getsops/sops · error

Error while serializing metadata: %w

Error message

Error while serializing metadata: %w

What it means

Wrapper emitted by SerializeMetadata when converting the tree's Metadata into an embeddable tree branch (metadataToTreeBranch) fails. The underlying cause is typically the metadata conversion producing an invalid structure (see related internal error) or missing required metadata fields.

Source

Thrown at stores/metadata.go:272

	err = d.Decode(md)
	if err != nil {
		return nil, err
	}
	metadata, err := goToSops(mdMap)
	if err != nil {
		return nil, err
	}
	if tb, ok := metadata.(sops.TreeBranch); ok {
		return tb, nil
	}
	return nil, fmt.Errorf("Internal error: unexpected metadata conversion result %T", metadata)
}

// SerializeMetadata embeds the metadata of `data` into its tree branches.
func SerializeMetadata(data sops.Tree, opts MetadataOpts) (sops.TreeBranches, error) {
	md, err := metadataToTreeBranch(metadataFromInternal(data.Metadata))
	if err != nil {
		return nil, fmt.Errorf("Error while serializing metadata: %w", err)
	}
	if opts.Flatten != MetadataFlattenNone {
		var prefix string
		if opts.Flatten == MetadataFlattenFull {
			prefix = SopsPrefix
		}
		md, err = flattenTreeBranch(md, prefix)
		if err != nil {
			return nil, fmt.Errorf("Error while flattening metadata: %w", err)
		}
		if opts.EscapeNewlines {
			for i, item := range md {
				if value, ok := item.Value.(string); ok {
					md[i] = sops.TreeItem{
						Key:   item.Key,
						Value: strings.ReplaceAll(value, "\n", "\\n"),
					}
				}

View on GitHub (pinned to 13442bb981)

Solutions

1. Inspect the wrapped cause (%w target) to find which metadata field is invalid
2. Populate all required Metadata fields (KeyGroups, ShamirThreshold/SShards, MAC, Version, LastModified)
3. Populate trees via LoadEncryptedFile instead of manual construction
4. Check library/file version compatibility

Example fix

// before
tree.Metadata = sops.Metadata{}
out, err := stores.SerializeMetadata(tree, opts) // "Error while serializing metadata"
// after
tree.Metadata.KeyGroups = [][]keyservice.Key{{{Recipient: "..."}}}
tree.Metadata.ShamirThreshold = 1
tree.Metadata.Version = "3.9.0"
out, err := stores.SerializeMetadata(tree, opts)

func validMetadata(md sops.Metadata) error {
	if len(md.KeyGroups) == 0 {
		return errors.New("metadata missing key groups")
	}
	if md.ShamirThreshold > len(md.KeyGroups) {
		return errors.New("shamir threshold exceeds key group count")
	}
	if md.Version == "" {
		return errors.New("metadata missing version")
	}
	return nil
}

out, err := stores.SerializeMetadata(tree, opts)
if err != nil {
	var serErr *fmt.wrapError // use errors.As/Is on the underlying cause
	if strings.HasPrefix(err.Error(), "Error while serializing metadata") {
		return fmt.Errorf("invalid tree metadata: %w", err)
	}
	return err
}

When it happens

Trigger: Calling SerializeMetadata or EmitEncryptedFile with a sops.Tree whose Metadata cannot be converted to a tree branch — e.g. hand-built Metadata missing key groups, shards, or MAC, or an inconsistent internal representation.

Common situations: Custom encryption tooling that constructs sops.Metadata programmatically, version mismatches between library and file metadata, or trees populated from non-standard sources.

Related errors

• Error marshaling metadata: %s
• Error marshaling metadata: %s
• Found duplicate %v entry
• Error while flattening metadata: %w
• Found key %q in encrypted data, which starts with the reserv

AI-assisted analysis of getsops/sops@13442bb981 (2026-09-01). Data as JSON: /api/errors/c622b675f72434b6. Report an issue: GitHub.