Claude Fable 5.1 vs Gemini 2.5 Flash
Updated October 21, 2026. 56 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 56 shared
Decision reading
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 28.7 for Gemini 2.5 Flash.
Pick Gemini 2.5 Flash when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.
Model AClaude Fable 5.1Anthropic89.1/1002 independent benchmarksNo cost per solved taskModel BGemini 2.5 FlashGoogle28.7/1001 independent benchmark$0.466 per solved task
- Shared results
- 56
- Claude Fable 5.1 only
- 68
- Gemini 2.5 Flash only
- 13
- 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 28.7.
2 and 1 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Fable 5.1
Claude Fable 5.1 leads, 53.4 against 15.5.
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
No call
Only Claude Fable 5.1 has a GPQA Diamond result, 93.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Fable 5.1 has a MMLU Pro result, 92.4%.
Directional only
Web design
Design Arena: websites
Claude Fable 5.1
Claude Fable 5.1 leads, 1313 against 1074.
Same board, both measured
Long documents
Listed context window
Gemini 2.5 Flash
Gemini 2.5 Flash takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 2.5 Flash
Claude Fable 5.1 $0.035, Gemini 2.5 Flash $0.0015 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Gemini 2.5 Flash has the number, $0.466.
Directional only
At a glance
- Coding index
- Claude Fable 5.1 89.1 from 2 benchmarks, Gemini 2.5 Flash 28.7 from 1 benchmark.
- Widest category
- Web design, 38.7 points apart on average over 7 shared benchmarks.
- Widest single gap
- ARC-AGI-2: Claude Fable 5.1 90.0% against Gemini 2.5 Flash 2.5%, 87.5 points apart on a 0 to 100 scale.
- Output price
- Claude Fable 5.1 $50.00 against Gemini 2.5 Flash $2.50 per million output tokens, 20.0x apart.
- Context window
- Claude Fable 5.1 takes 1M tokens, Gemini 2.5 Flash 1.05M.
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 | Gemini 2.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 2 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 1 | 0 | ||
| Reasoning | 9 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 5 | 0 | ||
| Web design | 7 | 0 | ||
| General | 28 | 0 | ||
| All shared boards | 56 | 0 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index20
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 28.7% | Only Gemini 2.5 Flash 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% | Not measured | Only Claude Fable 5.1 measured |
| 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 | 69.5% | Only Gemini 2.5 Flash measured |
| SciCode | 63.1% | Not measured | Only Claude Fable 5.1 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 13.6% | Only Gemini 2.5 Flash measured |
| Terminal-Bench | Not measured | 17.1% | Only Gemini 2.5 Flash 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% | Not measured | Only Claude Fable 5.1 measured |
| 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 | 1423 | Claude Fable 5.1 |
| LMArena Text: software and IT | 1530 | 1425 | 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 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 53.4 | 15.5 | Claude Fable 5.1 |
| Epoch Capabilities Index | 166.5 | 142.9 | Claude Fable 5.1 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | 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 | 31.6% | Only Gemini 2.5 Flash 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 |
| BALROG | Not measured | 33.5% | Only Gemini 2.5 Flash measured |
| SpireClimb | 2.0% | Not measured | Only Claude Fable 5.1 measured |
| Vending-Bench 2 | $5,422 | $549 | Claude Fable 5.1 |
