What changed
Version 2.1.284 added Claude Sonnet 5.5 (claude-sonnet-5-5) at $2 input and $10 output per million tokens. Anthropic says it costs the same per token as Sonnet 5 but uses fewer tokens, making it up to 30% cheaper per task. Default effort in Claude Code is Medium.
Who it affects
Claude Code users on Sonnet, especially API users.
What to do
Update to 2.1.284 or later. If you ran Sonnet with thinking off, check your settings after upgrading.