W&B Sandboxes Provider

Read when:

choosing provider: wandb (alias weights-and-biases);
pointing Crabbox at a Weights & Biases Sandbox;
changing internal/providers/wandb.

W&B Sandboxes are managed, isolated Linux containers backed by CoreWeave Sandboxes. The provider talks to the CoreWeave gateway over gRPC (coreweave.sandbox.v1beta2) using the W&B API key as the x-wandb-api-key metadata header, so a caller who has already run wandb login does not need a new provider-specific credential.

This is a delegated-run provider: Crabbox does not provision an SSH box and does not go through the broker coordinator. The CLI starts a sandbox, runs a single command in it via the unary Exec RPC, and stops it again. There is no workspace sync, so crabbox run requires --no-sync.

> Experimental. The upstream API is coreweave.sandbox.v1beta2 and W&B > Sandboxes are in preview. Expect field renames and breaking changes until > upstream cuts a stable v1; the protos are pinned via buf.lock in > internal/providers/wandb/proto/.

#When to use

Use W&B Sandboxes when you already have W&B credentials and want a managed Linux sandbox without provisioning your own runner or creating a new account. Pick a provider with SSH (AWS, Hetzner, Static SSH, Daytona) instead when you need direct shell access or a persistent dev box — this provider is exec-only by design.

W&B Sandboxes are Linux-only. Desktop, browser, code, SSH, Actions hydration, and the broker coordinator are not available.

#Commands

crabbox run    --provider wandb --no-sync -- python eval.py
crabbox run    --provider wandb --no-sync --id swift-crab -- pnpm test
crabbox status --provider wandb --id swift-crab
crabbox stop   --provider wandb swift-crab
crabbox list   --provider wandb
crabbox doctor --provider wandb

Without --id, run acquires a new sandbox, runs the command, and stops the sandbox afterwards. With --id <sandbox-id> it execs into the existing sandbox and leaves it running. warmup is rejected — sandboxes are acquired per run, with no separate provisioning phase.

#Auth

Resolve the W&B API key in this precedence (first match wins):

CRABBOX_WANDB_API_KEY — explicit override, CI-friendly.
wandb.apiKey — config-file value.
WANDB_API_KEY — canonical env var written by wandb login.
~/.netrc — the machine api.wandb.ai (or .com) entry written by

wandb login.

WANDB_ENTITY_NAME is also required; it is sent as the x-entity-id gRPC header. WANDB_PROJECT is optional and, when set, is sent as x-project-name.

export CRABBOX_WANDB_API_KEY=wandb_v1_...
export WANDB_ENTITY_NAME=my-team

The API key is never exposed as a CLI flag; do not pass secrets on the command line.

#Config

provider: wandb
target: linux
wandb:
  defaultImage: ubuntu:24.04
  maxLifetimeSeconds: 1800   # 30 min; W&B reclaims the sandbox at this limit

Defaults applied when unset: defaultImage is ubuntu:24.04 and maxLifetimeSeconds is 1800.

Provider flags (each overrides the matching wandb.* config key):

--wandb-image           # container image used when acquiring a new sandbox
--wandb-max-lifetime    # maximum sandbox lifetime in seconds

Environment overrides:

defaultImage also reads CRABBOX_WANDB_DEFAULT_IMAGE, then

WANDB_DEFAULT_IMAGE.

maxLifetimeSeconds also reads CRABBOX_WANDB_MAX_LIFETIME_SECONDS, then

WANDB_MAX_LIFETIME_SECONDS.

CWSANDBOX_BASE_URL overrides the gateway endpoint (default

api.cwsandbox.com:443); the https:// / http:// scheme is stripped if present.

#Lifecycle

crabbox run:

With --id <sandbox-id>, Exec against the existing sandbox and leave it

running.

Otherwise, Start a sandbox with an idle keep-alive command, poll until it

reaches RUNNING (200 ms backoff, ×1.5, capped at 2 s), Exec the command, then Stop it unless --keep is set.

status renders the sandbox state (for example running; a COMPLETED sandbox is reported as stopped so status --wait treats it as terminal). list paginates sandboxes tagged crabbox. stop issues a graceful stop (15 s timeout). Acquire and exec apply a startup timeout that is the lesser of five minutes and the sandbox lifetime.

#Capabilities

SSH: no — gRPC Exec only.
Crabbox sync: no — --no-sync is required.
Desktop / browser / code: no.
Actions hydration: no.
Coordinator (broker): no — always direct from the CLI.

#Gotchas

maxLifetimeSeconds is the main billing-safety limit. Crabbox defaults to

30 minutes; raise it with --wandb-max-lifetime only when needed. A lease TTL shorter than the configured lifetime narrows it further.

Exec is the unary RPC, so command output is buffered server-side and

returned at completion rather than streamed; there is no interactive PTY.

Environment variables are applied at Start time only. When you target an

existing sandbox with --id, env vars cannot be forwarded onto it (the Exec RPC has no env field), so an --id run with --allow-env is rejected.

--reclaim, --shell, --sync-only, --checksum, --force-sync-large,

and --full-resync are rejected: W&B owns the sandbox lifecycle and there is no Crabbox SSH/rsync target.

--keep retains a newly acquired sandbox after the run; --keep-on-failure

retains it only when the command fails, so you can debug.

gRPC failures map to sysexits-aligned exit codes:

77 (unauthenticated / permission denied), 4 (not found), 124 (deadline exceeded), 69 (unavailable / resource exhausted).

#Live smoke

Run a live smoke when changing W&B lifecycle, exec, status, or auth code. Keep the API key in the environment; never pass it as an argument.

export CRABBOX_WANDB_API_KEY=wandb_v1_...
export WANDB_ENTITY_NAME=my-team
go build -trimpath -o bin/crabbox ./cmd/crabbox

bin/crabbox doctor --provider wandb
bin/crabbox run --provider wandb --no-sync --wandb-max-lifetime 60 -- echo crabbox-wandb-ok

Or the Go smoke test (acquire, exec, stop):

go test -tags smoke -run TestSmokeVersionAndExec -v ./internal/providers/wandb/

#Regenerating the proto stubs

cd internal/providers/wandb/proto
buf dep update          # refresh buf.lock
buf generate            # regenerate ../gen/

Bump the BSR commit pin in buf.lock only via a dedicated, auditable PR.

Related docs:

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