Ephemora Cell MCP — Claude Code WASM MCP server
Runs agent-generated code in an isolated WASM environment with resource limits. Use it to separate execution from the project and produce signed evidence of a run.
claude mcp add ephemora-cell-mcp -- uvx ephemora-cellWhat Ephemora Cell MCP — WASM Sandbox does
Ephemora Cell creates a fresh environment for each run and removes it afterward. The MCP server passes code to a WASM module and sets limits for fuel, memory, time, and I/O. Network and process access are denied by default; filesystem and network capabilities must be granted explicitly.
Output size is bounded, and a run can produce signed evidence. Execution state does not carry over to the next run. Python 3.10+ is required, and the install command launches the server with uvx. One security caveat matters: independent security evaluation is still pending, and the newest isolation controls are on main, not in the published release.
What it helps with
- isolate agent-generated code during execution
- cap WASM memory and runtime
- block network access by default
- produce signed evidence for a run
Example prompts for the agent
- Run this untrusted code in the WASM sandbox with resource limits.
- Execute the module without network access and return its result.
- Tell me what signed evidence this run can produce.
How to install Ephemora Cell MCP — WASM Sandbox
Platform CLI
claude mcp add ephemora-cell-mcp -- uvx ephemora-celluvx runs the command named after the package; if the README names another one, use uvx --from ephemora-cell <command>
Platform CLI
codex mcp add ephemora-cell-mcp-wasm-sandbox -- uvx ephemora-celluvx runs the command named after the package; if the README names another one, use uvx --from ephemora-cell <command>
Config file
{
"mcpServers": {
"ephemora-cell-mcp-wasm-sandbox": {
"command": "uvx",
"args": [
"ephemora-cell"
]
}
}
}uvx runs the command named after the package; if the README names another one, use uvx --from ephemora-cell <command>
Config file
{
"servers": {
"ephemora-cell-mcp-wasm-sandbox": {
"type": "stdio",
"command": "uvx",
"args": [
"ephemora-cell"
]
}
}
}uvx runs the command named after the package; if the README names another one, use uvx --from ephemora-cell <command>
Platform CLI
gemini mcp add ephemora-cell-mcp-wasm-sandbox uvx ephemora-celluvx runs the command named after the package; if the README names another one, use uvx --from ephemora-cell <command>
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Ephemora Cell MCP — WASM Sandbox
How do I install Ephemora Cell MCP in Claude Code?
Run claude mcp add ephemora-cell-mcp -- uvx ephemora-cell to add the MCP server to Claude Code.
What does Ephemora Cell MCP do?
It executes code in a WASM environment with configurable limits, then discards the execution state. A run can also produce signed evidence.
What limits can I apply to an execution?
Limits can cover fuel, memory, time, I/O, and output size. Network and process access are denied by default.
