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  5. Claude Fable 5.1vsMercury 2.5
Updated Sep 2026

Claude Fable 5.1vsMercury 2.5

Mercury 2.5 is cheaper than Claude Fable 5.1 at $0.04/M vs $10/M input tokens.

Claude Fable 5.1 and Mercury 2.5 compared across 3 shared prompts
SpecClaude Fable 5.1Mercury 2.5
Input price$10/M tokens$0.04/M tokens
Output price$50/M tokens$0.15/M tokens
Context window1.0M tokens260K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Sep 2026
Our Verdict
Claude Fable 5.1
Claude Fable 5.1
Mercury 2.5
Mercury 2.5Runner-up

Not enough votes to call it. On the specs, Claude Fable 5.1 has the edge: bigger model tier, bigger context window, major provider backing.

Mercury 2.5 costs 333x less per token.

Slight edge

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Fable 5.1
Input
$10.00
Output
$50.00
Mercury 2.5
Input
$0.04
250× cheaper
Output
$0.15
333× cheaper

Mercury 2.5 is cheaper on both: 250× input, 333× output.

Where to run it

5 hosts

Claude Fable 5.14 hosts
HostInOutContextUptime
Amazon Bedrock$10.00 in·$50.00 out·1M—Anthropic$10.00 in·$50.00 out·1M·99.7% upAzure AI Foundry$10.00 in·$50.00 out·1M·99.8% upGoogle Vertex AI$10.00 in·$50.00 out·1M·99.8% up
Mercury 2.51 host
HostInOutContextUptime
Inception$0.04 in·$0.15 out·260k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Claude Fable 5.1 is developed by Anthropic while Mercury 2.5 is developed by Inception. Claude Fable 5.1 has a 1.0M token context window vs Mercury 2.5's 260K. You can compare their actual outputs across 3 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Fable 5.1 and Mercury 2.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 3 challenges so you can judge which fits your needs best.

Claude Fable 5.1 costs $10/M input tokens and Mercury 2.5 costs $0.04/M input tokens. Mercury 2.5 is $9.96/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 5.1 and Mercury 2.5 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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