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Pydantic Production Incidents & Fixes

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Grouped incident families for Pydantic (use these when you’re debugging during an outage).

Configuration error

issues: 347 fresh: 304 indexable

Data consistency

issues: 39 fresh: 29 indexable

OpenAPI schema

issues: 18 fresh: 16 indexable

Serialization

issues: 18 fresh: 14 indexable

Other

issues: 16 fresh: 14 indexable

Latency

issues: 8 fresh: 7 indexable

Top Queries / Error Strings

These are the lines developers tend to paste into Google during incidents.

complete_model_class(

... (truncated) ...

TypeError: ForwardRef._evaluate() missing 1 required keyword-only argument: 'recursive_guard'

"Unexpected keyword argument" when using `ConfigDict(extra="forbid")`

"family": "fam",

$ python fail.py

$ python main.py

$ python src/test.py

$ uv run --with 'pydantic<2.11' --with rich demo.py

$defs has invalid entry names when using ref_template (json_schema)

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Type errors with @model_validator

#8529 · pydantic/pydantic

Some properties do not remain private after constructing a serialised model

#8523 · pydantic/pydantic

Model computed_fields from a Model Type

#8573 · pydantic/pydantic

FutureDatetime accepts years 1000-1599

#8570 · pydantic/pydantic

Incorrect JSON schema for discriminated unions in nested dataclasses

#8628 · pydantic/pydantic

Ellipsis does not mark annotated field as required in create_model

#8634 · pydantic/pydantic

v2 regression: `__setattr__` hides bugs from type checkers

#8643 · pydantic/pydantic

`NameEmail` does not support parsing from json input

#8649 · pydantic/pydantic

pydantic v2 memory allocation

#8652 · pydantic/pydantic

dataclasses lose annotation if Field used in inherited class

#8670 · pydantic/pydantic

__pydantic_config__ ignored in `TypeAdapter` for `TypedDicts`

#8698 · pydantic/pydantic

Discriminator attribute missing from model schema in a forwardref in pydantic 2.6

#8688 · pydantic/pydantic

Pydantic TzInfo(UTC) != datetime.UTC

#8683 · pydantic/pydantic

false-positive warning wiht pydantic 2.6.0 "Unexpected extra items present in tuple"

#8677 · pydantic/pydantic

Type of `examples` parameter is not checked, which may lead to invalid JSON schema generation

#8732 · pydantic/pydantic

Weird bug that my english is not enough to describe this.

#8777 · pydantic/pydantic

Recursive `dict` causes infinite recursion during schema generation

#8785 · pydantic/pydantic

use_enum_values=True has no effect if another model with the same enum has use_enum_values=False

#8858 · pydantic/pydantic

AssertionError when calling BaseModel.schema_json()

#8896 · pydantic/pydantic

`Literal` annotation does not render type to json-schema

#8905 · pydantic/pydantic

Render Enum Member Docstrings in JSON Schema

#8888 · pydantic/pydantic

validate_call makes an unexpected conversion

#8930 · pydantic/pydantic

Type `IPv4Address` not parsed

#8942 · pydantic/pydantic

The JSON schema for the BaseModel class

#8980 · pydantic/pydantic

"Unexpected keyword argument" when using `ConfigDict(extra="forbid")`

#8954 · pydantic/pydantic

`-Werror`-related test failures with pytest 8.x

#9025 · pydantic/pydantic

GenerateSchema.match_type doesn't support classes inherited from str

#9006 · pydantic/pydantic

mypy doesn't complain about non-existent attributes when setting

#9017 · pydantic/pydantic

Private model attributes handled incorrectly by type checkers

#9048 · pydantic/pydantic

Reconcile behavioral differences between `SerializeAsAny` annotation and `serialize_as_any` runtime flag

#9049 · pydantic/pydantic

Pydantic to JSON Schema translation: Write a field with no default value that is not required in the JSON schema

#9057 · pydantic/pydantic

Unexpected error message while using properties with pydantic models

#9070 · pydantic/pydantic

UserWarning: Field name "XXX" shadows an attribute in parent "XXX"

#9107 · pydantic/pydantic

Union Field: union_mode="smart" with default_factory and self reference ignores data that could be coerced

