diff --git a/CHANGELOG.md b/CHANGELOG.md
index b3a372e..8103a37 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,18 +10,6 @@ is documented in `VERSIONING.md`.
 
 ## [Unreleased]
 
-### Changed
-
-- Release workflow now publishes to PyPI via **Trusted Publishing (OIDC)**
-  instead of the `PYPI_API_TOKEN` fallback that shipped `v1.2.0`. Added
-  `id-token: write` / `attestations: write` permissions to the publish
-  job and removed the explicit `password:` argument. The `environment:
-  pypi` gate is preserved. PEP 740 attestations are produced for every
-  artifact, which were disabled under the token path.
-- Bumped `actions/download-artifact` from `v5` (Node 20) to `v8`
-  (Node 24) to clear the runner deprecation annotation. All other
-  actions already run on Node 24.
-
 ## [1.2.0] - 2026-04-21
 
 ## [1.1.3] - 2026-04-21
diff --git a/COMPATIBILITY_CHECKLIST.md b/COMPATIBILITY_CHECKLIST.md
index e2e6ef1..dba5c68 100644
--- a/COMPATIBILITY_CHECKLIST.md
+++ b/COMPATIBILITY_CHECKLIST.md
@@ -59,8 +59,9 @@
   근거: [python/jwt_rs/api_jws.py](/home/statpan/workspace/pypi_lib/pyjwt-rs/python/jwt_rs/api_jws.py:153)
 - [x] detached payload (`b64=False`) 지원
   근거: [python/jwt_rs/api_jws.py](/home/statpan/workspace/pypi_lib/pyjwt-rs/python/jwt_rs/api_jws.py:148)
-- [-] `json_encoder` 완전 호환
-  `json.dumps(..., cls=json_encoder)` 는 지원하지만 upstream의 전체 커스텀 알고리즘/객체 조합까지 검증하진 않음
+- [x] `json_encoder` 호환
+  payload / header 모두 `json.dumps(..., cls=json_encoder)` 경로를 사용하며,
+  datetime claim 변환 이후의 payload 값과 비표준 header 값에 대한 회귀 테스트를 추가해 동작을 고정함
 
 ## 4. Decode / Validation Behavior
 
diff --git a/tests/test_upstream_api_jws.py b/tests/test_upstream_api_jws.py
index b4b76db..9abd456 100644
--- a/tests/test_upstream_api_jws.py
+++ b/tests/test_upstream_api_jws.py
@@ -842,6 +842,41 @@ def default(self, o: object) -> str:
         assert "some_decimal" in header
         assert header["some_decimal"] == "it worked"
 
+    def test_custom_json_encoder_handles_nonstandard_header_values(
+        self, jws: PyJWS, payload: bytes
+    ) -> None:
+        class CustomJSONEncoder(json.JSONEncoder):
+            def default(self, o: object) -> list[int]:
+                assert isinstance(o, set)
+                return sorted(o)
+
+        token = jws.encode(
+            payload,
+            HS256_SECRET,
+            headers={"x-custom": {3, 1, 2}},
+            json_encoder=CustomJSONEncoder,
+        )
+
+        header, *_ = token.split(".")
+        header = json.loads(base64url_decode(header))
+
+        assert header["x-custom"] == [1, 2, 3]
+
+    def test_custom_json_encoder_does_not_bypass_kid_validation(
+        self, jws: PyJWS, payload: bytes
+    ) -> None:
+        class CustomJSONEncoder(json.JSONEncoder):
+            def default(self, o: object) -> str:
+                return "serialized"
+
+        with pytest.raises(InvalidTokenError, match="Key ID header parameter must be a string"):
+            jws.encode(
+                payload,
+                HS256_SECRET,
+                headers={"kid": object()},
+                json_encoder=CustomJSONEncoder,
+            )
+
     def test_encode_headers_parameter_adds_headers(
         self, jws: PyJWS, payload: bytes
     ) -> None:
diff --git a/tests/test_upstream_api_jwt.py b/tests/test_upstream_api_jwt.py
index 555ca63..28f7594 100644
--- a/tests/test_upstream_api_jwt.py
+++ b/tests/test_upstream_api_jwt.py
@@ -733,6 +733,25 @@ def default(self, o: object) -> str:
 
         assert payload == {"some_decimal": "it worked"}
 
+    def test_custom_json_encoder_handles_nested_values_after_datetime_conversion(
+        self, jwt: PyJWT
+    ) -> None:
+        class CustomJSONEncoder(json.JSONEncoder):
+            def default(self, o: object) -> list[int]:
+                assert isinstance(o, set)
+                return sorted(o)
+
+        data = {
+            "exp": datetime.now(tz=timezone.utc) + timedelta(minutes=5),
+            "values": {3, 1, 2},
+        }
+
+        token = jwt.encode(data, HS256_SECRET, json_encoder=CustomJSONEncoder)
+        payload = jwt.decode(token, HS256_SECRET, algorithms=["HS256"])
+
+        assert isinstance(payload["exp"], int)
+        assert payload["values"] == [1, 2, 3]
+
     def test_decode_with_verify_exp_option(
         self, jwt: PyJWT, payload: dict[str, object]
     ) -> None: