koxudaxi · koxudaxi · Jul 1, 2026 · Jun 30, 2026
diff --git a/docs/architecture.md b/docs/architecture.md
@@ -154,16 +154,16 @@ classDiagram
 
 | Config model | Field count | Purpose |
 | --- | ---: | --- |
-| `BaseGenerateConfig` | 138 | Shared generation options. |
-| `GenerateConfig` | 153 | Public `generate()` configuration. |
-| `ParserConfig` | 134 | Base parser dependency injection and parser options. |
-| `JSONSchemaParserConfig` | 136 | JSON Schema parser options. |
-| `OpenAPIParserConfig` | 142 | OpenAPI-specific parser options. |
-| `AsyncAPIParserConfig` | 143 | AsyncAPI-specific parser options. |
-| `XMLSchemaParserConfig` | 137 | XML Schema-specific parser options. |
-| `ProtobufParserConfig` | 137 | Protocol Buffers-specific parser options. |
-| `AvroParserConfig` | 136 | Avro-specific parser options. |
-| `GraphQLParserConfig` | 137 | GraphQL-specific parser options. |
+| `BaseGenerateConfig` | 139 | Shared generation options. |
+| `GenerateConfig` | 154 | Public `generate()` configuration. |
+| `ParserConfig` | 135 | Base parser dependency injection and parser options. |
+| `JSONSchemaParserConfig` | 137 | JSON Schema parser options. |
+| `OpenAPIParserConfig` | 143 | OpenAPI-specific parser options. |
+| `AsyncAPIParserConfig` | 144 | AsyncAPI-specific parser options. |
+| `XMLSchemaParserConfig` | 138 | XML Schema-specific parser options. |
+| `ProtobufParserConfig` | 138 | Protocol Buffers-specific parser options. |
+| `AvroParserConfig` | 137 | Avro-specific parser options. |
+| `GraphQLParserConfig` | 138 | GraphQL-specific parser options. |
 
 ### Formatter Names
 

diff --git a/docs/cli-reference/index.md b/docs/cli-reference/index.md
@@ -11,7 +11,7 @@ This documentation is auto-generated from test cases.
 | 📁 [Base Options](base-options.md) | 12 | Input/output configuration |
 | 🔧 [Typing Customization](typing-customization.md) | 30 | Type annotation and import behavior |
 | 🏷️ [Field Customization](field-customization.md) | 27 | Field naming and docstring behavior |
-| 🏗️ [Model Customization](model-customization.md) | 43 | Model generation behavior |
+| 🏗️ [Model Customization](model-customization.md) | 44 | Model generation behavior |
 | 🎨 [Template Customization](template-customization.md) | 25 | Output formatting and custom rendering |
 | 📘 [OpenAPI-only Options](openapi-only-options.md) | 8 | OpenAPI-specific features |
 | 📋 [GraphQL-only Options](graphql-only-options.md) | 1 |  |
@@ -225,6 +225,7 @@ This documentation is auto-generated from test cases.
 - [`--use-generic-base-class`](model-customization.md#use-generic-base-class)
 - [`--use-generic-container-types`](typing-customization.md#use-generic-container-types)
 - [`--use-inline-field-description`](field-customization.md#use-inline-field-description)
+- [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel)
 - [`--use-non-positive-negative-number-constrained-types`](typing-customization.md#use-non-positive-negative-number-constrained-types)
 - [`--use-object-type`](typing-customization.md#use-object-type)
 - [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default)

diff --git a/docs/cli-reference/model-customization.md b/docs/cli-reference/model-customization.md
@@ -43,6 +43,7 @@
 | [`--use-default-kwarg`](#use-default-kwarg) | Use default= keyword argument instead of positional argument... |
 | [`--use-frozen-field`](#use-frozen-field) | Generate frozen (immutable) field definitions for readOnly p... |
 | [`--use-generic-base-class`](#use-generic-base-class) | Generate a shared base class with model configuration to avo... |
+| [`--use-missing-sentinel`](#use-missing-sentinel) | Use Pydantic's MISSING sentinel for optional fields without ... |
 | [`--use-one-literal-as-default`](#use-one-literal-as-default) | Use single literal value as default when enum has only one o... |
 | [`--use-root-model-sequence-interface`](#use-root-model-sequence-interface) | Make non-null sequence-like Pydantic v2 RootModel classes im... |
 | [`--use-serialize-as-any`](#use-serialize-as-any) | Wrap fields with subtypes in Pydantic's SerializeAsAny. |
@@ -5246,6 +5247,7 @@ The `--target-pydantic-version` flag controls Pydantic version-specific config:
 
 - **2**: Uses `populate_by_name=True` (compatible with Pydantic 2.0-2.10)
 - **2.11**: Uses `validate_by_name=True` (for Pydantic 2.11+)
+- **2.12**: Uses `validate_by_name=True` and allows features that require Pydantic 2.12+
 
 This prevents breaking changes when generated code is used on older Pydantic versions.
 
