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Claude Sonnet 5.5 vs Mercury 3

Claude Sonnet 5.5 leads the LLM Stats Score 58.4 to 36.1. Mercury 3 is 24.6x cheaper per token.

Anthropic · Inception · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.4 to 36.1, ranking #2 overall.

On price, Mercury 3 is roughly 24.6x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

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

Choose Claude Sonnet 5.5

  • overall performance matters — it scores 58.4 and ranks #2 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes

Choose Mercury 3

  • cost matters — it's about 24.6x cheaper per token
  • you want the most recent training data — it shipped Oct 2026

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
Mercury 3
Inception
Core performance indexes
LLM Stats Score
58.4
#2
36.1
#98
Reasoning
57.2
#3
34.8
#103
Coding
47.6
#2
21.5
#105
Agents
43.3
#3
19.4
#84
Cost, coverage & limits
Benchmark wins
—
—
Input price
$2.00 / M
$0.10 / M
Output price
$10.00 / M
$0.35 / M
Context window
1,000,000
1,000,000

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 12 for Mercury 3

No common benchmarks found

Claude Sonnet 5.5 and Mercury 3don'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 3 costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 20.0x more expensive than Mercury 3 ($0.10/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 28.6x more expensive than Mercury 3 ($0.35/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than Mercury 3.*

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

Lowest available price from all providers
Thu Oct 22 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
Inception
Mercury 3
Input tokens$0.10
Output tokens$0.35
Best providerInception
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Both models have the same input context window of 1,000,000 tokens. Mercury 3 can generate longer responses up to 131,072 tokens, while Claude Sonnet 5.5 is limited to 128,000 tokens.

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
Inception
Mercury 3
Input1,000,000 tokens
Output131,072 tokens
Thu Oct 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Sonnet 5.5 supports multimodal inputs, whereas Mercury 3 does not.

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

Claude Sonnet 5.5

Text
Images
Audio
Video

Mercury 3

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 Sonnet 5.5

Proprietary

Closed source

Mercury 3

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while Mercury 3 was released on 2026-10-19.

Mercury 3 is 1 month newer than Claude Sonnet 5.5.

Claude Sonnet 5.5

Sep 28, 2026

3 weeks ago

Mercury 3

Oct 19, 2026

3 days ago

3w newer

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Mercury 3's cutoff date is not specified.

We can confirm Claude Sonnet 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without Mercury 3's cutoff date.

Claude Sonnet 5.5

Jun 2026

Mercury 3

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. Mercury 3 is available from Inception.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

Mercury 3

inception logo
Inception
Input Price:Input: $0.10/1MOutput Price:Output: $0.35/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and Mercury 3 side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
Mercury 3
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs Mercury 3.

Which is better, Claude Sonnet 5.5 or Mercury 3?

Claude Sonnet 5.5 leads the LLM Stats Score 58.4 to 36.1. Claude Sonnet 5.5 is made by Anthropic and Mercury 3 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 Sonnet 5.5 compare to Mercury 3 in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. Mercury 3 scores GPQA: 89.2%, AA-LCR: 77.7%, IFBench: 76.8%, MRCR v2: 75.5%, DeepSearchQA: 71.3%.

Is Claude Sonnet 5.5 cheaper than Mercury 3?

Mercury 3 is 20.0x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. Mercury 3 costs $0.10/M input and $0.35/M output via inception.

What are the context window sizes for Claude Sonnet 5.5 and Mercury 3?

Claude Sonnet 5.5 supports 1.0M tokens and Mercury 3 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 Sonnet 5.5 and Mercury 3?

Key differences include LLM Stats Score (58.4 vs 36.1), input pricing ($2.00 vs $0.10/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and Mercury 3?

Claude Sonnet 5.5 is developed by Anthropic and Mercury 3 is developed by Inception.

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