Docker Sandboxes release notes

This page lists changes in recent stable releases of Docker Sandboxes. For the full release history, including pre-releases and downloads, see the Docker Sandboxes releases on GitHub.

0.39.0

GitHub release

Highlights

Declarative sandbox environments. Define a complete, reproducible sandbox in a .sbxenv.yaml file, including the agent, workspace, kits, environment variables, secrets, registry credentials, ports, and resource limits. Commit the file with your project so contributors can launch the same environment with sbx env run. This feature is experimental.

What's New

Sandbox environments

• Use sbx env run to provision an environment from .sbxenv.yaml and open an interactive session.
• Use sbx env create, sbx env exec, and sbx env rm to manage the environment lifecycle.
• Combine multiple environment files for shared configuration and local overrides.
• Reference host environment variables in environment files for machine-specific paths and credentials.
• See the sandbox environment files documentation.

CLI

• Add an experimental --usb flag to sbx create behind the DOCKER_SANDBOXES_FEATURE_SANDBOX_USB environment variable to re-attach the specified USB devices. They will be available inside a sandbox via usbfs. Linux x86_64/ARM64 only.
• sbx run --model now selects the Ollama backend via a new --provider ollama flag instead of an ollama/ prefix on the model name.
• Stopped sandboxes can now be cleaned up in bulk with sbx prune, which never removes a running sandbox and can filter on how long each has been stopped.
• sbx run and sbx create now accept -e/--env and --env-file to set environment variables in a sandbox, following docker run precedence rules.

Secrets

• sbx secret set and sbx secret set-custom can now configure dynamic secrets that resolve values from a reference or command, with options to control refreshing, verification, and error output.
• On Linux hosts without an available OS keychain, newly stored secrets are now read and written much faster; secrets already on disk keep their previous cost until they are next written.

Daemon

• Sandboxes now expose their own identity as SANDBOX_NAME and SANDBOX_ID environment variables, matching the name and id shown by sbx ls --json; the older SANDBOX_VM_ID still carries the sandbox name but is deprecated.

Networking

• Claude Code's /remote-control can now be used inside sandboxes by enabling claude.remoteControl setting: sbx settings set claude.remoteControl true.

Bug Fixes

• sandboxd now removes the sandbox container immediately when container startup fails, so an interrupted sbx create/sbx run is less likely to leave the sandbox name unusable.
• Agent kits that declare a persistent volume without a size now get a 512 MB volume instead of a 50 GB one, which significantly reduces sandbox disk usage on the host.
• sbx now reports a clear error for an unrecognized command, subcommand, or sbx help topic instead of printing help and succeeding, and reports a mistyped command without first asking an unauthenticated user to sign in.
• Claude sandboxes now use around 3.9 GB less disk space on the host.
• Claude sandboxes can connect to required Anthropic services when using the locked-down network policy.
• sbx kit inspect now describes kits using kit-spec v2 field names and lists any deprecated fields a kit still relies on, and sbx kit validate now rejects OAuth credentials missing sentinels, a service, or a credential-file body.
• DNS lookups in a sandbox now succeed for any host that network policy allows on any port, including hosts allowed only on a non-standard port such as myhost:2222.
• sbx template load now fails with an error when an image import does not complete, instead of reporting success.
• Correct the sbx create --name help text and CLI reference, which incorrectly listed plus signs as valid sandbox-name characters and omitted the leading-alphanumeric and two-character-minimum rules.
• sbx reset now removes the Docker Sandboxes-managed block from ~/.ssh/config.
• sbx now reports the exit code when a sandbox container dies at startup, and rejects a template image built for a different CPU architecture with a clear message instead of failing after a 30-second wait.
• Signing in to Claude Code with an Anthropic Console API key now succeeds on repeat logins instead of failing with a 401 error.
• Fixed sbx cp failing on Windows when the local path has no directory component (e.g. sbx cp file.txt sandbox:/tmp/).
• sbx daemon restart now starts the daemon again after a stop that reports a failure but leaves no daemon running.

Other

• sbx diagnose now reports free disk space on the volume holding sandbox data, and diagnostics bundles include host disk totals.
• sbx diagnose now detects broken, shadowed, or stale SSH client configuration.
• Add a platform.images.registryMirror setting that redirects Docker Hub-resolving sandbox template and kit images to an organization's registry mirror.
• Filesystem policy denials now include the organization's support contact message, matching network denials.
• sbx now reports when the host cannot provide a hypervisor — including a Windows installation running inside a virtual machine without nested virtualization — instead of a generic "failed to run sandbox container" error, and sbx diagnose now checks host virtualization support.
• Kits can now be signed and verified with cosign-compatible Sigstore signatures via sbx kit sign / sbx kit verify, with optional policy enforcement at load time.
• OAuth kits can declare their credential file with the declarative credentialFile.structure form, rendered to well-formed JSON, instead of a free-form Go template.
• Ubuntu 25.10 packages are no longer published; Ubuntu 25.10 is end-of-life.

