Claude Sonnet 5 vs Mercury 2
Updated October 21, 2026. 39 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
vs boards won of 39 shared
Decision reading
Pick Claude Sonnet 5 for coding: it scores 63.5 on the Vibe Coding Index against 0.0 for Mercury 2.
Pick Mercury 2 when output tokens cost 13.3x less.
Model AClaude Sonnet 5Anthropic63.5/1002 independent benchmarks$1.87 per solved taskModel BMercury 2Inception0.0/1001 independent benchmarkNo cost per solved task
- Shared results
- 39
- Claude Sonnet 5 only
- 81
- Mercury 2 only
- 3
- Like-for-like categories
- 7 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
Claude Sonnet 5
Claude Sonnet 5 scores 63.5 against 0.0.
2 and 1 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Sonnet 5
Claude Sonnet 5 leads, 38.2 against 10.8.
Same board, both measured
Agentic work
AA Agentic Index
Claude Sonnet 5
Claude Sonnet 5 leads, 43.6 against 1.6.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 5 has a GPQA Diamond result, 88.9%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Sonnet 5 has a MMLU Pro result, 87.5%.
Directional only
Web design
Design Arena: websites
Claude Sonnet 5
Claude Sonnet 5 leads, 1274 against 1036.
Same board, both measured
Long documents
Listed context window
Claude Sonnet 5
Claude Sonnet 5 takes 1M tokens against 128K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 2
Claude Sonnet 5 $0.0070, Mercury 2 $0.0006 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Sonnet 5 has the number, $1.87.
Directional only
At a glance
- Coding index
- Claude Sonnet 5 63.5 from 2 benchmarks, Mercury 2 0.0 from 1 benchmark.
- Widest category
- Agentic work, 42.0 points apart on average over 1 shared benchmark.
- Widest single gap
- LMArena WebDev: React: Claude Sonnet 5 1541 against Mercury 2 1160, 63.6 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5 $10.00 against Mercury 2 $0.75 per million output tokens, 13.3x apart.
- Context window
- Claude Sonnet 5 takes 1M tokens, Mercury 2 128K.
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 | Claude Sonnet 5 | Bars | Mercury 2 | Ties |
|---|---|---|---|---|
| Coding | 9 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 1 | 0 | ||
| Reasoning | 5 | 0 | ||
| Knowledge | 3 | 0 | ||
| Web design | 8 | 0 | ||
| General | 12 | 0 | ||
| All shared boards | 39 | 0 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index90
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| LiveBench coding | 74.7% | Not measured | Only Claude Sonnet 5 measured |
| LMArena WebDev | 1540 | 1171 | Claude Sonnet 5 |
| AA Coding Index | 71.5 | 31.1 | Claude Sonnet 5 |
| LiveCodeBench (Vals AI) | 82.4% | Not measured | Only Claude Sonnet 5 measured |
| SWE-bench Verified (Vals AI) | 79.6% | Not measured | Only Claude Sonnet 5 measured |
| Terminal-Bench 4 (Vals AI) | 10.6% | Not measured | Only Claude Sonnet 5 measured |
| Vibe Code Bench (Vals AI) | 81.3% | Not measured | Only Claude Sonnet 5 measured |
| Code migration (Vals AI) | 44.4% | Not measured | Only Claude Sonnet 5 measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only Claude Sonnet 5 measured |
| IOI (Vals AI) | 45.0% | Not measured | Only Claude Sonnet 5 measured |
| Terminal-Bench 2.1 (Vals AI) | 74.5% | Not measured | Only Claude Sonnet 5 measured |
| Vibe Code Bench 1-100 (Vals AI) | 13.8% | Not measured | Only Claude Sonnet 5 measured |
| SkillsBench (Vals AI) | 46.5% | Not measured | Only Claude Sonnet 5 measured |
| CyberBench (Vals AI) | 70.3% | Not measured | Only Claude Sonnet 5 measured |
| SciCode | 54.3% | 37.7% | Claude Sonnet 5 |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 26.5% | Only Mercury 2 measured |
| FrontierCode | 42.7% | Not measured | Only Claude Sonnet 5 measured |
| GSO-Bench | 37.3% | Not measured | Only Claude Sonnet 5 measured |
| WeirdML | 68.8% | 43.2% | Claude Sonnet 5 |
| ALE-Bench | 1463.1 | 785.6 | Claude Sonnet 5 |
| LMArena Text: coding | 1483 | 1390 | Claude Sonnet 5 |
| LMArena Text: software and IT | 1474 | 1385 | Claude Sonnet 5 |
| LMArena WebDev: React | 1541 | 1160 | Claude Sonnet 5 |
| LMArena WebDev: HTML | 1527 | 1199 | Claude Sonnet 5 |
| LMArena WebDev: from an image | 1540 | Not measured | Only Claude Sonnet 5 measured |
| Neither model has a result on the other 13 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| AA Intelligence Index | 38.2 | 10.8 | Claude Sonnet 5 |
| Epoch Capabilities Index | 156.9 | Not measured | Only Claude Sonnet 5 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| AA Agentic Index | 43.6 | 1.6 | Claude Sonnet 5 |
