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fix: prevent MCP server restart when toggling tool permissions #8233

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fix: prevent MCP server restart when toggling tool permissions #8233

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42 changes: 40 additions & 2 deletions src/services/mcp/McpHub.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,7 @@ export class McpHub {
isConnecting: boolean = false
private refCount: number = 0 // Reference counter for active clients
private configChangeDebounceTimers: Map<string, NodeJS.Timeout> = new Map()
private isProgrammaticUpdate: boolean = false // Flag to track programmatic config updates
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@roomote roomote bot Sep 22, 2025

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Missing test coverage: Consider adding specific test cases for the isProgrammaticUpdate flag behavior to ensure file watchers are properly skipped during programmatic updates. This would help catch any regression in this critical functionality.


constructor(provider: ClineProvider) {
this.providerRef = new WeakRef(provider)
Expand Down Expand Up @@ -278,6 +279,11 @@ export class McpHub {
* Debounced wrapper for handling config file changes
*/
private debounceConfigChange(filePath: string, source: "global" | "project"): void {
// Skip if this is a programmatic update
if (this.isProgrammaticUpdate) {
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@roomote roomote bot Sep 22, 2025

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Potential race condition: There's a risk that file system watcher events could fire between setting/unsetting the isProgrammaticUpdate flag and the actual file operations. Consider using a more robust synchronization mechanism, such as:

  • A promise-based queue for file operations
  • A unique operation ID system to track programmatic updates
  • Or increasing the debounce timeout in debounceConfigChange to be longer than the 100ms wait

return
}

const key = `${source}-${filePath}`

// Clear existing timer if any
Expand Down Expand Up @@ -1463,7 +1469,28 @@ export class McpHub {
mcpServers: config.mcpServers,
}

await fs.writeFile(configPath, JSON.stringify(updatedConfig, null, 2))
// Check if this is a minor update that shouldn't trigger a restart
const isMinorUpdate = Object.keys(configUpdate).every(
(key) => key === "alwaysAllow" || key === "disabledTools" || key === "timeout",
)

if (isMinorUpdate) {
// Set flag to indicate programmatic update
this.isProgrammaticUpdate = true
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@roomote roomote bot Sep 22, 2025

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Code duplication: This pattern of setting flag → writing → waiting → resetting flag is duplicated in updateServerToolList. Consider extracting into a helper method:

private async writeConfigWithoutTriggeringWatcher(
  configPath: string,
  config: any
): Promise<void> {
  this.isProgrammaticUpdate = true;
  try {
    await fs.writeFile(configPath, JSON.stringify(config, null, 2));
    await new Promise((resolve) => setTimeout(resolve, 100));
  } finally {
    this.isProgrammaticUpdate = false;
  }
}


try {
await fs.writeFile(configPath, JSON.stringify(updatedConfig, null, 2))

// Give file system watchers a moment to process
await new Promise((resolve) => setTimeout(resolve, 100))
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@roomote roomote bot Sep 22, 2025

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Hardcoded timeout concern: The 100ms timeout might not be sufficient on slower systems or under heavy I/O load. Consider:

  • Making this configurable via settings
  • Using file system events to confirm write completion
  • Or implementing exponential backoff if issues persist

} finally {
// Always reset the flag
this.isProgrammaticUpdate = false
}
} else {
// For major updates, allow normal file watcher behavior
await fs.writeFile(configPath, JSON.stringify(updatedConfig, null, 2))
}
}

public async updateServerTimeout(
Expand Down Expand Up @@ -1686,7 +1713,18 @@ export class McpHub {
targetList.splice(toolIndex, 1)
}

await fs.writeFile(normalizedPath, JSON.stringify(config, null, 2))
// Set flag to indicate programmatic update
this.isProgrammaticUpdate = true

try {
await fs.writeFile(normalizedPath, JSON.stringify(config, null, 2))

// Give file system watchers a moment to process
await new Promise((resolve) => setTimeout(resolve, 100))
} finally {
// Always reset the flag
this.isProgrammaticUpdate = false
}

if (connection) {
connection.server.tools = await this.fetchToolsList(serverName, source)
Expand Down
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