Performance Benchmarks for GPT-5.3-Codex (Codex Harness)

Analyze how GPT-5.3-Codex (Codex Harness) stacks up against other frontier models in terms of cost-to-performance and raw intelligence (LMArena Elo).

2026 Performance Summary

🚀 Intelligence (Elo): 1371
💰 API Cost (Input): $0.00000175 / 1M tokens
⚡ API Cost (Output): $0.000014 / 1M tokens
⏱️ Real-world Throughput: 50 tokens/s

Analysis: While GPT-5.3-Codex (Codex Harness) is a capable model, it is currently outperformed in efficiency by Kimi K3.1 Pro (Max). Kimi K3.1 Pro (Max) sits higher on the Pareto line, offering approximately 324 points more intelligence (Elo) for a comparable or lower API cost.

Highly Recommended Alternatives

Frontier Model	LMArena Elo	API Cost (1M)	Throughput
Kimi K3.1 Pro (Max)	1695	$0.000002	25
GPT-6.1 Terra (Max)	1673	$0.000001	47
DeepSeek-V4.1-Flash-20261017 (Max)	1665	$3e-7	161
MiniMax-M3.1-Flash	1582	$1.5e-7	150
GLM-5.3 (Max)	1481	$8e-8	83

*These models represent the Pareto Frontier (optimal cost-to-performance).*