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gpt-oss-120b vs Mercury 2

Updated October 21, 2026. 37 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace gpt-oss-120b Replace Mercury 2
gpt-oss-120bOpenAI
Coding
34.5
Overall
11.6
Output $/M
$0.60
16
Mercury 2Inception
Coding
0.0
Overall
10.8
Output $/M
$0.75
21
vs boards won of 37 shared

Decision reading

Pick gpt-oss-120b for coding: it scores 34.5 on the Vibe Coding Index against 0.0 for Mercury 2.

Pick Mercury 2 when what matters is AA Coding Index or SciCode, where it leads.

Model Agpt-oss-120bOpenAI34.5/1002 independent benchmarks$0.51 per solved taskModel BMercury 2Inception0.0/1001 independent benchmarkNo cost per solved task
Shared results
37
gpt-oss-120b only
41
Mercury 2 only
5
Like-for-like categories
7 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

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
gpt-oss-120b 34.5 from 2 benchmarks, Mercury 2 0.0 from 1 benchmark.
Widest category
Web design, 6.4 points apart on average over 6 shared benchmarks.
Widest single gap
Design Arena: 3D: gpt-oss-120b 901 against Mercury 2 982, 10.1 points apart on a 0 to 100 scale.
Output price
gpt-oss-120b $0.60 against Mercury 2 $0.75 per million output tokens, 1.3x apart.
Context window
gpt-oss-120b takes 131K tokens, Mercury 2 128K.

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
Categorygpt-oss-120bBarsMercury 2Ties
Coding25
Intelligence10
Agentic work11
Reasoning32
Knowledge30
Web design15
General58
All shared boards1621
CodingLike-for-likeFour of these boards feed the Vibe Coding Index25
Coding benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
Aider polyglot41.8%Not measuredOnly gpt-oss-120b measured
SWE-bench Verified26.0%Not measuredOnly gpt-oss-120b measured
LMArena WebDevNot measured1171Only Mercury 2 measured
AA Coding Index30.431.1Mercury 2
LiveCodeBench (Vals AI)83.2%Not measuredOnly gpt-oss-120b measured
SWE-bench Verified (Vals AI)33.6%Not measuredOnly gpt-oss-120b measured
LiveCodeBench (Artificial Analysis run)87.8%Not measuredOnly gpt-oss-120b measured
SciCode34.0%37.7%Mercury 2
Terminal-Bench Hard (Artificial Analysis run)23.5%26.5%Mercury 2
Terminal-Bench18.7%Not measuredOnly gpt-oss-120b measured
WeirdML48.2%43.2%gpt-oss-120b
ALE-Bench575.6785.6Mercury 2
LMArena Text: coding13791390Mercury 2
LMArena Text: software and IT13871385gpt-oss-120b
LMArena WebDev: ReactNot measured1160Only Mercury 2 measured
LMArena WebDev: HTMLNot measured1199Only Mercury 2 measured
Neither model has a result on the other 22 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
AA Intelligence Index11.610.8gpt-oss-120b
Epoch Capabilities Index139.8Not measuredOnly gpt-oss-120b measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index11
Agentic work benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
AA Agentic Index3.71.6gpt-oss-120b
τ²-Bench Telecom65.8%70.8%Mercury 2
APEX-Agents4.4%Not measuredOnly gpt-oss-120b measured
METR time horizons56.6%Not measuredOnly gpt-oss-120b measured
Vending-Bench 2-$22Not measuredOnly gpt-oss-120b measured
Neither model has a result on the other 34 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index32
Reasoning benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
GPQA Diamond78.5%Not measuredOnly gpt-oss-120b measured
GPQA Diamond (Artificial Analysis run)78.2%77.0%gpt-oss-120b
Humanity's Last Exam (Artificial Analysis run)19.6%17.1%gpt-oss-120b
GPQA Diamond (Epoch AI run)75.8%Not measuredOnly gpt-oss-120b measured
SimpleBench22.1%Not measuredOnly gpt-oss-120b measured
Mystery game puzzles2.0%Not measuredOnly gpt-oss-120b measured
LMArena Text: hard prompts13641362gpt-oss-120b
LMArena Text: expert13561358Mercury 2
LMArena Text: hard prompts in English13681374Mercury 2
Neither model has a result on the other 12 boards here
MathDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
Math benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
AIME92.6%Not measuredOnly gpt-oss-120b measured
MATH 500 (Vals AI)94.8%Not measuredOnly gpt-oss-120b measured
MGSM (Vals AI)92.0%Not measuredOnly gpt-oss-120b measured
AA Math Index93.4Not measuredOnly gpt-oss-120b measured
AIME 2025 (Artificial Analysis run)93.4%Not measuredOnly gpt-oss-120b measured
OTIS Mock AIME88.9%Not measuredOnly gpt-oss-120b measured
LMArena Text: math1389Not measuredOnly gpt-oss-120b measured
LMArena Text: mathematical work1386Not measuredOnly gpt-oss-120b measured
Neither model has a result on the other 5 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index30
Knowledge benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
MMLU Pro79.2%Not measuredOnly gpt-oss-120b measured
LegalBench (Vals AI)75.9%Not measuredOnly gpt-oss-120b measured
CaseLaw (Vals AI)48.8%Not measuredOnly gpt-oss-120b measured
CorpFin (Vals AI)58.2%Not measuredOnly gpt-oss-120b measured
TaxEval (Vals AI)71.6%Not measuredOnly gpt-oss-120b measured
MedQA (Vals AI)91.4%Not measuredOnly gpt-oss-120b measured
MMLU Pro (Artificial Analysis run)80.8%Not measuredOnly gpt-oss-120b measured
LMArena Text: science13821343gpt-oss-120b
LMArena Text: medicine and healthcare13881363gpt-oss-120b
LMArena Text: legal and government1355Not measuredOnly gpt-oss-120b measured
LMArena Text: business and finance13591349gpt-oss-120b
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index15
Web design benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
Design Arena: websites9681036Mercury 2
Design Arena: UI components927998Mercury 2
Design Arena: game dev992985gpt-oss-120b
Design Arena: data viz9871009Mercury 2
Design Arena: 3D901982Mercury 2
Design Arena: all code categories9631022Mercury 2
Design Arena: SVGNot measured998Only Mercury 2 measured
Design Arena: ASCII artNot measured990Only Mercury 2 measured
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index58
General benchmarks for gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
IFBench69.0%69.8%Mercury 2
Long context reasoning (AA-LCR)52.0%43.7%gpt-oss-120b
DTBench76.3%Not measuredOnly gpt-oss-120b measured
LMCA22.1%Not measuredOnly gpt-oss-120b measured
Fiction.LiveBench44.4%Not measuredOnly gpt-oss-120b measured
Creative writing (Lech Mazur)77.1%Not measuredOnly gpt-oss-120b measured
Surface Evolver Bench25.0%Not measuredOnly gpt-oss-120b measured
LMArena Text13661354gpt-oss-120b
LMArena Text: instruction following13181328Mercury 2
LMArena Text: creative writing12741286Mercury 2
LMArena Text: English13751378Mercury 2
LMArena Text: non-English13511330gpt-oss-120b
LMArena Text: Chinese13851414Mercury 2
LMArena Text: German1353Not measuredOnly gpt-oss-120b measured
LMArena Text: Japanese1331Not measuredOnly gpt-oss-120b measured
LMArena Text: Korean1282Not measuredOnly gpt-oss-120b measured
LMArena Text: French1370Not measuredOnly gpt-oss-120b measured
LMArena Text: Spanish1389Not measuredOnly gpt-oss-120b measured
LMArena Text: Russian13431304gpt-oss-120b
LMArena Text: Polish1353Not measuredOnly gpt-oss-120b measured
LMArena Text: multi-turn13401357Mercury 2
LMArena Text: longer queries13191329Mercury 2
LMArena Text: writing and language13061300gpt-oss-120b
LMArena Text: entertainment and media12921314Mercury 2
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 gpt-oss-120b and Mercury 2
Benchmarkgpt-oss-120bMercury 2Leader
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

