Method execution

packages/agent-core/src/tools/builtin/file/read.ts:264–323

(args: ReadInput, safePath: string)

  }

  private async execution(args: ReadInput, safePath: string): Promise<ExecutableToolResult> {
    try {
      let stat: StatResult;
      try {
        stat = await this.kaos.stat(safePath);
      } catch (error) {
        if (isFileNotFoundError(error)) {
          return { isError: true, output: `"${args.path}" does not exist.` };
        }
        throw error;
      }
      if (!isRegularFileMode(stat.stMode)) {
        return { isError: true, output: `"${args.path}" is not a file.` };
      }

      const header = await readTextHeader(this.kaos, safePath, MEDIA_SNIFF_BYTES);
      const fileType = detectFileType(safePath, header);
      if (fileType.kind === 'image' || fileType.kind === 'video') {
        return {
          isError: true,
          output: `"${args.path}" is a ${fileType.kind} file. Use ReadMediaFile to read image or video files.`,
        };
      }
      if (fileType.kind === 'unknown') {
        return {
          isError: true,
          output: notReadableFileOutput(args.path),
        };
      }

      const lineOffset = args.line_offset ?? 1;
      const requestedLines = args.n_lines ?? MAX_LINES;
      const effectiveLimit = Math.min(requestedLines, MAX_LINES);

      if (lineOffset < 0) {
        return await this.readTail(
          safePath,
          args.path,
          lineOffset,
          effectiveLimit,
          requestedLines,
        );
      }
      return await this.readForward(
        safePath,
        args.path,
        lineOffset,
        effectiveLimit,
        requestedLines,
      );
    } catch (error) {
      if (isTextDecodeError(error)) {
        return { isError: true, output: notReadableFileOutput(args.path) };
      }
      return {
        isError: true,
        output: error instanceof Error ? error.message : String(error),
      };