Claude Haiku 4.5 vs Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
Wins 0 of 5 areas
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Wins 4 of 5 areas
Coding · Agents · Reasoning · Long documents
Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) is the stronger all-rounder.Claude Haiku 4.5 is cheaper.
Scores updated · 10 tests both models report · How we compare
Where each one wins
Tests won in each of the five areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- AgentsCarrying out multi-step tasks on its own02Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)2 of 2 tests
- ReasoningHard problems that need careful thinking02Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)2 of 2 tests
- CodingWriting and fixing software01Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)1 of 1 test
- Long documentsFinding answers in very long texts01Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)1 of 1 test
- FactsGetting facts right instead of making them up11Even1 each
Coding and long documents rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Claude Haiku 4.5 costs 50% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) pulls ahead
- Real work tasks from 44 professionsGDPVal+55.2points ahead
- Very hard expert questions across many subjectsHumanity's Last Exam+44.6points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+36points ahead
Where Claude Haiku 4.5 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+19.7points ahead
Every test, side by side
All 10 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- SciCodeClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 18.842.261+18.8
AgentsClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- Terminal-Bench 4.0Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 63.6063.6+63.6
- GDPValClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 55.211.867+55.2
ReasoningClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- Humanity's Last ExamClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 44.610.455+44.6
- CritPtClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 31.4031.4+31.4
FactsEven
- AA-Omniscience · AccuracyClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 361854+36
- AA-Omniscience · Non-hallucinationClaude Haiku 4.5 by 19.772.753+19.7
Long documentsClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- AA-LCRClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 8.474.382.7+8.4
Other results2 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- AA IntelligenceClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 39.116.956+39.1
- AA-OmniscienceClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 36.7-4.432.3+36.7
Questions people ask
Which is better, Claude Haiku 4.5 or Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)?
Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) wins four of the five areas where both have results: coding, agents, reasoning and long documents. Claude Haiku 4.5 wins none, but costs 50% less. They are level on facts.
Which is better for coding?
Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback). It wins the one coding test both models report.
Which is cheaper?
Claude Haiku 4.5 costs $1.00 per million input tokens and $5.00 per million output tokens; Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) costs $2.00 and $10.00. That makes Claude Haiku 4.5 about 50% cheaper for the same work.
How do you compare the two?
We use the 10 benchmark tests both models have published scores on. The verdict counts the 8 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 2 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.