fabric-exec

fabric_exec — Python reference

Write a Python async function body in code: top-level await and return, no enclosing function or event-loop runner. Every invocation starts fresh. Only the returned JSON-compatible value reaches the model; print() goes to activity logs. Use True, False, None, native dicts/lists, and dict access for results. Never switch interpreters through shell commands to perform Fabric orchestration.

Runtime boundary

The default Python backend is Monty, a sandboxed Python subset. Arbitrary imports, third-party packages, native filesystem/network/environment access, and some Python syntax are unavailable. Use host tools for effects. import asyncio and asyncio.gather are supported. Missing native dependencies fail without fallback. Explicit CPython is trusted native code outside Schema enforce; enforce requires OS isolation and fails closed when unavailable. Neither backend exposes guest-local workflow helpers, memory visitor callbacks, or handoff predicates.

Core tools

Full code mode (also Schema enforce) exposes pi and captured extensions; orchestration-only mode leaves these on Pi's direct tool path instead.

import asyncio
manifest, matches = await asyncio.gather(
    pi.read("package.json"),
    pi.grep(pattern="TODO", path="src", limit=20),
)
return {"manifest": manifest, "matches": matches}

Search before bounded reads: await pi.find(pattern="*.py", path="src", limit=20), then await pi.read(path="src/main.py", offset=1, limit=80). Read continuation notices; unbounded reads cap at 2000 lines or 50KB. read, grep, find, and ls return payloads. Shell, edit, and write return dictionaries:

r = await pi.bash(command="git status --short", settle=True)
return {"ok": r["ok"], "output": r["output"], "exitCode": r.get("exitCode")}

Shell nonzero exits raise unless settle=True; timeout, cancellation, security and approval failures still raise. Shell timeout is seconds. No stdin option: write content to a file first, then use its path. Do not interpolate untrusted content into shell commands.