declarativeNetRequest response-header modifications are not shown in DevTools (Manifest V3)

[Orest Kreminsky]

Hi,

I found the existing Chromium issue 40196848, which appears to describe this behavior. The issue was reported several years ago and currently appears to remain open.

Could someone confirm whether this issue still tracks the current DevTools behavior and whether there are any plans to address it?

We are developing a Manifest V3 header override extension that modifies request and response headers using chrome.declarativeNetRequest.

The dynamic rules are registered using:

const existingRules = await chrome.declarativeNetRequest.getDynamicRules(); await chrome.declarativeNetRequest.updateDynamicRules({ removeRuleIds: existingRules.map(rule => rule.id) }); await chrome.declarativeNetRequest.updateDynamicRules({ addRules: [rule] });

The rule is registered successfully, and the modified header is visible to JavaScript:

const response = await fetch("/some-resource"); console.log( response.headers.get("x-debug-mode") ); // "on"

However, the header does not appear under:

DevTools → Network → Headers → Response Headers

Could you please clarify:

1. Is Chromium issue 40196848 still the correct issue for this behavior?
2. Are there plans for DevTools to display headers added, changed, or removed by extensions?

Thank you.