sipeed/picoclaw · error

slack_webhook: webhook %q has invalid URL format: %w

Error message

slack_webhook: webhook %q has invalid URL format: %w

What it means

During webhook validation, each webhook_url is passed through url.Parse; a parse error is wrapped as "webhook %q has invalid URL format". Go's url.Parse only errors on genuinely malformed input — control characters, unmatched brackets in the host, or a URL that is not absolute when later used as a request target — so this fires on corrupted values rather than merely unusual ones.

Source

Thrown at pkg/channels/slack_webhook/slack_webhook.go:53

	cfg *config.SlackWebhookSettings,
	bus *bus.MessageBus,
) (*SlackWebhookChannel, error) {
	if len(cfg.Webhooks) == 0 {
		return nil, fmt.Errorf("slack_webhook: at least one webhook target is required")
	}

	if _, hasDefault := cfg.Webhooks["default"]; !hasDefault {
		return nil, fmt.Errorf("slack_webhook: a 'default' webhook target is required")
	}

	for name, target := range cfg.Webhooks {
		webhookURL := target.WebhookURL.String()
		if webhookURL == "" {
			return nil, fmt.Errorf("slack_webhook: webhook %q has empty webhook_url", name)
		}
		parsed, err := url.Parse(webhookURL)
		if err != nil {
			return nil, fmt.Errorf("slack_webhook: webhook %q has invalid URL format: %w", name, err)
		}
		if !strings.EqualFold(parsed.Scheme, "https") {
			return nil, fmt.Errorf("slack_webhook: webhook %q must use HTTPS (got %q)", name, parsed.Scheme)
		}
	}

	base := channels.NewBaseChannel(
		"slack_webhook",
		cfg,
		bus,
		[]string{"*"},
		channels.WithMaxMessageLength(40000),
	)

	return &SlackWebhookChannel{
		BaseChannel: base,
		bc:          bc,
		config:      cfg,

View on GitHub (pinned to 49183d7e8d)

Solutions

1. Re-paste the webhook URL as plain text from the Slack app settings page; strip stray whitespace, quotes, and control characters.
2. The wrapped error names the byte offset/reason — read errors.Unwrap(err) (a *url.Error) to find what character is offending.
3. Quote the value in YAML (webhook_url: "https://...") to avoid parser-induced mutations.

Example fix

// before
url := webhookURLFromUser // may contain \r\n from clipboard

// after: sanitize before saving config
cleaned := strings.TrimSpace(strings.Map(func(r rune) rune {
    if r < 32 { return -1 } // strip control chars
    return r
}, raw))
if _, err := url.Parse(cleaned); err != nil { return fmt.Errorf("bad webhook_url: %w", err) }

func validWebhookURL(raw string) error {
    u, err := url.Parse(strings.TrimSpace(raw))
    if err != nil { return fmt.Errorf("unparseable webhook_url: %w", err) }
    if u.Scheme == "" || u.Host == "" { return fmt.Errorf("webhook_url must be absolute") }
    return nil
}

// Go: if err wraps *url.Error (errors.As) -> extract and log the parse reason; fail config validation, not runtime

When it happens

Trigger: webhook_url containing raw control characters (\x00, \r), a value wrapped in quotes/smart quotes copied from a rich-text editor, embedded newlines from terminal line-wrapping, or a truncated paste that leaves an unbalanced URL; note a missing scheme alone does not fail url.Parse here — it is caught by the HTTPS check instead.

Common situations: Copying URLs from chat/email clients that insert invisible characters or line breaks; YAML block scalars accidentally including trailing garbage; encoding mishaps (non-UTF8 bytes) after editing config on different platforms; placeholder text like ${WEBHOOK_URL} left unreplaced is usually caught by the HTTPS check, not this one.

Related errors

• MCP server ${server.name} requires a URL.
• MCP server ${server.name} requires a valid HTTP(S) URL.
• invalid WeCom QR generate URL: %w
• invalid WeCom QR query URL: %w
• invalid WeCom QR page URL: %w

AI-assisted analysis of sipeed/picoclaw@49183d7e8d (2026-08-15). Data as JSON: /api/errors/7be90d56301d1d0a. Report an issue: GitHub.