From 8abdd3b8bf065dceecd52d2b22d92b3c407a7c1d Mon Sep 17 00:00:00 2001
From: Thomas Waldmann <tw@waldmann-edv.de>
Date: Thu, 18 Jun 2026 18:23:49 +0200
Subject: [PATCH 1/2] support msgpack 1.2.1

---
 docs/changes.rst            | 2 +-
 pyproject.toml              | 2 +-
 src/borg/helpers/msgpack.py | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/changes.rst b/docs/changes.rst
index 3eaf24eba..5928735b5 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -473,7 +473,7 @@ Note: Many of the fixed issues listed below relate to rather rare or theoretical
 
 Other changes:
 
-- msgpack: allow 1.2.0
+- msgpack: also allow 1.2.0 and 1.2.1
 - use F_FULLFSYNC on macOS for SyncFile data durability, #9383
 - mount: improve error msg when uid/gid cannot be resolved, #9574
 - docs:
diff --git a/pyproject.toml b/pyproject.toml
index b789bf526..c60d128bd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,7 +35,7 @@ dependencies = [
     # Please note:
     # Using any other msgpack version is not supported by Borg development and
     # any feedback related to issues caused by this will be ignored.
-    "msgpack >=1.0.3, <=1.2.0",
+    "msgpack >=1.0.3, <=1.2.1",
     "packaging",
 ]
 
diff --git a/src/borg/helpers/msgpack.py b/src/borg/helpers/msgpack.py
index 0adf8c0b0..ae634e2ee 100644
--- a/src/borg/helpers/msgpack.py
+++ b/src/borg/helpers/msgpack.py
@@ -145,7 +145,7 @@ def is_supported_msgpack():
     version_check = os.environ.get('BORG_MSGPACK_VERSION_CHECK', 'yes').strip().lower()
 
     return version_check == 'no' or (
-        (1, 0, 3) <= msgpack.version[:3] <= (1, 2, 0) and
+        (1, 0, 3) <= msgpack.version[:3] <= (1, 2, 1) and
         msgpack.version not in []
     )
 

From b09bbed3de095d6ac9d69a42a486ec18523046dc Mon Sep 17 00:00:00 2001
From: Thomas Waldmann <tw@waldmann-edv.de>
Date: Thu, 18 Jun 2026 19:42:53 +0200
Subject: [PATCH 2/2] Archive.delete: don't reuse msgpack Unpacker after an
 unpacking failure

msgpack does not support reusing an Unpacker instance after an unpacking
failure - a new instance must be created instead.

In the forced-delete path, item metadata was unpacked via "for item in
unpacker" with an "except (TypeError, ValueError)" handler. msgpack's
FormatError/StackError are ValueError subclasses, so a real unpacking
failure was caught there and the (now broken) unpacker kept being reused
for the following chunks, making them all fail too - leaking their chunk
references.

Restructure the loop to use next(unpacker) so each failure mode gets a
tight handler:
- StopIteration: buffer drained, feed next chunk
- msgpack.UnpackException: corruption; in forced mode replace the unpacker
  with a fresh instance and skip the rest of the chunk
- TypeError/ValueError: only wraps Item processing (bad types yielded)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/borg/archive.py | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/borg/archive.py b/src/borg/archive.py
index 0fc411d3f..20cef9f67 100644
--- a/src/borg/archive.py
+++ b/src/borg/archive.py
@@ -1035,22 +1035,35 @@ Utilization of max. archive size: {csize_max:.0%}
                 data = self.key.decrypt(items_id, data)
                 unpacker.feed(data)
                 chunk_decref(items_id, stats)
-                try:
-                    for item in unpacker:
+                while True:
+                    try:
+                        item = next(unpacker)
+                    except StopIteration:
+                        # no more (complete) items in the buffer, feed the next chunk
+                        break
+                    except msgpack.UnpackException:
+                        # items metadata corrupted. the unpacker can't be reused after an
+                        # unpacking failure, so create a fresh one and skip the rest of this chunk.
+                        if forced == 0:
+                            raise
+                        error = True
+                        unpacker = msgpack.Unpacker(use_list=False)
+                        break
+                    try:
                         item = Item(internal_dict=item)
                         if 'chunks' in item:
                             part = not self.consider_part_files and 'part' in item
                             for chunk_id, size, csize in item.chunks:
                                 chunk_decref(chunk_id, stats, part=part)
-                except (TypeError, ValueError):
-                    # if items metadata spans multiple chunks and one chunk got dropped somehow,
-                    # it could be that unpacker yields bad types
-                    if forced == 0:
-                        raise
-                    error = True
+                    except (TypeError, ValueError):
+                        # if items metadata spans multiple chunks and one chunk got dropped somehow,
+                        # it could be that unpacker yields bad types
+                        if forced == 0:
+                            raise
+                        error = True
             if progress:
                 pi.finish()
-        except (msgpack.UnpackException, Repository.ObjectNotFound):
+        except Repository.ObjectNotFound:
             # items metadata corrupted
             if forced == 0:
                 raise