| LMArena Search | 1246 | Not measured | Only Claude Fable 5.1 measured |
| Neither model has a result on the other 13 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index90
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| GPQA Diamond | 93.4% | Not measured | Only Claude Fable 5.1 measured |
| 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% | Not measured | Only Claude Fable 5.1 measured |
| GPQA Diamond (Artificial Analysis run) | 93.7% | 79.0% | Claude Fable 5.1 |
| Humanity's Last Exam (Artificial Analysis run) | 59.1% | 12.1% | Claude Fable 5.1 |
| ARC-AGI | 97.5% | 33.3% | Claude Fable 5.1 |
| ARC-AGI-2 | 90.0% | 2.5% | Claude Fable 5.1 |
| SimpleBench | Not measured | 41.2% | Only Gemini 2.5 Flash measured |
| Chess puzzles | 48.0% | Not measured | Only Claude Fable 5.1 measured |
| Mystery game puzzles | 58.0% | Not measured | Only Claude Fable 5.1 measured |
| EBR-bench | 57.1% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: hard prompts | 1528 | 1422 | Claude Fable 5.1 |
| LMArena Text: expert | 1544 | 1426 | Claude Fable 5.1 |
| LMArena Text: hard prompts in English | 1522 | 1420 | Claude Fable 5.1 |
| LMArena Vision: diagrams | 1343 | 1245 | Claude Fable 5.1 |
| LMArena Vision: homework | 1345 | 1244 | Claude Fable 5.1 |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| AA Math Index | Not measured | 73.3 | Only Gemini 2.5 Flash measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 73.3% | Only Gemini 2.5 Flash measured |
| OTIS Mock AIME | 100.0% | Not measured | Only Claude Fable 5.1 measured |
| FrontierMath, tiers 1 to 3 | 90.2% | Not measured | Only Claude Fable 5.1 measured |
| FrontierMath, tier 4 | 87.8% | Not measured | Only Claude Fable 5.1 measured |
| ProofBench | 100.0% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: math | 1531 | 1411 | Claude Fable 5.1 |
| LMArena Text: mathematical work | 1541 | 1422 | Claude Fable 5.1 |
| Neither model has a result on the other 5 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| MMLU Pro | 92.4% | Not measured | Only Claude Fable 5.1 measured |
| LegalBench (Vals AI) | 88.5% | Not measured | Only Claude Fable 5.1 measured |
| TaxEval (Vals AI) | 76.0% | Not measured | Only Claude Fable 5.1 measured |
| MortgageTax (Vals AI) | 70.8% | Not measured | Only Claude Fable 5.1 measured |
| MedCode (Vals AI) | 53.5% | 40.4% | Claude Fable 5.1 |
| MMLU Pro (Artificial Analysis run) | Not measured | 83.2% | Only Gemini 2.5 Flash measured |
| SimpleQA Verified | 70.8% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text: science | 1532 | 1433 | Claude Fable 5.1 |
| LMArena Text: medicine and healthcare | 1531 | 1428 | Claude Fable 5.1 |
| LMArena Text: legal and government | 1514 | 1430 | Claude Fable 5.1 |
| LMArena Text: business and finance | 1493 | 1404 | Claude Fable 5.1 |
| Neither model has a result on the other 6 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index70
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1313 | 1074 | Claude Fable 5.1 |
| Design Arena: UI components | 1338 | 1005 | Claude Fable 5.1 |
| Design Arena: game dev | 1382 | 1005 | Claude Fable 5.1 |
| Design Arena: data viz | 1344 | 1060 | Claude Fable 5.1 |
| Design Arena: 3D | 1393 | 1021 | Claude Fable 5.1 |
| Design Arena: all code categories | 1336 | 1059 | Claude Fable 5.1 |
| Design Arena: SVG | 1301 | 1018 | Claude Fable 5.1 |
| 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 index280
| Benchmark | Claude Fable 5.1 | Gemini 2.5 Flash | 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% | 44.8% | Claude Fable 5.1 |
| MedScribe (Vals AI) | 91.3% | 83.0% | Claude Fable 5.1 |
| IFBench | Not measured | 50.3% | Only Gemini 2.5 Flash measured |
