SCH: An affordable sandbox for Coding Agents in your AWS account
2 days ago
- SCH is a serverless coding harness built on AWS AgentCore, enabling isolated, asynchronous coding agent tasks.
- It solves the problems of keeping machines running, avoiding permission gate stalls (YOLO mode), and providing isolation per session.
- Key concepts: state (git history, checkpoints), harness (tools, hooks, loops), and runtime (disposable microVM).
- Features include session handoff from local to cloud, detached tasks that survive laptop shutdown, Telegram supervision, and per-branch workspaces.
- Three use cases: handoff (brainstorm locally, continue remotely), AWS workbench (isolated with IAM roles), and backlog tasks (parallel branches with different agents).
- Cost analysis over 12 days showed ~$3.45 total, with memory being ~78% of cost; idle timeout is the main cost lever.
- Compared to EC2, AgentCore is cheaper for intermittent use (break-even around 680-700 session-hours/month).
- Limitations include proof-of-concept status, AWS lock-in, harness differences (Pi lacks some features), and single maintainer.
- Next steps: slimmer image to reduce memory cost, cost guardrails, VPC network mode, and identity passthrough.
- The project source code is available at c-daniele/sch, and the author recommends starting with 'sch run aws-lab'.