The closest alternative to GPT-5 Mini is Mistral Medium 3.5 — comparable intelligence (39.2 vs 38.9); for a cheaper option, MiMo-V2.5 runs $0.140/M vs $0.250/M; for more speed, gpt-oss-120b (free) hits 554 t/s; and the best open-weight substitute is MiniMax M3.
Mistral Medium 3.5 is the closest alternative to GPT-5 Mini, with an Intelligence Index of 39.2 (GPT-5 Mini scores 38.9) at $1.50 per million input tokens.
Yes — MiMo-V2.5 costs $0.140 per million input tokens versus $0.250 for GPT-5 Mini, while staying within ~8 points of its Intelligence Index.
MiniMax M3 is the strongest open-weight alternative to GPT-5 Mini — downloadable from Hugging Face and self-hostable, scoring 54.7 on intelligence.