Existing comments not displaying despite correct tinycomments_fetch implementation

[Alexandre-Pascal]

Hi,
I'm encountering an issue with TinyMCE Comments where previously created comments are not being displayed when loading the editor, even though:

1. New comments work perfectly (they appear when created)
2. The API returns data in the exact format specified in the documentation
3. Console logs show the correct data structure being returned
   Here's my implementation:

type tinycomments_fetch = {
    conversations: {
        [conversationUid: string]: {
            uid: string,
            comments: [
                {
                    uid: string,
                    author: string,
                    authorName?: string,
                    authorAvatar?: string,
                    content: string,
                    createdAt: string,
                    modifiedAt: string
                }
            ]
        }
    }
}

// In TinyMCE config:
tinycomments_fetch: (conversationUids: string[], done: (data: tinycomments_fetch) => void, fail: Function) => {
    fetch(`/api/comments/conversations`, {
        method: 'GET',
        headers: { 'Content-Type': 'application/json' }
    })
        .then(response => response.json())
        .then((data: tinycomments_fetch) => {
            console.log('All conversations:', data);
            done(data);
        })
        .catch(err => fail(err));
}

I also tried initializing comments in the setup function

Expected behavior:

• When loading the editor, previously created comments should be visible
• Comment markers should be present in the content where comments were added

Actual behavior:

• Previously created comments are not displayed
• No comment markers visible in content
• New comments work correctly

Environment:
TinyMCE version: 5.1.1
Framework: Next.js 15
Comment: Callback mode