test(mcp): serialize the proto-name suite on the shared mutation lock

The suite swaps NODE_ENV and the process-wide global and project MCP
configurations without holding sharedMutationLock, so bun can run it
alongside another state-mutating file: that file observes the injected
realserver/locallyreal fixtures, or its own updates are overwritten when
this teardown restores its snapshots.

Acquire the lock in setup and release it from a finally in teardown, the
same shape officialRegistry.test.ts uses.

Also cover the reserved __proto__ entry arriving from parsed file config.

Author: 0xfandom

src/services/mcp/config.protoName.test.ts

@@ -1,5 +1,9 @@
 import { afterEach, beforeEach, expect, test } from 'bun:test'
 
+import {
+  acquireSharedMutationLock,
+  releaseSharedMutationLock,
+} from '../../test/sharedMutationLock.js'
 import {
   getCurrentProjectConfig,
   getGlobalConfig,
@@ -9,6 +13,7 @@ import {
 import {
   addMcpConfig,
   getMcpConfigByName,
+  parseMcpConfig,
   removeMcpConfig,
 } from './config.js'
 
@@ -30,7 +35,12 @@ let savedProjectMcp: ReturnType<typeof getCurrentProjectConfig>['mcpServers']
 
 let savedNodeEnv: string | undefined
 
-beforeEach(() => {
+beforeEach(async () => {
+  // This suite swaps NODE_ENV and the process-wide global/project MCP configs,
+  // so it has to be serialized against the other state-mutating suites bun may
+  // run alongside it -- otherwise they observe the injected fixtures, or their
+  // updates are clobbered when this teardown restores a stale snapshot.
+  await acquireSharedMutationLock('services/mcp/config.protoName.test.ts')
   savedNodeEnv = process.env.NODE_ENV
   process.env.NODE_ENV = 'test'
   savedGlobalMcp = getGlobalConfig().mcpServers
@@ -46,15 +56,19 @@ beforeEach(() => {
 })
 
 afterEach(() => {
-  saveGlobalConfig(config => ({ ...config, mcpServers: savedGlobalMcp }))
-  saveCurrentProjectConfig(config => ({
-    ...config,
-    mcpServers: savedProjectMcp,
-  }))
-  if (savedNodeEnv === undefined) {
-    delete process.env.NODE_ENV
-  } else {
-    process.env.NODE_ENV = savedNodeEnv
+  try {
+    saveGlobalConfig(config => ({ ...config, mcpServers: savedGlobalMcp }))
+    saveCurrentProjectConfig(config => ({
+      ...config,
+      mcpServers: savedProjectMcp,
+    }))
+    if (savedNodeEnv === undefined) {
+      delete process.env.NODE_ENV
+    } else {
+      process.env.NODE_ENV = savedNodeEnv
+    }
+  } finally {
+    releaseSharedMutationLock()
   }
 })
 
@@ -97,6 +111,32 @@ test('reports proto-name removal as not found instead of succeeding', async () =
   }
 })
 
+test('surfaces a __proto__ entry in file config instead of dropping it', () => {
+  // A hand-authored .mcp.json can carry this name: the schema accepts it, but
+  // copying it into a plain object hits the prototype setter, so the entry
+  // vanished with no diagnostic and the user could not tell why their server
+  // did not exist. It must be reported, not silently discarded.
+  // Parsed from text, exactly as the real file is: JSON.parse creates a true
+  // own "__proto__" key, which an object literal would not.
+  const { config, errors } = parseMcpConfig({
+    configObject: JSON.parse(
+      '{"mcpServers":{"__proto__":{"command":"echo","args":[]},' +
+        '"realone":{"command":"echo","args":[]}}}',
+    ),
+    expandVars: false,
+    scope: 'project',
+    filePath: '/tmp/.mcp.json',
+  })
+
+  const protoError = errors.find(e => e.path === 'mcpServers.__proto__')
+  expect(protoError).toBeDefined()
+  expect(protoError?.message).toContain('reserved')
+  expect(protoError?.mcpErrorMetadata?.severity).toBe('fatal')
+  // The rest of the file still parses, and the bad name is not an own key.
+  expect(Object.hasOwn(config?.mcpServers ?? {}, 'realone')).toBe(true)
+  expect(Object.hasOwn(config?.mcpServers ?? {}, '__proto__')).toBe(false)
+})
+
 test('still allows adding and removing a real server name', async () => {
   await addMcpConfig('addedserver', { command: 'echo', args: [] }, 'user')
   expect(getMcpConfigByName('addedserver')).not.toBeNull()