Claude Fable 5.1 vs Claude Sonnet 4.5
Updated October 21, 2026. 73 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 73 shared
Decision reading
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5.
Pick Claude Sonnet 4.5 when output tokens cost 3.3x less.
Model AClaude Fable 5.1Anthropic89.1/1002 independent benchmarksNo cost per solved taskModel BClaude Sonnet 4.5Anthropic59.1/1002 independent benchmarks$1.16 per solved task
- Shared results
- 73
- Claude Fable 5.1 only
- 51
- Claude Sonnet 4.5 only
- 19
- Like-for-like categories
- 8 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 Fable 5.1
Claude Fable 5.1 scores 89.1 against 59.1.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Claude Fable 5.1
Claude Fable 5.1 leads, 53.4 against 20.7.
Same board, both measured
Agentic work
AA Agentic Index
Claude Fable 5.1
Claude Fable 5.1 leads, 57.9 against 15.8.
Same board, both measured
Reasoning
GPQA Diamond
Claude Fable 5.1
Claude Fable 5.1 leads, 93.4% against 81.6%.
Same board, both measured
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
Claude Fable 5.1
Claude Fable 5.1 leads, 92.4% against 87.4%.
Same board, both measured
Web design
Design Arena: websites
Claude Fable 5.1
Claude Fable 5.1 leads, 1313 against 1190.
Same board, both measured
Long documents
Listed context window
No call
Both take 1M tokens.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Claude Sonnet 4.5
Claude Fable 5.1 $0.035, Claude Sonnet 4.5 $0.011 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 Fable 5.1 89.1 from 2 benchmarks, Claude Sonnet 4.5 59.1 from 2 benchmarks.
- Widest category
- Math, 46.9 points apart on average over 6 shared benchmarks.
- Widest single gap
- FrontierMath, tier 4: Claude Fable 5.1 87.8% against Claude Sonnet 4.5 2.4%, 85.4 points apart on a 0 to 100 scale.
- Output price
- Claude Fable 5.1 $50.00 against Claude Sonnet 4.5 $15.00 per million output tokens, 3.3x apart.
- Context window
- Both take 1M tokens.
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 Fable 5.1 | Bars | Claude Sonnet 4.5 | Ties |
|---|---|---|---|---|
| Coding | 10 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 6 | 0 | ||
| Reasoning | 10 | 0 | ||
| Math | 6 | 0 | ||
| Knowledge | 10 | 0 | ||
| Web design | 8 | 0 | ||
| General | 21 | 0 | ||
| All shared boards | 73 | 0 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index100
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 74.8% | Only Claude Sonnet 4.5 measured |
| SWE-bench Multilingual | Not measured | 67.0% | Only Claude Sonnet 4.5 measured |
| LiveBench coding | 97.7% | Not measured | Only Claude Fable 5.1 measured |
| LMArena WebDev | 1743 | 1394 | Claude Fable 5.1 |
| AA Coding Index | 81.6 | 52.1 | Claude Fable 5.1 |
| LiveCodeBench (Vals AI) | 90.5% | 73.0% | Claude Fable 5.1 |
| SWE-bench Verified (Vals AI) | Not measured | 70.0% | Only Claude Sonnet 4.5 measured |
| Terminal-Bench 4 (Vals AI) | 58.1% | Not measured | Only Claude Fable 5.1 measured |
| Vibe Code Bench (Vals AI) | 90.3% | 22.6% | Claude Fable 5.1 |
| Code migration (Vals AI) | 54.6% | Not measured | Only Claude Fable 5.1 measured |
| ProgramBench (Vals AI) | 7.0% | Not measured | Only Claude Fable 5.1 measured |
| IOI (Vals AI) | 90.8% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench 2.1 (Vals AI) | 85.0% | Not measured | Only Claude Fable 5.1 measured |
| SWE-bench Multimodal (Vals AI) | 61.3% | Not measured | Only Claude Fable 5.1 measured |
| Vibe Code Bench 1-100 (Vals AI) | 28.0% | Not measured | Only Claude Fable 5.1 measured |
| SkillsBench (Vals AI) | 61.5% | Not measured | Only Claude Fable 5.1 measured |
| CyberBench (Vals AI) | 70.4% | Not measured | Only Claude Fable 5.1 measured |
