diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index 13b120de..f5903a5e 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "0.25.5"
+  ".": "0.25.6"
 }
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2931a180..c68f5952 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.25.6 (2024-04-18)
+
+Full Changelog: [v0.25.5...v0.25.6](https://github.com/anthropics/anthropic-sdk-python/compare/v0.25.5...v0.25.6)
+
+### Chores
+
+* **internal:** bump pyright to 1.1.359 ([#466](https://github.com/anthropics/anthropic-sdk-python/issues/466)) ([8088160](https://github.com/anthropics/anthropic-sdk-python/commit/808816044cb33499c45e12b609f7a7664c628c88))
+
 ## 0.25.5 (2024-04-17)
 
 Full Changelog: [v0.25.4...v0.25.5](https://github.com/anthropics/anthropic-sdk-python/compare/v0.25.4...v0.25.5)
diff --git a/pyproject.toml b/pyproject.toml
index 0d39e2bf..43447278 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "anthropic"
-version = "0.25.5"
+version = "0.25.6"
 description = "The official Python library for the anthropic API"
 dynamic = ["readme"]
 license = "MIT"
@@ -50,7 +50,7 @@ Repository = "https://github.com/anthropics/anthropic-sdk-python"
 managed = true
 # version pins are in requirements-dev.lock
 dev-dependencies = [
-    "pyright",
+    "pyright>=1.1.359",
     "mypy",
     "respx",
     "pytest",
diff --git a/requirements-dev.lock b/requirements-dev.lock
index 1b42bb70..de7b55f9 100644
--- a/requirements-dev.lock
+++ b/requirements-dev.lock
@@ -24,7 +24,7 @@ botocore==1.31.58
     # via anthropic
     # via boto3
     # via s3transfer
-botocore-stubs==1.34.69
+botocore-stubs==1.34.86
     # via boto3-stubs
 cachetools==5.3.3
     # via google-auth
@@ -94,7 +94,7 @@ pydantic==2.4.2
     # via anthropic
 pydantic-core==2.10.1
     # via pydantic
-pyright==1.1.353
+pyright==1.1.359
 pytest==7.1.1
     # via pytest-asyncio
 pytest-asyncio==0.21.1
@@ -129,9 +129,9 @@ tomli==2.0.1
     # via pytest
 tqdm==4.66.2
     # via huggingface-hub
-types-awscrt==0.20.5
+types-awscrt==0.20.9
     # via botocore-stubs
-types-s3transfer==0.10.0
+types-s3transfer==0.10.1
     # via boto3-stubs
 typing-extensions==4.8.0
     # via anthropic
diff --git a/src/anthropic/_models.py b/src/anthropic/_models.py
index ff93fbd8..ff3f54e2 100644
--- a/src/anthropic/_models.py
+++ b/src/anthropic/_models.py
@@ -378,7 +378,7 @@ def construct_type(*, value: object, type_: object) -> object:
 
     # unwrap `Annotated[T, ...]` -> `T`
     if is_annotated_type(type_):
-        meta = get_args(type_)[1:]
+        meta: tuple[Any, ...] = get_args(type_)[1:]
         type_ = extract_type_arg(type_, 0)
     else:
         meta = tuple()
diff --git a/src/anthropic/_utils/_utils.py b/src/anthropic/_utils/_utils.py
index fd3a8a4d..17904ce6 100644
--- a/src/anthropic/_utils/_utils.py
+++ b/src/anthropic/_utils/_utils.py
@@ -265,6 +265,8 @@ def wrapper(*args: object, **kwargs: object) -> object:
                     )
                     msg = f"Missing required arguments; Expected either {variations} arguments to be given"
                 else:
+                    assert len(variants) > 0
+
                     # TODO: this error message is not deterministic
                     missing = list(set(variants[0]) - given_params)
                     if len(missing) > 1:
diff --git a/src/anthropic/_version.py b/src/anthropic/_version.py
index 600308ee..264f9211 100644
--- a/src/anthropic/_version.py
+++ b/src/anthropic/_version.py
@@ -1,4 +1,4 @@
 # File generated from our OpenAPI spec by Stainless. See CONTRIBUTING.md for details.
 
 __title__ = "anthropic"
-__version__ = "0.25.5"  # x-release-please-version
+__version__ = "0.25.6"  # x-release-please-version