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The MCP Python SDK backported the same session-expiry and issuer-validation defaults to the 1.x line the same afternoon
v1.30.0 shipped 2026-09-07 within two hours of v2.2.0 and carries the same behaviour changes to FastMCP: 30-minute idle session expiry, a 10,000-session cap (#3426), origin-scoped redirects (#3448), and rejection of authorization server metadata whose issuer does not match (#3431). It adds one thing 2.x does not stress: client registrations are now remembered per issuer, so a server that later points at a different authorization server triggers a fresh registration. Anyone pinned to 1.x for the older API surface gets the breaking defaults anyway.
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