Host support: Antigravity — native plugin projection, Gemini migration boundaries, and explicit CLI/IDE contracts

[ScriptedAlchemy]

Scope / research evidence

P2 feature expansion. Research date 2026-09-06; Agent Bundle baseline 5fc8de37c9695b816d55bdcf18a6bcb1dfee69f5. Read Google's official Antigravity documentation; no CLI/IDE installation, migration, account change or native invocation was performed.

This covers the Antigravity product family, with separate CLI, desktop and IDE compatibility profiles. The research site currently labels CLI v1.1.25, desktop v2.12.2 and IDE v2.5.5; these are documentation labels, not versions independently tested here. Gemini CLI is #695. An explicit migration tool does not establish byte-for-byte compatibility of every Gemini extension.

Official specifications and configuration references

• CLI plugin manifest, package layout, skills and management
• Desktop/IDE plugin directories and component discovery
• Published schema URL named by the CLI guide
• Gemini-to-Antigravity configuration and extension migration
• MCP configuration, transport fields and profile locations
• Hook configuration and exact per-event JSON contract
• Official product/documentation entry

The schema URL is documented by the host, but direct retrieval was unavailable through the research browser. Pin the actual schema/parser before emitting a compatibility guarantee. The documentation has profile differences and an example/schema inconsistency described below; do not silently resolve them by guessing.

Native artifact and schema questions

The native layout uses root plugin.json, mcp_config.json, hooks.json, plus skills/rules and optional agents. CLI installs under ~/.gemini/antigravity-cli/plugins/; desktop docs describe workspace .agents/plugins/ or _agents/plugins/ and global ~/.gemini/config/plugins/.

composite-root/
  plugin.json
  mcp_config.json
  hooks.json
  skills/review/SKILL.md       # documented desktop package shape
  rules/review.md
  hooks/before.antigravity.mjs
  mcp/example.mjs

Illustrative native marker:

{"name":"example-plugin","description":"Project review capabilities"}

The CLI guide requires a name and shows a closed schema, while the general plugin guide makes name optional. CLI workspace skills are described as flat Markdown files, while the package guide uses skills/<name>/SKILL.md. Also, the CLI's manifest example includes $schema while its displayed closed-schema properties only list name/description. These are concrete parser/version verification requirements, not permission to emit both formats indiscriminately.

A native root plugin.json can conflict with Agent Bundle's closed portable manifest. First test whether a single record can satisfy both actual parsers. If not, reject the incompatible composite selection or provide an explicitly separate native install projection; do not overwrite portable metadata or claim successful file merging proves support.

Native operator lifecycle and migration

Documented commands:

agy plugin install /absolute/composite-root
agy plugin list
agy plugin disable example-plugin
agy plugin enable example-plugin
agy plugin uninstall example-plugin

The host also provides agy plugin import gemini for converting legacy extensions. It converts command and MCP representations and changes storage paths. That is an explicit user migration operation, not a prerequisite Agent Bundle should run against all of the user's extensions or credentials. Prefer generating native output directly from canonical content/operations; do not build a Gemini artifact and migrate it every build.

Preserve native disabled state, installed identity and consent. Shared .agents discovery needs negative conformance tests alongside other hosts. Local code paths and project/global settings must remain distinct, and removal must not purge shared profile data or other plugins.

MCP lowering

Native MCP uses mcpServers in mcp_config.json. The current guide requires serverUrl for remote definitions rather than Gemini's older url/httpUrl. Independent project config is .agents/mcp_config.json; global configuration is ~/.gemini/config/mcp_config.json. Bundled registration must not be duplicated there automatically.

{"mcpServers":{"example":{"command":"node","args":["/absolute/installed-plugin/mcp/example.mjs"]}}}

The path is illustrative. Prove the native package-root anchor and cwd resolution before generating relocatable config. Keep API keys/OAuth in native operator mechanisms, preserve disabledTools/disabled state, and test remote transport rather than treating any successful URL connection as the intended protocol.

