How to Use Claude Haiku 5.5 for Fast Classification Tasks

Anthropic released Claude Haiku 5.5 on October 7, 2026. It targets high-volume, latency-sensitive work such as classification, extraction, and routing. The model ID is claude-haiku-5-5. It offers a 1 million token context window and up to 128k output tokens. Pricing starts at $0.10 per million input tokens and $0.50 per million output tokens for prompts under 100k tokens (higher rates apply above that threshold). Cache reads are especially cheap at $0.01 / $0.05 per million.

This guide shows how to call the API for practical classification and routing use cases. It assumes you have an Anthropic API key.

Get Your API Key and Set Up

Sign in to the Claude Console and create an API key. Store it as an environment variable:

export ANTHROPIC_API_KEY="your-key-here"

Never hard-code the key in source files. The official Messages API endpoint is https://api.anthropic.com/v1/messages. Include the header anthropic-version: 2023-06-01.

Make Your First Classification Call

Use curl for a quick test. This example classifies a support ticket:

curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-haiku-5-5",
    "max_tokens": 200,
    "output_config": {"effort": "low"},
    "messages": [
      {"role": "user", "content": "Classify this ticket as billing, bug, or feature request. Reply with only the category: The export button times out on large projects."}
    ]
  }'

The response returns a short label. Low effort keeps latency and cost minimal for simple classification.

In Python (using the official SDK):

import anthropic

client = anthropic.Anthropic()
response = client.messages.create(
    model="claude-haiku-5-5",
    max_tokens=200,
    output_config={"effort": "low"},
    messages=[{"role": "user", "content": "Classify this ticket as billing, bug, or feature request. Reply with only the category: The export button times out on large projects."}]
)
print(response.content[0].text)

Control Effort for Cost and Quality

Haiku 5.5 supports an output_config.effort parameter with values: low, medium (default), high, xhigh, and max. Adaptive thinking is on by default. Lower effort reduces tokens and latency for routing or classification. Higher effort helps when the input is ambiguous.

For high-volume routing (for example, directing customer messages to the right team), start with low or medium. Test a sample of your real traffic and measure accuracy before scaling.

Route Multi-Step Workflows with Subagents

Haiku 5.5 works well as a fast subagent under a stronger model such as Claude Sonnet 5.5 or Opus 5.5. In Claude Code (version 2.1.293 or later), define an agent file with model: haiku and a low effort setting. The parent model can delegate classification or extraction while keeping the main reasoning on the stronger model.

Practical Tips

• Keep prompts under 100k tokens when possible to stay in the lower pricing tier.
• Use prompt caching for repeated system instructions or few-shot examples. Cache reads are very inexpensive.
• For batch processing, the Message Batches API supports larger outputs with the appropriate beta header.
• Omit sampling parameters such as temperature on Haiku 5.5; they can return errors.
• Monitor token usage. The newer tokenizer counts roughly 30% more tokens for the same text than Haiku 4.5.

If you already use Claude models for Android or developer workflows, see our related guide on Claude Haiku 5.5 API setup.

Watch the Overview

Conclusion

Claude Haiku 5.5 lowers the cost of high-volume classification and routing while keeping a large context window and controllable effort levels. Start with low-effort classification calls, measure accuracy on your data, and scale the same pattern for extraction or subagent tasks. Official pricing and model details are on Anthropic’s site and platform documentation.

Sources: Anthropic Claude Haiku 5.5 announcement and platform docs (October 7, 2026); Claude API Messages endpoint documentation.