feat(installer): add Antigravity IDE support as a native plugin

README.md

@@ -2,7 +2,7 @@
 
 # CodeGraph
 
-### Supercharge Claude Code, Cursor, Codex, OpenCode, and Hermes Agent with Semantic Code Intelligence
+### Supercharge Claude Code, Cursor, Codex, OpenCode, Hermes Agent, and Antigravity IDE with Semantic Code Intelligence
 
 **~35% cheaper · ~70% fewer tool calls · 100% local**
 
@@ -19,6 +19,7 @@
 [![Codex CLI](https://img.shields.io/badge/Codex_CLI-supported-blueviolet.svg)](#supported-agents)
 [![opencode](https://img.shields.io/badge/opencode-supported-blueviolet.svg)](#supported-agents)
 [![Hermes Agent](https://img.shields.io/badge/Hermes_Agent-supported-blueviolet.svg)](#supported-agents)
+[![Antigravity IDE](https://img.shields.io/badge/Antigravity_IDE-supported-blueviolet.svg)](#supported-agents)
 
 </div>
 
@@ -41,7 +42,7 @@ npx @colbymchenry/codegraph        # zero-install, or:
 npm i -g @colbymchenry/codegraph
 ```
 
-<sub>CodeGraph bundles its own runtime — nothing to compile, no native build, works the same everywhere. The interactive installer auto-configures your agent(s) — Claude Code, Cursor, Codex CLI, opencode, Hermes Agent.</sub>
+<sub>CodeGraph bundles its own runtime — nothing to compile, no native build, works the same everywhere. The interactive installer auto-configures your agent(s) — Claude Code, Cursor, Codex CLI, opencode, Hermes Agent, Antigravity IDE.</sub>
 
 ### Initialize Projects
 
@@ -171,7 +172,7 @@ npx @colbymchenry/codegraph
 ```
 
 The installer will:
-- Ask which agent(s) to configure — auto-detects installed ones from: **Claude Code**, **Cursor**, **Codex CLI**, **opencode**, **Hermes Agent**
+- Ask which agent(s) to configure — auto-detects installed ones from: **Claude Code**, **Cursor**, **Codex CLI**, **opencode**, **Hermes Agent**, **Antigravity IDE**
 - Prompt to install `codegraph` on your PATH (so agents can launch the MCP server)
 - Ask whether configs apply to all your projects or just this one
 - Write each chosen agent's MCP server config + an instructions file (e.g. `CLAUDE.md`, `.cursor/rules/codegraph.mdc`, `~/.codex/AGENTS.md`)
@@ -197,7 +198,7 @@ codegraph install --print-config codex               # print snippet, no file wr
 
 ### 2. Restart Your Agent
 
-Restart your agent (Claude Code / Cursor / Codex CLI / opencode / Hermes Agent) for the MCP server to load.
+Restart your agent (Claude Code / Cursor / Codex CLI / opencode / Hermes Agent / Antigravity IDE) for the MCP server to load.
 
 ### 3. Initialize Projects
 
@@ -474,6 +475,7 @@ the MCP server and writing its instructions file:
 - **Codex CLI**
 - **opencode**
 - **Hermes Agent**
+- **Antigravity IDE**
 
 ## Supported Languages
 
@@ -534,7 +536,7 @@ MIT
 
 <div align="center">
 
-**Made for AI coding agents — Claude Code, Cursor, Codex CLI, opencode, and Hermes Agent**
+**Made for AI coding agents — Claude Code, Cursor, Codex CLI, opencode, Hermes Agent, and Antigravity IDE**
 
 [Report Bug](https://github.com/colbymchenry/codegraph/issues) · [Request Feature](https://github.com/colbymchenry/codegraph/issues)
 

