Change8

FastAPI

Frontend & Mobile

FastAPI framework, high performance, easy to learn, fast to code, ready for production

Latest: 0.134.069 releases10 breaking changes4 common errorsView on GitHub

Release History

0.134.01 feature
Feb 27, 2026

This release introduces support for streaming JSON Lines and binary data using `yield` in responses, necessitating an upgrade to Starlette >=0.46.0.

0.133.11 fix1 feature
Feb 25, 2026

This release introduces the new FastAPI Agent Skill and resolves an issue preventing tests from running correctly on Windows.

0.133.01 feature
Feb 24, 2026

This release introduces support for Starlette 1.0.0+.

0.132.1
Feb 24, 2026

This release focuses on internal maintenance and refactoring, specifically improving the logic for handling OpenAPI and Swagger UI data escaping.

0.132.0Breaking
Feb 23, 2026

This release introduces strict checking for JSON Content-Type headers by default, enhancing request validation. Internal dependencies were also updated.

0.131.0Breaking
Feb 22, 2026

This release primarily focuses on deprecating the `ORJSONResponse` and `UJSONResponse` classes, signaling a shift away from these specific response types.

0.130.01 feature
Feb 22, 2026

This release introduces significant performance improvements for JSON serialization by leveraging Rust-based Pydantic serialization when applicable. New documentation is available for understanding JSON performance.

0.129.2Breaking1 fix
Feb 21, 2026

This release drops support for the `fastapi-slim` package and updates internal tooling, including an upgrade to pytest.

0.129.11 fix1 feature
Feb 21, 2026

This release focuses on documentation improvements, including adding an AI chatbot widget and updating JWT security guidance, alongside a fix for JSON Schema generation for byte fields.

0.129.0Breaking
Feb 12, 2026

This release drops support for Python 3.9 and updates internal types and documentation examples to align with Python 3.10.

0.128.81 fix
Feb 11, 2026

This release primarily contains documentation fixes and internal build updates, including the deprecation of the `fastapi-slim` package.

0.128.72 features
Feb 10, 2026

This release introduces clearer error handling for self-referencing routers and updates the type hint for HTTPException headers from dict to Mapping.

0.128.61 fix
Feb 9, 2026

This release primarily focuses on bug fixes, specifically addressing issues with `on_startup` and `on_shutdown` parameters in `APIRouter`, alongside minor internal improvements and translation updates.

0.128.5
Feb 8, 2026

This release focuses on internal refactoring and simplification of Pydantic v1 and v2 compatibility utilities, along with adding inline snapshot tests for OpenAPI generation.

0.128.4
Feb 7, 2026

This release primarily contains internal refactoring to simplify Pydantic v1/v2 utility code and remove legacy Pydantic v1 specific logic, alongside translation updates.

0.128.3
Feb 6, 2026

This release refactors the internal implementation of `on_event` for future Starlette compatibility while maintaining existing behavior. It also updates the supported version range for Starlette and tightens minimum dependency requirements for optional extras.

0.128.21 fix2 features
Feb 5, 2026

This release introduces support for PEP695 `TypeAliasType` and allows using `Response` as a dependency annotation. It also includes a fix for issues related to `Json[list[str]]` usage.

0.128.14 fixes2 features
Feb 4, 2026

This release introduces improvements for mobile Swagger UI and clearer error messages for invalid query parameters. It also includes several bug fixes related to validation errors, OpenAPI generation, and header parsing.

0.128.0Breaking
Dec 27, 2025

This release officially drops support for Pydantic v1, requiring all users to migrate to Pydantic v2. Internal performance tests have also been updated to reflect this change.

0.127.11 feature
Dec 26, 2025

This release introduces a custom deprecation warning class and adds a documentary to the documentation website, alongside internal CI improvements and translation updates.

0.127.0Breaking2 features
Dec 21, 2025

This release introduces deprecation warnings for pydantic.v1 and adds new LLM prompt files for Korean and Japanese translations.

0.126.0Breaking1 fix2 features
Dec 20, 2025

This release drops support for Pydantic v1, establishing Pydantic v2.7.0 as the new minimum requirement while adding performance testing via CodSpeed.

0.125.0Breaking2 fixes3 features
Dec 17, 2025

This release drops support for Python 3.8 and upgrades the internal codebase to Python 3.9+ syntax. It also includes significant updates to documentation translations and the CI pipeline for LLM-assisted localization.

0.124.41 fix
Dec 12, 2025

This release includes a bug fix for parameter aliases.

0.124.31 fix
Dec 12, 2025

This release fixes a bug regarding tagged unions in request bodies and updates documentation security practices for re-raising validation errors.

