Claude Haiku 4.5

TL;DR Highlight

Anthropic launched Claude Haiku 4.5, a small model delivering Sonnet 4-level coding performance at 1/3 the price and 2x+ the speed. A cost-effective option for developers needing agentic coding and real-time responses.

Who Should Read

Backend/full-stack developers running coding agents or chatbots on Claude API who want to reduce cost and latency. AI engineers looking for sub-agent models in multi-agent architectures.

Core Mechanics

Claude Haiku 4.5 matches the coding performance of Sonnet 4 (a frontier model from 5 months ago) at 1/3 the price ($1/M input, $5/M output) and 2x+ speed.
Achieved 90% of Sonnet 4.5 performance on Augment's agentic coding benchmark. Even outperformed Sonnet 4 on Computer Use tasks.
Particularly useful in multi-agent setups. Anthropic directly proposed an orchestration pattern: Sonnet 4.5 decomposes complex problems and plans, while multiple Haiku 4.5 instances handle subtasks in parallel.
Recorded statistically significantly lower misalignment behavior rates than Sonnet 4.5 and Opus 4.1 in safety evaluations — evaluated as Anthropic's safest model. Released at ASL-2 safety level.
Available immediately in Claude Code and via API with model ID `claude-haiku-4-5`.

Evidence

Early tests showed Haiku 4.5 avoids touching unrelated code compared to GPT-5, potentially making actual usage costs lower than the token price difference suggests. However, the 4x price increase from Haiku 3.5 ($0.25→$1/M input) was noted as a concern.
A direct comparison found Haiku 4.5 hallucinated function outputs giving wrong answers while Sonnet was accurate — the small model hallucination limitation persists.
On NYT Connections benchmark, Haiku 4.5 scored 20.0 (2x Haiku 3.5's 10.0) but still trails Sonnet 4.0 (26.6) and Sonnet 4.5 (46.1).
A freelancer said '3x faster responses outweigh slight quality loss for productivity' and planned switching daily driver from Sonnet 4.5 to Haiku 4.5.

How to Apply

In multi-agent systems, use Sonnet 4.5 as the main agent for planning/decomposition and Haiku 4.5 as parallel sub-agents to significantly cut costs while boosting throughput.
For quick prototyping or simple code fixes in Claude Code, switching to Haiku 4.5 cuts response wait time by half or more.
For chatbots or customer service agents where latency matters, Haiku 4.5 instead of Sonnet delivers 1/3 cost savings and improved responsiveness simultaneously.
However, for tasks requiring accurate fact lookup or code documentation reference, maintain Sonnet due to hallucination risk, and route only simple generation/transformation tasks to Haiku.

Terminology

ASL-2Anthropic's AI safety rating system. Lower numbers indicate the model is judged lower risk. ASL-3 has stricter restrictions.

Computer UseAn AI model capability to see actual computer screens and operate mouse/keyboard. Can browse the web or manipulate apps like a human.

Agentic CodingAI autonomously planning, executing multi-step processes, and writing/modifying code — beyond simple code completion.

OrchestrationA pattern of coordinating multiple AI models or agents to handle a large task. Like a conductor leading an orchestra, the main model distributes work to sub-models.

HallucinationAI confidently fabricating non-existent information. Like claiming a function exists when it doesn't, or inventing incorrect API responses.