@@ -51,6 +51,9 @@ Git executable and safety
 API changes
 -----------
 
+* Raw diffs preserve non-UTF-8 filename bytes in ``a_rawpath``, ``b_rawpath``,
+  and raw rename fields. Staged-file diffs no longer fail while decoding legacy
+  filenames; blob contents remain byte streams regardless of their encoding.
 * ``Tree.cache`` and ``TreeModifier`` remain supported. They edit one tree's
   in-memory entries; object IDs and parent trees do not change automatically.
   Tree serialization now delegates construction to Git or the supported Gix
 
@@ -761,34 +761,29 @@ def finalize_process_with_stderr(proc: Union["Popen", "Git.AutoInterrupt"]) -> N
 
     @staticmethod
     def _handle_diff_line(lines_bytes: bytes, repo: "Repo", index: DiffIndex["Diff"]) -> None:
-        lines = lines_bytes.decode(defenc)
-
         # Discard everything before the first colon, and the colon itself.
-        _, _, lines = lines.partition(":")
+        _, _, lines = lines_bytes.partition(b":")
 
         # Each record is a metadata field starting with a colon, followed by one path,
         # or two for copies and renames, each terminated by NUL. A path may itself
         # start with a colon or contain a line feed, so read the fields in order
         # instead of splitting at colons.
-        fields = iter(lines.rstrip("\n").split("\x00"))
+        fields = iter(lines.rstrip(b"\n").split(b"\x00"))
         for meta in fields:
             if not meta:
                 # The line data is empty, skip.
                 continue
-            if meta.startswith(":"):
-                meta = meta[1:]
+            metadata = (meta[1:] if meta.startswith(b":") else meta).decode("ascii")
             a_blob_id: Optional[str]
             b_blob_id: Optional[str]
-            old_mode, new_mode, a_blob_id, b_blob_id, _change_type = meta.split(None, 4)
+            old_mode, new_mode, a_blob_id, b_blob_id, _change_type = metadata.split(None, 4)
             # Change type can be R100
             # R: status letter
             # 100: score (in case of copy and rename)
             change_type: Lit_change_type = cast(Lit_change_type, _change_type[0])
             score_str = "".join(_change_type[1:])
             score = int(score_str) if score_str.isdigit() else None
-            path = next(fields, "")
-            a_path = path.encode(defenc)
-            b_path = path.encode(defenc)
+            a_path = b_path = next(fields, b"")
             deleted_file = False
             new_file = False
             copied_file = False
@@ -805,9 +800,9 @@ def _handle_diff_line(lines_bytes: bytes, repo: "Repo", index: DiffIndex["Diff"]
                 new_file = True
             elif change_type == "C":
                 copied_file = True
-                b_path = next(fields, "").encode(defenc)
+                b_path = next(fields, b"")
             elif change_type == "R":
-                b_path = next(fields, "").encode(defenc)
+                b_path = next(fields, b"")
                 rename_from, rename_to = a_path, b_path
             elif change_type == "T":
                 # Nothing to do.
 
@@ -6,6 +6,7 @@
 import os.path as osp
 
 import ddt
+import pytest
 
 from git import NULL_TREE, Diff, DiffIndex, Diffable, Repo
 from git.diff import decode_path
@@ -19,6 +20,22 @@ def to_raw(input):
     return input.replace(b"\t", b"\x00")
 
 
+@pytest.mark.parametrize("change", [b"A", b"D", b"M", b"R100", b"C100"])
+def test_raw_diff_preserves_non_utf8_paths(change):
+    before = b"legacy-\xf5\t:\n.pas"
+    after = b"renamed-\xe3.pas"
+    output = b":100644 100644 " + b"1" * 40 + b" " + b"2" * 40 + b" " + change + b"\0" + before + b"\0"
+    if change.startswith((b"R", b"C")):
+        output += after + b"\0"
+    diffs = DiffIndex()
+    Diff._handle_diff_line(output, None, diffs)
+    assert len(diffs) == 1
+    assert diffs[0].a_rawpath == before
+    assert diffs[0].b_rawpath == (after if change.startswith((b"R", b"C")) else before)
+    if change.startswith(b"R"):
+        assert (diffs[0].raw_rename_from, diffs[0].raw_rename_to) == (before, after)
+
+
 @ddt.ddt
 class TestDiff(TestBase):
     def setUp(self):
 
@@ -18,6 +18,7 @@
 
 from git import NULL_TREE, BlobFilter, Diff, Git, IndexFile, Object, Repo, Tree
 from git.diff import NULL_TREE_SHA
+from git.compat import defenc
 from git.exc import (
     CheckoutError,
     GitCommandError,
@@ -38,6 +39,19 @@
 _logger = logging.getLogger(__name__)
 
 
+def test_staged_legacy_filename_and_blob_bytes():
+    with fixture_repo("legacy-index.sh") as repo:
+        (entry,) = repo.index.iter_entries()
+        assert entry.path.encode(defenc, "surrogateescape") == b"fonte-\xf5.pas"
+        assert repo.odb.stream(entry.binsha).read() == b"// vers\xe3o nova\n"
+        (diff,) = repo.index.diff("HEAD")
+        assert (diff.a_rawpath, diff.b_rawpath) == (b"fonte-\xf5.pas", b"fonte-\xf5.pas")
+        assert {blob.data_stream.read() for blob in (diff.a_blob, diff.b_blob)} == {
+            b"// vers\xe3o original\n",
+            b"// vers\xe3o nova\n",
+        }
+
+
 @ddt.ddt
 class TestIndex(TestBase):
     @with_rw_repo("HEAD")
 
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -eu
+git init --initial-branch=main repo
+cd repo
+original=$(printf '// vers\343o original\n' | git hash-object -w --stdin)
+printf '100644 %s\tfonte-\365.pas\0' "$original" | git update-index -z --index-info
+git commit -m initial
+staged=$(printf '// vers\343o nova\n' | git hash-object -w --stdin)
+printf '100644 %s\tfonte-\365.pas\0' "$staged" | git update-index -z --index-info