Emisar MCP Server

emisar

Approved infrastructure actions for AI tools, enforced on-host.

emisar is a control plane, outbound-only runner, and MCP bridge for letting AI tools request a finite, declared set of operational actions without receiving raw shell or SSH access.

Status: public beta. This monorepo contains the complete runner, Phoenix control plane, public website, and MCP stdio bridge. The hosted control plane is the current supported product boundary; self-hosted and air-gapped deployments are not generally available.

What it does

• Loads versioned, content-addressed action packs on each runner.
• Dials out to the control plane over a TLS websocket — no inbound listener.
• Blocks dispatch when a runner advertises new, custom, or changed pack contents until an admin trusts the hash.
• Connects remote MCP clients through OAuth and local clients through the emisar-mcp stdio bridge.
• Applies per-user runner scopes, risk-tier policy, action overrides, human approvals, and revocable standing grants.
• For each run_action message from cloud:
  1. Re-validates arguments against the action's declared schema.
  2. Recomputes and verifies the trusted pack hash.
  3. Clamps cloud-supplied opts to the action's *_min/*_max bounds.
  4. Executes via os/exec with argv arrays, never shell strings.
  5. Streams line-buffered, redacted output back over the websocket.
  6. Writes one hash-chained JSONL event per attempt to the local security log.
• Mirrors run state into a searchable audit log with a read-only SIEM export.

What it deliberately is NOT

• Not a sandbox or process isolator.
• Not an arbitrary remote shell or generic execute(command) tool.
• Not a replacement for OS-level least privilege, process isolation, or customer change-management controls.
• Not fully open source (yet). The on-host components — runner/, mcp/, packs/ — are Apache-2.0; the control plane is source-available under the Business Source License 1.1 and converts to Apache-2.0 on its Change Date.

See docs/security-model.md.

Install (production)

Create a runner from the portal to receive a scoped bootstrap key and generated install command. The underlying supervised installer for Linux (systemd) and macOS (launchd) is:

curl -sSL https://raw.githubusercontent.com/andrewdryga/emisar/main/install.sh | sudo bash

This downloads the latest tagged release, verifies SHA256, creates a dedicated service user (Linux), installs /usr/local/bin/emisar, drops a config skeleton at /etc/emisar/, and installs the systemd unit or launchd plist with Restart=on-failure supervision and StartLimitBurst caps.

After install, edit /etc/emisar/config.yaml and /etc/emisar/runner.env if the portal-generated command did not populate them, then start the service. See docs/install.md for upgrade, uninstall, air-gapped install, and full operational commands.

Quick start (dev / local)

Commands run from the repo root. The runner is its own Go module under runner/ (see Repository layout below); building it puts the binary at bin/emisar:

# 1. Build the runner + MCP bridge
(cd runner && go build -o ../bin/emisar .)
(cd mcp && go build -o ../bin/emisar-mcp .)

# 2. Validate the bundled example packs
./bin/emisar pack validate ./packs/linux-core
./bin/emisar pack validate ./packs/cassandra
./bin/emisar pack validate ./packs/showcase

# 3. See what the runner would advertise to cloud
./bin/emisar --config ./runner/examples/config.yaml state | jq

# 4. Run an action locally for debugging (bypasses cloud)
./bin/emisar --config ./runner/examples/config.yaml \
    action run linux.uptime --reason "smoke test"

# 5. Stream a long-running action's output
./bin/emisar --config ./runner/examples/config.yaml \
    action run linux.journalctl --arg unit=docker --stream

# 6. Inspect the JSONL log
./bin/emisar --config ./runner/examples/config.yaml events tail --lines 20

To run in daemon mode (waiting for cloud commands):

EMISAR_AUTH_KEY=emkey-auth-... \
  ./bin/emisar --config ./runner/examples/config.yaml connect

Documentation

Repository layout

Monorepo with one folder per deployable component, in a language-rooted layout. Each Go folder is its own module; the Elixir control plane is an umbrella project. go.work ties the two Go modules together for editor + CLI convenience.

portal/                          Elixir/Phoenix control plane (umbrella)
  apps/emisar/                     domain contexts: accounts, runs, policies, audit, billing
  apps/emisar_web/                 LiveView dashboard + marketing site + MCP HTTP API
runner/                          Go module — on-host runner binary
  main.go, connect.go, …           CLI (cobra)
  internal/cloud                   wire protocol + outbound websocket client
  internal/engine                  action runtime (validate → clamp → execute → redact → journal)
  internal/packs                   pack loader + in-memory registry
  internal/executor                exec/script process runner (line-buffered streaming)
  internal/validation              arg schema enforcement
  internal/expressions             tiny argv-substitution template engine
  internal/redact                  output redaction
  internal/audit                   hash-chained JSONL event log
  internal/config                  config loader
  pkg/actionspec                   action spec types (YAML schema)
  pkg/packspec                     pack manifest types
  examples/config.yaml             example runner config
mcp/                             Go module — stdio MCP bridge for Claude Code / Cursor / etc.
packs/                           action pack catalog (YAML) — linux-core, cassandra, docker, + 70 more; consumed by the runner + portal
docs/                            architecture, security, signed-dispatch, action-packs, cloud-boundary, wire-protocol
docker-compose.yml               Full local stack: Postgres, portal, seeder, and runners
install.sh                       supervised install (systemd / launchd) — run against tarball

License

This repository is dual-licensed:

• runner/, mcp/, and packs/ — the code that runs on your hosts (the runner, the stdio MCP bridge) and the action-pack catalog — are open source under the Apache License 2.0. Inspect it, build it, package it, and keep operating it independently of us.
• Everything else, including the portal/ control plane, is source-available under the Business Source License 1.1: free for any non-production use, free production use under the Additional Use Grant (organizations under USD 1M annual revenue, and anything needed to run the Apache-licensed components or the hosted service), and each version converts to the Apache License 2.0 on its Change Date — so the entire codebase is guaranteed to become open source over time.

See:

• LICENSE.md
• runner/LICENSE · mcp/LICENSE · packs/LICENSE
• CONTRIBUTING.md
• CLA.md
• NOTICE.md
• SECURITY.md

For commercial licensing beyond the Additional Use Grant, contact licensing@emisar.dev.