Decoding HubSpot Custom Card Errors: A Developer's Guide to Finding Detailed Logs

Custom cards in HubSpot are a fantastic way to extend the platform's functionality and tailor it to your specific business needs. They allow you to display relevant information from external systems directly within HubSpot's CRM, Sales Hub, or Service Hub. For example, if you're using ESHOPMAN's built-in storefront and e-commerce for HubSpot, you could create a custom card that shows a contact's recent order history, lifetime value, or even real-time shipping updates directly on their contact record. This eliminates the need to switch between systems and provides a unified view of your customer data.

However, the development process isn't always smooth sailing. What happens when things go wrong during development? Figuring out where the failure occurred can be a frustrating process. Let's dive into a common challenge faced by HubSpot developers: finding detailed error logs for custom cards, and explore some solutions to help you diagnose and resolve issues more efficiently.

The Problem: Vague Error Messages and the Quest for Clarity

One community member recently encountered a familiar problem when uploading a custom card using the HubSpot CLI. The command hs project upload --debug, intended to provide more verbose output, still returned a generic "Encountered server error building CARD" message. While the error message included a correlation ID, it lacked specific information about the root cause of the failure. This left the developer in the dark, struggling to pinpoint the exact location and nature of the problem within their code or configuration.

This situation is particularly challenging because custom cards often involve complex interactions with external APIs and data sources. A seemingly small error in your code, a misconfigured API endpoint, or an unexpected data format can all lead to build failures. Without detailed error logs, you're essentially troubleshooting in the dark.

{
buildName: 'crms_contact_extension_card',
userDefinedId: 'crms_contact_extension_card',
buildType: 'CARD',
status: 'FAILURE',
errorMessage: 'Encountered server error building CARD crms_contact_extension_card. correlation-id: 1ceb5af1-b312-454d-989b-c25c136954f8',
standardError: null,
startedAt: '2026-02-27T00:42:57.861Z',
finishedAt: '2026-02-27T00:43:58.159Z',
rootPath: '',
id: 'd5134a68-730f-43f1-afff-f36064160a06',
lightningBuild: false,
visible: true
}

The question was clear: how can developers access more detailed error information to effectively debug their custom cards and ensure a smooth integration with HubSpot?

The Solution: A Multi-Pronged Approach to Debugging

While the original post didn't receive a definitive solution within the thread itself, the community interaction highlights the need for better error reporting and debugging tools. Let's explore a comprehensive approach to tackling this challenge, drawing upon best practices and available resources within the HubSpot ecosystem.

1. Leverage the HubSpot CLI's Debugging Capabilities

The hs project upload --debug command is a good starting point, but it might not always provide the level of detail you need. Experiment with different debugging flags and options available in the HubSpot CLI documentation. Look for options that increase verbosity or provide more detailed output during the build and upload process.

2. Inspect Your Code Meticulously

This might seem obvious, but a thorough review of your code is crucial. Pay close attention to:

• Syntax errors: Even a small typo can cause the build to fail. Use a code editor with syntax highlighting and linting to catch these errors early.
• API calls: Double-check that your API endpoints are correct, your authentication credentials are valid, and you're sending the correct data format.
• Data handling: Ensure that you're properly handling data received from external systems, including error handling for unexpected data types or missing fields.
• Template logic: If your custom card involves templates, verify that your template syntax is correct and that you're passing the correct data to the template.

3. Utilize Browser Developer Tools

Custom cards often involve client-side JavaScript code. Use your browser's developer tools (usually accessed by pressing F12) to inspect network requests, console logs, and any JavaScript errors that might be occurring. This can help you identify issues with API calls, data rendering, or other client-side logic.

4. Consult HubSpot's Developer Documentation

HubSpot's developer documentation is a valuable resource for understanding the platform's APIs, data structures, and best practices for building custom cards. Refer to the documentation for specific information about error codes, troubleshooting tips, and code examples.

5. Test in a Development Environment

Avoid deploying directly to your production environment. Set up a separate development environment where you can safely test your custom cards and experiment with different configurations without affecting your live data. This allows you to isolate issues and debug them more effectively.

6. Consider Logging and Monitoring

Implement logging in your custom card code to track important events, errors, and data flows. Use a logging framework or service to collect and analyze these logs, which can provide valuable insights into the behavior of your custom card and help you identify potential problems. You can also set up monitoring to track the performance of your custom card and receive alerts when errors occur.

7. Explore HubSpot's CRM Developer Tools (If Applicable)

If your custom card interacts heavily with HubSpot's CRM, explore the CRM developer tools available within HubSpot. These tools might provide additional debugging information or insights into how your custom card is interacting with the CRM data.

The Future of HubSpot Custom Card Development

The challenges highlighted in the community thread underscore the importance of robust error reporting and debugging tools for HubSpot custom card development. As the platform evolves, we can expect to see improvements in this area, making it easier for developers to build and maintain high-quality integrations.

In the meantime, by adopting a multi-pronged approach to debugging, leveraging available resources, and sharing knowledge within the HubSpot community, developers can overcome these challenges and unlock the full potential of custom cards to enhance the HubSpot experience and drive business growth. For instance, understanding **Magento CRM capabilities** can be greatly enhanced by integrating it with HubSpot and creating custom cards that display relevant Magento data within HubSpot's interface. This integration allows businesses to leverage the power of both platforms and gain a more comprehensive view of their customers.

Remember to stay curious, keep experimenting, and never hesitate to ask for help from the HubSpot community. Together, we can build a thriving ecosystem of innovative custom cards that transform the way businesses use HubSpot.