diff --git a/src/anthropic/resources/beta/messages/messages.py b/src/anthropic/resources/beta/messages/messages.py
index ed10bd7a..fcc90065 100644
--- a/src/anthropic/resources/beta/messages/messages.py
+++ b/src/anthropic/resources/beta/messages/messages.py
@@ -1033,6 +1033,9 @@ def create(
             stream_cls=Stream[BetaRawMessageStreamEvent],
         )
 
+    # This overload should be listed first to prioritize it over generic overload
+    # so calls with Omit() resolve to ParsedBetaMessage[None] not ParsedBetaMessage[Omit]
+    @overload
     def parse(
         self,
         *,
@@ -1043,7 +1046,7 @@ def parse(
         context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
         mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
         metadata: BetaMetadataParam | Omit = omit,
-        output_format: Optional[type[ResponseFormatT]] | Omit = omit,
+        output_format: None | Omit = omit,
         service_tier: Literal["auto", "standard_only"] | Omit = omit,
         stop_sequences: SequenceNotStr[str] | Omit = omit,
         stream: Literal[False] | Literal[True] | Omit = omit,
@@ -1061,7 +1064,100 @@ def parse(
         extra_query: Query | None = None,
         extra_body: Body | None = None,
         timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
-    ) -> ParsedBetaMessage[ResponseFormatT]:
+    ) -> ParsedBetaMessage[None]: ...
+
+    @overload
+    def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: type[ResponseFormatT],
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[ResponseFormatT]: ...
+
+    @overload
+    def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: ResponseFormatT,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[ResponseFormatT]: ...
+
+    def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        # TODO: Use TypeForm[ResponseFormatT] instead when PEP 747 is supported by mypy
+        output_format: None | type[ResponseFormatT] | ResponseFormatT | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[ResponseFormatT] | ParsedBetaMessage[None]:
         if not stream and not is_given(timeout) and self._client.timeout == DEFAULT_TIMEOUT:
             timeout = self._client._calculate_nonstreaming_timeout(
                 max_tokens, MODEL_NONSTREAMING_TOKENS.get(model, None)
@@ -1338,6 +1434,9 @@ def tool_runner(
             max_iterations=max_iterations if is_given(max_iterations) else None,
         )
 
+    # This overload should be listed first to prioritize it over generic overload
+    # so calls with Omit() resolve to ParsedBetaMessage[None] not ParsedBetaMessage[Omit]
+    @overload
     def stream(
         self,
         *,
@@ -1348,7 +1447,94 @@ def stream(
         context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
         mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
         metadata: BetaMetadataParam | Omit = omit,
-        output_format: Optional[type[ResponseFormatT]] | Omit = omit,
+        output_format: None | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaMessageStreamManager[None]: ...
+    @overload
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: type[ResponseFormatT],
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaMessageStreamManager[ResponseFormatT]: ...
+    @overload
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: ResponseFormatT,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaMessageStreamManager[ResponseFormatT]: ...
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        # TODO: Use TypeForm[ResponseFormatT] instead when PEP 747 is supported by mypy
+        output_format: None | type[ResponseFormatT] | ResponseFormatT | Omit = omit,
         service_tier: Literal["auto", "standard_only"] | Omit = omit,
         stop_sequences: SequenceNotStr[str] | Omit = omit,
         system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
@@ -2646,6 +2832,9 @@ async def create(
             stream_cls=AsyncStream[BetaRawMessageStreamEvent],
         )
 
+    # This overload should be listed first to prioritize it over generic overload
+    # so calls with Omit() resolve to ParsedBetaMessage[None] not ParsedBetaMessage[Omit]
+    @overload
     async def parse(
         self,
         *,
@@ -2656,7 +2845,98 @@ async def parse(
         context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
         mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
         metadata: BetaMetadataParam | Omit = omit,
-        output_format: Optional[type[ResponseFormatT]] | Omit = omit,
+        output_format: None | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[None]: ...
+    @overload
+    async def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: type[ResponseFormatT],
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[ResponseFormatT]: ...
+    @overload
+    async def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: ResponseFormatT,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        stream: Literal[False] | Literal[True] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> ParsedBetaMessage[ResponseFormatT]: ...
+
+    async def parse(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        metadata: BetaMetadataParam | Omit = omit,
+        # TODO: Use TypeForm[ResponseFormatT] instead when PEP 747 is supported by mypy
+        output_format: None | type[ResponseFormatT] | ResponseFormatT | Omit = omit,
         service_tier: Literal["auto", "standard_only"] | Omit = omit,
         stop_sequences: SequenceNotStr[str] | Omit = omit,
         stream: Literal[False] | Literal[True] | Omit = omit,
@@ -2950,6 +3230,9 @@ def tool_runner(
             max_iterations=max_iterations if is_given(max_iterations) else None,
         )
 
