Claude Fable 5.1 vs GPT-5 Nano
Updated October 21, 2026. 67 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 67 shared
Decision reading
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 34.8 for GPT-5 Nano.
Pick GPT-5 Nano when output tokens cost 125.0x less.
Model AClaude Fable 5.1Anthropic89.1/1002 independent benchmarksNo cost per solved taskModel BGPT-5 NanoOpenAI34.8/1001 independent benchmark$0.109 per solved task
- Shared results
- 67
- Claude Fable 5.1 only
- 57
- GPT-5 Nano only
- 18
- 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 Fable 5.1
Claude Fable 5.1 scores 89.1 against 34.8.
2 and 1 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Fable 5.1
Claude Fable 5.1 leads, 53.4 against 13.0.
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 63.4%.
Same board, both measured
Math
AIME
No call
Only GPT-5 Nano has a AIME result, 81.2%.
Directional only
Knowledge
MMLU Pro
Claude Fable 5.1
Claude Fable 5.1 leads, 92.4% against 76.1%.
Same board, both measured
Web design
Design Arena: websites
Claude Fable 5.1
Claude Fable 5.1 leads, 1313 against 1101.
Same board, both measured
Long documents
Listed context window
Claude Fable 5.1
Claude Fable 5.1 takes 1M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5 Nano
Claude Fable 5.1 $0.035, GPT-5 Nano $0.0003 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5 Nano has the number, $0.109.
Directional only
At a glance
- Coding index
- Claude Fable 5.1 89.1 from 2 benchmarks, GPT-5 Nano 34.8 from 1 benchmark.
- Widest category
- Math, 55.6 points apart on average over 6 shared benchmarks.
- Widest single gap
- ProofBench: Claude Fable 5.1 100.0% against GPT-5 Nano 12.0%, 88.0 points apart on a 0 to 100 scale.
- Output price
- Claude Fable 5.1 $50.00 against GPT-5 Nano $0.40 per million output tokens, 125.0x apart.
- Context window
- Claude Fable 5.1 takes 1M tokens, GPT-5 Nano 400K.
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 | GPT-5 Nano | Ties |
|---|---|---|---|---|
| Coding | 4 | 0 | ||
| Intelligence | 2 | 0 | ||
| Reasoning | 13 | 0 | ||
| Math | 6 | 0 | ||
| Knowledge | 10 | 0 | ||
| Web design | 6 | 0 | ||
| General | 26 | 0 | ||
| All shared boards | 67 | 0 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index40
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 34.8% | Only GPT-5 Nano measured |
| LiveBench coding | 97.7% | Not measured | Only Claude Fable 5.1 measured |
| LMArena WebDev | 1743 | Not measured | Only Claude Fable 5.1 measured |
| AA Coding Index | 81.6 | Not measured | Only Claude Fable 5.1 measured |
| LiveCodeBench (Vals AI) | 90.5% | 70.2% | Claude Fable 5.1 |
| Terminal-Bench 4 (Vals AI) | 58.1% | Not measured | Only Claude Fable 5.1 measured |
| Vibe Code Bench (Vals AI) | 90.3% | Not measured | Only Claude Fable 5.1 measured |
| 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 | 78.9% | Only GPT-5 Nano measured |
| SciCode | 63.1% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 17.4% | Only GPT-5 Nano measured |
| Terminal-Bench | Not measured | 21.8% | Only GPT-5 Nano 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% | Not measured | Only Claude Fable 5.1 measured |
| WeirdML | 92.9% | 38.1% | Claude Fable 5.1 |
| MirrorCode | 73.3% | Not measured | Only Claude Fable 5.1 measured |
| ALE-Bench | 2143.2 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: coding | 1532 | 1351 | Claude Fable 5.1 |
| LMArena Text: software and IT | 1530 | 1345 | Claude Fable 5.1 |
| LMArena WebDev: React | 1792 | Not measured | Only Claude Fable 5.1 measured |
| LMArena WebDev: HTML | 1684 | Not measured | Only Claude Fable 5.1 measured |
| LMArena WebDev: from an image | 1722 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 8 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| AA Intelligence Index | 53.4 | 13.0 | Claude Fable 5.1 |
| Epoch Capabilities Index | 166.5 | 139.2 | Claude Fable 5.1 |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index25 boards, none shared
