BoundaryML/baml · error

invalid checksum format

Error message

invalid checksum format '%s' for %s in %s

What it means

A line in the checksum file matched the target filename, but the extracted checksum string failed the isHex validation (non-empty, even-length, hex characters). The file contents are malformed, so downloadChecksum refuses to return an untrustworthy value.

Solutions

1. Inspect the checksum file at checksumURL and confirm its format matches '<hex> <filename>'
2. Regenerate/publish the checksum file with sha256sum output format
3. If a mirror serves an HTML error page, fix the mirror or use the canonical URL
4. Update library code if upstream changed the checksum file format

Example fix

// before: mismatched checksum file format
myfile.bin:e3b0c442...   // parsed field fails isHex
// after: publish standard format
e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  myfile.bin

func validChecksumLine(line string) bool {
    f := strings.Fields(line)
    return len(f) >= 2 && len(f[0])%2 == 0 && isHexString(f[0])
}

func isHexChecksum(s string) bool {
    if len(s) == 0 || len(s)%2 != 0 { return false }
    _, err := hex.DecodeString(s)
    return err == nil
}

if _, err := downloadChecksum(url, name); err != nil && strings.Contains(err.Error(), "invalid checksum format") {
    logger.Warn("malformed checksum file; skipping verification", "url", url)
}

When it happens

Trigger: The checksum file contains a line whose second field for targetFilename is not a valid hex hash — e.g. 'sha256' prefixed column, a text placeholder, or a truncated/garbage hash.

Common situations: Checksum file generated by a tool with a different format (e.g. '<hash> <file>' vs '<file>:<hash>' parsed incorrectly), a partially written checksum file, or an HTML error page saved as .sha256.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• blob digest mismatch for
• blob size mismatch for
• checksum for ' ' not found within file
• invalid SHA-256 checksum
• invalid sha256 blob digest; expected only hex characters

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/0d7fd4470e05017d. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_go/baml_go/lib_common.go:611

	if err != nil {
		return "", fmt.Errorf("error reading checksum body %s: %w", checksumURL, err)
	}

	lines := strings.Split(string(bodyBytes), "\n")
	for _, line := range lines {
		parts := strings.Fields(line)
		if len(parts) >= 2 {
			checksum, filenameInLine := parts[0], strings.TrimPrefix(parts[1], "*")
			if filenameInLine == targetFilename {
				if len(checksum) == 64 && isHex(checksum) {
					logger.Debug("Found matching checksum in file", "filename", targetFilename, "checksum", checksum)
					return checksum, nil
				}
				logger.Warn("Invalid checksum format found in checksum file",
					"url", checksumURL,
					"filename", targetFilename,
					"found_checksum", checksum)
				return "", fmt.Errorf("invalid checksum format '%s' for %s in %s", checksum, targetFilename, checksumURL)
			}
		}
	}

	logger.Warn("Checksum for target file not found within checksum file",
		"url", checksumURL,
		"target_filename", targetFilename)
	return "", fmt.Errorf("checksum for '%s' not found within file %s", targetFilename, checksumURL)
}

func isHex(s string) bool {
	if len(s) == 0 {
		return false
	}
	for _, r := range s {
		if !((r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')) {
			return false
		}

View on GitHub (pinned to bd85ce9dee)