Sandbox & File Access · Foundry docs

Sandbox & File AccessSandbox and File Access

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Foundry isolates work per project under a sandbox directory. Each project is fully isolated: no cross-project file access, no shared state.Isolation Rules

Each task has a project_id; its working directory is sandbox/<project_id>/.

The supervisor only reads/writes under the sandbox. No access outside unless explicitly configured.

Multiple projects can exist: sandbox/project-a/, sandbox/project-b/.

Each project has its own state key and task queue: no shared state between projects.

Goals are per project; the supervisor completes when all goals in state are completed.

Sandbox Paths

Default root: ./sandbox (relative to supervisor project root)

Project directory: <sandbox-root>/<project-id>/

Task-level override: set working_directory in the task to use <sandbox-root>/<working_directory>

The agent process is spawned with cwd set to the project sandbox directory. sandbox_root is also injected into the state snapshot context so the agent is always aware of its boundaries.BoilerplatesPlace starter code in sandbox/<project-id>/ before enqueueing tasks. The agent will build on existing files. Tasks can say "Extend the existing App.tsx" or "Add an endpoint following routes/users.ts".What to Include in Boilerplates

Project structure (directories, config files)

Initial dependencies (package.json, requirements.txt, etc.)

Starter templates (React components, API routes, etc.)

Parallel Mode and File LockingWhen using parallel execution, each task declares affects_files. The supervisor uses file-level locking so no two tasks edit the same file at once. depends_on enforces task order: tasks are auto-promoted when dependencies are met.