Claude Haiku 4.5 Thinking - Anyfast

Claude Haiku 4.5 Thinking is the extended thinking variant of Claude Haiku 4.5, available through Anyfast via an OpenAI-compatible interface. It combines Haiku’s speed and cost-efficiency with step-by-step internal reasoning, delivering improved accuracy on complex tasks while remaining significantly faster and cheaper than larger thinking models.

Key capabilities

OpenAI-compatible — Works as a drop-in replacement with the OpenAI SDK
Extended thinking — Step-by-step internal reasoning enabled by default
Fast + affordable — Thinking capability at Haiku-level speed and cost
Streaming — Supports real-time token streaming via SSE
Strong reasoning — Improved accuracy on math, logic, and multi-step problems

Quick example

curl https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-haiku-4-5-20251001-thinking",
    "messages": [
      { "role": "user", "content": "Solve step by step: If a train travels 120 km in 2 hours, then slows down and travels 80 km in 3 hours, what is the average speed for the entire trip?" }
    ]
  }'

Parameters

Parameter	Type	Required	Description
`model`	string	Yes	Must be `claude-haiku-4-5-20251001-thinking`
`messages`	array	Yes	List of `{ role, content }` objects
`max_tokens`	integer	No	Maximum tokens to generate
`temperature`	float	No	`0`–`2`. Controls randomness. Default: `1`
`stream`	boolean	No	Enable SSE streaming. Default: `false`
`top_p`	float	No	Nucleus sampling threshold. Default: `1`
`stop`	string / array	No	Sequences that stop generation

API Reference

View the interactive API playground for Claude Haiku 4.5 Thinking.

Claude Haiku 4.5 Claude 3.7 Sonnet