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GPT-5.1-Codex-Mini vs Kimi K2 0905

Updated October 21, 2026. 13 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-5.1-Codex-Mini Replace Kimi K2 0905
GPT-5.1-Codex-MiniOpenAI
Coding
No data
Overall
20.4
Output $/M
$2.00
11
Kimi K2 0905Moonshot AI
Coding
No data
Overall
15.3
Output $/M
$2.50
2
vs boards won of 13 shared

Decision reading

Neither model has a coding score yet, so the two cannot be ranked on coding.

GPT-5.1-Codex-Mini has the edge where output tokens cost 1.3x less, and where the context window is larger, 400K against 262K tokens.

Model AGPT-5.1-Codex-MiniOpenAINot benchmarked1 independent benchmarkNo cost per solved taskModel BKimi K2 0905Moonshot AINot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
13
GPT-5.1-Codex-Mini only
9
Kimi K2 0905 only
3
Like-for-like categories
8 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-5.1-Codex-Mini not benchmarked, Kimi K2 0905 not benchmarked.
Widest category
Math, 34.4 points apart on average over 2 shared benchmarks.
Widest single gap
AA Math Index: GPT-5.1-Codex-Mini 91.7 against Kimi K2 0905 57.3, 34.4 points apart on a 0 to 100 scale.
Output price
GPT-5.1-Codex-Mini $2.00 against Kimi K2 0905 $2.50 per million output tokens, 1.3x apart.
Context window
GPT-5.1-Codex-Mini takes 400K tokens, Kimi K2 0905 262K.

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-5.1-Codex-MiniBarsKimi K2 0905Ties
Coding20
Intelligence10
Agentic work01
Reasoning20
Math20
Knowledge10
Web design11
General20
All shared boards112
CodingLike-for-likeSix of these boards feed the Vibe Coding Index20
Coding benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
LMArena WebDev1244Not measuredOnly GPT-5.1-Codex-Mini measured
LiveCodeBench (Artificial Analysis run)83.6%61.0%GPT-5.1-Codex-Mini
Terminal-Bench Hard (Artificial Analysis run)33.3%23.5%GPT-5.1-Codex-Mini
Terminal-Bench61.6%Not measuredOnly GPT-5.1-Codex-Mini measured
WeirdMLNot measured36.7%Only Kimi K2 0905 measured
ALE-BenchNot measured267.1Only Kimi K2 0905 measured
LMArena WebDev: HTML1253Not measuredOnly GPT-5.1-Codex-Mini measured
Neither model has a result on the other 31 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
AA Intelligence Index20.415.3GPT-5.1-Codex-Mini
Neither model has a result on the other 1 board here
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
τ²-Bench Telecom62.9%73.4%Kimi K2 0905
Neither model has a result on the other 38 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index20
Reasoning benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
GPQA Diamond (Artificial Analysis run)81.3%76.7%GPT-5.1-Codex-Mini
Humanity's Last Exam (Artificial Analysis run)18.5%6.4%GPT-5.1-Codex-Mini
Neither model has a result on the other 19 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index20
Math benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
AA Math Index91.757.3GPT-5.1-Codex-Mini
AIME 2025 (Artificial Analysis run)91.7%57.3%GPT-5.1-Codex-Mini
Neither model has a result on the other 11 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index10
Knowledge benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
MMLU Pro (Artificial Analysis run)82.0%81.9%GPT-5.1-Codex-Mini
Neither model has a result on the other 16 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index11
Web design benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
Design Arena: websites11111089GPT-5.1-Codex-Mini
Design Arena: UI components1081Not measuredOnly GPT-5.1-Codex-Mini measured
Design Arena: game dev1092Not measuredOnly GPT-5.1-Codex-Mini measured
Design Arena: data viz1096Not measuredOnly GPT-5.1-Codex-Mini measured
Design Arena: 3D988Not measuredOnly GPT-5.1-Codex-Mini measured
Design Arena: all code categories10941098Kimi K2 0905
Design Arena: SVG978Not measuredOnly GPT-5.1-Codex-Mini measured
Design Arena: ASCII art1104Not measuredOnly GPT-5.1-Codex-Mini measured
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index20
General benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
IFBench67.9%41.7%GPT-5.1-Codex-Mini
Long context reasoning (AA-LCR)66.7%53.0%GPT-5.1-Codex-Mini
Fiction.LiveBenchNot measured66.7%Only Kimi K2 0905 measured
Neither model has a result on the other 43 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-5.1-Codex-Mini and Kimi K2 0905
BenchmarkGPT-5.1-Codex-MiniKimi K2 0905Leader
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-5.1-Codex-Mini$0.0013Fits in one request
Kimi K2 0905$0.0019Fits in one request

GPT-5.1-Codex-Mini costs less

Repository review

50K input + 3K output tokens

GPT-5.1-Codex-Mini$0.018Fits in one request
Kimi K2 0905$0.037Fits in one request

GPT-5.1-Codex-Mini costs less

Agent loop

200K input + 10K output tokens

GPT-5.1-Codex-Mini$0.070Fits in one request
Kimi K2 0905$0.145Fits in one request

GPT-5.1-Codex-Mini 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-5.1-Codex-Mini and Kimi K2 0905
SpecificationOpenAI GPT-5.1-Codex-MiniMoonshotAI Kimi K2 0905
MakerOpenAIMoonshot AI
WeightsNo public weights listedOpen weights
ReleasedNovember 13, 2025September 4, 2025
Context window400K262K
Input $/Mtok$0.25$0.60
Output $/Mtok$2.00$2.50
Coding indexNot benchmarkedNot benchmarked
Independent measurements behind it10
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-5.1-Codex-Mini better than Kimi K2 0905 for coding?

Neither model has a coding score yet, so the two cannot be ranked on coding. GPT-5.1-Codex-Mini has the edge where output tokens cost 1.3x less, and where the context window is larger, 400K against 262K tokens.

Which is cheaper, GPT-5.1-Codex-Mini or Kimi K2 0905?

GPT-5.1-Codex-Mini costs $0.25 per million input tokens and $2.00 per million output tokens; Kimi K2 0905 costs $0.60 and $2.50. Cost per solved task is known for neither of them.

Which has the bigger context window, GPT-5.1-Codex-Mini or Kimi K2 0905?

GPT-5.1-Codex-Mini, with 400K tokens against 262K.

How many benchmarks is the GPT-5.1-Codex-Mini vs Kimi K2 0905 comparison based on?

13 benchmarks have a result for both models as of October 21, 2026. GPT-5.1-Codex-Mini's coding index rests on 1 independent benchmark and Kimi K2 0905's on 0. Where only one model has a result, the page says so instead of naming a winner.

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