#9101 · pydantic/pydantic

config keyword in TypeAdapter doesn't update the model

#9142 · pydantic/pydantic

Discriminated union type breaks from 2.6.3 to 2.6.4: TypeError: 'none' is not a valid discriminated union variant;

#9118 · pydantic/pydantic

Cannot use model_copy(deep=True) on a model instance which was created using model_construct, when there is a

#9122 · pydantic/pydantic

Error when parsing a string as an integer

#9165 · pydantic/pydantic

v2.7.0 TypeError in model_construct where field has a validation_alias with AliasChoices

#9216 · pydantic/pydantic

Difference between TypeAdapter().json_schema and BaseModel.model_json_schema

#9210 · pydantic/pydantic

v2.7.0b1 throws error when using OpenAI SDK

#9191 · pydantic/pydantic

Use of __package__ in pydantic/__init__.py fails if imported from zip

#9221 · pydantic/pydantic

JSON serialisation error with Secret types union.

#9231 · pydantic/pydantic

Possible problem with dataclasses.dataclass and calling model_json_schema()

#9253 · pydantic/pydantic

Base64Bytes field doesn't raises validation error for min_length constraint

#9251 · pydantic/pydantic

New Enum validation doesn't work for custom __new__ methods

#9248 · pydantic/pydantic

Memory leak when using Iterable

#9243 · pydantic/pydantic

unhashable type: 'AliasPath' raised from BaseModel.model_construct()

#9239 · pydantic/pydantic

Exclude private attributes (`PrivateAttr`) from dataclass constructor

#9234 · pydantic/pydantic

When using min_length on Sequence field, outputted JSON schema is `minLength` instead of `minItems` for array type

#9256 · pydantic/pydantic

`TypeAdapter` doesn't respect `config['schema_generator']`

#9289 · pydantic/pydantic

v2.7 validation error when integer starts with `+`

#9259 · pydantic/pydantic

Nested Literals together with PEP-695 type statement are failed to produce json schema

#9269 · pydantic/pydantic

ImportString fails to generate JsonSchema - in fastapi openapi docs generation

#9327 · pydantic/pydantic

Enum construction from float worked in v2.6.4 but fails in v2.7.1

#9375 · pydantic/pydantic

misleading error message "Input should be a valid dictionary or instance" when using both pydantic `dataclass` and

#9383 · pydantic/pydantic

Default values not validated

#9389 · pydantic/pydantic

Serializing computed fields returning enums

#9394 · pydantic/pydantic

Schema for `Literal` differs between version 2.6 and 2.7

#9402 · pydantic/pydantic

GenericModel[Any] raises ValidationError for GenericModel[SomeModel]

#9414 · pydantic/pydantic

RootModel.model_construct() typing

#9461 · pydantic/pydantic

Problem when serializing models with `SecretStr`s

#9491 · pydantic/pydantic

`model_json_schema()` fails to include annotated third-party types: "Default value is not JSON serializable

#9525 · pydantic/pydantic

Validation of Enum Field with Decimal Fails

#9559 · pydantic/pydantic

`model_validate_json` cannot validate `Hashable`

#9567 · pydantic/pydantic

Field deprecation with typing_extension.deprecated example in `doc>concepts/fields` does not work

#9575 · pydantic/pydantic

`RootModel` from `dataclass` does not preserve extra fields

#9645 · pydantic/pydantic

TypeError: ForwardRef._evaluate() missing 1 required keyword-only argument: 'recursive_guard'

#9609 · pydantic/pydantic

[docs]: cannot leverage on alias_priority if alias_generator is not involved

#9678 · pydantic/pydantic

Documenting `create_model` with `description`

#9691 · pydantic/pydantic

`validate_call` doesn't use types from local scope

#9744 · pydantic/pydantic

Suggestion: Add DefaultFactory.

