feat(install): add Antigravity skill installation support (#87)

docs/agents/USER_AGENTS_TEMPLATE.md

@@ -5,7 +5,7 @@
 > **Preferred (automated):** install the agent pack instead of (or in addition to) pasting this file:
 >
 > ```bash
-> rgctl -r "$REPO" install --skill --with-commands --tools cursor,claude,codex,agents
+> rgctl -r "$REPO" install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 > ```
 >
 > See [Agent commands](../guides/agent-commands.md). This template is a fallback / complementary channel — skills remain the canonical runtime guidance.
@@ -28,7 +28,7 @@ Default for agents: spawn **`rgctl -f json`** subprocesses (or use foreground **
 Install the agent pack once (limit `--tools` to the IDEs you use; default is all registry adapters):
 
 ```bash
-rgctl -r "$REPO" install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl -r "$REPO" install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 ```
 
 ---

docs/guides/agent-commands.md

@@ -31,7 +31,7 @@ You must pass at least one of **`--skill`** or **`--with-policy`**.
 | **`--skill`** | Meta skill **`rgctl`** (router + `references/`) and eight workflow skills: `rgctl-discover`, `rgctl-impact`, `rgctl-flow`, `rgctl-search`, `rgctl-gql`, `rgctl-migrate`, `rgctl-kantra`, `rgctl-gate`. |
 | **`--with-commands`** | Chat slash commands / prompts per adapter (e.g. Cursor `/rgctl-gql`, Claude `/rgctl:gql`). Use with **`--skill`** for the full experience. |
 | **`--with-policy`** | Structural bias snippet (e.g. `.cursor/rules/rgctl-structural.mdc`). Optional; does not replace skills. |
-| **`--tools id1,id2`** or **`--tools all`** | Which **registry adapters** receive files. **Default (omit flag):** `cursor`, `claude`, `codex`, `agents` (v1 quad). **`all`** = full registry (~40 products). Unknown ids: stderr warning; if none valid, exit **1**. |
+| **`--tools id1,id2`** or **`--tools all`** | Which **registry adapters** receive files. **Default (omit flag):** `cursor`, `claude`, `codex`, `agents`, `antigravity`. **`all`** = full registry (~40 products). Unknown ids: stderr warning; if none valid, exit **1**. |
 | **`-g` / `--global`** | Install under your **home** (e.g. `~/.cursor/skills/…`) instead of repo-local paths. Only agents with `supports_global: true` in the registry (see `--list-agents`). |
 | **`--list-agents`** | Print the registry table and exit (no install). |
 | **`--force`** | Overwrite rgctl-managed files that differ from the bundled version. |
@@ -43,11 +43,14 @@ You must pass at least one of **`--skill`** or **`--with-policy`**.
 cd /path/to/your-app
 
 # Skills + slash commands for common IDEs (repo-local)
-rgctl install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 
 # Cursor only
 rgctl install --skill --with-commands --tools cursor
 
+# Antigravity only
+rgctl install --skill --with-commands --tools antigravity
+
 # Full registry (many dot-directories)
 rgctl install --skill --with-commands --tools all
 

docs/guides/agent-skill.md

@@ -2,9 +2,9 @@
 
 ## Introduction
 
-The rgctl **agent skill** is a structured instruction set that teaches AI coding agents (Claude Code, Codex, Cursor) how to use the rgctl CLI to answer structural questions about a codebase. When installed into a repository, the skill gives your agent the ability to automatically map natural-language questions to the right rgctl commands, interpret the results, and report findings -- all without the developer needing to know the CLI syntax.
+The rgctl **agent skill** is a structured instruction set that teaches AI coding agents (Claude Code, Antigravity, Codex, Cursor) how to use the rgctl CLI to answer structural questions about a codebase. When installed into a repository, the skill gives your agent the ability to automatically map natural-language questions to the right rgctl commands, interpret the results, and report findings -- all without the developer needing to know the CLI syntax.
 
-The **agent pack** embeds skills and optional chat commands into the `rgctl` binary. `rgctl install` copies them into per-product paths (`.cursor/skills/rgctl/`, `.claude/skills/rgctl/`, `.agents/skills/rgctl/`, OpenCode, Pi, … — see [Agent commands](agent-commands.md)). You get a **meta skill** `rgctl`, eight **workflow skills** (`rgctl-discover`, `rgctl-gql`, …), and with `--with-commands` slash/prompt files that map to the same workflows. No external downloads. Once installed, the agent follows a structured loop: parse the question, route to the right workflow or CLI command, run `rgctl -f json`, summarize results.
+The **agent pack** embeds skills and optional chat commands into the `rgctl` binary. `rgctl install` copies them into per-product paths (`.cursor/skills/rgctl/`, `.claude/skills/rgctl/`, `.agents/skills/rgctl/`, `.agent/skills/rgctl/`, OpenCode, Pi, … — see [Agent commands](agent-commands.md)). You get a **meta skill** `rgctl`, eight **workflow skills** (`rgctl-discover`, `rgctl-gql`, …), and with `--with-commands` slash/prompt files that map to the same workflows. No external downloads. Once installed, the agent follows a structured loop: parse the question, route to the right workflow or CLI command, run `rgctl -f json`, summarize results.
 
 The skill turns rgctl from a CLI tool into an **always-available architectural advisor** inside your editor.
 
@@ -47,7 +47,7 @@ rgctl -r example/coolstore discover --with-cfg
 Install the rgctl agent skill into your repository:
 
