The closest alternative to GPT-5 Codex is GLM 5.1 — comparable intelligence (43.8 vs 44.6); for a cheaper option, MiniMax M3 runs $0.300/M vs $1.25/M; for more speed, GLM 4.7 hits 555 t/s; and the best open-weight substitute is MiniMax M3.
GLM 5.1 is the closest alternative to GPT-5 Codex, with an Intelligence Index of 43.8 (GPT-5 Codex scores 44.6) at $0.980 per million input tokens.
Yes — MiniMax M3 costs $0.300 per million input tokens versus $1.25 for GPT-5 Codex, while staying within ~8 points of its Intelligence Index.
MiniMax M3 is the strongest open-weight alternative to GPT-5 Codex — downloadable from Hugging Face and self-hostable, scoring 54.7 on intelligence.