Model Comparison
GPT-5.6 Luna vs Mercury 2Which is better in 2026?
GPT-5.6 Luna significantly outperforms across most benchmarks. Mercury 2 is 6.0x cheaper per token.
Verdict: GPT-5.6 Luna vs Mercury 2 — which is better?
GPT-5.6 Luna (by OpenAI) and Mercury 2 (by Inception) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
GPT-5.6 Luna outperforms in 1 benchmarks (GPQA), while Mercury 2 is better at 0 benchmarks. GPT-5.6 Luna significantly outperforms across most benchmarks.
On price, Mercury 2 is roughly 6.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose GPT-5.6 Luna if…
- you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Jul 2026
Choose Mercury 2 if…
- cost matters — it's about 6.0x cheaper per token
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.6 Luna outperforms in 1 benchmarks (GPQA), while Mercury 2 is better at 0 benchmarks.
GPT-5.6 Luna significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 4.0x more expensive than Mercury 2 ($0.25/1M tokens).
For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 8.0x more expensive than Mercury 2 ($0.75/1M tokens).
In conclusion, GPT-5.6 Luna is more expensive than Mercury 2.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.6 Luna accepts 1,050,000 input tokens compared to Mercury 2's 128,000 tokens. GPT-5.6 Luna can generate longer responses up to 128,000 tokens, while Mercury 2 is limited to 8,192 tokens.
Input Capabilities
Supported data types and modalities
GPT-5.6 Luna supports multimodal inputs, whereas Mercury 2 does not.
GPT-5.6 Luna can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.6 Luna
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
GPT-5.6 Luna was released on 2026-07-09, while Mercury 2 was released on 2026-02-24.
GPT-5.6 Luna is 5 months newer than Mercury 2.
Jul 9, 2026
2 weeks ago
4mo newerFeb 24, 2026
5 months ago
Knowledge Cutoff
When training data ends
GPT-5.6 Luna has a documented knowledge cutoff of 2026-02-16, while Mercury 2's cutoff date is not specified.
We can confirm GPT-5.6 Luna's training data extends to 2026-02-16, but cannot make a direct comparison without Mercury 2's cutoff date.
Feb 2026
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Provider Availability
GPT-5.6 Luna is available from OpenAI. Mercury 2 is available from Inception.
GPT-5.6 Luna
Mercury 2
Outputs Comparison
Key Takeaways
GPT-5.6 Luna
View detailsOpenAI
Mercury 2
View detailsInception
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-5.6 Luna and Mercury 2 side-by-side, then vote on the output you prefer.
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FAQ
Common questions about GPT-5.6 Luna vs Mercury 2.