| name | hosted-agents |
| description | Build background agents in sandboxed environments. Use for hosted coding agents, sandboxed VMs, Modal sandboxes, and remote coding environments. |
| type | skill |
| created | 2026-02-27T00:00:00.000Z |
| domain | productivity |
| category | developer-experience |
| risk | unknown |
| source | community |
| tags | ["skill","productivity","developer-experience","hosted","agents"] |
Hosted Agent Infrastructure
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.
When to Use
Activate this skill when:
- Building background coding agents that run independently of user devices
- Designing sandboxed execution environments for agent workloads
- Implementing multiplayer agent sessions with shared state
- Creating multi-client agent interfaces (Slack, Web, Chrome extensions)
- Scaling agent infrastructure beyond local machine constraints
- Building systems where agents spawn sub-agents for parallel work
Core Concepts
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.
Detailed Topics
Sandbox Infrastructure
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:
- Cloned repository at a known commit
- All runtime dependencies installed
- Initial setup and build commands completed
- Cached files from running app and test suite once
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:
- After initial image build (base snapshot)
- When agent finishes making changes (session snapshot)
- Before sandbox exit for potential follow-up
This enables instant restoration for follow-up prompts without re-running setup.
Since git operations are not tied to a specific user during image builds:
