> ## Documentation Index
> Fetch the complete documentation index at: https://praison.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Middleware
> Intercept agent requests and responses
Agents can use middleware to process requests and responses - for logging, validation, or transformation.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
graph LR
subgraph "Request Pipeline"
A[📤 Input] --> B[🔧 Middleware]
B --> C[🤖 Agent]
C --> D[🔧 Middleware]
D --> E[📥 Output]
end
classDef agent fill:#8B0000,color:#fff
classDef tool fill:#189AB4,color:#fff
class C agent
class A,B,D,E tool
```
## Quick Start
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
import { Agent, Middleware } from 'praisonai';
const logger: Middleware = async (ctx, next) => {
console.log('Input:', ctx.input);
await next();
console.log('Output:', ctx.output);
};
const agent = new Agent({
instructions: 'You are helpful',
middleware: [logger]
});
```
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
const validate: Middleware = async (ctx, next) => {
if (ctx.input.length > 1000) {
throw new Error('Input too long');
}
await next();
};
```
***
## User Interaction Flow
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
sequenceDiagram
participant User
participant MW1 as Logger
participant Agent
participant MW2 as Filter
User->>MW1: Request
MW1->>Agent: Log + forward
Agent-->>MW2: Response
MW2-->>User: Filter + forward
```
***
## Configuration Levels
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
// Level 1: Array - Middleware list
const agent = new Agent({
middleware: [logger, validator]
});
// Level 2: Function - Simple middleware
const agent = new Agent({
middleware: [
async (ctx, next) => {
console.log(ctx.input);
await next();
}
]
});
// Level 3: Instance - Full control
const agent = new Agent({
middleware: [
{
name: 'logger',
handler: loggerFn,
order: 1
},
{
name: 'cache',
handler: cacheFn,
order: 2
}
]
});
```
***
## Common Uses
| Use Case | Description |
| -------------- | ------------------------------ |
| Logging | Track all requests/responses |
| Validation | Check inputs before processing |
| Transformation | Modify data in transit |
| Caching | Cache frequent responses |
***
## API Reference
Hooks configuration (middleware pattern)
***
## Best Practices
Each middleware should do one thing well.
Middleware runs in order - put validation first.
Forgetting next() breaks the chain.
***
## Related
Lifecycle hooks
Input validation