Function generateFileAttachment

src/utils/attachments.ts:3102–3281

(
  filename: string,
  toolUseContext: ToolUseContext,
  successEventName: string,
  errorEventName: string,
  mode: 'compact' | 'at-mention',
  options?: {
    offset?: number
    limit?: number
  },
)

}

export async function generateFileAttachment(
  filename: string,
  toolUseContext: ToolUseContext,
  successEventName: string,
  errorEventName: string,
  mode: 'compact' | 'at-mention',
  options?: {
    offset?: number
    limit?: number
  },
): Promise<
  | FileAttachment
  | CompactFileReferenceAttachment
  | PDFReferenceAttachment
  | AlreadyReadFileAttachment
  | null
> {
  const { offset, limit } = options ?? {}

  // Check if file has a deny rule configured
  const appState = toolUseContext.getAppState()
  if (isFileReadDenied(filename, appState.toolPermissionContext)) {
    return null
  }

  // Check file size before attempting to read (skip for PDFs — they have their own size/page handling below)
  if (
    mode === 'at-mention' &&
    !isFileWithinReadSizeLimit(
      filename,
      getDefaultFileReadingLimits().maxSizeBytes,
    )
  ) {
    const ext = parse(filename).ext.toLowerCase()
    if (!isPDFExtension(ext)) {
      try {
        const stats = await getFsImplementation().stat(filename)
        logEvent('tengu_attachment_file_too_large', {
          size_bytes: stats.size,
          mode,
        } as AnalyticsMetadata_I_VERIFIED_THIS_IS_NOT_CODE_OR_FILEPATHS)
        return null
      } catch {
        // If we can't stat the file, proceed with normal reading (will fail later if file doesn't exist)
      }
    }
  }

  // For large PDFs on @ mention, return a lightweight reference instead of inlining
  if (mode === 'at-mention') {
    const pdfRef = await tryGetPDFReference(filename)
    if (pdfRef) {
      return pdfRef
    }
  }

  // Check if file is already in context with latest version
  const existingFileState = toolUseContext.readFileState.get(filename)