| Design Arena: agents building web apps | 1245 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: agents building full-stack apps | 1249 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: agents building mobile apps | 1215 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: agents building Android apps | 1231 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: agents building Godot games | 1225 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: agents building games | 1227 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: HTML slides | 1218 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: PowerPoint slides | 1216 | Not measured | Only Claude Sonnet 5 measured |
| Design Arena: spreadsheets | 1004 | Not measured | Only Claude Sonnet 5 measured |
| LiveBench research | 82.8% | Not measured | Only Claude Sonnet 5 measured |
| LiveBench browser | 72.0% | Not measured | Only Claude Sonnet 5 measured |
| LiveBench long agentic | 39.0% | Not measured | Only Claude Sonnet 5 measured |
| SREBench (Vals AI) | 0.4% | Not measured | Only Claude Sonnet 5 measured |
| Finance Agent (Vals AI) | 53.9% | Not measured | Only Claude Sonnet 5 measured |
| Tax Agent Bench (Vals AI) | 29.4% | Not measured | Only Claude Sonnet 5 measured |
| Legal Research Bench (Vals AI) | 41.8% | Not measured | Only Claude Sonnet 5 measured |
| Excel Modeling Benchmark (Vals AI) | 66.3% | Not measured | Only Claude Sonnet 5 measured |
| Terminal-Bench-Science (Vals AI) | 5.7% | Not measured | Only Claude Sonnet 5 measured |
| τ²-Bench Telecom | Not measured | 70.8% | Only Mercury 2 measured |
| APEX-Agents | 54.5% | Not measured | Only Claude Sonnet 5 measured |
| Vending-Bench 2 | $6,378 | Not measured | Only Claude Sonnet 5 measured |
| Neither model has a result on the other 17 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| GPQA Diamond | 88.9% | Not measured | Only Claude Sonnet 5 measured |
| LiveBench reasoning | 88.7% | Not measured | Only Claude Sonnet 5 measured |
| MMMU Pro (Vals AI) | 83.0% | Not measured | Only Claude Sonnet 5 measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | 77.0% | Claude Sonnet 5 |
| Humanity's Last Exam (Artificial Analysis run) | 41.3% | 17.1% | Claude Sonnet 5 |
| GPQA Diamond (Epoch AI run) | 90.5% | Not measured | Only Claude Sonnet 5 measured |
| SimpleBench | 60.6% | Not measured | Only Claude Sonnet 5 measured |
| Chess puzzles | 45.0% | Not measured | Only Claude Sonnet 5 measured |
| Mystery game puzzles | 35.0% | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: hard prompts | 1461 | 1362 | Claude Sonnet 5 |
| LMArena Text: expert | 1489 | 1358 | Claude Sonnet 5 |
| LMArena Text: hard prompts in English | 1464 | 1374 | Claude Sonnet 5 |
| LMArena Vision: diagrams | 1293 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Vision: homework | 1311 | Not measured | Only Claude Sonnet 5 measured |
| Neither model has a result on the other 7 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| OTIS Mock AIME | 94.7% | Not measured | Only Claude Sonnet 5 measured |
| FrontierMath, tiers 1 to 3 | 65.6% | Not measured | Only Claude Sonnet 5 measured |
| FrontierMath, tier 4 | 29.3% | Not measured | Only Claude Sonnet 5 measured |
| ProofBench | 77.0% | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: math | 1467 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: mathematical work | 1481 | Not measured | Only Claude Sonnet 5 measured |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| MMLU Pro | 87.5% | Not measured | Only Claude Sonnet 5 measured |
| LegalBench (Vals AI) | 83.9% | Not measured | Only Claude Sonnet 5 measured |
| CorpFin (Vals AI) | 67.0% | Not measured | Only Claude Sonnet 5 measured |
| TaxEval (Vals AI) | 75.6% | Not measured | Only Claude Sonnet 5 measured |
| MortgageTax (Vals AI) | 70.0% | Not measured | Only Claude Sonnet 5 measured |
| MedCode (Vals AI) | 47.5% | Not measured | Only Claude Sonnet 5 measured |
| SimpleQA Verified | 33.7% | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: science | 1460 | 1343 | Claude Sonnet 5 |
| LMArena Text: medicine and healthcare | 1442 | 1363 | Claude Sonnet 5 |
| LMArena Text: legal and government | 1454 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: business and finance | 1436 | 1349 | Claude Sonnet 5 |
| Neither model has a result on the other 6 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index80
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| Design Arena: websites | 1274 | 1036 | Claude Sonnet 5 |
| Design Arena: UI components | 1279 | 998 | Claude Sonnet 5 |
| Design Arena: game dev | 1278 | 985 | Claude Sonnet 5 |
| Design Arena: data viz | 1251 | 1009 | Claude Sonnet 5 |
| Design Arena: 3D | 1261 | 982 | Claude Sonnet 5 |
