bug: TS2320: Interface 'HTMLIonInputElement' cannot simultaneously extend types 'IonInput' and 'HTMLStencilElement'

[emeryao]

Prerequisites

• I have read the Contributing Guidelines.
• I agree to follow the Code of Conduct.
• I have searched for existing issues that already report this problem, without success.

Ionic Framework Version

v8.x

Current Behavior

since angular 20.2.0 released recently and typescript v5.9 is being supported

I upgraded dependencies of my project and the message pop up when serving the project

X [ERROR] TS2320: Interface 'HTMLIonInputElement' cannot simultaneously extend types 'IonInput' and 'HTMLStencilElement'.
  Named property 'autocorrect' of types 'IonInput' and 'HTMLStencilElement' are not identical. [plugin angular-compiler]

    node_modules/@ionic/core/dist/types/components.d.ts:4326:14:
      4326 │     interface HTMLIonInputElement extends Components.IonInput, H...

X [ERROR] TS2320: Interface 'HTMLIonSearchbarElement' cannot simultaneously extend types 'IonSearchbar' and 'HTMLStencilElement'.
  Named property 'autocorrect' of types 'IonSearchbar' and 'HTMLStencilElement' are not identical. [plugin angular-compiler]

    node_modules/@ionic/core/dist/types/components.d.ts:4888:14:
      4888 │     interface HTMLIonSearchbarElement extends Components.IonSear...

and my project went well with angular@v20.1.* and typescript@v5.8.*

Expected Behavior

Success to build and serve

Steps to Reproduce

1. update deps with angular@v20.2.0 and typescript@v5.9.2
2. try to serve with npx ng serve

Ionic Info

Ionic:

Ionic CLI : 7.2.1 (C:\Users\USER\AppData\Local\npm-cache_npx\f6fddb685269761d\node_modules@ionic\cli)
Ionic Framework : @ionic/angular 8.7.2
@angular-devkit/build-angular : not installed
@angular-devkit/schematics : 20.2.0
@angular/cli : 20.2.0
@ionic/angular-toolkit : not installed

Capacitor:

Capacitor CLI : 7.4.2
@capacitor/android : 7.4.2
@capacitor/core : 7.4.2
@capacitor/ios : not installed

Utility:

cordova-res : not installed globally
native-run : 2.0.1

System:

NodeJS : v24.6.0 (C:\Program Files\nodejs\node.exe)
npm : 11.5.2
OS : Windows 10

---

Sorry for my poor English 😆

[IAM5K]

Facing same issue in new app.

{
  "dependencies": {
    "@angular/animations": "^20.0.0",
    "@angular/common": "^20.0.0",
    "@angular/compiler": "^20.0.0",
    "@angular/core": "^20.0.0",
    "@angular/forms": "^20.0.0",
    "@angular/platform-browser": "^20.0.0",
    "@angular/platform-browser-dynamic": "^20.0.0",
    "@angular/router": "^20.0.0",
    "@angular/service-worker": "^20.0.0",
    "@capacitor/android": "7.4.3",
    "@capacitor/app": "7.0.2",
    "@capacitor/core": "7.4.3",
    "@capacitor/haptics": "7.0.2",
    "@capacitor/ios": "7.4.3",
    "@capacitor/keyboard": "7.0.2",
    "@capacitor/status-bar": "7.0.2",
    "@ionic/angular": "^8.0.0",
    "firebase-tools": "^14.14.0",
    "ionicons": "^7.0.0",
    "rxjs": "~7.8.0",
    "tslib": "^2.3.0",
    "zone.js": "~0.15.0"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^20.0.0",
    "@angular-eslint/builder": "^20.0.0",
    "@angular-eslint/eslint-plugin": "^20.0.0",
    "@angular-eslint/eslint-plugin-template": "^20.0.0",
    "@angular-eslint/schematics": "^20.0.0",
    "@angular-eslint/template-parser": "^20.0.0",
    "@angular/cli": "^20.0.0",
    "@angular/compiler-cli": "^20.0.0",
    "@angular/language-service": "^20.0.0",
    "@capacitor/cli": "7.4.3",
    "@ionic/angular-toolkit": "^12.0.0",
    "@types/jasmine": "~5.1.0",
    "@typescript-eslint/eslint-plugin": "^8.18.0",
    "@typescript-eslint/parser": "^8.18.0",
    "eslint": "^9.16.0",
    "eslint-plugin-import": "^2.29.1",
    "eslint-plugin-jsdoc": "^48.2.1",
    "eslint-plugin-prefer-arrow": "1.2.3",
    "jasmine-core": "5.9.0",
    "jasmine-spec-reporter": "~5.0.0",
    "karma": "~6.4.0",
    "karma-chrome-launcher": "~3.2.0",
    "karma-coverage": "~2.2.0",
    "karma-jasmine": "~5.1.0",
    "karma-jasmine-html-reporter": "~2.1.0",
    "typescript": "5.9.2"
  },
}

Hope we get fix soon.
Message for the testing team, atleast test once before release.

[loganmurray-infor]

FYI you can force a build by adding "skipLibCheck": true to your tsconfig.json's compilerOptions, but also hoping this gets resolved soon.

[pedrodominguesp]

Facing same issue in new app

[davidsarkany]

FYI you can force a build by adding "skipLibCheck": false to your tsconfig.json's compilerOptions, but also hoping this gets resolved soon.

You need to add "skipLibCheck": true

[loganmurray-infor]

You need to add "skipLibCheck": true

Whoops, corrected.

[brandyscarney]

Thanks for the issue!

You should be able to work around this by downgrading TypeScript:

npm i typescript@5.8.3 --save-exact

[brysonreese]

Confirmed downgrade to typescript@5.8.3 worked in my case. Thank you much!

[SoraNoIseki]

This fixed the issue for me, works fine with TypeScript@5.8.3 too. Thanks!

[brandyscarney]

Hi everyone! I wanted to share an update on why this issue is happening, what needs to be done to resolve it, and what we recommend in the meantime.

Why this is happening

TypeScript 5.9 introduced a new property, HTMLElement.autocorrect, defined as a boolean. This conflicts with Stencil's existing autocorrect type, which follows the global autocorrect and is defined as a string.

Why this only affects Angular (not React or Vue)

Angular is currently the only framework that doesn't use skipLibCheck in its tsconfig.json in both our starters and our docs examples. React and Vue are not running into this because their configs already include skipLibCheck. I'll be updating the Angular starters and docs to include this as well.

What we are doing to fix it

The permanent fix needs to happen in Stencil. We've created an internal task to upgrade Stencil for TypeScript 5.9 support. We don't have an ETA until work begins, but once complete, we'll update Stencil in Ionic Framework and resolve this issue.

What we recommend in the meantime

If you want to use TypeScript 5.9, add the following to your tsconfig.json:

"compilerOptions": {
  "skipLibCheck": true,
},

If you want to pin TypeScript to the last version that works, you can install it with:

npm i typescript@5.8.3 --save-exact

We will update this issue once there is a permanent fix. Thank you!