tai42-sandbox-local

A direct/host sandbox provider for the TAI ecosystem. It implements the tai42_contract.sandbox.Sandbox surface over plain host subprocesses and the host filesystem: it runs a session's code directly on the host, with no container and no isolation. Exactly one sandbox provider is active per deployment, and the operator picks direct/host execution by installing this provider instead of a container provider — the consumers are provider-agnostic and acquire whichever is installed.

The TAI ecosystem

TAI is an open-source runtime for MCP tools, agents, and workflows. A Sandbox is "where a session's code runs" — a pluggable provider the runtime acquires through one seam. This package is one such provider (direct/host execution); any package can back the same contract, so this repo is this provider's own full doc home, and the documentation site covers the platform-level story:

• Sandbox concept: https://tai42.ai/concepts/sandboxes
• Deployment / operate: https://tai42.ai/operate

Its only tai-* dependencies are tai42-contract (the Sandbox ABC, the session / stream models, SandboxPolicy, the error family, PluginItemKind.SANDBOX, and the tai42_app.sandboxes facet) and tai42-kit (ManagedSandbox / ManagedSandboxSession — the shared ledger, TTL/reap, orphan recovery, and the session-create policy chokepoint — plus SandboxDispatchSettings and the conformance suite). It pulls in no third-party runtime dependency: it drives the host with the standard library only.

Security model

This provider gives no isolation: isolation="none" means arbitrary session code runs on the host with the host's filesystem, network, and secrets in reach. It is for a trusted, single-tenant box, not untrusted flows. It accepts only what it can honestly enforce and rejects the rest loudly:

• isolation="none" accepted; container / vm rejected. The operator isolation floor defaults to container, so a deployment installing this provider must set TAI_MCP_SANDBOX_ISOLATION=none or every session create rejects.
• network="egress" accepted; none / internal rejected.
• a cpu / memory_mb cap rejected.
• image is inert — the host is the execution environment; the operator installs the runtime on the host.

For enforced isolation or network lockdown, install a container provider instead.

Configuration

The SANDBOX_LOCAL_ env group: SANDBOX_LOCAL_ROOT (the host workspace root) and SANDBOX_LOCAL_BASE_PATH (the clean-env PATH), plus the shared dispatch knobs (SANDBOX_LOCAL_DEFAULT_TTL_SECONDS, SANDBOX_LOCAL_REAP_INTERVAL_SECONDS, SANDBOX_LOCAL_EXEC_DEFAULT_TIMEOUT_SECONDS). See docs/index.mdx for the full table and the durability model.

The current release line tracks the 7.x contract (tai42-contract>=7,<8).