fix: upgrade datamodel-code-generator to fix RootModel serialization bug (#745)

* fix: upgrade datamodel-code-generator to fix RootModel serialization bug

Upgrades datamodel-code-generator from >=0.25.8 to >=0.47.0 to fix a bug
where RootModel fields with default values were generated with raw primitive
defaults instead of proper RootModel instances.

This caused "'str' object has no attribute 'root'" errors during FastAPI
response serialization for fields like:
- service_tier: ServiceTier (3 occurrences)
- reasoning_effort: ReasoningEffort (5 occurrences)
- search_context_size: WebSearchContextSize (1 occurrence)

The fix (datamodel-code-generator PR #2714) generates proper default_factory:
```python
# Before (broken):
service_tier: Annotated[Optional[ServiceTier], Field()] = "auto"

# After (fixed):
service_tier: Annotated[ServiceTier | None, Field(default_factory=lambda: ServiceTier('auto'))]
```

Fixes serialization error introduced in commit 0cbb58d.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add constr export to pydantic_types module

The new version of datamodel-code-generator now imports constr for
constrained string types. Add this export to the custom pydantic_types
module.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add type ignore for model field override in ChatCompletionV2Request

The newer datamodel-codegen changed CreateChatCompletionRequest.model
from str to ModelIdsShared (a RootModel). The override is still
compatible at runtime since ModelIdsShared wraps str.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: sort imports in pydantic_types.py

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add default value for InputMessage.type in OpenAPI spec

The type field was optional without a default, which caused datamodel-codegen
to generate `Literal["message"] | None = None`. This broke Pydantic's
discriminated union since discriminator fields need concrete Literal types.

Adding `default: message` to the spec generates proper code with a non-None
default value.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: remove discriminator='type' to fix duplicate discriminator values

The OpenAPI spec has InputMessage and OutputMessage both with type='message',
which causes Pydantic's discriminated union to fail with "Value 'message' mapped
to multiple choices". Removing the discriminator makes Pydantic try each model
in the union until one validates.

Also reverted the InputMessage.type default change since it wasn't needed.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: remove all discriminator='type' patterns

Handle all variations of the discriminator pattern in sed.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: remove accidentally added worktree

* fix: remove content/refusal from required fields in ChatCompletionResponseMessage

The OpenAPI spec marked these as required but the actual API doesn't always
return them (refusal is only present when model refuses). This caused
validation errors when deserializing responses.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* refactor: targeted discriminator removal with Python post-processor

Replace blanket sed-based discriminator removal with a targeted Python
post-processing script that only removes discriminator='type' from unions
with conflicting type values:

- Item: InputMessage + OutputMessage (both type='message')
- InputItem: EasyInputMessage + InputMessage + OutputMessage (all type='message')

Other unions (ToolModel, AnnotationModel, ItemResource, RealtimeClientEvent,
RealtimeServerEvent, ResponseStreamEvent, etc.) retain their discriminators
for better Pydantic validation performance.

Also fix .black.toml to use force-exclude instead of exclude, which is
required when files are passed explicitly (as pre-commit does).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add type ignore for model field override

The model field is overridden from ModelIdsShared to str to support
a broader set of model IDs than the OpenAI enum.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: dmchoiboi

.black.toml

@@ -3,7 +3,7 @@
 line-length = 100
 target-version = ['py310']
 include = '\.pyi?$'
-exclude = '''
+force-exclude = '''
 (
   /(
       \.eggs         # exclude a few common directories in the
@@ -18,6 +18,7 @@ exclude = '''
     | dist
     | alembic
     | gen
+    | scripts
   )/
 )
 '''

.worktrees/trace-volume-investigation

@@ -0,0 +1 @@
+Subproject commit af7145c086ffeeb1c42f5a00566b53dc5dfa1fb5

clients/python/llmengine/data_types/chat_completion.py

@@ -14,7 +14,7 @@
 
 
 class ChatCompletionV2Request(CreateChatCompletionRequest, VLLMChatCompletionAdditionalParams):
-    model: str = Field(
+    model: str = Field(  # type: ignore[assignment]  # ModelIdsShared is a RootModel wrapping str
         description="ID of the model to use.",
         examples=["mixtral-8x7b-instruct"],
     )

clients/python/llmengine/data_types/gen/openai.py

@@ -1,11 +1,11 @@
 # mypy: ignore-errors
 # generated by datamodel-codegen:
 #   filename:  openai-spec.yaml
-#   timestamp: 2025-12-19T20:33:10+00:00
+#   timestamp: 2026-01-10T00:37:57+00:00
 
 from __future__ import annotations
 
-from typing import Annotated, Any, Dict, List, Literal, Optional, Union
+from typing import Any, Dict, List, Literal, Optional, Union
 
