Cache-Control header from layout routes not applied to child routes

[andrelandgraf]

What version of Remix are you using?

Was able to reproduce in 1.7.2, 1.13.0 and 1.16.1

Are all your remix dependencies & dev-dependencies using the same version?

• Yes

Steps to Reproduce

1. Add a "Cache-Control" header to a headers export in any layout route (root.tsx, __layout.tsx, dashboard.tsx)

// /dash.tsx layout route
export function headers() {
    return {
      "X-Cool": "Dash",
      "X-Dash": "Dash",
      "Cache-Control": "private, no-cache",
    }
  }

3. Open a nested route in a browser window
4. Inspect the Network tab
5. Notice that all but the "Cache-Control' headers of the layout route are applied

Expected Behavior

"Cache-Control" header is applied to every child route.

Actual Behavior

"Cache-Control" header is not applied, even if child routes do not add any headers. Custom headers are taken over in the child route (e.g., /dash/child) but not the "Cache-Control" header.

[andrelandgraf]

Logan and Ryan mentioned in Discord that this is a known issue and is actively being worked on: #6431

Closing!