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Claude Sonnet 4.5 vs gpt-oss-20b

Claude Sonnet 4.5 leads gpt-oss-20b on the Artificial Analysis Intelligence Index, 20.7 to 10.0, and gpt-oss-20b costs 100.0x less per output token ($0.15 vs $15.00 per million). Updated October 22, 2026; 48 benchmarks have a result for both.

Replace Claude Sonnet 4.5 Replace gpt-oss-20b
Claude Sonnet 4.5Anthropic
Coding
39.5
Overall
49.5
Output $/M
$15.00
47
gpt-oss-20bOpenAI
Coding
No data
Overall
38.5
Output $/M
$0.15
1
vs boards won of 48 shared

Claude Sonnet 4.5 or gpt-oss-20b: which to pick

Only Claude Sonnet 4.5 has a coding score, 39.5 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding.

Pick gpt-oss-20b for output tokens 100.0x cheaper ($0.15 vs $15.00 per million) and work measured by LiveCodeBench (Vals AI), where it leads.

Model AClaude Sonnet 4.5Anthropic39.5/1003 independent benchmarks$1.16 per solved taskModel Bgpt-oss-20bOpenAINot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
48
Claude Sonnet 4.5 only
47
gpt-oss-20b only
14
Like-for-like categories
7 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
Claude Sonnet 4.5 39.5 from 3 benchmarks, gpt-oss-20b not benchmarked.
Widest category
Web design, 35.7 points apart on average over 2 shared benchmarks.
Widest single gap
Terminal-Bench: Claude Sonnet 4.5 46.5% against gpt-oss-20b 3.4%, 43.1 points apart on a 0 to 100 scale.
Output price
Claude Sonnet 4.5 $15.00 against gpt-oss-20b $0.15 per million output tokens, 100.0x apart.
Context window
Claude Sonnet 4.5 takes 1M tokens, gpt-oss-20b 131K.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryClaude Sonnet 4.5Barsgpt-oss-20bTies
Coding41
Intelligence20
Reasoning60
Math50
Knowledge100
Web design20
General180
All shared boards471
CodingLike-for-likeSix of these boards feed the Vibe Coding Index41
Coding benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
SWE-bench Verified74.8%Not measuredOnly Claude Sonnet 4.5 measured
SWE-bench Multilingual67.0%Not measuredOnly Claude Sonnet 4.5 measured
LMArena WebDev1394Not measuredOnly Claude Sonnet 4.5 measured
AA Coding Index52.1Not measuredOnly Claude Sonnet 4.5 measured
LiveCodeBench (Vals AI)73.0%80.4%gpt-oss-20b
SWE-bench Verified (Vals AI)70.0%Not measuredOnly Claude Sonnet 4.5 measured
Vibe Code Bench (Vals AI)22.6%Not measuredOnly Claude Sonnet 4.5 measured
LiveCodeBench (Artificial Analysis run)Not measured77.7%Only gpt-oss-20b measured
SciCodeNot measured38.9%Only gpt-oss-20b measured
Terminal-Bench Hard (Artificial Analysis run)Not measured10.6%Only gpt-oss-20b measured
Terminal-Bench46.5%3.4%Claude Sonnet 4.5
GSO-Bench14.7%Not measuredOnly Claude Sonnet 4.5 measured
WeirdML47.7%40.9%Claude Sonnet 4.5
Cybench60.0%Not measuredOnly Claude Sonnet 4.5 measured
ALE-BenchNot measured566.0Only gpt-oss-20b measured
LMArena Text: coding14881307Claude Sonnet 4.5
LMArena Text: software and IT14731311Claude Sonnet 4.5
LMArena WebDev: React1386Not measuredOnly Claude Sonnet 4.5 measured
LMArena WebDev: HTML1399Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 20 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
AA Intelligence Index20.710.0Claude Sonnet 4.5
Epoch Capabilities Index146.7137.7Claude Sonnet 4.5
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index13 boards, none shared
Agentic work benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
AA Agentic Index15.8Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: agents building web apps1060Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: agents building full-stack apps1050Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: agents building mobile apps1137Not measuredOnly Claude Sonnet 4.5 measured
τ²-Bench TelecomNot measured60.2%Only gpt-oss-20b measured
METR time horizons67.4%Not measuredOnly Claude Sonnet 4.5 measured
Remote Labor Index2.1%Not measuredOnly Claude Sonnet 4.5 measured
GDPval42.5%Not measuredOnly Claude Sonnet 4.5 measured
DeepResearch Bench52.6%Not measuredOnly Claude Sonnet 4.5 measured
OSWorld62.9%Not measuredOnly Claude Sonnet 4.5 measured
Vending-Bench 2$3,839Not measuredOnly Claude Sonnet 4.5 measured
Berkeley Function Calling Leaderboard (BFCL)73.2%Not measuredOnly Claude Sonnet 4.5 measured
BrowseComp-PlusNot measured50.6%Only gpt-oss-20b measured
Neither model has a result on the other 28 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index60
Reasoning benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
GPQA Diamond81.6%68.9%Claude Sonnet 4.5
MMMU Pro (Vals AI)79.3%Not measuredOnly Claude Sonnet 4.5 measured
GPQA Diamond (Artificial Analysis run)Not measured68.8%Only gpt-oss-20b measured
Humanity's Last Exam (Artificial Analysis run)Not measured11.0%Only gpt-oss-20b measured
