GPT-5.1-Codex vs Kimi K2 Thinking
GPT-5.1-Codex leads Kimi K2 Thinking on the Artificial Analysis Intelligence Index, 23.7 to 22.0, and Kimi K2 Thinking costs 4.0x less per output token ($2.50 vs $10.00 per million). Updated October 22, 2026; 16 benchmarks have a result for both.
GPT-5.1-Codex or Kimi K2 Thinking: which to pick
Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; Kimi K2 Thinking has none, so the two cannot be ranked on coding.
Pick Kimi K2 Thinking for output tokens 4.0x cheaper ($2.50 vs $10.00 per million) and a lower cost per solved task ($0.61 against $0.892).
- Shared results
- 16
- GPT-5.1-Codex only
- 10
- Kimi K2 Thinking only
- 14
- Like-for-like categories
- 8 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.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Only GPT-5.1-Codex has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
GPT-5.1-Codex
GPT-5.1-Codex leads, 23.7 against 22.0.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Kimi K2 Thinking has a GPQA Diamond result, 78.5%.
Directional only
Math
AIME
No call
Only Kimi K2 Thinking has a AIME result, 85.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Kimi K2 Thinking has a MMLU Pro result, 81.1%.
Directional only
Web design
Design Arena: websites
GPT-5.1-Codex
GPT-5.1-Codex leads, 1161 against 1113.
Same board, both measured
Long documents
Listed context window
GPT-5.1-Codex
GPT-5.1-Codex takes 400K tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Kimi K2 Thinking
GPT-5.1-Codex $0.0063, Kimi K2 Thinking $0.0019 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Kimi K2 Thinking
GPT-5.1-Codex $0.892, Kimi K2 Thinking $0.61.
Published attempt cost and pass rate
At a glance
- Coding index
- GPT-5.1-Codex 15.3 from 2 benchmarks, Kimi K2 Thinking not benchmarked.
- Widest category
- Coding, 12.1 points apart on average over 6 shared benchmarks.
- Widest single gap
- LiveCodeBench (Vals AI): GPT-5.1-Codex 85.5% against Kimi K2 Thinking 63.1%, 22.4 points apart on a 0 to 100 scale.
- Output price
- GPT-5.1-Codex $10.00 against Kimi K2 Thinking $2.50 per million output tokens, 4.0x apart.
- Context window
- GPT-5.1-Codex takes 400K tokens, Kimi K2 Thinking 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.
| Category | GPT-5.1-Codex | Bars | Kimi K2 Thinking | Ties |
|---|---|---|---|---|
| Coding | 5 | 1 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 0 | 1 | ||
| Reasoning | 2 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 1 | 0 | ||
| Web design | 1 | 0 | ||
| General | 1 | 1 | ||
| All shared boards | 13 | 3 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index51
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| SWE-bench Verified | 66.0% | 63.4% | GPT-5.1-Codex |
| LMArena WebDev | 1337 | Not measured | Only GPT-5.1-Codex measured |
| LiveCodeBench (Vals AI) | 85.5% | 63.1% | GPT-5.1-Codex |
| SWE-bench Verified (Vals AI) | Not measured | 60.2% | Only Kimi K2 Thinking measured |
| Vibe Code Bench (Vals AI) | 13.1% | Not measured | Only GPT-5.1-Codex measured |
| LiveCodeBench (Artificial Analysis run) | 84.9% | 85.3% | Kimi K2 Thinking |
| Terminal-Bench Hard (Artificial Analysis run) | 34.8% | 31.1% | GPT-5.1-Codex |
| Terminal-Bench | 57.8% | 35.7% | GPT-5.1-Codex |
| WeirdML | Not measured | 42.8% | Only Kimi K2 Thinking measured |
| ALE-Bench | 1244.9 | 597.5 | GPT-5.1-Codex |
| LMArena WebDev: HTML | 1346 | Not measured | Only 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
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| AA Intelligence Index | 23.7 | 22.0 | GPT-5.1-Codex |
| Epoch Capabilities Index | Not measured | 145.8 | Only Kimi K2 Thinking measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1018 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building full-stack apps | 1086 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building mobile apps | 1191 | Not measured | Only GPT-5.1-Codex measured |
| τ²-Bench Telecom | 83.0% | 93.0% | Kimi K2 Thinking |
