If you set nuxeo.server.sdk=true in 9.1 server configuration, on server start you'll get:

2017-05-15 15:39:00,891 ERROR [localhost-startStop-1] [org.nuxeo.runtime.tomcat.NuxeoLauncher] Failed to handle event: start java.lang.NoSuchMethodException: org.nuxeo.runtime.reload.ReloadService.installWebResources(java.io.File)

    at java.lang.Class.getDeclaredMethod(Class.java:2130)
    at org.nuxeo.runtime.tomcat.dev.ReloadServiceInvoker.<init>(ReloadServiceInvoker.java:69)
    at org.nuxeo.runtime.tomcat.dev.DevFrameworkBootstrap.start(DevFrameworkBootstrap.java:82)
    at org.nuxeo.runtime.tomcat.NuxeoLauncher.handleEvent(NuxeoLauncher.java:105)
    at org.nuxeo.runtime.tomcat.NuxeoLauncher.lifecycleEvent(NuxeoLauncher.java:83)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:394)
    at org.apache.catalina.util.LifecycleBase.setState(LifecycleBase.java:339)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5651)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:899)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:875)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:679)
    at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1966)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:748)

I guess this has to do with: https://jira.nuxeo.com/browse/NXP-21025

Basically I'm trying to figure out how hot reload works now that the Eclipse IDE is deprecated. Is the sdk mode still a thing in 9.1 or is there some other setting I need to enable in order to enable the hot reload? I have followed the instructions here https://www.npmjs.com/package/generator-nuxeo, but there's not much information about the server configuration.