Claude Fable 5.1 vs Claude Opus 4.5
Claude Fable 5.1 leads Claude Opus 4.5 on coding, 84.2 to 44.0 on the Vibe Coding Index, and Claude Opus 4.5 costs 2.0x less per output token ($25.00 vs $50.00 per million). Updated October 22, 2026; 75 benchmarks have a result for both.
vs boards won of 75 shared
Claude Fable 5.1 or Claude Opus 4.5: which to pick
Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 44.0 for Claude Opus 4.5.
Pick Claude Opus 4.5 for output tokens 2.0x cheaper ($25.00 vs $50.00 per million) and work measured by SAGE (Vals AI), where it leads.
Model AClaude Fable 5.1Anthropic84.2/1005 independent benchmarksNo cost per solved taskModel BClaude Opus 4.5Anthropic44.0/1003 independent benchmarks$1.37 per solved task
- Shared results
- 75
- Claude Fable 5.1 only
- 49
- Claude Opus 4.5 only
- 33
- Like-for-like categories
- 8 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 Fable 5.1
Claude Fable 5.1 scores 84.2 against 44.0.
5 and 3 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Fable 5.1
Claude Fable 5.1 leads, 53.4 against 29.1.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Claude Fable 5.1 has a AA Agentic Index result, 57.9.
Directional only
Reasoning
GPQA Diamond
Claude Fable 5.1
Claude Fable 5.1 leads, 93.4% against 85.9%.
Same board, both measured
Math
AIME
No call
Only Claude Opus 4.5 has a AIME result, 95.4%.
Directional only
Knowledge
MMLU Pro
Claude Fable 5.1
Claude Fable 5.1 leads, 92.4% against 87.3%.
Same board, both measured
Web design
Design Arena: websites
Claude Fable 5.1
Claude Fable 5.1 leads, 1312 against 1247.
Same board, both measured
Long documents
Listed context window
Claude Fable 5.1
Claude Fable 5.1 takes 1M tokens against 200K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Claude Opus 4.5
Claude Fable 5.1 $0.035, Claude Opus 4.5 $0.018 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Opus 4.5 has the number, $1.37.
Directional only
At a glance
- Coding index
- Claude Fable 5.1 84.2 from 5 benchmarks, Claude Opus 4.5 44.0 from 3 benchmarks.
- Widest category
- Math, 40.0 points apart on average over 6 shared benchmarks.
- Widest single gap
- FrontierMath, tier 4: Claude Fable 5.1 87.8% against Claude Opus 4.5 4.9%, 82.9 points apart on a 0 to 100 scale.
- Output price
- Claude Fable 5.1 $50.00 against Claude Opus 4.5 $25.00 per million output tokens, 2.0x apart.
- Context window
- Claude Fable 5.1 takes 1M tokens, Claude Opus 4.5 200K.
