The closest alternative to Grok 4.20 Multi-Agent is Grok 4.5 — comparable intelligence (53.8 vs —); for a cheaper option, GPT-5.6 Terra runs $1.00/M vs $1.25/M; and the best open-weight substitute is Kimi K3.
Grok 4.5 is the closest alternative to Grok 4.20 Multi-Agent, with an Intelligence Index of 53.8 (Grok 4.20 Multi-Agent scores —) at $2.00 per million input tokens.
Yes — GPT-5.6 Terra costs $1.00 per million input tokens versus $1.25 for Grok 4.20 Multi-Agent, while staying within ~8 points of its Intelligence Index.
Kimi K3 is the strongest open-weight alternative to Grok 4.20 Multi-Agent — downloadable from Hugging Face and self-hostable, scoring 57.1 on intelligence.