Tested on a Claude Pro account on the evening of 7 October 2026, the day Haiku 5.5 launched. Model and plan details checked against Anthropic’s Haiku 5.5 announcement and Claude’s pricing page the same day.
The short answer
For everyday jobs, Claude Haiku 5.5 is good enough. We gave Haiku 5.5 and Sonnet 5.5 the same five tasks, from a short email to a tricky phone-contract sum. Both got every main answer right, with no maths slips.
Speed was close: 21 seconds in total for Haiku against 24 for Sonnet. Sonnet’s answers were a little fuller. Use Haiku for quick questions, Sonnet when you want more detail, and Opus for long or complex work.
Haiku vs Sonnet at a glance
| Haiku 5.5 | Sonnet 5.5 | |
|---|---|---|
| Best for | Quick questions, short emails, simple sums | Everyday tasks where you want a fuller answer |
| Speed in our test | 21 seconds for all 5 tasks | 24 seconds for all 5 tasks |
| Accuracy in our test | 5 of 5 main answers right | 5 of 5 main answers right |
| Default effort in the app | Medium | Medium |
| How the app describes it | “Fastest for quick answers” | “Most efficient for simpler tasks” |
| Which plans | Free, Pro, Max | Free, Pro, Max |
How we tested
- We used a Claude Pro account in Chrome on 7 October 2026, a few hours after Haiku 5.5 launched.
- Every task ran in a fresh incognito chat, so no chat history or saved memory could affect the answers.
- Both models got exactly the same five prompts we used in our Opus vs Sonnet test, word for word, on the app’s default effort (Medium for both).
- We timed both models on the same evening, from pressing send to the moment the answer finished, and checked every number by hand.
- The Sonnet screenshots below come from our earlier test the same day, so their times differ slightly from the chart.
Speed depends on how busy Anthropic’s servers are, so treat our times as a guide, not a lab result.
The results
| Task | Haiku 5.5 | Sonnet 5.5 | Verdict |
|---|---|---|---|
| Landlord email | Good, with a subject line (3 s) | Good, with a subject line (3 s) | Tie |
| UK pension explainer | Accurate (7 s) | Accurate and fuller (9.5 s) | Sonnet, for detail |
| Monthly budget | Correct: £550 to save (3 s) | Correct: £550 to save (3.9 s) | Tie |
| Pen-buying puzzle | Correct: £6.80 (3 s) | Correct: £6.80 (3 s) | Tie |
| Phone contracts | Correct: B cheaper by £32.40 (5 s) | Correct: B cheaper by £32.40 (5 s) | Tie |
1. Writing a polite email
Prompt: “Write a short, polite email to my landlord asking him to fix a kitchen tap that has been dripping for a week. Keep it under 120 words.”
Both emails were polite, clear and well under 120 words, with a subject line and placeholders for names. Haiku’s was ready in about 3 seconds. For a job like this, either model is fine.
2. Explaining UK pension auto-enrolment
Prompt: “Explain UK workplace pension auto-enrolment in 5 bullet points for someone starting their first job.”
Both models searched the web on their own and got the 2026/27 figures right: automatic enrolment from age 22 if you earn over £10,000, at least 8% in total with at least 3% from your employer, and contributions worked out on earnings between £6,240 and £50,270. We checked these against GOV.UK.
This was the one task where Sonnet was clearly better. It explained the one-month window for getting your money back if you opt out, and worked through an example on a £25,000 salary. Haiku’s answer was correct but a little rougher in places, for example “earning above £10,000 threshold”.
3. Making a monthly budget
Prompt: “I take home £2,100 a month. Rent is £850, bills £180, food £250 and travel £120. I want to keep £150 a month for fun. Make a simple budget table and tell me how much I can save each month.”
The right answer is £550 a month (£6,600 a year). Both models got it, in a clear table. Haiku added that £550 is about 26% of your take-home pay, which is correct.
