Function buildDownloadPath

src/services/api/filesApi.ts:187–210

(
  basePath: string,
  sessionId: string,
  relativePath: string,
)

 * Returns null if the path is invalid (e.g., path traversal).
 */
export function buildDownloadPath(
  basePath: string,
  sessionId: string,
  relativePath: string,
): string | null {
  const normalized = path.normalize(relativePath)
  if (normalized.startsWith('..')) {
    logDebugError(
      `Invalid file path: ${relativePath}. Path must not traverse above workspace`,
    )
    return null
  }

  const uploadsBase = path.join(basePath, sessionId, 'uploads')
  const redundantPrefixes = [
    path.join(basePath, sessionId, 'uploads') + path.sep,
    path.sep + 'uploads' + path.sep,
  ]
  const matchedPrefix = redundantPrefixes.find(p => normalized.startsWith(p))
  const cleanPath = matchedPrefix
    ? normalized.slice(matchedPrefix.length)
    : normalized
  return path.join(uploadsBase, cleanPath)
}

/**
 * Downloads a file and saves it to the session-specific workspace directory