What’s New

serverless sf-core@4.39.0

sf-core@4.39.0

4.39.0

Features

  • Sandboxes — AWS Lambda MicroVMs. First-class support for Firecracker-isolated, snapshot-booted virtual machines that you define declaratively and run on demand, with the serverless operational model (no clusters, pay per run). Define a sandbox from a local Dockerfile directory or a prebuilt s3:// zip, and configure memory, environment, lifecycle hooks, tags, and VPC egress. deploy/remove build and tear down the image and supporting resources; IAM build/execution roles are generated for you, and observability — CloudWatch logs, metric filters, alarms, and a dashboard — is enabled by default and fully customizable.

    sandboxes:
  echo:
    artifact: ./app # local directory that contains a Dockerfile

    serverless invoke --sandbox echo          # run it (with --method / --port)
serverless logs --sandbox echo            # fetch logs
serverless dev --sandbox echo             # local dev loop with hot reload

    Local development. serverless dev --sandbox <name> builds and runs the sandbox container on your machine and hot-reloads it as you edit — no deploy needed to iterate. Requests are relayed to the locally running container, so you get the full run/inspect loop against your real sandbox definition before anything ships to AWS.

    See the Sandboxes guide for the full configuration reference, and the serverless/examples sandboxes directory for deploy-ready examples (minimal, complete, and a self-hosted environment for Claude Managed Agent). (#13663)

  • serverless agent commands for AI coding agents. A new command namespace purpose-built for agents (Claude Code, Codex, Cursor) working with a Serverless service. (#13673)

    • serverless agent skills install installs the bundled Agent Skills into the service directory (.claude/skills/, .agents/skills/, or both — auto-detected), teaching agents how to work with the service. Idempotent, auto-refreshing when a newer CLI bundles newer skills, and ejectable per-skill.
    • serverless agent inspect returns the live AWS configuration of a deployed service's resources in a single call — a categorized inventory by default, or expanded raw AWS responses filtered by category (--functions, --api, --iam, --sandboxes, --all, …) or by AWS service. Deterministic, pipe-safe JSON/YAML output, so an agent gets the whole logical-to-physical picture without issuing dozens of aws describe-* calls itself.
    serverless agent skills install
serverless agent inspect --functions --api

    See the Agent Skills guide for how skills are discovered, updated, and ejected, and the agent inspect reference for its full category and AWS-service filtering options.

Maintenance
  • Runtime dependency bumps: @aws-sdk/util-arn-parser (#13680), a batch of 11 patch-level updates (#13677), and other routine bumps (#13666).
  • Development and CI tooling: dev-dependency group updates (#13676), lint-staged 16 → 17 (#13678), and GitHub Actions bumps (#13667); constrained https-proxy-agent to a range that keeps Node 18 support (#13686).
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