# OpenWebUI Plugin Development Guide

> This guide consolidates official documentation, SDK details, and best practices to provide a systematic tutorial for developers, from beginner to expert.

## 📚 Table of Contents

1.  [Quick Start](#1-quick-start)
2.  [Core Concepts & SDK Details](#2-core-concepts--sdk-details)
3.  [Deep Dive into Plugin Types](#3-deep-dive-into-plugin-types)
    *   [Action](#31-action)
    *   [Filter](#32-filter)
    *   [Pipe](#33-pipe)
4.  [Advanced Development Patterns](#4-advanced-development-patterns)
5.  [Best Practices & Design Principles](#5-best-practices--design-principles)
6.  [Troubleshooting](#6-troubleshooting)

---

## 1. Quick Start

### 1.1 What are OpenWebUI Plugins?

OpenWebUI Plugins (officially called "Functions") are the primary way to extend the platform's capabilities. Running in a backend Python environment, they allow you to:
*   🔌 **Integrate New Models**: Connect to Claude, Gemini, or custom RAGs via Pipes.
*   🎨 **Enhance Interaction**: Add buttons (e.g., "Export", "Generate Chart") next to messages via Actions.
*   🔧 **Intervene in Processes**: Modify data before requests or after responses (e.g., inject context, filter sensitive words) via Filters.

### 1.2 Your First Plugin (Hello World)

Save the following code as `hello.py` and upload it to the **Functions** panel in OpenWebUI:

```python
"""
title: Hello World Action
author: Demo
version: 1.0.0
"""

from pydantic import BaseModel, Field
from typing import Optional

class Action:
    class Valves(BaseModel):
        greeting: str = Field(default="Hello", description="Greeting message")

    def __init__(self):
        self.valves = self.Valves()

    async def action(
        self,
        body: dict,
        __event_emitter__=None,
        __user__=None
    ) -> Optional[dict]:
        user_name = __user__.get("name", "Friend") if __user__ else "Friend"
        
        if __event_emitter__:
            await __event_emitter__({
                "type": "notification",
                "data": {"type": "success", "content": f"{self.valves.greeting}, {user_name}!"}
            })
        return body
```

---

## 2. Core Concepts & SDK Details

### 2.1 ⚠️ Important: Sync vs Async

OpenWebUI plugins run within an `asyncio` event loop.
*   **Principle**: All I/O operations (database, file, network) must be non-blocking.
*   **Pitfall**: Calling synchronous methods directly (e.g., `time.sleep`, `requests.get`) will freeze the entire server.
*   **Solution**: Wrap synchronous calls using `await asyncio.to_thread(sync_func, ...)`.

### 2.2 Core Parameters

All plugin methods (`inlet`, `outlet`, `pipe`, `action`) support injecting the following special parameters:

| Parameter | Type | Description |
| :--- | :--- | :--- |
| `body` | `dict` | **Core Data**. Contains request info like `messages`, `model`, `stream`. |
| `__user__` | `dict` | **Current User**. Contains `id`, `name`, `role`, `valves` (user config), etc. |
| `__metadata__` | `dict` | **Metadata**. Contains `chat_id`, `message_id`. The `variables` field holds preset variables like `{{USER_NAME}}`, `{{CURRENT_TIME}}`. |
| `__request__` | `Request` | **FastAPI Request Object**. Access `app.state` for cross-plugin communication. |
| `__event_emitter__` | `func` | **One-way Notification**. Used to send Toast notifications or status bar updates. |
| `__event_call__` | `func` | **Two-way Interaction**. Used to execute JS code, show confirmation dialogs, or input boxes on the frontend. |

### 2.3 Configuration System (Valves)

*   **`Valves`**: Global admin configuration.
*   **`UserValves`**: User-level configuration (higher priority, overrides global).

```python
class Filter:
    class Valves(BaseModel):
        API_KEY: str = Field(default="", description="Global API Key")
        
    class UserValves(BaseModel):
        API_KEY: str = Field(default="", description="User Private API Key")
        
    def inlet(self, body, __user__):
        # Prioritize user's Key
        user_valves = __user__.get("valves", self.UserValves())
        api_key = user_valves.API_KEY or self.valves.API_KEY
```

