Tencent/WeKnora · error

failed to create HTTP streamable client: %w

Error message

failed to create HTTP streamable client: %w

What it means

NewMCPClient wraps errors from NewStreamableHttpClient or NewOAuthStreamableHttpClient with 'failed to create HTTP streamable client'. As with SSE, construction-time failures are almost always URL parse errors or invalid options; network problems surface later in Connect, not here.

Source

Thrown at internal/mcp/client.go:222

		}
	case types.MCPTransportHTTPStreamable:
		if config.Service.URL == nil || *config.Service.URL == "" {
			return nil, fmt.Errorf("URL is required for HTTP Streamable transport")
		}
		if useOAuth {
			mcpClient, err = client.NewOAuthStreamableHttpClient(*config.Service.URL, oauthConfig,
				transport.WithHTTPBasicClient(httpClient),
				transport.WithHTTPHeaders(headers),
			)
		} else {
			// For HTTP streamable, we need to use transport options
			mcpClient, err = client.NewStreamableHttpClient(*config.Service.URL,
				transport.WithHTTPBasicClient(httpClient),
				transport.WithHTTPHeaders(headers),
			)
		}
		if err != nil {
			return nil, fmt.Errorf("failed to create HTTP streamable client: %w", err)
		}
	case types.MCPTransportStdio:
		// Stdio transport is disabled for security reasons (potential command injection vulnerabilities)
		return nil, fmt.Errorf("stdio transport is disabled for security reasons; please use SSE or HTTP Streamable transport instead")
	default:
		return nil, ErrUnsupportedTransport
	}

	instance := &mcpGoClient{
		service: config.Service,
		client:  mcpClient,
	}
	if useOAuth {
		instance.oauth = newOAuthRuntime(
			config.OAuthRepo,
			config.TenantID,
			config.Principal,
			config.Service.ID,

View on GitHub (pinned to 988cbb0330)

Solutions

1. Read the wrapped cause after 'failed to create HTTP streamable client:' for the real error
2. Validate the URL with url.Parse and require http/https before calling NewMCPClient
3. Correct the stored service URL to an absolute https endpoint
4. If OAuth, verify the OAuthConfig fields are valid before construction

Example fix

// before
mcpClient, err = client.NewStreamableHttpClient("http://bad url\tmcp", ...)
// after
endpoint := strings.TrimSpace(cfg.URL)
if _, perr := url.Parse(endpoint); perr != nil {
    return nil, fmt.Errorf("invalid streamable URL: %w", perr)
}
mcpClient, err = client.NewStreamableHttpClient(endpoint, ...)

func validStreamableURL(raw *string) bool {
    if raw == nil || *raw == "" { return false }
    u, err := url.Parse(strings.TrimSpace(*raw))
    return err == nil && (u.Scheme == "http" || u.Scheme == "https") && u.Host != ""
}

func asCreateStreamableErr(err error) (cause error, ok bool) {
    if err == nil || !strings.Contains(err.Error(), "failed to create HTTP streamable client") { return nil, false }
    return errors.Unwrap(err), true
}

mcpClient, err := NewMCPClient(cfg)
if err != nil {
    if strings.Contains(err.Error(), "failed to create HTTP streamable client") {
        return fmt.Errorf("bad streamable endpoint %q: %v", *cfg.Service.URL, errors.Unwrap(err))
    }
    return err
}

When it happens

Trigger: NewMCPClient with TransportType == MCPTransportHTTPStreamable and a non-empty URL that the streamable client constructor rejects (malformed/unsupported URL), or an OAuth streamable client rejecting the URL/OAuth options.

Common situations: Typo in URL scheme (ftp://, ws://); URL with control characters loaded from config; endpoint missing the /mcp path so later calls fail but construction itself fails only on parse errors.

Understand the failure class

Background: "Invalid URL" / "URL cannot be empty": fix the malformed or missing URL behind request-construction failures — this error's family across 50 libraries.

Related errors

• failed to create SSE client: %w
• invalid URL: %w
• fetch failed: %w
• create request: %w
• execute request: %w

AI-assisted analysis of Tencent/WeKnora@988cbb0330 (2026-09-02). Data as JSON: /api/errors/1acda3978a227ac8. Report an issue: GitHub.