Claude Haiku 5.5: six breaking API changes and 5x price jump above 100K tokens

Claude Haiku 5.5 launched on October 7, 2026, adding adaptive thinking, a 1M-token context window and 128K output. Pricing is $0.10/$0.50 per million tokens, one tenth of Haiku 4.5, but requests above 100K tokens are billed at five times that rate. Migration breaks budget_tokens, temperature, prefill and computer_20250124, which now return HTTP 400.

• Pricing is $0.10/$0.50 per 1M tokens, rising to $0.50/$2.50 above 100K tokens
• budget_tokens, temperature and prefill now return HTTP 400
• Thinking is on by default, raising token usage by about 30%
• Minimum cacheable prompt drops from 4,096 to 512 tokens