diff --git a/packages/angular-query-experimental/src/__tests__/inject-mutation-state.test.ts b/packages/angular-query-experimental/src/__tests__/inject-mutation-state.test.ts
index bf3c37f39b..9e72b5e245 100644
--- a/packages/angular-query-experimental/src/__tests__/inject-mutation-state.test.ts
+++ b/packages/angular-query-experimental/src/__tests__/inject-mutation-state.test.ts
@@ -144,7 +144,6 @@ describe('injectMutationState', () => {
             <span>{{ mutation.status }}</span>
           }
         `,
-        standalone: true,
       })
       class FakeComponent {
         name = input.required<string>()
diff --git a/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts b/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts
index 3ea18743d7..2ecccf882e 100644
--- a/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts
+++ b/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts
@@ -58,8 +58,6 @@ describe('injectMutation', () => {
       }))
     })
 
-    TestBed.tick()
-
     mutation.mutate(result)
     vi.advanceTimersByTime(1)
 
@@ -133,9 +131,17 @@ describe('injectMutation', () => {
 
     mutation.mutate('xyz')
 
-    const mutations = mutationCache.find({ mutationKey: ['2'] })
+    mutationKey.set(['3'])
+
+    mutation.mutate('xyz')
 
-    expect(mutations?.options.mutationKey).toEqual(['2'])
+    expect(mutationCache.find({ mutationKey: ['1'] })).toBeUndefined()
+    expect(
+      mutationCache.find({ mutationKey: ['2'] })?.options.mutationKey,
+    ).toEqual(['2'])
+    expect(
+      mutationCache.find({ mutationKey: ['3'] })?.options.mutationKey,
+    ).toEqual(['3'])
   })
 
   test('should reset state after invoking mutation.reset', async () => {
@@ -310,7 +316,6 @@ describe('injectMutation', () => {
         <button (click)="mutate()"></button>
         <span>{{ mutation.data() }}</span>
       `,
-      standalone: true,
     })
     class FakeComponent {
       name = input.required<string>()
@@ -333,8 +338,6 @@ describe('injectMutation', () => {
     button.triggerEventHandler('click')
 
     await resolveMutations()
-    fixture.detectChanges()
-
     const text = debugElement.query(By.css('span')).nativeElement.textContent
     expect(text).toEqual('value')
     const mutation = mutationCache.find({ mutationKey: ['fake', 'value'] })
@@ -351,7 +354,6 @@ describe('injectMutation', () => {
         <button (click)="mutate()"></button>
         <span>{{ mutation.data() }}</span>
       `,
-      standalone: true,
     })
     class FakeComponent {
       name = input.required<string>()
@@ -394,6 +396,37 @@ describe('injectMutation', () => {
     expect(mutation2!.options.mutationKey).toEqual(['fake', 'updatedValue'])
   })
 
+  test('should have pending state when mutating in constructor', async () => {
+    @Component({
+      selector: 'app-fake',
+      template: `
+        <span>{{ mutation.isPending() ? 'pending' : 'not pending' }}</span>
+      `,
+    })
+    class FakeComponent {
+      mutation = injectMutation(() => ({
+        mutationKey: ['fake'],
+        mutationFn: () => sleep(0).then(() => 'fake'),
+      }))
+
+      constructor() {
+        this.mutation.mutate()
+      }
+    }
+
+    const fixture = TestBed.createComponent(FakeComponent)
+    const { debugElement } = fixture
+    const span = debugElement.query(By.css('span'))
+
+    vi.advanceTimersByTime(1)
+
+    expect(span.nativeElement.textContent).toEqual('pending')
+
+    await resolveMutations()
+
+    expect(span.nativeElement.textContent).toEqual('not pending')
+  })
+
   describe('throwOnError', () => {
     test('should evaluate throwOnError when mutation is expected to throw', async () => {
       const err = new Error('Expected mock error. All is well!')
diff --git a/packages/angular-query-experimental/src/__tests__/inject-query.test.ts b/packages/angular-query-experimental/src/__tests__/inject-query.test.ts
index 44964b7927..0309296430 100644
--- a/packages/angular-query-experimental/src/__tests__/inject-query.test.ts
+++ b/packages/angular-query-experimental/src/__tests__/inject-query.test.ts
@@ -520,7 +520,6 @@ describe('injectQuery', () => {
     @Component({
       selector: 'app-fake',
       template: `{{ query.data() }}`,
-      standalone: true,
     })
     class FakeComponent {
       name = input.required<string>()
diff --git a/packages/angular-query-experimental/src/inject-mutation.ts b/packages/angular-query-experimental/src/inject-mutation.ts
index 16b22ed2f7..ad8fadc015 100644
--- a/packages/angular-query-experimental/src/inject-mutation.ts
+++ b/packages/angular-query-experimental/src/inject-mutation.ts
@@ -4,7 +4,6 @@ import {
   NgZone,
   assertInInjectionContext,
   computed,
-  effect,
   inject,
   signal,
   untracked,
@@ -71,7 +70,15 @@ export function injectMutation<
       null
 
