it works!

src/main/scala/Main.scala

@@ -1,3 +1,4 @@
+import cats.data.*
 import cats.effect.*
 import cats.effect.syntax.all.*
 import cats.syntax.all.*
@@ -9,8 +10,43 @@ import calico.html.io.{*, given}
 import calico.syntax.*
 import snow.*
 
+object Store {
+  def apply(window: Window[IO]): Resource[IO, Store] = {
+    val key = "nak-input"
+
+    for {
+      inputRef <- SignallingRef[IO].of("").toResource
+
+      _ <- Resource.eval {
+        OptionT(window.localStorage.getItem(key))
+          .foreachF(inputRef.set(_))
+      }
+
+      _ <- window.localStorage
+        .events(window)
+        .foreach {
+          case Storage.Event.Updated(`key`, _, value, _) =>
+            inputRef.set(value)
+          case _ => IO.unit
+        }
+        .compile
+        .drain
+        .background
+
+      _ <- inputRef.discrete
+        .foreach(input => IO.cede *> window.localStorage.setItem(key, input))
+        .compile
+        .drain
+        .background
+    } yield new Store(inputRef)
+  }
+}
+
+case class Store(input: SignallingRef[IO, String])
+
 object Main extends IOWebApp {
-  def render: Resource[IO, HtmlDivElement[IO]] = {
+  def render: Resource[IO, HtmlDivElement[IO]] = Store(window).flatMap {
+    store =>
       div(
         cls := "flex w-full h-full flex-col items-center justify-center",
         h1(cls := "px-1 py-2 text-lg", "nostr army knife"),
@@ -18,15 +54,12 @@ object Main extends IOWebApp {
           cls := "flex justify-center my-3"
           // button(cls := buttonCls, "generate event", onClick --> (_.foreach(_ => ))),
         ),
-      input()
+        input(store),
+        result(store)
       )
   }
 
-  def input(): Resource[IO, HtmlDivElement[IO]] =
-    SignallingRef[IO]
-      .of("")
-      .toResource
-      .flatMap { input =>
+  def input(store: Store): Resource[IO, HtmlDivElement[IO]] =
     div(
       cls := "w-full",
       div(
@@ -36,25 +69,22 @@ object Main extends IOWebApp {
             cls := "w-2/3 max-h-96 p-3",
             styleAttr := "min-height: 200px",
             placeholder := "paste something nostric",
-                onInput --> (_.foreach(_ => self.value.get.flatMap(input.set))),
-                value <-- input
+            onInput --> (_.foreach(_ =>
+              self.value.get.flatMap(store.input.set)
+            )),
+            value <-- store.input
           )
         }
       )
     )
-      }
 
-  def result(): Resource[IO, HtmlDivElement[IO]] =
-    SignallingRef[IO]
-      .of("")
-      .toResource
-      .flatMap { input =>
+  def result(store: Store): Resource[IO, HtmlDivElement[IO]] =
     div(
       cls := "w-full flex justify-center",
-          input.map(inp =>
-            if inp.trim() == "" then ""
+      store.input.map { input =>
+        if input.trim() == "" then ""
         else
-              decode[Event](inp) match {
+          decode[Event](input) match {
             case Right(event) => event.toString
             case Left(err: io.circe.DecodingFailure) =>
               err.pathToRootString match {
@@ -64,9 +94,8 @@ object Main extends IOWebApp {
             case Left(err: io.circe.ParsingFailure) =>
               "not valid JSON"
           }
-          )
-        )
       }
+    )
 
   val buttonCls =
     "bg-blue-500 hover:bg-blue-700 text-white font-bold py-2 mx-2 px-4 rounded"