getAuthorFeed with posts_and_author_threads filter incorrect behaviour with threads saved with same createdAt

[fogrye]

Describe the bug

Bsky client inserts threads using com.atproto.repo.applyWrites programatically computing cid and rkey. If thread is created at same time it works just fine because of only 1 call.

As third party service dev I rely on com.atproto.repo.createRecord to get correct uri and cid. Still I use same createdAt as time of bigger post from other service.

Thread is successfully created but available only with posts_with_replies filter for method app.bsky.feed.getAuthorFeed.

To Reproduce

Steps to reproduce the behavior:

1. exec

const agent = new AtpAgent({
   service: 'https://bsky.social',
});
// authorise

const date = new Date();
const {uri, cid} = await agent.post({
text: 'hello',
createdAt: date.toISOString()
})
await agent.post({
text: 'world',
reply: {root: {uri, cid}, parent: {uri, cid}},
createdAt: date.toISOString()
})

2. check in client app that thread missing in tab "Posts", only visible in "Replies"

Expected behavior

Thread should be visible in "Posts"