MCP extensions get three maturity levels. The next spec release may wait for March 2027.
By Lior AharonovFounder, 7IT Solutions ·
SEP-3392, filed 25 September 2026, sorts MCP extensions into experimental-ext-, beta-ext- and ext- names. Apps and auth would start as stable, skills and tasks as beta. A second proposal, SEP-3398, proposes releases every March and September, starting in March 2027.
The identifier your server advertises becomes a promise. An experimental extension can change with one maintainer's approval; a stable one moves only with the core protocol.
List the extensions your server and client advertise today, and note which would land as experimental, so a rename does not break clients overnight.
Labels are cheap until a client trusts them. Then a renamed extension is an outage.
Lior Aharonov · my takeSources
- SEP-3392: Extension Lifecycle (GitHub) github.com
- SEP-3398: Release Cycle Updates (GitHub) github.com
Researched with AI tools; every fact is checked against the linked sources.