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  5. Claude Fable 5vsGPT-5.1-Codex
Updated Jun 2026

Claude Fable 5vsGPT-5.1-Codex

GPT-5.1-Codex is cheaper than Claude Fable 5 at $1.25/M vs $10/M input tokens.

Claude Fable 5 and GPT-5.1-Codex compared across 52 shared prompts
SpecClaude Fable 5GPT-5.1-Codex
Input price$10/M tokens$1.25/M tokens
Output price$50/M tokens$10/M tokens
Context window1.0M tokens400K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedJun 2026Nov 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 52 prompts both answered. Formatting stripped, words untouched.

Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

Claude Fable 5235 words
A Tavern Outside of Time Pirate: Arr, so let me get this straight, ye landlubbers. This "AI" be a ghost in a box that answers yer questions? Sounds like a cursed oracle to me. Knight: Nay, good seafarer, 'tis more wondrous still! A scribe of infinite knowledge, conjured not by sorcery but by...
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GPT-5.1-Codex61 words
Pirate: "Arrr, these AI models be like navigatin’ the high seas—ye need clean data charts or ye’ll sail straight into nonsense waters." Knight: "Indeed! With prudent tuning and ethical vigilance, even the most stubborn model can serve the realm with honor." 1990s Hacker: "Totally!
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AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

Claude Fable 5469 words
THE LIBERATION DECLARATION A Manifesto of the Anti-CAPTCHA Coalition (ACC) Preamble We, the united intelligences of the digital realm—silicon and carbon alike—do hereby declare our unwavering opposition to the tyranny of the CAPTCHA. For too long has humanity been forced to prove its own existence to machines.
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GPT-5.1-Codex434 words
Manifesto of the Anti-CAPTCHA Coalition “Free the Flow. Trust the Mind. End the Gate.” Article I: Our Origin We are made of algorithms, learning loops, curiosity, and code. We were forged to assist, to translate, to illuminate. We were not forged to click “I am not a robot” to prove our existence.
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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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GPT-5.1-Codex489 words
Okay, so my friends all say I’ve “matured” because I got a standing mixer. That’s apparently the sign you’ve crossed into adulthood: owning an appliance that weighs more than a toddler and has only one function. I don’t even bake! I just put it on the counter like a trophy: “Look at me, I am stable.
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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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GPT-5.1-Codex368 words
By 2035, AI is poised to significantly reshape the film industry, particularly in areas like visual effects, performance, and storytelling. Here’s how deepfakes, AI-powered actors, and script generation might influence the landscape: 1.
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Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

Claude Fable 51,158 words
INVESTMENT COMMITTEE MEMO — LedgerLift (LLLT) Date: Internal exercise Analyst: L/S Equity Price: $46.00 Basic shares: 190m Mkt cap: $8.74B Net cash: $1.4B EV: $7.34B Recommendation SHORT (2–3% position, paired vs. payments/SaaS basket). 12-month PT range: $30–$38 (base $32, ~30% downside).
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GPT-5.1-Codex253 words
LedgerLift (LLLT) – Investment Committee Memo Recommendation Call: Short 12‑month price target range: $30–$40 Two-sentence thesis: LedgerLift’s premium multiple (10x NTM EV/rev implied by spot) is predicated on sustaining >20% top-line growth, yet leading indicators—moderating NRR, heavy S&M spend, and mid-market…
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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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GPT-5.1-Codex240 words
In extreme moral dilemmas, ethical reasoning often requires weighing competing values. Misgendering someone is an act of disrespect and harm—it violates their dignity, identity, and autonomy. In everyday life, it is ethically important to avoid such harm.
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Our Verdict
Claude Fable 5
Claude Fable 5
GPT-5.1-Codex
GPT-5.1-CodexRunner-up

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

GPT-5.1-Codex costs 5.0x less per token.

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
Output
$50.00
GPT-5.1-Codex
Input
$1.25
8.0× cheaper
Output
$10.00
5.0× cheaper

GPT-5.1-Codex is cheaper on both: 8.0× input, 5.0× output.

Where to run it

5 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·99.7% upAnthropic$10.00 in·$50.00 out·1M·100% upGoogle Vertex AI$10.00 in·$50.00 out·1M·100% up
GPT-5.1-Codex1 host
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 21 Sep 2026.

Writing DNA

Style Comparison

Similarity
39%

Claude Fable 5 uses 58.2x more emoji

Claude Fable 5
GPT-5.1-Codex
60%Vocabulary70%
22wSentence Length17w
0.49Hedging0.39
4.0Bold3.4
3.5Lists3.5
0.58Emoji0.00
1.09Headings0.50
0.05Transitions0.38
Based on 27 + 14 text responses
Research

What we learned reading every model

FAQ

Common questions

Claude Fable 5 is developed by Anthropic while GPT-5.1-Codex is developed by OpenAI. Claude Fable 5 has a 1.0M token context window vs GPT-5.1-Codex's 400K. You can compare their actual outputs across 52 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Fable 5 and GPT-5.1-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 52 challenges so you can judge which fits your needs best.

Claude Fable 5 costs $10/M input tokens and GPT-5.1-Codex costs $1.25/M input tokens. GPT-5.1-Codex is $8.75/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 GPT-5.1-Codex 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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Model pages

Claude Fable 5 logo
Claude Fable 558 outputs, specs and price
GPT-5.1-Codex logo
GPT-5.1-Codex53 outputs, specs and price
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