Help making AS3MXML LSP work in Panic Nova

[AmigaAbattoir]

Hello, I'm trying to make an extension for Panic's Nova and use this for an LSP. Out of the box, I got some functionality working, like issues, but could not get hovering to work. I noticed that Nova does not send a request textDocument/didOpen like VSCode does. But, when I try manually invoking I get it runs textDocument/publishDiagnostics on the files in the project, and then I get an error:

org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer fireError
SEVERE: Cannot invoke "java.util.concurrent.CompletableFuture.thenAccept(java.util.function.Consumer)" because "future" is null
java.lang.NullPointerException: Cannot invoke "java.util.concurrent.CompletableFuture.thenAccept(java.util.function.Consumer)" because "future" is null
org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleRequest(RemoteEndpoint.java:279)
org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:190)
org.eclipse.lsp4j.jsonrpc.TracingMessageConsumer.consume(TracingMessageConsumer.java:114)
org.eclipse.lsp4j.jsonrpc.validation.ReflectiveMessageValidator.consume(ReflectiveMessageValidator.java:68)
org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:194)
org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:94)
org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:113)
java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
java.base/java.lang.Thread.run(Thread.java:833)

I also get this on textDocument/didClose, textDocument/textChange. I was wondering if you had any suggestion on where to start digging into this.