#9769 · pydantic/pydantic

validate_default has no effect when attribute type is Literal

#9738 · pydantic/pydantic

2.8.0 unexpectedly change `create_model()`arg `__model_name` to `model_name`

#9810 · pydantic/pydantic

Referencing an external JSON Schema when generating a JSONSchema fails with a KeyError

#9783 · pydantic/pydantic

Union discrimination ignored in Sequence validation

#9872 · pydantic/pydantic

Mypy error: incompatible definition of `model_construct()` in multiple inheritance from `BaseModel` and `RootModel`

#9861 · pydantic/pydantic

`multiple_of` failing on some negative floats

#9871 · pydantic/pydantic

KeyError when trying to instantiate BaseModels that depend on each other

#9887 · pydantic/pydantic

TypeError: '_AnnotatedAlias' object cannot be converted to 'PyType'

#9909 · pydantic/pydantic

pydantic v2 slow import performance

#9905 · pydantic/pydantic

default_factory passed in annotation Field silently ignored

#9947 · pydantic/pydantic

validate_assignment breaks frozen for dataclasses

#10041 · pydantic/pydantic

JSON schema uses allOf when adding Field(description="")

#10031 · pydantic/pydantic

Nested generic inheritance

#10039 · pydantic/pydantic

Using $ref" in examples raises KeyError on .model_json_schema() generation

#9981 · pydantic/pydantic

Support for Snowflake DSN format

#10079 · pydantic/pydantic

Failing core schema generation when importing a model with a mock schema from another module

#10069 · pydantic/pydantic

`PlainSerializer` not respecting `when_used` field during generation of json schema

#10118 · pydantic/pydantic

Support for `annotated_types.Not`

#10111 · pydantic/pydantic

AttributeError when using __future__ import with PrivateAttr in Pydantic

#10153 · pydantic/pydantic

JSON Schema serialization of FloatEnums incorrectly assigns type 'numeric'

#10163 · pydantic/pydantic

defaulting behavior of `Field` inside of `TypeAliasType` not working when used inside discriminated union

#10219 · pydantic/pydantic

__pydantic_complete__ is not updated when rebuilding dataclass

#10284 · pydantic/pydantic

Performance issues related to schema cleaning

#10285 · pydantic/pydantic

`KeyError` happening during schema cleaning with generic models

#10279 · pydantic/pydantic

v2.9.0b1 is breaking napari

#10239 · pydantic/pydantic

Issue using annotated_types.Predicate

#10319 · pydantic/pydantic

Pydantic 2.9 requires annotated-types 0.6.0 or higher

#10323 · pydantic/pydantic

Type alias for model_dump include/exclude is broken

#10333 · pydantic/pydantic

Performance issues related to schema building

#10297 · pydantic/pydantic

Relax default `protected_namespaces` config setting (remove `model_`)

#10315 · pydantic/pydantic

"Failed to get discriminator value for tagged union serialization" when using alias_generator

#10334 · pydantic/pydantic

`include`/`exclude` doesn't work when using `False`

#10335 · pydantic/pydantic

Wrong ordering of serializer and validator in `Annotated` breaks serialized output

#10385 · pydantic/pydantic

Pydantic FilePath does not accept sockets

#10376 · pydantic/pydantic

Schema generation error when serialization schema holds a reference

#10443 · pydantic/pydantic

`PydanticUserError` raised when `model_config` has type annotation and is empty

#10411 · pydantic/pydantic

Field parsing order is not taken into account for Decimal | str

#10413 · pydantic/pydantic

Plain serializer and validator in Annotated does not work with pydantic model

#10434 · pydantic/pydantic

model_json_schema() generates an unexpected leading space in title when using a serialization_alias with a `_` prefix

#10397 · pydantic/pydantic

TypeError when using BeforeValidator

#10459 · pydantic/pydantic

`validate_call` not working with class/custom callables

#10461 · pydantic/pydantic

() false positive mypy error "Only `root` is allowed as a field of a `RootModel`"

#10474 · pydantic/pydantic

Bug: `TypeError: cannot pickle 'staticmethod' object` with a `Field.default`

#10551 · pydantic/pydantic

Internal Pydantic code issuing warnings

#10497 · pydantic/pydantic

`Optional[Decimal]` with field constraints error: Unable to apply constraint 'max_digits' to schema of type

#10498 · pydantic/pydantic

Annotated field schemas broken after v2.9.0

#10528 · pydantic/pydantic

model_dump() does not include Python object for IP addresses

#10589 · pydantic/pydantic

Email parsing slowdown on edgecases

#10600 · pydantic/pydantic

Declaring a generic attribute in a Pydantic model that itself has a generic attribute breaks deserialisation of the

#10695 · pydantic/pydantic

Unexpected Behavior with Extra Arguments in Pydantic Dataclass

#10644 · pydantic/pydantic

() invalid serialization warning when...

