From 8b201bc55d1c303811b2168651d8c9d9c2827163 Mon Sep 17 00:00:00 2001
From: boulea7 <zln1905391059@163.com>
Date: Wed, 30 Sep 2026 02:44:19 +0800
Subject: [PATCH 1/2] Preserve wrapped converter return annotations in pipe

---
 docs/init.md             | 14 ++++++++++++++
 src/attr/_make.py        |  3 +--
 tests/test_converters.py | 30 ++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/docs/init.md b/docs/init.md
index 8d5f2610f..3a5f67901 100644
--- a/docs/init.md
+++ b/docs/init.md
@@ -386,6 +386,20 @@ If you need more control over the conversion process, you can wrap the converter
 C(x=410)
 ```
 
+Use {func}`attrs.converters.pipe` to apply converters in sequence.
+A final {class}`attrs.Converter` preserves the return annotation of its wrapped function.
+Tools can inspect that annotation on the pipeline:
+
+```{doctest}
+>>> import inspect
+>>> from attrs.converters import pipe
+>>> def to_int(value) -> int:
+...     return int(value)
+>>> converter = pipe(str, attrs.Converter(to_int))
+>>> inspect.signature(converter.__call__).return_annotation
+<class 'int'>
+```
+
 Or as a decorator
 
 ```{doctest}
diff --git a/src/attr/_make.py b/src/attr/_make.py
index afbca4635..6e1a58e54 100644
--- a/src/attr/_make.py
+++ b/src/attr/_make.py
@@ -20,7 +20,6 @@
 # having the thread-local in the globals here.
 from . import _compat, _config, setters
 from ._compat import (
-    PY_3_11_PLUS,
     PY_3_13_PLUS,
     _AnnotationExtractor,
     _get_annotations,
@@ -3449,7 +3448,7 @@ def pipe_converter(val):
             pipe_converter.__annotations__["val"] = t
 
         last = converters[-1]
-        if not PY_3_11_PLUS and isinstance(last, Converter):
+        if isinstance(last, Converter):
             last = last.__call__
 
         # Get return type from last converter.
diff --git a/tests/test_converters.py b/tests/test_converters.py
index 5726ae210..8a82b3633 100644
--- a/tests/test_converters.py
+++ b/tests/test_converters.py
@@ -4,6 +4,7 @@
 Tests for `attr.converters`.
 """
 
+import inspect
 import pickle
 
 import pytest
@@ -298,6 +299,35 @@ class C:
             ).get_return_type()
         )
 
+    def test_wrapped_annotation_when_converter_signature_unavailable(
+        self, monkeypatch
+    ):
+        """
+        A pipe keeps the last Converter's return type even if its instance
+        signature cannot be inspected.
+        """
+
+        def last(value) -> bool:
+            return bool(value)
+
+        wrapped = Converter(last)
+        original_signature = inspect.signature
+
+        def signature_without_converter_instances(obj, *args, **kwargs):
+            if isinstance(obj, Converter):
+                raise TypeError("Converter instance signature unavailable")
+
+            return original_signature(obj, *args, **kwargs)
+
+        with monkeypatch.context() as patch:
+            patch.setattr(
+                inspect, "signature", signature_without_converter_instances
+            )
+            converted = pipe(wrapped)
+
+        assert True is converted(5, None, None)
+        assert bool is inspect.signature(converted.__call__).return_annotation
+
 
 class TestOptionalPipe:
     def test_optional(self):

From a25520700d01fbafe74c192267888f3d15c98b41 Mon Sep 17 00:00:00 2001
From: boulea7 <zln1905391059@163.com>
Date: Wed, 30 Sep 2026 03:07:18 +0800
Subject: [PATCH 2/2] Add news fragment for pipe annotation fix

---
 changelog.d/1631.change.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/1631.change.md

diff --git a/changelog.d/1631.change.md b/changelog.d/1631.change.md
new file mode 100644
index 000000000..f5f5d4918
--- /dev/null
+++ b/changelog.d/1631.change.md
@@ -0,0 +1 @@
+`attrs.converters.pipe()` now preserves the return annotation of a final `attrs.Converter` when Python cannot inspect the converter instance's signature, including early Python 3.11 releases.