CherryHQ/cherry-studio · warning · Error

Invalid MCP package upload: file name cannot contain leading

Error message

Invalid MCP package upload: file name cannot contain leading or trailing whitespace

What it means

Thrown by validatePackageUploadPayload when fileName !== fileName.trim(), i.e. the value has leading or trailing whitespace. The service rejects this because (a) the temp-file path is built from the filename and surrounding whitespace causes confusing path errors, and (b) it almost always indicates a frontend string-handling bug rather than an intentional filename.

Source

Thrown at src/main/ai/mcp/McpPackageService.ts:291

  return resolvedEnv
}

export function validatePackageUploadPayload(
  fileBuffer: ArrayBuffer | NodeJS.ArrayBufferView,
  fileName: string,
  packageFormat: McpPackageFormat
): Buffer {
  if (typeof fileName !== 'string') {
    throw new Error('Invalid MCP package upload: file name must be a string')
  }

  const trimmedFileName = fileName.trim()
  if (!trimmedFileName) {
    throw new Error('Invalid MCP package upload: file name cannot be empty')
  }
  if (trimmedFileName !== fileName) {
    throw new Error('Invalid MCP package upload: file name cannot contain leading or trailing whitespace')
  }
  if (trimmedFileName.includes('\0') || /[/\\]/.test(trimmedFileName)) {
    throw new Error('Invalid MCP package upload: file name cannot contain path separators')
  }
  if (!/^[A-Za-z0-9._ ()@+-]+$/.test(trimmedFileName)) {
    throw new Error('Invalid MCP package upload: file name contains unsupported characters')
  }
  if (path.extname(trimmedFileName).toLowerCase() !== `.${packageFormat}`) {
    throw new Error(`Invalid MCP package upload: expected a .${packageFormat} file`)
  }

  let buffer: Buffer
  if (fileBuffer instanceof ArrayBuffer) {
    buffer = Buffer.from(fileBuffer)
  } else if (ArrayBuffer.isView(fileBuffer)) {
    buffer = Buffer.from(fileBuffer.buffer, fileBuffer.byteOffset, fileBuffer.byteLength)
  } else {
    throw new Error('Invalid MCP package upload: file buffer must be an ArrayBuffer')

View on GitHub (pinned to 726446b54c)

Solutions

On the renderer, pass file.name directly rather than a constructed or user-typed string; do not trim there because the service wants the raw value to detect the bug.
Find the code path that added the whitespace (often a template literal or label concat) and remove it.
Retry the upload once the frontend sends the verbatim File.name.

Example fix

// renderer - before
const fileName = `upload: ${file.name}`
// after
const fileName = file.name

Defensive patterns

Strategy: validation

Validate before calling

function hasNoSurroundingWhitespace(s: string): boolean {
  return s === s.trim()
}

Type guard

function isTrimmedString(s: unknown): s is string {
  return typeof s === 'string' && s.length > 0 && s === s.trim()
}

Prevention

Pass the verbatim File.name; do not construct filenames by concatenation with labels or prefixes.
If the filename is user-typed, trim is the renderer's responsibility — but the service intentionally rejects pre-trimmed whitespace as a bug signal, so send a clean value.
Add a renderer lint rule that flags template literals used to build filenames.

When it happens

Trigger: Renderer sent fileName = " pkg.mcpb" or "pkg.dxt\n". Common when the filename was concatenated with a separator and not trimmed, or when copy-pasted from a label that included padding spaces.

Common situations: The filename was read from a UI label or template literal that introduced spaces; a user typed the filename manually with stray spaces; the IPC payload builder did `somePrefix + ' ' + file.name`.

Related errors

AI-assisted analysis of CherryHQ/cherry-studio@726446b54c (2026-08-12). Data as JSON: /api/errors/769a5ff92d6b728b. Report an issue: GitHub.