What causes "file type requires mimetype" in wavetermdev/waveterm?

Set MimeType explicitly, e.g. "image/png" or "application/pdf"

file type requires mimetype

Error message

file type requires mimetype

What it means

Validation error: a file-type message part is missing the required mimetype field.

Source

Thrown at pkg/aiusechat/uctypes/uctypes.go:415

func (p *AIMessagePart) Validate() error {
	if p.Type == AIMessagePartTypeText {
		if p.Text == "" {
			return fmt.Errorf("text type requires non-empty text field")
		}
		// Check that no file fields are set
		if p.FileName != "" || p.MimeType != "" || len(p.Data) > 0 || p.URL != "" {
			return fmt.Errorf("text type cannot have file fields set")
		}
		return nil
	}

	if p.Type == AIMessagePartTypeFile {
		if p.Text != "" {
			return fmt.Errorf("file type cannot have text field set")
		}

		if p.MimeType == "" {
			return fmt.Errorf("file type requires mimetype")
		}

		// Either data or url (not both) must be set
		hasData := len(p.Data) > 0
		hasURL := p.URL != ""

		if !hasData && !hasURL {
			return fmt.Errorf("file type requires either data or url")
		}

		if hasData && hasURL {
			return fmt.Errorf("file type cannot have both data and url set")
		}

		// If URL is set, validate it's https or data URL
		if hasURL {
			parsedURL, err := url.Parse(p.URL)
			if err != nil {

View on GitHub (pinned to a4447c1563)

Solutions

Set MimeType explicitly, e.g. "image/png" or "application/pdf"
Detect the type with http.DetectContentType(data) before building the part
Fix the client JSON to include the "mimetype" field

Example fix

// before
part := uctypes.AIMessagePart{Type: "file", Data: data}
// after
part := uctypes.AIMessagePart{Type: "file", MimeType: http.DetectContentType(data), Data: data}

Defensive patterns

Strategy: validation

Validate before calling

func hasMimeType(p uctypes.AIMessagePart) bool {
	return p.Type == uctypes.AIMessagePartTypeFile && p.MimeType != ""
}
// mime := http.DetectContentType(data) when unknown

Type guard

func asTypedFilePart(p uctypes.AIMessagePart) (mime string, ok bool) {
	if p.Type == uctypes.AIMessagePartTypeFile && p.MimeType != "" {
		return p.MimeType, true
	}
	return "", false
}

Prevention

Sniff MIME with http.DetectContentType when the type is unknown
Include the "mimetype" key in client JSON payloads
Never build a file part literal without MimeType

When it happens

Trigger: AIMessagePart{Type:"file", Data: data} or {Type:"file", URL: ...} with MimeType left empty, then Validate() is called (directly or via AIMessage.Validate on a POSTed message).

Common situations: Constructing a file part from raw bytes without sniffing the content type; JSON payloads omitting the "mimetype" key; inferring MIME from extension and getting empty string for extensionless files.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of wavetermdev/waveterm@a4447c1563 (2026-09-01). Data as JSON: /api/errors/62e98ebe7bdffa15. Report an issue: GitHub.