0.38.0

GitHub release

Highlights

Kit spec v2. A new schema is available for authoring kits, with a clearer structure for setup, permissions, agent instructions, networking, and credentials. Use schemaVersion: "2" for new kits; existing v1 kits continue to load through the legacy path. See the kit spec reference for migration details.

MCP management is now a first-class feature. Register remote or local MCP servers once with sbx mcp, then reuse them across supported agents and sandboxes through a built-in MCP gateway. OAuth credentials stay on the host, and organizations can govern server registration and tool calls with Cedar policies. See the MCP gateway documentation.

What's new

CLI

• sbx create and sbx run show detailed structured progress during startup, including environment files loaded, resources provisioned, and each kit command's outcome; kit-install progress streams live during sbx create --kit.
• Added sbx daemon restart to stop and restart the sandboxd daemon in the background.
• sbx inspect now displays custom secrets configured for a sandbox.
• DOCKER_SANDBOXES_CLONED_WORKSPACE_SIZE configures the size of the cloned workspace volume.
• sbx setup ssh warns when ssh is missing from PATH, and on Windows when sh (required by Claude Desktop's SSH ProxyCommand) is missing.
• Port publishing failures now identify the affected host port and explain when the OS requires extra daemon privileges.

MCP

• The sbx mcp subcommand is now available for managing MCP servers.
• Includes dynamic MCP tools (mcp-find, mcp-add, mcp-config-set) for attaching registered servers to sandboxes.
• Govern MCP servers and tools for your organization using Cedar policies.

Networking & policy

• --deny-network HOST on sbx run and sbx create records per-sandbox network deny rules at creation time, with layer-aware egress messages.
• sbx policy allow network reports a clear "managed by your organization" error when org governance overrides the local allow, and failed rule removals now explain what went wrong using a single rule identifier.
• Signing in refreshes organization policies in the running daemon immediately instead of waiting for the next polling interval.
• IP-literal destinations denied by a CIDR rule fail fast with a policy message instead of timing out.
• Blocked HTTPS proxy connections appear in sbx policy log even when the client aborts the TLS handshake.

Secrets & credentials

• Service and custom secrets are global by default, with --sandbox for sandbox scope; legacy positional and --global forms are deprecated with warnings.
• Sandbox-scoped GitHub credentials added after creation now work without recreating the sandbox.
• Pressing Ctrl+C while entering a secret cancels the command without saving it.

Agents

• Docker Agent and OpenCode sandboxes can authenticate GitHub Copilot requests with proxy-managed GitHub credentials.
• Codex sandboxes created from the TUI prefer stored OpenAI OAuth credentials over API keys; kit environment variables now reach cloud agents, and git no longer hangs Codex startup prompting for credentials.
• Shared agent skills: directory symlinks under the skills folder are resolved and their contents imported.

Kits & templates

• Kit specs use the new v2 grammar.
• Kits using extends correctly inherit and override the base image or build source of their parent.
• Kit install commands can consume static files from files/home, including binary files.

Packaging

• Homebrew installs from a stapled .dmg artifact rather than a .tar.gz archive, improving Gatekeeper compatibility on macOS.
• Windows: the running sandboxd daemon is stopped during a WinGet/MSI upgrade so client and server end up on the same version.

Security

• Claude Desktop SSH sessions no longer expose Desktop OAuth access tokens inside sandboxes.
• Fixed a destination-escape flaw in sbx cp copy-out (CVE-2026-17106).
• The daemon's loopback egress proxy only serves the daemon's own traffic, preventing other local users on a multi-user host from reaching the configured upstream proxy through it.

Bug fixes

• Fixed a hang where sandboxd stopped answering all endpoints and could not be stopped without SIGKILL after a crash; fatal daemon tracebacks are now included in sbx diagnose --upload bundles.
• Fixed intermittent sandboxd startup failures when a running daemon was slow to answer its health check.
• Fixed sbx daemon stop hanging when an idle SSH session (for example, Claude Desktop) was connected to a sandbox.
• sandboxd automatically repairs a corrupted local image cache by re-pulling the image, and otherwise reports a clear "run sbx daemon reset" error.
• Fixed recreate failures ("base image not found") after daemon restarts when swapping a sandbox's container via sbx kit add; recreates self-heal by recomposing from the sandbox's template.
• Fixed reverse DNS (PTR) lookups from sandboxes returning NXDOMAIN for container-resolved addresses.
• Fixed a goroutine and network-endpoint leak from hijacked HTTP CONNECT tunnels that could eventually stall sandbox creation after many delete/recreate cycles.
• Fixed an intermittent 500 error when deleting a sandbox while its network endpoints were being torn down.
• The daemon restores saved sandboxes' network proxies in parallel on restart, speeding up startup with several sandboxes and fixing a potential crash during first-run policy application.
• Fixed host .git/config corruption when creating a sandbox for repositories using includeIf directives in ~/.gitconfig; the sandbox now writes git identity only to the container's gitconfig.
• sbx skills shows a single usage form and clearer help for importing shared agent skills.
• sbx no longer reports that a stored credential was not injected when the daemon injects it.

