feat: add node-runner base image for npm-based MCP servers

STDIO servers with packageName (e.g. @leval/mcp-grafana) need a Node.js
container that runs `npx -y <package>`. Previously, packageName was used
as a Docker image reference causing "invalid reference format" errors.

- Add Dockerfile.node-runner: minimal node:20-alpine with npx entrypoint
- Update instance.service.ts: detect npm-based servers and use node-runner
  image with npx command instead of treating packageName as image name
- Fix NanoCPUs: only set when explicitly provided (kernel CFS not available
  on all hosts)
- Add mcp-servers network with explicit name for container isolation
- Configure MCPD_NODE_RUNNER_IMAGE and MCPD_MCP_NETWORK env vars

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

deploy/Dockerfile.node-runner

@@ -0,0 +1,12 @@
+# Base container for npm-based MCP servers (STDIO transport).
+# mcpd uses this image to run `npx -y <packageName>` when a server
+# has packageName but no dockerImage.
+FROM node:20-alpine
+
+WORKDIR /mcp
+
+# Pre-warm npx cache directory
+RUN mkdir -p /root/.npm
+
+# Default entrypoint — overridden by mcpd via container command
+ENTRYPOINT ["npx", "-y"]

deploy/docker-compose.yml

@@ -30,6 +30,8 @@ services:
       MCPD_PORT: "3100"
       MCPD_HOST: "0.0.0.0"
       MCPD_LOG_LEVEL: info
+      MCPD_NODE_RUNNER_IMAGE: mcpctl-node-runner:latest
+      MCPD_MCP_NETWORK: mcp-servers
     depends_on:
       postgres:
         condition: service_healthy
@@ -48,6 +50,16 @@ services:
       retries: 3
       start_period: 10s
 
+  # Base image for npm-based MCP servers (built once, used by mcpd)
+  node-runner:
+    build:
+      context: ..
+      dockerfile: deploy/Dockerfile.node-runner
+    image: mcpctl-node-runner:latest
+    profiles:
+      - build
+    entrypoint: ["echo", "Image built successfully"]
+
   postgres-test:
     image: postgres:16-alpine
     container_name: mcpctl-postgres-test
@@ -71,8 +83,11 @@ networks:
   mcpctl:
     driver: bridge
   mcp-servers:
+    name: mcp-servers
     driver: bridge
-    internal: true
+    # Not internal — MCP servers need outbound access to reach external APIs
+    # (e.g., Grafana, Home Assistant). Isolation is enforced by not binding
+    # host ports on MCP server containers; only mcpd can reach them.
 
 volumes:
   mcpctl-pgdata:

src/mcpd/src/services/docker/container-manager.ts

@@ -5,7 +5,7 @@ import type {
   ContainerInfo,
   ContainerLogs,
 } from '../orchestrator.js';
-import { DEFAULT_MEMORY_LIMIT, DEFAULT_NANO_CPUS } from '../orchestrator.js';
+import { DEFAULT_MEMORY_LIMIT } from '../orchestrator.js';
 
 const MCPCTL_LABEL = 'mcpctl.managed';
 
@@ -54,7 +54,7 @@ export class DockerContainerManager implements McpOrchestrator {
 
   async createContainer(spec: ContainerSpec): Promise<ContainerInfo> {
     const memoryLimit = spec.memoryLimit ?? DEFAULT_MEMORY_LIMIT;
-    const nanoCpus = spec.nanoCpus ?? DEFAULT_NANO_CPUS;
+    const nanoCpus = spec.nanoCpus;
 
     const portBindings: Record<string, Array<{ HostPort: string }>> = {};
     const exposedPorts: Record<string, Record<string, never>> = {};
@@ -83,7 +83,7 @@ export class DockerContainerManager implements McpOrchestrator {
       HostConfig: {
         PortBindings: portBindings,
         Memory: memoryLimit,
-        NanoCpus: nanoCpus,
+        ...(nanoCpus ? { NanoCpus: nanoCpus } : {}),
         NetworkMode: spec.network ?? 'bridge',
       },
     };

src/mcpd/src/services/instance.service.ts

@@ -4,6 +4,12 @@ import type { McpOrchestrator, ContainerSpec, ContainerInfo } from './orchestrat
 import { NotFoundError } from './mcp-server.service.js';
 import { resolveServerEnv } from './env-resolver.js';
 
+/** Default image for npm-based MCP servers (STDIO with packageName, no dockerImage). */
+const DEFAULT_NODE_RUNNER_IMAGE = process.env['MCPD_NODE_RUNNER_IMAGE'] ?? 'mcpctl-node-runner:latest';
+
+/** Network for MCP server containers (matches docker-compose mcp-servers network). */
+const MCP_SERVERS_NETWORK = process.env['MCPD_MCP_NETWORK'] ?? 'mcp-servers';
+
 export class InvalidStateError extends Error {
   readonly statusCode = 409;
   constructor(message: string) {
@@ -139,7 +145,23 @@ export class InstanceService {
       });
     }
 
-    const image = server.dockerImage ?? server.packageName ?? server.name;
+    // Determine image + command based on server config:
+    // 1. Explicit dockerImage → use as-is
+    // 2. packageName (npm) → use node-runner image + npx command
+    // 3. Fallback → server name (legacy)
+    let image: string;
+    let npmCommand: string[] | undefined;
+
+    if (server.dockerImage) {
+      image = server.dockerImage;
+    } else if (server.packageName) {
+      image = DEFAULT_NODE_RUNNER_IMAGE;
+      // Build npx command: entrypoint is ["npx", "-y"], so CMD = [packageName, ...args]
+      const serverCommand = server.command as string[] | null;
+      npmCommand = [server.packageName, ...(serverCommand ?? [])];
+    } else {
+      image = server.name;
+    }
 
     let instance = await this.instanceRepo.create({
       serverId,
@@ -151,6 +173,7 @@ export class InstanceService {
         image,
         name: `mcpctl-${server.name}-${instance.id}`,
         hostPort: null,
+        network: MCP_SERVERS_NETWORK,
         labels: {
           'mcpctl.server-id': serverId,
           'mcpctl.instance-id': instance.id,
@@ -159,9 +182,15 @@ export class InstanceService {
       if (server.transport === 'SSE' || server.transport === 'STREAMABLE_HTTP') {
         spec.containerPort = server.containerPort ?? 3000;
       }
-      const command = server.command as string[] | null;
-      if (command) {
-        spec.command = command;
+      // npm-based servers: command = [packageName, ...args] (entrypoint handles npx -y)
+      // Docker-image servers: use explicit command if provided
+      if (npmCommand) {
+        spec.command = npmCommand;
+      } else {
+        const command = server.command as string[] | null;
+        if (command) {
+          spec.command = command;
+        }
       }
 
       // Resolve env vars from inline values and secret refs