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Claude Fable 5.1 vs GPT-5.6 Terra

Claude Fable 5.1 leads GPT-5.6 Terra on coding, 84.2 to 63.9 on the Vibe Coding Index, and GPT-5.6 Terra costs 4.2x less per output token ($12.00 vs $50.00 per million). Updated October 22, 2026; 111 benchmarks have a result for both.

Replace Claude Fable 5.1 Replace GPT-5.6 Terra
Claude Fable 5.1Anthropic
Coding
84.2
Overall
84.7
Output $/M
$50.00
108
GPT-5.6 TerraOpenAI
Coding
63.9
Overall
68.1
Output $/M
$12.00
3
vs boards won of 111 shared

Claude Fable 5.1 or GPT-5.6 Terra: which to pick

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 63.9 for GPT-5.6 Terra, though on 5 benchmarks against 6.

Pick GPT-5.6 Terra for output tokens 4.2x cheaper ($12.00 vs $50.00 per million) and a larger context window (1.05M against 1M tokens).

Model AClaude Fable 5.1Anthropic84.2/1005 independent benchmarksNo cost per solved taskModel BGPT-5.6 TerraOpenAI63.9/1006 independent benchmarks$0.42 per solved task
Shared results
111
Claude Fable 5.1 only
22
GPT-5.6 Terra only
18
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.

At a glance

Coding index
Claude Fable 5.1 84.2 from 5 benchmarks, GPT-5.6 Terra 63.9 from 6 benchmarks.
Widest category
Agentic work, 18.8 points apart on average over 16 shared benchmarks.
Widest single gap
Terminal-Bench 4 (Vals AI): Claude Fable 5.1 58.1% against GPT-5.6 Terra 22.7%, 47.1 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against GPT-5.6 Terra $12.00 per million output tokens, 4.2x apart.
Context window
Claude Fable 5.1 takes 1M tokens, GPT-5.6 Terra 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.