---

## 3. Deep Dive into Plugin Types

### 3.1 Action

**Role**: Adds buttons below messages that trigger upon user click.

**Advanced Usage: Execute JavaScript on Frontend (File Download Example)**

```python
import base64

async def action(self, body, __event_call__):
    # 1. Generate content on backend
    content = "Hello OpenWebUI".encode()
    b64 = base64.b64encode(content).decode()
    
    # 2. Send JS to frontend for execution
    js = f"""
    const blob = new Blob([atob('{b64}')], {{type: 'text/plain'}});
    const a = document.createElement('a');
    a.href = URL.createObjectURL(blob);
    a.download = 'hello.txt';
    a.click();
    """
    await __event_call__({"type": "execute", "data": {"code": js}})
```

### 3.2 Filter

**Role**: Middleware that intercepts and modifies requests/responses.

*   **`inlet`**: Before request. Used for injecting context, modifying model parameters.
*   **`outlet`**: After response. Used for formatting output, logging.
*   **`stream`**: During streaming. Used for real-time sensitive word filtering.

**Example: Injecting Environment Variables**

```python
async def inlet(self, body, __metadata__):
    vars = __metadata__.get("variables", {})
    context = f"Current Time: {vars.get('{{CURRENT_DATETIME}}')}"
    
    # Inject into System Prompt or first message
    if body.get("messages"):
        body["messages"][0]["content"] += f"\n\n{context}"
    return body
```

### 3.3 Pipe

**Role**: Custom Model/Agent.

**Example: Simple OpenAI Wrapper**

```python
import requests

class Pipe:
    def pipes(self):
        return [{"id": "my-gpt", "name": "My GPT Wrapper"}]

    def pipe(self, body):
        # Modify body here, e.g., force add prompt
        headers = {"Authorization": f"Bearer {self.valves.API_KEY}"}
        r = requests.post("https://api.openai.com/v1/chat/completions", json=body, headers=headers, stream=True)
        return r.iter_lines()
```

---

## 4. Advanced Development Patterns

### 4.1 Pipe & Filter Collaboration
Use `__request__.app.state` to share data between plugins.
*   **Pipe**: `__request__.app.state.search_results = [...]`
*   **Filter (Outlet)**: Read `search_results` and format them as citation links appended to the response.

### 4.2 Async Background Tasks
Execute time-consuming operations (e.g., summarization, database storage) in the background without blocking the user response.

```python
import asyncio

async def outlet(self, body, __metadata__):
    asyncio.create_task(self.background_job(__metadata__["chat_id"]))
    return body

async def background_job(self, chat_id):
    # Execute time-consuming operation...
    pass
```

---

## 5. Best Practices & Design Principles

### 5.1 Naming & Positioning
*   **Short & Punchy**: e.g., "FlashCard", "DeepRead". Avoid generic terms like "Text Analysis Assistant".
*   **Complementary**: Don't reinvent the wheel; clarify what specific problem your plugin solves.

### 5.2 User Experience (UX)
*   **Timely Feedback**: Send a `notification` ("Generating...") before time-consuming operations.
*   **Visual Appeal**: When Action outputs HTML, use modern CSS (rounded corners, shadows, gradients).
*   **Smart Guidance**: If text is too short, prompt the user: "Suggest entering more content for better results".

### 5.3 Error Handling
Never let a plugin fail silently. Catch exceptions and inform the user via `__event_emitter__`.

```python
try:
    # Business logic
except Exception as e:
    await __event_emitter__({
        "type": "notification",
        "data": {"type": "error", "content": f"Processing failed: {str(e)}"}
    })
```

---

## 6. Troubleshooting

*   **HTML not showing?** Ensure it's wrapped in a ` ```html ... ``` ` code block.
*   **Database error?** Check if you called synchronous DB methods directly in an `async` function; use `asyncio.to_thread`.
*   **Parameters not working?** Check if `Valves` are defined correctly and if they are being overridden by `UserValves`.