Claude Sonnet 4.5 vs Mercury 2.5
Claude Sonnet 4.5 leads Mercury 2.5 on coding, 39.5 to 1.6 on the Vibe Coding Index, and Mercury 2.5 costs 100.0x less per output token ($0.15 vs $15.00 per million). Updated October 22, 2026; 6 benchmarks have a result for both.
Claude Sonnet 4.5 or Mercury 2.5: which to pick
Pick Claude Sonnet 4.5 for coding: it scores 39.5 on the Vibe Coding Index against 1.6 for Mercury 2.5.
Pick Mercury 2.5 for output tokens 100.0x cheaper ($0.15 vs $15.00 per million).
- Shared results
- 6
- Claude Sonnet 4.5 only
- 89
- Mercury 2.5 only
- 16
- Like-for-like categories
- 5 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
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, six public coding benchmarks
Claude Sonnet 4.5
Claude Sonnet 4.5 scores 39.5 against 1.6.
3 and 2 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Sonnet 4.5
Claude Sonnet 4.5 leads, 20.7 against 12.3.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Claude Sonnet 4.5 has a AA Agentic Index result, 15.8.
Directional only
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 4.5 has a GPQA Diamond result, 81.6%.
Directional only
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Sonnet 4.5 has a MMLU Pro result, 87.4%.
Directional only
Web design
Design Arena: websites
No call
Only Claude Sonnet 4.5 has a Design Arena: websites result, 1189.
Directional only
Long documents
Listed context window
Claude Sonnet 4.5
Claude Sonnet 4.5 takes 1M tokens against 260K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 2.5
Claude Sonnet 4.5 $0.011, Mercury 2.5 $0.0001 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Sonnet 4.5 has the number, $1.16.
Directional only
At a glance
- Coding index
- Claude Sonnet 4.5 39.5 from 3 benchmarks, Mercury 2.5 1.6 from 2 benchmarks.
- Widest category
- General, 29.4 points apart on average over 1 shared benchmark.
- Widest single gap
- MedScribe (Vals AI): Claude Sonnet 4.5 84.5% against Mercury 2.5 55.1%, 29.4 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 4.5 $15.00 against Mercury 2.5 $0.15 per million output tokens, 100.0x apart.
- Context window
- Claude Sonnet 4.5 takes 1M tokens, Mercury 2.5 260K.
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 4.5 | Bars | Mercury 2.5 | Ties |
|---|---|---|---|---|
| Coding | 1 | 0 | ||
| Intelligence | 1 | 0 | ||
| Math | 1 | 0 | ||
| Knowledge | 2 | 0 | ||
| General | 1 | 0 | ||
| All shared boards | 6 | 0 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index10
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| SWE-bench Verified | 74.8% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Multilingual | 67.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev | 1394 | Not measured | Only Claude Sonnet 4.5 measured |
| AA Coding Index | 52.1 | Not measured | Only Claude Sonnet 4.5 measured |
| LiveCodeBench (Vals AI) | 73.0% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Verified (Vals AI) | 70.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 0.0% | Only Mercury 2.5 measured |
| Vibe Code Bench (Vals AI) | 22.6% | 3.7% | Claude Sonnet 4.5 |
| Code migration (Vals AI) | Not measured | 4.5% | Only Mercury 2.5 measured |
| IOI (Vals AI) | Not measured | 2.4% | Only Mercury 2.5 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 34.5% | Only Mercury 2.5 measured |
| SkillsBench (Vals AI) | Not measured | 18.1% | Only Mercury 2.5 measured |
| CyberBench (Vals AI) | Not measured | 45.5% | Only Mercury 2.5 measured |
| SciCode | Not measured | 38.5% | Only Mercury 2.5 measured |
| Terminal-Bench | 46.5% | Not measured | Only Claude Sonnet 4.5 measured |
| GSO-Bench | 14.7% | Not measured | Only Claude Sonnet 4.5 measured |
| WeirdML | 47.7% | Not measured | Only Claude Sonnet 4.5 measured |
| Cybench | 60.0% | Not measured | Only Claude Sonnet 4.5 measured |
| ALE-Bench | Not measured | 301.6 | Only Mercury 2.5 measured |
| LMArena Text: coding | 1488 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: software and IT | 1473 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev: React | 1386 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev: HTML | 1399 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 16 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.7 | 12.3 | Claude Sonnet 4.5 |
| Epoch Capabilities Index | 146.7 | Not measured | Only Claude Sonnet 4.5 measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index16 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| AA Agentic Index | 15.8 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building web apps | 1060 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building full-stack apps | 1050 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building mobile apps | 1137 | Not measured | Only Claude Sonnet 4.5 measured |
| Finance Agent (Vals AI) | Not measured | 18.9% | Only Mercury 2.5 measured |
| Tax Agent Bench (Vals AI) | Not measured | 2.5% | Only Mercury 2.5 measured |
| Legal Research Bench (Vals AI) | Not measured | 4.3% | Only Mercury 2.5 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 8.8% | Only Mercury 2.5 measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 0.0% | Only Mercury 2.5 measured |
| METR time horizons | 67.4% | Not measured | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 2.1% | Not measured | Only Claude Sonnet 4.5 measured |
| GDPval | 42.5% | Not measured | Only Claude Sonnet 4.5 measured |
| DeepResearch Bench | 52.6% | Not measured | Only Claude Sonnet 4.5 measured |
| OSWorld | 62.9% | Not measured | Only Claude Sonnet 4.5 measured |
| Vending-Bench 2 | $3,839 | Not measured | Only Claude Sonnet 4.5 measured |
| Berkeley Function Calling Leaderboard (BFCL) | 73.2% | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 25 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index15 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| GPQA Diamond | 81.6% | Not measured | Only Claude Sonnet 4.5 measured |
| MMMU Pro (Vals AI) | 79.3% | Not measured | Only Claude Sonnet 4.5 measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 11.8% | Only Mercury 2.5 measured |
| GPQA Diamond (Epoch AI run) | 82.3% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI | 63.7% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI-2 | 13.6% | Not measured | Only Claude Sonnet 4.5 measured |