GPQA Diamond (Epoch AI run)82.3%60.8%Claude Sonnet 4.5
ARC-AGI63.7%Not measuredOnly Claude Sonnet 4.5 measured
ARC-AGI-213.6%Not measuredOnly Claude Sonnet 4.5 measured
SimpleBench54.3%Not measuredOnly Claude Sonnet 4.5 measured
Chess puzzles10.0%Not measuredOnly Claude Sonnet 4.5 measured
Mystery game puzzles17.0%Not measuredOnly Claude Sonnet 4.5 measured
EBR-bench2.4%Not measuredOnly Claude Sonnet 4.5 measured
VPCT39.8%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: hard prompts14621274Claude Sonnet 4.5
LMArena Text: expert14831258Claude Sonnet 4.5
LMArena Text: hard prompts in English14711292Claude Sonnet 4.5
Kagi LLM Benchmark57.9%53.2%Claude Sonnet 4.5
Neither model has a result on the other 6 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index50
Math benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
AIME88.2%86.0%Claude Sonnet 4.5
MATH 500 (Vals AI)Not measured94.2%Only gpt-oss-20b measured
MGSM (Vals AI)94.3%89.0%Claude Sonnet 4.5
AA Math IndexNot measured89.3Only gpt-oss-20b measured
AIME 2025 (Artificial Analysis run)Not measured89.3%Only gpt-oss-20b measured
OTIS Mock AIME77.8%65.3%Claude Sonnet 4.5
FrontierMath, tiers 1 to 323.9%Not measuredOnly Claude Sonnet 4.5 measured
FrontierMath, tier 42.4%Not measuredOnly Claude Sonnet 4.5 measured
ProofBench19.0%Not measuredOnly Claude Sonnet 4.5 measured
MATH level 597.7%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: math14491317Claude Sonnet 4.5
LMArena Text: mathematical work14621305Claude Sonnet 4.5
Neither model has a result on the other 1 board here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100
Knowledge benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
MMLU Pro87.4%71.6%Claude Sonnet 4.5
LegalBench (Vals AI)84.1%70.8%Claude Sonnet 4.5
CaseLaw (Vals AI)62.2%43.8%Claude Sonnet 4.5
CorpFin (Vals AI)62.0%53.1%Claude Sonnet 4.5
TaxEval (Vals AI)73.3%63.7%Claude Sonnet 4.5
MortgageTax (Vals AI)64.0%Not measuredOnly Claude Sonnet 4.5 measured
MedQA (Vals AI)94.7%82.9%Claude Sonnet 4.5
MedCode (Vals AI)44.1%Not measuredOnly Claude Sonnet 4.5 measured
MMLU Pro (Artificial Analysis run)Not measured74.8%Only gpt-oss-20b measured
SimpleQA Verified30.7%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: science14481296Claude Sonnet 4.5
LMArena Text: medicine and healthcare14441310Claude Sonnet 4.5
LMArena Text: legal and government14511280Claude Sonnet 4.5
LMArena Text: business and finance14401284Claude Sonnet 4.5
FACTS Benchmark Suite40.6%Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 3 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index20
Web design benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
Design Arena: websites1189852Claude Sonnet 4.5
Design Arena: UI components1170Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: game dev1166Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: data viz1167933Claude Sonnet 4.5
Design Arena: 3D1157Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: all code categories1182Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: SVG1115Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: ASCII art1205Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index180
General benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
SAGE (Vals AI)36.1%Not measuredOnly Claude Sonnet 4.5 measured
MedScribe (Vals AI)84.5%Not measuredOnly Claude Sonnet 4.5 measured
IFBenchNot measured65.1%Only gpt-oss-20b measured
Long context reasoning (AA-LCR)Not measured34.7%Only gpt-oss-20b measured
DTBench83.2%68.0%Claude Sonnet 4.5
LMCA38.8%14.5%Claude Sonnet 4.5
LMArena Text14381288Claude Sonnet 4.5
LMArena Text: instruction following14591236Claude Sonnet 4.5
LMArena Text: creative writing14421201Claude Sonnet 4.5
LMArena Text: English14501303Claude Sonnet 4.5
LMArena Text: non-English14251269Claude Sonnet 4.5
LMArena Text: Chinese14601315Claude Sonnet 4.5
LMArena Text: German14271255Claude Sonnet 4.5
LMArena Text: Japanese13901244Claude Sonnet 4.5
LMArena Text: Korean14021236Claude Sonnet 4.5
LMArena Text: French1459Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Spanish14581267Claude Sonnet 4.5
LMArena Text: Russian14371278Claude Sonnet 4.5
LMArena Text: Polish14231252Claude Sonnet 4.5
LMArena Text: multi-turn14651268Claude Sonnet 4.5
LMArena Text: longer queries14751250Claude Sonnet 4.5
LMArena Text: writing and language14421238Claude Sonnet 4.5
LMArena Text: entertainment and media14281216Claude Sonnet 4.5
LMArena Document1450Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 22 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Claude Sonnet 4.5 and gpt-oss-20b
BenchmarkClaude Sonnet 4.5gpt-oss-20bLeader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Claude Sonnet 4.5$0.011Fits in one request
gpt-oss-20b$0.0001Fits in one request

