Strands Box: another open source sandbox

Strands released Strands Box, an open source sandbox for AI agents that combines operating-system isolation with semantic policies written in the Dogwood policy language, currently in preview with support limited to local execution on macOS with Apple silicon. Box is harness-agnostic: users pick the agent program or binary, configure its access in box.toml, and write policies in policy.dw, with the host OS enforcing direct access restrictions and an embedded Dogwood Local Engine evaluating permit and forbid rules that deny operations by default. Strands Shell, Monty for Python, the egress gateway, and the MCP broker share one policy engine and event history, so a file read through one interpreter can cause the gateway to deny a later outbound HTTP request, and the gateway injects configured API credentials or AWS SigV4 signing so the agent never receives the underlying secrets.

Strands Box is an open source sandbox for AI agents. It combines operating-system isolation with semantic policies written in Dogwood https://dogwood-policy.github.io/dogwood/ , so you can control what agents can access and the conditions under which they can act. Box is harness-agnostic. You choose the agent program or binary to run, configure its access in box.toml , and write its policies in policy.dw . The host OS enforces the direct access restrictions in box.toml . Strands Shell, Monty for Python, the egress gateway, and the MCP broker send the operations they handle to the embedded Dogwood Local Engine, which evaluates the rules in policy.dw . Box enforces its allow or deny decisions outside the agent process. Dogwood uses permit and forbid rules. Operations checked by the engine are denied by default: a matching permit must allow the operation, and a matching forbid overrides that permission. Box's interpreters and gateways share an event history, so rules can use earlier actions and elapsed time to decide what is allowed next. For example, a file read through Shell or Python can cause the gateway to deny a later outbound HTTP request. Preview: Box currently supports local execution on macOS with Apple silicon. We welcome feedback through GitHub issues https://github.com/strands-agents/box/issues . Read CONTRIBUTING.md https://github.com/strands-agents/box/blob/main/CONTRIBUTING.md before submitting a change. - File, program, and network restrictions. The agent's sandbox limits its direct access. Box reports the configured grants at startup. - Semantic and temporal policies. Dogwood rules can depend on the requested operation, its arguments, earlier actions, and elapsed time. Operations checked by the policy engine are denied unless a rule permits them. - Policy across code and tools. Strands Shell, Monty for Python, the egress gateway, and the MCP broker use one policy engine and event history. A file read through one interpreter can affect whether a later network request is allowed. - Request and tool-call checks. The egress gateway checks connections and HTTP requests, including their method and path. The MCP integration checks configured tool calls and their arguments. - Credential injection. The gateway authenticates permitted requests with configured API credentials or AWS SigV4 signing. The agent does not receive the underlying secrets. - Decision records. Box records policy decisions in OTLP JSON. By default, records go to <box dir /private/telemetry/records.jsonl . Direct filesystem grants in box.toml are enforced by the OS and do not produce individual Dogwood decisions. To apply a policy to file operations, use the interpreters and keep those files out of the agent's direct grants. See filesystem access https://github.com/strands-agents/box/blob/main/docs/user/security.md and policy https://github.com/strands-agents/box/blob/main/docs/user/policy.md . Box runs the Dogwood Local Engine and its enforcement components in its own process, outside the agent's sandbox. Strands Shell, Monty, the egress gateway, and the MCP broker check operations with the engine before allowing them. They also record events that later policy decisions can use. flowchart LR subgraph sandbox "Agent OS sandbox" agent "Agent application" end net "network requests" :::label py "Python code" :::label sh "shell commands" :::label mc "local MCP calls" :::label subgraph trusted "The box's trusted process outside the agent sandbox " proxy "Egress gateway" monty "Monty for Python" shell "Strands Shell" mcp "MCP broker" policy "Dogwood Local Engine and event history" end agent --- net -- proxy agent --- py -- monty agent --- sh -- shell agent --- mc -- mcp proxy -- |"policy checks"| policy monty -- |"policy checks"| policy shell -- |"policy checks"| policy mcp -- |"policy checks"| policy classDef label fill:none,stroke:none; When the agent uses a program such as git or cargo , or a local MCP server, Box checks the launch against policy and runs the program in its own sandbox. You configure which files each program can read or change. The agent can send requests to Box's interpreters, but external programs and local MCP servers cannot. Box receives their output and exit status, and their network traffic goes through Box's gateway by default. See the security model https://github.com/strands-agents/box/blob/main/docs/user/security.md for details. For each part, where it runs, what it decides, and how one request moves through them, read Box architecture https://github.com/strands-agents/box/blob/main/docs/design/architecture.md . Follow the getting-started guide https://github.com/strands-agents/box/blob/main/docs/user/getting-started.md to run Strands CLI with Box. To follow this guide, you need a Mac with Apple silicon and macOS 15 or later, Node.js 22.21 or later from Homebrew, and access to Claude Opus 5 on Amazon Bedrock in us-west-2 . The download script checks the release checksum and unpacks the binaries into ./box-core . It does not change your PATH or system directories: curl -fsSL https://raw.githubusercontent.com/strands-agents/box/main/download.sh | sh ./box-core/box --version Keep the downloaded binaries together in ./box-core . You can also build from source build-from-source . Then follow the guide to write box.toml and policy.dw , and run the box. Edit box.toml to change the agent's environment and direct access grants. Edit policy.dw to change the rules for operations Box checks through its interpreters and gateways. You can give your coding agent the policy-authoring skill for help with Dogwood syntax and Box's supported actions: https://raw.githubusercontent.com/strands-agents/box/main/.agents/skills/authoring-box-policy/SKILL.md Run the Strands Python SDK example https://github.com/strands-agents/box/blob/main/examples/strands-box/strands-sdk-agent for a small agent whose three tools use Shell. See the example index https://github.com/strands-agents/box/blob/main/examples/README.md for dependencies and run instructions. This is a Cargo workspace. rust-toolchain.toml pins the compiler, and rustup installs it on the first build. Build the box binaries from a clone with rustup https://rustup.rs/ : git clone https://github.com/strands-agents/box.git cd box cargo build --release -p strands-box -p strands-box-containment Run the compiled binary as ./target/release/strands-box . Keep its helper binaries in the same directory. Common tasks run through just https://github.com/casey/just : just build the CLI, the alias image, and the containment trampoline just test workspace tests just check pre-push gate: fmt-check + clippy + test just test-all workspace tests and box example checks cargo test --workspace --all-features runs the full suite. Include --all-features to run the box shell and box credentials suites, which require the test-support feature. | Guide | Contents | |---|---| | docs/user/ https://github.com/strands-agents/box/blob/main/docs/user | How to install Box and run a box. | | docs/design/ https://github.com/strands-agents/box/blob/main/docs/design | Architecture, enforcement boundaries, and design decisions. | See AGENTS.md https://github.com/strands-agents/box/blob/main/AGENTS.md for the repository rules and the current state. Open an issue on this repository. For a suspected security problem, read SECURITY.md https://github.com/strands-agents/box/blob/main/SECURITY.md first. Apache License 2.0.