Android system font scaling has no effect on certain cases

Description

On Android, system font scaling values between 1.0 to 1.5 aren't applied properly on certain font sizes. Please see the screenshots below.

Steps to reproduce

Android

1. Install the app
2. Use adb shell settings put system font_scale x.x to set font scaling value or change it through setting
3. Make sure to restart the app after changing the value

iOS

1. Install the app
2. Use simulator settings or the settings app to change the font scaling value
3. Make sure to restart the app after changing the value

React Native Version

0.85.3

Affected Platforms

Runtime - Android

Output of npx @react-native-community/cli info

info Fetching system and libraries information...
System:
  OS: macOS 15.7.7
  CPU: (12) arm64 Apple M4 Pro
  Memory: 559.30 MB / 48.00 GB
  Shell:
    version: 0.109.1
    path: /Users/burakguner/.cargo/bin/nu
Binaries:
  Node:
    version: 24.13.0
    path: /Users/burakguner/.nix-profile/bin/node
  Yarn:
    version: 1.22.22
    path: /Users/burakguner/.nix-profile/bin/yarn
  npm:
    version: 11.6.2
    path: /Users/burakguner/.nix-profile/bin/npm
  Watchman:
    version: 2026.01.19.00
    path: /Users/burakguner/.nix-profile/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/burakguner/.local/share/gem/ruby/3.3.0/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK:
    API Levels:
      - "30"
      - "31"
      - "34"
      - "35"
      - "36"
    Build Tools:
      - 35.0.0
      - 36.0.0
      - 36.1.0
    System Images:
      - android-30 | ARM 64 v8a
      - android-34 | Google Play ARM 64 v8a
      - android-35 | Google APIs ARM 64 v8a
      - android-35 | Google Play ARM 64 v8a
      - android-36.1 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.3 AI-253.32098.37.2534.15336583
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 21.0.8
    path: /Users/burakguner/.nix-profile/bin/javac
  Ruby:
    version: 3.4.8
    path: /Users/burakguner/.nix-profile/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.1.0
    wanted: 20.1.0
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.85.3
    wanted: 0.85.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

N/A

MANDATORY Reproducer

https://github.com/atlj/reproducer-android-broken-font-scaling

Screenshots and Videos

Android

All of these screenshots were taken with an Android 16 emulator. However the issue is reproducible on Android 13, Android 14 and Android 15 as well.

What to look for

In the following screenshots, notice how text with font size 30 isn't scaled properly between font scale 1 to 1.5 (except 1.01 which might be useful to spot the exact bug)

1	1.01	1.1	1.2	1.3	1.5	1.6	2

A non React Native App

Here is how the settings app behaves

1.0	1.01	1.1	1.2	1.6

iOS

iOS applies font scaling properly

Bắt đầu với reproducer bắt buộc tại github.com/atlj/reproducer-android-broken-font-scaling và tái hiện vấn đề trên Android bằng các giá trị font_scale được liệt kê, đặc biệt là 1.0–1.5. So sánh hành vi của Android với iOS và ứng dụng Settings không dùng React Native. Được xem là hoàn tất khi các kích thước phông chữ bị ảnh hưởng được chia tỷ lệ chính xác trên các phiên bản Android đã được báo cáo và hành vi hiện có vẫn được giữ nguyên.