#10682 · pydantic/pydantic

mypy incorrectly identifies argument of method within a model_serializer as incorrect

#10707 · pydantic/pydantic

Recent `typing_extensions.TypeAliasType` backport causing tests to fail.

#10711 · pydantic/pydantic

`cached_property` cannot be assigned by recommended way

#10772 · pydantic/pydantic

Change JSON schema (and maybe config) default for `extra` for `dataclass`es and `TypedDict`s

#10785 · pydantic/pydantic

TypeError: ForwardRef._evaluate() missing 1 required keyword-only argument: 'recursive_guard' still occurs with v2.9.2

#10747 · pydantic/pydantic

2.10 breaks type checking for `Field(...)`

#10780 · pydantic/pydantic

Circular ref error with `validate_call`

#10799 · pydantic/pydantic

2.10: dataclass config issues (`arbitrary_types_allowed`, aliases, etc)

#10917 · pydantic/pydantic

pydantic take dataclass `Text` as str if `from __future__ import annotations`

#10889 · pydantic/pydantic

PEP 695 types with reference to `Enum` inside annotation breaks `pydantic_core`

#10877 · pydantic/pydantic

Recursive type aliases should just work

#10873 · pydantic/pydantic

Problem generating OpenAPI schema for models with an enum as the key of a dict

#10960 · pydantic/pydantic

2.10: Blank model title no longer respected by generated JSON schema

#10935 · pydantic/pydantic

In 2.10.1 the AnyHttpUrl is not hashable any more

#10955 · pydantic/pydantic

Missing `eval-type-backport` as required dependency in 2.10.* Pydantic line for Python 3.8/3.9

#10958 · pydantic/pydantic

V2.10.1 custom model_serializer causes problems with dumping model to json

#10965 · pydantic/pydantic

Data class with defer_build set to true causes the error AttributeError: type object '...' has no attribute

#10953 · pydantic/pydantic

In 2.10.x AnyUrl does not validate data uris

#10968 · pydantic/pydantic

Signature of "__replace__" incompatible - RootModel

#10970 · pydantic/pydantic

Model is not fully defined together with from __future__ import annotations (Started in version 2.10.0)

#11004 · pydantic/pydantic

Regression using regex_engine python-re in pydantic >= 2.10b1

#11042 · pydantic/pydantic

"`Foo` is not fully defined; you should define `T`" error when using new generic syntax with dataclass

#11031 · pydantic/pydantic

v2.10.x: OpenAPI schema generation omits constraints for HttpUrl

#11019 · pydantic/pydantic

JSON Schema gen chokes on `BeforeValidator` with a union in the `json_schema_input_type`

#11033 · pydantic/pydantic

pydantic.errors.PydanticUndefinedAnnotation: name 'T' is not defined when using from __future__ import annotations with

#11076 · pydantic/pydantic

`Field()` and `FieldInfo`/metadata ordering inconsistencies and bugs

#11122 · pydantic/pydantic

Support the `closed` attribute of TypedDict and make behavior consistent between BaseModel and TypeAdapter.

#11136 · pydantic/pydantic

AnyUrl: TypeError: object of type 'AnyUrl' has no len()

#11092 · pydantic/pydantic

Validation of parametrized generics issues

#11183 · pydantic/pydantic

Dataclass with `__pydantic_config__` extra=allow and `__pydantic_extra__` field init=False: combination not allowed

#11201 · pydantic/pydantic

Enable mypy plugin to support initializing RootModel fields with values of the generic's type when `init_typed=True`

#11203 · pydantic/pydantic

Result of default_factory is not type-checked against annotation

#11235 · pydantic/pydantic

MRO broken after 2.10.x with subclassed generics

#11220 · pydantic/pydantic

Issues with disabled core schema validation

#11341 · pydantic/pydantic

ConfigDict's json_schema_mode_override does not override default mode for model_json_schema()

#11359 · pydantic/pydantic

Add support for `typing.ReadOnly` on typed dictionaries

#11346 · pydantic/pydantic

RecursionError with recursive types.