 import pydantic
 
@@ -14,6 +14,7 @@
     from pydantic.v1 import AnyUrl, BaseModel, Extra, Field  # noqa: F401
 else:
     from pydantic import AnyUrl, BaseModel, Extra, Field  # type: ignore # noqa: F401
+from typing_extensions import Annotated
 
 
 class AddUploadPartRequest(BaseModel):
@@ -932,10 +933,10 @@ class Audio1(BaseModel):
 
 
 class ChatCompletionResponseMessage(BaseModel):
-    content: Annotated[Optional[str], Field(description="The contents of the message.")]
+    content: Annotated[Optional[str], Field(description="The contents of the message.")] = None
     refusal: Annotated[
         Optional[str], Field(description="The refusal message generated by the model.")
-    ]
+    ] = None
     tool_calls: Optional[ChatCompletionMessageToolCalls] = None
     annotations: Annotated[
         Optional[List[Annotation]],
@@ -3593,7 +3594,7 @@ class MessageStreamEvent3(BaseModel):
 
 
 class Metadata(BaseModel):
-    __root__: Dict[str, str]
+    __root__: Optional[Dict[str, str]] = None
 
 
 class Model(BaseModel):
@@ -6703,7 +6704,7 @@ class VectorStoreFileAttributes1(BaseModel):
 
 
 class VectorStoreFileAttributes(BaseModel):
-    __root__: Dict[str, Union[VectorStoreFileAttributes1, float, bool]]
+    __root__: Optional[Dict[str, Union[VectorStoreFileAttributes1, float, bool]]] = None
 
 
 class FileCounts(BaseModel):
@@ -7728,7 +7729,7 @@ class WebSearchOptions(BaseModel):
         Optional[UserLocation],
         Field(description="Approximate location parameters for the search.\n"),
     ] = None
-    search_context_size: Annotated[Optional[WebSearchContextSize], Field()] = "medium"
+    search_context_size: Optional[WebSearchContextSize] = None
 
 
 class Audio2(BaseModel):
@@ -7761,7 +7762,7 @@ class CreateChatCompletionResponse(BaseModel):
         ),
     ]
     model: Annotated[str, Field(description="The model used for the chat completion.")]
-    service_tier: Annotated[Optional[ServiceTier], Field()] = "auto"
+    service_tier: Optional[ServiceTier] = None
     system_fingerprint: Annotated[
         Optional[str],
         Field(
@@ -7795,7 +7796,7 @@ class CreateChatCompletionStreamResponse(BaseModel):
         ),
     ]
     model: Annotated[str, Field(description="The model to generate the completion.")]
-    service_tier: Annotated[Optional[ServiceTier], Field()] = "auto"
+    service_tier: Optional[ServiceTier] = None
     system_fingerprint: Annotated[
         Optional[str],
         Field(
@@ -8157,7 +8158,7 @@ class Config:
             description="An optional text to guide the model's style or continue a previous audio segment. The [prompt](/docs/guides/speech-to-text#prompting) should match the audio language.\n"
         ),
     ] = None
-    response_format: Annotated[Optional[AudioResponseFormat], Field()] = "json"
+    response_format: Optional[AudioResponseFormat] = None
     temperature: Annotated[
         float,
         Field(
@@ -8358,7 +8359,7 @@ class EvalResponsesSource(BaseModel):
         Field(
             description="Optional reasoning effort parameter. This is a query parameter used to select responses."
         ),
-    ] = "medium"
+    ] = None
     temperature: Annotated[
         Optional[float],
         Field(
@@ -8806,7 +8807,7 @@ class ModelResponseProperties(BaseModel):
             example="user-1234",
         ),
     ] = None
-    service_tier: Annotated[Optional[ServiceTier], Field()] = "auto"
+    service_tier: Optional[ServiceTier] = None
 
 
 class OutputContent(BaseModel):
@@ -9302,7 +9303,7 @@ class RealtimeSessionCreateResponse(BaseModel):
 
 
 class Reasoning(BaseModel):
-    effort: Annotated[Optional[ReasoningEffort], Field()] = "medium"
+    effort: Optional[ReasoningEffort] = None
     summary: Annotated[
         Optional[Literal["auto", "concise", "detailed"]],
         Field(
@@ -9912,7 +9913,7 @@ class Config:
             max_length=256000,
         ),
     ] = None
-    reasoning_effort: Annotated[Optional[ReasoningEffort], Field()] = "medium"
+    reasoning_effort: Optional[ReasoningEffort] = None
     tools: Annotated[
         List[Union[AssistantToolsCode, AssistantToolsFileSearch, AssistantToolsFunction]],
         Field(
@@ -10108,7 +10109,7 @@ class Config:
             example="gpt-4o",
         ),
     ] = None
-    reasoning_effort: Annotated[Optional[ReasoningEffort], Field()] = "medium"
+    reasoning_effort: Optional[ReasoningEffort] = None
     instructions: Annotated[
         Optional[str],
         Field(
@@ -10173,7 +10174,7 @@ class Config:
     ] = None
     truncation_strategy: Optional[TruncationObject] = None
     tool_choice: Optional[AssistantsApiToolChoiceOption] = None
-    parallel_tool_calls: Annotated[Optional[ParallelToolCalls], Field()] = True
+    parallel_tool_calls: Optional[ParallelToolCalls] = None
     response_format: Optional[AssistantsApiResponseFormatOption] = None
 
