From 5a8c01ed4e4119b83cdfe2e4b6c7b71c1f1e87aa Mon Sep 17 00:00:00 2001
From: Minh Vu <vuhoangminh97@gmail.com>
Date: Sat, 27 Jun 2026 01:37:07 +0200
Subject: [PATCH] fix(reactivity): stop once watchers after callback throws

---
 packages/reactivity/__tests__/watch.spec.ts | 34 +++++++++++++++++++++
 packages/reactivity/src/watch.ts            |  8 +++--
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/packages/reactivity/__tests__/watch.spec.ts b/packages/reactivity/__tests__/watch.spec.ts
index db19070e03d..31f739830ff 100644
--- a/packages/reactivity/__tests__/watch.spec.ts
+++ b/packages/reactivity/__tests__/watch.spec.ts
@@ -157,6 +157,40 @@ describe('watch', () => {
     expect(onError.mock.calls[1]).toMatchObject(['oops in once watch'])
   })
 
+  test('once option stops after sync callback throw', () => {
+    const onError = vi.fn()
+    const call: WatchOptions['call'] = function call(fn, type, args) {
+      if (Array.isArray(fn)) {
+        fn.forEach(f => call(f, type, args))
+        return
+      }
+      try {
+        fn.apply(null, args)
+      } catch (e) {
+        onError(e, type)
+      }
+    }
+
+    const source = ref(0)
+    const cb = vi.fn(() => {
+      throw 'oops in once watch'
+    })
+
+    watch(source, cb, { call, once: true })
+
+    source.value++
+    expect(cb).toHaveBeenCalledTimes(1)
+    expect(onError.mock.calls).toMatchObject([
+      ['oops in once watch', WatchErrorCodes.WATCH_CALLBACK],
+    ])
+
+    source.value++
+    expect(cb).toHaveBeenCalledTimes(1)
+    expect(onError.mock.calls).toMatchObject([
+      ['oops in once watch', WatchErrorCodes.WATCH_CALLBACK],
+    ])
+  })
+
   test('watch with onWatcherCleanup', async () => {
     let dummy = 0
     let source: Ref<number>
diff --git a/packages/reactivity/src/watch.ts b/packages/reactivity/src/watch.ts
index 2c537c59083..d1124e9d963 100644
--- a/packages/reactivity/src/watch.ts
+++ b/packages/reactivity/src/watch.ts
@@ -221,9 +221,11 @@ export function watch(
   if (once && cb) {
     const _cb = cb
     cb = (...args) => {
-      const res = _cb(...args)
-      watchHandle()
-      return res
+      try {
+        return _cb(...args)
+      } finally {
+        watchHandle()
+      }
     }
   }