Hook mapping

Native hooks.json groups named hook definitions around event configurations. Inputs are camelCase JSON with conversation/workspace/tool-call context; command stdout is structured output, not diagnostics. PreToolUse has several authorization decisions—not only a boolean—including ask versus force_ask. A canonical continue must not accidentally become unconditional allow. PostToolUse is observational under the documented output contract; do not inject unsupported context there merely because another host accepts it.

Map only pinned event semantics and preserve matcher/filter behavior, multi-workspace identity, timeout/failure handling and cancellation. Permissions and sandboxing remain host-owned. SDK lifecycle callbacks are not automatically the CLI shell-hook contract, and implementing this adapter does not require embedding Google's Python agent SDK.

Acceptance

• Pin native version/parser/schema and settle required-name, $schema, skill-layout and profile-path differences with real fixtures.
• Validate root manifest compatibility with portable/Claude/Codex selections; incompatibility is explicit and never overwrites another host's metadata.
• Skills/rules-only output starts no MCP, Flight, SQLite or plugin execution process.
• Native install/list/disable/enable/remove discovers exactly the declared components and preserves user consent/configuration.
• A generated MCP operation completes from a relocated, source-free artifact with native argv/cwd/environment and transport semantics.
• Before-tool deny/ask/continue and observational hooks preserve authority; sentinel tests prevent accidental unconditional approval.
• Test required versus forbidden .agents and profile discovery, reversed target order, no duplicate registration, and shared state retention.
• If migration compatibility is claimed, test a pinned Gemini fixture separately; never migrate unrelated user assets or secrets.
• Record real native execution separately from schema validation, UI listing or a successful migration command.
• Update English/Chinese documentation with supported profiles and exact native references.

Reuse current adapters, compiler/manifest/launch/receipt machinery and #651/#652 tests. No new agent orchestration, automatic account migration, SDK embedding, broad permission override, or global removal of AB4106.

[ScriptedAlchemy]

Resolved by #721 (72a8857ebe).

Antigravity — observed docs retrieved 2026-09-06; no product or CLI version is published on any page. Not supported as published: this client loads nothing from the emitted package.

Surface	State	Evidence
manifest	unavailable	2026-09-06: unproven. https://www.antigravity.google/docs/cli/plugins requires a root plugin.json and embeds a closed schema for it ("additionalProperties": false, "required": ["name"], properties name and description only) that omits every other Agent Plugins manifest field this artifact emits — including the $schema its own example shows — and the schema URL that example cites returns 404. No page states what install-time validation does with an unknown root key, and no CLI run against the emitted manifest is recorded here.
skills	unavailable	2026-09-06: unproven. The root plugin.json is "a mandatory manifest located at the root of your plugin directory" (https://www.antigravity.google/docs/cli/plugins), so component discovery depends on the unproven manifest outcome above; Antigravity does document skills//SKILL.md in its own plugin layout, and nothing here establishes whether the emitted tree is reached.
mcp	unavailable	2026-09-06: the plugin MCP file is mcp_config.json, not mcp.json, and remote servers key on serverUrl rather than url (https://www.antigravity.google/docs/cli/plugins, https://www.antigravity.google/docs/cli/gcli-migration: "Legacy schema keys: url or httpUrl -> Modern schema key: serverUrl").
placeholders	unavailable	2026-09-06: no ${PLUGIN_ROOT}, ${PLUGIN_DATA}, or other path placeholder is documented for Antigravity MCP or hook configuration.
hooks	unavailable	2026-09-06: Antigravity reads a root hooks.json as a named-hook map (https://www.antigravity.google/docs/hooks/); Agent Plugins 1.0.0 defines no hooks, so this projection emits no hooks document for it to read.

Paths it reads: none.
No install command is recorded, because nothing this bundle emits installs there.

Every row above is pinned to that client's own documentation on the date shown, is validated on every build, and renders in INSTALL.md and the generated hosts reference. A surface recorded unavailable or degraded names exactly what the client would need; no unsupported feature is projected silently.