maf-sandbox-bicep

Experimental. This package is early-stage (pre-1.0, Development Status :: 4 - Beta) — its API may change or be removed in a future release without notice. Importing it emits a one-time MafSandboxBicepExperimentalWarning; suppress it with warnings.filterwarnings("ignore", category=maf_sandbox_bicep.MafSandboxBicepExperimentalWarning) once you've read the notice.

This package is not affiliated with, endorsed by, or a product of Microsoft — it is a third-party reference implementation of microsoft/agent-framework#7568 for Microsoft Agent Framework.

Sandboxed Bicep validation as a Microsoft Agent Framework tool: bicep_validate writes the files an agent authored into a sandbox, runs bicep build and bicep lint there, and returns the compiler's SARIF diagnostics as structured text — T2 (compiler truth) instead of T0 (the model checking its own work).

app  ->  maf_sandbox  ->  a backend (maf-sandbox-acas, ...)  ->  this workload

This package is a sandbox kind in the sense of maf-sandbox's protocol. It contains no Azure import and no sandbox lifecycle code; it asks a SandboxRouter for a sandbox and gets back write_file and exec, so the same tool runs unchanged against ACA Sandboxes, a local Docker container or an in-process fake. Tests enforce both boundaries: one scans this package's sources for any Azure import, the other for any import outside what its manifest declares.

Quickstart

pip install maf-sandbox-bicep

from maf_sandbox_bicep import make_bicep_tools

tools = make_bicep_tools(router, workspace_store, "devops-engineer", context,
                         image="bicep-sandbox:0.46.1")

Pass router=None — or a router with no backend — and you get [] back: an unconfigured host attaches no tool rather than one that fails when called.

router, workspace_store and context are the host's, and this snippet shows none of them being built. samples/01_acas_bicep is the whole wiring as a runnable program: a one-turn agent that validates a deliberately flawed Bicep file and prints the compiler's diagnostics.

Threat model

Fixed command templates. No agent-authored text is interpolated into a shell command — the only substitution is a filesystem path, and only after that path is validated against the sandbox's own workspace listing (the injection guard: a name that isn't in the listing, or that resolves outside the workspace, is rejected before it reaches a template). Sanitized error surfaces. Failures the sandbox reports are cleaned before the model sees them, so a compiler or shell error cannot smuggle sandbox-internal detail back into the conversation. The egress allowlist. The only hosts Bicep is allowed to reach are the four an AVM module restore reads from — mcr.microsoft.com and *.data.mcr.microsoft.com for the artifacts, aka.ms and live-data.bicep.azure.com for the public module index — stated as a property of the spec (SandboxSpec.egress_allow), not of runtime configuration, because a deployment that could widen Bicep's egress after the fact could undo the containment the tool's design rests on. Nothing else is reachable, ARM above all.

What is Bicep-specific

What is Bicep-specific — the command templates, the accepted extensions, the SARIF parsing, the hosts Bicep is allowed to reach (the four an AVM module restore reads from) — lives here and only here. The spec pins the egress allowlist and work directory as properties of the workload, not of configuration: a deployment that could widen Bicep's egress could undo the containment the tool's design rests on.

Its companion artefacts live outside this package, because a container image and a registry are not Python: a pinned Bicep image on Azure Linux, and the registry and pull identity that serve it. The hard-won behaviours of the pinned CLI — SARIF on stderr for build but stdout for lint, build-params for .bicepparam, config discovery only by walking up from the source file — are documented where they bite, in _tool.py.

Provenance

Split out of maf-sandbox-acas (which keeps the ACAS backend and nothing else) so this workload's dependency set states its portability: maf-sandbox + agent-framework-core, nothing more. Extracted from a production agent application, where it runs against real infrastructure code an agent wrote — which is where every behaviour documented above was learned.

Maintained by SOKOLAI BV.