[Problem/Bug]: No Kanji conversion

[suzuki-s0329]

What happened?

What happened?

After updating Microsoft Edge WebView2 Runtime to version
151.0.4129.59 (x64), Japanese text can no longer be converted
to Kanji when using Japanist 10 IME.

The issue did not occur before updating to WebView2 Runtime 151.

Repro Steps

1. Install Microsoft Edge WebView2 Runtime 151.0.4129.59 (x64).
2. Launch an application that uses WebView2.
3. Switch input method to Japanist 10.
4. Enter Japanese text.
5. Attempt Kanji conversion.

Expected behavior

Japanese text should be converted normally using Japanist 10.

Actual behavior

Conversion candidates do not appear, or Kanji conversion does not work properly.

Runtime Version

151.0.4129.59

Operating System

Windows 11 24H2
(26100.8875)

IME

Japanist 10

Additional notes

• Reproducible on multiple WebView2-based applications.
• The problem started immediately after updating to Runtime 151.
• Rolling back to the previous Runtime version resolves the issue.
• Microsoft IME does not show this problem. (If applicable)

Importance

Blocking. My app's basic functions are not working due to this issue.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

No response

SDK Version

No response

Framework

Win32

Operating System

Windows 11

OS Version

26100.8875

Repro steps

After updating to Microsoft Edge WebView2 Runtime 151.0.4129.59 (x64), Japanese Kanji conversion no longer works when using Japanist 10.

The issue occurs in Outlook (both the new and classic versions), Microsoft Teams, and other applications that use WebView2. Microsoft Edge itself has already been unable to perform Kanji conversion with Japanist 10.

Rolling back WebView2 Runtime to the 150.x version resolves the issue in WebView2-based applications. However, Microsoft Edge continues to have the same problem even after the rollback.

Environment:

• WebView2 Runtime: 151.0.4129.59 (x64)
• IME: Japanist 10

Expected behavior:
Japanese text should be converted to Kanji normally when using Japanist 10.

Actual behavior:
Kanji conversion does not work when entering Japanese text with Japanist 10.

This appears to be a regression introduced in WebView2 Runtime 151, as the problem does not occur with Runtime 150.x.

Repros in Edge Browser

Yes, issue can be reproduced in the corresponding Edge version

Regression

Regression in newer Runtime

Last working version (if regression)

No response

[ambikakunnath]

suzuki-s0329 , can you kindly help with steps to install Japanist 10 IME? Given this doesn't reproduce with Microsoft IME, would like to know where this is installed from.
Can you also confirm the following:

1. Does the issue repro in Chrome?
2. Does the issue repro in Notepad or is isolated to Edge and WebView2?