+    # This overload should be listed first to prioritize it over generic overload
+    # so calls with Omit() resolve to ParsedBetaMessage[None] not ParsedBetaMessage[Omit]
+    @overload
     def stream(
         self,
         *,
@@ -2957,7 +3240,95 @@ def stream(
         messages: Iterable[BetaMessageParam],
         model: ModelParam,
         metadata: BetaMetadataParam | Omit = omit,
-        output_format: Optional[type[ResponseFormatT]] | Omit = omit,
+        output_format: None | Omit = omit,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaAsyncMessageStreamManager[None]: ...
+    @overload
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: type[ResponseFormatT],
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaAsyncMessageStreamManager[ResponseFormatT]: ...
+    @overload
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        metadata: BetaMetadataParam | Omit = omit,
+        output_format: ResponseFormatT,
+        container: Optional[message_create_params.Container] | Omit = omit,
+        context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
+        mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
+        service_tier: Literal["auto", "standard_only"] | Omit = omit,
+        stop_sequences: SequenceNotStr[str] | Omit = omit,
+        system: Union[str, Iterable[BetaTextBlockParam]] | Omit = omit,
+        temperature: float | Omit = omit,
+        thinking: BetaThinkingConfigParam | Omit = omit,
+        tool_choice: BetaToolChoiceParam | Omit = omit,
+        tools: Iterable[BetaToolUnionParam] | Omit = omit,
+        top_k: int | Omit = omit,
+        top_p: float | Omit = omit,
+        betas: List[AnthropicBetaParam] | Omit = omit,
+        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+        # The extra values given here take precedence over values defined on the client or passed to this method.
+        extra_headers: Headers | None = None,
+        extra_query: Query | None = None,
+        extra_body: Body | None = None,
+        timeout: float | httpx.Timeout | None | NotGiven = NOT_GIVEN,
+    ) -> BetaAsyncMessageStreamManager[ResponseFormatT]: ...
+
+    def stream(
+        self,
+        *,
+        max_tokens: int,
+        messages: Iterable[BetaMessageParam],
+        model: ModelParam,
+        metadata: BetaMetadataParam | Omit = omit,
+        # TODO: Use TypeForm[ResponseFormatT] instead when PEP 747 is supported by mypy
+        output_format: None | type[ResponseFormatT] | ResponseFormatT | Omit = omit,
         container: Optional[message_create_params.Container] | Omit = omit,
         context_management: Optional[BetaContextManagementConfigParam] | Omit = omit,
         mcp_servers: Iterable[BetaRequestMCPServerURLDefinitionParam] | Omit = omit,
diff --git a/src/anthropic/types/beta/message_create_params.py b/src/anthropic/types/beta/message_create_params.py
index 1202c91b..9ada27f0 100644
--- a/src/anthropic/types/beta/message_create_params.py
+++ b/src/anthropic/types/beta/message_create_params.py
@@ -302,7 +302,7 @@ class MessageCreateParamsBase(TypedDict, total=False):
 
 
 class ParseMessageCreateParamsBase(MessageCreateParamsBase, Generic[ResponseFormatT]):
-    output_format: type[ResponseFormatT]  # type: ignore[misc]
+    output_format: ResponseFormatT  # type: ignore[misc]
 
