React Router's fetcher fails to upload some images on Safari

[jmho]

I'm using React Router as a...

framework

Reproduction

1. Open up the following StackBlitz in Safari and Chrome
2. Download the following zip containing png images here
3. Extract the untitled folder from the zip file.
4. Upload any of the two images to the stackblitz instance opened in chrome and click submit.
5. Upload the same image as in step 4 to the stackblitz instance opened in safari and click submit.

Additional note:

• These .png images were created using the MacOS Snipping tool.

System Info

Stack Blitz
  System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @react-router/dev: * => 7.1.5 
    @react-router/node: * => 7.1.5 
    @react-router/serve: * => 7.1.5 
    react-router: * => 7.1.5 
    vite: ^6.0.11 => 6.1.0 

Local
  System:
    OS: macOS 15.3
    CPU: (10) arm64 Apple M1 Pro
    Memory: 137.61 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.11.1 - ~/.nvm/versions/node/v20.11.1/bin/node
    npm: 10.2.4 - ~/.nvm/versions/node/v20.11.1/bin/npm
    pnpm: 9.12.3 - ~/.nvm/versions/node/v20.11.1/bin/pnpm
    bun: 1.1.0 - ~/.bun/bin/bun
  Browsers:
    Chrome: 132.0.6834.160
    Safari: 18.3
  npmPackages:
    @react-router/dev: ^7.1.4 => 7.1.4 
    @react-router/node: ^7.1.4 => 7.1.4 
    @react-router/serve: ^7.1.4 => 7.1.4 
    react-router: ^7.1.4 => 7.1.4 
    vite: ^5.4.11 => 5.4.14

Used Package Manager

npm

Expected Behavior

I expect both Safari and Chrome to have the same behavior when uploading images. The same behavior is defined as is_file rendering as true on the web page and the console.log(...) that fires on form submissions to output the same object.

Actual Behavior

Chrome successfully renders is_file as True and outputs the expected File object on fetcher submission.

Safari renders is_file as False and outputs an empty string on console.log(...) for fetcher submission.

Image of behavior attached: