From 55fb979923f9e314074aa4b2ae0de86b8acae087 Mon Sep 17 00:00:00 2001
From: Kadir Can Ozden <101993364+bysiber@users.noreply.github.com>
Date: Fri, 20 Feb 2026 18:57:52 +0300
Subject: [PATCH 1/2] Fix perfect match missed for headers with empty values
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HeaderTable.search() returns (index, name, value) for perfect matches
and (index, name, None) for partial matches. The encoder distinguishes
them with `if perfect:`, but this fails when value is b"" because
empty bytes are falsy in Python.

46 of 61 static table entries have an empty value (e.g. :authority,
accept-charset, accept-language, age, allow, …). When encoding a
header that perfectly matches one of these entries, the encoder falls
through to the indexed-literal path — using 2+ bytes instead of 1 and
unnecessarily adding the entry to the dynamic table.

Change the check to `if perfect is not None:` so that b"" is treated
as a valid perfect match.
---
 src/hpack/hpack.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hpack/hpack.py b/src/hpack/hpack.py
index 7e33e77..20dce0a 100644
--- a/src/hpack/hpack.py
+++ b/src/hpack/hpack.py
@@ -313,7 +313,7 @@ def add(self, to_add: tuple[bytes, bytes], sensitive: bool, huffman: bool = Fals
         # can use the indexed literal.
         index, name, perfect = match
 
-        if perfect:
+        if perfect is not None:
             # Indexed representation.
             encoded = self._encode_indexed(index)
         else:

From 53f60ce372d6914b5f774479f9340942eaf4e83b Mon Sep 17 00:00:00 2001
From: Thomas Kriechbaumer <thomas@kriechbaumer.name>
Date: Mon, 6 Apr 2026 11:34:38 +0200
Subject: [PATCH 2/2] Fix perfect match missed for headers with empty values:
 add test and changelog

---
 CHANGELOG.rst       |  1 +
 tests/test_hpack.py | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 8b4c060..62f593f 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -13,6 +13,7 @@ dev
 
 - Support for Python 3.14 has been added.
 - Support for PyPy 3.11 has been added.
+- Fixed perfect match missed for headers with empty values
 
 
 **Bugfixes**
diff --git a/tests/test_hpack.py b/tests/test_hpack.py
index 3864a33..e9c170c 100644
--- a/tests/test_hpack.py
+++ b/tests/test_hpack.py
@@ -126,6 +126,18 @@ def test_indexed_header_field(self):
         assert e.encode(header_set, huffman=False) == result
         assert list(e.header_table.dynamic_entries) == []
 
+    def test_indexed_header_field_empty_value_string(self):
+        """
+        The header field representation uses an indexed header field, from
+        the static table.
+        """
+        e = Encoder()
+        header_set = {':authority': ''}
+        result = b'\x81'
+
+        assert e.encode(header_set, huffman=False) == result
+        assert list(e.header_table.dynamic_entries) == []
+
     def test_indexed_header_field_from_static_table(self):
         e = Encoder()
         e.header_table_size = 0