gpt-oss-120b$0.0004Fits in one request
Mercury 2$0.0006Fits in one request

gpt-oss-120b costs less

Repository review

50K input + 3K output tokens

gpt-oss-120b$0.0093Fits in one request
Mercury 2$0.015Fits in one request

gpt-oss-120b costs less

Agent loop

200K input + 10K output tokens

gpt-oss-120b$0.036Exceeds the context window
Mercury 2$0.058Exceeds the context window

gpt-oss-120b 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 gpt-oss-120b and Mercury 2
SpecificationOpenAI gpt-oss-120bInception Mercury 2
MakerOpenAIInception
WeightsOpen weightsNo public weights listed
ReleasedAugust 5, 2025March 4, 2026
Context window131K128K
Input $/Mtok$0.15$0.25
Output $/Mtok$0.60$0.75
Coding index34.50.0
Independent measurements behind it21
Cost per solved task$0.51Not computable
SourceOpenRouter listingOpenRouter listing

Questions

Is gpt-oss-120b better than Mercury 2 for coding?

Pick gpt-oss-120b for coding: it scores 34.5 on the Vibe Coding Index against 0.0 for Mercury 2. Pick Mercury 2 when what matters is AA Coding Index or SciCode, where it leads.

Which is cheaper, gpt-oss-120b or Mercury 2?

gpt-oss-120b costs $0.15 per million input tokens and $0.60 per million output tokens; Mercury 2 costs $0.25 and $0.75. Cost per solved task is known for gpt-oss-120b only.

Which has the bigger context window, gpt-oss-120b or Mercury 2?

gpt-oss-120b, with 131K tokens against 128K.

How many benchmarks is the gpt-oss-120b vs Mercury 2 comparison based on?

37 benchmarks have a result for both models as of October 21, 2026. gpt-oss-120b's coding index rests on 2 independent benchmarks and Mercury 2's on 1. Where only one model has a result, the page says so instead of naming a winner.

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