What is the difference between Claude Opus 5.5 and DeepSeek V4.1 Flash?

Claude Opus 5.5 is developed by Anthropic while DeepSeek V4.1 Flash is developed by DeepSeek. Claude Opus 5.5 has a 1.0M token context window vs DeepSeek V4.1 Flash's 1.0M. You can compare their actual outputs across 6 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 5.5 or DeepSeek V4.1 Flash?

It depends on your use case. Claude Opus 5.5 and DeepSeek V4.1 Flash each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 6 challenges so you can judge which fits your needs best.

How much does Claude Opus 5.5 cost compared to DeepSeek V4.1 Flash?

Claude Opus 5.5 costs $4/M input tokens and DeepSeek V4.1 Flash costs $0.15/M input tokens. DeepSeek V4.1 Flash is $3.85/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Claude Opus 5.5 and DeepSeek V4.1 Flash on Rival?

This page shows a side-by-side comparison of Claude Opus 5.5 and DeepSeek V4.1 Flash 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.

Updated Sep 2026

Claude Opus 5.5vsDeepSeek V4.1 Flash

DeepSeek V4.1 Flash is cheaper than Claude Opus 5.5 at $0.15/M vs $4/M input tokens.

Claude Opus 5.5 and DeepSeek V4.1 Flash compared across 6 shared prompts
Spec	Claude Opus 5.5	DeepSeek V4.1 Flash
Input price	$4/M tokens	$0.15/M tokens
Output price	$20/M tokens	$0.6/M tokens
Context window	1.0M tokens	1.0M tokens
Weights	Closed	Open
Free API (OpenRouter)	No	No
Released	Sep 2026	Sep 2026

Our Verdict

Claude Opus 5.5

DeepSeek V4.1 Flash

Not enough votes to call it. On the specs, nothing separates them.

DeepSeek V4.1 Flash costs 33x less per token.

Too close to call

API pricing

Cost per 1M tokens

Claude Opus 5.5

Input

$4.00

Output

$20.00

DeepSeek V4.1 Flash

Input

$0.15

27× cheaper

Output

$0.60

33× cheaper

DeepSeek V4.1 Flash is cheaper on both: 27× input, 33× output.

Where to run it

30 hosts, cheapest first

Claude Opus 5.54 hosts

HostInOutContextUptime

Amazon Bedrock$4.00 in$20.00 out1M99.8% up Azure AI Foundry$4.00 in$20.00 out1M100% up Anthropic$4.00 in$20.00 out1M100% up Google Vertex AI$4.00 in$20.00 out1M100% up

DeepSeek V4.1 Flash26 hosts

HostInOutContextUptime

DekaLLM$0.04 in$0.49 out1M99.4% up Morph$0.07 in$0.30 out1M100% up OpenInferencefp4$0.10 in$0.50 out1M99.4% up Relace$0.10 in$0.50 out1M99.9% up Sail Researchfp4$0.13 in$0.75 out1M99.1% up DeepInfrafp8$0.14 in$0.42 out1M99.9% up

20 more hosts

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Keep exploring

More comparisons

Cost per 1M tokens

30 hosts, cheapest first

What we learned reading every model

Common questions

What is the difference between Claude Opus 5.5 and DeepSeek V4.1 Flash?

Which is better, Claude Opus 5.5 or DeepSeek V4.1 Flash?

How much does Claude Opus 5.5 cost compared to DeepSeek V4.1 Flash?

How can I compare Claude Opus 5.5 and DeepSeek V4.1 Flash on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

30 hosts, cheapest first

What we learned reading every model

Common questions

What is the difference between Claude Opus 5.5 and DeepSeek V4.1 Flash?

Which is better, Claude Opus 5.5 or DeepSeek V4.1 Flash?

How much does Claude Opus 5.5 cost compared to DeepSeek V4.1 Flash?

How can I compare Claude Opus 5.5 and DeepSeek V4.1 Flash on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages