Claude Fable 5 vs GPT-5 Nano

Claude Fable 5 leads GPT-5 Nano on the Artificial Analysis Intelligence Index, 49.6 to 13.0, and GPT-5 Nano costs 125.0x less per output token ($0.40 vs $50.00 per million). Updated October 22, 2026; 72 benchmarks have a result for both.

Replace Claude Fable 5 Replace GPT-5 Nano

Claude Fable 5Anthropic

Coding: 79.3
Overall: 79.0
Output $/M: $50.00

GPT-5 NanoOpenAI

Coding: No data
Overall: 35.6
Output $/M: $0.40

vs boards won of 72 shared

Claude Fable 5 or GPT-5 Nano: which to pick

Only Claude Fable 5 has a coding score, 79.3 on the Vibe Coding Index; GPT-5 Nano has none, so the two cannot be ranked on coding.

Pick GPT-5 Nano for output tokens 125.0x cheaper ($0.40 vs $50.00 per million) and a lower cost per solved task ($0.109 against $2.16).

Model AClaude Fable 5Anthropic79.3/1006 independent benchmarks$2.16 per solved task Model BGPT-5 NanoOpenAINot benchmarkedNo coding benchmark$0.109 per solved task

725515

Shared results: 72
Claude Fable 5 only: 55
GPT-5 Nano only: 15
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
No call
Only Claude Fable 5 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Claude Fable 5
Claude Fable 5 leads, 49.6 against 13.0.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Claude Fable 5 has a AA Agentic Index result, 50.7.
Directional only
Reasoning
GPQA Diamond
Claude Fable 5
Claude Fable 5 leads, 93.2% 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
Claude Fable 5 leads, 91.5% against 76.1%.
Same board, both measured
Web design
Design Arena: websites
Claude Fable 5
Claude Fable 5 leads, 1295 against 1101.
Same board, both measured
Long documents
Listed context window
Claude Fable 5
Claude Fable 5 takes 1M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5 Nano
Claude Fable 5 $0.035, GPT-5 Nano $0.0003 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5 Nano
Claude Fable 5 $2.16, GPT-5 Nano $0.109.
Published attempt cost and pass rate

At a glance

Coding index: Claude Fable 5 79.3 from 6 benchmarks, GPT-5 Nano not benchmarked.
Widest category: Agentic work, 62.0 points apart on average over 1 shared benchmark.
Widest single gap: FrontierMath, tier 4: Claude Fable 5 90.2% against GPT-5 Nano 2.4%, 87.8 points apart on a 0 to 100 scale.
Output price: Claude Fable 5 $50.00 against GPT-5 Nano $0.40 per million output tokens, 125.0x apart.
Context window: Claude Fable 5 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.

Boards won, where both have a result
Category	Claude Fable 5	GPT-5 Nano
Coding	5	0
Intelligence	2	0
Agentic work	1	0
Reasoning	15	0
Math	6	0
Knowledge	10	0
Web design	6	0
General	26	1
All shared boards	71	1