| SimpleBench | 54.3% | Not measured | Only Claude Sonnet 4.5 measured |
| Chess puzzles | 10.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Mystery game puzzles | 17.0% | Not measured | Only Claude Sonnet 4.5 measured |
| EBR-bench | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| VPCT | 39.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1462 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: expert | 1483 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts in English | 1471 | Not measured | Only Claude Sonnet 4.5 measured |
| Kagi LLM Benchmark | 57.9% | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 7 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| AIME | 88.2% | Not measured | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | 94.3% | Not measured | Only Claude Sonnet 4.5 measured |
| OTIS Mock AIME | 77.8% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tiers 1 to 3 | 23.9% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| ProofBench | 19.0% | 3.0% | Claude Sonnet 4.5 |
| MATH level 5 | 97.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1449 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: mathematical work | 1462 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 4 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| MMLU Pro | 87.4% | Not measured | Only Claude Sonnet 4.5 measured |
| LegalBench (Vals AI) | 84.1% | 83.1% | Claude Sonnet 4.5 |
| CaseLaw (Vals AI) | 62.2% | Not measured | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | 62.0% | Not measured | Only Claude Sonnet 4.5 measured |
| TaxEval (Vals AI) | 73.3% | Not measured | Only Claude Sonnet 4.5 measured |
| MortgageTax (Vals AI) | 64.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MedQA (Vals AI) | 94.7% | Not measured | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 44.1% | 31.3% | Claude Sonnet 4.5 |
| SimpleQA Verified | 30.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: science | 1448 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: medicine and healthcare | 1444 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: legal and government | 1451 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: business and finance | 1440 | Not measured | Only Claude Sonnet 4.5 measured |
| FACTS Benchmark Suite | 40.6% | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 4 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1189 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: UI components | 1170 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: game dev | 1166 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: data viz | 1167 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: 3D | 1157 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: all code categories | 1182 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: SVG | 1115 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: ASCII art | 1205 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | Leader |
|---|---|---|---|
| Public Benefits Bench (Vals AI) | Not measured | 45.3% | Only Mercury 2.5 measured |
| SAGE (Vals AI) | 36.1% | Not measured | Only Claude Sonnet 4.5 measured |
| MedScribe (Vals AI) | 84.5% | 55.1% | Claude Sonnet 4.5 |
| Long context reasoning (AA-LCR) | Not measured | 71.7% | Only Mercury 2.5 measured |
| DTBench | 83.2% | Not measured | Only Claude Sonnet 4.5 measured |
| LMCA | 38.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text | 1438 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: instruction following | 1459 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: creative writing | 1442 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: English | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: non-English | 1425 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Chinese | 1460 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: German | 1427 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Japanese | 1390 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Korean | 1402 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: French | 1459 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Spanish | 1458 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Russian | 1437 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Polish | 1423 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: multi-turn | 1465 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: longer queries | 1475 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: writing and language | 1442 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: entertainment and media | 1428 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Document | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 22 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 | 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
Mercury 2.5 costs less
Repository review
50K input + 3K output tokens
Mercury 2.5 costs less
Agent loop
200K input + 10K output tokens
Mercury 2.5 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 4.5 | Inception Mercury 2.5 |
|---|---|---|
| Maker | Anthropic | Inception |
| Weights | No public weights listed | No public weights listed |
| Released | September 29, 2025 | September 8, 2026 |
| Context window | 1M | 260K |
| Input $/Mtok | $3.00 | $0.04 |
| Output $/Mtok | $15.00 | $0.15 |
| Coding index | 39.5 | 1.6 |
| Independent measurements behind it | 3 | 2 |
| Cost per solved task | $1.16 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 4.5 better than Mercury 2.5 for coding?
Pick Claude Sonnet 4.5 for coding: it scores 39.5 on the Vibe Coding Index against 1.6 for Mercury 2.5. Pick Mercury 2.5 for output tokens 100.0x cheaper ($0.15 vs $15.00 per million).
Which is cheaper, Claude Sonnet 4.5 or Mercury 2.5?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; Mercury 2.5 costs $0.04 and $0.15. Cost per solved task is known for Claude Sonnet 4.5 only.
Which has the bigger context window, Claude Sonnet 4.5 or Mercury 2.5?
Claude Sonnet 4.5, with 1M tokens against 260K.
How many benchmarks is the Claude Sonnet 4.5 vs Mercury 2.5 comparison based on?
6 benchmarks have a result for both models as of October 22, 2026. Claude Sonnet 4.5's coding index rests on 3 independent benchmarks and Mercury 2.5's on 2. Where only one model has a result, the page says so instead of naming a winner.