one, so pin exact versions if you try it. Before the stable release we plan to add a good amount of backwards compatibility shims to reduce the breakage.

Alphas run from now through late June, with a beta targeted for 2026-06-30 and stable v2 targeted for 2026-07-27 (the spec releases 2026-07-28). v1.x is the only stable version of the SDK for now: it stays in maintenance mode and continues to get critical bug fixes and security patches.

TLDR:

• Today (v2.0.0.a1) - Only 2025-11-25 spec functionality support
• Today -> 2026-06-30 - New MCP 2026-07-28 spec functionality will be added to v2 alpha versions and released regularly during this time
  • Each alpha release during this should be considered breaking
• 2026-06-30 (estimated) - A beta version of the SDK will be released with full MCP 2026-07-28 spec support
• 2026-07-01 -> 2026-07-27 - Bug fixes and cleanup
  • Ideally significantly less breaking that each alpha release, although not guaranteed
• 2026-07-28 - A stable v2.0.0 version of the Python SDK will be released along side the MCP 2026-07-28 spec release.

What you should do

If you maintain a package that depends on mcp, add an upper bound now. 84% of the 10,000+ PyPI packages that depend on mcp declare no upper bound, and they'll all resolve to v2 the day the stable release ships. Add <2 to your existing constraint, for example mcp>=1.27,<2, and your users stay on v1 until you've migrated.

If you want to try v2:

pip install mcp==2.0.0a1
# or
uv add mcp==2.0.0a1

One ask: only pin an mcp pre-release from a pre-release of your own package, otherwise you'll drag your users onto the alpha.

Feedback is much appreciated in #python-sdk-dev on the MCP Contributors Discord, or open an issue with the v2-alpha label.