DialogBody + ItemStack as item crashes server

Stack trace

https://pastes.dev/PgMViG4EXH

Plugin and Datapack List

[16:44:53 INFO]: ℹ Server Plugins (1):
[16:44:53 INFO]: Paper Plugins:
[16:44:53 INFO]: - VanillaPlus

[16:44:30 INFO]: There are 3 data pack(s) enabled: [vanilla (built-in)], [file/bukkit (world)], [paper (built-in)]
[16:44:30 INFO]: There are no more data packs available

Actions to reproduce (if known)

@Override
    public void bootstrap(BootstrapContext context) {
        context.getLifecycleManager().registerEventHandler(RegistryEvents.DIALOG.compose()
            .newHandler(event -> event.registry().register(
                DialogKeys.create(Key.key("papermc:custom_dialog")),
                builder -> builder
                    .base(DialogBase
                        .builder(Component.text("Title"))
                        .body(DialogBody.item(ItemStack.of(Material.PAPER).setData(DataComponentTypes.CUSTOM_NAME, Component.text("TEST"))))
                        .build())
                    .type(DialogType.notice())
            )));
    }

Paper version

[16:44:19 INFO]: Checking version, please wait...
[16:44:19 INFO]: This server is running Paper version 1.21.11-92-main@e7445e1 (2026-01-11T23:38:04Z) (Implementing API version 1.21.11-R0.1-SNAPSHOT)
You are running the latest version
Previous version: 1.21.11-46-8e5e54f (MC: 1.21.11)

Other

No response

Start with the linked stack trace and the bootstrap reproduction using DialogBody.item with an ItemStack carrying a custom name. Trace the dialog registration and item serialization path to identify the crash; done means this dialog registers without crashing the server, with a regression test if the relevant test area is found.