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Claude Opus 5.5 vs Mercury 2

Claude Opus 5.5 leads the LLM Stats Score 60.4 to 23.1. Mercury 2 is 21.3x cheaper per token.

Anthropic · Inception · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 60.4 to 23.1, ranking #1 overall.

On price, Mercury 2 is roughly 21.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Opus 5.5 also accepts a larger context window (1,000,000 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 60.4 and ranks #1 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Mercury 2

  • cost matters — it's about 21.3x cheaper per token

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
Mercury 2
Inception
Core performance indexes
LLM Stats Score
60.4
#1
23.1
#199
Reasoning
59.5
#1
22.2
#194
Coding
49.9
#1
11.9
#173
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
$0.25 / M
Output price
$20.00 / M
$0.75 / M
Context window
1,000,000
128,000

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Claude Opus 5.5
Mercury 2
Math
41.8#6
22.8#144
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 6 for Mercury 2

No common benchmarks found

Claude Opus 5.5 and Mercury 2don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Mercury 2 costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 16.0x more expensive than Mercury 2 ($0.25/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 26.7x more expensive than Mercury 2 ($0.75/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than Mercury 2.*

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

Lowest available price from all providers
Sat Oct 24 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
Inception
Mercury 2
Input tokens$0.25
Output tokens$0.75
Best providerInception
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Claude Opus 5.5 accepts 1,000,000 input tokens compared to Mercury 2's 128,000 tokens. Claude Opus 5.5 can generate longer responses up to 128,000 tokens, while Mercury 2 is limited to 8,192 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
Inception
Mercury 2
Input128,000 tokens
Output8,192 tokens
Sat Oct 24 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Opus 5.5 supports multimodal inputs, whereas Mercury 2 does not.

Claude Opus 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Opus 5.5

Text
Images
Audio
Video

Mercury 2

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Opus 5.5

Proprietary

Closed source

Mercury 2

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while Mercury 2 was released on 2026-02-24.

Claude Opus 5.5 is 7 months newer than Mercury 2.

Claude Opus 5.5

Sep 22, 2026

4 weeks ago

7mo newer
Mercury 2

Feb 24, 2026

7 months ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a documented knowledge cutoff of 2026-06-01, while Mercury 2'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 Mercury 2's cutoff date.

Claude Opus 5.5

Jun 2026

Mercury 2

—

Provider Availability

Claude Opus 5.5 is available from Anthropic. Mercury 2 is available from Inception.

Claude Opus 5.5

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

Mercury 2

inception logo
Inception
Input Price:Input: $0.25/1MOutput Price:Output: $0.75/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and Mercury 2 side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
Mercury 2
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs Mercury 2.

Which is better, Claude Opus 5.5 or Mercury 2?

Claude Opus 5.5 leads the LLM Stats Score 60.4 to 23.1. Claude Opus 5.5 is made by Anthropic and Mercury 2 is made by Inception. 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 Mercury 2 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%. Mercury 2 scores AIME 2025: 91.1%, GPQA: 74.0%, IFBench: 71.0%, LiveCodeBench: 67.0%, Tau2 Airline: 53.0%.

Is Claude Opus 5.5 cheaper than Mercury 2?

Mercury 2 is 16.0x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. Mercury 2 costs $0.25/M input and $0.75/M output via inception.

What are the context window sizes for Claude Opus 5.5 and Mercury 2?

Claude Opus 5.5 supports 1.0M tokens and Mercury 2 supports 128K 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 Mercury 2?

Key differences include LLM Stats Score (60.4 vs 23.1), context window (1.0M vs 128K), input pricing ($4.00 vs $0.25/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and Mercury 2?

Claude Opus 5.5 is developed by Anthropic and Mercury 2 is developed by Inception.

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