Hello all :) I have spent most of today trying to reply to my own comment by making my own AP implementation using node.js.

This is the Note I am trying to reply to: https://social.bvoigtlaender.de/@bjarne/statuses/01KDP1FQNJTTZGB3Q3BMD1JRMX

For that I am sending a POST to my Gts instance over at https://social.bvoigtlaender.de/users/bjarne/inbox with the following body:

{  
    "@context": [  
        "https://www.w3.org/ns/activitystreams"  
    ],  
    "actor": "https://fb2-01.bvoigtlaender.de/users/marty_mcfly34",  
    "cc": [  
        "https://www.w3.org/ns/activitystreams#Public",  
        "https://social.bvoigtlaender.de/users/bjarne"  
    ],  
    "id": "https://fb2-01.bvoigtlaender.de/posts/33135fdf-2fd6-4977-94e8-051ce44199fe/activity#Create",  
    "type": "Create",  
    "published": "2025-12-29T22:02:13.423Z",  
    "to": "https://fb2-01.bvoigtlaender.de/users/marty_mcfly34/followers",  
    "object": {  
        "attachment": [],  
        "id": "https://fb2-01.bvoigtlaender.de/posts/33135fdf-2fd6-4977-94e8-051ce44199fe",  
        "actor": "https://fb2-01.bvoigtlaender.de/users/marty_mcfly34",  
        "type": "Note",  
        "cc": [  
            "https://www.w3.org/ns/activitystreams#Public",  
            "https://social.bvoigtlaender.de/users/bjarne"  
        ],  
        "published": "2025-12-29T22:02:13.423Z",  
        "url": "https://fb2-01.bvoigtlaender.de/posts/33135fdf-2fd6-4977-94e8-051ce44199fe",  
        "attributedTo": "https://fb2-01.bvoigtlaender.de/users/marty_mcfly34",  
        "inReplyTo": "https://social.bvoigtlaender.de/users/bjarne/statuses/01KDP1FQNJTTZGB3Q3BMD1JRMX",  
        "content": "<p>Hello from FediBB</p>",  
        "to": "https://fb2-01.bvoigtlaender.de/users/marty_mcfly34/followers"  
    }  
}  

The signature works and GtS is not reporting any errors. Instead it fetches /followers /following /outbox and creates the user on its local db. However the reply will not be created and it only shows up after I fetch it manually using its id. Then it also gets linked the original post correctly. I am not sure what I am doing wrong.

What AP implementations do you normally test against?