0.124.21 fix
Dec 10, 2025

This release fixes an issue with type hint evaluation, specifically improving support for 'if TYPE_CHECKING' blocks and stringified annotations.

0.124.11 fix
Dec 10, 2025

This release fixes a bug related to arbitrary type handling and updates documentation for the Advanced User Guide and project generation.

0.124.01 feature
Dec 6, 2025

This release improves developer experience by adding endpoint metadata to tracebacks and includes internal script maintenance.

0.123.102 fixes
Dec 5, 2025

This release provides bug fixes for dependency injection using classes with __call__ methods and resolves schema generation issues involving computed_field.

0.123.91 fix
Dec 4, 2025

This release fixes an issue with OAuth2 scope generation in OpenAPI documentation when dealing with nested dependencies and specific security scheme configurations.

0.123.82 fixes
Dec 4, 2025

This release fixes a bug in OpenAPI generation where OAuth2 security schemes were not correctly deduplicated when using different scopes.

0.123.71 fix
Dec 4, 2025

This release provides a bug fix for evaluating stringified type annotations specifically for users on Python 3.10.

0.123.61 fix
Dec 4, 2025

This release fixes a bug involving the combined use of functools.wraps and functools.partial in FastAPI path operations and dependencies.

0.123.51 fix3 features
Dec 2, 2025

This release improves dependency injection support for wrapped functions and functools.partial, while fixing a bug related to Python 3.10 union syntax in sequences.

0.123.41 fix
Dec 2, 2025

This release fixes an issue with OpenAPI schema generation for computed fields and updates the docstring for the servers parameter.

0.123.32 fixes
Dec 2, 2025

This release focuses on bug fixes for parameter model aliases and sequence serialization issues when using Pydantic V2.

0.123.24 fixes
Dec 2, 2025

This release focuses on bug fixes for parameter parsing and error formatting, alongside documentation improvements for virtual environments and SQL tutorials.

0.123.13 fixes
Dec 2, 2025

This release focuses on bug fixes for Pydantic v2 compatibility remapping and decimal encoding for NaN/Infinity values, alongside internal CI improvements for Windows.

0.123.01 fix
Nov 30, 2025

This release includes a bug fix to improve dependency caching for dependencies that do not utilize scopes or have sub-dependencies with scopes.

0.122.11 fix
Nov 30, 2025

This release fixes a bug in hierarchical security scope propagation and includes minor internal dependency updates and documentation CSS improvements.

0.122.0Breaking1 fix
Nov 24, 2025

This release updates security classes to return a more accurate 401 Unauthorized status code instead of 403 Forbidden when credentials are missing, and includes several internal CI/documentation improvements.

0.121.31 fix1 feature
Nov 19, 2025

This release improves internal tool compatibility by making dependency injection results hashable and updates the Starlette dependency constraint.

0.121.21 fix
Nov 13, 2025

This release focuses on a bug fix for JSON Schema '$ref' attributes and includes several documentation updates and translation synchronizations for Portuguese, Russian, and German.

0.121.11 fix
Nov 8, 2025

This release fixes a bug with top-level parameterless dependencies using function scope and updates documentation for advanced dependencies with yield.

0.121.01 feature
Nov 3, 2025

This release introduces scoped dependencies, allowing yield-based dependencies to exit before the response is sent by using scope="request".

0.120.41 fix
Oct 31, 2025

This release fixes a bug where security schemes added at the top-level FastAPI application were not correctly reflected in the generated OpenAPI schema.

0.120.3
Oct 30, 2025

This release focuses on internal refactoring of the dependency injection system to reduce recursion and simplify code using dataclasses. It also includes minor documentation updates for untranslated pages.

0.120.21 fix
Oct 29, 2025

This release provides a bug fix for OpenAPI schema generation involving nested models, resolving an issue introduced in the previous version.

0.120.1
Oct 27, 2025

This release updates the Starlette dependency constraint to <0.50.0 and performs internal maintenance on the pyproject.toml license metadata.

0.120.01 feature
Oct 23, 2025

FastAPI 0.120.0 migrates its internal reference documentation utility from typing_extensions.Doc to the new annotated-doc package and includes German documentation updates.

0.119.11 fix
Oct 20, 2025

This release focuses on internal compatibility fixes for Pydantic v1 when running on Python 3.14 and updates documentation links for Starlette and Uvicorn.

0.119.02 features
Oct 11, 2025

This release introduces temporary dual-support for Pydantic v1 and v2 models to facilitate migration, while officially deprecating Pydantic v1 support.

0.118.31 feature
Oct 10, 2025

This release introduces support for Python 3.14.

