GPT-5.1-Codex-Mini vs Kimi K2.5
Updated October 21, 2026. 18 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick Kimi K2.5 for coding: it scores 58.5 on the Vibe Coding Index against 6.2 for GPT-5.1-Codex-Mini.
Pick GPT-5.1-Codex-Mini when output tokens cost 1.3x less, or when the context window is larger, 400K against 262K tokens.
- Shared results
- 18
- GPT-5.1-Codex-Mini only
- 4
- Kimi K2.5 only
- 80
- Like-for-like categories
- 6 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.
Coding
Vibe Coding Index, four public coding benchmarks
Kimi K2.5
Kimi K2.5 scores 58.5 against 6.2.
1 and 2 benchmarks behind the scores
Intelligence
AA Intelligence Index
Kimi K2.5
Kimi K2.5 leads, 23.5 against 20.4.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Kimi K2.5 has a GPQA Diamond result, 84.1%.
Directional only
Math
AIME
No call
Only Kimi K2.5 has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
No call
Only Kimi K2.5 has a MMLU Pro result, 85.9%.
Directional only
Web design
Design Arena: websites
Kimi K2.5
Kimi K2.5 leads, 1249 against 1111.
Same board, both measured
Long documents
Listed context window
GPT-5.1-Codex-Mini
GPT-5.1-Codex-Mini takes 400K tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.1-Codex-Mini
GPT-5.1-Codex-Mini $0.0013, Kimi K2.5 $0.0018 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Kimi K2.5 has the number, $0.24.
Directional only
At a glance
- Coding index
- GPT-5.1-Codex-Mini 6.2 from 1 benchmark, Kimi K2.5 58.5 from 2 benchmarks.
- Widest category
- Agentic work, 33.0 points apart on average over 1 shared benchmark.
- Widest single gap
- τ²-Bench Telecom: GPT-5.1-Codex-Mini 62.9% against Kimi K2.5 95.9%, 33.0 points apart on a 0 to 100 scale.
- Output price
- GPT-5.1-Codex-Mini $2.00 against Kimi K2.5 $2.50 per million output tokens, 1.3x apart.
- Context window
- GPT-5.1-Codex-Mini takes 400K tokens, Kimi K2.5 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-Mini | Bars | Kimi K2.5 | Ties |
|---|---|---|---|---|
| Coding | 1 | 3 | ||
| Intelligence | 0 | 1 | ||
| Agentic work | 0 | 1 | ||
| Reasoning | 0 | 2 | ||
| Web design | 0 | 8 | ||
| General | 0 | 2 | ||
| All shared boards | 1 | 17 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index13
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 70.8% | Only Kimi K2.5 measured |
| SWE-bench Multilingual | Not measured | 67.3% | Only Kimi K2.5 measured |
| LMArena WebDev | 1244 | 1437 | Kimi K2.5 |
| AA Coding Index | Not measured | 46.8 | Only Kimi K2.5 measured |
| LiveCodeBench (Vals AI) | Not measured | 83.9% | Only Kimi K2.5 measured |
| SWE-bench Verified (Vals AI) | Not measured | 70.0% | Only Kimi K2.5 measured |
| Vibe Code Bench (Vals AI) | Not measured | 17.5% | Only Kimi K2.5 measured |
| Code migration (Vals AI) | Not measured | 7.0% | Only Kimi K2.5 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 42.0% | Only Kimi K2.5 measured |
| LiveCodeBench (Artificial Analysis run) | 83.6% | Not measured | Only GPT-5.1-Codex-Mini measured |
| Terminal-Bench Hard (Artificial Analysis run) | 33.3% | 34.8% | Kimi K2.5 |
| Terminal-Bench | 61.6% | 43.2% | GPT-5.1-Codex-Mini |
| WeirdML | Not measured | 45.6% | Only Kimi K2.5 measured |
| ALE-Bench | Not measured | 821.6 | Only Kimi K2.5 measured |
| LMArena Text: coding | Not measured | 1483 | Only Kimi K2.5 measured |
| LMArena Text: software and IT | Not measured | 1471 | Only Kimi K2.5 measured |
| LMArena WebDev: React | Not measured | 1429 | Only Kimi K2.5 measured |
| LMArena WebDev: HTML | 1253 | 1426 | Kimi K2.5 |
| LMArena WebDev: from an image | Not measured | 1439 | Only Kimi K2.5 measured |
| Neither model has a result on the other 19 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.4 | 23.5 | Kimi K2.5 |
| Epoch Capabilities Index | Not measured | 148.1 | Only Kimi K2.5 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | Not measured | 1136 | Only Kimi K2.5 measured |
| Design Arena: agents building full-stack apps | Not measured | 1114 | Only Kimi K2.5 measured |
