Importing and applying MatInput somehow disables an extended diagnostic on an unrelated signal #63739

Which @angular/* package(s) are the source of the bug?

language-service

Is this a regression?

No

Description

Running ng new my-minimal-app --minimal for a simple setup I was quickly able to reproduce this issue.

before, extended diagnostic shows correctly:

after, added MatInput, and a text area with matInput directive somehow blows away the diagnostic on the other line:

Minimal repro attached.
my-minimal-app.zip

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 20.3.1
Node: 24.0.1
Package Manager: npm 11.5.2
OS: darwin arm64
    

Angular: 20.3.0
... common, compiler, compiler-cli, core, forms
... platform-browser, router

Package                      Version
------------------------------------
@angular-devkit/architect    0.2003.1
@angular-devkit/core         20.3.1
@angular-devkit/schematics   20.3.1
@angular/build               20.3.1
@angular/cli                 20.3.1
@angular/material            20.2.2
@schematics/angular          20.3.1
rxjs                         7.8.2
typescript                   5.9.2

Anything else?

No response