Claude Opus 5.5 vs DeepSeek-V4.1-Flash
Wins 6 of 8 areas
Coding · Agents · Reasoning · Facts · Images and charts · Math
Wins 1 of 8 areas
Following instructions
Claude Opus 5.5 is the stronger all-rounder.DeepSeek-V4.1-Flash is cheaper and better at following instructions.
Scores updated · 35 tests both models report · How we compare
Where each one wins
Tests won in each of the eight areas we test. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- ReasoningHard problems that need careful thinking50Claude Opus 5.55 of 5 tests
- FactsGetting facts right instead of making them up30Claude Opus 5.53 of 3 tests
- MathCompetition and research-level math30Claude Opus 5.53 of 3 tests
- CodingWriting and fixing software31Claude Opus 5.53 of 4 tests
- Images and chartsUnderstanding pictures, charts and video20Claude Opus 5.52 of 2 tests
- AgentsCarrying out multi-step tasks on its own21Claude Opus 5.52 of 3 tests
- Following instructionsDoing exactly what it is asked01DeepSeek-V4.1-Flash1 of 1 test
- Long documentsFinding answers in very long texts00Even0 each · 1 tie
Long documents and following instructions 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.
DeepSeek-V4.1-Flash costs 94% less for the same work.
The biggest differences
The three tests each model wins by the widest margin. Scores are out of 100.
Where Claude Opus 5.5 pulls ahead
- Extremely hard research-level math problemsFrontierMath Tier 4+48.7points ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+37.9points ahead
- Complex command-line tasks across many fieldsTerminal-Bench 4.0+32.8points ahead
Where DeepSeek-V4.1-Flash pulls ahead
- Finds the root cause of IT system incidentsAA IT-Bench SRE+8.7points ahead
- Fixes real GitHub issues, working as an agentLiveBench · Agentic Coding+5.6points ahead
- Follows detailed instructions exactlyLiveBench · Instruction Following+4.3points ahead
Every test, side by side
All 35 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Opus 5.5
- LMArena · WebDevClaude Opus 5.5 by 190 rating points18091619+190 rating
- SciCodeClaude Opus 5.5 by 1566.951.9+15
- LiveBench · CodingClaude Opus 5.5 by 9.389.380+9.3
- LiveBench · Agentic CodingDeepSeek-V4.1-Flash by 5.671.777.3+5.6
AgentsClaude Opus 5.5
- Terminal-Bench 4.0Claude Opus 5.5 by 32.859.626.8+32.8
- GDPValClaude Opus 5.5 by 13.368.355+13.3
- AA IT-Bench SREDeepSeek-V4.1-Flash by 8.738.246.9+8.7
ReasoningClaude Opus 5.5
- Humanity's Last ExamClaude Opus 5.5 by 22.261.439.2+22.2
- SimpleBenchClaude Opus 5.5 by 21.788.466.7+21.7
- CritPtClaude Opus 5.5 by 17.431.714.3+17.4
- ARC-AGI-2Claude Opus 5.5 by 13.691.778.1+13.6
- LiveBench · ReasoningClaude Opus 5.5 by 5.592.286.7+5.5
FactsClaude Opus 5.5
- AA-Omniscience · Non-hallucinationClaude Opus 5.5 by 37.941.43.5+37.9
- SimpleQA VerifiedClaude Opus 5.5 by 29.372.242.9+29.3
- AA-Omniscience · AccuracyClaude Opus 5.5 by 19.866.246.4+19.8
Images and chartsClaude Opus 5.5
- MMMU-ProClaude Opus 5.5 by 10.787.777+10.7
- LMArena · VisionClaude Opus 5.5 by 43 rating points13211278+43 rating
MathClaude Opus 5.5
- FrontierMath Tier 4Claude Opus 5.5 by 48.79546.3+48.7
- FrontierMath Tiers 1-3 (v2)Claude Opus 5.5 by 2091.271.2+20
- LiveBench · MathematicsClaude Opus 5.5 by 3.897.193.3+3.8
Following instructionsDeepSeek-V4.1-Flash
- LiveBench · Instruction FollowingDeepSeek-V4.1-Flash by 4.365.770+4.3
Other results13 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.
- Program BenchClaude Opus 5.5 by 70.991.220.3+70.9
- AA-OmniscienceClaude Opus 5.5 by 51.746.4-5.3+51.7
- Terminal-Bench 4.0Claude Opus 5.5 by 35.266.431.2+35.2
- OSWorld 2.0Claude Opus 5.5 by 27.581.854.3+27.5
- AA IntelligenceClaude Opus 5.5 by 18.157.639.5+18.1
- vectara_avg_summary_lengthClaude Opus 5.5 by 83.9 rating points192.1108.2+83.9 rating
- vectara_factual_consistencyDeepSeek-V4.1-Flash by 5.790.195.8+5.7
- livebench_languageClaude Opus 5.5 by 5.186.381.2+5.1
- ARC-AGI-1Claude Opus 5.5 by 497.593.5+4
- HLE (with tools)Claude Opus 5.5 by 3.867.763.9+3.8
- livebench_data_analysisClaude Opus 5.5 by 180.379.3+1
- vectara_answer_ratetie99.799.9tie
- DeepSWE 1.1tie74.274.2tie
Questions people ask
Which is better, Claude Opus 5.5 or DeepSeek-V4.1-Flash?
Claude Opus 5.5 wins six of the eight areas we test: coding, agents, reasoning, facts, images and charts and math. DeepSeek-V4.1-Flash wins following instructions, and costs 94% less. They are level on long documents.
Which is better for coding?
Claude Opus 5.5. It wins 3 of the 4 coding tests both models report; DeepSeek-V4.1-Flash wins 1.
Which is cheaper?
Claude Opus 5.5 costs $4.00 per million input tokens and $20.00 per million output tokens; DeepSeek-V4.1-Flash costs $0.30 and $1.20. That makes DeepSeek-V4.1-Flash about 94% cheaper for the same work.
How do you compare the two?
We use the 35 benchmark tests both models have published scores on. The verdict counts the 22 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 13 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.