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Comparison · 3 models · Updated Oct 4, 2026

Claude Opus 4.5 vs Claude Fable 5 vs GPT-5.1

Claude Fable 5 comes out ahead, 65 to 60 and 55 on our weighted score, though GPT-5.1 is 5.8× cheaper per token.

  1. Anthropic

    Claude Opus 4.5

    Released Nov 24, 2025

    55/100
    • ECI150.1
    • Price$5.00 / $25.00
    • Context200K
    Full specs Remove Claude Opus 4.5
  2. Our pick

    Anthropic

    Claude Fable 5

    Released Jun 9, 2026

    65/100
    • ECI162.2
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5

  3. OpenAI

    GPT-5.1

    Released Nov 13, 2025

    60/100
    • ECI149.7
    • Price$1.25 / $10.00
    • Context400K
    Full specs Remove GPT-5.1
01 — Verdict

Claude Fable 5 is our pick

Claude Fable 5 is the better all-round choice, scoring 65/100 against GPT-5.1 (60) and Claude Opus 4.5 (55). It leads on capability and context window. GPT-5.1 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Fable 5Capabilities Index (ECI): Claude Fable 5 162.2 · Claude Opus 4.5 150.1 · GPT-5.1 149.7
  • Lowest priceGPT-5.1GPT-5.1 $3.44 · Claude Opus 4.5 $10.00 · Claude Fable 5 $20.00 per 1M tokens (3:1 blend)
  • Longest contextClaude Fable 5Claude Fable 5 1,000,000 · GPT-5.1 400,000 · Claude Opus 4.5 200,000 tokens
  • Widest inputsClaude Opus 4.5 and Claude Fable 5Claude Opus 4.5: Text, Images, PDFs · Claude Fable 5: Text, Images, PDFs · GPT-5.1: Text, Images
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightClaude Opus 4.5Claude Fable 5GPT-5.1
CapabilityCapabilities Index (ECI)50%789478
Price25%2024
Inputs & features15%808070
Context window10%326044
Overall100%55/10065/10060/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Claude Opus 4.5 vs Claude Fable 5 vs GPT-5.1 specifications side by side
SpecificationClaude Opus 4.5AnthropicClaude Fable 5AnthropicGPT-5.1OpenAI
Capability
Capabilities Index (ECI)150.1162.2 (best)149.7
ECI rank#48 of 148#7 of 148 (best)#52 of 148
GPQA DiamondGraduate-level science questions86.1%85.9%87.6% (best)
FrontierMath Tiers 1–3Research-level mathematics34.4%87.0% (best)—
OTIS Mock AIME 2024–2025Competition mathematics86.1%100% (best)88.6%
SWE-bench VerifiedFixing real GitHub issues76.7% (best)—68.0%
SimpleQA VerifiedShort factual questions45.7%70.7% (best)48.0%
Price per million tokens
Input$5.00$10.00$1.25 (best)
Output$25.00$50.00$10.00 (best)
Cached input$0.50$1.00$0.125 (best)
Blended (3:1)$10.00$20.00$3.44 (best)
Long-context rateSame rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Anthropic APIOfficial OpenAI API
Limits
Context window200,000 tokens1,000,000 tokens (best)400,000 tokens
Max output64,000 tokens128,000 tokens (best)128,000 tokens (best)
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesYesNo
AudioNoNoNo
VideoNoNoNo
ReasoningYeslow · medium · highYeslow · medium · high · xhigh · maxYeslow · medium · high
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDclaude-opus-4-5claude-fable-5gpt-5.1
API providers2838 (best)21
ReleasedNov 24, 2025Jun 9, 2026Nov 13, 2025
Knowledge cutoffMay 2025Jan 31, 2026Sep 30, 2024
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Claude Opus 4.5$100.00
  • Claude Fable 5$200.00
  • GPT-5.1$32.50
04 — Questions

Which should you choose?

Which is better: Claude Opus 4.5, Claude Fable 5 or GPT-5.1?

Claude Fable 5 is the better all-round choice, scoring 65/100 against GPT-5.1 (60) and Claude Opus 4.5 (55). It leads on capability and context window. GPT-5.1 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Opus 4.5, Claude Fable 5 or GPT-5.1?

GPT-5.1 is cheaper at $1.25 input / $10.00 output per million tokens (official OpenAI API price). Claude Opus 4.5 costs $5.00 input / $25.00 output per million tokens (official Anthropic API price); Claude Fable 5 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $3.44 per million tokens for GPT-5.1 versus $10.00 for Claude Opus 4.5 (2.9× as much) and $20.00 for Claude Fable 5 (5.8× as much).

Which scores higher on benchmarks?

Claude Fable 5 scores higher on the Capabilities Index (ECI): Claude Fable 5 162.2 (#7 of 148), Claude Opus 4.5 150.1 (#48 of 148) and GPT-5.1 149.7 (#52 of 148). Their confidence ranges do not overlap (159.6–166.1 vs 147.9–153.0), so the gap is a real one. On individual benchmarks: GPQA Diamond — GPT-5.1 87.6%, Claude Opus 4.5 86.1%, Claude Fable 5 85.9%; OTIS Mock AIME 2024–2025 — Claude Fable 5 100%, GPT-5.1 88.6%, Claude Opus 4.5 86.1%; SimpleQA Verified — Claude Fable 5 70.7%, GPT-5.1 48.0%, Claude Opus 4.5 45.7%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Fable 5 yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5 leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.

Which has the bigger context window?

Claude Fable 5 has the largest context window at 1,000,000 tokens, against 400,000 for GPT-5.1 and 200,000 for Claude Opus 4.5. Maximum output per response: Claude Opus 4.5 up to 64,000, Claude Fable 5 up to 128,000, GPT-5.1 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Opus 4.5 accepts text, images and PDFs; Claude Fable 5 accepts text, images and PDFs; GPT-5.1 accepts text and images. Claude Opus 4.5 handles the widest range of inputs.

Are any of these open source?

No. Claude Opus 4.5, Claude Fable 5 and GPT-5.1 are proprietary and only available through APIs and apps.

Which is newer?

Claude Fable 5 is the newest, released Jun 9, 2026. Claude Opus 4.5 came out Nov 24, 2025; GPT-5.1 came out Nov 13, 2025. Knowledge cutoff: Claude Opus 4.5 May 2025, Claude Fable 5 Jan 31, 2026, GPT-5.1 Sep 30, 2024.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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