Upgrading Contract and Exo Objects

Long-Lived Upgradable Objects in Agoric

Understanding Exos (Exposed Objects)

An Exo in Agoric is an exposed, remotable object that persists across contract upgrades. Think of it like a permanent employee in a company - they maintain their role and knowledge even when company policies change. Exos use InterfaceGuard for protection.

What Makes an Exo Special?

• Durability: Survives contract upgrades
• Remote Accessibility: Can be accessed from other parts of the system
• State Persistence: Maintains its state across upgrades
• Interface Guarantees: Provides consistent API access

Interface Guard Protection

• Acts as a protective layer around Exo objects
• Validates method calls and arguments
• Ensures only allowed operations are performed
• Maintains security during upgrades

Durability Through Zones

Zone Capabilities

• Provides API for creating Exo objects
• Manages object collections (Stores)
• Supports different persistence types:
• Ephemeral (JS heap)
• Virtual (disk storage)
• Durable (upgrade survival)

Baggage System

• Preserves state during upgrades
• Acts like a secure container for contract data
• Ensures continuity of operations
• Maintains object relationships

Upgrade Process

Preparation

• Define what state needs to be preserved
• Plan new features or modifications
• Ensure backward compatibility

Implementation

• Create new contract version
• Define state transitions
• Update interfaces as needed