How to Use Claude Haiku 5.5 as a Coding Subagent

Anthropic released Claude Haiku 5.5 on 7 October 2026 as the fastest and cheapest small model in the Claude 5.5 family. It handles high-volume, cost-sensitive work and pairs well with Opus 5.5 or Sonnet 5.5 as a subagent on coding tasks.

This guide shows practical ways to route simple jobs to Haiku 5.5 while keeping complex reasoning on larger models, based on Anthropic’s official details.

Why Haiku 5.5 fits subagent roles

Haiku 5.5 costs $0.10 per million input tokens and $0.50 per million output tokens for prompts up to 100,000 tokens. That is roughly 90 percent cheaper than Haiku 4.5 on those lengths, and Anthropic reports an average 75 percent lower cost overall after accounting for the new tokenizer.

It supports a 1 million token context window and up to 128k output tokens. Adaptive thinking is on by default, and you can adjust effort from low to max. These traits make it useful for routing, classification, summarization of code diffs, and quick reviews that do not need the full power of Opus.

Step 1: Get access

Haiku 5.5 is available on Claude.ai for Free, Pro, Max, Team, and Enterprise plans. Select it from the model menu on web, iOS, or Android.

For API use the model ID claude-haiku-5-5 on the Claude Platform, Amazon Bedrock, Google Cloud, and Microsoft Foundry. Pricing starts at the low rates above for shorter prompts and rises for prompts over 100k tokens.

If you already use Claude Code, Haiku 5.5 is available there as well. Confirm the model appears in your account before building workflows around it.

Step 2: Route tasks by size and complexity

Send classification, extraction, and short summarization jobs to Haiku 5.5. Examples include tagging pull-request comments, extracting function names from a diff, or deciding whether a ticket matches a template.

Keep architecture decisions, multi-file refactors, and long-horizon debugging on Sonnet 5.5 or Opus 5.5. Anthropic notes that Haiku 5.5 works especially well as a subagent that larger models can call for the repetitive pieces.

Start with effort set to medium. Raise it only if the small model misses edge cases. Lower it for pure classification to cut latency and cost further.

Step 3: Measure token use and quality

Because Haiku 5.5 uses the newer tokenizer, the same text can count as about 30 percent more tokens than on Haiku 4.5. Track actual token consumption in your first runs rather than relying on old estimates.

Compare outputs on a small set of real tasks. Anthropic reports gains over Haiku 4.5 on coding, tool use, and agentic evaluations, but your codebase may differ. Adjust prompts or effort if quality drops.

Cache reads are inexpensive. Reuse context where possible when the same files appear across many subagent calls.

Practical patterns

One pattern is a larger model that plans the change, then hands the file-by-file checks or comment generation to Haiku 5.5. Another is a router that sends simple lint-style questions to Haiku and escalates only when the small model returns low confidence.

Set clear stop conditions. Haiku 5.5 is fast enough for live support or browser-style loops, but you still want human review on production changes.

For migration notes and breaking changes, consult Anthropic’s official Haiku 5.5 documentation. Existing max_tokens values remain valid, yet thinking tokens count toward the limit.

See our earlier guide on switching to Claude Sonnet 5.5 for related model choices.

Tips

Test the new effort controls on a few representative tasks before rolling out widely. Monitor cost per task rather than per token, since fewer tokens on some jobs can offset the tokenizer change.

Keep security reviews on the larger models. Haiku 5.5 includes improved alignment relative to Haiku 4.5, yet Anthropic positions the frontier models for the highest-stakes work.

Update any hard-coded model strings in your scripts once you confirm the exact ID in your platform.

Conclusion

Claude Haiku 5.5 gives developers a low-cost, fast option for the high-volume pieces of coding workflows. Route classification and extraction to it, keep complex reasoning on Sonnet or Opus, and measure results on your own tasks. The model is available now across Claude surfaces and major cloud platforms.

Sources

• Introducing Claude Haiku 5.5 — Anthropic, 7 October 2026
• Claude platform model overview and pricing documentation