src/installer/targets/antigravity.ts

@@ -0,0 +1,256 @@
+/**
+ * Antigravity IDE target.
+ *
+ * Installs CodeGraph as an Antigravity Plugin, enabling support for
+ * both global (`~/.gemini/config/plugins/codegraph/`) and local 
+ * (`./.agents/plugins/codegraph/`) deployments.
+ *
+ * The plugin bundles:
+ *   - `plugin.json`
+ *   - `mcp_config.json`
+ *   - `skills/codegraph-instructions/SKILL.md` (Agent instructions)
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import {
+  AgentTarget,
+  DetectionResult,
+  InstallOptions,
+  Location,
+  WriteResult,
+} from './types';
+import {
+  getMcpServerConfig,
+  jsonDeepEqual,
+  readJsonFile,
+  writeJsonFile,
+} from './shared';
+import {
+  INSTRUCTIONS_TEMPLATE,
+} from '../instructions-template';
+
+function configDir(loc: Location): string {
+  return loc === 'global'
+    ? path.join(os.homedir(), '.gemini', 'config', 'plugins', 'codegraph')
+    : path.join(process.cwd(), '.agents', 'plugins', 'codegraph');
+}
+
+function pluginJsonPath(loc: Location): string {
+  return path.join(configDir(loc), 'plugin.json');
+}
+
+function mcpJsonPath(loc: Location): string {
+  return path.join(configDir(loc), 'mcp_config.json');
+}
+
+function instructionsPath(loc: Location): string {
+  return path.join(configDir(loc), 'skills', 'codegraph-instructions', 'SKILL.md');
+}
+
+function rulesPath(loc: Location): string {
+  return path.join(configDir(loc), 'rules', 'codegraph-rules.md');
+}
+
+class AntigravityTarget implements AgentTarget {
+  readonly id = 'antigravity' as const;
+  readonly displayName = 'Antigravity IDE';
+  readonly docsUrl = '';
+
+  supportsLocation(_loc: Location): boolean {
+    return true;
+  }
+
+  detect(loc: Location): DetectionResult {
+    const dir = configDir(loc);
+    const installed = fs.existsSync(dir);
+    return { installed, alreadyConfigured: installed, configPath: dir };
+  }
+
+  install(loc: Location, _opts: InstallOptions): WriteResult {
+    const files: WriteResult['files'] = [];
+
+    // Cleanup legacy files from earlier flawed global install
+    if (loc === 'global') {
+      const legacyCleanup = cleanupLegacyFiles();
+      files.push(...legacyCleanup);
+    }
+
+    files.push(writePluginJson(loc));
+    files.push(writeMcpEntry(loc));
+    files.push(writeInstructionsEntry(loc));
+    files.push(writeRulesEntry(loc));
+
+    return { files };
+  }
+
+  uninstall(loc: Location): WriteResult {
+    const files: WriteResult['files'] = [];
+
+    const dir = configDir(loc);
+    if (fs.existsSync(dir)) {
+      try {
+        fs.rmSync(dir, { recursive: true, force: true });
+        files.push({ path: dir, action: 'removed' });
+      } catch {
+        // Ignore removal errors
+      }
+    } else {
+      files.push({ path: dir, action: 'not-found' });
+    }
+
+    if (loc === 'global') {
+      const legacyCleanup = cleanupLegacyFiles();
+      files.push(...legacyCleanup);
+    }
+
+    return { files };
+  }
+
+  printConfig(loc: Location): string {
+    const target = mcpJsonPath(loc);
+    const snippet = JSON.stringify({ mcpServers: { codegraph: getMcpServerConfig() } }, null, 2);
+    return `# Add to ${target}\n\n${snippet}\n`;
+  }
+
+  describePaths(loc: Location): string[] {
+    return [configDir(loc)];
+  }
+}
+
+function writePluginJson(loc: Location): WriteResult['files'][number] {
+  const file = pluginJsonPath(loc);
+  const dir = path.dirname(file);
+  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
+
+  const existing = fs.existsSync(file) ? readJsonFile(file) : null;
+  const after = { name: 'codegraph', description: 'CodeGraph Semantic Code Intelligence' };
+
+  if (existing && jsonDeepEqual(existing, after)) {
+    return { path: file, action: 'unchanged' };
+  }
+
+  writeJsonFile(file, after);
+  return { path: file, action: existing ? 'updated' : 'created' };
+}
+
+function writeMcpEntry(loc: Location): WriteResult['files'][number] {
+  const file = mcpJsonPath(loc);
+  const dir = path.dirname(file);
+  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
+
+  const existing = fs.existsSync(file) ? readJsonFile(file) : null;
+  const after = { mcpServers: { codegraph: getMcpServerConfig() } };
+
+  if (existing && jsonDeepEqual(existing, after)) {