| METR time horizons | Not measured | 59.2% | Only Kimi K2 Thinking measured |
| Neither model has a result on the other 36 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 78.5% | Only Kimi K2 Thinking measured |
| GPQA Diamond (Artificial Analysis run) | 86.0% | 83.8% | GPT-5.1-Codex |
| Humanity's Last Exam (Artificial Analysis run) | 25.7% | 23.8% | 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
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| AIME | Not measured | 85.4% | Only Kimi K2 Thinking measured |
| MGSM (Vals AI) | Not measured | 90.2% | Only Kimi K2 Thinking measured |
| AA Math Index | 95.7 | 94.7 | GPT-5.1-Codex |
| AIME 2025 (Artificial Analysis run) | 95.7% | 94.7% | GPT-5.1-Codex |
| Neither model has a result on the other 9 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 81.1% | Only Kimi K2 Thinking measured |
| LegalBench (Vals AI) | Not measured | 80.2% | Only Kimi K2 Thinking measured |
| CaseLaw (Vals AI) | Not measured | 65.7% | Only Kimi K2 Thinking measured |
| CorpFin (Vals AI) | Not measured | 60.6% | Only Kimi K2 Thinking measured |
| TaxEval (Vals AI) | Not measured | 71.7% | Only Kimi K2 Thinking measured |
| MedQA (Vals AI) | Not measured | 92.6% | Only Kimi K2 Thinking measured |
| MMLU Pro (Artificial Analysis run) | 86.0% | 84.8% | GPT-5.1-Codex |
| Neither model has a result on the other 11 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| Design Arena: websites | 1161 | 1113 | GPT-5.1-Codex |
| Design Arena: UI components | 1234 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: game dev | 1137 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: data viz | 1213 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: all code categories | 1152 | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 4 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| IFBench | 70.0% | 68.1% | GPT-5.1-Codex |
| Long context reasoning (AA-LCR) | 69.3% | 72.0% | Kimi K2 Thinking |
| CL-bench | Not measured | 17.6% | Only Kimi K2 Thinking 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
| Benchmark | GPT-5.1-Codex | Kimi K2 Thinking | Leader |
|---|---|---|---|
| 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
Kimi K2 Thinking costs less
Repository review
50K input + 3K output tokens
Kimi K2 Thinking costs less
Agent loop
200K input + 10K output tokens
Kimi K2 Thinking 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.
| Specification | OpenAI GPT-5.1-Codex | MoonshotAI Kimi K2 Thinking |
|---|---|---|
| Maker | OpenAI | Moonshot AI |
| Weights | No public weights listed | Open weights |
| Released | November 13, 2025 | November 6, 2025 |
| Context window | 400K | 262K |
| Input $/Mtok | $1.25 | $0.60 |
| Output $/Mtok | $10.00 | $2.50 |
| Coding index | 15.3 | Not benchmarked |
| Independent measurements behind it | 2 | 1 |
| Cost per solved task | $0.892 | $0.61 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.1-Codex better than Kimi K2 Thinking for coding?
Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; Kimi K2 Thinking has none, so the two cannot be ranked on coding. Pick Kimi K2 Thinking for output tokens 4.0x cheaper ($2.50 vs $10.00 per million) and a lower cost per solved task ($0.61 against $0.892).
Which is cheaper, GPT-5.1-Codex or Kimi K2 Thinking?
GPT-5.1-Codex costs $1.25 per million input tokens and $10.00 per million output tokens; Kimi K2 Thinking costs $0.60 and $2.50. Per solved SWE-bench Verified task, GPT-5.1-Codex costs $0.892 and Kimi K2 Thinking $0.61.
Which has the bigger context window, GPT-5.1-Codex or Kimi K2 Thinking?
GPT-5.1-Codex, with 400K tokens against 262K.
How many benchmarks is the GPT-5.1-Codex vs Kimi K2 Thinking comparison based on?
16 benchmarks have a result for both models as of October 22, 2026. GPT-5.1-Codex's coding index rests on 2 independent benchmarks and Kimi K2 Thinking's on 1. Where only one model has a result, the page says so instead of naming a winner.