OS-enforced sandbox backend for LangChain Deep Agents using nono.

Kernel-level sandboxing, network filtering, policy-based access control, credential injection, and filesystem snapshots — all native Python, no containers required.

Installation

pip install langchain-nono

Usage

import uuid
from pathlib import Path

from langchain_anthropic import ChatAnthropic
from deepagents import create_deep_agent
from langchain_nono import NonoSandbox

thread_id = str(uuid.uuid4())
working_dir = Path("/tmp/agent-sandboxes") / thread_id
working_dir.mkdir(parents=True, exist_ok=True)

sandbox = NonoSandbox(
    working_dir=str(working_dir),
    virtual_workspace_root=True,
)

agent = create_deep_agent(
    backend=sandbox,
    model=ChatAnthropic(model_name="claude-sonnet-4-6"),
    system_prompt="You are a coding assistant with sandbox access.",
)

result = agent.invoke(
    {
        "messages": [
            {
                "role": "user",
                "content": "Create a hello world Python script and run it",
            }
        ]
    },
    config={"configurable": {"thread_id": thread_id}},
)
print(result["messages"][-1].content)

virtual_workspace_root=True lets Deep Agents use absolute tool paths such as /hello.py while langchain-nono stores the file under the concrete per-thread workspace, for example /tmp/agent-sandboxes/<thread-id>/hello.py.

Configuration

sandbox = NonoSandbox(
    working_dir="/tmp/agent-workspace",     # Required: read-write access
    virtual_workspace_root=True,            # Map /file.py to working_dir/file.py for Deep Agents
    allow_read=["/data/models"],            # Additional read-only paths
    allow_readwrite=["/tmp/scratch"],        # Additional read-write paths
    policy_json=json.dumps({                # Optional: nono policy JSON
        "groups": {
            "project_rw": {
                "description": "RW access to a project directory",
                "allow": {"readwrite": ["/tmp/agent-workspace"]}
            }
        }
    }),
    policy_groups=["project_rw"],           # Groups to resolve from policy_json
    proxy_config=ProxyConfig(               # Optional: host filtering + credential injection
        allowed_hosts=["api.openai.com"],
    ),
    snapshot_session_dir="/tmp/nono-session",  # Optional: enable snapshots + rollback
    block_network=True,                     # Block outbound network (default)
    timeout=300,                            # Default command timeout in seconds
)

Network Filtering

Pass proxy_config=ProxyConfig(...) to start the nono proxy when the sandbox is created. execute() automatically receives the proxy environment variables, so host filtering and credential injection apply to sandboxed child processes without extra wiring in the caller.

import shlex

from langchain_nono import NonoSandbox, ProxyConfig

sandbox = NonoSandbox(
    working_dir="/tmp/agent-workspace",
    proxy_config=ProxyConfig(allowed_hosts=["example.com"]),
    block_network=True,
)

request_script = """
import urllib.request

with urllib.request.urlopen("https://example.com", timeout=30) as response:
    print(response.status)
"""
result = sandbox.execute(f"python3 -c {shlex.quote(request_script)}")
print(result.exit_code)

events = sandbox.drain_network_audit_events()
sandbox.shutdown_proxy()

Or resolve proxy config from a policy file:

proxy_config = NonoSandbox.resolve_proxy_from_policy(
    policy_json, ["proxy_web_demo"]
)

Credential Injection

The proxy can inject real API credentials on outbound requests, so sandboxed code never sees real keys. Real credentials can be loaded from host-side sources such as env://OPENAI_API_KEY. When env_var is configured on a route, the sandboxed child receives a route-scoped phantom token in that variable; the proxy swaps that phantom token for the real credential before forwarding upstream.

When proxy mode is enabled, langchain-nono uses nono-py's proxy-only network mode so sandboxed code can connect only to the local proxy port; all direct outbound network access remains blocked.

import shlex

from langchain_nono import InjectMode, NonoSandbox, ProxyConfig, RouteConfig


sandbox = NonoSandbox(
    working_dir="/tmp/agent-workspace",
    proxy_config=ProxyConfig(
        allowed_hosts=["api.openai.com"],
        routes=[
            RouteConfig(
                prefix="/openai",
                upstream="https://api.openai.com",
                credential_key="env://OPENAI_API_KEY",  # Host env lookup
                inject_mode=InjectMode.HEADER,
                inject_header="Authorization",
                credential_format="Bearer {}",
                env_var="OPENAI_API_KEY",          # Phantom token env var
            )
        ],
    ),
    block_network=True,
)

try:
    # The child sees OPENAI_API_KEY=<phantom> and OPENAI_BASE_URL=http://127.0.0.1:<port>/openai.
    # The proxy swaps the phantom token for the real key on outbound requests.
    request_script = """
import os
import urllib.request

request = urllib.request.Request(
    os.environ["OPENAI_BASE_URL"] + "/v1/models",
    headers={"Authorization": "Bearer " + os.environ["OPENAI_API_KEY"]},
)
with urllib.request.urlopen(request, timeout=30) as response:
    print(response.read().decode())
"""
    result = sandbox.execute(f"python3 -c {shlex.quote(request_script)}")
    print(result.output)
finally:
    sandbox.shutdown_proxy()