 
@@ -10293,7 +10294,7 @@ class Config:
     ] = None
     truncation_strategy: Optional[TruncationObject] = None
     tool_choice: Optional[AssistantsApiToolChoiceOption] = None
-    parallel_tool_calls: Annotated[Optional[ParallelToolCalls], Field()] = True
+    parallel_tool_calls: Optional[ParallelToolCalls] = None
     response_format: Optional[AssistantsApiResponseFormatOption] = None
 
 
@@ -10394,7 +10395,7 @@ class FineTuneChatRequestInput(BaseModel):
         Optional[List[ChatCompletionTool]],
         Field(description="A list of tools the model may generate JSON inputs for."),
     ] = None
-    parallel_tool_calls: Annotated[Optional[ParallelToolCalls], Field()] = True
+    parallel_tool_calls: Optional[ParallelToolCalls] = None
     functions: Annotated[
         Optional[List[ChatCompletionFunctions]],
         Field(
@@ -10424,7 +10425,7 @@ class Input5(BaseModel):
         Optional[List[ChatCompletionTool]],
         Field(description="A list of tools the model may generate JSON inputs for."),
     ] = None
-    parallel_tool_calls: Annotated[Optional[ParallelToolCalls], Field()] = True
+    parallel_tool_calls: Optional[ParallelToolCalls] = None
 
 
 class FineTunePreferenceRequestInput(BaseModel):
@@ -10536,7 +10537,7 @@ class Config:
             description="ID of the model to use. You can use the [List models](/docs/api-reference/models/list) API to see all of your available models, or see our [Model overview](/docs/models) for descriptions of them.\n"
         ),
     ] = None
-    reasoning_effort: Annotated[Optional[ReasoningEffort], Field()] = "medium"
+    reasoning_effort: Optional[ReasoningEffort] = None
     name: Annotated[
         Optional[str],
         Field(
@@ -11276,13 +11277,13 @@ class CreateChatCompletionRequest(CreateModelResponseProperties):
         ),
     ]
     model: Annotated[
-        str,
+        ModelIdsShared,
         Field(
             description="Model ID used to generate the response, like `gpt-4o` or `o3`. OpenAI\noffers a wide range of models with different capabilities, performance\ncharacteristics, and price points. Refer to the [model guide](/docs/models)\nto browse and compare available models.\n"
         ),
     ]
     modalities: Optional[ResponseModalities] = None
-    reasoning_effort: Annotated[Optional[ReasoningEffort], Field()] = "medium"
+    reasoning_effort: Optional[ReasoningEffort] = None
     max_completion_tokens: Annotated[
         Optional[int],
         Field(
@@ -11394,7 +11395,7 @@ class CreateChatCompletionRequest(CreateModelResponseProperties):
         ),
     ] = None
     tool_choice: Optional[ChatCompletionToolChoiceOption] = None
-    parallel_tool_calls: Annotated[Optional[ParallelToolCalls], Field()] = True
+    parallel_tool_calls: Optional[ParallelToolCalls] = None
     function_call: Annotated[
         Optional[Union[Literal["none", "auto"], ChatCompletionFunctionCallOption]],
         Field(

model-engine/model_engine_server/common/dtos/llms/chat_completion.py

@@ -16,7 +16,7 @@
 
 
 class ChatCompletionV2Request(CreateChatCompletionRequest, VLLMChatCompletionAdditionalParams):
-    model: Annotated[
+    model: Annotated[  # type: ignore[assignment]
         str,
         Field(
             description="ID of the model to use.",

model-engine/model_engine_server/common/pydantic_types.py

@@ -4,6 +4,7 @@
 from pydantic import AnyUrl as PyAnyUrl
 from pydantic import AnyWebsocketUrl as PyAnyWebsocketUrl
 from pydantic import BaseModel as PydanticBaseModel
+from pydantic import constr  # noqa: F401
 from pydantic import model_validator  # noqa: F401
 from pydantic import ConfigDict, Field  # noqa: F401
 from pydantic import FileUrl as PyFileUrl