@@ -6003,6 +6005,87 @@ Generate a shared base class with model configuration to avoid repetition (DRY).
 
 ---
 
+## `--use-missing-sentinel` {#use-missing-sentinel}
+
+Use Pydantic's MISSING sentinel for optional fields without defaults.
+
+The `--use-missing-sentinel` flag generates `MISSING` as the default for optional
+Pydantic v2 fields that do not define a schema default. This preserves the
+difference between an omitted field and a nullable field set to `None`.
+
+**Related:** [`--strict-nullable`](model-customization.md#strict-nullable), [`--target-pydantic-version`](model-customization.md#target-pydantic-version)
+
+!!! tip "Usage"
+
+    ```bash
+    datamodel-codegen --input schema.json --output-model-type pydantic_v2.BaseModel --use-missing-sentinel # (1)!
+    ```
+
+    1. :material-arrow-left: `--use-missing-sentinel` - the option documented here
+
+??? example "Examples"
+
+    **Input Schema:**
+
+    ```json
+    {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "title": "MissingSentinel",
+      "type": "object",
+      "required": ["required", "requiredNullable"],
+      "properties": {
+        "required": {
+          "type": "integer"
+        },
+        "requiredNullable": {
+          "type": ["integer", "null"]
+        },
+        "unrequired": {
+          "type": "integer"
+        },
+        "nullableUnrequired": {
+          "type": ["integer", "null"]
+        },
+        "withDefault": {
+          "type": "integer",
+          "default": 1
+        },
+        "nullDefault": {
+          "type": ["integer", "null"],
+          "default": null
+        },
+        "aliased-field": {
+          "type": "string"
+        }
+      }
+    }
+    ```
+
+    **Output:**
+
+    ```python
+    # generated by datamodel-codegen:
+    #   filename:  missing_sentinel.json
+    #   timestamp: 2019-07-26T00:00:00+00:00
+
+    from __future__ import annotations
+
+    from pydantic import BaseModel, Field
+    from pydantic.experimental.missing_sentinel import MISSING
+
+
+    class MissingSentinel(BaseModel):
+        required: int
+        requiredNullable: int | None
+        unrequired: int | MISSING = MISSING
+        nullableUnrequired: int | None | MISSING = MISSING
+        withDefault: int | None = 1
+        nullDefault: int | None = None
+        aliased_field: str | MISSING = Field(MISSING, alias='aliased-field')
+    ```
+
+---
+
 ## `--use-one-literal-as-default` {#use-one-literal-as-default}
 
 Use single literal value as default when enum has only one option.

diff --git a/docs/cli-reference/quick-reference.md b/docs/cli-reference/quick-reference.md
@@ -139,6 +139,7 @@ datamodel-codegen [OPTIONS]
 | [`--use-default-kwarg`](model-customization.md#use-default-kwarg) | Use default= keyword argument instead of positional argument for fields with def... |
 | [`--use-frozen-field`](model-customization.md#use-frozen-field) | Generate frozen (immutable) field definitions for readOnly properties. |
 | [`--use-generic-base-class`](model-customization.md#use-generic-base-class) | Generate a shared base class with model configuration to avoid repetition (DRY). |
+| [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel) | Use Pydantic's MISSING sentinel for optional fields without defaults. |
 | [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default) | Use single literal value as default when enum has only one option. |
 | [`--use-root-model-sequence-interface`](model-customization.md#use-root-model-sequence-interface) | Make non-null sequence-like Pydantic v2 RootModel classes implement collections.... |
 | [`--use-serialize-as-any`](model-customization.md#use-serialize-as-any) | Wrap fields with subtypes in Pydantic's SerializeAsAny. |
@@ -383,6 +384,7 @@ All options sorted alphabetically:
 - [`--use-generic-base-class`](model-customization.md#use-generic-base-class) - Generate a shared base class with model configuration to avo...
 - [`--use-generic-container-types`](typing-customization.md#use-generic-container-types) - Use generic container types (Sequence, Mapping) for type hin...
 - [`--use-inline-field-description`](field-customization.md#use-inline-field-description) - Add field descriptions as inline comments.
+- [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel) - Use Pydantic's MISSING sentinel for optional fields without ...
 - [`--use-non-positive-negative-number-constrained-types`](typing-customization.md#use-non-positive-negative-number-constrained-types) - Use NonPositive/NonNegative types for number constraints.
 - [`--use-object-type`](typing-customization.md#use-object-type) - Use object instead of Any for unspecified object and array v...
 - [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default) - Use single literal value as default when enum has only one o...