CodingLike-for-likeSix of these boards feed the Vibe Coding Index50

Coding benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
SWE-bench Verified	Not measured	34.8%	Only GPT-5 Nano measured
LiveBench coding	98.3%	Not measured	Only Claude Fable 5 measured
LMArena WebDev	1624	Not measured	Only Claude Fable 5 measured
AA Coding Index	76.5	Not measured	Only Claude Fable 5 measured
LiveCodeBench (Vals AI)	89.8%	70.2%	Claude Fable 5
SWE-bench Verified (Vals AI)	95.0%	Not measured	Only Claude Fable 5 measured
Terminal-Bench 4 (Vals AI)	41.4%	Not measured	Only Claude Fable 5 measured
Vibe Code Bench (Vals AI)	90.3%	Not measured	Only Claude Fable 5 measured
Code migration (Vals AI)	55.1%	Not measured	Only Claude Fable 5 measured
ProgramBench (Vals AI)	2.0%	Not measured	Only Claude Fable 5 measured
Terminal-Bench 2.1 (Vals AI)	80.5%	Not measured	Only Claude Fable 5 measured
LiveCodeBench (Artificial Analysis run)	Not measured	78.9%	Only GPT-5 Nano measured
SciCode	61.0%	Not measured	Only Claude Fable 5 measured
Terminal-Bench Hard (Artificial Analysis run)	62.9%	17.4%	Claude Fable 5
Terminal-Bench	Not measured	21.8%	Only GPT-5 Nano measured
FrontierCode	53.5%	Not measured	Only Claude Fable 5 measured
FrontierSWE	47.0%	Not measured	Only Claude Fable 5 measured
GSO-Bench	78.4%	Not measured	Only Claude Fable 5 measured
WeirdML	91.9%	38.1%	Claude Fable 5
MirrorCode	63.9%	Not measured	Only Claude Fable 5 measured
ALE-Bench	2041.3	Not measured	Only Claude Fable 5 measured
LMArena Text: coding	1518	1351	Claude Fable 5
LMArena Text: software and IT	1513	1345	Claude Fable 5
LMArena WebDev: React	1631	Not measured	Only Claude Fable 5 measured
LMArena WebDev: HTML	1651	Not measured	Only Claude Fable 5 measured
LMArena WebDev: from an image	1623	Not measured	Only Claude Fable 5 measured
Neither model has a result on the other 13 boards here

IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20

Intelligence benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
AA Intelligence Index	49.6	13.0	Claude Fable 5
Epoch Capabilities Index	163.4	139.2	Claude Fable 5

Agentic workLike-for-likePublic boards, shown as published, kept out of the index10

Agentic work benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
AA Agentic Index	50.7	Not measured	Only Claude Fable 5 measured
Design Arena: agents building web apps	1261	Not measured	Only Claude Fable 5 measured
Design Arena: agents building full-stack apps	1280	Not measured	Only Claude Fable 5 measured
Design Arena: agents building mobile apps	1264	Not measured	Only Claude Fable 5 measured
Design Arena: agents building Android apps	1284	Not measured	Only Claude Fable 5 measured
Design Arena: agents building Godot games	1292	Not measured	Only Claude Fable 5 measured
Design Arena: agents building games	1285	Not measured	Only Claude Fable 5 measured
Design Arena: HTML slides	1227	Not measured	Only Claude Fable 5 measured
Design Arena: PowerPoint slides	1270	Not measured	Only Claude Fable 5 measured
LiveBench research	86.9%	Not measured	Only Claude Fable 5 measured
LiveBench browser	92.0%	Not measured	Only Claude Fable 5 measured
LiveBench long agentic	53.2%	Not measured	Only Claude Fable 5 measured
Finance Agent (Vals AI)	56.3%	Not measured	Only Claude Fable 5 measured
Tax Agent Bench (Vals AI)	38.3%	Not measured	Only Claude Fable 5 measured
Legal Research Bench (Vals AI)	49.5%	Not measured	Only Claude Fable 5 measured
Excel Modeling Benchmark (Vals AI)	73.7%	Not measured	Only Claude Fable 5 measured
Terminal-Bench-Science (Vals AI)	15.7%	Not measured	Only Claude Fable 5 measured
τ²-Bench Telecom	98.5%	36.5%	Claude Fable 5
APEX-Agents	63.6%	Not measured	Only Claude Fable 5 measured
Remote Labor Index	16.1%	Not measured	Only Claude Fable 5 measured
PostTrainBench	41.8%	Not measured	Only Claude Fable 5 measured
Vending-Bench 2	$5,680	Not measured	Only Claude Fable 5 measured
LMArena Search	1229	Not measured	Only Claude Fable 5 measured
Berkeley Function Calling Leaderboard (BFCL)	Not measured	51.4%	Only GPT-5 Nano measured
Neither model has a result on the other 17 boards here

ReasoningLike-for-likePublic boards, shown as published, kept out of the index150