#11320 · pydantic/pydantic

Using a dict[ConstrainedStr, _] sets both `patternProperties` and `additionalProperties`

#11404 · pydantic/pydantic

Deprecated fields bugs with forward annotations

#11390 · pydantic/pydantic

`TypeAdapter.dump_python` and `TypeAdapter.dump_json` do not respect `alias_generator` for `Sequence[Item]` fields

#11408 · pydantic/pydantic

Serializer is not applied to json schema default value

#11446 · pydantic/pydantic

Broken validation of fields in `pydantic==2.11.0a{1,2}

#11443 · pydantic/pydantic

Unpacking annotated metadata from PEP 695 type aliases

#11467 · pydantic/pydantic

Schema generation loses Field annotations when using PEP 695 type alias syntax

#11470 · pydantic/pydantic

Annotated `NotRequired` field in `TypedDict` requires `arbitrary_types_allowed=True`

#11510 · pydantic/pydantic

__future__ annotations + TypedDict NotRequired broken in 2.11.0b1

#11557 · pydantic/pydantic

Displaying a parent-child tree of models with a computed `cached_property` causes a RuntimeError

#11574 · pydantic/pydantic

() `Field` info specified through pep 695 type alias statement is not handled correctly

#11552 · pydantic/pydantic

Regression in size of pydantic core schemas and corresponding `model_json_schema()` call time

#11587 · pydantic/pydantic

Support "default" in generated schema when default_factory is used

#11622 · pydantic/pydantic

validate_as(...) doesn't chain correctly

#11624 · pydantic/pydantic

PlainSerializer does not work correctly in 2.11

#11642 · pydantic/pydantic

Remove custom MRO implementation of Pydantic models breaks generic RootModel subclass

#11641 · pydantic/pydantic

`deprecated_instance_property` doesn't work with `pylint`

#11637 · pydantic/pydantic

Model construction fails on non-union types annotated with discriminator.

#11661 · pydantic/pydantic

AttributeError when using `create_model` with `computed_field`.

#11708 · pydantic/pydantic

Fix documentation source code paths for `pydantic_{core,extra_types,settings}`

#11703 · pydantic/pydantic

model_rebuild() doesn't respect use_attribute_docstrings

#11696 · pydantic/pydantic

Recursion ForwardRef issue starting from pydantic 2.11.0

#11689 · pydantic/pydantic

2.11 Regression - Nested annotation references lead to model never being fully buildable

#11682 · pydantic/pydantic

Root models are sometimes inferred as unions by mypy when using the mypy plugin

#11675 · pydantic/pydantic

Types and default value not resolved correctly in inherited class if ONE of types is forward ref

#11663 · pydantic/pydantic

Incorrect `ValidationInfo.field_name` when using `type` statement

#11737 · pydantic/pydantic

Documentation error: Incorrect example in `populate_by_name` docstring

#11765 · pydantic/pydantic

when `use_attribute_docstrings=True`, `DocstringVisitor` fail to grab field docs in unknown reason when using

#11805 · pydantic/pydantic

Inconsistent Private Attribute Type

#11797 · pydantic/pydantic

breaking change in 2.11.4: `create_model` no longer accepts class-based `Config`

#11819 · pydantic/pydantic

Stealth breaking change 2.9 -> 2.10 for type sequences

#11853 · pydantic/pydantic

model_rebuild with _types_namespace does not update forward references in parameterized generic models after v2.10

#11854 · pydantic/pydantic

Add ability to exclude a type from serialization.

#11843 · pydantic/pydantic

Field default gets mutated globally when setting it in a specific model

#11876 · pydantic/pydantic

Tag not extracted from Annotated when using nested named type aliases.

#11930 · pydantic/pydantic

Cannot override certain magic methods in Pydantic dataclass subclasses of native dataclasses

#11934 · pydantic/pydantic

validate_by_alias does not work with validate_call

#11962 · pydantic/pydantic

JSON Schema inconsistently sets Annotated type aliases as required or not

#12024 · pydantic/pydantic

Dataclass field inconsistencies

#12045 · pydantic/pydantic

model_rebuild incorrectly determines rebuild not required

#12061 · pydantic/pydantic