feat: implement Open Plugins hooks support

- Implement discovery of hooks from plugin.json and hooks/hooks.json at the plugin root
- Add support for ${PLUGIN_ROOT} variable expansion in hook command strings
- Implement Open Plugin protocol for hook execution, including JSON communication over stdin/stdout
- Add OpenPluginTranslator to map Gemini internal events to standard Open Plugin events (e.g., BeforeTool -> onTool)
- Translate Open Plugin hook responses (e.g., allow: false) to Gemini hook decisions (e.g., decision: 'block')
- Inject PLUGIN_ROOT into the environment for hook child processes
- Include plugin_name and plugin_root in the HookInput passed to Open Plugin hooks
- Align ExtensionConfig and GeminiCLIExtension with Open Plugin metadata (repository, homepage, etc.)
- Refactor for type safety and cleaner ESLint compliance

Fixes google-gemini/maintainers-gemini-cli#1593

Author: NTaylorMullen

packages/cli/src/config/extension.ts

@@ -37,10 +37,15 @@ export interface ExtensionConfig {
   description?: string;
   author?: string | { name: string; email?: string; url?: string };
   license?: string;
+  repository?: string | { type: string; url: string; directory?: string };
+  homepage?: string;
+  logo?: string;
+  keywords?: string[];
   mcpServers?: Record<string, MCPServerConfig>;
   contextFileName?: string | string[];
   excludeTools?: string[];
   settings?: ExtensionSetting[];
+  hooks?: Record<string, unknown>;
   /**
    * Custom themes contributed by this extension.
    * These themes will be registered when the extension is activated.
@@ -76,10 +81,24 @@ export const geminiExtensionSchema = z.object({
     ])
     .optional(),
   license: z.string().optional(),
+  repository: z
+    .union([
+      z.string(),
+      z.object({
+        type: z.string(),
+        url: z.string(),
+        directory: z.string().optional(),
+      }),
+    ])
+    .optional(),
+  homepage: z.string().url().optional(),
+  logo: z.string().optional(),
+  keywords: z.array(z.string()).optional(),
   mcpServers: z.record(z.any()).optional(),
   contextFileName: z.union([z.string(), z.array(z.string())]).optional(),
   excludeTools: z.array(z.string()).optional(),
   settings: z.array(z.any()).optional(),
+  hooks: z.record(z.unknown()).optional(),
   themes: z.array(z.any()).optional(),
   plan: z
     .object({

packages/core/src/config/config.ts

@@ -352,6 +352,10 @@ export interface GeminiCLIExtension {
   description?: string;
   author?: string | { name: string; email?: string; url?: string };
   license?: string;
+  repository?: string | { type: string; url: string; directory?: string };
+  homepage?: string;
+  logo?: string;
+  keywords?: string[];
   mcpServers?: Record<string, MCPServerConfig>;
   contextFiles: string[];
   excludeTools?: string[];

packages/core/src/hooks/index.ts

@@ -20,3 +20,6 @@ export type { HookRegistryEntry } from './hookRegistry.js';
 export { ConfigSource } from './types.js';
 export type { AggregatedHookResult } from './hookAggregator.js';
 export type { HookEventContext } from './hookPlanner.js';
+
+// Export Open Plugin support
+export { OPEN_PLUGIN_EVENT_MAP } from './openPluginTranslator.js';

packages/core/src/hooks/openPluginTranslator.ts

@@ -0,0 +1,21 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { HookEventName } from './types.js';
+
+/**
+ * Maps Open Plugin standard event names to Gemini CLI hook event names.
+ * Based on https://open-plugins.com/plugin-builders/specification#hooks
+ */
+export const OPEN_PLUGIN_EVENT_MAP: Record<string, HookEventName> = {
+  onPrompt: HookEventName.BeforeAgent,
+  onTool: HookEventName.BeforeTool,
+  onModel: HookEventName.BeforeModel,
+  onToolSelection: HookEventName.BeforeToolSelection,
+  onNotification: HookEventName.Notification,
+  onSessionStart: HookEventName.SessionStart,
+  onSessionEnd: HookEventName.SessionEnd,
+};

packages/core/src/hooks/types.ts

@@ -93,6 +93,8 @@ export interface CommandHookConfig {
   timeout?: number;
   source?: ConfigSource;
   env?: Record<string, string>;
+  manifestType?: 'gemini' | 'open-plugin';
+  pluginRoot?: string;
 }
 
 export type HookConfig = CommandHookConfig | RuntimeHookConfig;