chenhg5/cc-connect · error

attachment exceeds %d bytes

Error message

attachment exceeds %d bytes

What it means

The attachment body downloaded from MAX exceeded maxAttachmentBytes. The reader is capped at maxAttachmentBytes+1 so any payload strictly larger than the limit is detected and rejected before it can exhaust memory.

Source

Thrown at platform/max/max.go:1205

	defer cancel()
	req, err := http.NewRequestWithContext(dlCtx, http.MethodGet, url, nil)
	if err != nil {
		return nil, "", err
	}
	resp, err := p.client.Do(req)
	if err != nil {
		return nil, "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return nil, "", fmt.Errorf("HTTP %d", resp.StatusCode)
	}
	data, err := io.ReadAll(io.LimitReader(resp.Body, maxAttachmentBytes+1))
	if err != nil {
		return nil, "", err
	}
	if len(data) > maxAttachmentBytes {
		return nil, "", fmt.Errorf("attachment exceeds %d bytes", maxAttachmentBytes)
	}
	return data, resp.Header.Get("Content-Type"), nil
}

// resolveMediaURL asks MAX for the playable/downloadable URL of a video or
// audio attachment. MAX delivers only an opaque token in the message payload
// and exposes /videos/{token} and /audios/{token} for resolution.
func (p *Platform) resolveMediaURL(ctx context.Context, kind, token string) (string, string, error) {
	if token == "" {
		return "", "", fmt.Errorf("empty token")
	}
	endpoint := "/videos/"
	if kind == "audio" {
		endpoint = "/audios/"
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, p.apiBase+endpoint+token, nil)
	if err != nil {
		return "", "", err

View on GitHub (pinned to 4000b2338a)

Solutions

1. Increase maxAttachmentBytes if your deployment can afford larger transfers
2. Reply to the user that the attachment is too large to relay instead of surfacing a raw error
3. Check Content-Length before reading to fail fast
4. Compress or link to the original URL instead of downloading the full payload

Example fix

// before
data, ct, err := p.downloadAttachment(ctx, url)
if err != nil { return err }
// after
data, ct, err := p.downloadAttachment(ctx, url)
if err != nil {
	if strings.Contains(err.Error(), "attachment exceeds") {
		return sendTooLargeNotice(chatID)
	}
	return err
}

if att.Size > maxAttachmentBytes { return sendTooLargeNotice(chatID) }

if _, _, err := dl(); err != nil && strings.Contains(err.Error(), "attachment exceeds") {
	return gracefulTooLargeReply()
}

When it happens

Trigger: A user sends an image or file through MAX whose size is larger than maxAttachmentBytes; downloadAttachment reads maxAttachmentBytes+1 bytes and the extra byte triggers this error.

Common situations: Users sharing large videos/high-res photos through the bot bridge; deployment with a conservatively small maxAttachmentBytes configured.

Understand the failure class

Background: "File too large" / "file size exceeds limit" errors: why libraries cap file sizes and how to fix them — this error's family across 46 libraries.

Related errors

• weixin: %s: response body exceeds %d bytes
• attachment send is disabled by config
• hook input exceeds %d bytes
• codex app-server line exceeds max size (%d bytes): %w
• Content-Length too large: %d

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/986972999b0f2a28. Report an issue: GitHub.