diff --git a/dist/js/utils/class.js b/dist/js/utils/class.js
index 29b12abc..bbc6c2f6 100644
--- a/dist/js/utils/class.js
+++ b/dist/js/utils/class.js
@@ -71,7 +71,7 @@ function extendThis(childClass, parentClass, config) {
                 Object.defineProperty(childClass.prototype, prop, { get, set });
             }
             else {
-                childClass.prototype[prop] = parentClass.prototype[prop];
+                childClass.prototype[prop] = protos[prop];
             }
             seen.push(prop); // don't override with older definition in hierarchy
             return null;
diff --git a/src/js/utils/class.js b/src/js/utils/class.js
index 6dc7ebc1..5082906e 100644
--- a/src/js/utils/class.js
+++ b/src/js/utils/class.js
@@ -66,7 +66,7 @@ export function extendThis(childClass, parentClass, config) {
                 if (get || set) {
                     Object.defineProperty(childClass.prototype, prop, { get, set });
                 } else {
-                    childClass.prototype[prop] = parentClass.prototype[prop];
+                    childClass.prototype[prop] = protos[prop];
                 }
                 seen.push(prop); // don't override with older definition in hierarchy
                 return null;
diff --git a/src/py/mat3ra/code/mixins/__init__.py b/src/py/mat3ra/code/mixins/__init__.py
index 564362af..9c93fdc8 100644
--- a/src/py/mat3ra/code/mixins/__init__.py
+++ b/src/py/mat3ra/code/mixins/__init__.py
@@ -4,6 +4,7 @@
 from mat3ra.esse.models.system.description import DescriptionSchema
 from mat3ra.esse.models.system.metadata import MetadataSchema
 from mat3ra.esse.models.system.name import NameEntitySchema
+from .hashed_entity import HashedEntityMixin
 
 
 class DefaultableMixin(DefaultableEntitySchema):
diff --git a/src/py/mat3ra/code/mixins/hashed_entity.py b/src/py/mat3ra/code/mixins/hashed_entity.py
new file mode 100644
index 00000000..746e5523
--- /dev/null
+++ b/src/py/mat3ra/code/mixins/hashed_entity.py
@@ -0,0 +1,23 @@
+from typing import Any, Dict
+
+from mat3ra.utils.object import calculate_hash_from_object
+
+
+class HashedEntityMixin:
+    """
+    Mixin for entities that compute a deterministic hash from "meaningful fields".
+
+    Mirrors the JS `HashedEntityMixin`: child classes override `get_hash_object()`,
+    while `calculate_hash()` hashes that object.
+    """
+
+    def get_hash_object(self) -> Dict[str, Any]:  # pragma: no cover
+        return {}
+
+    def calculate_hash(self) -> str:
+        return calculate_hash_from_object(self.get_hash_object())
+
+    @property
+    def hash(self) -> str:
+        return self.calculate_hash()
+
diff --git a/tests/js/utils/class.tests.ts b/tests/js/utils/class.tests.ts
index a4ee4afd..77bd4f65 100644
--- a/tests/js/utils/class.tests.ts
+++ b/tests/js/utils/class.tests.ts
@@ -18,6 +18,15 @@ class BaseEntity extends RuntimeItemsMixin(InMemoryEntity) {
     }
 }
 
+const PrototypeMethodMixin = (superclass: any) =>
+    class extends superclass {
+        methodFromMixinPrototype() {
+            return "from-mixin";
+        }
+    };
+
+class BaseEntityWithPrototypeMethodFromMixin extends PrototypeMethodMixin(BaseEntity) {}
+
 class ExtendClassEntity extends NamedInMemoryEntity {
     declare results: unknown;
 
@@ -75,6 +84,13 @@ class ExtendThisEntity extends BetweenEntity {
     }
 }
 
+class ExtendThisEntityFromMixedBase extends BetweenEntity {
+    constructor(config: object) {
+        super(config);
+        extendThis(ExtendThisEntityFromMixedBase, BaseEntityWithPrototypeMethodFromMixin, config);
+    }
+}
+
 defaultableEntityStaticMixin(ExtendThisEntity);
 defaultableEntityMixin(ExtendThisEntity.prototype);
 
@@ -106,6 +122,11 @@ describe("extendThis", () => {
         expect(JSON.stringify(obj.results)).to.be.equal(JSON.stringify([{ name: "test" }]));
     });
 
+    it("copies prototype methods defined by mixins", () => {
+        const obj = new ExtendThisEntityFromMixedBase({});
+        expect((obj as any).methodFromMixinPrototype()).to.be.equal("from-mixin");
+    });
+
     it("remembers intermediate methods", () => {
         const base = new BaseBetweenEntity({});
         expect(base.betweenMethod()).to.be.equal("base");
diff --git a/tests/py/unit/test_mixins.py b/tests/py/unit/test_mixins.py
index 64daaf01..ccd18e39 100644
--- a/tests/py/unit/test_mixins.py
+++ b/tests/py/unit/test_mixins.py
@@ -1,6 +1,7 @@
 from typing import Optional
 
-from mat3ra.code.mixins import DefaultableMixin, NamedMixin
+from mat3ra.code.mixins import DefaultableMixin, HashedEntityMixin, NamedMixin
+from mat3ra.utils.object import calculate_hash_from_object
 
 
 def test_defaultable_mixin():
@@ -60,3 +61,13 @@ class ExampleComplex(DefaultableMixin, NamedMixin):
     assert instance.key is None
     assert instance.number is None
     assert hasattr(instance, "isDefault")
+
+
+def test_hashed_entity_mixin():
+    class ExampleHashed(HashedEntityMixin):
+        def get_hash_object(self):
+            return {"b": 1, "a": 2}
+
+    instance = ExampleHashed()
+    assert instance.calculate_hash() == calculate_hash_from_object({"b": 1, "a": 2})
+    assert instance.hash == instance.calculate_hash()