Claude Sonnet 5.5 vs Mercury 2
Claude Sonnet 5.5 leads the LLM Stats Score 58.3 to 23.5. Mercury 2 is 10.7x cheaper per token.
Anthropic · Inception · Updated for 2026
Which is better?
Claude Sonnet 5.5 leads the overall LLM Stats Score 58.3 to 23.5, ranking #2 overall.
On price, Mercury 2 is roughly 10.7x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Claude Sonnet 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 Sonnet 5.5
- overall performance matters — it scores 58.3 and ranks #2 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 10.7x cheaper per token
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
47 reported for Claude Sonnet 5.5 · 6 for Mercury 2
Claude Sonnet 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
For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 8.0x more expensive than Mercury 2 ($0.25/1M tokens).
For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 13.3x more expensive than Mercury 2 ($0.75/1M tokens).
In conclusion, Claude Sonnet 5.5 is more expensive than Mercury 2.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to Mercury 2's 128,000 tokens. Claude Sonnet 5.5 can generate longer responses up to 128,000 tokens, while Mercury 2 is limited to 8,192 tokens.
Input capabilities
Documented input modalities across available providers
Claude Sonnet 5.5 supports multimodal inputs, whereas Mercury 2 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
Mercury 2
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Sonnet 5.5 was released on 2026-09-28, while Mercury 2 was released on 2026-02-24.
Claude Sonnet 5.5 is 7 months newer than Mercury 2.
Sep 28, 2026
1 weeks ago
7mo newerFeb 24, 2026
7 months ago
Knowledge Cutoff
When training data ends
Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Mercury 2'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 2's cutoff date.
Jun 2026
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Provider Availability
Claude Sonnet 5.5 is available from Anthropic. Mercury 2 is available from Inception.
Claude Sonnet 5.5
Mercury 2
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Sonnet 5.5 and Mercury 2 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Sonnet 5.5 vs Mercury 2.