Reasoning benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
GPQA Diamond	93.2%	63.4%	Claude Fable 5
LiveBench reasoning	89.7%	Not measured	Only Claude Fable 5 measured
MMMU Pro (Vals AI)	89.3%	70.9%	Claude Fable 5
GPQA Diamond (Artificial Analysis run)	92.6%	67.6%	Claude Fable 5
Humanity's Last Exam (Artificial Analysis run)	55.5%	9.5%	Claude Fable 5
GPQA Diamond (Epoch AI run)	85.9%	69.4%	Claude Fable 5
ARC-AGI	98.5%	20.7%	Claude Fable 5
ARC-AGI-2	89.2%	2.6%	Claude Fable 5
SimpleBench	81.9%	Not measured	Only Claude Fable 5 measured
Chess puzzles	47.0%	22.0%	Claude Fable 5
Mystery game puzzles	52.0%	9.0%	Claude Fable 5
EBR-bench	39.5%	Not measured	Only Claude Fable 5 measured
VPCT	Not measured	37.2%	Only GPT-5 Nano measured
LMArena Text: hard prompts	1507	1328	Claude Fable 5
LMArena Text: expert	1534	1321	Claude Fable 5
LMArena Text: hard prompts in English	1509	1338	Claude Fable 5
LMArena Vision: diagrams	1357	1141	Claude Fable 5
LMArena Vision: homework	1361	1157	Claude Fable 5
Kagi LLM Benchmark	91.4%	62.2%	Claude Fable 5
Neither model has a result on the other 3 boards here

MathLike-for-likePublic boards, shown as published, kept out of the index60

Math benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	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
FrontierMath, tiers 1 to 3	87.0%	20.0%	Claude Fable 5
FrontierMath, tier 4	90.2%	2.4%	Claude Fable 5
ProofBench	95.0%	12.0%	Claude Fable 5
MATH level 5	Not measured	95.2%	Only GPT-5 Nano measured
LMArena Text: math	1516	1317	Claude Fable 5
LMArena Text: mathematical work	1515	1326	Claude Fable 5
Neither model has a result on the other 1 board here

KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100

Knowledge benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
MMLU Pro	91.5%	76.1%	Claude Fable 5
LegalBench (Vals AI)	88.6%	50.1%	Claude Fable 5
CaseLaw (Vals AI)	Not measured	52.6%	Only GPT-5 Nano measured
CorpFin (Vals AI)	71.8%	Not measured	Only Claude Fable 5 measured
TaxEval (Vals AI)	76.9%	67.4%	Claude Fable 5
MortgageTax (Vals AI)	68.9%	53.6%	Claude Fable 5
MedQA (Vals AI)	Not measured	93.3%	Only GPT-5 Nano measured
MedCode (Vals AI)	56.1%	30.4%	Claude Fable 5
MMLU Pro (Artificial Analysis run)	Not measured	78.0%	Only GPT-5 Nano measured
SimpleQA Verified	70.7%	11.7%	Claude Fable 5
LMArena Text: science	1506	1318	Claude Fable 5
LMArena Text: medicine and healthcare	1480	1335	Claude Fable 5
LMArena Text: legal and government	1498	1298	Claude Fable 5
LMArena Text: business and finance	1480	1311	Claude Fable 5
Neither model has a result on the other 4 boards here

Web designLike-for-likePublic boards, shown as published, kept out of the index60

Web design benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
Design Arena: websites	1295	1101	Claude Fable 5
Design Arena: UI components	1316	1064	Claude Fable 5
Design Arena: game dev	1335	1044	Claude Fable 5
Design Arena: data viz	1304	1056	Claude Fable 5
Design Arena: 3D	1318	965	Claude Fable 5
Design Arena: all code categories	1310	1084	Claude Fable 5
Design Arena: SVG	1302	Not measured	Only Claude Fable 5 measured
Design Arena: ASCII art	1329	Not measured	Only Claude Fable 5 measured
LiveBench design	84.7%	Not measured	Only Claude Fable 5 measured

