I realised my mistake.
All of the parts in TestModel2 are welded via a Weld Constraint to Part1. I’m assuming therefore, that TestModel is forced to also be Persistant as one of the parts inside it is Welded to parts that are in a Persistant model. Without Weld Constraints it worked as intended, which would explain why you couldn’t replicate it. That being said, does it really need to keep the entire model in rather than just the part its welded to?
If Part1 is welded to something in the persistent model then I would expect Part1 to behave persistently, but Part2 and Part3 should still stream in and out independently if they aren’t linked in any way with the persistent model.
@CorvusCoraxx @Khanovich @tnavarts
BugWhen streaming, other Player Characters in workspace which have limbs that utilize IK Control, sometimes have those limbs disappear entirely on the client viewing them.
The limbs and IK Control are intact on the server and there is no complications or issues there.
I only seemed to resolve this by making all characters Persistent with a script as they spawn in. But as you may understand this bug is a big setback to optimization.
This issue forces a developer to choose between glitches and character parts disappearing on the client vs optimization and allowing characters to stream out. vs Not using IC Controls at all.
(Which I am sure is not the intended behavior)
-The Target is changed repeatedly on the server when reaching for specific objects. But this is the intended use of the property to my knowledge.
-The Weight and Smoothing is updated as well depending on the object that the target is changed to.
-I was unable to pinpoint the exact cause of this issue. But I learned that anchoring the parts causes them to appear on the client viewing them again. This information might be useful or relevant.
-Disabling the IK Control or any of its properties does not reverse the behavior.
If you are already aware of this bug, or if this will be worked on, please reply as soon as you can.
Thank you. 
Are you able to file a bug report on this issue? I’m not aware of any problems similar to what you describe. Having a bug report with an attached repro place would be helpful.
There seems to be a bug where having a character set to Atomic completely breaks respawning after resetting. Here’s a Repro Place (41.8 KB) of the bug. If you reset in the place provided it will break your character (the limbs) but you will not respawn (It occasionally works, but 90% of the time it doesn’t). I have a script in ServerScriptService that sets the character to atomic on CharacterAdded
If it works the first time, the animations will not work which is a bug that has been reported previously. However, if you reset again the character will not respawn
I can try to make a repo place, but it’s something I noticed in a large game, and I only noticed the behavior in other players.
The behavior seemed to be tied into streaming somehow, but I never figured out exactly how, as I was more concerned with making the game functional.
It may take a while to try and make a repro place and find people willing to help me figure it out.
I will submit a bug report if I have any luck.
Thanks, we are aware of this issue and have developed a fix. We are hoping to release it in the next couple weeks.
Was this fix ever implemented? Now I’m worried about the chance for PrimaryPart to not be already set when an atomic model streams in.
The issue with PrimaryPart not being set when an atomic model is streamed in has been fixed.
Is there an update on when this fix will be enabled? My team switched all our code to use atomic streaming mode a while ago for characters (when the bug wasn’t happening) and this is causing quite a few bugs within our game
The fix for respawning should be enabled this week. I will post when it is fully active.
Will there ever be support for locally created attributes and collection tags for streamed parts? It is pretty crucial in my case and makes the transition really difficult.
Edit: Not as difficult as I thought. For non-atomic models only descendants are streamed out, the solution is to store attributes/tags directly in models
Edit2: I’ve got another question. Shouldn’t atomic and non-atomic models also be streamed out when descendant of ReplicatedStorage or ReplicatedFirst? Let’s say I have buildings under workspace and keep their interiors in a replicated storage. Each time player walks in, a proper one is parented to workspace from a localscript.
Will there ever be a function that allows us to manually unload things via streaming?
We have RequestStreamAroundAsync() why cant we have a function to also forcibly unload it?
The reason i need thiss is because my map is quite small to roblox scale. My streamingminradius is 64 and target radius is around 128~ studs. Since i use a custom unrendering system alongside streaming it would be amazing to be able to unload it via a function which also fully removes it from the clients memory.
There is a related issue to having a character as an atomic model. The content of a StarterGui doesn’t replicate to a PlayerGui when a character spawns.
A fix for this issue has been developed and should be rolled out in a few weeks.
Would it be possible to add a new streaming property to set a model to never stream in? This would allow developers to have more control over what they want to stream in? Something like persistent, but the other way around.
Fixes for all known issues related to atomic characters have been enabled. These include fixes for:
If you are still seeing problems with atomic character models please file a bug report if possible. Thank you to those who reported these issues in the past.
Do you have some news about selective replication ?
Did you ever find a fix for this issue? We’re currently having very similar problems with servers crashing due to memory, and it’s making the game unplayable with servers only lasting 30-45 minutes. Unfortunately many players can’t even load in without streaming enabled so we are stuck on what to do.