vtcode-a2a

June 17, 2026 · View on GitHub

Agent2Agent (A2A) Protocol support for VT Code.

Overview

Layer 0 crate with zero internal vtcode dependencies. Provides the A2A protocol implementation for agent-to-agent communication, including agent discovery, task management, and webhook notifications.

Module Groups

Area	Modules	Description
Agent Card	`agent_card`	Agent discovery and capability advertisement
Client	`client`	A2A protocol client
CLI	`cli`	CLI interface for A2A commands
Errors	`errors`	A2A-specific error types
RPC	`rpc`	JSON-RPC message types and protocol constants
Server	`server`	HTTP server (feature-gated: `a2a-server`)
Task Manager	`task_manager`	Task lifecycle management
Types	`types`	Core A2A protocol types (Message, Task, Part, etc.)
Webhook	`webhook`	Push notification support

Key Concepts

Agent Card

Agent cards describe agent identity, version, capabilities, and security requirements. They enable agents to discover and communicate with each other.

Task Management

The task manager handles the lifecycle of A2A tasks, including creation, execution, and completion tracking.

Webhook Notifications

WebhookNotifier is always available (not feature-gated) — only the HTTP server is gated behind a2a-server.

Feature Flags

a2a-server — enables the HTTP server module
Feature chain: vtcode binary a2a-server → vtcode-core a2a-server → vtcode-a2a a2a-server

Rules

The server module is feature-gated behind a2a-server — never import unconditionally
shutdown_signal_logged() is defined in lib.rs (not a separate module)
Re-export facade in vtcode-core (a2a/mod.rs) must stay in sync with feature gates