Persistent Stdio

Boundline's Persistent Stdio architecture is the backbone of the V1 Framework Adapter Protocol. It allows Boundline to seamlessly integrate with external subprocess adapters (like speckit) without tying the runtime to complex remote APIs, brittle RPC frameworks, or heavy orchestrator SDKs.

The V1 Wire Contract

Integration with external frameworks is achieved exclusively through trusted local subprocess execution using standard input (stdin) and standard output (stdout).

The rules of the contract are strict:

• One-Shot Execution: Adapters are spawned for a specific bounded task, do their work, and exit. There is no persistent daemon or graceful shutdown logic required.
• UTF-8 JSON Payload: Boundline writes the entire execution context (including session state, config, and goals) to the adapter's stdin as a single, validated JSON payload.
• Deterministic Envelopes: The adapter MUST emit exactly one JSON payload to stdout before exiting. This payload must match a strict schema representing either a Success (with mutated state or plans) or an Error (with structured failure reasons).

Handling Stderr

Standard error (stderr) is treated strictly as an out-of-band enrichment channel:

• Adapters can stream logs, debugging info, and raw LLM reasoning traces to stderr.
• Boundline captures this stream but never uses it to mutate the session state machine.
• The stderr stream is saved into the .boundline/traces/ directory for human auditability and debugging purposes.

Security & Independence

Because the adapter surface relies entirely on local stdio, Boundline achieves total execution isolation:

• No Network Dependencies: Adapters don't need to expose ports, handle TCP connections, or manage authentication.
• Language Agnostic: An adapter can be written in Rust, Python, Node.js, or Go. As long as it can parse JSON from stdin and print JSON to stdout, it is a fully compatible framework adapter.
• Strict Host Ownership: Boundline (the host) retains absolute control over capability validation, config persistence, and operator-visible output. If an adapter crashes, Boundline simply records the failure and recovers the session.