From 3b08e9c07a80b9bbbb6d953f034d986129a42478 Mon Sep 17 00:00:00 2001
From: Gore Williams <88089185+gorewilliams@users.noreply.github.com>
Date: Fri, 4 Sep 2026 14:42:03 +0300
Subject: [PATCH] Improve invalid header encoding errors

---
 src/httpx2/httpx2/_models.py        | 13 ++++++-------
 tests/httpx2/models/test_headers.py | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/httpx2/httpx2/_models.py b/src/httpx2/httpx2/_models.py
index 0272f36d..3092bce9 100644
--- a/src/httpx2/httpx2/_models.py
+++ b/src/httpx2/httpx2/_models.py
@@ -152,15 +152,14 @@ def __init__(
 
         if isinstance(headers, Headers):
             self._list = list(headers._list)
-        elif isinstance(headers, Mapping):
-            for k, v in headers.items():
-                bytes_key = _normalize_header_key(k, encoding)
-                bytes_value = _normalize_header_value(v, encoding)
-                self._list.append((bytes_key, bytes_key.lower(), bytes_value))
         elif headers is not None:
-            for k, v in headers:
+            header_items = headers.items() if isinstance(headers, Mapping) else headers
+            for k, v in header_items:
                 bytes_key = _normalize_header_key(k, encoding)
-                bytes_value = _normalize_header_value(v, encoding)
+                try:
+                    bytes_value = _normalize_header_value(v, encoding)
+                except UnicodeEncodeError as exc:
+                    raise ValueError(f"Unable to encode header value for {k!r}") from exc
                 self._list.append((bytes_key, bytes_key.lower(), bytes_value))
 
         self._encoding = encoding
diff --git a/tests/httpx2/models/test_headers.py b/tests/httpx2/models/test_headers.py
index 666b7886..fd081643 100644
--- a/tests/httpx2/models/test_headers.py
+++ b/tests/httpx2/models/test_headers.py
@@ -36,6 +36,22 @@ def test_headers() -> None:
     assert repr(h) == "Headers({'a': '123', 'b': '789'})"
 
 
+@pytest.mark.parametrize(
+    "headers",
+    [
+        {"auth": "שלום"},
+        [("auth", "שלום")],
+    ],
+)
+def test_header_value_encoding_error_includes_header_name(
+    headers: dict[str, str] | list[tuple[str, str]],
+) -> None:
+    with pytest.raises(ValueError, match="auth") as exc_info:
+        httpx2.Headers(headers)
+
+    assert isinstance(exc_info.value.__cause__, UnicodeEncodeError)
+
+
 def test_header_mutations() -> None:
     h = httpx2.Headers()
     assert dict(h) == {}