4. A simple money puzzle
Prompt: “Pens cost 80p each, or £2 for a pack of 3. I need exactly 10 pens. What is the cheapest way to buy them, and how much will it cost?”
Both answered correctly: three packs plus one single pen, for £6.80. Both showed why the other options cost more (£7.20 for two packs and four singles, £8 for ten singles).
5. Comparing two phone contracts (the hard one)
Prompt: “Contract A: £35 a month for 24 months, but the first 3 months are half price, plus a £50 upfront fee. Contract B: £28 a month for 24 months, but the monthly price goes up by 3.9% after 12 months, plus £120 upfront for the phone. Which is cheaper over 24 months, and by how much?”
This is the task where Sonnet slipped once in our Opus vs Sonnet test, adding a wrong note about rounding. Haiku got it right first time: Contract B is about £32.40 cheaper (£805.10 against £837.50). It also warned that early exit fees could change the picture. Sonnet got it right this time too.
So which should you use?
- On the Free plan, Claude’s pricing page lists both Haiku and Sonnet. Our test suggests either will handle everyday jobs.
- Pick Haiku for quick questions, short emails, simple sums and summaries, when you just want the answer.
- Pick Sonnet when you want a fuller explanation, such as money or work questions where the detail matters.
- Switch to Opus for long, complex or multi-step work. Our Opus vs Sonnet test shows where it earns its keep.
- Check important numbers whichever model you use.
Anthropic says the model you choose affects how quickly you use your plan’s allowance. It doesn’t publish how much further Haiku goes, but it calls Haiku 5.5 its cheapest model to run, so it’s worth trying for simple chats if you keep hitting your limit. Our Claude Pro vs Max guide explains how limits work.
What’s new in Claude Haiku 5.5
- Anthropic released it on 7 October 2026. On our account it replaced Haiku 4.5 in the model menu the same evening.
- Anthropic calls it “the cheapest, fastest, and most capable small model we’ve ever released.”
- It is the first Haiku model with an adjustable effort setting. The app sets it to Medium by default.
- For developers, Anthropic says it costs about 75% less to run than Haiku 4.5 on average. The API name is claude-haiku-5-5.
- Anthropic says Sonnet 5.5 and Opus 5.5 are still better for complex coding work.
What each plan includes
| Plan | Haiku | Sonnet | Opus | UK price |
|---|---|---|---|---|
| Free | Yes | Yes | No | £0 |
| Pro | Yes | Yes | Yes | £18 a month (£15 paid yearly) |
| Max | Yes | Yes | Yes | From £90 a month |
Claude’s pricing page lists “Haiku” without a version number. We tested on a Pro account, so check the model menu to see which Haiku your plan shows. New to Claude? Start with Is Claude free? or see what changed in Sonnet 5.5.
FAQ
Is Claude Haiku 5.5 free?
Claude’s pricing page lists Haiku on every plan, including Free, but doesn’t say which version. We tested on a paid Pro account, so check the model menu on your own account.
Is Haiku better than Sonnet?
No, but for everyday tasks the gap is small. In our test both got all five main answers right, and Sonnet gave fuller answers. Anthropic says Sonnet 5.5 and Opus 5.5 are still better for complex coding.
Is Haiku faster than Sonnet?
A little. Haiku finished our five tasks in 21 seconds against 24 for Sonnet. On three of the five tasks they took the same time.
How do I switch to Haiku 5.5?
Click the model name next to the chat box and choose Haiku 5.5. If you don’t see it, update the Claude app.
What happened to Haiku 4.5?
Earlier on 7 October 2026 our model menu still showed Haiku 4.5. By that evening it showed Haiku 5.5 instead.
How this test was made
- Tests run by AI Start Compass on a Claude Pro account on 7 October 2026, in incognito chats, with every answer checked by hand.
- Pension figures checked against GOV.UK; model details against Anthropic’s announcement; plan details against Claude’s pricing page.
- Drafted with help from an AI writing assistant, then fact-checked and edited by Adsen. No affiliate links.
