Claude Opus 5.5 is the new default Claude

The model

• Claude Opus 5.5 (claude-opus-5-5) replaces Opus 5 and is now the recommended Claude model in TeamDay. Anthropic released it on September 22 and tells most teams to start with it.
• 1M token context window and up to 128k output tokens.
• Cheaper than Opus 5: $4 / $20 per million tokens (input / output), with cache hits at $0.20.
• Full reasoning-effort ladder (low → max), defaulting to high.

What happens to Opus 5

• New chats and agents now default to Opus 5.5.
• Existing agents and chats set to Opus 5 (or Opus 4.x) move to Opus 5.5 automatically. You don't need to do anything, and the new model costs less.

The Claude lineup in TeamDay

• Opus 5.5: the default for everyday and complex work.
• Fable 5.1: the most capable option, for the hardest and longest-running tasks.
• Sonnet 5: efficient for routine tasks.
• Haiku 4.5: fastest for quick answers.