What
MCP servers are outside programs that give Claude extra tools. Compaction is when Claude Code shortens a long conversation to save space. Before, if a tool's MCP server was reconnecting at that moment, the tool's entry could be dropped. It is now kept, carried in a separate group for tools without a deferred channel. Servers under HIPAA restrictions (a US health-privacy law) are excluded from this.
The telemetry that records tools dropped at compaction gains a noDeferredChannel field to tell these two cases apart.
Why
A server that briefly drops and reconnects during compaction no longer makes Claude lose track of its tools.