diff --git a/docs/llms-full.txt b/docs/llms-full.txt
@@ -1118,7 +1118,7 @@ This documentation is auto-generated from test cases.
 | 📁 [Base Options](base-options.md) | 12 | Input/output configuration |
 | 🔧 [Typing Customization](typing-customization.md) | 30 | Type annotation and import behavior |
 | 🏷️ [Field Customization](field-customization.md) | 27 | Field naming and docstring behavior |
-| 🏗️ [Model Customization](model-customization.md) | 43 | Model generation behavior |
+| 🏗️ [Model Customization](model-customization.md) | 44 | Model generation behavior |
 | 🎨 [Template Customization](template-customization.md) | 25 | Output formatting and custom rendering |
 | 📘 [OpenAPI-only Options](openapi-only-options.md) | 8 | OpenAPI-specific features |
 | 📋 [GraphQL-only Options](graphql-only-options.md) | 1 |  |
@@ -1332,6 +1332,7 @@ This documentation is auto-generated from test cases.
 - [`--use-generic-base-class`](model-customization.md#use-generic-base-class)
 - [`--use-generic-container-types`](typing-customization.md#use-generic-container-types)
 - [`--use-inline-field-description`](field-customization.md#use-inline-field-description)
+- [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel)
 - [`--use-non-positive-negative-number-constrained-types`](typing-customization.md#use-non-positive-negative-number-constrained-types)
 - [`--use-object-type`](typing-customization.md#use-object-type)
 - [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default)
@@ -2382,6 +2383,7 @@ Source: https://datamodel-code-generator.koxudaxi.dev/cli-reference/model-custom
 | [`--use-default-kwarg`](#use-default-kwarg) | Use default= keyword argument instead of positional argument... |
 | [`--use-frozen-field`](#use-frozen-field) | Generate frozen (immutable) field definitions for readOnly p... |
 | [`--use-generic-base-class`](#use-generic-base-class) | Generate a shared base class with model configuration to avo... |
+| [`--use-missing-sentinel`](#use-missing-sentinel) | Use Pydantic's MISSING sentinel for optional fields without ... |
 | [`--use-one-literal-as-default`](#use-one-literal-as-default) | Use single literal value as default when enum has only one o... |
 | [`--use-root-model-sequence-interface`](#use-root-model-sequence-interface) | Make non-null sequence-like Pydantic v2 RootModel classes im... |
 | [`--use-serialize-as-any`](#use-serialize-as-any) | Wrap fields with subtypes in Pydantic's SerializeAsAny. |
@@ -7585,6 +7587,7 @@ The `--target-pydantic-version` flag controls Pydantic version-specific config:
 
 - **2**: Uses `populate_by_name=True` (compatible with Pydantic 2.0-2.10)
 - **2.11**: Uses `validate_by_name=True` (for Pydantic 2.11+)
+- **2.12**: Uses `validate_by_name=True` and allows features that require Pydantic 2.12+
 
 This prevents breaking changes when generated code is used on older Pydantic versions.
 
@@ -8342,6 +8345,87 @@ Generate a shared base class with model configuration to avoid repetition (DRY).
 
 ---
 
+## `--use-missing-sentinel` {#use-missing-sentinel}
+
+Use Pydantic's MISSING sentinel for optional fields without defaults.
+
+The `--use-missing-sentinel` flag generates `MISSING` as the default for optional
+Pydantic v2 fields that do not define a schema default. This preserves the
+difference between an omitted field and a nullable field set to `None`.
+
+**Related:** [`--strict-nullable`](model-customization.md#strict-nullable), [`--target-pydantic-version`](model-customization.md#target-pydantic-version)
+
+!!! tip "Usage"
+
+    ```bash
+    datamodel-codegen --input schema.json --output-model-type pydantic_v2.BaseModel --use-missing-sentinel # (1)!
+    ```
+
+    1. :material-arrow-left: `--use-missing-sentinel` - the option documented here
+
+??? example "Examples"
+
+    **Input Schema:**
+
+    ```json
+    {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "title": "MissingSentinel",
+      "type": "object",
+      "required": ["required", "requiredNullable"],
+      "properties": {
+        "required": {
+          "type": "integer"
+        },
+        "requiredNullable": {
+          "type": ["integer", "null"]
+        },
+        "unrequired": {
+          "type": "integer"
+        },
+        "nullableUnrequired": {
+          "type": ["integer", "null"]
+        },
+        "withDefault": {
+          "type": "integer",
+          "default": 1
+        },
+        "nullDefault": {
+          "type": ["integer", "null"],
+          "default": null
+        },
+        "aliased-field": {
+          "type": "string"
+        }
+      }
+    }
+    ```
+
+    **Output:**
+
+    ```python
+    # generated by datamodel-codegen:
+    #   filename:  missing_sentinel.json
+    #   timestamp: 2019-07-26T00:00:00+00:00
+
+    from __future__ import annotations
+
+    from pydantic import BaseModel, Field
+    from pydantic.experimental.missing_sentinel import MISSING
+
+
+    class MissingSentinel(BaseModel):
+        required: int
+        requiredNullable: int | None
+        unrequired: int | MISSING = MISSING
+        nullableUnrequired: int | None | MISSING = MISSING
+        withDefault: int | None = 1
+        nullDefault: int | None = None
+        aliased_field: str | MISSING = Field(MISSING, alias='aliased-field')
+    ```
+
+---
+
 ## `--use-one-literal-as-default` {#use-one-literal-as-default}
 
