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Trace Tab Is not Visible In API Manager when testing an API

Troubleshooting


Problem

The Trace tab in API Manager is not showing up for a specific API, but works fine for other APIs.
Predefined is set to false in the API

Cause

The issue seems to be due to a CORS misconfiguration.
Specifically, the expose-headers.predefined setting is set to false,

Environment

The Trace tab in API Manager relies on specific headers (e.g., X-Global-Transaction-ID, X-Correlation-ID, etc.) being exposed in the response.
When expose-headers.predefined is set to false, these headers are not included in the CORS response, even if backend: true is enabled.
As a result, the API Manager UI cannot detect or display the Trace tab for that API.

Diagnosing The Problem

For comparison, here is the relevant CORS configuration when Trace Tab is visible

cors:
  enabled: true
  policy:
    - allow-credentials: true
      allow-origin:
        - https://example1.apim.mgmt.apic.castle.com
      expose-headers:
        predefined: true
        backend: true

And here is the configuration for when Trace Tab is NOT visible

cors:
  enabled: true
  policy:
    - allow-credentials: true
      allow-origin:
        - https://example1.apim.mgmt.apic.castle.com
      expose-headers:
        predefined: false
        backend: true

Resolving The Problem

Update the CORS configuration for the API to include predefined: true under expose-headers
Steps to Apply the Fix
  1. Log in to API Manager.
  2. Navigate to the respective API.
  3. Click on the Gateway tab.
  4. In the left-hand menu, select CORS.
  5. Under Allowed Origins, click the three dots next to the relevant hostname.
  6. Click Edit.
  7. Check the Predefined option under Expose Headers.
  8. Click Save.
Predefined is set to true

Related Information

Enabling CORS support for an API

Document Location

Worldwide

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Document Information

Modified date:
23 July 2025

UID

ibm17240163

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