 
 class OutputFormat(TypedDict, total=False):
diff --git a/tests/lib/_parse/__init__.py b/tests/lib/_parse/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/lib/_parse/test_beta_messages.py b/tests/lib/_parse/test_beta_messages.py
new file mode 100644
index 00000000..edd107c7
--- /dev/null
+++ b/tests/lib/_parse/test_beta_messages.py
@@ -0,0 +1,77 @@
+from __future__ import annotations
+
+from typing import Literal
+
+import pytest
+from respx import MockRouter
+from pydantic import BaseModel
+from inline_snapshot import snapshot
+
+from anthropic import AsyncAnthropic, _compat
+
+from ..utils import print_obj
+from ..snapshots import make_async_snapshot_request
+
+
+@pytest.mark.skipif(_compat.PYDANTIC_V1, reason="tool runner not supported with pydantic v1")
+class TestAsyncMessages:
+    async def test_simple_parse(
+        self, async_client: AsyncAnthropic, respx_mock: MockRouter, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        class ContactInfo(BaseModel):
+            name: str
+            email: str
+            plan_interest: str
+            demo_requested: bool
+
+        resp = await make_async_snapshot_request(
+            lambda cl: cl.beta.messages.parse(
+                model="claude-sonnet-4-5",
+                messages=[
+                    {
+                        "role": "user",
+                        "content": (
+                            "Extract the key information from this email: John Smith (john@example.com) is "
+                            "interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm."
+                        ),
+                    }
+                ],
+                max_tokens=1024,
+                output_format=ContactInfo,
+            ),
+            content_snapshot=snapshot(
+                '{"model": "claude-sonnet-4-5-20250929", "id": "msg_01PpBVKyHCmDmjk57fYhRsMk", "type": "message", "role": "assistant", "content": [{"type": "text", "text": "{\\"name\\": \\"John Smith\\", \\"email\\": \\"john@example.com\\", \\"plan_interest\\": \\"Enterprise\\", \\"demo_requested\\": true}"}], "stop_reason": "end_turn", "stop_sequence": null, "usage": {"input_tokens": 303, "cache_creation_input_tokens": 0, "cache_read_input_tokens": 0, "cache_creation": {"ephemeral_5m_input_tokens": 0, "ephemeral_1h_input_tokens": 0}, "output_tokens": 35, "service_tier": "standard"}}'
+            ),
+            respx_mock=respx_mock,
+            mock_client=async_client,
+            path="/v1/messages?beta=true",
+        )
+        assert print_obj(resp, monkeypatch) == snapshot(
+            "ParsedBetaMessage(container=None, content=[ParsedBetaTextBlock(citations=None, parsed_output=ContactInfo(demo_requested=True, email='john@example.com', name='John Smith', plan_interest='Enterprise'), text='{\"name\": \"John Smith\", \"email\": \"john@example.com\", \"plan_interest\": \"Enterprise\", \"demo_requested\": true}', type='text')], context_management=None, id='msg_01PpBVKyHCmDmjk57fYhRsMk', model='claude-sonnet-4-5-20250929', role='assistant', stop_reason='end_turn', stop_sequence=None, type='message', usage=BetaUsage(cache_creation=BetaCacheCreation(ephemeral_1h_input_tokens=0, ephemeral_5m_input_tokens=0), cache_creation_input_tokens=0, cache_read_input_tokens=0, input_tokens=303, output_tokens=35, server_tool_use=None, service_tier='standard'))\n"
+        )
+
+    async def test_special_types(
+        self, async_client: AsyncAnthropic, respx_mock: MockRouter, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        resp = await make_async_snapshot_request(
+            lambda cl: cl.beta.messages.parse(
+                model="claude-sonnet-4-5",
+                messages=[
+                    {
+                        "role": "user",
+                        "content": "Which programming language is better for data science, Python or JavaScript?",
+                    }
+                ],
+                max_tokens=1024,
+                output_format=Literal["Python", "Typescript"],
+            ),
+            content_snapshot=snapshot(
+                '{"model": "claude-sonnet-4-5-20250929", "id": "msg_015CQWZ6XgLgvZpALgDXQQR5", "type": "message", "role": "assistant", "content": [{"type": "text", "text": "\\"Python\\""}], "stop_reason": "end_turn", "stop_sequence": null, "usage": {"input_tokens": 129, "cache_creation_input_tokens": 0, "cache_read_input_tokens": 0, "cache_creation": {"ephemeral_5m_input_tokens": 0, "ephemeral_1h_input_tokens": 0}, "output_tokens": 6, "service_tier": "standard"}}'
+            ),
+            respx_mock=respx_mock,
+            mock_client=async_client,
+            path="/v1/messages?beta=true",
+        )
+        assert print_obj(resp, monkeypatch) == snapshot(
+            "ParsedBetaMessage(container=None, content=[ParsedBetaTextBlock(citations=None, parsed_output='Python', text='\"Python\"', type='text')], context_management=None, id='msg_015CQWZ6XgLgvZpALgDXQQR5', model='claude-sonnet-4-5-20250929', role='assistant', stop_reason='end_turn', stop_sequence=None, type='message', usage=BetaUsage(cache_creation=BetaCacheCreation(ephemeral_1h_input_tokens=0, ephemeral_5m_input_tokens=0), cache_creation_input_tokens=0, cache_read_input_tokens=0, input_tokens=129, output_tokens=6, server_tool_use=None, service_tier='standard'))\n"
+        )
diff --git a/tests/lib/snapshots.py b/tests/lib/snapshots.py
index 510fceb0..7b3158d4 100644
--- a/tests/lib/snapshots.py
+++ b/tests/lib/snapshots.py
@@ -161,7 +161,8 @@ async def _on_response(response: httpx.Response) -> None:
         )
     else:
         responses = get_snapshot_value(content_snapshot)
-        assert is_list(responses)
+        if not is_list(responses):
+            responses = [responses]
 
         curr = 0