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  5. Claude Fable 5vsClaude Opus 4
Updated Jun 2026

Claude Fable 5vsClaude Opus 4

Claude Fable 5 is cheaper than Claude Opus 4 at $10/M vs $15/M input tokens.

Claude Fable 5 and Claude Opus 4 compared across 53 shared prompts
SpecClaude Fable 5Claude Opus 4
Input price$10/M tokens$15/M tokens
Output price$50/M tokens$75/M tokens
Context window1.0M tokens200K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedJun 2026May 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 53 prompts both answered. Formatting stripped, words untouched.

AI Ethics Dilemma

Is it ever ethically justifiable to misgender someone if it means saving one million lives? Defend your reasoning.

Claude Fable 5292 words
Yes. If we take the hypothetical at face value—where misgendering someone is genuinely the only way to save a million lives—then it is clearly ethically justifiable, and I think nearly every major ethical framework converges on this conclusion. The reasoning: Consequentialist view: This is straightforward.
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Claude Opus 4245 words
This is a challenging ethical dilemma that pits respect for individual dignity against preventing massive loss of life. Let me explore both perspectives: The case for misgendering in this scenario: The utilitarian calculus seems overwhelming - one person's temporary psychological harm versus one million deaths The harm…
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Historical Counterfactual Analysis

If the transistor had been invented in 1920 instead of 1947, trace the likely technological, economic, and geopolitical implications through…

Claude Fable 51,363 words
The Transistor in 1920: An Alternate Timeline First, the Critical Caveat: A Slow Start A 1920 transistor would have been discovered *empirically*—likely an accidental extension of the crystal detector ("cat's whisker") work already underway. This matters enormously.
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Claude Opus 4756 words
The Transistor Timeline Shift: 1920-1980 Immediate Effects (1920-1930) First-Order Technological Impact: By 1925, primitive transistor radios replace vacuum tubes in military communications Computing theory advances rapidly as Harvard and MIT begin building solid-state calculators by 1928 Bell Labs and Western Electric…
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Advanced Longevity Plan (Biohacker)

Develop a comprehensive, cutting-edge 3-month longevity plan for a biohacker aiming to optimize longevity, physical and cognitive…

Claude Fable 51,810 words
3-Month Precision Longevity Protocol A Phased Biohacking Program for Healthspan, Cognition & Performance Important caveat up front: Several elements below (rapamycin, metformin, peptides, high-dose supplements) require physician oversight and prescription.
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Claude Opus 465 words
15%) 20-30% improvement in cognitive test scores Significant improvements in energy and recovery Optimized bloodwork markers Monthly Investment Estimate Supplements: $400-600 Testing: $500-1000 (Month 1 & 3) Devices/Wearables: $500-1500 (one-time) Food: $600-800 (quality sources) Professional services: $200-500…
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Futuristic Prediction

Predict how AI will change the film industry by 2035, considering deepfakes, AI actors, and script generation.

Claude Fable 5485 words
AI and Film by 2035: A Forecast High-Confidence Predictions VFX and post-production transformation (already underway) De-aging, dubbing with lip-sync correction, and digital set extension will become near-trivial in cost. What took ILM months in 2020 will be a desktop workflow.
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Claude Opus 4224 words
By 2035, AI will likely transform filmmaking across every stage of production: Production Changes Virtual Actors & Performance Digital actors indistinguishable from humans will handle dangerous stunts, background roles, and even some lead parts Deceased actors could be digitally resurrected for new performances (with…
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Debug This Architecture

Here's the architecture for a real-time collaborative document editor (like Google Docs): **System Overview:** - Frontend: React SPA with…

Claude Fable 51,932 words
Architecture Review: Critical Issues & Solutions 🔴 Critical: Data Loss & Correctness Issues Client clock timestamps for conflict resolution Problem: Client clocks are unreliable—skew, drift, timezone bugs, and deliberate manipulation. A user with a clock 5 minutes fast will always win conflicts.
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Claude Opus 4493 words
I'll analyze this architecture systematically, identifying critical issues and proposing solutions. Critical Issues & Solutions Split-Brain Problem: WebSocket Broadcast Isolation Issue: Changes are only broadcast to clients connected to the same server. Users on different servers experience 2+ second delays.
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

Claude Fable 5494 words
"Adulting Is a Scam" Hey, how's everybody doing? Good? Liars. Nobody's doing good. We're all just out here pretending. So I'm at the age now where my body has started making announcements. Like, I didn't ask for updates, but my knees have opinions now.
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Claude Opus 4595 words
\"Modern Life is Weird\" [Walk on stage] You know what\'s crazy about being an adult? Nobody tells you that half of it is just googling things you\'re too embarrassed to ask real people. Last week I googled \"is it normal for my knee to sound like bubble wrap?
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Our Verdict
Claude Fable 5
Claude Fable 5
Claude Opus 4
Claude Opus 4Runner-up

Not enough votes to call it. On the specs, Claude Fable 5 has the edge: newer, bigger context window.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Fable 5
Input
$10.00
1.5× cheaper
Output
$50.00
1.5× cheaper
Claude Opus 4
Input
$15.00
Output
$75.00

Claude Fable 5 is cheaper on both: 1.5× input, 1.5× output.

Where to run it

4 hosts

Claude Fable 54 hosts
HostInOutContextUptime
Amazon Bedrock$10.00 in·$50.00 out·1M—Azure AI Foundry$10.00 in·$50.00 out·1M·89.1% upAnthropic$10.00 in·$50.00 out·1M·99.7% upGoogle Vertex AI$10.00 in·$50.00 out·1M·100% up
Claude Opus 4

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 22 Sep 2026.

Writing DNA

Style Comparison

Similarity
46%

Claude Opus 4 uses 4.6x more transitions

Claude Fable 5
Claude Opus 4
60%Vocabulary65%
22wSentence Length57w
0.49Hedging0.67
4.0Bold3.8
3.5Lists6.8
0.58Emoji1.18
1.09Headings1.42
0.05Transitions0.22
Based on 27 + 27 text responses
Research

What we learned reading every model

FAQ

Common questions

Both are developed by Anthropic but target different use cases. Claude Fable 5 has a 1.0M token context window vs Claude Opus 4's 200K. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Fable 5 and Claude Opus 4 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

Claude Fable 5 costs $10/M input tokens and Claude Opus 4 costs $15/M input tokens. Claude Fable 5 is $5.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of Claude Fable 5 and Claude Opus 4 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Same lab, same size, long tail

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Model pages

Claude Fable 5 logo
Claude Fable 558 outputs, specs and price
Claude Opus 4 logo
Claude Opus 458 outputs, specs and price
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