| SciCode | 63.1% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench | Not measured | 46.5% | Only Claude Sonnet 4.5 measured |
| FrontierCode | 50.9% | Not measured | Only Claude Fable 5.1 measured |
| FrontierSWE | 56.3% | Not measured | Only Claude Fable 5.1 measured |
| GSO-Bench | 88.2% | 14.7% | Claude Fable 5.1 |
| WeirdML | 92.9% | 47.7% | Claude Fable 5.1 |
| MirrorCode | 73.3% | Not measured | Only Claude Fable 5.1 measured |
| Cybench | Not measured | 60.0% | Only Claude Sonnet 4.5 measured |
| ALE-Bench | 2143.2 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: coding | 1532 | 1488 | Claude Fable 5.1 |
| LMArena Text: software and IT | 1530 | 1473 | Claude Fable 5.1 |
| LMArena WebDev: React | 1792 | 1386 | Claude Fable 5.1 |
| LMArena WebDev: HTML | 1684 | 1399 | Claude Fable 5.1 |
| LMArena WebDev: from an image | 1722 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 7 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 53.4 | 20.7 | Claude Fable 5.1 |
| Epoch Capabilities Index | 166.5 | 146.7 | Claude Fable 5.1 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| AA Agentic Index | 57.9 | 15.8 | Claude Fable 5.1 |
| Design Arena: agents building web apps | 1318 | 1060 | Claude Fable 5.1 |
| Design Arena: agents building full-stack apps | 1326 | 1050 | Claude Fable 5.1 |
| Design Arena: agents building mobile apps | 1267 | 1137 | Claude Fable 5.1 |
| Design Arena: agents building Godot games | 1327 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: PowerPoint slides | 1328 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: spreadsheets | 1374 | Not measured | Only Claude Fable 5.1 measured |
| LiveBench research | 82.0% | Not measured | Only Claude Fable 5.1 measured |
| LiveBench browser | 100.0% | Not measured | Only Claude Fable 5.1 measured |
| LiveBench long agentic | 80.8% | Not measured | Only Claude Fable 5.1 measured |
| SREBench (Vals AI) | 22.9% | Not measured | Only Claude Fable 5.1 measured |
| Finance Agent (Vals AI) | 58.9% | Not measured | Only Claude Fable 5.1 measured |
| Tax Agent Bench (Vals AI) | 49.2% | Not measured | Only Claude Fable 5.1 measured |
| Legal Research Bench (Vals AI) | 55.3% | Not measured | Only Claude Fable 5.1 measured |
| Excel Modeling Benchmark (Vals AI) | 76.7% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench-Science (Vals AI) | 40.0% | Not measured | Only Claude Fable 5.1 measured |
| Time Horizon Index (Vals AI) | 63.3% | Not measured | Only Claude Fable 5.1 measured |
| CUA-bench (Vals AI) | 13.2% | Not measured | Only Claude Fable 5.1 measured |
| Robo-bench (Vals AI) | 5.8% | Not measured | Only Claude Fable 5.1 measured |
| APEX-Agents | 68.6% | Not measured | Only Claude Fable 5.1 measured |
| METR time horizons | Not measured | 67.4% | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 17.9% | 2.1% | Claude Fable 5.1 |
| GDPval | Not measured | 42.5% | Only Claude Sonnet 4.5 measured |
| DeepResearch Bench | Not measured | 52.6% | Only Claude Sonnet 4.5 measured |
| OSWorld | Not measured | 62.9% | Only Claude Sonnet 4.5 measured |
| SpireClimb | 2.0% | Not measured | Only Claude Fable 5.1 measured |
| Vending-Bench 2 | $5,422 | $3,839 | Claude Fable 5.1 |
| LMArena Search | 1246 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 11 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index100
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| GPQA Diamond | 93.4% | 81.6% | Claude Fable 5.1 |
| LiveBench reasoning | 91.7% | Not measured | Only Claude Fable 5.1 measured |
| MysteryMechanism (Vals AI) | 47.8% | Not measured | Only Claude Fable 5.1 measured |
| MMMU Pro (Vals AI) | 90.6% | 79.3% | Claude Fable 5.1 |
