Reported on Hacker News.

When inputting Japanese text in a Flutter Web app, we appear to be failing to capture the first character input in the composing region. See attached video for the (incorrect behaviour). I was able to repro on both macOS and Windows. Presumably this affects Linux as well.

Repro steps

1. Launch a Flutter Web app that includes a text field.
2. Switch to Japanese input hiragana mode (you should see an あ in the menu bar)
3. Type n-i-h-o-n-n.

Expected behaviour:
After each keypress you should see:

• n: n
• ni: に
• nih: にh
• niho: にほ
• nihon: にほn
• nihonn: にほん　(at this point you may get an auto-conversion to 日本, 2本, or other similar kanji conversion for 'nihon')

Actual behaviour:

• n: n
• ni: nい
• nih: nいh
• niho: nいほ
• nihon: nいほn
• nihonn: nいほん　(at this point you may get an auto-conversion to 伊ほん, 伊本 or other similar kanji conversion for 'ihon')

Notes

Verified on Windows, macOS, and Linux and this issue does not affect the desktop embedders, so appears to likely to be an issue in the web engine.