bug: input-otp, backspace in an empty box only moves focus instead of clearing the previous box #31639

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

v9.x (9.0.8, same code on main)

Current Behavior

Happens on iOS (Safari and Capacitor app, on-screen keyboard), not every time. Not reproducible in desktop browsers.

Backspace in an empty box only moves focus to the previous box without clearing it. Since focus moves to the next empty box after each typed character, the first Backspace after typing can end up deleting nothing.

Typing into the now-focused, filled box then inserts the character and shifts the rest right instead of replacing it.

Expected Behavior

Per the docs:

• Backspace: "In an empty box: moves focus back one box and clears its value."
• Typing: "If the current box has a value, override the value with the entered character."

Steps to Reproduce

1. On an iPhone, in the Basic Usage demo, type 789 (focus is now on box 4)
2. Press Backspace: focus moves to box 3, 9 stays
3. Type 6: the result is 7869 instead of 786

May take a few tries; it does not happen on every attempt.

Code Reproduction URL

https://ionicframework.com/docs/api/input-otp#basic-usage

Ionic Info

@ionic/core 9.0.8, @ionic/angular 9.0.8, @angular/core 22.2.3, @capacitor/core 8.5.3

Additional Information

The empty-box branch of onKeyDown in core/src/components/input-otp/input-otp.tsx only calls this.focusPrevious(index). It should also clear inputValues[index - 1] and its input ref, call updateValue(event), and preventDefault(). The insert-and-shift branch of onInput contradicts the documented override behavior.