Sonnet 4.6 vs Haiku 4.5 vs Opus 4.6: I Tested 3 Claude Models on 10 Real Tasks

Evaluated on April 15, 2026 using AgentHunter Eval v0.3.1

Which Claude model should you use for your agent? I tested the latest versions of all three on the same 10 tasks to find out.

Results

Only Opus 4.6 scored a perfect 10/10. Sonnet 4.6 and Haiku 4.5 both stumbled on the same task. Haiku was 2.5x faster than the other two.

The 10 Tasks

Coding (5 tasks)

Writing & Docs (5 tasks)

Key Findings

1. Test writing is the hardest task for smaller models

Both Sonnet 4.6 and Haiku 4.5 failed the "write unit tests" task. This task requires generating a test file with correct assertions against a provided calculator function — it demands precise understanding of both the source code and test framework patterns. Only Opus 4.6 handled it correctly.

Takeaway: For tasks requiring multi-file reasoning (reading source + generating corresponding tests), Opus is worth the cost.

2. Haiku 4.5 is absurdly fast

At 3.9s average, Haiku is 2.5x faster than Sonnet 4.6 (10.2s) and 2.4x faster than Opus 4.6 (9.4s). For the README task, Haiku took 8.7s vs Sonnet's 32.0s — a 3.7x difference.

With 9/10 pass rate at that speed, Haiku is the clear winner for high-volume, latency-sensitive workloads.

3. Sonnet 4.6 is surprisingly slow

Sonnet 4.6 averaged 10.2s — actually slower than Opus 4.6 (9.4s) while passing fewer tasks (9 vs 10). This is unexpected: Sonnet is supposed to be the balanced middle option, but on these tasks, Opus delivers better accuracy at comparable speed.

4. Writing tasks are easy for everyone

All three models scored 10/10 on writing and documentation tasks. Emails, summaries, shell scripts, READMEs — no differentiation. The quality gap only appears on complex code reasoning tasks.

My updated recommendation

Try it yourself

npx @agenthunter/eval task -c task.yaml

All evaluation data: github.com/OrrisTech/agent-eval/results

Full interactive results: eval.agenthunter.io

Built with AgentHunter Eval — the open-source AI agent evaluation platform. npx @agenthunter/eval task