gpt-oss-20b costs less

Repository review

50K input + 3K output tokens

Claude Sonnet 4.5$0.195Fits in one request
gpt-oss-20b$0.0019Fits in one request

gpt-oss-20b costs less

Agent loop

200K input + 10K output tokens

Claude Sonnet 4.5$0.750Fits in one request
gpt-oss-20b$0.0075Exceeds the context window

gpt-oss-20b costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Claude Sonnet 4.5 and gpt-oss-20b
SpecificationAnthropic Claude Sonnet 4.5OpenAI gpt-oss-20b
MakerAnthropicOpenAI
WeightsNo public weights listedOpen weights
ReleasedSeptember 29, 2025August 5, 2025
Context window1M131K
Input $/Mtok$3.00$0.03
Output $/Mtok$15.00$0.15
Coding index39.5Not benchmarked
Independent measurements behind it30
Cost per solved task$1.16Not computable
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Sonnet 4.5 better than gpt-oss-20b for coding?

Only Claude Sonnet 4.5 has a coding score, 39.5 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding. Pick gpt-oss-20b for output tokens 100.0x cheaper ($0.15 vs $15.00 per million) and work measured by LiveCodeBench (Vals AI), where it leads.

Which is cheaper, Claude Sonnet 4.5 or gpt-oss-20b?

Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; gpt-oss-20b costs $0.03 and $0.15. Cost per solved task is known for Claude Sonnet 4.5 only.

Which has the bigger context window, Claude Sonnet 4.5 or gpt-oss-20b?

Claude Sonnet 4.5, with 1M tokens against 131K.

How many benchmarks is the Claude Sonnet 4.5 vs gpt-oss-20b comparison based on?

48 benchmarks have a result for both models as of October 22, 2026. Claude Sonnet 4.5's coding index rests on 3 independent benchmarks and gpt-oss-20b's on 0. Where only one model has a result, the page says so instead of naming a winner.

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