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 Opus 4.5 | Ties |
|---|---|---|---|---|
| Coding | 9 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 5 | 0 | ||
| Reasoning | 12 | 0 | ||
| Math | 6 | 0 | ||
| Knowledge | 10 | 0 | ||
| Web design | 8 | 0 | ||
| General | 22 | 1 | ||
| All shared boards | 74 | 1 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index90
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 79.2% | Only Claude Opus 4.5 measured |
| SWE-bench (full test set) | Not measured | 52.6% | Only Claude Opus 4.5 measured |
| SWE-bench Multilingual | Not measured | 70.7% | Only Claude Opus 4.5 measured |
| LiveBench coding | 97.7% | Not measured | Only Claude Fable 5.1 measured |
| LMArena WebDev | 1743 | 1494 | Claude Fable 5.1 |
| AA Coding Index | 81.6 | Not measured | Only Claude Fable 5.1 measured |
| LiveCodeBench (Vals AI) | 90.5% | 83.7% | Claude Fable 5.1 |
| SWE-bench Verified (Vals AI) | Not measured | 76.4% | Only Claude Opus 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% | 20.6% | 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 |
| LiveCodeBench (Artificial Analysis run) | Not measured | 87.1% | Only Claude Opus 4.5 measured |
| SciCode | 63.1% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 47.0% | Only Claude Opus 4.5 measured |
| Terminal-Bench | Not measured | 63.1% | Only Claude Opus 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% | 26.5% | Claude Fable 5.1 |
| WeirdML | 92.9% | 63.7% | Claude Fable 5.1 |
| MirrorCode | 73.3% | Not measured | Only Claude Fable 5.1 measured |
| Cybench | Not measured | 82.0% | Only Claude Opus 4.5 measured |
| ALE-Bench | 2143.2 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: coding | 1532 | 1503 | Claude Fable 5.1 |
| LMArena Text: software and IT | 1530 | 1483 | Claude Fable 5.1 |
| LMArena WebDev: React | 1792 | 1478 | Claude Fable 5.1 |
| LMArena WebDev: HTML | 1684 | 1510 | 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 5 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 53.4 | 29.1 | Claude Fable 5.1 |
| Epoch Capabilities Index | 166.5 | 150.1 | Claude Fable 5.1 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| AA Agentic Index | 57.9 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: agents building web apps | 1318 | 1159 | Claude Fable 5.1 |
| Design Arena: agents building full-stack apps | 1326 | 1156 | Claude Fable 5.1 |
| Design Arena: agents building mobile apps | 1267 | 1189 | Claude Fable 5.1 |
| Design Arena: agents building Android apps | Not measured | 1176 | Only Claude Opus 4.5 measured |
| Design Arena: agents building Godot games | 1327 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: PowerPoint slides | 1305 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: spreadsheets | 1380 | 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 |
| τ²-Bench Telecom | Not measured | 89.5% | Only Claude Opus 4.5 measured |
| APEX-Agents | 68.6% | Not measured | Only Claude Fable 5.1 measured |
| METR time horizons | Not measured | 75.0% | Only Claude Opus 4.5 measured |
| Remote Labor Index | 17.9% | 3.8% | Claude Fable 5.1 |
| GDPval | Not measured | 45.5% | Only Claude Opus 4.5 measured |
| BALROG | Not measured | 43.5% | Only Claude Opus 4.5 measured |
| DeepResearch Bench | Not measured | 54.8% | Only Claude Opus 4.5 measured |
| OSWorld | Not measured | 66.3% | Only Claude Opus 4.5 measured |
| SpireClimb | 2.0% | Not measured | Only Claude Fable 5.1 measured |
| Vending-Bench 2 | $5,422 | $4,967 | Claude Fable 5.1 |
| LMArena Search | 1246 | Not measured | Only Claude Fable 5.1 measured |
| Berkeley Function Calling Leaderboard (BFCL) | Not measured | 77.5% | Only Claude Opus 4.5 measured |
