> ## Documentation Index
> Fetch the complete documentation index at: https://docs.train.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Edge Cases

> Describes potential failure scenarios and how the protocol handles them to ensure fund safety and transaction integrity

### Solver Fails to Act on the User's Lock

In a rare scenario where the selected Solver fails to act on the User's lock, the User only needs to wait for the timelock period (usually \~15 minutes) to receive their funds back.

<Accordion title="Sequence Diagram" icon="brake-warning">
  ```mermaid theme={null}
  sequenceDiagram
      participant User
      participant SC as Source Chain
      participant Solver
      participant DC as Destination Chain

  	
      User->>SC: lock() with hashlock
      SC-->>Solver: TokenLocked
      
      Note over User,SC: Timelock passes
      User->>SC: refund()
      SC-->>User: TokenRefunded
  ```
</Accordion>

### User Fails to Transmit Secret to Solver

If the User does not transmit the derived secret to the Solver in time, both parties can refund their funds after the timelock period expires.

<Accordion title="Sequence Diagram" icon="brake-warning">
  ```mermaid theme={null}
  sequenceDiagram
      participant User
      participant SC as Source Chain
      participant Solver
      participant DC as Destination Chain

  	
      User->>SC: lock() with hashlock
      SC-->>Solver: TokenLocked
      Solver->>DC: lock() with same hashlock
      DC-->>User: TokenLocked
      
      Note over User,SC: Timelock passes
      User->>SC: refund()
      SC-->>User: TokenRefunded
  		
  		Note over Solver,DC: Timelock passes
      Solver->>DC: refund()
      DC-->>Solver: TokenRefunded
  ```
</Accordion>

### Solver Fails to Release the User's Funds

In scenarios where the Solver releases their own funds but fails to release the User's funds, the protocol provides two mechanisms:

1. **Manual Redemption**: The User already possesses the secret (they transmitted it to the Solver). If the Solver fails to redeem on the destination chain, the User can directly use the secret to manually redeem their own funds on the destination chain, bypassing the Solver's failure.

2. **Reward Mechanism**: Other actors can redeem on behalf of the user and earn a reward for completing the swap. The original Solver loses their reward by failing to act in time.

<Accordion title="Sequence Diagram" icon="brake-warning">
  ```mermaid theme={null}
  sequenceDiagram
      participant User
      participant SC as Source Chain
      participant Solver
      participant DC as Destination Chain

  	
      User->>SC: lock() with hashlock
      SC-->>Solver: TokenLocked
      Solver->>DC: lock() with same hashlock
      DC-->>User: TokenLocked
      User->>Solver: sign(secret)
      Solver->>SC: redeem(secret)
      SC-->>Solver: TokenRedeemed
      User->>DC: redeem(secret)
      DC-->>User: TokenRedeemed
  ```
</Accordion>

### Solver Fails to Release Any Funds

If the Solver fails to release any funds, both the User and Solver can wait for the timelock period to expire and then refund their funds.

<Accordion title="Sequence Diagram" icon="brake-warning">
  ```mermaid theme={null}
  sequenceDiagram
      participant User
      participant SC as Source Chain
      participant Solver
      participant DC as Destination Chain

  	
      User->>SC: lock() with hashlock
      SC-->>Solver: TokenLocked
      Solver->>DC: lock() with same hashlock
      DC-->>User: TokenLocked
      User->>Solver: sign(secret)
      Note over Solver,DC: Timelock passes
      Solver->>DC: refund()
      DC-->>Solver: TokenRefunded
      Note over User,SC: Timelock passes
      User->>SC: refund()
      SC-->>User: TokenRefunded
  ```
</Accordion>