 Use single literal value as default when enum has only one option.
@@ -27967,6 +28051,7 @@ datamodel-codegen [OPTIONS]
 | [`--use-default-kwarg`](model-customization.md#use-default-kwarg) | Use default= keyword argument instead of positional argument for fields with def... |
 | [`--use-frozen-field`](model-customization.md#use-frozen-field) | Generate frozen (immutable) field definitions for readOnly properties. |
 | [`--use-generic-base-class`](model-customization.md#use-generic-base-class) | Generate a shared base class with model configuration to avoid repetition (DRY). |
+| [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel) | Use Pydantic's MISSING sentinel for optional fields without defaults. |
 | [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default) | Use single literal value as default when enum has only one option. |
 | [`--use-root-model-sequence-interface`](model-customization.md#use-root-model-sequence-interface) | Make non-null sequence-like Pydantic v2 RootModel classes implement collections.... |
 | [`--use-serialize-as-any`](model-customization.md#use-serialize-as-any) | Wrap fields with subtypes in Pydantic's SerializeAsAny. |
@@ -28211,6 +28296,7 @@ All options sorted alphabetically:
 - [`--use-generic-base-class`](model-customization.md#use-generic-base-class) - Generate a shared base class with model configuration to avo...
 - [`--use-generic-container-types`](typing-customization.md#use-generic-container-types) - Use generic container types (Sequence, Mapping) for type hin...
 - [`--use-inline-field-description`](field-customization.md#use-inline-field-description) - Add field descriptions as inline comments.
+- [`--use-missing-sentinel`](model-customization.md#use-missing-sentinel) - Use Pydantic's MISSING sentinel for optional fields without ...
 - [`--use-non-positive-negative-number-constrained-types`](typing-customization.md#use-non-positive-negative-number-constrained-types) - Use NonPositive/NonNegative types for number constraints.
 - [`--use-object-type`](typing-customization.md#use-object-type) - Use object instead of Any for unspecified object and array v...
 - [`--use-one-literal-as-default`](model-customization.md#use-one-literal-as-default) - Use single literal value as default when enum has only one o...
@@ -36680,16 +36766,16 @@ classDiagram
 
 | Config model | Field count | Purpose |
 | --- | ---: | --- |
-| `BaseGenerateConfig` | 138 | Shared generation options. |
-| `GenerateConfig` | 153 | Public `generate()` configuration. |
-| `ParserConfig` | 134 | Base parser dependency injection and parser options. |
-| `JSONSchemaParserConfig` | 136 | JSON Schema parser options. |
-| `OpenAPIParserConfig` | 142 | OpenAPI-specific parser options. |
-| `AsyncAPIParserConfig` | 143 | AsyncAPI-specific parser options. |
-| `XMLSchemaParserConfig` | 137 | XML Schema-specific parser options. |
-| `ProtobufParserConfig` | 137 | Protocol Buffers-specific parser options. |
-| `AvroParserConfig` | 136 | Avro-specific parser options. |
-| `GraphQLParserConfig` | 137 | GraphQL-specific parser options. |
+| `BaseGenerateConfig` | 139 | Shared generation options. |
+| `GenerateConfig` | 154 | Public `generate()` configuration. |
+| `ParserConfig` | 135 | Base parser dependency injection and parser options. |
+| `JSONSchemaParserConfig` | 137 | JSON Schema parser options. |
+| `OpenAPIParserConfig` | 143 | OpenAPI-specific parser options. |
+| `AsyncAPIParserConfig` | 144 | AsyncAPI-specific parser options. |
+| `XMLSchemaParserConfig` | 138 | XML Schema-specific parser options. |
+| `ProtobufParserConfig` | 138 | Protocol Buffers-specific parser options. |
+| `AvroParserConfig` | 137 | Avro-specific parser options. |
+| `GraphQLParserConfig` | 138 | GraphQL-specific parser options. |
 
 ### Formatter Names