Native plugin installation

Summary of the spec that moved agb from a global npm install to a native Antigravity plugin.

Historical, superseded

This is a summary of a completed design spec, kept for design history. It does not describe current behavior; see Installation and Plugin and migration. The full spec: .adlc/specs/native-plugin-installation.md.

The spec (T-PLUGIN-00..04, October 2026) planned the move from npm install -g antigravity-booster plus agb bootstrap to a native Google Antigravity plugin installed with agy plugin install.

Its main decisions:

Two layers. The Node.js orchestration engine ships as single-file esbuild bundles (dist/agb.mjs, dist/mcp-server.mjs). The ADLC gate toolkit ships as an integrity-pinned vendored package under vendor/adlc/. Both are committed to git so a git-URL install runs without npm install, and CI fails if they drift from a fresh build.
Measured platform facts (agy 1.2.16, macOS and Linux): plugins stage byte-for-byte into ~/.gemini/config/plugins/<name>/, and agy plugin validate recognises skills, agents, commands, MCP servers and hooks.
POSIX launchers. bin/node-launcher.sh finds a suitable Node, and bin/hook-runner.sh keeps a broken hook from crashing the session.
Fail-closed enforcement. Enforcement gates (rails-guard and the in-session policy guard) fail closed. Audit gates (gate-manifest, flail-detector) degrade.
Bundled builds ignore overrides. Development env overrides are ignored when __AGB_BUNDLED__ is true. The companion adlc-antigravity plugin resolves only from its staged directory.
Doctrine as a pinned dependency. The doctrine comes from @adlc/antigravity, committed as the unmodified registry tarball in vendor/cache/ and checked byte-for-byte in CI. A contract handshake (adlcContract) checks compatibility.
Migration. agb migrate moves an npm install to the plugin, with a state machine and rollback.

Appendix A of the spec records the binding owner decisions and errata. Where the body and the appendix disagree, the appendix wins.