Claude Sonnet 4.5 vs gpt-oss-20b
Wins 5 of 6 areas
Coding · Agents · Reasoning · Facts · Long documents
Wins 1 of 6 areas
Following instructions
Claude Sonnet 4.5 is the stronger all-rounder.gpt-oss-20b is cheaper and better at following instructions.
Scores updated · 34 tests both models report · How we compare
Where each one wins
Tests won in each of the six 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.
- CodingWriting and fixing software60Claude Sonnet 4.56 of 6 tests
- ReasoningHard problems that need careful thinking20Claude Sonnet 4.52 of 3 tests · 1 tie
- FactsGetting facts right instead of making them up20Claude Sonnet 4.52 of 2 tests
- AgentsCarrying out multi-step tasks on its own21Claude Sonnet 4.52 of 4 tests · 1 tie
- Long documentsFinding answers in very long texts10Claude Sonnet 4.51 of 1 test
- Following instructionsDoing exactly what it is asked01gpt-oss-20b1 of 1 test
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.
gpt-oss-20b costs 99% 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 4.5 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+45points ahead
- Command-line tasks in a real terminalTerminal-Bench 2.1+41.9points ahead
- Reasons across sets of long documentsAA-LCR+37.6points ahead
Where gpt-oss-20b pulls ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+7.8points ahead
- Finds hard-to-locate facts by browsing the webBrowseComp+4.2points ahead
Every test, side by side
All 34 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Sonnet 4.5
- Terminal-Bench 2.1Claude Sonnet 4.5 by 41.955.813.9+41.9
- SWE-bench MultilingualClaude Sonnet 4.5 by 25.16741.9+25.1
- Terminal-Bench HardClaude Sonnet 4.5 by 2535.610.6+25
- SWE-bench VerifiedClaude Sonnet 4.5 by 24.877.252.4+24.8
- SciCodeClaude Sonnet 4.5 by 6.845.738.9+6.8
- LiveCodeBench v6Claude Sonnet 4.5 by 36461+3
AgentsClaude Sonnet 4.5
- GDPValClaude Sonnet 4.5 by 20.520.50+20.5
- τ-Bench V3 · BankingClaude Sonnet 4.5 by 17.524.57+17.5
- BrowseCompgpt-oss-20b by 4.224.128.3+4.2
- Terminal-Bench 4.0tie00tie
ReasoningClaude Sonnet 4.5
- GPQA DiamondClaude Sonnet 4.5 by 14.683.468.8+14.6
- Humanity's Last ExamClaude Sonnet 4.5 by 6.817.811+6.8
- CritPttie1.11.4tie
FactsClaude Sonnet 4.5
- AA-Omniscience · Non-hallucinationClaude Sonnet 4.5 by 4550.95.9+45
- AA-Omniscience · AccuracyClaude Sonnet 4.5 by 16.932.916+16.9
Long documentsClaude Sonnet 4.5
- AA-LCRClaude Sonnet 4.5 by 37.672.334.7+37.6
Following instructionsgpt-oss-20b
- IFBenchgpt-oss-20b by 7.857.365.1+7.8
Other results17 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 Sonnet 4.5 by 62.9-0.1-63+62.9
- τ²-BenchClaude Sonnet 4.5 by 50.39847.7+50.3
- Artificial Analysis Coding IndexClaude Sonnet 4.5 by 31.452.120.7+31.4
- TAU-bench (retail)Claude Sonnet 4.5 by 31.486.254.8+31.4
- τ²-Bench Telecom (AA run)Claude Sonnet 4.5 by 17.978.160.2+17.9
- GPQA (unspecified)Claude Sonnet 4.5 by 11.983.471.5+11.9
- AA IntelligenceClaude Sonnet 4.5 by 11.720.79+11.7
- MMLU-ProClaude Sonnet 4.5 by 11.187.576.4+11.1
- HMMT Feb. 2025gpt-oss-20b by 9.267.576.7+9.2
- XSTestClaude Sonnet 4.5 by 9.296.487.2+9.2
- HarmBenchgpt-oss-20b by 6.79298.7+6.7
- AIR-Bench 2024Claude Sonnet 4.5 by 3.889.886+3.8
- AIME 2025gpt-oss-20b by 2.28789.2+2.2
- bbqClaude Sonnet 4.5 by 2.298.996.7+2.2
- HealthBenchClaude Sonnet 4.5 by 1.744.242.5+1.7
- anthropic_red_teamgpt-oss-20b by 1.598.299.7+1.5
- simple_safety_teststie100100tie
Questions people ask
Which is better, Claude Sonnet 4.5 or gpt-oss-20b?
Claude Sonnet 4.5 wins five of the six areas where both have results: coding, agents, reasoning, facts and long documents. gpt-oss-20b wins following instructions, and costs 99% less.
Which is better for coding?
Claude Sonnet 4.5. It wins 6 of the 6 coding tests both models report; gpt-oss-20b wins none.
Which is cheaper?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; gpt-oss-20b costs $0.07 and $0.18. That makes gpt-oss-20b about 99% cheaper for the same work.
How do you compare the two?
We use the 34 benchmark tests both models have published scores on. The verdict counts the 17 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 17 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.