Experimental features

Enterprise networking

Settings-driven upstream-proxy configuration with separate sandbox and daemon scopes, integrated NTLM/Kerberos proxy authentication on Windows.

• Configure separate proxy settings for sandbox and daemon traffic using proxy, proxy.sandbox, proxy.daemon, and the matching no_proxy settings. These default to the host operating system's proxy settings. The daemon's own traffic, including image pulls and telemetry, also uses the configured proxy.
• On Windows, sbx can authenticate to upstream proxies that require integrated NTLM or Kerberos/Negotiate authentication. Enable this behavior with the proxy.integratedAuth setting.
• If a TLS-inspecting proxy issues certificates with negative serial numbers, enable compatibility with sbx settings set tls.allowNegativeSerial true, then restart the daemon.

GPU passthrough

Run a sandbox with NVIDIA VFIO GPU passthrough on Linux using sbx run --gpu. Enable this feature with sbx settings set feature.sandbox-gpu true.

Local models

Run Claude Code against a local GGUF model with sbx run --model <name> claude. To use a model from an existing Ollama installation, prefix the model name with ollama/. See Claude Code > Use a local model.

0.37.1

GitHub release

Highlights

This patch release stops SSH sessions from forwarding credential environment variables into sandboxes by default. Variables such as ANTHROPIC_API_KEY, OPENAI_API_KEY, and GH_TOKEN are no longer sent from the client to the sandbox unless explicitly allowed via the ssh.acceptEnv setting.

What's New

Bug Fixes

• SSH sessions no longer forward credential environment variables (ANTHROPIC_API_KEY, OPENAI_API_KEY, GH_TOKEN, ...) from the client into the sandbox by default; use the ssh.acceptEnv setting to opt back in for specific variables

0.37.0

GitHub release

Highlights

SSH access to sandboxes (experimental). Docker Sandboxes can now be used as SSH targets. After enabling SSH access, run sbx setup ssh once, then connect to an existing sandbox by name with ssh my-sandbox.sbx. Use the connection for interactive shells, one-shot commands, and SSH-based remote development.

Shared agent skills. Docker Sandboxes can now import skills from supported host agents into a persistent store shared across sandboxes. Run sbx skills import to import them. New sandboxes mount the store read-write by default; use --no-share-skills to opt out.

What's New

SSH

• sbx setup ssh adds a managed *.sbx entry to your SSH config, making existing sandboxes available at <name>.sbx.
• SSH connections start the local Docker Sandboxes daemon and the target sandbox automatically when needed.
• Connect using OpenSSH-compatible clients and remote-development tools such as VS Code, Cursor, Claude Desktop, and ChatGPT.

Shared skills

• sbx skills import discovers and imports skills from the host and makes them available to sandboxed agents. Use --dry-run to preview imports and --force to replace existing skills.
• Imported skills persist after sandbox deletion and are mounted into new sandboxes for supported agents.
• Pass --no-share-skills to sbx run or sbx create when creating a sandbox to opt out.

CLI

• sbx create and sbx run accept -p/--publish to publish sandbox ports at creation time.

Networking & Policy

• DOCKER_SANDBOXES_PROXY=system routes sandbox egress through the host operating system's proxy configuration (macOS/Windows), including any PAC auto-config URL.
• Governance-policy denials can now display an organization-configured support message (for example, who to contact).

Security & Audit

• Audit now emits execution-outcome records for network egress (per allowed connection) and filesystem mounts (per allowed path) — success, latency, and error class — alongside the policy-attributed decision records.
• sandboxd excludes itself from Windows Error Reporting so daemon crash dumps cannot capture in-memory credentials.

Performance

• sbx secret ls and sandbox startup are faster on Linux hosts without an OS keychain — stored secrets are no longer all decrypted just to list or resolve credentials.

Bug Fixes

• Fixed sandboxd failing to start on Linux hosts without an OS keychain, where the on-disk secret store's key derivation could peg a CPU during startup and the CLI would kill the still-starting daemon.
• Fixed an intermittent "failed to fully delete sandbox" error when removing a running sandbox, caused by a network-teardown race with the engine's endpoint cleanup.

Earlier releases

For older versions, see the Docker Sandboxes releases on GitHub.