Anthropic released Claude Haiku 5.5 on October 7 through its platform, AWS, Google Cloud, and Microsoft Azure. Prompts up to 100,000 tokens cost $0.10 per million input tokens and $0.50 for output, versus Haiku 4.5's $1 and $5. Above that prompt threshold, Haiku 5.5 costs $0.50 input and $2.50 output. Anthropic also halved Sonnet 5.5 cache-read pricing to $0.10 per million tokens. The system card reports independently run Artificial Analysis GDPval-AA v2.1 results of 1620 Elo for Haiku 5.5 at max effort, versus 735 for Haiku 4.5 and 1840 for Sonnet 5.5. At Haiku's default medium effort, the rating falls to 1277 while output-token use is about a tenth of max. These are professional-work ratings, not accuracy percentages. The launch footnote says the new tokenizer uses slightly more tokens per task. The advertised average saving therefore differs from the posted token-price reduction, and neither guarantees savings on a particular workflow. A queue of short summaries or classification requests is a plausible place to try Haiku. Replacing a larger agent on a difficult workflow is a different decision. The gap between medium and max effort shows why a launch leaderboard cannot predict the setting your application uses. Set effort explicitly and measure cost per accepted result, including retries and corrections. Repeated agent prompts may also benefit from Sonnet's separate cache-read cut without any model substitution. Check that your requests actually generate cache hits. The migration guide is useful for API compatibility, but its living checklist supplies current integration advice rather than proof that every detail was already published at launch. Benchmark one short-request queue at medium effort and compare accepted outputs, corrections, and total cost. Anthropic's benchmark comparisons are inline HTML and SVG, inspected in the browser. The table and linked system card verify the reported ratings, but no public standalone comparison-image URL was verified. External images are decorative intro artwork, not benchmark evidence. This single-file issue cannot publish a new screenshot asset. Claude Haiku 5.5 System Card: Evaluation methods and safety results. Section 8.10.2 separates independent GDPval-AA max-effort and medium-effort ratings and token use. Migrating from Haiku 4.5 to Haiku 5.5: Current integration checklist covering adaptive thinking, token recounting, request parameters, and refusals. Living documentation without a displayed publication date; linked by the October 7 announcement.