diff --git a/scripts/generate_models_simple.py b/scripts/generate_models_simple.py
index 68d9727b..6f6400a9 100755
--- a/scripts/generate_models_simple.py
+++ b/scripts/generate_models_simple.py
@@ -501,6 +501,7 @@ def add_custom_implementations(code: str) -> str:
 # The simple code generator produces type aliases (e.g., PreviewCreativeRequest = Any)
 # for complex schemas that use oneOf. We override them here with proper Pydantic classes
 # to maintain type safety and enable batch API support.
+# Note: All classes inherit from BaseModel (which is aliased to AdCPBaseModel for exclude_none).
 
 
 class FormatId(BaseModel):
@@ -723,7 +724,9 @@ def main():
         "import re",
         "from typing import Any, Literal",
         "",
-        "from pydantic import BaseModel, ConfigDict, Field, field_validator",
+        "from pydantic import ConfigDict, Field, field_validator",
+        "",
+        "from adcp.types.base import AdCPBaseModel as BaseModel",
         "",
         "",
         "",
diff --git a/src/adcp/types/__init__.py b/src/adcp/types/__init__.py
index 7638d9d3..30ff4ac0 100644
--- a/src/adcp/types/__init__.py
+++ b/src/adcp/types/__init__.py
@@ -2,6 +2,7 @@
 
 """Type definitions for AdCP client."""
 
+from adcp.types.base import AdCPBaseModel
 from adcp.types.core import (
     Activity,
     ActivityType,
@@ -14,6 +15,7 @@
 )
 
 __all__ = [
+    "AdCPBaseModel",
     "AgentConfig",
     "Protocol",
     "TaskResult",
diff --git a/src/adcp/types/base.py b/src/adcp/types/base.py
new file mode 100644
index 00000000..ccc28d2f
--- /dev/null
+++ b/src/adcp/types/base.py
@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+"""Base model for AdCP types with spec-compliant serialization."""
+
+from typing import Any
+
+from pydantic import BaseModel
+
+
+class AdCPBaseModel(BaseModel):
+    """Base model for AdCP types with spec-compliant serialization.
+
+    AdCP JSON schemas use additionalProperties: false and do not allow null
+    for optional fields. Therefore, optional fields must be omitted entirely
+    when not present (not sent as null).
+    """
+
+    def model_dump(self, **kwargs: Any) -> dict[str, Any]:
+        if "exclude_none" not in kwargs:
+            kwargs["exclude_none"] = True
+        return super().model_dump(**kwargs)
+
+    def model_dump_json(self, **kwargs: Any) -> str:
+        if "exclude_none" not in kwargs:
+            kwargs["exclude_none"] = True
+        return super().model_dump_json(**kwargs)
diff --git a/src/adcp/types/generated.py b/src/adcp/types/generated.py
index 8f3af924..eb33e454 100644
--- a/src/adcp/types/generated.py
+++ b/src/adcp/types/generated.py
@@ -14,7 +14,9 @@
 import re
 from typing import Any, Literal
 
-from pydantic import BaseModel, ConfigDict, Field, field_validator
+from pydantic import ConfigDict, Field, field_validator
+
+from adcp.types.base import AdCPBaseModel as BaseModel
 
 
 
@@ -945,6 +947,7 @@ class TasksListResponse(BaseModel):
 # The simple code generator produces type aliases (e.g., PreviewCreativeRequest = Any)
 # for complex schemas that use oneOf. We override them here with proper Pydantic classes
 # to maintain type safety and enable batch API support.
+# Note: All classes inherit from BaseModel (which is aliased to AdCPBaseModel for exclude_none).
 
 
 class FormatId(BaseModel):