0.118.21 fix
Oct 8, 2025

This release provides a bug fix for tagged discriminated unions in request bodies and updates internal CI dependencies.

0.118.11 fix2 features
Oct 8, 2025

This release focuses on ensuring compatibility with Pydantic 2.12.0, expanding Russian translations, and updating internal dependencies and documentation.

0.118.0Breaking2 fixes
Sep 29, 2025

FastAPI 0.118.0 fixes a critical issue where dependencies with 'yield' (like database sessions) were closed before StreamingResponse could finish, and updates security tutorials to use pwdlib.

0.117.11 fix
Sep 20, 2025

This release includes a bug fix for parameter validation when using both File and Form parameters in a specific declaration order.

0.117.05 fixes3 features
Sep 20, 2025

This release introduces support for bodiless responses and array-based OpenAPI types, while providing several bug fixes for Pydantic V1 integration and dependency resolution.

0.116.23 fixes3 features
Sep 16, 2025

This release upgrades the supported Starlette version range and focuses heavily on documentation improvements, including proxy header configurations and Pydantic method deprecations.

0.116.1
Jul 11, 2025

This release primarily updates the supported Starlette version range and includes minor documentation and internal maintenance updates.

0.116.05 features
Jul 7, 2025

This release introduces integrated support for FastAPI Cloud deployment via the 'fastapi deploy' command and updates the 'standard' installation extra to include 'fastapi-cloud-cli'.

0.115.141 fix
Jun 26, 2025

This release fixes a bug regarding Union type support in Form parameters and includes several documentation updates and translations.

0.115.131 fix3 features
Jun 17, 2025

This release updates ReDoc to 2.x, adds refreshUrl support to OAuth2PasswordBearer, and fixes a Pydantic V2 description truncation bug. It also improves the documentation UI for password fields in OAuth2 forms.

0.115.121 fix
Mar 23, 2025

This release focuses on a bug fix for Pydantic header models with underscores and includes extensive documentation updates and translations across multiple languages.

0.115.111 fix1 feature
Mar 1, 2025

This release restores and officially supports custom validations using Pydantic's Annotated and AfterValidator, including new documentation and tests. It also includes internal updates to GitHub topics and contributor lists.

0.115.101 fix3 features
Feb 28, 2025

This release focuses on internal compatibility updates for Pydantic 2.11, expands Starlette dependency ranges, and adds extensive documentation translations for Ukrainian, Japanese, and Vietnamese.

0.115.93 fixes2 features
Feb 27, 2025

This release focuses on a fix for HTTPDigest error handling, significant documentation improvements, and a large number of international translations. It also includes internal test refactors and dependency updates.

0.115.81 fix1 feature
Jan 30, 2025

This release adds support for Python 3.13, fixes a RegEx validation issue in OAuth2 password forms, and includes various internal refactors and documentation translations.

0.115.74 fixes3 features
Jan 22, 2025

This release focuses on dependency upgrades for security and compatibility, alongside a significant overhaul of documentation translations and test suite simplifications.

Common Errors

PydanticUserError2 reports

PydanticUserError in FastAPI often arises from incorrect type hinting involving Pydantic models, especially within dependencies or request body definitions. Resolve this by ensuring consistent and explicit type annotations: use `Annotated` correctly for dependencies with `Body()` and verify discriminated unions are properly defined and imported from `typing` instead of `collections`. Consider explicitly defining a Pydantic model schema when using complex types within request bodies.

ValidationError1 report

The "ValidationError: field required (type=value_error.missing)" error usually means your FastAPI endpoint expects a specific field in the request body, but it's missing or wasn't properly sent in the request. To fix this, ensure your request body includes all the required fields as defined in your Pydantic model associated with the endpoint, and verify that the field names match exactly. Also, check that the Content-Type header in your request is set to "application/json" if you are sending a JSON payload.

NotImplementedError1 report

NotImplementedError in FastAPI often arises when a custom type lacks explicit handling for JSON serialization or schema generation, especially when `arbitrary_types_allowed=True`. To fix this, implement `__get_validators__` and `json_encoders` within your custom type to define how it is serialized and represented in the OpenAPI schema, or use a suitable pydantic field type for serialization. Ensure that pydantic can properly understand and serialize the custom type when generating the OpenAPI schema.

RequestValidationError1 report

The "RequestValidationError" usually means your FastAPI endpoint expects data in the request body that is missing or doesn't match the expected schema. To fix this, carefully examine your pydantic model and ensure the incoming request includes all required fields with the correct data types. You can also use `Optional[]` for non-required fields in your Pydantic model.

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