From fde9c57dc48df6ac58184c993c03198cfc3e9e96 Mon Sep 17 00:00:00 2001
From: Zawwar Sami <zawwarsami16@gmail.com>
Date: Sat, 13 Jun 2026 03:04:10 +0000
Subject: [PATCH 1/2] fix(client): handle bare dict/list annotations in
 construct_type

get_args() returns an empty tuple for an unparameterized `dict` or
`list` annotation, so the dict branch's two-value unpack raised
ValueError and the list branch's args[0] raised IndexError. Guard both
and fall back to `object` as the element type so values pass through
unchanged instead of crashing.

Fixes #1619, #1626
---
 src/anthropic/_models.py |  5 +++--
 tests/test_models.py     | 12 ++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/anthropic/_models.py b/src/anthropic/_models.py
index dc00516bc..ac1b212b1 100644
--- a/src/anthropic/_models.py
+++ b/src/anthropic/_models.py
@@ -647,7 +647,8 @@ def construct_type(*, value: object, type_: object, metadata: Optional[List[Any]
         if not is_mapping(value):
             return value
 
-        _, items_type = get_args(type_)  # Dict[_, items_type]
+        args = get_args(type_)
+        items_type = args[1] if len(args) >= 2 else object  # Dict[_, items_type]
         return {key: construct_type(value=item, type_=items_type) for key, item in value.items()}
 
     if (
@@ -668,7 +669,7 @@ def construct_type(*, value: object, type_: object, metadata: Optional[List[Any]
         if not is_list(value):
             return value
 
-        inner_type = args[0]  # List[inner_type]
+        inner_type = args[0] if args else object  # List[inner_type]
         return [construct_type(value=entry, type_=inner_type) for entry in value]
 
     if origin == float:
diff --git a/tests/test_models.py b/tests/test_models.py
index 195f23079..d7e5850fa 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -655,6 +655,18 @@ class Model(BaseModel):
     assert m.value == "foo"
 
 
+def test_bare_dict_annotation() -> None:
+    # a bare `dict` annotation (no type parameters) should not raise
+    m = construct_type(value={"key": "value", "n": 1}, type_=cast(Any, dict))
+    assert m == {"key": "value", "n": 1}
+
+
+def test_bare_list_annotation() -> None:
+    # a bare `list` annotation (no type parameters) should not raise
+    m = construct_type(value=["a", "b", 1], type_=cast(Any, list))
+    assert m == ["a", "b", 1]
+
+
 def test_discriminated_unions_invalid_data() -> None:
     class A(BaseModel):
         type: Literal["a"]

From 6302050ec85f10fc149e185bb4edd0cb01aa4a84 Mon Sep 17 00:00:00 2001
From: Zawwar Sami <zawwarsami16@gmail.com>
Date: Sat, 13 Jun 2026 03:04:15 +0000
Subject: [PATCH 2/2] fix(client): handle bare dict annotation in transform

A bare `dict` annotation (no type parameters) made both the sync and
async transform helpers index get_args(...)[1] on an empty tuple,
raising IndexError. Guard the lookup and fall back to `object` so the
mapping is passed through unchanged.

Fixes #1628
---
 src/anthropic/_utils/_transform.py | 6 ++++--
 tests/test_transform.py            | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/anthropic/_utils/_transform.py b/src/anthropic/_utils/_transform.py
index 1331da174..0229f3d5c 100644
--- a/src/anthropic/_utils/_transform.py
+++ b/src/anthropic/_utils/_transform.py
@@ -180,7 +180,8 @@ def _transform_recursive(
         return _transform_typeddict(data, stripped_type)
 
     if origin == dict and is_mapping(data):
-        items_type = get_args(stripped_type)[1]
+        args = get_args(stripped_type)
+        items_type = args[1] if len(args) >= 2 else object
         return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
 
     if (
@@ -348,7 +349,8 @@ async def _async_transform_recursive(
         return await _async_transform_typeddict(data, stripped_type)
 
     if origin == dict and is_mapping(data):
-        items_type = get_args(stripped_type)[1]
+        args = get_args(stripped_type)
+        items_type = args[1] if len(args) >= 2 else object
         return {key: _transform_recursive(value, annotation=items_type) for key, value in data.items()}
 
     if (
diff --git a/tests/test_transform.py b/tests/test_transform.py
index 513b09cac..406d838de 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -61,6 +61,13 @@ class Baz2(TypedDict):
     my_baz: Annotated[str, PropertyInfo(alias="myBaz")]
 
 
+@parametrize
+@pytest.mark.asyncio
+async def test_bare_dict_annotation(use_async: bool) -> None:
+    # a bare `dict` annotation (no type parameters) should pass values through unchanged
+    assert await transform({"key": "value", "n": 1}, cast(Any, dict), use_async) == {"key": "value", "n": 1}
+
+
 @parametrize
 @pytest.mark.asyncio
 async def test_recursive_typeddict(use_async: bool) -> None: