Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) vs Claude Opus 5
Wins 4 of 5 areas
Coding · Agents · Reasoning · Long documents
Wins 0 of 5 areas
—
Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) is the stronger all-rounder.
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 own20Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)2 of 2 tests
- ReasoningHard problems that need careful thinking10Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)1 of 2 tests · 1 tie
- CodingWriting and fixing software10Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)1 of 1 test
- Long documentsFinding answers in very long texts10Claude 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 Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) costs 60% 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
- Complex command-line tasks across many fieldsTerminal-Bench 4.0+14.6points ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+13.8points ahead
- Real work tasks from 44 professionsGDPVal+5.8points ahead
Where Claude Opus 5 pulls ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+6.9points 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 4.66156.4+4.6
AgentsClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- Terminal-Bench 4.0Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 14.663.649+14.6
- GDPValClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 5.86761.2+5.8
ReasoningClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- CritPtClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 2.331.429.1+2.3
- Humanity's Last Examtie5554.9tie
FactsEven
- AA-Omniscience · Non-hallucinationClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 13.85339.2+13.8
- AA-Omniscience · AccuracyClaude Opus 5 by 6.95460.9+6.9
Long documentsClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback)
- AA-LCRClaude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) by 3.482.779.3+3.4
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 5.25650.8+5.2
- AA-OmniscienceClaude Opus 5 by 4.832.337.1+4.8
Questions people ask
Which is better, Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) or Claude Opus 5?
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 Opus 5 wins none. 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 Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) costs $2.00 per million input tokens and $10.00 per million output tokens; Claude Opus 5 costs $5.00 and $25.00. That makes Claude Sonnet 5.5 (Adaptive Reasoning, Max Effort, Default Fallback) about 60% 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.