Agents can now be serialized to JSON and rebuilt

Agents built with the SDK can now be serialized to JSON and reconstructed later. A new describe() method exports a complete agent configuration as a schema object, while fromSchema() reconstructs a fully functional agent from that schema. This rounds out the agent lifecycle: build fluently, export the config, store it, and rebuild anywhere.

The credential provider solves the problem of embedding raw API keys in agent code. Instead of passing secret keys directly, developers can reference a credential by name or ID. The provider resolves these references at build time, keeping credentials out of source code and enabling proper secret management.

A companion feature generates TypeScript code from any agent schema. This closes the loop between visual editing, JSON storage, and code generation — agents can be designed in a UI, serialized, and converted back to portable code.

In the agents SDK, these changes wire together serialization, reconstruction, and sandboxed execution through new types including AgentSchema, CredentialProvider, and HandlerExecutor. The agent itself gains a builder interface that avoids circular dependencies between the main class and reconstruction logic.