Quick Take

GLM-5.2 (Z AI) and GPT-5.3 Codex (xhigh) (OpenAI) represent different approaches to model deployment. Released on June 16, 2026, GLM-5.2 focuses on rapid, efficient output. GPT-5.3 Codex (xhigh), released February 5, 2026, prioritizes raw intelligence and depth, reflected in its higher index scores and broader benchmark coverage.

Benchmark Read

GPT-5.3 Codex (xhigh) leads in intelligence with an index of 44.3 compared to GLM-5.2’s 34.1. In direct benchmark comparisons, GPT-5.3 Codex (xhigh) consistently outperforms GLM-5.2:

• GPQA: 0.915 (GPT-5.3) vs 0.686 (GLM-5.2)
• HLE: 0.399 (GPT-5.3) vs 0.084 (GLM-5.2)
• SciCode: 0.532 (GPT-5.3) vs 0.361 (GLM-5.2)
• LCR: 0.74 (GPT-5.3) vs 0.373 (GLM-5.2)

GPT-5.3 Codex (xhigh) also excels in specialized metrics, including IFBench (0.754), TerminalBench Hard (0.530), and TAU2 (0.860). GLM-5.2 shows strength in coding with a 46.5 index, though its math capabilities remain unknown.

Cost and Speed

GLM-5.2 is the more economical choice for high-volume tasks, with a blended cost of $3.16/1M tokens compared to $4.81/1M for GPT-5.3 Codex (xhigh). GLM-5.2 also offers a significantly faster user experience, with an output speed of 118.912 tok/s and a time to first token of 1.094s. Conversely, GPT-5.3 Codex (xhigh) operates at 83.267 tok/s and experiences a substantial delay in time to first token at 73.559s.

Best Fit

GLM-5.2 is best suited for applications requiring rapid, high-frequency responses where cost efficiency is paramount. GPT-5.3 Codex (xhigh) is the optimal fit for complex research, advanced coding, and reasoning-heavy tasks where accuracy and intelligence outweigh the need for immediate response times.