Claude Haiku 4.5 Thinking extends Anthropic's Haiku family into the reasoning-model era, pairing the line's signature efficiency with controllable extended thinking and full tool-assisted workflows that cover coding and computer-use tasks. The thinking variant is aimed at developers who need step-by-step problem solving without paying frontier-tier latency, and it ships alongside standard tool calling and structured output support so it can drop into agent pipelines that already speak the Claude API. Third-party directories describe the underlying Haiku 4.5 model as Anthropic's fastest, most efficient offering, positioning it as a near-frontier option tuned for real-time, high-volume workloads rather than heavyweight offline reasoning.

In practice, Haiku 4.5 Thinking is reported to score 73% on SWE-bench Verified, which third-party observers read as matching Sonnet-level software engineering capability while keeping response times and per-token costs low enough for production code-review and coding-agent use cases. A Qodo head-to-head on 400 real GitHub pull requests using a 4096-token thinking budget shows the Haiku thinking variant outperforming Sonnet 4.5 Thinking on average code suggestion quality, reinforcing its fit for automated review, refactoring assistants, and tool-driven coding agents where budget-friendly reasoning and reliable tool execution matter more than maximum raw capability.