diff --git a/.changeset/inject-is-mutating-readonly.md b/.changeset/inject-is-mutating-readonly.md
new file mode 100644
index 0000000000..ce43e97138
--- /dev/null
+++ b/.changeset/inject-is-mutating-readonly.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/angular-query-experimental': patch
+---
+
+Make `injectIsMutating` signal read-only to prevent external modifications to the internal state
\ No newline at end of file
diff --git a/packages/angular-query-experimental/src/inject-is-mutating.ts b/packages/angular-query-experimental/src/inject-is-mutating.ts
index 8f11291b0e..7bab410634 100644
--- a/packages/angular-query-experimental/src/inject-is-mutating.ts
+++ b/packages/angular-query-experimental/src/inject-is-mutating.ts
@@ -25,7 +25,7 @@ export interface InjectIsMutatingOptions {
  * Can be used for app-wide loading indicators
  * @param filters - The filters to apply to the query.
  * @param options - Additional configuration
- * @returns signal with number of fetching mutations.
+ * @returns A read-only signal with the number of fetching mutations.
  */
 export function injectIsMutating(
   filters?: MutationFilters,
@@ -60,5 +60,5 @@ export function injectIsMutating(
 
   destroyRef.onDestroy(unsubscribe)
 
-  return result
+  return result.asReadonly()
 }
diff --git a/packages/angular-query-experimental/tsconfig.json b/packages/angular-query-experimental/tsconfig.json
index 1aea53d869..2aecb18545 100644
--- a/packages/angular-query-experimental/tsconfig.json
+++ b/packages/angular-query-experimental/tsconfig.json
@@ -7,6 +7,13 @@
     "useDefineForClassFields": false,
     "target": "ES2022"
   },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
+    "strictStandalone": true,
+    "strictTemplates": true
+  },
   "include": ["src", "scripts", "test-setup.ts", "*.config.*", "package.json"],
   "references": [{ "path": "../query-core" }, { "path": "../query-devtools" }]
 }