> ## 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.
# Failover
> Automatic backup when things fail
Agents can failover to backup models when the primary fails.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
graph LR
subgraph "Automatic Failover"
A[📤 Request] --> B[🤖 Primary]
B -->|Fails| C[🤖 Backup]
C --> D[✅ Success]
end
classDef agent fill:#8B0000,stroke:#7C90A0,color:#fff
classDef tool fill:#189AB4,stroke:#7C90A0,color:#fff
class B agent
class A,C,D tool
classDef agent fill:#8B0000,color:#fff
classDef tool fill:#189AB4,color:#fff
```
## Quick Start
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
import { Agent } from 'praisonai';
const agent = new Agent({
llm: 'gpt-4o',
fallback: ['gpt-4-turbo', 'gpt-3.5-turbo']
});
await agent.chat('Hello');
// Uses gpt-4o, falls back if unavailable
```
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
const agent = new Agent({
llm: 'gpt-4o',
fallback: [
'anthropic/claude-3',
'google/gemini-pro'
]
});
```
***
## User Interaction Flow
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
sequenceDiagram
participant User
participant Agent
participant LLM1 as GPT-4o
participant LLM2 as Backup
User->>Agent: Request
Agent->>LLM1: Try primary
LLM1--xAgent: Fail
Agent->>LLM2: Try backup
LLM2-->>Agent: Success
Agent-->>User: Response
```
***
## Configuration Levels
```typescript theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
// Level 1: Array - Simple fallback list
const agent = new Agent({
llm: 'gpt-4o',
fallback: ['gpt-4-turbo', 'gpt-3.5-turbo']
});
// Level 2: Dict - With options
const agent = new Agent({
llm: 'gpt-4o',
fallback: {
models: ['gpt-4-turbo', 'gpt-3.5-turbo'],
retries: 2
}
});
// Level 3: Instance - Full control
const agent = new Agent({
failover: {
primary: 'gpt-4o',
fallbacks: ['gpt-4-turbo', 'claude-3'],
strategy: 'round-robin', // or 'priority'
healthCheck: true
}
});
```
***
## Failover Options
| Option | Description |
| ------------- | ---------------------- |
| `fallback` | Backup models list |
| `retries` | Attempts per model |
| `strategy` | How to select backup |
| `healthCheck` | Skip known-down models |
***
## API Reference
Complete configuration options
Manager class documentation
***
## Best Practices
Use lower-cost models as last resort.
Different providers have different outages.
Verify backups work before production.
***
## Related
Execution settings
LLM providers