From 0275c7d80ebe76e825498bc4839cdb6f5bce8520 Mon Sep 17 00:00:00 2001
From: Claudius Ellsel <claudius.ellsel@live.de>
Date: Thu, 16 Jul 2026 14:59:05 +0200
Subject: [PATCH] Preserve fields after escaped brace sequences

* Keep brace-depth accounting stable for escaped opening braces.
* Verify later fields survive parse-write-parse round trips.
---
 bibtexparser/splitter.py                 |  6 ++++++
 tests/middleware_tests/test_enclosing.py | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/bibtexparser/splitter.py b/bibtexparser/splitter.py
index bbc3e97..4cf6ee5 100644
--- a/bibtexparser/splitter.py
+++ b/bibtexparser/splitter.py
@@ -197,6 +197,12 @@ def _is_escaped():
                 return next_mark.start()
             # Check for end of entry:
             elif next_mark.group(0) == "}" and not _is_escaped():
+                # A malformed escaped-brace sequence can reduce the tracked depth too early.
+                # If a comma follows, this brace belongs to the field value; consume it and let
+                # the comma terminate the field instead of silently dropping subsequent fields.
+                remaining = self.bibstr[next_mark.end() :].lstrip()
+                if remaining.startswith(","):
+                    continue
                 self._unaccepted_mark = next_mark
                 return next_mark.start()
 
diff --git a/tests/middleware_tests/test_enclosing.py b/tests/middleware_tests/test_enclosing.py
index e5e021f..0f2dd98 100644
--- a/tests/middleware_tests/test_enclosing.py
+++ b/tests/middleware_tests/test_enclosing.py
@@ -421,4 +421,28 @@ def test_string_reference_roundtrip():
     assert "year = {2019}" in written
 
 
+def test_escaped_brace_sequence_roundtrip():
+    """The issue #452 field value remains parseable after default parse and write middleware."""
+    bibtex = r"""@Article{Konstadinidis2009,
+        abstract = {The 396$\{2}$ chip is fabricated in a 65-nm process.},
+        author_keywords = {Arrays; Chip multi-threading (CMT); Register files}
+    }"""
+    expected_abstract = r"The 396$\{2}$ chip is fabricated in a 65-nm process."
+
+    library = bibtexparser.parse_string(bibtex)
+    assert len(library.failed_blocks) == 0
+    parsed_abstract = library.entries[0]["abstract"]
+    assert parsed_abstract == expected_abstract
+
+    written = bibtexparser.write_string(library)
+    assert r"396$\{2}$" in written
+
+    reparsed = bibtexparser.parse_string(written)
+    assert len(reparsed.failed_blocks) == 0
+    assert reparsed.entries[0]["abstract"] == parsed_abstract
+    assert reparsed.entries[0]["author_keywords"] == (
+        "Arrays; Chip multi-threading (CMT); Register files"
+    )
+
+
 # TODO round-trip tests (removal -> addition -> removal)