# pydantic_core._pydantic_core.ValidationError: 1 validation error for Order
customer_id
  Field required [type=missing, input_value={}, input_type=dict]

- **ID:** `python/pydantic-missing-field-required`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The model defines customer_id without a default and no value was provided in the input dict; Pydantic v2 raises missing error instead of using None.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 2.x | active | — | — |

## Workarounds

1. **** (98% success)
   ```
   from typing import Optional
class Order(BaseModel):
    customer_id: Optional[int] = None
   ```
2. **** (97% success)
   ```
   from pydantic import Field
class Order(BaseModel):
    items: list = Field(default_factory=list)
   ```

## Dead Ends

- **** — Type checker and Pydantic v2 will complain that None is not int; runtime validation still fails if None is passed explicitly. (70% fail)
- **** — extra controls unknown fields, not missing required fields. (90% fail)