Gemini CLI Nightly Build Shows Warning: Not Yet Optimized for Gemini 4

A banner saying [Gemini CLI](/tools/gemini-cli) is not yet optimized for Gemini 4 appeared in the v0.66.0 nightly build from Oct 17, 2026. The build also includes four CLI fixes, one of which stops it from falsely reporting a successful update when a different binary is on the PATH.