Japanese IME composition is broken on the first character in an empty Markdoc field

Japanese IME composition is broken on the first character in the rich text editor

Japanese IME input is broken when typing the first character into an empty Keystatic rich text editor.

This is not specific to fields.markdoc(), fields.mdx(), or entryLayout: "content".

I can reproduce the same behavior across the rich text editor itself.

For example, when trying to type:

にほんご

the editor produces:

ｎいほんご

The first n is committed separately instead of being included in the IME composition.

Steps to reproduce

1. Open an entry containing a Keystatic rich text field.
2. Focus an empty editor.
3. Enable a Japanese IME.
4. Type nihongo.

Expected:

にほんご

Actual:

ｎいほんご

Browser behavior

I can reproduce this in both:

• Google Chrome
• Mozilla Firefox

Additional findings

The issue is reproducible with different rich text field types, including:

• fields.markdoc()
• fields.mdx()

It also occurs regardless of whether entryLayout: "content" is used.

Because of this, the problem appears to be in the shared rich text editor implementation rather than in Markdoc, MDX, or the collection layout.

The problem seems to occur specifically when typing the first character into an empty editor.

Once the editor already contains text, Japanese IME input works normally.

Suspected behavior

It looks like the IME composition is interrupted immediately after the first romaji character is entered.

For example, while trying to type:

nihongo

the first:

n

is committed separately, and the remaining:

ihongo

continues as a new IME composition.

This suggests that the editor may be changing the DOM, selection, or editor state while the initial IME composition is active.

Additional information

I have a GIF showing the issue clearly and can attach it to this issue.

The issue is reproducible with Japanese IME input in both Chrome and Firefox.

Start with the shared rich text editor implementation, since the issue reproduces across Markdoc and MDX fields and entry layouts. Reproduce the first-character Japanese IME case in Chrome or Firefox, then verify that typing nihongo into an empty editor produces にほんご without interrupting composition.