| Design Arena: agents building mobile apps | Not measured | 1147 | Only Kimi K2.5 measured |
| Design Arena: agents building Android apps | Not measured | 1124 | Only Kimi K2.5 measured |
| Design Arena: agents building Godot games | Not measured | 1219 | Only Kimi K2.5 measured |
| Finance Agent (Vals AI) | Not measured | 35.8% | Only Kimi K2.5 measured |
| Legal Research Bench (Vals AI) | Not measured | 15.9% | Only Kimi K2.5 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 28.5% | Only Kimi K2.5 measured |
| τ²-Bench Telecom | 62.9% | 95.9% | Kimi K2.5 |
| OSWorld | Not measured | 63.3% | Only Kimi K2.5 measured |
| Vending-Bench 2 | Not measured | $1,198 | Only Kimi K2.5 measured |
| Neither model has a result on the other 28 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 84.1% | Only Kimi K2.5 measured |
| MMMU Pro (Vals AI) | Not measured | 84.3% | Only Kimi K2.5 measured |
| GPQA Diamond (Artificial Analysis run) | 81.3% | 87.9% | Kimi K2.5 |
| Humanity's Last Exam (Artificial Analysis run) | 18.5% | 30.7% | Kimi K2.5 |
| ARC-AGI | Not measured | 65.3% | Only Kimi K2.5 measured |
| ARC-AGI-2 | Not measured | 11.8% | Only Kimi K2.5 measured |
| SimpleBench | Not measured | 46.8% | Only Kimi K2.5 measured |
| LMArena Text: hard prompts | Not measured | 1453 | Only Kimi K2.5 measured |
| LMArena Text: expert | Not measured | 1466 | Only Kimi K2.5 measured |
| LMArena Text: hard prompts in English | Not measured | 1460 | Only Kimi K2.5 measured |
| LMArena Vision: diagrams | Not measured | 1282 | Only Kimi K2.5 measured |
| LMArena Vision: homework | Not measured | 1297 | Only Kimi K2.5 measured |
| Neither model has a result on the other 9 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index5 boards, none shared
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| AIME | Not measured | 95.6% | Only Kimi K2.5 measured |
| AA Math Index | 91.7 | Not measured | Only GPT-5.1-Codex-Mini measured |
| AIME 2025 (Artificial Analysis run) | 91.7% | Not measured | Only GPT-5.1-Codex-Mini measured |
| LMArena Text: math | Not measured | 1470 | Only Kimi K2.5 measured |
| LMArena Text: mathematical work | Not measured | 1473 | Only Kimi K2.5 measured |
| Neither model has a result on the other 8 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index13 boards, none shared
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 85.9% | Only Kimi K2.5 measured |
| CaseLaw (Vals AI) | Not measured | 58.7% | Only Kimi K2.5 measured |
| CorpFin (Vals AI) | Not measured | 68.3% | Only Kimi K2.5 measured |
| TaxEval (Vals AI) | Not measured | 74.2% | Only Kimi K2.5 measured |
| MortgageTax (Vals AI) | Not measured | 66.5% | Only Kimi K2.5 measured |
| MedQA (Vals AI) | Not measured | 94.4% | Only Kimi K2.5 measured |
| MedCode (Vals AI) | Not measured | 39.3% | Only Kimi K2.5 measured |
| MMLU Pro (Artificial Analysis run) | 82.0% | Not measured | Only GPT-5.1-Codex-Mini measured |
| SimpleQA Verified | Not measured | 34.3% | Only Kimi K2.5 measured |
| LMArena Text: science | Not measured | 1459 | Only Kimi K2.5 measured |
| LMArena Text: medicine and healthcare | Not measured | 1448 | Only Kimi K2.5 measured |
| LMArena Text: legal and government | Not measured | 1441 | Only Kimi K2.5 measured |
| LMArena Text: business and finance | Not measured | 1427 | Only Kimi K2.5 measured |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index08
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1111 | 1249 | Kimi K2.5 |
| Design Arena: UI components | 1081 | 1236 | Kimi K2.5 |
| Design Arena: game dev | 1093 | 1207 | Kimi K2.5 |
| Design Arena: data viz | 1097 | 1219 | Kimi K2.5 |
| Design Arena: 3D | 988 | 1205 | Kimi K2.5 |
| Design Arena: all code categories | 1094 | 1236 | Kimi K2.5 |
| Design Arena: SVG | 977 | 1149 | Kimi K2.5 |
| Design Arena: ASCII art | 1104 | 1165 | Kimi K2.5 |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | Not measured | 49.9% | Only Kimi K2.5 measured |
