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GPT-5.1-Codex vs Kimi K2 0905

Updated October 21, 2026. 14 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 Replace Kimi K2 0905
GPT-5.1-CodexOpenAI
Coding
15.3
Overall
23.7
Output $/M
$10.00
14
Kimi K2 0905Moonshot AI
Coding
No data
Overall
15.3
Output $/M
$2.50
0
vs boards won of 14 shared

Decision reading

Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; Kimi K2 0905 has none, so the two cannot be ranked on coding.

Kimi K2 0905 has the edge where output tokens cost 4.0x less.

Model AGPT-5.1-CodexOpenAI15.3/1002 independent benchmarks$0.892 per solved taskModel BKimi K2 0905Moonshot AINot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
14
GPT-5.1-Codex only
12
Kimi K2 0905 only
2
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 15.3 from 2 benchmarks, Kimi K2 0905 not benchmarked.
Widest category
Math, 38.4 points apart on average over 2 shared benchmarks.
Widest single gap
AA Math Index: GPT-5.1-Codex 95.7 against Kimi K2 0905 57.3, 38.4 points apart on a 0 to 100 scale.
Output price
GPT-5.1-Codex $10.00 against Kimi K2 0905 $2.50 per million output tokens, 4.0x apart.
Context window
GPT-5.1-Codex 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-CodexBarsKimi K2 0905Ties
Coding30
Intelligence10
Agentic work10
Reasoning20
Math20
Knowledge10
Web design20
General20
All shared boards140
CodingLike-for-likeSix of these boards feed the Vibe Coding Index30
Coding benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
SWE-bench Verified66.0%Not measuredOnly GPT-5.1-Codex measured
LMArena WebDev1337Not measuredOnly GPT-5.1-Codex measured
LiveCodeBench (Vals AI)85.5%Not measuredOnly GPT-5.1-Codex measured
Vibe Code Bench (Vals AI)13.1%Not measuredOnly GPT-5.1-Codex measured
LiveCodeBench (Artificial Analysis run)84.9%61.0%GPT-5.1-Codex
Terminal-Bench Hard (Artificial Analysis run)34.8%23.5%GPT-5.1-Codex
Terminal-Bench57.8%Not measuredOnly GPT-5.1-Codex measured
WeirdMLNot measured36.7%Only Kimi K2 0905 measured
ALE-Bench1244.9267.1GPT-5.1-Codex
LMArena WebDev: HTML1346Not measuredOnly GPT-5.1-Codex measured
Neither model has a result on the other 28 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
AA Intelligence Index23.715.3GPT-5.1-Codex
Neither model has a result on the other 1 board here
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
Agentic work benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
Design Arena: agents building web apps1018Not measuredOnly GPT-5.1-Codex measured
Design Arena: agents building full-stack apps1086Not measuredOnly GPT-5.1-Codex measured
Design Arena: agents building mobile apps1191Not measuredOnly GPT-5.1-Codex measured
τ²-Bench Telecom83.0%73.4%GPT-5.1-Codex
Neither model has a result on the other 35 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index20
Reasoning benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
GPQA Diamond (Artificial Analysis run)86.0%76.7%GPT-5.1-Codex
Humanity's Last Exam (Artificial Analysis run)25.7%6.4%GPT-5.1-Codex
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 and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
AA Math Index95.757.3GPT-5.1-Codex
AIME 2025 (Artificial Analysis run)95.7%57.3%GPT-5.1-Codex
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 and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
MMLU Pro (Artificial Analysis run)86.0%81.9%GPT-5.1-Codex
Neither model has a result on the other 16 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index20
Web design benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
Design Arena: websites11621089GPT-5.1-Codex
Design Arena: UI components1237Not measuredOnly GPT-5.1-Codex measured
Design Arena: game dev1138Not measuredOnly GPT-5.1-Codex measured
Design Arena: data viz1213Not measuredOnly GPT-5.1-Codex measured
Design Arena: all code categories11521098GPT-5.1-Codex
Neither model has a result on the other 4 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index20
General benchmarks for GPT-5.1-Codex and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi K2 0905Leader
IFBench70.0%41.7%GPT-5.1-Codex
Long context reasoning (AA-LCR)69.3%53.0%GPT-5.1-Codex
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 and Kimi K2 0905
BenchmarkGPT-5.1-CodexKimi 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$0.0063Fits in one request
Kimi K2 0905$0.0019Fits in one request

Kimi K2 0905 costs less

Repository review

50K input + 3K output tokens

GPT-5.1-Codex$0.092Fits in one request
Kimi K2 0905$0.037Fits in one request

Kimi K2 0905 costs less

Agent loop

200K input + 10K output tokens

GPT-5.1-Codex$0.350Fits in one request
Kimi K2 0905$0.145Fits in one request

Kimi K2 0905 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 and Kimi K2 0905
SpecificationOpenAI GPT-5.1-CodexMoonshotAI Kimi K2 0905
MakerOpenAIMoonshot AI
WeightsNo public weights listedOpen weights
ReleasedNovember 13, 2025September 4, 2025
Context window400K262K
Input $/Mtok$1.25$0.60
Output $/Mtok$10.00$2.50
Coding index15.3Not benchmarked
Independent measurements behind it20
Cost per solved task$0.892Not computable
SourceOpenRouter listingOpenRouter listing

Questions

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

Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; Kimi K2 0905 has none, so the two cannot be ranked on coding. Kimi K2 0905 has the edge where output tokens cost 4.0x less.

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

GPT-5.1-Codex costs $1.25 per million input tokens and $10.00 per million output tokens; Kimi K2 0905 costs $0.60 and $2.50. Cost per solved task is known for GPT-5.1-Codex only.

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

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

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

14 benchmarks have a result for both models as of October 21, 2026. GPT-5.1-Codex's coding index rests on 2 independent benchmarks 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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