shell

name	shell
tags	shell, exec, filesystem, jobs, sandbox
description	Run Unix commands and structured filesystem ops from the iii engine: exec, background jobs, and a structured fs (ls/stat/mkdir/rm/chmod/mv/grep/sed/ read/write, jailed only if fs.host_roots is configured), all forwardable into a sandbox microVM.

shell

The shell worker is the single door every agent uses to touch the OS: run a build, call a CLI, read a file, list a directory. Routing it all through shell::* and shell::fs::* keeps a denylist, timeouts, output caps, and an optional host-root jail (unjailed by default — see Boundaries) in one enforceable place. Both surfaces take an optional target field that forwards the call into a live iii-sandbox microVM, so the same denylist gates host and sandbox execution alike.

Host-targeted shell::exec is not an isolation boundary. The denylist is a regex tripwire on argv.join(" "), and any interpreter (sh, node, python3) can construct any forbidden token at runtime to bypass it. Run untrusted input with target: { kind: "sandbox", sandbox_id }. Prefer the shell::fs::* backends over exec-ing ls/stat/grep/rg: they stay in-process, honor fs.host_roots when it's configured, and return structured results.

Sandbox forwarding (and shell::fs::* into a VM) requires the iii-sandbox worker; iii trigger compose::add worker=shell does not pull it in. To surface shell::* to LLM agents, pair with the skills worker.

When to Use

• Run a one-shot command and block for its full output: git status, wc, head, a quick compile probe (shell::exec).
• Kick off long work (build, watcher, wide grep) without blocking the turn, then poll for completion (shell::exec_bg + shell::status).
• Survey or terminate in-flight background jobs (shell::list, shell::kill).
• List, stat, or read files with structured output instead of shelling out to ls/stat/cat (shell::fs::ls, shell::fs::stat, shell::fs::read).
• Search or rewrite across a tree without spawning rg/sed (shell::fs::grep, shell::fs::sed).
• Create, move, remove, or re-permission paths (jailed only if fs.host_roots is set) (shell::fs::mkdir, shell::fs::mv, shell::fs::rm, shell::fs::chmod).
• Persist a generated artefact, or bootstrap files into a sandbox, by streaming bytes to a path (shell::fs::write with a target).

Boundaries

• Host shell::exec is not a security sandbox: the denylist is bypassable by any interpreter. Run untrusted commands with target: sandbox (needs iii-sandbox).
• shell::fs::* honors fs.host_roots as a jail WHEN it's set — empty (the shipped default) means unjailed, confined only by fs.denylist_paths — and always refuses denylisted paths regardless; paths must be absolute (unless jailed, where a relative path resolves against the primary root) and symlinks are never followed.
• Sandbox-backed background jobs cannot be hard-killed: shell::kill flips the record but the in-VM process runs until its timeout_ms (or sandbox::stop).
• Not for inlining file bytes into an LLM tool result: shell::fs::read/ write move bytes over channels; use the harness worker's harness::fs::read_inline wrapper for inline reads on the web surface.
• No batch or glob form for single-path ops (mv, rm, stat, …); loop in the caller.
• Not a package manager, editor, or migration tool; for SQL use the database worker.

Functions

• shell::exec: run a command in the foreground and return its stdout, stderr, exit code, and timing; blocks until exit or timeout. Sandbox execution is fully valid (target: { kind: "sandbox", sandbox_id }); only the host-only override fields — stdin (string piped to the program's stdin, then EOF), plus cwd/env — are rejected with S210 when supplied on a sandbox target, because the sandbox exec protocol does not forward them.
• shell::exec_bg: spawn a command as a background job and return a job_id immediately. Host-targeted jobs run until they exit or shell::kill terminates them — unbounded by default, capped only when the operator sets a positive max_bg_timeout_ms (default 0 = unbounded), after which a runaway job is killed and its status becomes killed. Sandbox jobs honor timeout_ms. Same optional host-only stdin as shell::exec.
• shell::status: fetch one job's full record: state, exit code, and captured stdout/stderr. A missing id (never existed or aged out) returns an S211 ("no such job") error.
• shell::list: enumerate current jobs as lightweight summaries (no argv, stdout, or stderr).
• shell::kill: terminate a running background job by job_id.
• shell::config-status (operator/automation only — not agent-callable): report the last hot-reload outcome — last_outcome (applied/rejected), last_error, and rejected_reloads (count since boot). A rejected outcome or non-zero count means a stored config was refused and shell is enforcing an older policy than the central store. Takes no arguments.
• shell::fs::ls: list a directory's entries with structured metadata.
• shell::fs::stat: read one path's metadata (size, mode, symlink flag).
• shell::fs::mkdir: create a directory, optionally with missing parents. Returns { created: bool, path: string, already_existed: bool }.
• shell::fs::rm: remove a file or directory, optionally recursive. Returns { removed: bool, path: string, was_present: bool }.

Every shell::fs::* call accepts the same optional target as exec, so host and sandbox share one wire shape; reads and writes move bytes over SDK channels rather than inlining them.

Live change feed (shell::changed)

A custom trigger type backed by a system-level directory watch. Bind it with config: { path: "/some/dir" } to stream every change under that directory — whoever made it: coder::* calls, shell::exec side effects, or an editor outside the engine. Payload: { path, kind, root, dir } with kind ∈ created | modified | deleted, path relative to root, dir true for directories (skip those when opening files). Events coalesce per path in a short window (create + write = created; deletion supersedes), .git internals are filtered, and fan-out is fire-and-forget. Read content on demand via coder::read-file — the event deliberately carries none.

Code files (coder::*)

The shell worker also serves the coder::* code-file surface (formerly a standalone worker) over the same jail (fs.host_roots): coder::info (discover roots/caps first), coder::read-file (windowed + batch reads), coder::search, coder::list-folder, coder::tree, and the batched coder::create-file / coder::update-file / coder::delete-file / coder::move. Prefer these structured ops over editing files through shell::exec. They return C2xx error codes (distinct from shell::*'s S2xx); protected paths are the shared code.non_accessible_globs.