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Claude Opus 5.5 vs DeepSeek-V4.1-Flash

Claude Opus 5.5 leads the LLM Stats Score 59.8 to 51.6. DeepSeek-V4.1-Flash is 24.2x cheaper per token.

Anthropic · DeepSeek · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.8 to 51.6, ranking #1 overall.

In the 6 individual benchmarks reported for both models, Claude Opus 5.5 wins 4; this is a narrower head-to-head signal than the composite indexes.

On price, DeepSeek-V4.1-Flash is roughly 24.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

DeepSeek-V4.1-Flash also accepts a larger context window (1,040,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Opus 5.5

  • overall performance matters — it scores 59.8 and ranks #1 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 4 of 6 exact shared results
  • you want the most recent training data — it shipped Sep 2026

Choose DeepSeek-V4.1-Flash

  • cost matters — it's about 24.2x cheaper per token
  • you process long inputs — it offers a 1,040,000 token context window
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
DeepSeek-V4.1-Flash
DeepSeek
Core performance indexes
LLM Stats Score
59.8
#1
51.6
#13
Reasoning
57.9
#1
48.9
#17
Coding
51.8
#1
43.4
#6
Agents
44.6
#2
40.4
#4
Cost, coverage & limits
Benchmark wins
4 of 6
2 of 6
Input price
$4.00 / M
$0.22 / M
Output price
$20.00 / M
$0.66 / M
Context window
1,000,000
1,040,000

Capability indexes

Additional strengths measured across groups of related public benchmarks

4 shared
Index
Claude Opus 5.5
DeepSeek-V4.1-Flash
Math
42.5#5
35.0#45
Vision
42.9#1
30.8#29
Tool use
32.9#2
32.0#3
Multimodal
42.6#1
35.3#12
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 20 for DeepSeek-V4.1-Flash

6 shared

Claude Opus 5.5 outperforms in 4 benchmarks (Chartography, Humanity's Last Exam (no tools, text-only), Program Bench, Terminal-Bench 4.0), while DeepSeek-V4.1-Flash is better at 1 benchmark (AutomationBench).

Claude Opus 5.5 shows notably better performance in the majority of benchmarks.

Tue Sep 22 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

DeepSeek-V4.1-Flash costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 18.2x more expensive than DeepSeek-V4.1-Flash ($0.22/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 30.3x more expensive than DeepSeek-V4.1-Flash ($0.66/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than DeepSeek-V4.1-Flash.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Tue Sep 22 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
DeepSeek
DeepSeek-V4.1-Flash
Input tokens$0.22
Output tokens$0.66
Best providerFireworks
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

DeepSeek-V4.1-Flash accepts 1,040,000 input tokens compared to Claude Opus 5.5's 1,000,000 tokens. DeepSeek-V4.1-Flash can generate longer responses up to 393,216 tokens, while Claude Opus 5.5 is limited to 128,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
DeepSeek
DeepSeek-V4.1-Flash
Input1,040,000 tokens
Output393,216 tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and DeepSeek-V4.1-Flash support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Opus 5.5

Text
Images
Audio
Video

DeepSeek-V4.1-Flash

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Opus 5.5 is licensed under a proprietary license, while DeepSeek-V4.1-Flash uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Opus 5.5

Proprietary

Closed source

DeepSeek-V4.1-Flash

MIT

Open weights

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while DeepSeek-V4.1-Flash was released on 2026-09-10.

Claude Opus 5.5 is 0 month newer than DeepSeek-V4.1-Flash.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1w newer
DeepSeek-V4.1-Flash

Sep 10, 2026

1 weeks ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a documented knowledge cutoff of 2026-06-01, while DeepSeek-V4.1-Flash's cutoff date is not specified.

We can confirm Claude Opus 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without DeepSeek-V4.1-Flash's cutoff date.

Claude Opus 5.5

Jun 2026

DeepSeek-V4.1-Flash

—

Provider Availability

Claude Opus 5.5 is available from Anthropic. DeepSeek-V4.1-Flash is available from Fireworks, DeepInfra, DeepSeek, Novita.

Claude Opus 5.5

anthropic logo
Anthropic
Input Price:Input: $4.00/1MOutput Price:Output: $20.00/1M

DeepSeek-V4.1-Flash

fireworks logo
Fireworks
Input Price:Input: $0.22/1MOutput Price:Output: $0.66/1M
deepinfra logo
Deepinfra
Input Price:Input: $0.30/1MOutput Price:Output: $1.20/1M
deepseek logo
DeepSeek
Input Price:Input: $0.30/1MOutput Price:Output: $1.20/1M
novita logo
Novita
Input Price:Input: $0.30/1MOutput Price:Output: $1.20/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and DeepSeek-V4.1-Flash side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
DeepSeek-V4.1-Flash
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs DeepSeek-V4.1-Flash.

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

Claude Opus 5.5 leads the LLM Stats Score 59.8 to 51.6. Claude Opus 5.5 is made by Anthropic and DeepSeek-V4.1-Flash is made by DeepSeek. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Opus 5.5 compare to DeepSeek-V4.1-Flash in benchmarks?

Claude Opus 5.5 scores BenchCAD (with Python tool): 96.2%, Global-MMLU: 94.3%, SWE-bench Multilingual: 93.9%, MILU: 93.1%, ArXivMath: 91.2%. DeepSeek-V4.1-Flash scores CodeForces: 100.0%, GPQA: 90.9%, Terminal-Bench 2.1: 90.6%, BabyVision: 89.6%, CyberGym: 88.1%.

Is Claude Opus 5.5 cheaper than DeepSeek-V4.1-Flash?

DeepSeek-V4.1-Flash is 18.2x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. DeepSeek-V4.1-Flash costs $0.22/M input and $0.66/M output via fireworks.

What are the context window sizes for Claude Opus 5.5 and DeepSeek-V4.1-Flash?

Claude Opus 5.5 supports 1.0M tokens and DeepSeek-V4.1-Flash supports 1.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Opus 5.5 and DeepSeek-V4.1-Flash?

Key differences include LLM Stats Score (59.8 vs 51.6), context window (1.0M vs 1.0M), input pricing ($4.00 vs $0.22/M), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and DeepSeek-V4.1-Flash?

Claude Opus 5.5 is developed by Anthropic and DeepSeek-V4.1-Flash is developed by DeepSeek.

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