File is encoded as UTF-16 BE which is not supported. Please

Error message

File is encoded as UTF-16 BE which is not supported. Please re-save as UTF-8 or UTF-16 LE, then retry.

What it means

Error "File is encoded as UTF-16 BE which is not supported. Please re-save as UTF-8 or UTF-16 LE, then retry." thrown in Fission-AI/OpenSpec.

Source

Thrown at src/core/completions/installers/powershell-installer.ts:37

    end: '# OPENSPEC:END',
  };

  constructor(homeDir: string = os.homedir()) {
    this.homeDir = homeDir;
  }

  /**
   * Detect the encoding of a file by inspecting its BOM (Byte Order Mark).
   * Returns the Node.js BufferEncoding and the raw BOM bytes to preserve on write.
   */
  private detectEncoding(buffer: Buffer): { encoding: BufferEncoding; bom: Buffer } {
    // UTF-16 LE BOM: FF FE
    if (buffer.length >= 2 && buffer[0] === 0xff && buffer[1] === 0xfe) {
      return { encoding: 'utf16le', bom: Buffer.from([0xff, 0xfe]) };
    }
    // UTF-16 BE BOM: FE FF — not natively supported by Node
    if (buffer.length >= 2 && buffer[0] === 0xfe && buffer[1] === 0xff) {
      throw new Error(
        'File is encoded as UTF-16 BE which is not supported. ' +
          'Please re-save as UTF-8 or UTF-16 LE, then retry.',
      );
    }
    // UTF-8 BOM: EF BB BF
    if (buffer.length >= 3 && buffer[0] === 0xef && buffer[1] === 0xbb && buffer[2] === 0xbf) {
      return { encoding: 'utf-8', bom: Buffer.from([0xef, 0xbb, 0xbf]) };
    }
    // No BOM → default UTF-8
    return { encoding: 'utf-8', bom: Buffer.alloc(0) };
  }

  /**
   * Read a profile file, preserving its encoding metadata for round-trip writes.
   * Throws if the file uses UTF-16 BE (unsupported by Node).
   */
  private async readProfileFile(filePath: string): Promise<{ content: string; encoding: BufferEncoding; bom: Buffer }> {
    const raw = await fs.readFile(filePath);

View on GitHub (pinned to 6926ccb18a)

When it happens

Trigger: Thrown at src/core/completions/installers/powershell-installer.ts:37 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Fission-AI/OpenSpec@6926ccb18a (2026-08-25). Data as JSON: /api/errors/761632ff7d9245bb. Report an issue: GitHub.