Boards won, where both have a result
CategoryClaude Fable 5.1BarsGPT-5.6 TerraTies
Coding221
Intelligence20
Agentic work151
Reasoning140
Math60
Knowledge91
Web design90
General310
All shared boards1083
CodingLike-for-likeSix of these boards feed the Vibe Coding Index221
Coding benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
LiveBench coding97.7%86.2%Claude Fable 5.1
LMArena WebDev17431522Claude Fable 5.1
AA Coding Index81.676.7Claude Fable 5.1
LiveCodeBench (Vals AI)90.5%85.9%Claude Fable 5.1
SWE-bench Verified (Vals AI)Not measured95.4%Only GPT-5.6 Terra measured
Terminal-Bench 4 (Vals AI)58.1%22.7%Claude Fable 5.1
Vibe Code Bench (Vals AI)90.3%74.6%Claude Fable 5.1
Code migration (Vals AI)54.6%47.8%Claude Fable 5.1
ProgramBench (Vals AI)7.0%0.5%Claude Fable 5.1
IOI (Vals AI)90.8%87.6%Claude Fable 5.1
Terminal-Bench 2.1 (Vals AI)85.0%77.5%Claude Fable 5.1
SWE-bench Multimodal (Vals AI)61.3%Not measuredOnly Claude Fable 5.1 measured
Vibe Code Bench 1-100 (Vals AI)28.0%14.8%Claude Fable 5.1
SkillsBench (Vals AI)61.5%58.9%Claude Fable 5.1
CyberBench (Vals AI)70.4%72.1%GPT-5.6 Terra
SciCode63.1%55.0%Claude Fable 5.1
Terminal-Bench Hard (Artificial Analysis run)Not measured62.9%Only GPT-5.6 Terra measured
FrontierCode50.9%41.3%Claude Fable 5.1
FrontierSWE56.3%Not measuredOnly Claude Fable 5.1 measured
GSO-Bench88.2%Not measuredOnly Claude Fable 5.1 measured
WeirdML92.9%78.3%Claude Fable 5.1
MirrorCode73.3%Not measuredOnly Claude Fable 5.1 measured
ALE-Bench2143.21951.4Claude Fable 5.1
LMArena Text: coding15321485Claude Fable 5.1
LMArena Text: software and IT15301482Claude Fable 5.1
LMArena WebDev: React17921513Claude Fable 5.1
LMArena WebDev: HTML16841526Claude Fable 5.1
LMArena WebDev: from an image17221541Claude Fable 5.1
SciCodeNot measured10.8%Only GPT-5.6 Terra measured
SWE-Bench Pro V299.1%92.4%Claude Fable 5.1
SWE Atlas: Codebase QnA60.0%Not measuredOnly Claude Fable 5.1 measured
SWE Atlas: Refactoring56.7%Not measuredOnly Claude Fable 5.1 measured
SWE Atlas: Test Writing67.0%Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 10 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
AA Intelligence Index53.442.1Claude Fable 5.1
Epoch Capabilities Index166.5160.1Claude Fable 5.1
Agentic workLike-for-likePublic boards, shown as published, kept out of the index151
Agentic work benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
AA Agentic Index57.943.2Claude Fable 5.1
Design Arena: agents building web apps13181120Claude Fable 5.1
Design Arena: agents building full-stack apps13261061Claude Fable 5.1
Design Arena: agents building mobile apps12671110Claude Fable 5.1
Design Arena: agents building Android appsNot measured1060Only GPT-5.6 Terra measured
Design Arena: agents building Godot games1327Not measuredOnly Claude Fable 5.1 measured
Design Arena: agents building gamesNot measured1083Only GPT-5.6 Terra measured
Design Arena: HTML slidesNot measured1047Only GPT-5.6 Terra measured
Design Arena: PowerPoint slides13071104Claude Fable 5.1
Design Arena: spreadsheets1394Not measuredOnly Claude Fable 5.1 measured
LiveBench research82.0%60.4%Claude Fable 5.1
LiveBench browser100.0%84.0%Claude Fable 5.1
LiveBench long agentic80.8%48.4%Claude Fable 5.1
SREBench (Vals AI)22.9%9.5%Claude Fable 5.1
Finance Agent (Vals AI)58.9%54.4%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%30.0%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%41.4%Claude Fable 5.1
Excel Modeling Benchmark (Vals AI)76.7%66.2%Claude Fable 5.1
Terminal-Bench-Science (Vals AI)40.0%10.0%Claude Fable 5.1
Time Horizon Index (Vals AI)63.3%Not measuredOnly Claude Fable 5.1 measured
CUA-bench (Vals AI)13.2%Not measuredOnly Claude Fable 5.1 measured
Robo-bench (Vals AI)5.8%Not measuredOnly Claude Fable 5.1 measured
τ²-Bench TelecomNot measured86.3%Only GPT-5.6 Terra measured
APEX-Agents68.6%58.2%Claude Fable 5.1
Remote Labor Index17.9%Not measuredOnly Claude Fable 5.1 measured
BALROGNot measured53.2%Only GPT-5.6 Terra measured
SpireClimb2.0%Not measuredOnly Claude Fable 5.1 measured
Vending-Bench 2$5,422$7,343GPT-5.6 Terra
LMArena Search1246Not measuredOnly Claude Fable 5.1 measured
MCP Atlas87.2%Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index140
Reasoning benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
GPQA Diamond93.4%90.9%Claude Fable 5.1
LiveBench reasoning91.7%90.6%Claude Fable 5.1
MysteryMechanism (Vals AI)47.8%Not measuredOnly Claude Fable 5.1 measured
MMMU Pro (Vals AI)90.6%86.5%Claude Fable 5.1
GPQA Diamond (Artificial Analysis run)93.7%92.5%Claude Fable 5.1
Humanity's Last Exam (Artificial Analysis run)59.1%42.9%Claude Fable 5.1
GPQA Diamond (Epoch AI run)Not measured93.3%Only GPT-5.6 Terra measured
ARC-AGI97.5%96.5%Claude Fable 5.1
ARC-AGI-290.0%83.9%Claude Fable 5.1
SimpleBenchNot measured48.9%Only GPT-5.6 Terra measured
Chess puzzles48.0%47.0%Claude Fable 5.1
Mystery game puzzles58.0%35.0%Claude Fable 5.1
EBR-bench57.1%Not measuredOnly Claude Fable 5.1 measured
LMArena Text: hard prompts15281469Claude Fable 5.1
LMArena Text: expert15441496Claude Fable 5.1
LMArena Text: hard prompts in English15221465Claude Fable 5.1
LMArena Vision: diagrams13431295Claude Fable 5.1
LMArena Vision: homework13451312Claude Fable 5.1
Kagi LLM BenchmarkNot measured51.3%Only GPT-5.6 Terra measured
Humanity's Last Exam (Scale run)51.3%Not measuredOnly Claude Fable 5.1 measured
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 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
OTIS Mock AIME100.0%99.7%Claude Fable 5.1
FrontierMath, tiers 1 to 390.2%86.0%Claude Fable 5.1
FrontierMath, tier 487.8%70.7%Claude Fable 5.1
ProofBench100.0%74.0%Claude Fable 5.1
LMArena Text: math15311465Claude Fable 5.1
LMArena Text: mathematical work15411478Claude Fable 5.1
MathArena78.1%Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index91
Knowledge benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
MMLU Pro92.4%86.7%Claude Fable 5.1
LegalBench (Vals AI)88.5%85.1%Claude Fable 5.1
CorpFin (Vals AI)Not measured65.3%Only GPT-5.6 Terra measured
TaxEval (Vals AI)76.0%76.2%GPT-5.6 Terra
MortgageTax (Vals AI)70.8%67.3%Claude Fable 5.1
MedCode (Vals AI)53.5%43.4%Claude Fable 5.1
SimpleQA Verified70.8%43.2%Claude Fable 5.1
LMArena Text: science15321452Claude Fable 5.1
LMArena Text: medicine and healthcare15311430Claude Fable 5.1
LMArena Text: legal and government15141461Claude Fable 5.1
LMArena Text: business and finance14931448Claude Fable 5.1
FACTS Benchmark SuiteNot measured52.0%Only GPT-5.6 Terra measured
PRBench Finance50.8%Not measuredOnly Claude Fable 5.1 measured
PRBench Legal51.6%Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index90
Web design benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
Design Arena: websites13121268Claude Fable 5.1
Design Arena: UI components13361256Claude Fable 5.1
Design Arena: game dev13811229Claude Fable 5.1
Design Arena: data viz13451240Claude Fable 5.1
Design Arena: 3D13921134Claude Fable 5.1
Design Arena: all code categories13351240Claude Fable 5.1
Design Arena: SVG13001219Claude Fable 5.1
Design Arena: ASCII art13231178Claude Fable 5.1
LiveBench design83.4%76.0%Claude Fable 5.1
GeneralLike-for-likePublic boards, shown as published, kept out of the index310
General benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
LiveBench data analysis80.3%79.3%Claude Fable 5.1
Public Benefits Bench (Vals AI)74.9%62.4%Claude Fable 5.1
SAGE (Vals AI)48.5%47.0%Claude Fable 5.1
MedScribe (Vals AI)91.3%82.9%Claude Fable 5.1
Vals Multimodal IndexNot measured65.1%Only GPT-5.6 Terra measured
IFBenchNot measured71.2%Only GPT-5.6 Terra measured
Long context reasoning (AA-LCR)85.3%83.0%Claude Fable 5.1
DTBench97.6%93.3%Claude Fable 5.1
LMCA65.5%54.9%Claude Fable 5.1
Surface Evolver BenchNot measured83.8%Only GPT-5.6 Terra measured
Furniture assembly70.0%54.2%Claude Fable 5.1
LMArena Text15121448Claude Fable 5.1
LMArena Text: instruction following15181456Claude Fable 5.1
LMArena Text: creative writing15091413Claude Fable 5.1
LMArena Vision13191271Claude Fable 5.1
LMArena Text: English15061449Claude Fable 5.1
LMArena Text: non-English15081441Claude Fable 5.1
LMArena Text: Chinese15841514Claude Fable 5.1
LMArena Text: German14991460Claude Fable 5.1
LMArena Text: Japanese15621454Claude Fable 5.1
LMArena Text: Korean15171427Claude Fable 5.1
LMArena Text: French15231466Claude Fable 5.1
LMArena Text: Spanish15201451Claude Fable 5.1
LMArena Text: Russian15201452Claude Fable 5.1
LMArena Text: Polish15251446Claude Fable 5.1
LMArena Text: multi-turn14931453Claude Fable 5.1
LMArena Text: longer queries15241454Claude Fable 5.1
LMArena Text: writing and language15101431Claude Fable 5.1
LMArena Text: entertainment and media14971418Claude Fable 5.1
LMArena Vision: English13131272Claude Fable 5.1
LMArena Vision: Chinese13911337Claude Fable 5.1
LMArena Vision: reading text13271278Claude Fable 5.1
LMArena Vision: humor13181236Claude Fable 5.1
LMArena Vision: creative writing13301248Claude Fable 5.1
LMArena DocumentNot measured1472Only GPT-5.6 Terra measured
EQ-Bench 4Not measured1234Only GPT-5.6 Terra 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
Image generation benchmarks for Claude Fable 5.1 and GPT-5.6 Terra
BenchmarkClaude Fable 5.1GPT-5.6 TerraLeader
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-5.6 Terra$0.0080Fits in one request

