Model comparison
GPT-5.6 Sol vs Mercury 2
GPT-5.6 Sol is the stronger model overall, scoring 64.4 to 38.8 on the Noometry Index. Mercury 2 costs 21× less per token, which makes it the better buy when GPT-5.6 Sol's lead doesn't matter for your workload.
Last verified . 17 shared benchmarks.
Summary
- They share 17 benchmarks with published results for both. GPT-5.6 Sol scores higher in 7 categories and Mercury 2 in 0 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.6 Sol leads 74.7 to 23.0.
- The biggest single-benchmark swing is WeirdML: 89.4% for GPT-5.6 Sol and 43.2% for Mercury 2.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $4 / $20 for GPT-5.6 Sol.
- GPT-5.6 Sol accepts more context: 1.05M tokens versus 128K.
Side by side
| GPT-5.6 Sol | Mercury 2 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 64.4 | 38.8 |
| Released | 2026-07-09 | 2026-02-20 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 128K |
| Max output | 128K | 50K |
| Input $ / M tokens | $4 | $0.25 |
| Output $ / M tokens | $20 | $0.75 |
| Results tracked | 64 | 17 |
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Category by category
Coding GPT-5.6 Sol leads
GPT-5.6 Sol: 61.1 (#7), Mercury 2: 33.2 (#250)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena WebDev | 1619 | 1170 |
| SciCode | 57.1% | 38.7% |
| WeirdML | 89.4% | 43.2% |
| LMArena Coding | 1493 | 1391 |
| ALE-Bench | 2,177 | 785.58 |
| DeepSWE | 72.7% | — |
| FrontierCode | 47.5% | — |
| CursorBench | 41.7% | — |
| FrontierSWE | 32.2% | — |
| MirrorCode | 20% | — |
Agentic & Tool Use Not comparable
GPT-5.6 Sol: 50.2 (#7), Mercury 2: —
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| APEX-Agents | 51.4% | — |
| OSWorld 2.0 | 27.3% | — |
| τ²-bench Banking | 46.9% | — |
| PostTrainBench | 36.2% | — |
| BALROG | 60% | — |
| GBAEval | 52.6% | — |
| GDP.pdf | 30.7% | — |
| LMArena Search | 1257 | — |
| Vending-Bench 2 | 9,619 | — |
Reasoning GPT-5.6 Sol leads
GPT-5.6 Sol: 74.7 (#6), Mercury 2: 23.0 (#170)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| CritPt | 32.3% | 0.8% |
| LMArena Hard Prompts | 1481 | 1362 |
| ARC-AGI-2 | 92.5% | — |
| SimpleBench | 71.7% | — |
| Kagi LLM Benchmark | 67% | — |
| NYT Connections (extended) | 93.8% | — |
| ARC-AGI-1 | 97.5% | — |
| Chess Puzzles | 64% | — |
| EnigmaEval | 37.1% | — |
| EBR-Bench | 44.8% | — |
| Mystery Game Puzzles | 58% | — |
| DTBench | 96% | — |
| LMCA | 59.2% | — |
| Surface Evolver Bench | 93.1% | — |
| Bench to the Future 3 | 0.14 | — |
| Epoch Capabilities Index | 161.99 | — |
Math Not comparable
GPT-5.6 Sol: 85.5 (#7), Mercury 2: —
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 89.1% | — |
| FrontierMath Tier 4 | 82.9% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 83% | — |
| LMArena Math | 1472 | — |
| FrontierMath Erdős | 0% | — |
Knowledge GPT-5.6 Sol leads
GPT-5.6 Sol: 64.3 (#16), Mercury 2: 35.6 (#170)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| Vectara Hallucination Rate | 12.4% | 12.3% |
| LMArena Expert | 1517 | 1358 |
| GPQA Diamond | 93.5% | — |
| SimpleQA Verified | 69.7% | — |
Multimodal Not comparable
GPT-5.6 Sol: 48.9 (#8), Mercury 2: —
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena Vision | 1281 | — |
| Blueprint-Bench 2 | 33.6% | — |
| Furniture Assembly | 56.7% | — |
| LMArena Document | 1483 | — |
Multilingual GPT-5.6 Sol leads
GPT-5.6 Sol: 55.4 (#32), Mercury 2: 46.8 (#153)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena Non-English | 1450 | 1331 |
| LMArena Chinese | 1523 | 1416 |
| LMArena Russian | 1466 | 1303 |
| LMArena French | 1475 | — |
| LMArena German | 1476 | — |
| LMArena Japanese | 1475 | — |
| LMArena Korean | 1434 | — |
| LMArena Spanish | 1449 | — |
Instruction Following GPT-5.6 Sol leads
GPT-5.6 Sol: 77.8 (#16), Mercury 2: 70.4 (#161)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | 1480 | 1328 |
Long Context GPT-5.6 Sol leads
GPT-5.6 Sol: 45.3 (#42), Mercury 2: 40.4 (#149)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena Longer Query | 1479 | 1329 |
Writing & Preference GPT-5.6 Sol leads
GPT-5.6 Sol: 73.5 (#12), Mercury 2: 54.0 (#151)
| Benchmark | GPT-5.6 Sol | Mercury 2 |
|---|---|---|
| LMArena Text | 1456 | 1355 |
| LMArena Creative Writing | 1450 | 1289 |
| LMArena Multi-Turn | 1456 | 1358 |
| EQ-Bench Creative Writing | 1972 | — |
| EQ-Bench 4 | 1250 | — |
Frequently asked questions
Is GPT-5.6 Sol better than Mercury 2?
GPT-5.6 Sol is the stronger model overall, scoring 64.4 to 38.8 on the Noometry Index. Mercury 2 costs 21× less per token, which makes it the better buy when GPT-5.6 Sol's lead doesn't matter for your workload.
Which is cheaper, GPT-5.6 Sol or Mercury 2?
Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 per million output tokens; GPT-5.6 Sol lists at $4 and $20.
Is GPT-5.6 Sol or Mercury 2 better for coding?
GPT-5.6 Sol scores higher on coding benchmarks: 61.1 versus 33.2 in the Noometry coding category.
Which has the bigger context window?
GPT-5.6 Sol does, with 1.05M tokens against 128K.
How many benchmarks do GPT-5.6 Sol and Mercury 2 share?
17 benchmarks have published results for both models. GPT-5.6 Sol has 64 scored results on Noometry and Mercury 2 has 17.