🐞 Bug Summary

Encountered a scenario in deployed environments where the content-length header is occasionally missing from the response when calling the version/metrics tab. This is causing issues in content-length validation and proper response processing.
In cases where the Content-Length header is absent, we should be able to verify the content length using the content itself. The lack of this header leads to inconsistencies and bugs in client-side or server-side code that depend on it.

Root cause could be:

1. Intermediaries such as Proxies or load balancers might strip or modify the Content-Length header.
2. In case of Chunked transfer encoding, response body is sent in chunks, making Content-Length unnecessary.
3. Compressed content may omit Content-Length as the server doesn’t adjust for compressed size.

🧩 Affected Component

Select the area of the project impacted:

• mcpgateway - API
• mcpgateway - UI (admin panel)
• mcpgateway.wrapper - stdio wrapper
• Federation or Transports
• CLI, Makefiles, or shell scripts
• Container setup (Docker/Podman/Compose)
• Other (explain below)

🔁 Steps to Reproduce

1. In deployed Environments, with middleware in place.
2. Version and Metrics tab fails to load.

🤔 Expected Behavior

Check for content-length header in response, if not present, check the length on the response received to confirm if the content is empty or not.

📓 Logs / Error Output

Version Tab:

Metrics Tab:

🧩 Additional Context (optional)

Code changes:

Current code:

if (
    response.status === 0 ||
    (response.ok &&
        response.status === 200 &&
        !response.headers.get("content-length"))
) {
    console.warn(`Empty response received from ${url}`);
    throw new Error("Server returned an empty response");
}

New Code:

if (response.status === 0 || (response.ok && response.status === 200)) {
    const contentLength = response.headers.get("content-length");

    // Check Content-Length if present
    if (contentLength !== null) {
        if (parseInt(contentLength, 10) === 0) {
            throw new Error("Server returned an empty response (via header)");
        }
    } else {
        // Fallback: check actual body
        const cloned = response.clone();
        const text = await cloned.text();
        if (!text.trim()) {
            throw new Error("Server returned an empty response (via body)");
        }
    }
}

🧠 Environment Info

You can retrieve most of this from the /version endpoint.