From 4a25186844c5fc439f670e4ec3cae5902fd544a4 Mon Sep 17 00:00:00 2001
From: Chirag Gupta <103719146+chiruu12@users.noreply.github.com>
Date: Mon, 5 Oct 2026 03:38:34 +0530
Subject: [PATCH] fix(data-classes): handle keyword arguments in
 CaseInsensitiveDict.update

---
 .../utilities/data_classes/common.py          |  2 +-
 .../required_dependencies/test_common.py      | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/data_classes/required_dependencies/test_common.py

diff --git a/aws_lambda_powertools/utilities/data_classes/common.py b/aws_lambda_powertools/utilities/data_classes/common.py
index 3b9171b286d..c8908eda9ce 100644
--- a/aws_lambda_powertools/utilities/data_classes/common.py
+++ b/aws_lambda_powertools/utilities/data_classes/common.py
@@ -61,7 +61,7 @@ def update(self, data=None, **kwargs):
             if isinstance(data, Mapping):
                 data = data.items()
             super().update((k.lower(), v) for k, v in data)
-        super().update((k.lower(), v) for k, v in kwargs)
+        super().update((k.lower(), v) for k, v in kwargs.items())
 
     def __contains__(self, k):
         return super().__contains__(k.lower())
diff --git a/tests/unit/data_classes/required_dependencies/test_common.py b/tests/unit/data_classes/required_dependencies/test_common.py
new file mode 100644
index 00000000000..2a2ad1f0f93
--- /dev/null
+++ b/tests/unit/data_classes/required_dependencies/test_common.py
@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+from aws_lambda_powertools.utilities.data_classes.common import CaseInsensitiveDict
+
+
+def test_case_insensitive_dict_init_with_kwargs():
+    headers = CaseInsensitiveDict({"Content-Type": "application/json"}, X_Trace_Id="abc")
+
+    assert headers == {"content-type": "application/json", "x_trace_id": "abc"}
+    assert headers["x_trace_id"] == "abc"
+
+
+def test_case_insensitive_dict_update_with_kwargs():
+    headers = CaseInsensitiveDict({"Host": "example.com"})
+    headers.update(ab="1", User_Agent="test")
+
+    assert headers["AB"] == "1"
+    assert headers["user_agent"] == "test"
+    assert len(headers) == 3