The closest alternative to Claude Sonnet 5 is Claude Fable 5 — comparable intelligence (— vs —); for a cheaper option, Nano Banana 2 Lite (Gemini 3.1 Flash Lite Image) runs $0.250/M vs $2.00/M; for more speed, Morph V3 Large hits 1.8k t/s; and the best open-weight substitute is North Mini Code (free).
Claude Fable 5 is the closest alternative to Claude Sonnet 5, with an Intelligence Index of — (Claude Sonnet 5 scores —) at $10.00 per million input tokens.
Yes — Nano Banana 2 Lite (Gemini 3.1 Flash Lite Image) costs $0.250 per million input tokens versus $2.00 for Claude Sonnet 5, while staying within ~8 points of its Intelligence Index.
North Mini Code (free) is the strongest open-weight alternative to Claude Sonnet 5 — downloadable from Hugging Face and self-hostable, scoring — on intelligence.