| Design Arena: all code categories | 1276 | 1022 | Claude Sonnet 5 |
| Design Arena: SVG | 1193 | 998 | Claude Sonnet 5 |
| Design Arena: ASCII art | 1207 | 990 | Claude Sonnet 5 |
| LiveBench design | 82.0% | Not measured | Only Claude Sonnet 5 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index120
| Benchmark | Claude Sonnet 5 | Mercury 2 | Leader |
|---|---|---|---|
| LiveBench data analysis | 71.7% | Not measured | Only Claude Sonnet 5 measured |
| Public Benefits Bench (Vals AI) | 66.0% | Not measured | Only Claude Sonnet 5 measured |
| SAGE (Vals AI) | 48.9% | Not measured | Only Claude Sonnet 5 measured |
| MedScribe (Vals AI) | 76.0% | Not measured | Only Claude Sonnet 5 measured |
| Vals Multimodal Index | 68.8% | Not measured | Only Claude Sonnet 5 measured |
| IFBench | Not measured | 69.8% | Only Mercury 2 measured |
| Long context reasoning (AA-LCR) | 82.0% | 43.7% | Claude Sonnet 5 |
| DTBench | 92.5% | Not measured | Only Claude Sonnet 5 measured |
| LMCA | 50.0% | Not measured | Only Claude Sonnet 5 measured |
| Surface Evolver Bench | 60.0% | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text | 1442 | 1354 | Claude Sonnet 5 |
| LMArena Text: instruction following | 1452 | 1328 | Claude Sonnet 5 |
| LMArena Text: creative writing | 1416 | 1286 | Claude Sonnet 5 |
| LMArena Vision | 1273 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: English | 1450 | 1378 | Claude Sonnet 5 |
| LMArena Text: non-English | 1431 | 1330 | Claude Sonnet 5 |
| LMArena Text: Chinese | 1478 | 1414 | Claude Sonnet 5 |
| LMArena Text: German | 1442 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: Japanese | 1422 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: Korean | 1412 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: French | 1463 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: Spanish | 1438 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: Russian | 1450 | 1304 | Claude Sonnet 5 |
| LMArena Text: Polish | 1425 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Text: multi-turn | 1453 | 1357 | Claude Sonnet 5 |
| LMArena Text: longer queries | 1462 | 1329 | Claude Sonnet 5 |
| LMArena Text: writing and language | 1436 | 1300 | Claude Sonnet 5 |
| LMArena Text: entertainment and media | 1411 | 1314 | Claude Sonnet 5 |
| LMArena Vision: English | 1275 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Vision: Chinese | 1331 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Vision: reading text | 1288 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Vision: humor | 1261 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Vision: creative writing | 1246 | Not measured | Only Claude Sonnet 5 measured |
| LMArena Document | 1466 | Not measured | Only Claude Sonnet 5 measured |
| Neither model has a result on the other 12 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5 | Mercury 2 | 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
Claude Sonnet 5$0.0070Fits in one request
Mercury 2$0.0006Fits in one request
Mercury 2 costs less
Repository review
50K input + 3K output tokens
Claude Sonnet 5$0.130Fits in one request
Mercury 2$0.015Fits in one request
Mercury 2 costs less
Agent loop
200K input + 10K output tokens
Claude Sonnet 5$0.500Fits in one request
Mercury 2$0.058Exceeds the context window
Mercury 2 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 | Anthropic Claude Sonnet 5 | Inception Mercury 2 |
|---|---|---|
| Maker | Anthropic | Inception |
| Weights | No public weights listed | No public weights listed |
| Released | June 30, 2026 | March 4, 2026 |
| Context window | 1M | 128K |
| Input $/Mtok | $2.00 | $0.25 |
| Output $/Mtok | $10.00 | $0.75 |
| Coding index | 63.5 | 0.0 |
| Independent measurements behind it | 2 | 1 |
| Cost per solved task | $1.87 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5 better than Mercury 2 for coding?
Pick Claude Sonnet 5 for coding: it scores 63.5 on the Vibe Coding Index against 0.0 for Mercury 2. Pick Mercury 2 when output tokens cost 13.3x less.
Which is cheaper, Claude Sonnet 5 or Mercury 2?
Claude Sonnet 5 costs $2.00 per million input tokens and $10.00 per million output tokens; Mercury 2 costs $0.25 and $0.75. Cost per solved task is known for Claude Sonnet 5 only.
Which has the bigger context window, Claude Sonnet 5 or Mercury 2?
Claude Sonnet 5, with 1M tokens against 128K.
How many benchmarks is the Claude Sonnet 5 vs Mercury 2 comparison based on?
39 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5's coding index rests on 2 independent benchmarks and Mercury 2's on 1. Where only one model has a result, the page says so instead of naming a winner.