# GPT-5.1-Codex vs GPT-5.6 Terra

> GPT-5.6 Terra is the stronger model overall, scoring 59.2 to 38.6 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-gpt-5-6-terra
- Last updated: 2026-10-10
- Shared benchmarks: 3

## Summary

- They share 3 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and GPT-5.6 Terra in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.6 Terra leads 81.6 to 30.3.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 74% for GPT-5.6 Terra.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $2 / $12 for GPT-5.6 Terra.
- GPT-5.6 Terra accepts more context: 1.05M tokens versus 400K.

## Snapshot

| | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.6 | 59.2 |
| Rank | 186 | 17 |
| Context | 400K | 1.05M |
| Input $/M | $1.25 | $2 |
| Output $/M | $10 | $12 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.9 (#116)
- GPT-5.6 Terra: 57.7 (#19)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena WebDev | 1337 | 1522 |
| ALE-Bench | 1,245 | 1,951 |
| DeepSWE | — | 69.6% |
| FrontierCode | — | 41.3% |
| SWE-bench Verified (bash only) | 66% | — |
| CursorBench | — | 41.3% |
| SciCode | — | 55% |
| WeirdML | — | 78.3% |
| LMArena Coding | — | 1484 |

## Agentic & Tool Use

- GPT-5.1-Codex: 38.0 (#33)
- GPT-5.6 Terra: 40.1 (#25)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| APEX-Agents | — | 58.2% |
| BALROG | — | 53.2% |
| GDP.pdf | — | 24.7% |
| METR Time Horizons | 70.8% | — |
| Vending-Bench 2 | — | 7,343 |

## Reasoning

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 60.7 (#21)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| ARC-AGI-2 | — | 83.9% |
| SimpleBench | — | 48.9% |
| Kagi LLM Benchmark | — | 51.3% |
| NYT Connections (extended) | — | 78.4% |
| ARC-AGI-1 | — | 96.5% |
| CritPt | — | 30% |
| Chess Puzzles | — | 54% |
| LMArena Hard Prompts | — | 1468 |
| Mystery Game Puzzles | — | 35% |
| DTBench | — | 93.3% |
| LMCA | — | 55% |
| Surface Evolver Bench | — | 83.8% |
| Epoch Capabilities Index | — | 159.62 |

## Math

- GPT-5.1-Codex: 30.3 (#235)
- GPT-5.6 Terra: 81.6 (#12)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| ProofBench | 9% | 74% |
| FrontierMath (Tiers 1-3) | — | 86% |
| FrontierMath Tier 4 | — | 70.7% |
| OTIS Mock AIME 2024-2025 | — | 99.7% |
| LMArena Math | — | 1466 |

## Knowledge

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 61.2 (#30)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| GPQA Diamond | — | 93.3% |
| SimpleQA Verified | — | 43.2% |
| LMArena Expert | — | 1492 |

## Multimodal

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 47.3 (#11)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena Vision | — | 1271 |
| Blueprint-Bench 2 | — | 30.8% |
| Furniture Assembly | — | 54.2% |
| LMArena Document | — | 1472 |

## Multilingual

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 54.4 (#44)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena Non-English | — | 1439 |
| LMArena Chinese | — | 1513 |
| LMArena French | — | 1471 |
| LMArena German | — | 1460 |
| LMArena Japanese | — | 1457 |
| LMArena Korean | — | 1425 |
| LMArena Russian | — | 1450 |
| LMArena Spanish | — | 1448 |

## Instruction Following

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 76.4 (#40)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena Instruction Following | — | 1454 |

## Long Context

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 44.4 (#68)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena Longer Query | — | 1451 |

## Writing & Preference

- GPT-5.1-Codex: —
- GPT-5.6 Terra: 70.2 (#23)

| Benchmark | GPT-5.1-Codex | GPT-5.6 Terra |
|---|---|---|
| LMArena Text | — | 1447 |
| LMArena Creative Writing | — | 1410 |
| EQ-Bench Creative Writing | — | 1855 |
| EQ-Bench 4 | — | 1234 |
| LMArena Multi-Turn | — | 1449 |

## FAQ

### Is GPT-5.1-Codex better than GPT-5.6 Terra?

GPT-5.6 Terra is the stronger model overall, scoring 59.2 to 38.6 on the Noometry Index.

### Which is cheaper, GPT-5.1-Codex or GPT-5.6 Terra?

GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.6 Terra lists at $2 and $12.

### Is GPT-5.1-Codex or GPT-5.6 Terra better for coding?

GPT-5.6 Terra scores higher on coding benchmarks: 57.7 versus 41.9 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.6 Terra does, with 1.05M tokens against 400K.

### How many benchmarks do GPT-5.1-Codex and GPT-5.6 Terra share?

3 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-5.6 Terra has 52.