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background-left

A deny rule by default: it refuses an agent finishing while shell commands it ran in the background are still running, and names what to run instead.

What it catches

An agent finishing while shell commands it ran in the background are still running.

Why

A host does not stop a finished subagent's background tasks, and once the subagent has reported nobody is told when one ends or that it is still running: a transcript search left behind by a scout ran for four hours. At a subagent's stop magus reads the subagent's own transcript for the shell commands it ran in the background (run_in_background, a foreground call the host moved to the background, a watcher's command) that no completion notice, stop call or watcher expiry has ended, and refuses the stop naming each by id, start time, age and command. A run under magus job exec --timeout, which check-timeout sends a worker to background and which stops at its deadline, and a commit the host moved to the background while its hooks run, end on their own: their completion notice is how the agent hears the result, so neither holds a stop. At a root session's stop it advises instead, and only of tasks older than 30 minutes: a root wakes on a task's completion notice, so a young task is one it is waiting on, and the person is there to decide. Reads the host's transcript by shape, so a host whose transcript records no background task in that shape is never refused. Set to advise, a subagent's stop is advised too.

Default and override

By default this rule takes the decision deny. A workspace sets it by name, in its root magusfile, to deny, advise or off:

magus\guard.builtins({"background-left": "advise"})

A loosening takes effect once it is committed; a tightening applies at once.

Seeing it

A verdict names its rule in brackets, which is how you got here:

deny [background-left]: ...

A workspace that sets this rule to advise sees advise [background-left]: ... instead.

magus describe rule background-left prints the same entry at a terminal, and magus describe rules lists every rule this workspace enforces.

See also

ReferencePages in this section. human-only: a magus run reaching a human_only target: the person is asked, a leased worker refusedA deny rule by default: it refuses a magus run reaching a human_only target: the person is asked, a leased worker refused, and names what to run instead. lease-vcs: a worker lease mutating version control, or committing outside its own branch and checkoutA deny rule by default: it refuses a worker lease mutating version control, or committing outside its own branch and checkout, and names what to run instead. push-ungated: a push or `gh pr create` at a commit with no green gate; refused for every sessionA deny rule by default: it refuses a push or `gh pr create` at a commit with no green gate; refused for every session, and names what to run instead.
guardrulesbackground-leftdeny
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Glossary

Workspace

The magus root directory that owns a set of projects and shared config; the unit magus operates over. Workspace in full.

Magusfile

The magusfile.buzz that declares a project's targets (as export funs) and binds its spells. Magusfile in full.

Op

A single tool-native command a target composes (long form: operation); the middle of the work hierarchy (Spell to Op to Target). Op in full.

Buzz

The language magusfiles are written in (the .buzz engine). Buzz in full.

CI

An ordinary target you compose yourself with ctx.needs; magus does not hardcode its stages. It is the anchor magus affected ci keys off, and ci strips the rw charm. CI in full.

Agent

A model working through an agent host such as Claude Code, Codex, Cursor or OpenCode. magus treats an agent as one more caller of its CLI, MCP tools and console, held to the same checks as a person. Agent in full.

Session

An agent host's conversation, by the id the host delivers to its hooks. magus never mints one: a record with no session is unattributed, and the OS user it carries says whose account ran it. Session in full.

Job

The unit of delegated work, and one row of the job store: what an orchestrating agent handed out, with its goal, the checkpoint it was cut against, the paths it may write or must not touch, and the one check it runs. A job's holder is either a session, for work an orchestrator handed out, or the daemon, for its own maintenance. The store records; the agent guard is what reads those facts back when grading a write. Job in full.

Run

One target executing under one magus invocation, such as magus run test web or magus affected ci. A run keeps its captured output behind an output reference. Every magus run is a run whether or not any job asked for it; see Job for how the two relate. Run in full.

Conventions

This page uses none of the site's convention markers. The full set is on the conventions page.