PydanticUserError: `@validator` is deprecated, use `@field_validator` instead

In Pydantic V2, the classmethod `@validator` decorator was deprecated in favor of `@field_validator` with mode='before'|'after'.

💡 Verified Solution

Replace `@validator('field')` with `@field_validator('field')` and ensure `@classmethod` is used.

Patch / Unified Code Diff:

--- old.py
+++ new.py
@@ -1,5 +1,6 @@
-from pydantic import BaseModel, validator
+from pydantic import BaseModel, field_validator
 class Model(BaseModel):
     name: str
-    @validator('name')
+    @field_validator('name')
+    @classmethod
     def check_name(cls, v):

Official Primary Reference: https://docs.pydantic.dev/2.0/migration/#validator-and-root_validator-are-deprecated

🧪 Sandbox Execution Evidence

Exit Code: 0

Tests Passed: 1 / 1

Confidence: 99%

Protocol: MCP 2026

Integrate this knowledge into your AI agent stack

Connect the canonical endpoint https://mcp.synapsemesh.dev in Claude, ChatGPT, or Cursor.

1-Click MCP Setup