| MedScribe (Vals AI) | Not measured | 76.4% | Only Kimi K2.5 measured |
| IFBench | 67.9% | 70.2% | Kimi K2.5 |
| Long context reasoning (AA-LCR) | 66.7% | 78.0% | Kimi K2.5 |
| Fiction.LiveBench | Not measured | 86.1% | Only Kimi K2.5 measured |
| CL-bench | Not measured | 19.3% | Only Kimi K2.5 measured |
| CL-bench Life | Not measured | 13.2% | Only Kimi K2.5 measured |
| LMArena Text | Not measured | 1445 | Only Kimi K2.5 measured |
| LMArena Text: instruction following | Not measured | 1431 | Only Kimi K2.5 measured |
| LMArena Text: creative writing | Not measured | 1422 | Only Kimi K2.5 measured |
| LMArena Vision | Not measured | 1269 | Only Kimi K2.5 measured |
| LMArena Text: English | Not measured | 1453 | Only Kimi K2.5 measured |
| LMArena Text: non-English | Not measured | 1433 | Only Kimi K2.5 measured |
| LMArena Text: Chinese | Not measured | 1494 | Only Kimi K2.5 measured |
| LMArena Text: German | Not measured | 1441 | Only Kimi K2.5 measured |
| LMArena Text: Japanese | Not measured | 1423 | Only Kimi K2.5 measured |
| LMArena Text: Korean | Not measured | 1412 | Only Kimi K2.5 measured |
| LMArena Text: French | Not measured | 1454 | Only Kimi K2.5 measured |
| LMArena Text: Spanish | Not measured | 1450 | Only Kimi K2.5 measured |
| LMArena Text: Russian | Not measured | 1435 | Only Kimi K2.5 measured |
| LMArena Text: Polish | Not measured | 1445 | Only Kimi K2.5 measured |
| LMArena Text: multi-turn | Not measured | 1444 | Only Kimi K2.5 measured |
| LMArena Text: longer queries | Not measured | 1445 | Only Kimi K2.5 measured |
| LMArena Text: writing and language | Not measured | 1425 | Only Kimi K2.5 measured |
| LMArena Text: entertainment and media | Not measured | 1417 | Only Kimi K2.5 measured |
| LMArena Vision: English | Not measured | 1274 | Only Kimi K2.5 measured |
| LMArena Vision: Chinese | Not measured | 1328 | Only Kimi K2.5 measured |
| LMArena Vision: reading text | Not measured | 1276 | Only Kimi K2.5 measured |
| LMArena Vision: humor | Not measured | 1284 | Only Kimi K2.5 measured |
| LMArena Vision: captioning | Not measured | 1257 | Only Kimi K2.5 measured |
| LMArena Vision: recognizing things | Not measured | 1285 | Only Kimi K2.5 measured |
| LMArena Vision: creative writing | Not measured | 1269 | Only Kimi K2.5 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5.1-Codex-Mini | Kimi K2.5 | 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
GPT-5.1-Codex-Mini costs less
Repository review
50K input + 3K output tokens
GPT-5.1-Codex-Mini costs less
Agent loop
200K input + 10K output tokens
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.
| Specification | OpenAI GPT-5.1-Codex-Mini | MoonshotAI Kimi K2.5 |
|---|---|---|
| Maker | OpenAI | Moonshot AI |
| Weights | No public weights listed | Open weights |
| Released | November 13, 2025 | January 27, 2026 |
| Context window | 400K | 262K |
| Input $/Mtok | $0.25 | $0.50 |
| Output $/Mtok | $2.00 | $2.50 |
| Coding index | 6.2 | 58.5 |
| Independent measurements behind it | 1 | 2 |
| Cost per solved task | Not computable | $0.24 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.1-Codex-Mini better than Kimi K2.5 for coding?
Pick Kimi K2.5 for coding: it scores 58.5 on the Vibe Coding Index against 6.2 for GPT-5.1-Codex-Mini. Pick GPT-5.1-Codex-Mini when output tokens cost 1.3x less, or when the context window is larger, 400K against 262K tokens.
Which is cheaper, GPT-5.1-Codex-Mini or Kimi K2.5?
GPT-5.1-Codex-Mini costs $0.25 per million input tokens and $2.00 per million output tokens; Kimi K2.5 costs $0.50 and $2.50. Cost per solved task is known for Kimi K2.5 only.
Which has the bigger context window, GPT-5.1-Codex-Mini or Kimi K2.5?
GPT-5.1-Codex-Mini, with 400K tokens against 262K.
How many benchmarks is the GPT-5.1-Codex-Mini vs Kimi K2.5 comparison based on?
18 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 K2.5's on 2. Where only one model has a result, the page says so instead of naming a winner.