Blaxel sandbox backend¶

Bernstein's blaxel sandbox backend talks to the Blaxel control plane (https://blaxel.ai) over its public REST API and conforms to the SandboxBackend protocol exposed by bernstein.core.sandbox.

Module¶

src/bernstein/core/sandbox/backends/blaxel.py - class BlaxelSandboxBackend, registered under the name blaxel in bernstein.core.sandbox.registry.

Environment variables¶

Variable	Required	Purpose
`BLAXEL_API_KEY`	yes	Bearer token issued in Workspace Settings -> API Keys.
`BLAXEL_WORKSPACE`	yes	Workspace slug that owns the sandboxes.
`BLAXEL_API_URL`	no	Override of the API root. Defaults to `https://api.blaxel.ai/v0`.

When any required variable is missing the backend raises SandboxCredentialError from bernstein.core.sandbox.backends._http_helpers naming the missing variable.

Capabilities¶

FILE_RW, EXEC, NETWORK, PERSISTENT_VOLUMES.

SNAPSHOT is not advertised because the public Blaxel REST API does not expose a snapshot/restore primitive at time of writing. backend.snapshot() and backend.resume() raise NotImplementedError with a pointer to the vendor changelog.

Selecting the backend¶

sandbox:
  backend: blaxel
  options:
    runtime: python:3.13
    region: us-east-1

Honest limitations¶

No exec streaming. The Blaxel REST endpoint returns the final combined stdout/stderr of the command after the process exits, rather than streaming over WebSockets. Long-running interactive workloads that need tail-style log streaming should use the worktree or docker backends.
Snapshots not supported. Provider does not expose snapshot/resume; persistent state lives in the workspace volume attached to the sandbox.

Integration tests¶

Live integration tests are gated by CI_BLAXEL_TEST=1 plus the credentials above. Without them the test in tests/integration/sandbox/test_blaxel_backend.py skips cleanly.