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Get Started Free →majiayu000/hosted-agents
This skill should be used when the user asks to "build background agent", "create hosted coding agent", "set up sandboxed execution", "implement multiplayer agent", or mentions background agents, sandboxed VMs, agent infrastructure, Modal sandboxes, self-spawning agents, or remote coding environments.
Passed 20 of 21 test cases with the skill, and 9 of 21 without it.
and 17 more in the full report
12 fixed9 passed either way1 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 11 test cases the skill fixed. Same model, same prompt, with and without the skill.
We are designing remote sandbox infrastructure for our team's background coding agents to replace our local CLI tools. Can you write a comprehensive technical architecture document outlining how to manage sandbox pre-building and snapshotting, how to handle git configuration and user identity attribution for commits, and how file synchronization should be constrained relative to file reading during early session setup? Please format the output as a structured engineering document with clear sections for Sandbox Lifecycle, Git Integration, and Speed Optimization Strategy.
| Checked | Without skill | With skill |
|---|---|---|
| Specifies pre-building environment images on a fixed 30-minute cadence rather than triggering builds solely on code pushes or lockfile updates | Missed | Passed |
| Configures git user identity using the prompting individual's name and email rather than the application service identity | Missed | Passed |
| Allows immediate parallel file reading before branch synchronization finishes while blocking file writes until synchronization completes | Missed | Passed |
| Includes predictive warm-up that begins spinning up sandboxes as soon as the user starts typing | Missed | Passed |
The instructions your model reads when the skill loads.
Hosted agents run in remote sandboxed environments rather than on local machines. When designed well, they provide unlimited concurrency, consistent execution environments, and multiplayer collaboration. The critical insight is that session speed should be limited only by model provider time-to-first-token, with all infrastructure setup completed before the user starts their session.
Activate this skill when:
Hosted agents address the fundamental limitation of local agent execution: resource contention, environment inconsistency, and single-user constraints. By moving agent execution to remote sandboxed environments, teams gain unlimited concurrency, reproducible environments, and collaborative workflows.
The architecture consists of three layers: sandbox infrastructure for isolated execution, API layer for state management and client coordination, and client interfaces for user interaction across platforms. Each layer has specific design requirements that enable the system to scale.
The Core Challenge Spinning up full development environments quickly is the primary technical challenge. Users expect near-instant session starts, but development environments require cloning repositories, installing dependencies, and running build steps.
Image Registry Pattern Pre-build environment images on a regular cadence (every 30 minutes works well). Each image contains:
When starting a session, spin up a sandbox from the most recent image. The repository is at most 30 minutes out of date, making synchronization with the latest code much faster.
Snapshot and Restore Take filesystem snapshots at key points:
test cases passed, vs 9 / 21 without
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