Intermittent “Unable to Connect to Data Plane” Errors Due to VPN Connectivity

Last updated: December 30, 2025

This issue is applicable to customers matching these conditions

Plans: Enterprise

Deployments: Hybrid

Use case: Accessing Braintrust UI with data plane hosted on private/internal network domain

Issue

Users may intermittently see the following error when accessing Braintrust in the UI or when running Braintrust-related scripts:

Your browser is unable to connect to the data plane at <custom-domain> 
Please check your internet connection or VPN (if applicable), and reach out to your Braintrust administrator if you are still having issues.

The error may appear sporadically, resolve temporarily, and then reoccur. It can affect both browser access (e.g., Safari, Chrome) and programmatic access (scripts, CLI, SDKs).

Cause

This issue is commonly caused by an unstable or degraded VPN connection.

In hybrid or self-hosted Braintrust deployments, access to the Braintrust data plane depends on a reliable VPN connection to internal network resources. If the VPN connection is:

  • Dropping packets

  • Reconnecting intermittently

  • Experiencing high latency

  • Switching networks (e.g., Wi-Fi ↔ wired, sleep/wake cycles)

then requests to the Braintrust data plane may fail intermittently, resulting in connection errors.

Unlike browser-specific issues (such as Chrome local network access restrictions), this scenario is not browser-dependent and can occur across browsers and scripts alike.

Resolution

  1. Verify VPN stability

    • Disconnect and reconnect to the VPN.

    • Confirm the VPN shows a healthy, connected state.

    • If possible, test from a stable network (avoid public or weak Wi-Fi).

  2. Restart affected processes

    • Fully reload the Braintrust UI after reconnecting to the VPN.

    • Restart any scripts, terminals, or development environments that were running during the VPN disruption.

  3. Check for recurring VPN issues

    • If the problem continues, consult your internal IT or networking team to investigate VPN reliability, routing, or firewall behavior.

  4. Rule out browser-specific issues