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MGS2002: path write denied by sandbox

A spell tried to write to a file outside the workspace and outside the configured allowlist.

[MGS2002] fs write denied: /home/user/.bashrc

Why

The sandbox denies writes outside <workspace> and /tmp by default. This blocks the supply-chain attack pattern of modifying shell startup files, sudoers, or cron tables for persistence.

Resolution

  1. If the write target is a legitimate cache (e.g. a Rust spell writing to ~/.cargo/registry/cache): add it to magus.yaml:

    sandbox:
  allow:
    - path: ~/.cargo
      mode: rw

  2. If the spell should be writing inside the workspace but is using an absolute path: the spell has a bug. File an issue with the spell author; in the meantime grant the path explicitly or disable sandbox mode.

  3. If this is a malicious spell: do not grant the path. Uninstall.

sandbox diagnosticsLanding page for the sandbox that confines magus spells to the workspace, plus its MGS2xxx diagnostics for denied reads, writes, execs, and env leaks. MGS2001: path read deniedFires when a spell tries to read a file outside the workspace and outside the configured sandbox allowlist, typically a credential store. Sandbox modelThe threat model and allowlist semantics that magus enforces around spell execution, and how the MGS2xxx diagnostics map onto that model. magus stdlibReference for every magus stdlib module - fs, os, http, json, yaml, crypto, and the rest of the magusfile API surface.
MGS2002sandboxsecuritypermissionswriteallowlistpersistence
Last updated (b022d75e)
Glossary

Workspace

The magus root directory that owns a set of projects and shared config; the unit magus operates over. See workspace.

Target

A named operation (build, test, ...) you invoke with magus run <target>; it may compose a spell's tool-native operations and depend on other targets. See targets.

Spell

A language/runtime adapter (e.g. go, md) that maps generic targets onto a toolchain's real commands. See spells.

Cache

The content-addressed store magus consults before running a target, so unchanged work is skipped. See cache.

Sandbox

The restricted filesystem and environment a target runs in, so builds stay reproducible and side-effect-free. See sandbox.

CI

An ordinary magusfile-defined target you compose yourself with magus\needs - magus does not hardcode its stages. Magus.RunCI treats it specially only in that it strips the rw charm, it is the anchor magus affected ci keys off, and a selected scope with no project declaring it is a load error rather than a silent no-op. See targets.

Conventions

Placeholders

Angle brackets mark a value you replace with your own - never type the brackets:

magus run <target>
magus completion <shell>    # e.g. bash, zsh, fish

<target>, <path>, <shell>, <name> and the like are stand-ins, not literal text.