From 179863a2d6921fbc5dbaca52c172c644c914206b Mon Sep 17 00:00:00 2001
From: Davide Di Pumpo <davidemak@gmail.com>
Date: Wed, 5 Nov 2025 17:50:22 +0100
Subject: [PATCH] Forces form reset on tag change in OmegaForm Union

---
 .changeset/tangy-results-behave.md                        | 5 +++++
 .../src/components/OmegaForm/OmegaTaggedUnion.vue         | 1 +
 .../src/components/OmegaForm/OmegaTaggedUnionInternal.vue | 5 +++++
 .../vue-components/stories/OmegaForm/FormTaggedUnion.vue  | 8 ++++----
 4 files changed, 15 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/tangy-results-behave.md

diff --git a/.changeset/tangy-results-behave.md b/.changeset/tangy-results-behave.md
new file mode 100644
index 0000000000..5ed740c70d
--- /dev/null
+++ b/.changeset/tangy-results-behave.md
@@ -0,0 +1,5 @@
+---
+"@effect-app/vue-components": patch
+---
+
+Forces form reset on tag change in OmegaForm Union
diff --git a/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnion.vue b/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnion.vue
index f4e4e13eb0..fc1dc3de86 100644
--- a/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnion.vue
+++ b/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnion.vue
@@ -41,6 +41,7 @@ defineProps<{
         :field="inputProps.field as any"
         :state="inputProps.state.value"
         :name="name"
+        :form="form"
       >
         <template
           v-for="(_, slotname) in $slots"
diff --git a/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnionInternal.vue b/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnionInternal.vue
index d12feb9b39..ef471db60e 100644
--- a/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnionInternal.vue
+++ b/packages/vue-components/src/components/OmegaForm/OmegaTaggedUnionInternal.vue
@@ -18,19 +18,24 @@
 import { type DeepKeys, type DeepValue } from "@tanstack/vue-form"
 import { watch } from "vue"
 import { type OmegaFieldInternalApi } from "./InputProps"
+import { type useOmegaForm } from "./useOmegaForm"
 
 const props = defineProps<{
   state: DeepValue<From, Name>
   field: OmegaFieldInternalApi<From, Name>
   name?: DeepKeys<From>
+  form: ReturnType<typeof useOmegaForm<From, To>>
 }>()
 
+const values = props.form.useStore(({ values }) => values)
+
 // Watch for _tag changes
 watch(() => props.state, (newTag, oldTag) => {
   if (newTag === null) {
     props.field.setValue(null as DeepValue<From, Name>)
   }
   if (newTag !== oldTag) {
+    props.form.reset(values.value)
     setTimeout(() => {
       props.field.validate("change")
     }, 0)
diff --git a/packages/vue-components/stories/OmegaForm/FormTaggedUnion.vue b/packages/vue-components/stories/OmegaForm/FormTaggedUnion.vue
index b3b110aa95..3c7c4eb5b2 100644
--- a/packages/vue-components/stories/OmegaForm/FormTaggedUnion.vue
+++ b/packages/vue-components/stories/OmegaForm/FormTaggedUnion.vue
@@ -79,17 +79,17 @@ import { useOmegaForm } from "../../src"
 
 const form = useOmegaForm(
   S.Struct({
-    aString: S.String,
+    aString: S.NonEmptyString255,
     union: S.NullOr(
       S.Union(
         S.Struct({
           a: S.NonEmptyString255,
-          common: S.String,
+          common: S.NonEmptyString255,
           _tag: S.Literal("A")
         }),
         S.Struct({
-          b: S.Number,
-          common: S.String,
+          b: S.NonEmptyString255,
+          common: S.NonEmptyString255,
           _tag: S.Literal("B")
         })
       )