Claude Haiku 3.5

Overview

Anthropic's former speed-tier model, retired from the API on February 19, 2026. Claude Haiku 3.5 defined the latency-sensitive Claude tier — classification, extraction, real-time chat — before being succeeded by Claude Haiku 4.5.

Why it matters

Haiku 3.5 mattered because it proved Claude-level safety and instruction-following could ship at commodity pricing, unlocking high-volume workloads like customer support and document triage. It is now retired: API calls to it return errors, and any production system still referencing it needs to migrate to Claude Haiku 4.5. The retirement is a useful case study in model lifecycle risk — teams that hardcoded model IDs without a migration plan saw pipelines fail silently. Budget for model turnover the way you budget for dependency upgrades.