MCP ecosystem speaks five protocol revisions at once

Pennyforge probed 186 remote MCP endpoints and 10 local stdio servers: only 7.3% of responding endpoints accept the new 2026-07-28 revision, while flagship npm servers still run the 2025-06-18 wire. About 47% of endpoints are auth-gated.

• 86 of 186 endpoints (46%) are auth-gated and invisible to anonymous probes
• Only 8 of 109 responding endpoints (7.3%) accept the 2026-07-28 revision
• All five answering local npm servers speak the 2025-06-18 wire
• Servers negotiate: they echo any requested version within their supported range