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Ephemeral MicroVM-isolated code execution for AI agents. Fresh VM per call, hard-purged after.
About
Ephemeral MicroVM-isolated code execution for AI agents. Fresh VM per call, hard-purged after.
Security Report
Valid MCP server (2 strong, 4 medium validity signals). No known CVEs in dependencies. Imported from the Official MCP Registry. 1 finding(s) downgraded by scanner intelligence.
3 files analyzed · 1 issue found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Required
This plugin requests these system permissions. Most are normal for its category.
What You'll Need
Set these up before or after installing:
Environment variable: SCRATCHRUN_API_KEY
How to Install
Add this to your MCP configuration file:
{
"mcpServers": {
"dev-scratchrun-mcp": {
"env": {
"SCRATCHRUN_API_KEY": "your-scratchrun-api-key-here"
},
"args": [
"-y",
"@scratchrun/mcp-server"
],
"command": "npx"
}
}
}Documentation
View on GitHubFrom the project's GitHub README.
@scratchrun/mcp-server
MCP server for ScratchRun — ephemeral, MicroVM-isolated code execution for AI agents.
Each call runs in a fresh hardware-isolated MicroVM. The VM is hard-purged after execution. No state, no files, nothing persists between calls.
Install
Add to your claude_desktop_config.json:
{
"mcpServers": {
"scratchrun": {
"command": "npx",
"args": ["-y", "@scratchrun/mcp-server"],
"env": {
"SCRATCHRUN_API_KEY": "sr_live_your_key_here"
}
}
}
}
Get an API key at scratchrun.dev.
Tool: scratchrun_exec
Executes code in an ephemeral sandbox and returns stdout, stderr, exit code, and any output files.
Parameters:
| Parameter | Type | Required | Description |
|---|---|---|---|
runtime | python3.12 | python3.11 | node20 | bash | yes | Runtime to use |
code | string | yes | Code to execute |
timeout_ms | integer | no | Timeout in ms (default 10000, max 30000) |
memory_mb | integer | no | Memory limit in MB (default 256, max 512) |
env | object | no | Environment variables — use for secrets, not code strings |
files | object | no | Files to write before execution (path → content) |
return_files | string[] | no | File paths to capture after execution (returned as base64) |
Example — run Python and return a chart:
{
"runtime": "python3.12",
"code": "import matplotlib.pyplot as plt\nimport numpy as np\nx = np.linspace(0, 10, 100)\nplt.plot(x, np.sin(x))\nplt.savefig('/tmp/plot.png')",
"return_files": ["/tmp/plot.png"]
}
Output files are returned as base64. Image files (PNG, JPG, SVG) are returned as MCP image content blocks and render inline in Claude.
Isolation
- Hardware-virtualized MicroVM per execution (own kernel, not a shared-kernel container)
TerminateMicroVMcalled unconditionally after every run — VM destroyed, never reused- RFC 1918 + cloud metadata (
169.254.x.x) always blocked at the network layer - Read-only system filesystem via OverlayFS;
/tmpis RAM-backed and gone with the VM
Latency
~400ms median (warm pool). 2–8s cold start if the pool is empty.
License
MIT
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