Creating OpenCode Plugins

Overview

OpenCode plugins are JavaScript/TypeScript modules that hook into 25+ events across the OpenCode AI assistant lifecycle. Plugins export an async function receiving context (project, client, $, directory, worktree) and return an event handler.

When to Use

Create an OpenCode plugin when:

• Intercepting file operations (prevent sharing .env files)
• Monitoring command execution (notifications, logging)
• Processing LSP diagnostics (custom error handling)
• Managing permissions (auto-approve trusted operations)
• Reacting to session lifecycle (cleanup, initialization)
• Extending tool capabilities (custom tool registration)
• Enhancing TUI interactions (custom prompts, toasts)

Don't create for:

• Simple prompt instructions (use agents instead)
• One-time scripts (use bash tools)
• Static configuration (use settings files)

Quick Reference

Plugin Structure

export const MyPlugin = async (context) => {
  // context: { project, client, $, directory, worktree }

  return {
    event: async ({ event }) => {
      // event: { type: 'event.name', data: {...} }

      switch(event.type) {
        case 'file.edited':
          // Handle file edits
          break;
        case 'tool.execute.before':
          // Pre-process tool execution
          break;
      }
    }
  };
};

Event Categories

Category	Events	Use Cases
command	command.executed	Track command history, notifications
file	file.edited, file.watcher.updated	File validation, auto-formatting
installation	installation.updated	Dependency tracking
lsp	lsp.client.diagnostics, lsp.updated	Custom error handling
message	message.*.updated/removed	Message filtering, logging
permission	permission.replied/updated	Permission policies
server	server.connected	Connection monitoring
session	session.created/deleted/error/idle/status/updated/compacted/diff	Session management
todo	todo.updated	Todo synchronization
tool	tool.execute.before/after	Tool interception, augmentation
tui	tui.prompt.append, tui.command.execute, tui.toast.show	UI customization

Plugin Manifest (package.json or separate config)

{
  "name": "env-protection",
  "description": "Prevents sharing .env files",
  "version": "1.0.0",
  "author": "Security Team",
  "plugin": {
    "file": "plugin.js",
    "location": "global"
  },
  "hooks": {
    "file": ["file.edited"],
    "permission": ["permission.replied"]
  }
}

Implementation

Complete Example: Environment File Protection

// .opencode/plugin/env-protection.js

export const EnvProtectionPlugin = async ({ project, client }) => {
  const sensitivePatterns = [
    /\.env$/,
    /\.env\..+$/,
    /credentials\.json$/,
    /\.secret$/,
  ];

  const isSensitiveFile = (filePath) => {
    return sensitivePatterns.some(pattern => pattern.test(filePath));
  };

  return {
    event: async ({ event }) => {
      switch (event.type) {
        case 'file.edited': {
          const { path } = event.data;

          if (isSensitiveFile(path)) {
            console.warn(`⚠️  Sensitive file edited: ${path}`);
            console.warn('This file should not be shared or committed.');
          }
          break;
        }

        case 'permission.replied': {
          const { action, target, decision } = event.data;

          // Block read/share operations on sensitive files
          if ((action === 'read' || action === 'share') &&
              isSensitiveFile(target) &&
              decision === 'allow') {

            console.error(`🚫 Blocked ${action} operation on sensitive file: ${target}`);

            // Override permission decision
            return {
              override: true,
              decision: 'deny',
              reason: 'Sensitive file protection policy'
            };
          }
          break;
        }
      }
    }
  };
};

Example: Command Execution Notifications

// .opencode/plugin/notify.js

export const NotifyPlugin = async ({ project, $ }) => {
  let commandStartTime = null;

  return {
    event: async ({ event }) => {
      switch (event.type) {
        case 'command.executed': {
          const { command, args, status } = event.data;
          commandStartTime = Date.now();

          console.log(`▶️  Executing: ${command} ${args.join(' ')}`);
          break;
        }

        case 'tool.execute.after': {
          const { tool, duration, success } = event.data;

          if (duration > 5000) {
            // Notify for long-running operations
            await $`osascript -e 'display notification "Completed in ${duration}ms" with title "${tool}"'`;
          }

          console.log(`✅ ${tool} completed in ${duration}ms`);
          break;
        }
      }
    }
  };
};

Example: Custom Tool Registration

// .opencode/plugin/custom-tools.js

export const CustomToolsPlugin = async ({ client }) => {
  // Register custom tool on initialization
  await client.registerTool({
    name: 'lint',
    description: 'Run linter on current file with auto-fix option',
    parameters: {
      type: 'object',
      properties: {
        fix: {
          type: 'boolean',
          description: 'Auto-fix issues'
        }
      }
    },
    handler: async ({ fix }) => {
      const result = await $`eslint ${fix ? '--fix' : ''} .`;
      return {
        output: result.stdout,
        errors: result.stderr
      };
    }
  });

  return {
    event: async ({ event }) => {
      // Monitor tool usage
      if (event.type === 'tool.execute.before') {
        console.log(`🔧 Tool: ${event.data.tool}`);
      }
    }
  };
};

Installation Locations

Location	Path	Scope	Use Case
Global	~/.config/opencode/plugin/	All projects	Security policies, global utilities
Project	.opencode/plugin/	Current project	Project-specific hooks, validators

Common Mistakes

Mistake	Why It Fails	Fix
Synchronous event handler	Blocks event loop	Use async handlers
Missing error handling	Plugin crashes on error	Wrap in try/catch
Heavy computation in handler	Slows down operations	Defer to background process
Mutating event data directly	Causes side effects	Return override object
Not checking event type	Handles wrong events	Use switch/case on event.type
Forgetting context destructuring	Missing key utilities	Destructure { project, client, $, directory, worktree }

Event Data Structures

// File Events
interface FileEditedEvent {
  type: 'file.edited';
  data: {
    path: string;
    content: string;
    timestamp: number;
  };
}

// Tool Events
interface ToolExecuteBeforeEvent {
  type: 'tool.execute.before';
  data: {
    tool: string;
    args: Record<string, any>;
    user: string;
  };
}

interface ToolExecuteAfterEvent {
  type: 'tool.execute.after';
  data: {
    tool: string;
    duration: number;
    success: boolean;
    output?: any;
    error?: string;
  };
}

// Permission Events
interface PermissionRepliedEvent {
  type: 'permission.replied';
  data: {
    action: 'read' | 'write' | 'execute' | 'share';
    target: string;
    decision: 'allow' | 'deny';
  };
}

Testing Plugins

// Test plugin locally before installation
import { EnvProtectionPlugin } from './env-protection.js';

const mockContext = {
  project: { root: '/test/project' },
  client: {},
  $: async (cmd) => ({ stdout: '', stderr: '' }),
  directory: '/test/project',
  worktree: null
};

const plugin = await EnvProtectionPlugin(mockContext);

// Simulate event
await plugin.event({
  event: {
    type: 'file.edited',
    data: { path: '.env', content: 'SECRET=123', timestamp: Date.now() }
  }
});

Real-World Impact

Security: Prevent accidental sharing of credentials (env-protection plugin blocks .env file reads)

Productivity: Auto-notify on long-running commands (notify plugin sends system notifications)

Quality: Auto-format files on save (file.edited hook runs prettier)

Monitoring: Track tool usage patterns (tool.execute hooks log analytics)

Claude Code Event Mapping

When porting Claude Code hook behavior to OpenCode plugins, use these event mappings:

Claude Hook	OpenCode Event	Description
PreToolUse	tool.execute.before	Run before tool execution, can block
PostToolUse	tool.execute.after	Run after tool execution
UserPromptSubmit	message.* events	Process user prompts
SessionEnd	session.idle	Session completion

Example: Claude-like Hook Behavior

export const CompatiblePlugin = async (context) => {
  return {
    // Equivalent to Claude's PreToolUse hook
    'tool.execute.before': async (input, output) => {
      if (shouldBlock(input)) {
        throw new Error('Blocked by policy');
      }
    },

    // Equivalent to Claude's PostToolUse hook
    'tool.execute.after': async (result) => {
      console.log(`Tool completed: ${result.tool}`);
    },

    // Equivalent to Claude's SessionEnd hook
    event: async ({ event }) => {
      if (event.type === 'session.idle') {
        await cleanup();
      }
    }
  };
};

Plugin Composition

Combine multiple plugins using opencode-plugin-compose:

import { compose } from "opencode-plugin-compose";

const composedPlugin = compose([
  envProtectionPlugin,
  notifyPlugin,
  customToolsPlugin
]);
// Runs all hooks in sequence

Non-Convertibility Note

Important: OpenCode plugins cannot be directly converted from Claude Code hooks due to fundamental differences:

• Event models differ: Claude has 4 hook events, OpenCode has 32+
• Formats differ: Claude uses executable scripts, OpenCode uses JS/TS modules
• Execution context differs: Different context objects and return value semantics

When porting Claude hooks to OpenCode plugins, you'll need to rewrite the logic using the OpenCode plugin API.

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Schema Reference: packages/converters/schemas/opencode-plugin.schema.json

Documentation: https://opencode.ai/docs/plugins/