+    return { path: file, action: 'unchanged' };
+  }
+
+  writeJsonFile(file, after);
+  return { path: file, action: existing ? 'updated' : 'created' };
+}
+
+function writeInstructionsEntry(loc: Location): WriteResult['files'][number] {
+  const file = instructionsPath(loc);
+  const dir = path.dirname(file);
+  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
+
+  const SKILL_CONTENT = `---
+name: codegraph-instructions
+description: Explains how to use the CodeGraph MCP server for semantic code intelligence, codebase graph queries, finding references, and understanding architecture. Use this whenever the codegraph_* tools are available or the user asks questions about code structure.
+---
+
+${INSTRUCTIONS_TEMPLATE}
+`;
+
+  let action: 'created' | 'updated' | 'unchanged' = 'created';
+  if (fs.existsSync(file)) {
+    const existing = fs.readFileSync(file, 'utf-8');
+    if (existing === SKILL_CONTENT) {
+      action = 'unchanged';
+    } else {
+      action = 'updated';
+    }
+  }
+
+  if (action !== 'unchanged') {
+    fs.writeFileSync(file, SKILL_CONTENT, 'utf-8');
+  }
+
+  return { path: file, action };
+}
+
+function writeRulesEntry(loc: Location): WriteResult['files'][number] {
+  const file = rulesPath(loc);
+  const dir = path.dirname(file);
+  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
+
+  const RULE_CONTENT = `---
+name: codegraph-rules
+description: Defines when to use CodeGraph over native grep search.
+trigger: always_on
+---
+
+${INSTRUCTIONS_TEMPLATE}
+`;
+
+  let action: 'created' | 'updated' | 'unchanged' = 'created';
+  if (fs.existsSync(file)) {
+    const existing = fs.readFileSync(file, 'utf-8');
+    if (existing === RULE_CONTENT) {
+      action = 'unchanged';
+    } else {
+      action = 'updated';
+    }
+  }
+
+  if (action !== 'unchanged') {
+    fs.writeFileSync(file, RULE_CONTENT, 'utf-8');
+  }
+
+  return { path: file, action };
+}
+
+function cleanupLegacyFiles(): WriteResult['files'] {
+  const files: WriteResult['files'] = [];
+
+  // Cleanup wrong mcp config file
+  const oldMcpPath = path.join(os.homedir(), '.gemini', 'config', 'mcp_config.json');
+  if (fs.existsSync(oldMcpPath)) {
+    try {
+      const config = readJsonFile(oldMcpPath);
+      if (config?.mcpServers?.codegraph) {
+        delete config.mcpServers.codegraph;
+        if (Object.keys(config.mcpServers).length === 0) {
+          delete config.mcpServers;
+        }
+        writeJsonFile(oldMcpPath, config);
+        files.push({ path: oldMcpPath, action: 'updated' });
+      }
+    } catch {
+      // ignore
+    }
+  }
+
+  // Cleanup wrong instructions file
+  const oldInstrDir = path.join(os.homedir(), '.gemini', 'antigravity-ide', 'mcp', 'codegraph');
+  const oldInstr = path.join(oldInstrDir, 'instructions.md');
+  if (fs.existsSync(oldInstr)) {
+    try {
+      fs.unlinkSync(oldInstr);
+      files.push({ path: oldInstr, action: 'removed' });
+
+      // Cleanup empty dirs up to .gemini/antigravity-ide
+      if (fs.readdirSync(oldInstrDir).length === 0) fs.rmdirSync(oldInstrDir);
+      const parentDir = path.dirname(oldInstrDir);
+      if (fs.readdirSync(parentDir).length === 0) fs.rmdirSync(parentDir);
+    } catch {
+      // ignore
+    }
+  }
+
+  return files;
+}
+
+export const antigravityTarget: AgentTarget = new AntigravityTarget();

src/installer/targets/registry.ts

@@ -13,13 +13,15 @@ import { cursorTarget } from './cursor';
 import { codexTarget } from './codex';
 import { opencodeTarget } from './opencode';
 import { hermesTarget } from './hermes';
+import { antigravityTarget } from './antigravity';
 
 export const ALL_TARGETS: readonly AgentTarget[] = Object.freeze([
   claudeTarget,
   cursorTarget,
   codexTarget,
   opencodeTarget,
   hermesTarget,
+  antigravityTarget,
 ]);
 
 export function getTarget(id: string): AgentTarget | undefined {

src/installer/targets/types.ts

@@ -19,7 +19,7 @@ export type Location = 'global' | 'local';
  * lookup. New targets add a value here when they're added to the
  * registry. Keep these short and lowercase.
  */
-export type TargetId = 'claude' | 'cursor' | 'codex' | 'opencode' | 'hermes';
+export type TargetId = 'claude' | 'cursor' | 'codex' | 'opencode' | 'hermes' | 'antigravity';
 
 /**
  * Result of `target.detect(location)`.