Claude Opus 5.5 vs GLM-5.3-Flash
Wins 8 of 8 areas
Coding · Agents · Reasoning · Facts · Images and charts · Math · Long documents · Following instructions
Wins 0 of 8 areas
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Claude Opus 5.5 is the stronger all-rounder.GLM-5.3-Flash is cheaper.
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.
- CodingWriting and fixing software40Claude Opus 5.54 of 4 tests
- ReasoningHard problems that need careful thinking40Claude Opus 5.54 of 4 tests
- MathCompetition and research-level math30Claude Opus 5.53 of 3 tests
- AgentsCarrying out multi-step tasks on its own31Claude Opus 5.53 of 4 tests
- FactsGetting facts right instead of making them up21Claude Opus 5.52 of 3 tests
- Images and chartsUnderstanding pictures, charts and video10Claude Opus 5.51 of 1 test
- Long documentsFinding answers in very long texts10Claude Opus 5.51 of 1 test
- Following instructionsDoing exactly what it is asked10Claude Opus 5.51 of 1 test
Images and charts, 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.
GLM-5.3-Flash costs 97% 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 pulls ahead
- Extremely hard research-level math problemsFrontierMath Tier 4+77.9points ahead
- Short factual questions, answered correctlySimpleQA Verified+40.2points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+38.7points ahead
Where GLM-5.3-Flash pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+31points ahead
- Finds the root cause of IT system incidentsAA IT-Bench SRE+13points 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 205 rating points18141609+205 rating
- SciCodeClaude Opus 5.5 by 15.366.951.6+15.3
- LiveBench · Agentic CodingClaude Opus 5.5 by 14.971.756.8+14.9
- LiveBench · CodingClaude Opus 5.5 by 10.389.379+10.3
AgentsClaude Opus 5.5
- Terminal-Bench 4.0Claude Opus 5.5 by 26.859.632.8+26.8
- BrowseCompClaude Opus 5.5 by 14.890.876+14.8
- AA IT-Bench SREGLM-5.3-Flash by 1338.251.2+13
- GDPValClaude Opus 5.5 by 11.168.357.2+11.1
ReasoningClaude Opus 5.5
- ARC-AGI-2Claude Opus 5.5 by 25.991.765.8+25.9
- Humanity's Last ExamClaude Opus 5.5 by 21.561.439.9+21.5
- CritPtClaude Opus 5.5 by 16.331.715.4+16.3
- LiveBench · ReasoningClaude Opus 5.5 by 14.692.277.6+14.6
FactsClaude Opus 5.5
- SimpleQA VerifiedClaude Opus 5.5 by 40.272.232+40.2
- AA-Omniscience · AccuracyClaude Opus 5.5 by 38.766.227.5+38.7
- AA-Omniscience · Non-hallucinationGLM-5.3-Flash by 3141.472.4+31
Images and chartsClaude Opus 5.5
- LMArena · VisionClaude Opus 5.5 by 29 rating points13241295+29 rating
MathClaude Opus 5.5
- FrontierMath Tier 4Claude Opus 5.5 by 77.99517.1+77.9
- FrontierMath Tiers 1-3 (v2)Claude Opus 5.5 by 35.491.255.8+35.4
- LiveBench · MathematicsClaude Opus 5.5 by 15.997.181.2+15.9
Following instructionsClaude Opus 5.5
- LiveBench · Instruction FollowingClaude Opus 5.5 by 12.965.752.8+12.9
Other results14 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.
- Terminal-Bench-Science 0.1Claude Opus 5.5 by 54.2594.8+54.2
- HLE-DiamondClaude Opus 5.5 by 49.767.918.2+49.7
- CritPt v2 HardClaude Opus 5.5 by 43.56824.5+43.5
- AA-OmniscienceClaude Opus 5.5 by 38.946.47.5+38.9
- GDPval-AA 2.1Claude Opus 5.5 by 197 rating points18461649+197 rating
- Vals IndexClaude Opus 5.5 by 16.16750.9+16.1
- AA IntelligenceClaude Opus 5.5 by 15.857.641.8+15.8
- DeepSWE 1.1Claude Opus 5.5 by 10.874.263.4+10.8
- GDP (Surge AI)Claude Opus 5.5 by 10.826.215.4+10.8
- livebench_languageClaude Opus 5.5 by 986.377.3+9
- PostTrain Bench v1.2Claude Opus 5.5 by 743.836.8+7
- ARC-AGI-1Claude Opus 5.5 by 6.597.591+6.5
- OfficeQA ProClaude Opus 5.5 by 5.367.762.4+5.3
- livebench_data_analysisClaude Opus 5.5 by 3.980.376.4+3.9
Questions people ask
Which is better, Claude Opus 5.5 or GLM-5.3-Flash?
Claude Opus 5.5 wins all eight areas we test: coding, agents, reasoning, facts, images and charts, math, long documents and following instructions. GLM-5.3-Flash wins none, but costs 97% less.
Which is better for coding?
Claude Opus 5.5. It wins 4 of the 4 coding tests both models report; GLM-5.3-Flash wins none.
Which is cheaper?
Claude Opus 5.5 costs $4.00 per million input tokens and $20.00 per million output tokens; GLM-5.3-Flash costs $0.15 and $0.50. That makes GLM-5.3-Flash about 97% 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 21 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 14 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.