displayName
stdio
kind
stdio
description
Plain stdin/stdout pipe to the agent process. The simplest invocation
shape; used by CI runners, the babysitter harness, and most CLI tools
when they spawn an agent for a single task.
inboundMessageFormat
Per-agent. Common patterns:
- Single JSON object on stdin, EOF terminates the request (one-shot
mode used by most CI invocations).
- Newline-delimited JSON (JSONL) when the host streams multiple
turns / tool results into the agent across a single session.
- Free-form text prompt on stdin (legacy / interactive REPL agents).
The agent's CLI surface (flags, env vars) configures which shape is
expected; no cross-vendor standard exists. Agent-specific stdin
formats are recorded on the AgentVersion node via per-edge
evidence rather than duplicated on this transport node.
outboundMessageFormat
Per-agent. Common patterns:
- Newline-delimited JSON (JSONL) event stream on stdout, one event
per line (e.g. Claude Code `--output-format stream-json`,
Codex CLI session events).
- Single JSON document on stdout for one-shot invocations.
- Plain text / ANSI-coloured output for interactive agents.
stderr is reserved for human-readable diagnostics and is NOT part of
the structured wire surface.
signalForwarding
POSIX signals on the child process:
- SIGINT — interrupt the current turn (graceful cancel; agent should
flush partial output and return).
- SIGTERM — request a clean shutdown.
- SIGKILL — last-resort termination (no cleanup).
On Windows, hosts typically use `GenerateConsoleCtrlEvent(CTRL_C_EVENT)`
or `TerminateProcess`. Closing stdin (EOF) is also commonly used to
signal end-of-input without sending a signal.
ptySemantics
Plain stdio — the agent is invoked with anonymous pipes for
stdin/stdout/stderr; `isatty()` returns false on all three. ANSI
colour codes, prompt redraws, and raw-mode keystrokes are not
available. Hosts that need TTY behaviour use
`agent-host-transport:stdio-pty` instead.