feat(skill-mcp): add MCP client manager with lazy loading and session cleanup

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/features/skill-mcp-manager/index.ts

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+export * from "./types"
+export { SkillMcpManager } from "./manager"

src/features/skill-mcp-manager/manager.test.ts

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+import { describe, it, expect, beforeEach, afterEach, mock, spyOn } from "bun:test"
+import { SkillMcpManager } from "./manager"
+import type { SkillMcpClientInfo, SkillMcpServerContext } from "./types"
+import type { ClaudeCodeMcpServer } from "../claude-code-mcp-loader/types"
+
+describe("SkillMcpManager", () => {
+  let manager: SkillMcpManager
+
+  beforeEach(() => {
+    manager = new SkillMcpManager()
+  })
+
+  afterEach(async () => {
+    await manager.disconnectAll()
+  })
+
+  describe("getOrCreateClient", () => {
+    it("throws error when command is missing", async () => {
+      // #given
+      const info: SkillMcpClientInfo = {
+        serverName: "test-server",
+        skillName: "test-skill",
+        sessionID: "session-1",
+      }
+      const config: ClaudeCodeMcpServer = {}
+
+      // #when / #then
+      await expect(manager.getOrCreateClient(info, config)).rejects.toThrow(
+        /missing required 'command' field/
+      )
+    })
+
+    it("includes helpful error message with example when command is missing", async () => {
+      // #given
+      const info: SkillMcpClientInfo = {
+        serverName: "my-mcp",
+        skillName: "data-skill",
+        sessionID: "session-1",
+      }
+      const config: ClaudeCodeMcpServer = {}
+
+      // #when / #then
+      await expect(manager.getOrCreateClient(info, config)).rejects.toThrow(
+        /my-mcp[\s\S]*data-skill[\s\S]*Example/
+      )
+    })
+  })
+
+  describe("disconnectSession", () => {
+    it("removes all clients for a specific session", async () => {
+      // #given
+      const session1Info: SkillMcpClientInfo = {
+        serverName: "server1",
+        skillName: "skill1",
+        sessionID: "session-1",
+      }
+      const session2Info: SkillMcpClientInfo = {
+        serverName: "server1",
+        skillName: "skill1",
+        sessionID: "session-2",
+      }
+
+      // #when
+      await manager.disconnectSession("session-1")
+
+      // #then
+      expect(manager.isConnected(session1Info)).toBe(false)
+      expect(manager.isConnected(session2Info)).toBe(false)
+    })
+
+    it("does not throw when session has no clients", async () => {
+      // #given / #when / #then
+      await expect(manager.disconnectSession("nonexistent")).resolves.toBeUndefined()
+    })
+  })
+
+  describe("disconnectAll", () => {
+    it("clears all clients", async () => {
+      // #given - no actual clients connected (would require real MCP server)
+
+      // #when
+      await manager.disconnectAll()
+
+      // #then
+      expect(manager.getConnectedServers()).toEqual([])
+    })
+  })
+
+  describe("isConnected", () => {
+    it("returns false for unconnected server", () => {
+      // #given
+      const info: SkillMcpClientInfo = {
+        serverName: "unknown",
+        skillName: "test",
+        sessionID: "session-1",
+      }
+
+      // #when / #then
+      expect(manager.isConnected(info)).toBe(false)
+    })
+  })
+
+  describe("getConnectedServers", () => {
+    it("returns empty array when no servers connected", () => {
+      // #given / #when / #then
+      expect(manager.getConnectedServers()).toEqual([])
+    })
+  })
+})

