chenhg5/cc-connect · error

%s is not %s media (detected mime: %s)

Error message

%s is not %s media (detected mime: %s)

What it means

loadTypedFileAttachments verifies that every attachment supplied via `cc-connect send --media-type <type>` actually matches the requested media type. It compares the mime type detected from the file content/filename (via detectAttachmentMimeType) against the requested mediaType using attachmentMatchesMediaType; on mismatch it refuses the file rather than sending a wrongly-typed attachment to the platform. This prevents e.g. an image agent API from receiving a PDF that was passed by mistake.

Source

Thrown at cmd/cc-connect/send.go:253

	for _, path := range paths {
		data, fileName, mimeType, err := readAttachment(path, maxSize)
		if err != nil {
			return nil, err
		}
		files = append(files, core.FileAttachment{MimeType: mimeType, Data: data, FileName: fileName})
	}
	return files, nil
}

func loadTypedFileAttachments(paths []string, mediaType string, maxSize int64) ([]core.FileAttachment, error) {
	files := make([]core.FileAttachment, 0, len(paths))
	for _, path := range paths {
		data, fileName, mimeType, err := readAttachment(path, maxSize)
		if err != nil {
			return nil, err
		}
		if !attachmentMatchesMediaType(mimeType, fileName, mediaType) {
			return nil, fmt.Errorf("%s is not %s media (detected mime: %s)", path, mediaType, mimeType)
		}
		files = append(files, core.FileAttachment{MimeType: mimeType, Data: data, FileName: fileName})
	}
	return files, nil
}

func attachmentMatchesMediaType(mimeType, fileName, mediaType string) bool {
	ext := strings.ToLower(filepath.Ext(fileName))
	switch mediaType {
	case "audio":
		if strings.HasPrefix(mimeType, "audio/") {
			return true
		}
		switch ext {
		case ".aac", ".flac", ".m4a", ".mp3", ".oga", ".ogg", ".opus", ".wav":
			return true
		}
	case "video":

View on GitHub (pinned to 4000b2338a)

Solutions

1. Check the detected mime in the error message and replace the offending path with a file that matches the requested media type
2. Drop --media-type so the file is loaded as a generic file attachment (loadFileAttachments) instead of typed media
3. Fix the file extension if the content is actually of the requested type but named wrongly, so mime detection classifies it correctly

Example fix

// before
cc-connect send --media-type image ./assets/*
// after
cc-connect send --media-type image ./assets/photo.png ./assets/diagram.jpg

file="./assets/photo.png"; file "$file"  # verify mime matches --media-type before running send

When it happens

Trigger: Running `cc-connect send ... --media-type image` (or similar) while one of the given paths is a non-image file (e.g. a .txt, .pdf, or .mp4), so detectAttachmentMimeType returns a mime that does not satisfy attachmentMatchesMediaType for the requested type.

Common situations: Passing a glob that picks up non-matching files (e.g. `./assets/*` picking up a README), renaming a file with an image extension when it is actually another format, or confusing image vs file attachments on the send command.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

• attachment %s exceeds size limit (%d MB)
• %s must be true or false
• timeout_mins must be an integer
• invalid value for --log-max-size: %s
• invalid --platform-type %q, want feishu or lark

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/86e1abb08747cae2. Report an issue: GitHub.