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| AA Agentic Index | 57.9 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: agents building web apps | 1318 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: agents building full-stack apps | 1326 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: agents building mobile apps | 1267 | Not measured | Only Claude Fable 5.1 measured |
| 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 |
| τ²-Bench Telecom | Not measured | 36.5% | Only GPT-5 Nano measured |
| APEX-Agents | 68.6% | Not measured | Only Claude Fable 5.1 measured |
| Remote Labor Index | 17.9% | Not measured | Only Claude Fable 5.1 measured |
| SpireClimb | 2.0% | Not measured | Only Claude Fable 5.1 measured |
| Vending-Bench 2 | $5,422 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Search | 1246 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 14 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index130
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| GPQA Diamond | 93.4% | 63.4% | 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% | 70.9% | Claude Fable 5.1 |
| GPQA Diamond (Artificial Analysis run) | 93.7% | 67.6% | Claude Fable 5.1 |
| Humanity's Last Exam (Artificial Analysis run) | 59.1% | 9.5% | Claude Fable 5.1 |
| GPQA Diamond (Epoch AI run) | Not measured | 69.4% | Only GPT-5 Nano measured |
| ARC-AGI | 97.5% | 20.7% | Claude Fable 5.1 |
| ARC-AGI-2 | 90.0% | 2.6% | Claude Fable 5.1 |
| Chess puzzles | 48.0% | 22.0% | Claude Fable 5.1 |
| Mystery game puzzles | 58.0% | 9.0% | Claude Fable 5.1 |
| EBR-bench | 57.1% | Not measured | Only Claude Fable 5.1 measured |
| VPCT | Not measured | 37.2% | Only GPT-5 Nano measured |
| LMArena Text: hard prompts | 1528 | 1328 | Claude Fable 5.1 |
| LMArena Text: expert | 1544 | 1321 | Claude Fable 5.1 |
| LMArena Text: hard prompts in English | 1522 | 1338 | Claude Fable 5.1 |
| LMArena Vision: diagrams | 1343 | 1141 | Claude Fable 5.1 |
| LMArena Vision: homework | 1345 | 1157 | Claude Fable 5.1 |
| Neither model has a result on the other 3 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| AIME | Not measured | 81.2% | Only GPT-5 Nano measured |
| MATH 500 (Vals AI) | Not measured | 93.8% | Only GPT-5 Nano measured |
| MGSM (Vals AI) | Not measured | 89.3% | Only GPT-5 Nano measured |
| AA Math Index | Not measured | 83.7 | Only GPT-5 Nano measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 83.7% | Only GPT-5 Nano measured |
| OTIS Mock AIME | 100.0% | 81.1% | Claude Fable 5.1 |
| FrontierMath, tiers 1 to 3 | 90.2% | 20.0% | Claude Fable 5.1 |
| FrontierMath, tier 4 | 87.8% | 2.4% | Claude Fable 5.1 |
| ProofBench | 100.0% | 12.0% | Claude Fable 5.1 |
| MATH level 5 | Not measured | 95.2% | Only GPT-5 Nano measured |
| LMArena Text: math | 1531 | 1317 | Claude Fable 5.1 |
| LMArena Text: mathematical work | 1541 | 1326 | Claude Fable 5.1 |
| Neither model has a result on the other 1 board here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| MMLU Pro | 92.4% | 76.1% | Claude Fable 5.1 |
| LegalBench (Vals AI) | 88.5% | 50.1% | Claude Fable 5.1 |
| CaseLaw (Vals AI) | Not measured | 52.6% | Only GPT-5 Nano measured |
| TaxEval (Vals AI) | 76.0% | 67.4% | Claude Fable 5.1 |
| MortgageTax (Vals AI) | 70.8% | 53.6% | Claude Fable 5.1 |
| MedQA (Vals AI) | Not measured | 93.3% | Only GPT-5 Nano measured |
| MedCode (Vals AI) | 53.5% | 30.4% | Claude Fable 5.1 |
| MMLU Pro (Artificial Analysis run) | Not measured | 78.0% | Only GPT-5 Nano measured |
| SimpleQA Verified | 70.8% | 11.7% | Claude Fable 5.1 |
| LMArena Text: science | 1532 | 1318 | Claude Fable 5.1 |
| LMArena Text: medicine and healthcare | 1531 | 1335 | Claude Fable 5.1 |
| LMArena Text: legal and government | 1514 | 1298 | Claude Fable 5.1 |
| LMArena Text: business and finance | 1493 | 1311 | 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 index60
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | Leader |
|---|---|---|---|
| Design Arena: websites | 1313 | 1101 | Claude Fable 5.1 |
| Design Arena: UI components | 1338 | 1066 | Claude Fable 5.1 |
| Design Arena: game dev | 1382 | 1045 | Claude Fable 5.1 |
| Design Arena: data viz | 1344 | 1056 | Claude Fable 5.1 |