src/features/skill-mcp-manager/manager.ts

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+import { Client } from "@modelcontextprotocol/sdk/client/index.js"
+import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js"
+import type { Tool, Resource, Prompt } from "@modelcontextprotocol/sdk/types.js"
+import type { ClaudeCodeMcpServer } from "../claude-code-mcp-loader/types"
+import { expandEnvVarsInObject } from "../claude-code-mcp-loader/env-expander"
+import type { SkillMcpClientInfo, SkillMcpServerContext } from "./types"
+
+interface ManagedClient {
+  client: Client
+  transport: StdioClientTransport
+  skillName: string
+}
+
+export class SkillMcpManager {
+  private clients: Map<string, ManagedClient> = new Map()
+
+  private getClientKey(info: SkillMcpClientInfo): string {
+    return `${info.sessionID}:${info.skillName}:${info.serverName}`
+  }
+
+  async getOrCreateClient(
+    info: SkillMcpClientInfo,
+    config: ClaudeCodeMcpServer
+  ): Promise<Client> {
+    const key = this.getClientKey(info)
+    const existing = this.clients.get(key)
+
+    if (existing) {
+      return existing.client
+    }
+
+    const expandedConfig = expandEnvVarsInObject(config)
+    const client = await this.createClient(info, expandedConfig)
+    return client
+  }
+
+  private async createClient(
+    info: SkillMcpClientInfo,
+    config: ClaudeCodeMcpServer
+  ): Promise<Client> {
+    const key = this.getClientKey(info)
+
+    if (!config.command) {
+      throw new Error(
+        `MCP server "${info.serverName}" is missing required 'command' field.\n\n` +
+        `The MCP configuration in skill "${info.skillName}" must specify a command to execute.\n\n` +
+        `Example:\n` +
+        `  mcp:\n` +
+        `    ${info.serverName}:\n` +
+        `      command: npx\n` +
+        `      args: [-y, @some/mcp-server]`
+      )
+    }
+
+    const command = config.command
+    const args = config.args || []
+
+    const mergedEnv: Record<string, string> = {}
+    if (config.env) {
+      for (const [key, value] of Object.entries(process.env)) {
+        if (value !== undefined) mergedEnv[key] = value
+      }
+      Object.assign(mergedEnv, config.env)
+    }
+
+    const transport = new StdioClientTransport({
+      command,
+      args,
+      env: config.env ? mergedEnv : undefined,
+    })
+
+    const client = new Client(
+      { name: `skill-mcp-${info.skillName}-${info.serverName}`, version: "1.0.0" },
+      { capabilities: {} }
+    )
+
+    try {
+      await client.connect(transport)
+    } catch (error) {
+      const errorMessage = error instanceof Error ? error.message : String(error)
+      throw new Error(
+        `Failed to connect to MCP server "${info.serverName}".\n\n` +
+        `Command: ${command} ${args.join(" ")}\n` +
+        `Reason: ${errorMessage}\n\n` +
+        `Hints:\n` +
+        `  - Ensure the command is installed and available in PATH\n` +
+        `  - Check if the MCP server package exists\n` +
+        `  - Verify the args are correct for this server`
+      )
+    }
+
+    this.clients.set(key, { client, transport, skillName: info.skillName })
+    return client
+  }
+
+  async disconnectSession(sessionID: string): Promise<void> {
+    const keysToRemove: string[] = []
+
+    for (const [key, managed] of this.clients.entries()) {
+      if (key.startsWith(`${sessionID}:`)) {
+        keysToRemove.push(key)
+        try {
+          await managed.client.close()
+        } catch {
+          // Ignore close errors - process may already be terminated
+        }
+      }
+    }
+
+    for (const key of keysToRemove) {
+      this.clients.delete(key)
+    }
+  }
+
+  async disconnectAll(): Promise<void> {
+    for (const [, managed] of this.clients.entries()) {
+      try {
+        await managed.client.close()
+      } catch { /* process may already be terminated */ }
+    }
+    this.clients.clear()
+  }
+
+  async listTools(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext
+  ): Promise<Tool[]> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.listTools()
+    return result.tools
+  }
+
+  async listResources(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext
+  ): Promise<Resource[]> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.listResources()
+    return result.resources
+  }
+
+  async listPrompts(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext
+  ): Promise<Prompt[]> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.listPrompts()
+    return result.prompts
+  }
+
+  async callTool(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext,
+    name: string,
+    args: Record<string, unknown>
+  ): Promise<unknown> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.callTool({ name, arguments: args })
+    return result.content
+  }
+
+  async readResource(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext,
+    uri: string
+  ): Promise<unknown> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.readResource({ uri })
+    return result.contents
+  }
+
+  async getPrompt(
+    info: SkillMcpClientInfo,
+    context: SkillMcpServerContext,
+    name: string,
+    args: Record<string, string>
+  ): Promise<unknown> {
+    const client = await this.getOrCreateClientWithRetry(info, context.config)
+    const result = await client.getPrompt({ name, arguments: args })
+    return result.messages
+  }
+
+  private async getOrCreateClientWithRetry(
+    info: SkillMcpClientInfo,
+    config: ClaudeCodeMcpServer
+  ): Promise<Client> {
+    try {
+      return await this.getOrCreateClient(info, config)
+    } catch (error) {
+      const key = this.getClientKey(info)
+      const existing = this.clients.get(key)
+      if (existing) {
+        try {
+          await existing.client.close()
+        } catch { /* process may already be terminated */ }
+        this.clients.delete(key)
+        return await this.getOrCreateClient(info, config)
+      }
+      throw error
+    }
+  }
+
+  getConnectedServers(): string[] {
+    return Array.from(this.clients.keys())
+  }
+
+  isConnected(info: SkillMcpClientInfo): boolean {
+    return this.clients.has(this.getClientKey(info))
+  }
+}

src/features/skill-mcp-manager/types.ts

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+import type { ClaudeCodeMcpServer } from "../claude-code-mcp-loader/types"
+
+export type SkillMcpConfig = Record<string, ClaudeCodeMcpServer>
+
+export interface SkillMcpClientInfo {
+  serverName: string
+  skillName: string
+  sessionID: string
+}
+
+export interface SkillMcpServerContext {
+  config: ClaudeCodeMcpServer
+  skillName: string
+}