Claude Opus 4.8 vs Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)
Wins 0 of 5 areas
—
Wins 4 of 5 areas
Coding · Agents · Reasoning · Long documents
Claude Opus 5.5 (Adaptive Reasoning, Medium 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 own02Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)2 of 2 tests
- ReasoningHard problems that need careful thinking02Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)2 of 2 tests
- CodingWriting and fixing software01Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)1 of 1 test
- Long documentsFinding answers in very long texts01Claude Opus 5.5 (Adaptive Reasoning, Medium 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 Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) costs 20% 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 Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) pulls ahead
- Complex command-line tasks across many fieldsTerminal-Bench 4.0+30.8points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+15.8points ahead
- Research-level physics problemsCritPt+6.8points ahead
Where Claude Opus 4.8 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+29.1points 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 Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)
- SciCodeClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 4.954.459.3+4.9
AgentsClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)
- Terminal-Bench 4.0Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 30.821.752.5+30.8
- GDPValClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 6.547.854.3+6.5
ReasoningClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)
- CritPtClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 6.820.927.7+6.8
- Humanity's Last ExamClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 648.754.7+6
FactsEven
- AA-Omniscience · Non-hallucinationClaude Opus 4.8 by 29.160.731.6+29.1
- AA-Omniscience · AccuracyClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 15.848.864.5+15.8
Long documentsClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)
- AA-LCRClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 6.677.784.3+6.6
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-OmniscienceClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 11.528.840.3+11.5
- AA IntelligenceClaude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) by 9.441.851.2+9.4
Questions people ask
Which is better, Claude Opus 4.8 or Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback)?
Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) wins four of the five areas where both have results: coding, agents, reasoning and long documents. Claude Opus 4.8 wins none. They are level on facts.
Which is better for coding?
Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback). It wins the one coding test both models report.
Which is cheaper?
Claude Opus 4.8 costs $5.00 per million input tokens and $25.00 per million output tokens; Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) costs $4.00 and $20.00. That makes Claude Opus 5.5 (Adaptive Reasoning, Medium Effort, Default Fallback) about 20% 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.