     return computed(() => {
-      return (instance ||= new MutationObserver(queryClient, optionsSignal()))
+      const observerOptions = optionsSignal()
+      return untracked(() => {
+        if (instance) {
+          instance.setOptions(observerOptions)
+        } else {
+          instance = new MutationObserver(queryClient, observerOptions)
+        }
+        return instance
+      })
     })
   })()
 
@@ -84,14 +91,6 @@ export function injectMutation<
     }
   })
 
-  /**
-   * Computed signal that gets result from mutation cache based on passed options
-   */
-  const resultFromInitialOptionsSignal = computed(() => {
-    const observer = observerSignal()
-    return observer.getCurrentResult()
-  })
-
   /**
    * Signal that contains result set by subscriber
    */
@@ -102,50 +101,36 @@ export function injectMutation<
     TContext
   > | null>(null)
 
-  effect(
-    () => {
-      const observer = observerSignal()
-      const observerOptions = optionsSignal()
-
-      untracked(() => {
-        observer.setOptions(observerOptions)
-      })
-    },
-    {
-      injector,
-    },
-  )
-
-  effect(
-    () => {
-      // observer.trackResult is not used as this optimization is not needed for Angular
-      const observer = observerSignal()
+  /**
+   * Computed signal that gets result from mutation cache based on passed options
+   */
+  const resultFromInitialOptionsSignal = computed(() => {
+    const observer = observerSignal()
 
-      untracked(() => {
-        const unsubscribe = ngZone.runOutsideAngular(() =>
-          observer.subscribe(
-            notifyManager.batchCalls((state) => {
-              ngZone.run(() => {
-                if (
-                  state.isError &&
-                  shouldThrowError(observer.options.throwOnError, [state.error])
-                ) {
-                  ngZone.onError.emit(state.error)
-                  throw state.error
-                }
+    untracked(() => {
+      const unsubscribe = ngZone.runOutsideAngular(() =>
+        // observer.trackResult is not used as this optimization is not needed for Angular
+        observer.subscribe(
+          notifyManager.batchCalls((state) => {
+            ngZone.run(() => {
+              if (
+                state.isError &&
+                shouldThrowError(observer.options.throwOnError, [state.error])
+              ) {
+                ngZone.onError.emit(state.error)
+                throw state.error
+              }
+
+              resultFromSubscriberSignal.set(state)
+            })
+          }),
+        ),
+      )
+      destroyRef.onDestroy(unsubscribe)
+    })
 
-                resultFromSubscriberSignal.set(state)
-              })
-            }),
-          ),
-        )
-        destroyRef.onDestroy(unsubscribe)
-      })
-    },
-    {
-      injector,
-    },
-  )
+    return observer.getCurrentResult()
+  })
 
   const resultSignal = computed(() => {
     const resultFromSubscriber = resultFromSubscriberSignal()