Gemini CLI shutdown forces 100k-star project developers to manually rewrite incompatible Antigravity config layouts with 28-day notice

Google killed Gemini CLI on June 18 2026, replacing it with a closed-source Antigravity CLI that breaks on four key behaviors: default model, streaming format, state directory, and exit codes. Developers who contributed 6000+ pull requests to the Apache 2.0 Gemini repo are now stuck manually rewriting GEMINI.md project files, MCP server definitions, slash-command extensions, and hook configurations into Antigravity's incompatible layout. No automated migration tool exists. Google's own postmortem acknowledges Antigravity will not have 1:1 feature parity. The community is also angry about the bait-and-switch from open-source to closed-source proprietary product. The gap: a CLI tool that reads a Gemini CLI project tree (GEMINI.md, .gemini/ MCP configs, hooks, slash commands) and outputs a validated Antigravity CLI config directory, with a diff report of what changed and what has no equivalent.