Claude Code reads mcp_set_servers only after its SessionStart hooks finish.
A hook can run up to the CLI's default 10 minute hook timeout, for example
a cold worktree setup script, so the 90 s registration deadline failed the
open while the CLI was healthy. The deadline now covers that hook budget
plus the per-server connect time. The SDK still rejects the request if the
CLI exits, and interrupting the open still closes the query.

Fixes #23151

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>