GeneralLike-for-likePublic boards, shown as published, kept out of the index261

General benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	GPT-5 Nano	Leader
LiveBench data analysis	80.5%	Not measured	Only Claude Fable 5 measured
Public Benefits Bench (Vals AI)	70.4%	Not measured	Only Claude Fable 5 measured
SAGE (Vals AI)	51.9%	30.4%	Claude Fable 5
MedScribe (Vals AI)	88.5%	72.9%	Claude Fable 5
Vals Multimodal Index	74.2%	Not measured	Only Claude Fable 5 measured
IFBench	63.5%	67.6%	GPT-5 Nano
Long context reasoning (AA-LCR)	82.3%	45.0%	Claude Fable 5
DTBench	98.4%	62.7%	Claude Fable 5
LMCA	61.2%	7.9%	Claude Fable 5
Fiction.LiveBench	Not measured	44.4%	Only GPT-5 Nano measured
Surface Evolver Bench	95.0%	Not measured	Only Claude Fable 5 measured
Furniture assembly	35.8%	Not measured	Only Claude Fable 5 measured
LMArena Text	1491	1320	Claude Fable 5
LMArena Text: instruction following	1502	1306	Claude Fable 5
LMArena Text: creative writing	1494	1249	Claude Fable 5
LMArena Vision	1325	1159	Claude Fable 5
LMArena Text: English	1498	1321	Claude Fable 5
LMArena Text: non-English	1482	1313	Claude Fable 5
LMArena Text: Chinese	1543	1356	Claude Fable 5
LMArena Text: German	1486	1327	Claude Fable 5
LMArena Text: Japanese	1504	1227	Claude Fable 5
LMArena Text: Korean	1487	1269	Claude Fable 5
LMArena Text: French	1505	Not measured	Only Claude Fable 5 measured
LMArena Text: Spanish	1498	1360	Claude Fable 5
LMArena Text: Russian	1503	1296	Claude Fable 5
LMArena Text: Polish	1494	1314	Claude Fable 5
LMArena Text: multi-turn	1504	1311	Claude Fable 5
LMArena Text: longer queries	1510	1312	Claude Fable 5
LMArena Text: writing and language	1501	1283	Claude Fable 5
LMArena Text: entertainment and media	1482	1268	Claude Fable 5
LMArena Vision: English	1323	1170	Claude Fable 5
LMArena Vision: Chinese	1373	1176	Claude Fable 5
LMArena Vision: reading text	1337	1152	Claude Fable 5
LMArena Vision: humor	1341	1110	Claude Fable 5
LMArena Vision: creative writing	1338	Not measured	Only Claude Fable 5 measured
LMArena Document	1496	Not measured	Only Claude Fable 5 measured
Neither model has a result on the other 10 boards here

Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared

Image generation benchmarks for Claude Fable 5 and GPT-5 Nano
Benchmark	Claude Fable 5	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$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$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$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.

Specifications of Claude Fable 5 and GPT-5 Nano
Specification	Anthropic Claude Fable 5	OpenAI GPT-5 Nano
Maker	Anthropic	OpenAI
Weights	No public weights listed	No public weights listed
Released	June 9, 2026	August 7, 2025
Context window	1M	400K
Input $/Mtok	$10.00	$0.05
Output $/Mtok	$50.00	$0.40
Coding index	79.3	Not benchmarked
Independent measurements behind it	6	0
Cost per solved task	$2.16	$0.109
Source	OpenRouter listing	OpenRouter listing

Questions

Is Claude Fable 5 better than GPT-5 Nano for coding?

Only Claude Fable 5 has a coding score, 79.3 on the Vibe Coding Index; GPT-5 Nano has none, so the two cannot be ranked on coding. Pick GPT-5 Nano for output tokens 125.0x cheaper ($0.40 vs $50.00 per million) and a lower cost per solved task ($0.109 against $2.16).

Which is cheaper, Claude Fable 5 or GPT-5 Nano?

Claude Fable 5 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5 Nano costs $0.05 and $0.40. Per solved SWE-bench Verified task, Claude Fable 5 costs $2.16 and GPT-5 Nano $0.109.

Which has the bigger context window, Claude Fable 5 or GPT-5 Nano?

Claude Fable 5, with 1M tokens against 400K.

How many benchmarks is the Claude Fable 5 vs GPT-5 Nano comparison based on?

72 benchmarks have a result for both models as of October 22, 2026. Claude Fable 5's coding index rests on 6 independent benchmarks and GPT-5 Nano's on 0. Where only one model has a result, the page says so instead of naming a winner.

Claude Fable 5 or GPT-5 Nano: which to pick

Which one for your work

Coding

Intelligence

Agentic work

Reasoning

Math

Knowledge

Web design

Long documents

Everyday cost

Cost per solved task

At a glance

Benchmark by benchmark

What each workload costs

Chat turn

Repository review

Agent loop

Specification differences

Questions

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