Injection modes: HEADER, QUERY_PARAM, BASIC_AUTH, URL_PATH.

Snapshots

Pass snapshot_session_dir=... to enable content-addressable snapshots and rollback for the sandbox workspace.

from pathlib import Path
from tempfile import TemporaryDirectory

from langchain_nono import ExclusionConfig, NonoSandbox


def print_changes(title, changes):
    print(title)
    for change in changes:
        print(f"  - {change.change_type}: {Path(change.path).name}")


with (
    TemporaryDirectory(prefix="agent-workspace-") as workspace,
    TemporaryDirectory(prefix="nono-session-") as session_dir,
):
    sandbox = NonoSandbox(
        working_dir=workspace,
        snapshot_session_dir=session_dir,
        snapshot_exclusion=ExclusionConfig(exclude_patterns=["node_modules"]),
    )

    sandbox.execute("printf 'version 1\n' > app.txt")
    baseline = sandbox.create_snapshot_baseline()
    print("Baseline snapshot")
    print(f"  app.txt contains: {sandbox.execute('cat app.txt').output.strip()!r}")

    sandbox.execute("printf 'version 2\n' > app.txt")
    sandbox.execute("printf 'generated\n' > output.txt")
    manifest, changes = sandbox.create_snapshot_incremental()

    print("\nAgent changed the workspace")
    print(f"  app.txt now contains: {sandbox.execute('cat app.txt').output.strip()!r}")
    print_changes("Snapshot detected:", changes)
    print(f"  Merkle root changed: {baseline.merkle_root != manifest.merkle_root}")

    diff = sandbox.compute_restore_diff(0)
    print_changes("\nDry-run restore preview:", diff)

    restored = sandbox.restore_snapshot(0)
    print(f"\nRestored baseline by applying {len(restored)} change(s)")
    print(f"  app.txt contains: {sandbox.execute('cat app.txt').output.strip()!r}")
    print(
        "  output.txt:",
        sandbox.execute("test -e output.txt && echo exists || echo removed").output.strip(),
    )

Session Metadata

Save audit trails with Merkle roots and network events:

meta = SessionMetadata(
    session_id="my-session",
    command=["bash", "-c", "echo hello"],
    tracked_paths=["/tmp/agent-workspace"],
)
meta.add_merkle_root(baseline.merkle_root)
sandbox.save_session_metadata(meta)

# Later, load from disk:
loaded = NonoSandbox.load_session_metadata("/tmp/nono-session")

Examples

Inline policy for an agent that can write in its workspace, read a reference folder, and is denied access to a sibling secrets folder because that path is never granted:

python examples/01_policy_inline.py

Policy loaded from a JSON file with the same workspace/reference split, plus an explicit deny.access rule for the secrets folder on macOS:

python examples/02_policy_from_file.py

Policy-aware upload_files() and download_files() with user-facing error messages instead of raw backend error codes:

python examples/03_policy_file_transfer.py

Proxy basics -- starting a proxy, running commands, draining audit events:

python examples/04_proxy_basics.py

API key protection via proxy credential injection without exposing the API key:

python examples/05_credential_injection.py

Policy-based proxy configuration resolved from JSON groups:

python examples/06_policy_proxy.py

Filesystem snapshots with dry-run diff and rollback:

python examples/07_snapshot_rollback.py

Full supervisor flow combining proxy, snapshots, and session metadata:

python examples/08_proxy_with_snapshots.py

The matching policy document is:

examples/policy_example.json

How it works

Each execute() call:

1. Forks the current process
2. Applies OS-level sandbox restrictions in the child (Landlock or Seatbelt)
3. Exec's the command
4. Captures stdout/stderr and waits for exit

The parent process remains unsandboxed and can call execute() repeatedly. Sandbox restrictions are enforced by the kernel and cannot be bypassed from userspace.

Platform support

Platform	Mechanism	Minimum version
Linux	Landlock LSM	Kernel 5.13+
macOS	Seatbelt	macOS 10.15+