GPT-6 Astra vs Claude Sonnet 5.5
Wins 4 of 8 areas
Reasoning · Facts · Math · Following instructions
Wins 3 of 8 areas
Coding · Agents · Long documents
GPT-6 Astra wins more areas, narrowly.Claude Sonnet 5.5 is cheaper and better at agents.
Both rank among the ten best models we track in math.
Scores updated · 29 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 thinking20GPT-6 Astra2 of 4 tests · 2 ties
- MathCompetition and research-level math20GPT-6 Astra2 of 3 tests · 1 tie
- FactsGetting facts right instead of making them up21GPT-6 Astra2 of 3 tests
- Following instructionsDoing exactly what it is asked10GPT-6 Astra1 of 1 test
- AgentsCarrying out multi-step tasks on its own02Claude Sonnet 5.52 of 2 tests
- CodingWriting and fixing software12Claude Sonnet 5.52 of 4 tests · 1 tie
- Long documentsFinding answers in very long texts01Claude Sonnet 5.51 of 1 test
- Images and chartsUnderstanding pictures, charts and video00Even0 each · 1 tie
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.
Claude Sonnet 5.5 costs 80% less for the same work.
The biggest differences
The three tests each model wins by the widest margin. Scores are out of 100.
Where GPT-6 Astra pulls ahead
- Short factual questions, answered correctlySimpleQA Verified+29.1points ahead
- Follows detailed instructions exactlyLiveBench · Instruction Following+18.8points ahead
- Extremely hard research-level math problemsFrontierMath Tier 4+17.1points ahead
Where Claude Sonnet 5.5 pulls ahead
- Real work tasks from 44 professionsGDPVal+13.3points ahead
- Programming problems, refreshed regularlyLiveBench · Coding+11points ahead
- Code for real scientific research problemsSciCode+4.5points ahead
Every test, side by side
All 29 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Sonnet 5.5
- LiveBench · CodingClaude Sonnet 5.5 by 1180.491.4+11
- SciCodeClaude Sonnet 5.5 by 4.556.561+4.5
- LiveBench · Agentic CodingGPT-6 Astra by 157.356.3+1
- LMArena · WebDevtie17771768tie
AgentsClaude Sonnet 5.5
- GDPValClaude Sonnet 5.5 by 13.353.666.9+13.3
- Terminal-Bench 4.0Claude Sonnet 5.5 by 4.559.163.6+4.5
ReasoningGPT-6 Astra
- SimpleBenchGPT-6 Astra by 7.783.675.9+7.7
- LiveBench · ReasoningGPT-6 Astra by 1.192.791.6+1.1
- CritPttie31.731.4tie
- Humanity's Last Examtie54.755tie
FactsGPT-6 Astra
- SimpleQA VerifiedGPT-6 Astra by 29.175.646.5+29.1
- AA-Omniscience · AccuracyGPT-6 Astra by 8.662.654+8.6
- AA-Omniscience · Non-hallucinationClaude Sonnet 5.5 by 4.348.753+4.3
MathGPT-6 Astra
- FrontierMath Tier 4GPT-6 Astra by 17.197.680.5+17.1
- FrontierMath Tiers 1-3 (v2)GPT-6 Astra by 4.993.788.8+4.9
- LiveBench · Mathematicstie96.896.1tie
Following instructionsGPT-6 Astra
- LiveBench · Instruction FollowingGPT-6 Astra by 18.875.656.8+18.8
Other results10 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.
- GDPval-AA 2.1Claude Sonnet 5.5 by 302 rating points15421844+302 rating
- livebench_data_analysisGPT-6 Astra by 23.58359.5+23.5
- Terminal-Bench 4.0Claude Sonnet 5.5 by 12.957.770.6+12.9
- livebench_languageGPT-6 Astra by 11.489.478+11.4
- AA-OmniscienceGPT-6 Astra by 11.143.432.3+11.1
- HealthBench ProfessionalClaude Sonnet 5.5 by 5.863.469.2+5.8
- Terminal-Bench-Science 0.1GPT-6 Astra by 4.764.659.9+4.7
- HealthBench Professional length-adjustedClaude Sonnet 5.5 by 4.564.769.2+4.5
- AA IntelligenceClaude Sonnet 5.5 by 3.352.756+3.3
- DeepSWE 1.1GPT-6 Astra by 3.174.171+3.1
Questions people ask
Which is better, GPT-6 Astra or Claude Sonnet 5.5?
GPT-6 Astra wins four of the eight areas we test: reasoning, facts, math and following instructions. Claude Sonnet 5.5 wins coding, agents and long documents, and costs 80% less. They are level on images and charts.
Which is better for coding?
Claude Sonnet 5.5. It wins 2 of the 4 coding tests both models report; GPT-6 Astra wins 1, and 1 is a tie.
Which is cheaper?
GPT-6 Astra costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Sonnet 5.5 costs $2.00 and $10.00. That makes Claude Sonnet 5.5 about 80% cheaper for the same work.
How do you compare the two?
We use the 29 benchmark tests both models have published scores on. The verdict counts the 19 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 10 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.