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Head-to-head comparison

Claude Fable 5.1 vs GPT-5.5

Claude Fable 5.1 (Anthropic) and GPT-5.5 (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 3 September 2026

As of 3 September 2026, Claude Fable 5.1 holds the stronger ModelCap Index position (#2 vs #9); and GPT-5.5 is 1.7× cheaper per output token ($30.00/1M vs $50.00/1M).

Which should you choose?

Choose Claude Fable 5.1 if…

  • you want the stronger overall ModelCap Index position — #2 against #9 (84.1 vs 77.9 points).
  • you want provider choice — 4 listed API providers against 3.
  • ARC-AGI-2 is your yardstick — 90.0% against 85.0%.
  • AA Intelligence Index is your yardstick — 65.7 against 56.3.
  • AA Terminal-Bench 2.1 is your yardstick — 91.4% against 84.3%.
  • AA Humanity's Last Exam is your yardstick — 59.1% against 45.8%.
  • you want the more recently listed model — Claude Fable 5.1 was listed 1 September 2026, GPT-5.5 24 April 2026.

Choose GPT-5.5 if…

  • API cost matters — $30.00/1M output tokens against $50.00/1M, about 1.7× cheaper.
  • your workload is prompt-heavy — input tokens cost $5.00/1M against $10.00/1M.

Claude Fable 5.1 vs GPT-5.5: specs, pricing and context

Specification comparison of Claude Fable 5.1 and GPT-5.5
FieldClaude Fable 5.1AnthropicGPT-5.5OpenAI
ModelCap Index position#2#9
Index score84.177.9
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$5.00
Output price / 1M tokens$50.00$30.00
Context window1M tokens1M tokens
Max output tokens128K128K
API providers listed43
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileFile, Image, Text
First listed1 September 202624 April 2026
PublisherAnthropicOpenAI

Evidence: 2 public benchmark observations across 2 boards · 7 public benchmark observations across 7 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5.1 vs GPT-5.5

Public benchmark boards where Claude Fable 5.1 or GPT-5.5 has a published result
BoardClaude Fable 5.1GPT-5.5Leads
Arena codingArena (LMArena)—15201514–1526HighOnly one result
LMArena AgentLMArena—7.9%6.8%–9.0%X-HighOnly one result
ARC-AGI-2ARC Prize Foundation90.0%Max85.0%X-HighClaude Fable 5.1
ARC-AGI-3ARC Prize Foundation—0.4%HighOnly one result
AA Intelligence IndexArtificial Analysis65.7intelligence-index56.3intelligence-indexClaude Fable 5.1
AA Terminal-Bench 2.1Artificial Analysis91.4%terminal-bench-2.184.3%terminal-bench-2.1Claude Fable 5.1
AA τ²-Bench TelecomArtificial Analysis—93.9%tau2-bench-telecomOnly one result
AA Humanity's Last ExamArtificial Analysis59.1%humanitys-last-exam45.8%humanitys-last-examClaude Fable 5.1
WildClawBench OpenClawWildClawBench—58.2Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Fable 5.1 vs GPT-5.5: common questions

Is Claude Fable 5.1 better than GPT-5.5?

Claude Fable 5.1 ranks higher on the ModelCap Index as of 3 September 2026: #2 against #9. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is Claude Fable 5.1 cheaper than GPT-5.5?

GPT-5.5 is cheaper on output tokens: $30.00/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5.1 and $5.00/1M for GPT-5.5. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Fable 5.1 or GPT-5.5?

Both publish a 1M-token context window.

Which is better for coding, Claude Fable 5.1 or GPT-5.5?

AA Terminal-Bench 2.1: Claude Fable 5.1 91.4%, GPT-5.5 84.3% — Claude Fable 5.1 leads.

Are Claude Fable 5.1 and GPT-5.5 open-weight models?

Claude Fable 5.1: API only. GPT-5.5: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Fable 5.1 and GPT-5.5?

ModelCap currently lists 4 API providers for Claude Fable 5.1 and 3 for GPT-5.5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5.1 vs GPT-5.5 comparison?

Every figure comes from the sealed ModelCap dataset published 3 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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