 ```bash
-rgctl -r example/coolstore install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl -r example/coolstore install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 ```
 
 Text mode lists each created or updated path. Typical layout (Cursor example):
@@ -121,6 +121,7 @@ Limit adapters with **`--tools`** (comma-separated registry ids):
 ```bash
 rgctl -r example/coolstore install --skill --with-commands --tools claude
 rgctl -r example/coolstore install --skill --with-commands --tools codex,agents
+rgctl -r example/coolstore install --skill --with-commands --tools antigravity
 rgctl -r example/coolstore install --skill --with-commands --tools cursor
 rgctl install --list-agents   # all ids and paths
 ```
@@ -503,7 +504,7 @@ See **[Agent commands](agent-commands.md)** for the full table. Summary:
 | `--skill` | Meta `rgctl` + eight workflow skills (required for skills unless only `--with-policy`) |
 | `--with-commands` | Slash / prompt files per adapter |
 | `--with-policy` | Cursor structural rule snippet |
-| `--tools` | Registry ids or `all` (**default:** `cursor`, `claude`, `codex`, `agents`) |
+| `--tools` | Registry ids or `all` (**default:** `cursor`, `claude`, `codex`, `agents`, `antigravity`) |
 | `-g` / `--global` | User home instead of repo |
 | `--force` | Overwrite differing rgctl-managed files |
 | `--list-agents` | Print registry; no install |

docs/installation.md

@@ -224,7 +224,7 @@ rgctl migrate-cache --name coolstore --force   # explicit cache name
 After `rgctl` is on your PATH, install the **embedded agent pack** into the **target repository** (same root you use for `discover`):
 
 ```bash
-rgctl install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 rgctl -r /path/to/repo install --skill --with-commands --tools cursor
 rgctl install --list-agents
 ```
@@ -236,7 +236,7 @@ This copies from the binary (no network):
 - **Optional chat commands** — with `--with-commands` (e.g. `.cursor/commands/rgctl-gql.md`, Claude `/rgctl:gql` files)
 - **Optional policy** — `--with-policy` (Cursor structural rule snippet)
 
-Default **`--tools`** (omit flag) is **`cursor`, `claude`, `codex`, `agents`**. Use **`--tools all`** for the full registry (~40 paths). Unknown tool ids warn on stderr; **`--global`** requires `supports_global: true` per agent. **`--host`** is deprecated. Use **`-g`** for a global install under your home directory. If a managed file differs from the bundle, the command exits **1** unless you pass **`--force`**.
+Default **`--tools`** (omit flag) is **`cursor`, `claude`, `codex`, `agents`, `antigravity`**. Use **`--tools all`** for the full registry (~40 paths). Unknown tool ids warn on stderr; **`--global`** requires `supports_global: true` per agent. **`--host`** is deprecated. Use **`-g`** for a global install under your home directory. If a managed file differs from the bundle, the command exits **1** unless you pass **`--force`**.
 
 Install does **not** run `discover` — index the repo separately (`rgctl discover .`).
 

docs/json-api.md

@@ -1091,7 +1091,7 @@ rgctl -r "$REPO" -f json install --skill [--with-commands] [--with-policy] \
 rgctl -f json install --list-agents
 ```
 
-Omitting **`--tools`** installs the **v1 default** adapters: `cursor`, `claude`, `codex`, `agents`. Use **`--tools all`** for every registry entry. Unknown ids in `--tools` are reported on stderr; if none are valid, exit **1**. **`--global`** is rejected for agents with `supports_global: false` in the registry.
+Omitting **`--tools`** installs the default adapters: `cursor`, `claude`, `codex`, `agents`, `antigravity`. Use **`--tools all`** for every registry entry. Unknown ids in `--tools` are reported on stderr; if none are valid, exit **1**. **`--global`** is rejected for agents with `supports_global: false` in the registry.
 
 ### `install --list-agents`
 

docs/user-guide.md

@@ -100,7 +100,7 @@ rgctl -r /path/to/repo install --skill --with-commands
 rgctl install --list-agents
 ```
 
-That writes workflow skills (`rgctl-discover`, `rgctl-migrate`, `rgctl-kantra`, …), meta-skill `rgctl`, and optional slash commands. **Default (no `--tools`):** `cursor`, `claude`, `codex`, `agents`. Use **`--tools all`** for the full registry.
+That writes workflow skills (`rgctl-discover`, `rgctl-migrate`, `rgctl-kantra`, …), meta-skill `rgctl`, and optional slash commands. **Default (no `--tools`):** `cursor`, `claude`, `codex`, `agents`, `antigravity`. Use **`--tools all`** for the full registry.
 
