Module transport 

Generic JSON-RPC-over-stdio transport for subprocess agents.

StdioTransport handles the low-level framing of newline-delimited JSON over a child process’s stdin/stdout pair. It is intentionally protocol-agnostic: it knows nothing about Copilot, ACP sessions, or any other higher-level concept.

Message routing

The internal reader task inspects each incoming line and dispatches it as follows:

• Response (has result or error field with a numeric id): looked up in the pending table populated by StdioTransport::call and delivered to the waiting caller via a tokio::sync::oneshot channel.
• Request / notification (anything else): forwarded to the closure registered via StdioTransport::set_notification_handler.

Stderr lines are forwarded to tracing::debug! under the vtcode.stdio_transport.stderr target.

Backpressure

The write channel is bounded (capacity 64) to prevent unbounded memory growth if the subprocess is slow to consume stdin. send_raw uses try_send and returns an error if the channel is full, rather than blocking or growing without bound.

Structs

StdioTransport

Generic JSON-RPC-over-stdio transport for local subprocess agents.

StdioTransportOptions