| GPQA Diamond (Artificial Analysis run) | 93.7% | Not measured | Only Claude Fable 5.1 measured |
| Humanity's Last Exam (Artificial Analysis run) | 59.1% | Not measured | Only Claude Fable 5.1 measured |
| GPQA Diamond (Epoch AI run) | Not measured | 82.3% | Only Claude Sonnet 4.5 measured |
| ARC-AGI | 97.5% | 63.7% | Claude Fable 5.1 |
| ARC-AGI-2 | 90.0% | 13.6% | Claude Fable 5.1 |
| SimpleBench | Not measured | 54.3% | Only Claude Sonnet 4.5 measured |
| Chess puzzles | 48.0% | 10.0% | Claude Fable 5.1 |
| Mystery game puzzles | 58.0% | 17.0% | Claude Fable 5.1 |
| EBR-bench | 57.1% | 2.4% | Claude Fable 5.1 |
| VPCT | Not measured | 39.8% | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1528 | 1462 | Claude Fable 5.1 |
| LMArena Text: expert | 1544 | 1483 | Claude Fable 5.1 |
| LMArena Text: hard prompts in English | 1522 | 1471 | Claude Fable 5.1 |
| LMArena Vision: diagrams | 1343 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Vision: homework | 1345 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 2 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| AIME | Not measured | 88.2% | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | Not measured | 94.3% | Only Claude Sonnet 4.5 measured |
| OTIS Mock AIME | 100.0% | 77.8% | Claude Fable 5.1 |
| FrontierMath, tiers 1 to 3 | 90.2% | 23.9% | Claude Fable 5.1 |
| FrontierMath, tier 4 | 87.8% | 2.4% | Claude Fable 5.1 |
| ProofBench | 100.0% | 19.0% | Claude Fable 5.1 |
| MATH level 5 | Not measured | 97.7% | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1531 | 1449 | Claude Fable 5.1 |
| LMArena Text: mathematical work | 1541 | 1462 | Claude Fable 5.1 |
| Neither model has a result on the other 4 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| MMLU Pro | 92.4% | 87.4% | Claude Fable 5.1 |
| LegalBench (Vals AI) | 88.5% | 84.1% | Claude Fable 5.1 |
| CaseLaw (Vals AI) | Not measured | 62.2% | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | Not measured | 62.0% | Only Claude Sonnet 4.5 measured |
| TaxEval (Vals AI) | 76.0% | 73.3% | Claude Fable 5.1 |
| MortgageTax (Vals AI) | 70.8% | 64.0% | Claude Fable 5.1 |
| MedQA (Vals AI) | Not measured | 94.7% | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 53.5% | 44.1% | Claude Fable 5.1 |
| SimpleQA Verified | 70.8% | 30.7% | Claude Fable 5.1 |
| LMArena Text: science | 1532 | 1448 | Claude Fable 5.1 |
| LMArena Text: medicine and healthcare | 1531 | 1444 | Claude Fable 5.1 |
| LMArena Text: legal and government | 1514 | 1451 | Claude Fable 5.1 |
| LMArena Text: business and finance | 1493 | 1440 | Claude Fable 5.1 |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index80
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1313 | 1190 | Claude Fable 5.1 |
| Design Arena: UI components | 1338 | 1173 | Claude Fable 5.1 |
| Design Arena: game dev | 1382 | 1166 | Claude Fable 5.1 |
| Design Arena: data viz | 1344 | 1167 | Claude Fable 5.1 |
| Design Arena: 3D | 1393 | 1158 | Claude Fable 5.1 |
| Design Arena: all code categories | 1336 | 1183 | Claude Fable 5.1 |
| Design Arena: SVG | 1301 | 1114 | Claude Fable 5.1 |
| Design Arena: ASCII art | 1324 | 1204 | Claude Fable 5.1 |
| LiveBench design | 83.4% | Not measured | Only Claude Fable 5.1 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index210
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | Leader |
|---|---|---|---|
| LiveBench data analysis | 80.3% | Not measured | Only Claude Fable 5.1 measured |
| Public Benefits Bench (Vals AI) | 74.9% | Not measured | Only Claude Fable 5.1 measured |
| SAGE (Vals AI) | 48.5% | 36.1% | Claude Fable 5.1 |
| MedScribe (Vals AI) | 91.3% | 84.5% | Claude Fable 5.1 |