 Full flag reference, adapter paths, and workflow ↔ CLI table: **[Agent commands](guides/agent-commands.md)**. Walkthrough: [Agent skill](guides/agent-skill.md). Add `--with-policy` for a Cursor structural-rules snippet. Use `-g` for a global install. Exit code **1** if a managed file differs unless you pass `--force`. Install does not run `discover`.
 
@@ -1240,7 +1240,7 @@ Migration hints (with `--export-migration-hints`) land under `.rgctl/migration_p
 | `metrics` | PageRank, betweenness, communities summary |
 | `export` | Serialize graph (json, graphml, dot, mermaid, obsidian vault, okf) |
 | `check` | CI policy gateway |
-| `install` | Copy the bundled agent skill into `.claude/skills/`, `.agents/skills/`, and `.cursor/skills/` |
+| `install` | Copy the bundled agent skill into `.claude/skills/`, `.agents/skills/`, `.agent/skills/`, and `.cursor/skills/` |
 | `semantic` | Opt-in semantic index + query (`--scope community`, `docs`, `all`) |
 | `serve` | HTTP dashboard + `/api/query` + `/api/status` (auto full pipeline); `--no-pipeline` fail-fast |
 

skills/rgctl/README.md

@@ -88,7 +88,7 @@ skills/rgctl/
 From a target repository (not the rgctl source tree unless you are dogfooding):
 
 ```bash
-rgctl install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 ```
 
 Installs meta skill `rgctl`, workflow skills (`rgctl-discover`, …), and optional slash commands per adapter. See [Agent commands guide](../../docs/guides/agent-commands.md).

skills/rgctl/SKILL.md

@@ -220,7 +220,7 @@ rgctl -r "$REPO" -f json <command> …
 ## Installation
 
