From 8bdc6c246ac31fe20582fdea446ae26c6d4d0064 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 20 May 2026 08:39:41 +0000
Subject: [PATCH 1/3] Initial plan


From 3e1ab431718cbc17e3576973ae0c697f9f7516ee Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 20 May 2026 08:42:30 +0000
Subject: [PATCH 2/3] Change DEFAULT_RECURSE_LIMIT from 511 to 1024 and add
 nest_limit test

Agent-Logs-Url: https://github.com/msgpack/msgpack-python/sessions/d5bc8a6a-e14e-4de3-b55f-4206dc3ca170

Co-authored-by: methane <199592+methane@users.noreply.github.com>
---
 msgpack/_packer.pyx |  2 +-
 msgpack/fallback.py |  2 +-
 test/test_limits.py | 18 ++++++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/msgpack/_packer.pyx b/msgpack/_packer.pyx
index 94d1462c..4d0d2d21 100644
--- a/msgpack/_packer.pyx
+++ b/msgpack/_packer.pyx
@@ -38,7 +38,7 @@ cdef extern from "pack.h":
     int msgpack_pack_timestamp(msgpack_packer* x, long long seconds, unsigned long nanoseconds) except -1
 
 
-cdef int DEFAULT_RECURSE_LIMIT=511
+cdef int DEFAULT_RECURSE_LIMIT=1024
 cdef long long ITEM_LIMIT = (2**32)-1
 
 
diff --git a/msgpack/fallback.py b/msgpack/fallback.py
index d71bbfc7..1f2daf7b 100644
--- a/msgpack/fallback.py
+++ b/msgpack/fallback.py
@@ -52,7 +52,7 @@ def newlist_hint(size):
 TYPE_BIN = 4
 TYPE_EXT = 5
 
-DEFAULT_RECURSE_LIMIT = 511
+DEFAULT_RECURSE_LIMIT = 1024
 
 
 def _check_type_strict(obj, t, type=type, tuple=tuple):
diff --git a/test/test_limits.py b/test/test_limits.py
index 9b92b4d9..9774d741 100644
--- a/test/test_limits.py
+++ b/test/test_limits.py
@@ -153,6 +153,24 @@ def test_auto_max_array_len():
         unpacker.unpack()
 
 
+def test_nest_limit_1024():
+    import sys
+
+    # Build a list nested 1024 levels deep
+    d = None
+    for _ in range(1024):
+        d = [d]
+
+    # Temporarily raise Python's recursion limit so packing 1024 levels succeeds
+    old_limit = sys.getrecursionlimit()
+    sys.setrecursionlimit(max(old_limit, 10000))
+    try:
+        packed = packb(d)
+        assert unpackb(packed) == d
+    finally:
+        sys.setrecursionlimit(old_limit)
+
+
 def test_auto_max_map_len():
     # len(packed) == 6 -> max_map_len == 3
     packed = b"\xde\x00\x04zzz"

From 30e46c8d14e76a54fda419788fe377bb5386c019 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 20 May 2026 14:31:14 +0000
Subject: [PATCH 3/3] Fix test_nest_limit_1024: use iterative comparison to
 avoid C-level recursion limit

Agent-Logs-Url: https://github.com/msgpack/msgpack-python/sessions/b5597430-50ea-4c37-b94f-7b4c9ed4142c

Co-authored-by: methane <199592+methane@users.noreply.github.com>
---
 test/test_limits.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/test/test_limits.py b/test/test_limits.py
index 9774d741..468c1c36 100644
--- a/test/test_limits.py
+++ b/test/test_limits.py
@@ -166,10 +166,16 @@ def test_nest_limit_1024():
     sys.setrecursionlimit(max(old_limit, 10000))
     try:
         packed = packb(d)
-        assert unpackb(packed) == d
+        result = unpackb(packed)
     finally:
         sys.setrecursionlimit(old_limit)
 
+    # Verify structure iteratively to avoid hitting C-level recursion limit in ==
+    for _ in range(1024):
+        assert isinstance(result, list) and len(result) == 1
+        result = result[0]
+    assert result is None
+
 
 def test_auto_max_map_len():
     # len(packed) == 6 -> max_map_len == 3