Windows System Proxy with a fixed proxy adds 20–30s delay per request, while manual proxy is fast

[luceat-lux-vestra]

I have checked the following:

• I have searched existing issues and found nothing that matches this exact behavior.

This bug is:

• making Bruno unusable for me
• slowing me down but I'm able to continue working
• annoying
• this feature was working in a previous version but is broken in the current release.

Bruno version

Current desktop version in use (exact version can be provided if needed).

Operating System

Windows (corporate environment)

Describe the bug

Bruno correctly detects and uses the Windows System Proxy, but requests are extremely slow when System Proxy mode is enabled.

The Windows proxy configuration is a fixed proxy, not a PAC URL/script.

Observed behavior:

• With System Proxy enabled in Bruno, requests succeed, but each request takes roughly 20–30 seconds before the response is returned.
• If I switch Bruno to Manual Proxy and enter the exact same proxy host and port, the same requests complete at normal speed.
• Other internet access and other applications using the same corporate proxy do not show this delay.

This makes the issue appear specific to Bruno's System Proxy handling path rather than the proxy server or target API itself.

Steps to reproduce

1. On Windows, configure a fixed corporate proxy at the OS level.
2. In Bruno, set Proxy mode to System Proxy.
3. Send a request to an external endpoint that requires the corporate proxy.
4. Observe that the request succeeds but takes approximately 20–30 seconds.
5. Change Bruno Proxy mode to On / Manual Proxy.
6. Configure the same proxy host and port that Windows is using.
7. Send the same request again.
8. Observe that the request completes at normal speed.

Expected behavior

Using System Proxy with a fixed Windows proxy should have approximately the same request latency as configuring the same proxy manually in Bruno.

Actual behavior

System Proxy mode adds approximately 20–30 seconds of latency per request, while Manual Proxy mode using the same proxy endpoint is fast.

Additional context

This appears different from existing proxy issues:

• Bruno does not recognize system proxy settings #4031: the System Proxy is not recognized there. In this case, the System Proxy is recognized and works, but is very slow.
• System Proxy (PAC) mode is ~2s slower per request due to myIpAddress() calling out to 8.8.8.8:53 #8576: PAC-specific ~2s delay caused by myIpAddress() / PAC evaluation. This setup does not use PAC; it uses a fixed Windows proxy.

I have not identified the root cause, so I am reporting only the observed A/B behavior.

Collection to reproduce

N/A. The behavior is network/proxy-configuration dependent rather than request-specific.

Screenshots/Live demo link

N/A