 ```bash
-rgctl install --skill --with-commands --tools cursor,claude,codex,agents
+rgctl install --skill --with-commands --tools cursor,claude,codex,antigravity,agents
 ```
 
-Installs workflow skills (`rgctl-discover`, `rgctl-migrate`, `rgctl-kantra`, …), meta-skill `rgctl`, and slash commands for each selected adapter. Omitting `--tools` installs **cursor, claude, codex, agents**; use `--tools all` for the full registry. See [docs/guides/agent-commands.md](../../docs/guides/agent-commands.md). Workflow source: `skills/rgctl/workflows/`; keep `references/workflows.md` in sync via `cargo test -p rgctl-agent-pack-codegen workflows_reference_matches_fragments`.
+Installs workflow skills (`rgctl-discover`, `rgctl-migrate`, `rgctl-kantra`, …), meta-skill `rgctl`, and slash commands for each selected adapter. Omitting `--tools` installs **cursor, claude, codex, agents, antigravity**; use `--tools all` for the full registry. See [docs/guides/agent-commands.md](../../docs/guides/agent-commands.md). Workflow source: `skills/rgctl/workflows/`; keep `references/workflows.md` in sync via `cargo test -p rgctl-agent-pack-codegen workflows_reference_matches_fragments`.

src/cli/agent_pack.rs

@@ -253,7 +253,8 @@ pub fn bundle_bytes(bundle_rel: &Path) -> Option<&[u8]> {
 }
 
 /// Default install targets when `--tools` is omitted (phased v1 per #84).
-pub const DEFAULT_INSTALL_AGENTS: &[&str] = &["cursor", "claude", "codex", "agents"];
+pub const DEFAULT_INSTALL_AGENTS: &[&str] =
+    &["cursor", "claude", "codex", "agents", "antigravity"];
 
 pub fn all_agent_ids(manifest: &PackManifest) -> Vec<String> {
     manifest.agents.iter().map(|a| a.id.clone()).collect()
@@ -354,7 +355,10 @@ mod tests {
     fn default_install_agents_are_v1_quad() {
         let m = load_manifest().expect("manifest");
         let ids = default_agent_ids(&m);
-        assert_eq!(ids, ["cursor", "claude", "codex", "agents"]);
+        assert_eq!(
+            ids,
+            ["cursor", "claude", "codex", "agents", "antigravity"]
+        );
     }
 
     #[test]

tests/cli_output/install.rs

@@ -41,3 +41,57 @@ fn test_install_json_schema_sanity() {
     assert_eq!(write.get("agent").and_then(|v| v.as_str()), Some("cursor"));
     assert_eq!(write.get("workflow").and_then(|v| v.as_str()), Some("gql"));
 }
+
+#[test]
+fn test_install_json_schema_hosts_serialization() {
+    for (agent, expected) in [
+        ("claude", "claude"),
+        ("codex", "codex"),
+        ("agents", "codex"),
+        ("cursor", "cursor"),
+    ] {
+        let host = rgctl::cli::install_output::host_compat(agent);
+        let response = build_install_response(
+            "/tmp/repo",
+            "local",
+            vec![agent.to_string()],
+            false,
+            false,
+            false,
+            vec![InstallWrite {
+                agent: agent.into(),
+                workflow: None,
+                kind: InstallWriteKind::Skill,
+                path: format!("/tmp/repo/skills/{expected}/SKILL.md"),
+                status: InstallWriteStatus::Created,
+                host,
+            }],
+        );
+        let doc = serde_json::to_value(&response).expect("serialize install fixture");
+        let writes = doc["writes"].as_array().expect("writes array");
+        assert_eq!(writes[0]["host"].as_str(), Some(expected));
+    }
+
+    // Antigravity does not expand the legacy host schema; it serializes with agent only.
+    assert_eq!(rgctl::cli::install_output::host_compat("antigravity"), None);
+    let response = build_install_response(
+        "/tmp/repo",
+        "local",
+        vec!["antigravity".to_string()],
+        false,
+        false,
+        false,
+        vec![InstallWrite {
+            agent: "antigravity".into(),
+            workflow: None,
+            kind: InstallWriteKind::Skill,
+            path: "/tmp/repo/.agent/skills/rgctl/SKILL.md".into(),
+            status: InstallWriteStatus::Created,
+            host: rgctl::cli::install_output::host_compat("antigravity"),
+        }],
+    );
+    let doc = serde_json::to_value(&response).expect("serialize install fixture");
+    let writes = doc["writes"].as_array().expect("writes array");
+    assert_eq!(writes[0]["agent"].as_str(), Some("antigravity"));
+    assert!(writes[0].get("host").is_none());
+}

tests/install_skill.rs

@@ -240,7 +240,7 @@ fn install_opencode_and_pi_paths() {
 }
 
 #[test]
-fn install_default_tools_is_v1_quad_not_opencode() {
+fn install_default_tools_includes_antigravity() {
     let dir = tempfile::tempdir().expect("tempdir");
     let repo = fs::canonicalize(dir.path()).expect("canonicalize");
     let output = run_in(
@@ -255,9 +255,36 @@ fn install_default_tools_is_v1_quad_not_opencode() {
     assert!(repo.join(".cursor/skills/rgctl/SKILL.md").is_file());
     assert!(repo.join(".claude/skills/rgctl/SKILL.md").is_file());
     assert!(repo.join(".agents/skills/rgctl/SKILL.md").is_file());
+    assert!(repo.join(".agent/skills/rgctl/SKILL.md").is_file());
     assert!(!repo.join(".opencode/skills/rgctl/SKILL.md").exists());
 }
 
+#[test]
+fn install_tools_antigravity_writes_agent_directory_only() {
+    let dir = tempfile::tempdir().expect("tempdir");
+    let repo = fs::canonicalize(dir.path()).expect("canonicalize");
+    let output = run_in(
+        dir.path(),
+        &[
+            "-r",
+            &repo.display().to_string(),
+            "install",
+            "--skill",
+            "--tools",
+            "antigravity",
+        ],
+    );
+    assert!(
+        output.status.success(),
+        "stderr={}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert!(repo.join(".agent/skills/rgctl/SKILL.md").is_file());
+    assert!(!repo.join(".claude/skills/rgctl/SKILL.md").exists());
+    assert!(!repo.join(".cursor/skills/rgctl/SKILL.md").exists());
+    assert!(!repo.join(".agents/skills/rgctl/SKILL.md").exists());
+}
+
 #[test]
 fn install_unknown_tools_exits_one() {
     let dir = tempfile::tempdir().expect("tempdir");

website/src/app/install/page.tsx

@@ -41,7 +41,7 @@ export default function InstallPage() {
         <TerminalBlock
           lines={[
             "rgctl --version",
-            "rgctl install --skill --with-commands --tools cursor,claude,codex,agents",
+            "rgctl install --skill --with-commands --tools cursor,claude,codex,antigravity,agents",
           ]}
         />
         <p className="text-sm text-[var(--mute)]">