diff --git a/src/uix/soma/morfo/resolver.ts b/src/uix/soma/morfo/resolver.ts
index a99517460..6084d1e51 100644
--- a/src/uix/soma/morfo/resolver.ts
+++ b/src/uix/soma/morfo/resolver.ts
@@ -107,9 +107,17 @@ export function resolveMorfoAriaValue(entry: MorfoAriaEntry, bindings: MorfoBind
 
 /**
  * Resolves a part's full attribute map (role + data-* + aria-*) against the
- * given bindings. Returns `undefined`-valued entries for declared attrs that
- * shouldn't be emitted in the current state — the caller decides whether to
- * skip them (Svelte does it automatically; `dom.apply` removes them).
+ * given bindings.
+ *
+ * The map ALWAYS includes every declared attr (data with a `value` source +
+ * every aria entry). Attrs whose condition is falsy or whose value source
+ * resolves to nothing are emitted as `undefined`, which `dom.apply` reads as
+ * "remove this attribute" and Svelte ignores during render. This is what
+ * lets the runtime clean up attrs that previously matched their condition
+ * but no longer do (e.g. `data-invalid` toggling from set to absent).
+ *
+ * Entries with no `value` source on `data` are skipped entirely — they are
+ * documentation in the morfo, not runtime-managed attrs.
  */
 export function resolvePartAttrs(
 	partMeta: MorfoPart,
@@ -123,19 +131,19 @@ export function resolvePartAttrs(
 
 	for (const data of partMeta.data) {
 		if (!data.value) continue;
-		if (!shouldEmitMorfoEntry(data.condition, bindings)) continue;
-		const value = resolveMorfoDataValue(data, bindings);
-		if (value !== undefined) {
-			result[data.attr] = value;
+		if (!shouldEmitMorfoEntry(data.condition, bindings)) {
+			result[data.attr] = undefined;
+			continue;
 		}
+		result[data.attr] = resolveMorfoDataValue(data, bindings);
 	}
 
 	for (const aria of partMeta.aria) {
-		if (!shouldEmitMorfoEntry(aria.condition, bindings)) continue;
-		const value = resolveMorfoAriaValue(aria, bindings);
-		if (value !== undefined) {
-			result[aria.attr] = value;
+		if (!shouldEmitMorfoEntry(aria.condition, bindings)) {
+			result[aria.attr] = undefined;
+			continue;
 		}
+		result[aria.attr] = resolveMorfoAriaValue(aria, bindings);
 	}
 
 	return result;
diff --git a/src/uix/soma/morfo/runtime.svelte.test.ts b/src/uix/soma/morfo/runtime.svelte.test.ts
index ef6595a80..0e21258d7 100644
--- a/src/uix/soma/morfo/runtime.svelte.test.ts
+++ b/src/uix/soma/morfo/runtime.svelte.test.ts
@@ -125,6 +125,42 @@ describe('createMorfoRuntime', () => {
 		cleanup()
 	})
 
+	it('removes conditional attrs when their condition flips back to false', () => {
+		const ref = state<HTMLElement | null>(null)
+		const invalid = state(false)
+		const { cleanup } = withEffectRoot(() => {
+			const id = state('tog-1')
+			const r = createMorfoRuntime(toggleMorfo, {
+				dom,
+				states: { on: () => false },
+				props: {
+					disabled: () => false,
+					readonly: () => false,
+					required: () => false,
+					invalid: () => invalid.current,
+					ariaLabel: () => undefined
+				}
+			})
+			r.registerPart('provider', { id, ref })
+		})
+
+		ref.current = target
+		flushSync()
+		expect(target.hasAttribute('data-invalid')).toBe(false)
+		expect(target.hasAttribute('aria-invalid')).toBe(false)
+
+		invalid.current = true
+		flushSync()
+		expect(target.getAttribute('data-invalid')).toBe('')
+		expect(target.getAttribute('aria-invalid')).toBe('true')
+
+		invalid.current = false
+		flushSync()
+		expect(target.hasAttribute('data-invalid')).toBe(false)
+		expect(target.hasAttribute('aria-invalid')).toBe(false)
+		cleanup()
+	})
+
 	it('throws when registering an unknown part', () => {
 		const { cleanup } = withEffectRoot(() => {
 			const r = createMorfoRuntime(toggleMorfo, { dom })