Model comparison
GPT-5.1-Codex vs Inkling
Inkling is the stronger model overall, scoring 44.1 to 38.6 on the Noometry Index.
Last verified . 3 shared benchmarks.
Summary
- They share 3 benchmarks with published results for both. GPT-5.1-Codex scores higher in 2 categories and Inkling in 1 category; 2 gaps are clear of the uncertainty.
- The widest gap is in agentic & tool use, where GPT-5.1-Codex leads 38.0 to 29.6.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 0% for Inkling.
- Inkling is cheaper at $1.87 / $4.68 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 66K.
- Inkling has downloadable open weights; the other is API-only.
Side by side
| GPT-5.1-Codex | Inkling | |
|---|---|---|
| Provider | OpenAI | Thinking Machines Lab |
| Noometry Index | 38.6 | 44.1 |
| Released | 2025-11-12 | 2026-07-15 |
| Weights | Proprietary | Open |
| Context window | 400K | 66K |
| Max output | 128K | 66K |
| Input $ / M tokens | $1.25 | $1.87 |
| Output $ / M tokens | $10 | $4.68 |
| Results tracked | 6 | 41 |
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Category by category
Coding GPT-5.1-Codex leads
GPT-5.1-Codex: 41.9 (#116), Inkling: 34.5 (#234)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| LMArena WebDev | 1337 | 1413 |
| ALE-Bench | 1,245 | 946 |
| FrontierCode | — | 14% |
| SWE-bench Verified (bash only) | 66% | — |
| FrontierSWE | — | 4.1% |
| SciCode | — | 47% |
| WeirdML | — | 32.3% |
| LMArena Coding | — | 1464 |
Agentic & Tool Use GPT-5.1-Codex leads
GPT-5.1-Codex: 38.0 (#33), Inkling: 29.6 (#85)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| APEX-Agents | — | 33.8% |
| τ²-bench Banking | — | 25% |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, Inkling: 40.4 (#56)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| ARC-AGI-2 | — | 36.5% |
| SimpleBench | — | 50% |
| ARC-AGI-1 | — | 79.5% |
| CritPt | — | 5.4% |
| Chess Puzzles | — | 21% |
| LMArena Hard Prompts | — | 1451 |
| DTBench | — | 87.5% |
| LMCA | — | 37.6% |
| Epoch Capabilities Index | — | 148.54 |
Math Too close to call
GPT-5.1-Codex: 30.3 (#235), Inkling: 31.3 (#225)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| ProofBench | 9% | 0% |
| FrontierMath (Tiers 1-3) | — | 33.3% |
| FrontierMath Tier 4 | — | 4.9% |
| OTIS Mock AIME 2024-2025 | — | 88.9% |
| LMArena Math | — | 1479 |
Knowledge Not comparable
GPT-5.1-Codex: —, Inkling: 55.1 (#49)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| GPQA Diamond | — | 88.3% |
| SimpleQA Verified | — | 40.3% |
| LMArena Expert | — | 1465 |
Multilingual Not comparable
GPT-5.1-Codex: —, Inkling: 54.0 (#52)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| LMArena Non-English | — | 1434 |
| LMArena Chinese | — | 1490 |
| LMArena French | — | 1458 |
| LMArena German | — | 1446 |
| LMArena Japanese | — | 1429 |
| LMArena Korean | — | 1404 |
| LMArena Russian | — | 1429 |
| LMArena Spanish | — | 1448 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Inkling: 75.1 (#71)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| LMArena Instruction Following | — | 1426 |
Long Context Not comparable
GPT-5.1-Codex: —, Inkling: 43.8 (#86)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| LMArena Longer Query | — | 1434 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Inkling: 65.2 (#51)
| Benchmark | GPT-5.1-Codex | Inkling |
|---|---|---|
| LMArena Text | — | 1441 |
| LMArena Creative Writing | — | 1387 |
| EQ-Bench Creative Writing | — | 1611 |
| EQ-Bench 4 | — | 1226 |
| LMArena Multi-Turn | — | 1436 |
Frequently asked questions
Is GPT-5.1-Codex better than Inkling?
Inkling is the stronger model overall, scoring 44.1 to 38.6 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or Inkling?
Inkling is cheaper. It lists at $1.87 per million input tokens and $4.68 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is GPT-5.1-Codex or Inkling better for coding?
GPT-5.1-Codex scores higher on coding benchmarks: 41.9 versus 34.5 in the Noometry coding category.
Which has the bigger context window?
GPT-5.1-Codex does, with 400K tokens against 66K.
How many benchmarks do GPT-5.1-Codex and Inkling share?
3 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Inkling has 41.