GPT-5.6 Terra costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
GPT-5.6 Terra$0.136Fits in one request

GPT-5.6 Terra costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
GPT-5.6 Terra$0.520Fits in one request

GPT-5.6 Terra 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 5.1 and GPT-5.6 Terra
SpecificationAnthropic Claude Fable 5.1OpenAI GPT-5.6 Terra
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026July 9, 2026
Context window1M1.05M
Input $/Mtok$10.00$2.00
Output $/Mtok$50.00$12.00
Coding index84.263.9
Independent measurements behind it56
Cost per solved taskNot computable$0.42
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than GPT-5.6 Terra for coding?

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 63.9 for GPT-5.6 Terra, though on 5 benchmarks against 6. Pick GPT-5.6 Terra for output tokens 4.2x cheaper ($12.00 vs $50.00 per million) and a larger context window (1.05M against 1M tokens).

Which is cheaper, Claude Fable 5.1 or GPT-5.6 Terra?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5.6 Terra costs $2.00 and $12.00. Cost per solved task is known for GPT-5.6 Terra only.

Which has the bigger context window, Claude Fable 5.1 or GPT-5.6 Terra?

GPT-5.6 Terra, with 1.05M tokens against 1M.

How many benchmarks is the Claude Fable 5.1 vs GPT-5.6 Terra comparison based on?

111 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 GPT-5.6 Terra's on 6. Where only one model has a result, the page says so instead of naming a winner.

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