PydanticUserError: `orm_mode` has been renamed to `from_attributes`

In Pydantic V2 the old Config class attribute orm_mode = True was renamed. Using the V1 style Config.orm_mode raises a PydanticUserError. The correct V2 way is model_config = ConfigDict(from_attributes=True).

💡 Verified Solution

Replace class Config: orm_mode = True with model_config = ConfigDict(from_attributes=True). Import ConfigDict from pydantic.

Patch / Unified Code Diff:

--- old.py
+++ new.py
@@ -1,7 +1,6 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, ConfigDict
 class User(BaseModel):
-    class Config:
-        orm_mode = True
+    model_config = ConfigDict(from_attributes=True)
     id: int
     name: str

Official Primary Reference: https://docs.pydantic.dev/2.0/migration/#changes-to-config

🧪 Sandbox Execution Evidence

Exit Code: 0

Tests Passed: 1 / 1

Confidence: 99%

Protocol: MCP 2026

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