Local Effects Runtime

The local effects runtime turns the host runtime ABI into application-level

operations for files, command-line state, environment, and subprocesses.

Filesystem

Required file behavior:

• read text through runtime-read-text;
• write text through runtime-write-text;
• atomic write through runtime-atomic-write-text;
• temp, config, cache, and home directory discovery;
• permission checks through runtime-permissions;
• advisory lock and unlock through runtime-lock and runtime-unlock;
• deterministic directory walk through runtime-directory-walk;
• local artifact and capture storage;
• safe path normalization that rejects parent traversal outside the root.

Environment And CLI

Required CLI behavior:

• argv projection through runtime-argv;
• environment lookup through runtime-env-get;
• stdout and stderr writes through runtime-stdout and runtime-stderr;
• exit code policy through runtime-exit-code;
• stable command error reporting through runtime-command-error.

Subprocess

Structured subprocess calls use argv arrays, cwd, env overrides, timeout, and

stdin policy. The default path never invokes a shell. Shell execution must be an

explicit runtime-process-shell call.

Subprocess results capture stdout, stderr, exit code, elapsed time, timeout

status, and a stable error code. Timed-out process groups are terminated before

the result is returned.