UseGlobalCustomSerializer doesn't appear to work

[maxkratt]

UseGlobalCustomSerializer doesn't appear to work

• Unity version:
  6000.3.0f1

• FishNet Version:
  4.6.19

• Discord Troubleshot Link/What I've tried:
  https://discord.com/channels/424284635074134018/1460289147674693704/1460289147674693704

• Description:
  Placing a custom serializer in it's own assembly definition prevents FishNet from finding it. Even when the class it's for has been given the UseGlobalCustomSerializer attribute.

• Replication:
  Download and import example. See errors.

• Example:
  SerializerInDifferentAssembly.zip

[FirstGearGames]

This has probably already been realized: as a work-around the user can put the serializer in the same assembly as the using type.

[Virus-vr]

This has probably already been realized: as a work-around the user can put the serializer in the same assembly as the using type.

Thank you for taking a look at this issue.
I have the serialisier and the using type in the same assembly. That's the set up I tried where I got the errors I showed in the screenshot.

[maxkratt]

@Virus-vr , I've tested having the serializer in the same assembly as the using type and that works fine. If that part is causing trouble on your end, then could you create an example project showing that failing please? You can post it in the Discord link, since it's different from this exact issue.

[FirstGearGames]

I don't see any issues here.

There's no test code trying the RPC, but I can see via the logs it's recognizing the custom serializer.

Registering type SomeClass. IsGenerated? False

When IsGenerated is false the serializer is set as custom, and it cannot be overwritten.

        public static void SetWrite(Action<Writer, T> value)
        {
            /* If a custom serializer has already been set then exit method
             * to not overwrite serializer. */
            if (HasCustomSerializer)
                return;

            bool isGenerated = value.Method.Name.StartsWith(UtilityConstants.GeneratedWriterPrefix);

            Debug.Log($"Registering type {typeof(T).Name}. IsGenerated? {isGenerated}");
            
            // If not generated then unset any generated delta serializer.
            if (!isGenerated && GenericDeltaWriter<T>.HasCustomSerializer)
                GenericDeltaWriter<T>.Write = null;

            // Set has custom serializer if value being used is not a generated method.
            HasCustomSerializer = !isGenerated;
            Write = value;
        }

[Virus-vr]

Sorry I responded on discord and forgot to put my response here as well.
My setup was actually the same issue as the example. I misunderstood the wording, which made me wrongly think I had a different issue.
The alternative that I ended up using was provided by TenousTV main...Tenous-TV:FishNet:main
So for me that works as a solution.

[maxkratt]

I tried importing the project and adding the UseGlobalCustomSerializer attribute to the SomeClass class, but these errors are shown.

[FirstGearGames]

That's the Sprite, it cannot be serialized.

…

On Fri, Feb 13, 2026, 5:46 AM Max Kratt ***@***.***> wrote: *maxkratt* left a comment (FirstGearGames/FishNet#998) <#998 (comment)> I tried importing the project and adding the UseGlobalCustomSerializer attribute to the SomeClass class, but these errors are shown. image.png (view on web) <https://github.com/user-attachments/assets/be503175-f6e8-481d-9e1f-20bcf9f97619> — Reply to this email directly, view it on GitHub <#998 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGPJC3TG4MUW43DXDICGSQL4LWTOTAVCNFSM6AAAAACR5OWWEWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOJWGQ4TIMZWGA> . You are receiving this because you commented.Message ID: ***@***.***>

[maxkratt]

Maybe I'm misunderstanding it then. From my understanding, the custom serializer doesn't serialize the Sprite, so if the custom one is used then it shouldn't have any errors, but if FishNet were trying to use an automatic serializer then it would attempt to serialize the Sprite and cause the errors.

[FirstGearGames]

Ah, I see. Unity prevents xodefne from seeing across assemblies, so FN has no way of knowing if a custom serializer even exists, so a standard serializer is generated. Even if a type is only in a single assembly it's more trouble than it's worth to try and determine that, since we cannot see across assemblies anyway. So when the standard serializer is made it tries to serialize the Sprite and the error is shown. There's an attribute which can be added over the member to prevent the error, CodegenExclude perhaps; wording may vary slightly.

…

On Sat, Feb 14, 2026, 12:48 AM Max Kratt ***@***.***> wrote: *maxkratt* left a comment (FirstGearGames/FishNet#998) <#998 (comment)> Maybe I'm misunderstanding it then. From my understanding, the custom serializer doesn't serialize the Sprite, so if the custom one is used then it shouldn't have any errors, but if FishNet were trying to use an automatic serializer then it would attempt to serialize the Sprite and cause the errors. — Reply to this email directly, view it on GitHub <#998 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGPJC3W4ZK36B6TWPS5XGLL4L2ZKRAVCNFSM6AAAAACR5OWWEWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTSMBRGE3TGMBXHA> . You are receiving this because you commented.Message ID: ***@***.***>

[maxkratt]

Ah ok, I understand it better now. What's the benefit of the UseGlobalCustomSerializer attribute then though?