| Long context reasoning (AA-LCR) | 85.3% | 65.3% | Claude Fable 5.1 |
| DTBench | 97.6% | 76.5% | Claude Fable 5.1 |
| LMCA | 65.5% | 27.5% | Claude Fable 5.1 |
| Furniture assembly | 70.0% | Not measured | Only Claude Fable 5.1 measured |
| LMArena Text | 1512 | 1417 | Claude Fable 5.1 |
| LMArena Text: instruction following | 1518 | 1405 | Claude Fable 5.1 |
| LMArena Text: creative writing | 1509 | 1400 | Claude Fable 5.1 |
| LMArena Vision | 1319 | 1235 | Claude Fable 5.1 |
| LMArena Text: English | 1506 | 1418 | Claude Fable 5.1 |
| LMArena Text: non-English | 1508 | 1409 | Claude Fable 5.1 |
| LMArena Text: Chinese | 1584 | 1449 | Claude Fable 5.1 |
| LMArena Text: German | 1499 | 1417 | Claude Fable 5.1 |
| LMArena Text: Japanese | 1562 | 1396 | Claude Fable 5.1 |
| LMArena Text: Korean | 1517 | 1385 | Claude Fable 5.1 |
| LMArena Text: French | 1523 | 1432 | Claude Fable 5.1 |
| LMArena Text: Spanish | 1520 | 1422 | Claude Fable 5.1 |
| LMArena Text: Russian | 1520 | 1415 | Claude Fable 5.1 |
| LMArena Text: Polish | 1525 | 1413 | Claude Fable 5.1 |
| LMArena Text: multi-turn | 1493 | 1408 | Claude Fable 5.1 |
| LMArena Text: longer queries | 1524 | 1419 | Claude Fable 5.1 |
| LMArena Text: writing and language | 1510 | 1405 | Claude Fable 5.1 |
| LMArena Text: entertainment and media | 1497 | 1393 | Claude Fable 5.1 |
| LMArena Vision: English | 1313 | 1239 | Claude Fable 5.1 |
| LMArena Vision: Chinese | 1391 | 1284 | Claude Fable 5.1 |
| LMArena Vision: reading text | 1327 | 1237 | Claude Fable 5.1 |
| LMArena Vision: humor | 1318 | 1225 | Claude Fable 5.1 |
| LMArena Vision: captioning | Not measured | 1277 | Only Gemini 2.5 Flash measured |
| LMArena Vision: recognizing things | Not measured | 1252 | Only Gemini 2.5 Flash measured |
| LMArena Vision: creative writing | 1330 | 1241 | Claude Fable 5.1 |
| 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 | Gemini 2.5 Flash | 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
Gemini 2.5 Flash$0.0015Fits in one request
Gemini 2.5 Flash costs less
Repository review
50K input + 3K output tokens
Claude Fable 5.1$0.650Fits in one request
Gemini 2.5 Flash$0.022Fits in one request
Gemini 2.5 Flash costs less
Agent loop
200K input + 10K output tokens
Claude Fable 5.1$2.50Fits in one request
Gemini 2.5 Flash$0.085Fits in one request
Gemini 2.5 Flash 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 | Google Gemini 2.5 Flash |
|---|---|---|
| Maker | Anthropic | |
| Weights | No public weights listed | No public weights listed |
| Released | September 1, 2026 | June 17, 2025 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $10.00 | $0.30 |
| Output $/Mtok | $50.00 | $2.50 |
| Coding index | 89.1 | 28.7 |
| Independent measurements behind it | 2 | 1 |
| Cost per solved task | Not computable | $0.466 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Fable 5.1 better than Gemini 2.5 Flash for coding?
Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 28.7 for Gemini 2.5 Flash. Pick Gemini 2.5 Flash when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.
Which is cheaper, Claude Fable 5.1 or Gemini 2.5 Flash?
Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Gemini 2.5 Flash costs $0.30 and $2.50. Cost per solved task is known for Gemini 2.5 Flash only.
Which has the bigger context window, Claude Fable 5.1 or Gemini 2.5 Flash?
Gemini 2.5 Flash, with 1.05M tokens against 1M.
How many benchmarks is the Claude Fable 5.1 vs Gemini 2.5 Flash comparison based on?
56 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 Gemini 2.5 Flash's on 1. Where only one model has a result, the page says so instead of naming a winner.