| Long context reasoning (AA-LCR) | 85.3% | Not measured | Only Claude Fable 5.1 measured |
| DTBench | 97.6% | 83.2% | Claude Fable 5.1 |
| LMCA | 65.5% | 38.8% | Claude Fable 5.1 |
| Furniture assembly | 70.0% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text | 1512 | 1438 | Claude Fable 5.1 |
| LMArena Text: instruction following | 1518 | 1459 | Claude Fable 5.1 |
| LMArena Text: creative writing | 1509 | 1442 | Claude Fable 5.1 |
| LMArena Vision | 1319 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: English | 1506 | 1450 | Claude Fable 5.1 |
| LMArena Text: non-English | 1508 | 1425 | Claude Fable 5.1 |
| LMArena Text: Chinese | 1584 | 1460 | Claude Fable 5.1 |
| LMArena Text: German | 1499 | 1427 | Claude Fable 5.1 |
| LMArena Text: Japanese | 1562 | 1390 | Claude Fable 5.1 |
| LMArena Text: Korean | 1517 | 1402 | Claude Fable 5.1 |
| LMArena Text: French | 1523 | 1459 | Claude Fable 5.1 |
| LMArena Text: Spanish | 1520 | 1458 | Claude Fable 5.1 |
| LMArena Text: Russian | 1520 | 1437 | Claude Fable 5.1 |
| LMArena Text: Polish | 1525 | 1423 | Claude Fable 5.1 |
| LMArena Text: multi-turn | 1493 | 1465 | Claude Fable 5.1 |
| LMArena Text: longer queries | 1524 | 1475 | Claude Fable 5.1 |
| LMArena Text: writing and language | 1510 | 1442 | Claude Fable 5.1 |
| LMArena Text: entertainment and media | 1497 | 1428 | Claude Fable 5.1 |
| LMArena Vision: English | 1313 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Vision: Chinese | 1391 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Vision: reading text | 1327 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Vision: humor | 1318 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Vision: creative writing | 1330 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Document | Not measured | 1450 | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Fable 5.1 | Claude Sonnet 4.5 | 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
Claude Fable 5.1$0.035Fits in one request
Claude Sonnet 4.5$0.011Fits in one request
Claude Sonnet 4.5 costs less
Repository review
50K input + 3K output tokens
Claude Fable 5.1$0.650Fits in one request
Claude Sonnet 4.5$0.195Fits in one request
Claude Sonnet 4.5 costs less
Agent loop
200K input + 10K output tokens
Claude Fable 5.1$2.50Fits in one request
Claude Sonnet 4.5$0.750Fits in one request
Claude Sonnet 4.5 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 Fable 5.1 | Anthropic Claude Sonnet 4.5 |
|---|---|---|
| Maker | Anthropic | Anthropic |
| Weights | No public weights listed | No public weights listed |
| Released | September 1, 2026 | September 29, 2025 |
| Context window | 1M | 1M |
| Input $/Mtok | $10.00 | $3.00 |
| Output $/Mtok | $50.00 | $15.00 |
| Coding index | 89.1 | 59.1 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | Not computable | $1.16 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Fable 5.1 better than Claude Sonnet 4.5 for coding?
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5. Pick Claude Sonnet 4.5 when output tokens cost 3.3x less.
Which is cheaper, Claude Fable 5.1 or Claude Sonnet 4.5?
Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Sonnet 4.5 costs $3.00 and $15.00. Cost per solved task is known for Claude Sonnet 4.5 only.
Which has the bigger context window, Claude Fable 5.1 or Claude Sonnet 4.5?
Neither: both take 1M tokens.
How many benchmarks is the Claude Fable 5.1 vs Claude Sonnet 4.5 comparison based on?
73 benchmarks have a result for both models as of October 21, 2026. Claude Fable 5.1's coding index rests on 2 independent benchmarks and Claude Sonnet 4.5's on 2. Where only one model has a result, the page says so instead of naming a winner.