ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Claude Opus 4.8 vs Claude Fable 5.1

Claude Fable 5.1 comes out ahead, 66 to 63 on our weighted score, though Claude Opus 4.8 is 2× cheaper per token.

  1. Anthropic

    Claude Opus 4.8

    Released May 28, 2026

    63/100
    • ECI158.3
    • Price$5.00 / $25.00
    • Context1M
    Full specs Remove Claude Opus 4.8
  2. Our pick

    Anthropic

    Claude Fable 5.1

    Released Sep 1, 2026

    66/100
    • ECI164.8
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5.1

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Claude Fable 5.1 is our pick

Claude Fable 5.1 is the better all-round choice, scoring 66/100 against Claude Opus 4.8 (63). It leads on capability. Claude Opus 4.8 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Fable 5.1Capabilities Index (ECI): Claude Fable 5.1 164.8 · Claude Opus 4.8 158.3
  • Lowest priceClaude Opus 4.8Claude Opus 4.8 $10.00 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameClaude Opus 4.8 1,000,000 · Claude Fable 5.1 1,000,000 tokens
  • Widest inputsSame inputsClaude Opus 4.8: Text, Images, PDFs · Claude Fable 5.1: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightClaude Opus 4.8Claude Fable 5.1
CapabilityCapabilities Index (ECI)50%8997
Price25%20
Inputs & features15%8080
Context window10%6060
Overall100%63/10066/100
02 — Side by side

Every spec in one table

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

Claude Opus 4.8 vs Claude Fable 5.1 specifications side by side
SpecificationClaude Opus 4.8AnthropicClaude Fable 5.1Anthropic
Capability
Capabilities Index (ECI)158.3164.8 (best)
ECI rank#12 of 148#4 of 148 (best)
GPQA DiamondGraduate-level science questions91.0%—
FrontierMath Tiers 1–3Research-level mathematics80.0%90.2% (best)
OTIS Mock AIME 2024–2025Competition mathematics98.3%100% (best)
SimpleQA VerifiedShort factual questions53.0%70.8% (best)
Price per million tokens
Input$5.00 (best)$10.00
Output$25.00 (best)$50.00
Cached input$0.50$0.25 (best)
Blended (3:1)$10.00 (best)$20.00
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Anthropic API
Limits
Context window1,000,000 tokens1,000,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDclaude-opus-4-8claude-fable-5-1
API providers45 (best)29
ReleasedMay 28, 2026Sep 1, 2026
Knowledge cutoffJan 2026Jun 2026
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 4.8$100.00
  • Claude Fable 5.1$200.00
04 — Questions

Which should you choose?

Which is better: Claude Opus 4.8 or Claude Fable 5.1?

Claude Fable 5.1 is the better all-round choice, scoring 66/100 against Claude Opus 4.8 (63). It leads on capability. Claude Opus 4.8 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Opus 4.8 or Claude Fable 5.1?

Claude Opus 4.8 is cheaper at $5.00 input / $25.00 output per million tokens (official Anthropic API price). Claude Fable 5.1 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 $10.00 per million tokens for Claude Opus 4.8 versus $20.00 for Claude Fable 5.1 (2× as much).

Which scores higher on benchmarks?

Claude Fable 5.1 scores higher on the Capabilities Index (ECI): Claude Fable 5.1 164.8 (#4 of 148) and Claude Opus 4.8 158.3 (#12 of 148). Their confidence ranges do not overlap (161.8–169.1 vs 156.1–160.7), so the gap is a real one. On individual benchmarks: FrontierMath Tiers 1–3 — Claude Fable 5.1 90.2%, Claude Opus 4.8 80.0%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, Claude Opus 4.8 98.3%; SimpleQA Verified — Claude Fable 5.1 70.8%, Claude Opus 4.8 53.0%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Opus 4.8 and Claude Fable 5.1 yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5.1 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Claude Opus 4.8 and Claude Fable 5.1 share the same 1,000,000-token context window. Maximum output per response: Claude Opus 4.8 up to 128,000, Claude Fable 5.1 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Opus 4.8 accepts text, images and PDFs; Claude Fable 5.1 accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. Claude Opus 4.8 and Claude Fable 5.1 are proprietary and only available through APIs and apps.

Which is newer?

Claude Fable 5.1 is the newest, released Sep 1, 2026. Claude Opus 4.8 came out May 28, 2026. Knowledge cutoff: Claude Opus 4.8 Jan 2026, Claude Fable 5.1 Jun 2026.

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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