GPT-5.1 Codex vs Mercury 2
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI and Mercury 2 by Inception are evenly matched across 6 benchmarks. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
Coding: In coding, GPT-5.1 Codex scores 1197 on Design Arena ELO compared to Mercury 2's 1014, while GPT-5.1 Codex scores 1174 on Website Arena ELO compared to Mercury 2's 1036.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to Mercury 2's 128K.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while Mercury 2 costs $0.25/1M input and $0.75/1M output. Mercury 2 is the more affordable option for API usage.
Verdict
Mercury 2 leads across the board in affordability, making it the stronger overall choice in this comparison.
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GPT-5.1 Codex vs Mercury 2 — FAQ
Which is better, GPT-5.1 Codex or Mercury 2?
GPT-5.1 Codex and Mercury 2 are evenly matched across benchmarks. The best choice depends on your specific priorities such as coding ability, speed, or pricing.
How does GPT-5.1 Codex compare to Mercury 2 for coding?
SWE-bench Verified data is not available for both models. Check the detailed comparison charts above for other coding-related metrics.
Is GPT-5.1 Codex cheaper than Mercury 2?
Yes, Mercury 2 is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. Mercury 2 costs $0.25/1M input and $0.75/1M output tokens.
Which is faster, GPT-5.1 Codex or Mercury 2?
Output speed data is not available for both models. Check the speed section of the comparison above for available performance data.
What benchmarks does the GPT-5.1 Codex vs Mercury 2 comparison cover?
This comparison covers 6 benchmarks including Input Cost, Output Cost, Context Length, Cached Input Cost, Design Arena ELO, Website Arena ELO. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.