From 771f1ca6ab8a9c430026ac608752f8fcb4ce3c2f Mon Sep 17 00:00:00 2001
From: Thibault Sottiaux <tibo@openai.com>
Date: Mon, 5 Jan 2026 17:41:23 -0800
Subject: [PATCH] fix: accept whitespace-padded patch markers (#8746)

Trim whitespace when validating '*** Begin Patch'/'*** End Patch'
markers in codex-apply-patch so padded marker lines parse as intended,
and add regression coverage (unit + fixture scenario); this avoids
apply_patch failures when models include extra spacing. Tested with
cargo test -p codex-apply-patch.
---
 codex-rs/apply-patch/src/parser.rs            | 26 +++++++++++++++++--
 .../expected/file.txt                         |  1 +
 .../input/file.txt                            |  1 +
 .../patch.txt                                 |  6 +++++
 4 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/expected/file.txt
 create mode 100644 codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/input/file.txt
 create mode 100644 codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/patch.txt

diff --git a/codex-rs/apply-patch/src/parser.rs b/codex-rs/apply-patch/src/parser.rs
index 768c89ad7..8785b3851 100644
--- a/codex-rs/apply-patch/src/parser.rs
+++ b/codex-rs/apply-patch/src/parser.rs
@@ -227,11 +227,14 @@ fn check_start_and_end_lines_strict(
     first_line: Option<&&str>,
     last_line: Option<&&str>,
 ) -> Result<(), ParseError> {
+    let first_line = first_line.map(|line| line.trim());
+    let last_line = last_line.map(|line| line.trim());
+
     match (first_line, last_line) {
-        (Some(&first), Some(&last)) if first == BEGIN_PATCH_MARKER && last == END_PATCH_MARKER => {
+        (Some(first), Some(last)) if first == BEGIN_PATCH_MARKER && last == END_PATCH_MARKER => {
             Ok(())
         }
-        (Some(&first), _) if first != BEGIN_PATCH_MARKER => Err(InvalidPatchError(String::from(
+        (Some(first), _) if first != BEGIN_PATCH_MARKER => Err(InvalidPatchError(String::from(
             "The first line of the patch must be '*** Begin Patch'",
         ))),
         _ => Err(InvalidPatchError(String::from(
@@ -444,6 +447,25 @@ fn test_parse_patch() {
             "The last line of the patch must be '*** End Patch'".to_string()
         ))
     );
+
+    assert_eq!(
+        parse_patch_text(
+            concat!(
+                "*** Begin Patch",
+                " ",
+                "\n*** Add File: foo\n+hi\n",
+                " ",
+                "*** End Patch"
+            ),
+            ParseMode::Strict
+        )
+        .unwrap()
+        .hunks,
+        vec![AddFile {
+            path: PathBuf::from("foo"),
+            contents: "hi\n".to_string()
+        }]
+    );
     assert_eq!(
         parse_patch_text(
             "*** Begin Patch\n\
diff --git a/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/expected/file.txt b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/expected/file.txt
new file mode 100644
index 000000000..f719efd43
--- /dev/null
+++ b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/expected/file.txt
@@ -0,0 +1 @@
+two
diff --git a/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/input/file.txt b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/input/file.txt
new file mode 100644
index 000000000..5626abf0f
--- /dev/null
+++ b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/input/file.txt
@@ -0,0 +1 @@
+one
diff --git a/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/patch.txt b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/patch.txt
new file mode 100644
index 000000000..3d2a1dbe5
--- /dev/null
+++ b/codex-rs/apply-patch/tests/fixtures/scenarios/020_whitespace_padded_patch_marker_lines/patch.txt
@@ -0,0 +1,6 @@
+*** Begin Patch 
+*** Update File: file.txt
+@@
+-one
++two
+ *** End Patch