MCP protocol confusion about server lifecycle vs client session lifecycle

5/10 Medium

The `lifespan` parameter in MCP SDK was ambiguous and commonly misunderstood—developers thought it referred to client sessions when it should refer to server lifecycle (e.g., database connections), causing initialization and cleanup logic to run incorrectly.

MCPFastMCP
Category
dx
Workaround
partial
Stage
build
Freshness
declining
Scope
single_lib
Upstream
open
Recurring
Yes
Buyer Type
team
Maintainer
active

Sources

Collection History

Query: “What are the most common pain points with FastMCP for developers in 2025?”4/8/2026

We fixed a long-standing point of confusion in the MCP SDK. `lifespan` now correctly refers to the *server* lifecycle (for things like DB connections), not the client session. This is a breaking change, but it's the correct one.

Created: 4/8/2026Updated: 4/8/2026