| Neither model has a result on the other 9 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index120
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| GPQA Diamond | 93.4% | 85.9% | 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% | 83.0% | Claude Fable 5.1 |
| GPQA Diamond (Artificial Analysis run) | 93.7% | 86.6% | Claude Fable 5.1 |
| Humanity's Last Exam (Artificial Analysis run) | 59.1% | 30.1% | Claude Fable 5.1 |
| GPQA Diamond (Epoch AI run) | Not measured | 86.0% | Only Claude Opus 4.5 measured |
| ARC-AGI | 97.5% | 80.0% | Claude Fable 5.1 |
| ARC-AGI-2 | 90.0% | 37.6% | Claude Fable 5.1 |
| SimpleBench | Not measured | 62.0% | Only Claude Opus 4.5 measured |
| Chess puzzles | 48.0% | 14.0% | Claude Fable 5.1 |
| Mystery game puzzles | 58.0% | 22.0% | Claude Fable 5.1 |
| EBR-bench | 57.1% | 14.3% | Claude Fable 5.1 |
| VPCT | Not measured | 40.0% | Only Claude Opus 4.5 measured |
| LMArena Text: hard prompts | 1528 | 1476 | Claude Fable 5.1 |
| LMArena Text: expert | 1544 | 1487 | Claude Fable 5.1 |
| LMArena Text: hard prompts in English | 1522 | 1482 | 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 |
| Kagi LLM Benchmark | Not measured | 80.2% | Only Claude Opus 4.5 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 Opus 4.5 | Leader |
|---|---|---|---|
| AIME | Not measured | 95.4% | Only Claude Opus 4.5 measured |
| MGSM (Vals AI) | Not measured | 95.2% | Only Claude Opus 4.5 measured |
| AA Math Index | Not measured | 91.3 | Only Claude Opus 4.5 measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 91.3% | Only Claude Opus 4.5 measured |
| OTIS Mock AIME | 100.0% | 86.1% | Claude Fable 5.1 |
| FrontierMath, tiers 1 to 3 | 90.2% | 34.4% | Claude Fable 5.1 |
| FrontierMath, tier 4 | 87.8% | 4.9% | Claude Fable 5.1 |
| ProofBench | 100.0% | 36.0% | Claude Fable 5.1 |
| LMArena Text: math | 1531 | 1463 | Claude Fable 5.1 |
| LMArena Text: mathematical work | 1541 | 1468 | Claude Fable 5.1 |
| Neither model has a result on the other 3 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| MMLU Pro | 92.4% | 87.3% | Claude Fable 5.1 |
| LegalBench (Vals AI) | 88.5% | 84.6% | Claude Fable 5.1 |
| CaseLaw (Vals AI) | Not measured | 62.6% | Only Claude Opus 4.5 measured |
| CorpFin (Vals AI) | Not measured | 65.1% | Only Claude Opus 4.5 measured |
| TaxEval (Vals AI) | 76.0% | 74.9% | Claude Fable 5.1 |
| MortgageTax (Vals AI) | 70.8% | 68.7% | Claude Fable 5.1 |
| MedQA (Vals AI) | Not measured | 95.9% | Only Claude Opus 4.5 measured |
| MedCode (Vals AI) | 53.5% | 49.2% | Claude Fable 5.1 |
| MMLU Pro (Artificial Analysis run) | Not measured | 89.5% | Only Claude Opus 4.5 measured |
| SimpleQA Verified | 70.8% | 45.7% | Claude Fable 5.1 |
| GeoBench | Not measured | 75.0% | Only Claude Opus 4.5 measured |
| LMArena Text: science | 1532 | 1454 | Claude Fable 5.1 |
| LMArena Text: medicine and healthcare | 1531 | 1444 | Claude Fable 5.1 |
| LMArena Text: legal and government | 1514 | 1459 | Claude Fable 5.1 |
| LMArena Text: business and finance | 1493 | 1448 | Claude Fable 5.1 |
| FACTS Benchmark Suite | Not measured | 43.9% | Only Claude Opus 4.5 measured |
| Neither model has a result on the other 2 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index80
| Benchmark | Claude Fable 5.1 | Claude Opus 4.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1312 | 1247 | Claude Fable 5.1 |
| Design Arena: UI components | 1336 | 1235 | Claude Fable 5.1 |
| Design Arena: game dev | 1381 | 1228 | Claude Fable 5.1 |
| Design Arena: data viz | 1344 | 1243 | Claude Fable 5.1 |
| Design Arena: 3D | 1392 | 1213 | Claude Fable 5.1 |
| Design Arena: all code categories | 1335 | 1242 | Claude Fable 5.1 |
| Design Arena: SVG | 1300 | 1180 | Claude Fable 5.1 |
