Anthropic launched Claude Haiku 5.5, a lightweight model with 90% lower base pricing at $0.10 input and $0.50 output per million tokens. It features adaptive thinking for high-concurrency tasks. However, a new tokenizer increases token usage by 25-30%, resulting in a net 75% cost reduction. Prices surge fivefold beyond 100k tokens, requiring careful workflow management to avoid hidden costs.