Anthropic launched Claude Haiku 5.5 on October 7, 2026 at $0.10 per million input tokens, 20 times less than the $2.00 of Claude Sonnet 5.5. In exchange, on Terminal-Bench 4.0, the test closest to what a coding agent actually does, Haiku scores 39.2% and Sonnet scores 70.6%.
This guide puts the numbers side by side, says where each one comes from, and shows how to call both models so you can test them on your own repository. Everything checked on 10/27/2026 against Anthropic's launch page.
Which is better for coding, Haiku 5.5 or Sonnet 5.5?
For an agent that runs commands in the terminal, reads the error and iterates until the test passes, Sonnet 5.5. The gap is 31 points on Terminal-Bench 4.0. For small, repetitive, high-volume work such as summarizing, classifying, compacting context or running a subagent, Haiku 5.5 delivers at 5% of the price.
Anthropic itself says Haiku 5.5 is meant for high-volume, narrowly scoped work, and that Sonnet 5.5 and Opus 5.5 remain the choice for complex agentic coding, like the kind measured by Terminal-Bench 4.0.
What do the benchmarks say?
The table collects the tests from the launch table published by Anthropic. These are the vendor's numbers, not third-party results.
| Benchmark | Haiku 5.5 | Sonnet 5.5 | Haiku 4.5 |
|---|---|---|---|
| Terminal-Bench 4.0 | 39.2% | 70.6% | 0.0% |
| FrontierCode 1.1 (Main) | 46.4% | 52.1% (Xhigh effort) | not reported |
| OSWorld 2.1 (offline subset) | 72.4% | 83.9% | 15.7% |
| GDPval-AA v2.1 (Elo) | 1620 | 1840 | 735 |
| Humanity's Last Exam (no tools) | 45.9% | 56.9% | 10.2% |
| Humanity's Last Exam (with tools) | 57.4% | 64.5% | 18.7% |
Source: Claude Haiku 5.5 launch page (Anthropic, 10/07/2026), accessed 10/27/2026.
Two readings matter. First: Sonnet 5.5 wins every row, but the distance varies a lot. On FrontierCode it is 5.7 points. On Terminal-Bench it is 31.4. If your work looks like the first, Haiku gets close. If it looks like the second, it does not. Second: Anthropic measured Sonnet at Xhigh effort on FrontierCode. VentureBeat reported that Haiku's Terminal-Bench score drops to about 20% at medium effort, versus 39% at maximum, so the table number assumes high effort and more tokens spent.
How much does each one cost?
Haiku 5.5 costs 20 times less per token in the tier up to 100 thousand tokens per prompt. Above that its price goes up and the gap falls to 4 times, according to Anthropic's price table, which lists a single price for Sonnet 5.5.
| Attribute | Haiku 5.5 | Sonnet 5.5 |
|---|---|---|
| API ID | claude-haiku-5-5 | claude-sonnet-5-5 |
| Input (per 1M tokens) | $0.10 up to 100K, $0.50 above | $2.00 |
| Output (per 1M tokens) | $0.50 up to 100K, $2.50 above | $10.00 |
| Cache write | $0.125 up to 100K, $0.625 above | $2.50 |
| Cache read | $0.01 up to 100K, $0.05 above | $0.10 |
| Effort control | Low, Med, High, Xhigh, Max | yes |
Source: Claude Haiku 5.5 launch page (Anthropic, 10/07/2026) and VentureBeat (10/07/2026), accessed 10/27/2026. Sonnet 5.5's cache read price dropped from $0.20 to $0.10 alongside the launch.
Our own math from those prices: a prompt with 50 thousand input tokens and 5 thousand output tokens costs about $0.0075 on Haiku and $0.15 on Sonnet. But price per token is not cost per task. If Haiku needs two or three attempts where Sonnet gets it right the first time, the difference shrinks, and if it never gets it right, the difference disappears. VentureBeat makes the same warning when comparing it with GPT-6 Luna, which has the same base price table.
When should you pick Claude Haiku 5.5?
- When the work is high-volume and narrow: summarizing files, classifying issues, extracting fields, querying a database.
- When it runs as a subagent, reading code and compacting context under a larger model that plans and decides.
- When the prompt fits within 100 thousand tokens, which is where the low price lives. Anthropic says about 90% of Haiku 4.5 requests fall in that range.
- When latency matters more than the last layer of quality, like live customer support.
When should you pick Claude Sonnet 5.5?
- When the agent lives in the terminal: runs a test, reads the error, fixes, runs again. That is a 31-point lead on Terminal-Bench 4.0.
- When the task is long, open-ended engineering that does not fit a short instruction.
- When a wrong attempt costs more than the token you saved, like a refactor that breaks the build.
- When you run large prompts, above 100 thousand tokens, and Haiku's price stops being 20 times lower.
How do you test both on your code?
Benchmarks tell you the trend; your repository tells you the rest. Run the same request on both and compare the result and the cost.
Claude Haiku 5.5 through the Anthropic API:
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": 4096,
"messages": [
{"role": "user", "content": "Find the bug in this function and propose the failing test: ..."}
]
}'For Sonnet 5.5, only change the model field to claude-sonnet-5-5. To test as a terminal agent, inside your own repository, with each:
claude --model claude-haiku-5-5
claude --model claude-sonnet-5-5Give both the same multi-step task (for example, "make test X pass") and compare how many rounds each needed and how much showed up on the bill. That number, not the one in the table, decides.
Summary: which one to pick?
| If your case is... | Pick |
|---|---|
| Terminal agent, test and fix loop | Claude Sonnet 5.5 |
| Subagent that reads, summarizes and compacts | Claude Haiku 5.5 |
| Classifying or extracting at high volume | Claude Haiku 5.5 |
| Large refactor, where a mistake is expensive | Claude Sonnet 5.5 |
| Prompts above 100 thousand tokens | Claude Sonnet 5.5 |
Both charge per token, and in a coding agent the bill grows with every attempt, even on Haiku at $0.10. If you are tired of dealing with that, Verboo Code offers unlimited tokens.