| Design Arena: ASCII art | 1323 | 1190 | 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 index221
| Benchmark | Claude Fable 5.1 | Claude Opus 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% | 52.1% | Claude Opus 4.5 |
| MedScribe (Vals AI) | 91.3% | 85.3% | Claude Fable 5.1 |
| IFBench | Not measured | 58.0% | Only Claude Opus 4.5 measured |
| Long context reasoning (AA-LCR) | 85.3% | 77.3% | Claude Fable 5.1 |
| DTBench | 97.6% | 89.9% | Claude Fable 5.1 |
| LMCA | 65.5% | 44.5% | Claude Fable 5.1 |
| CL-bench | Not measured | 21.1% | Only Claude Opus 4.5 measured |
| Furniture assembly | 70.0% | 28.3% | Claude Fable 5.1 |
| LMArena Text | 1512 | 1451 | Claude Fable 5.1 |
| LMArena Text: instruction following | 1518 | 1478 | Claude Fable 5.1 |
| LMArena Text: creative writing | 1509 | 1445 | Claude Fable 5.1 |
| LMArena Vision | 1319 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: English | 1506 | 1461 | Claude Fable 5.1 |
| LMArena Text: non-English | 1508 | 1438 | Claude Fable 5.1 |
| LMArena Text: Chinese | 1584 | 1470 | Claude Fable 5.1 |
| LMArena Text: German | 1499 | 1449 | Claude Fable 5.1 |
| LMArena Text: Japanese | 1562 | 1417 | Claude Fable 5.1 |
| LMArena Text: Korean | 1517 | 1424 | Claude Fable 5.1 |
| LMArena Text: French | 1523 | 1471 | Claude Fable 5.1 |
| LMArena Text: Spanish | 1520 | 1457 | Claude Fable 5.1 |
| LMArena Text: Russian | 1520 | 1447 | Claude Fable 5.1 |
| LMArena Text: Polish | 1525 | 1439 | Claude Fable 5.1 |
| LMArena Text: multi-turn | 1493 | 1466 | Claude Fable 5.1 |
| LMArena Text: longer queries | 1524 | 1479 | Claude Fable 5.1 |
| LMArena Text: writing and language | 1510 | 1452 | Claude Fable 5.1 |
| LMArena Text: entertainment and media | 1497 | 1434 | 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 | 1462 | Only Claude Opus 4.5 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 Fable 5.1 | Claude Opus 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 Opus 4.5$0.018Fits in one request
Claude Opus 4.5 costs less
Repository review
50K input + 3K output tokens
Claude Fable 5.1$0.650Fits in one request
Claude Opus 4.5$0.325Fits in one request
Claude Opus 4.5 costs less
Agent loop
200K input + 10K output tokens
Claude Fable 5.1$2.50Fits in one request
Claude Opus 4.5$1.25Exceeds the context window
Claude Opus 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 Opus 4.5 |
|---|---|---|
| Maker | Anthropic | Anthropic |
| Weights | No public weights listed | No public weights listed |
| Released | September 1, 2026 | November 24, 2025 |
| Context window | 1M | 200K |
| Input $/Mtok | $10.00 | $5.00 |
| Output $/Mtok | $50.00 | $25.00 |
| Coding index | 84.2 | 44.0 |
| Independent measurements behind it | 5 | 3 |
| Cost per solved task | Not computable | $1.37 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Fable 5.1 better than Claude Opus 4.5 for coding?
Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 44.0 for Claude Opus 4.5. Pick Claude Opus 4.5 for output tokens 2.0x cheaper ($25.00 vs $50.00 per million) and work measured by SAGE (Vals AI), where it leads.
Which is cheaper, Claude Fable 5.1 or Claude Opus 4.5?
Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Opus 4.5 costs $5.00 and $25.00. Cost per solved task is known for Claude Opus 4.5 only.
Which has the bigger context window, Claude Fable 5.1 or Claude Opus 4.5?
Claude Fable 5.1, with 1M tokens against 200K.
How many benchmarks is the Claude Fable 5.1 vs Claude Opus 4.5 comparison based on?
75 benchmarks have a result for both models as of October 22, 2026. Claude Fable 5.1's coding index rests on 5 independent benchmarks and Claude Opus 4.5's on 3. Where only one model has a result, the page says so instead of naming a winner.