| Design Arena: 3D | 1393 | 966 | Claude Fable 5.1 |
| Design Arena: all code categories | 1336 | 1084 | Claude Fable 5.1 |
| Design Arena: SVG | 1301 | Not measured | Only Claude Fable 5.1 measured |
| Design Arena: ASCII art | 1324 | Not measured | Only Claude Fable 5.1 measured |
| LiveBench design | 83.4% | Not measured | Only Claude Fable 5.1 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index260
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | 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% | 30.4% | Claude Fable 5.1 |
| MedScribe (Vals AI) | 91.3% | 72.9% | Claude Fable 5.1 |
| IFBench | Not measured | 67.6% | Only GPT-5 Nano measured |
| Long context reasoning (AA-LCR) | 85.3% | 45.0% | Claude Fable 5.1 |
| DTBench | 97.6% | 62.7% | Claude Fable 5.1 |
| LMCA | 65.5% | 7.9% | Claude Fable 5.1 |
| Fiction.LiveBench | Not measured | 44.4% | Only GPT-5 Nano measured |
| Furniture assembly | 70.0% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text | 1512 | 1320 | Claude Fable 5.1 |
| LMArena Text: instruction following | 1518 | 1306 | Claude Fable 5.1 |
| LMArena Text: creative writing | 1509 | 1249 | Claude Fable 5.1 |
| LMArena Vision | 1319 | 1159 | Claude Fable 5.1 |
| LMArena Text: English | 1506 | 1321 | Claude Fable 5.1 |
| LMArena Text: non-English | 1508 | 1313 | Claude Fable 5.1 |
| LMArena Text: Chinese | 1584 | 1356 | Claude Fable 5.1 |
| LMArena Text: German | 1499 | 1327 | Claude Fable 5.1 |
| LMArena Text: Japanese | 1562 | 1227 | Claude Fable 5.1 |
| LMArena Text: Korean | 1517 | 1269 | Claude Fable 5.1 |
| LMArena Text: French | 1523 | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: Spanish | 1520 | 1360 | Claude Fable 5.1 |
| LMArena Text: Russian | 1520 | 1296 | Claude Fable 5.1 |
| LMArena Text: Polish | 1525 | 1314 | Claude Fable 5.1 |
| LMArena Text: multi-turn | 1493 | 1311 | Claude Fable 5.1 |
| LMArena Text: longer queries | 1524 | 1312 | Claude Fable 5.1 |
| LMArena Text: writing and language | 1510 | 1283 | Claude Fable 5.1 |
| LMArena Text: entertainment and media | 1497 | 1268 | Claude Fable 5.1 |
| LMArena Vision: English | 1313 | 1170 | Claude Fable 5.1 |
| LMArena Vision: Chinese | 1391 | 1176 | Claude Fable 5.1 |
| LMArena Vision: reading text | 1327 | 1152 | Claude Fable 5.1 |
| LMArena Vision: humor | 1318 | 1110 | Claude Fable 5.1 |
| LMArena Vision: creative writing | 1330 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 13 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Fable 5.1 | GPT-5 Nano | 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
GPT-5 Nano$0.0003Fits in one request
GPT-5 Nano costs less
Repository review
50K input + 3K output tokens
Claude Fable 5.1$0.650Fits in one request
GPT-5 Nano$0.0037Fits in one request
GPT-5 Nano costs less
Agent loop
200K input + 10K output tokens
Claude Fable 5.1$2.50Fits in one request
GPT-5 Nano$0.014Fits in one request
GPT-5 Nano 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 | OpenAI GPT-5 Nano |
|---|---|---|
| Maker | Anthropic | OpenAI |
| Weights | No public weights listed | No public weights listed |
| Released | September 1, 2026 | August 7, 2025 |
| Context window | 1M | 400K |
| Input $/Mtok | $10.00 | $0.05 |
| Output $/Mtok | $50.00 | $0.40 |
| Coding index | 89.1 | 34.8 |
| Independent measurements behind it | 2 | 1 |
| Cost per solved task | Not computable | $0.109 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Fable 5.1 better than GPT-5 Nano for coding?
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 34.8 for GPT-5 Nano. Pick GPT-5 Nano when output tokens cost 125.0x less.
Which is cheaper, Claude Fable 5.1 or GPT-5 Nano?
Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5 Nano costs $0.05 and $0.40. Cost per solved task is known for GPT-5 Nano only.
Which has the bigger context window, Claude Fable 5.1 or GPT-5 Nano?
Claude Fable 5.1, with 1M tokens against 400K.
How many benchmarks is the Claude Fable 5.1 vs GPT-5 Nano comparison based on?
67 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 GPT-5 Nano's on 1. Where only one model has a result, the page says so instead of naming a winner.