Sourced from aws-lambda-powertools's releases.

v3.27.0

Summary

In this release, we focused on the Event Handler utility - we added three new features and shipped several important bug fixes across Event Handler and Idempotency.

• File uploads - handle multipart/form-data uploads with full OpenAPI validation and Swagger UI file picker
• Cookie parameters - use cookies as typed, validated parameters alongside Query(), Header(), and Form()
• Request object - access the resolved route pattern, path parameters, and HTTP method in middleware and route handlers

A huge thanks to @​oyiz-michael, @​siwyd, @​abhu85, and @​danjhd for their contributions!

File upload support for OpenAPI

Docs

You can now handle file uploads in your API endpoints with full OpenAPI validation and Swagger UI support. If using Swagger, it renders a file picker automatically. A special thanks to @​oyiz-michael for starting the initial work on this feature.

from typing import Annotated
from aws_lambda_powertools.event_handler import APIGatewayRestResolver
from aws_lambda_powertools.event_handler.openapi.params import File, Form, UploadFile
app = APIGatewayRestResolver(enable_validation=True)
app.enable_swagger(path="/swagger")
@​app.post("/upload")
def upload(
file_data: Annotated[UploadFile, File(description="CSV file")],
separator: Annotated[str, Form(description="CSV separator")] = ",",
):
return {
"filename": file_data.filename,
"content_type": file_data.content_type,
"file_size": len(file_data),
}

You can receive files as raw bytes (Annotated[bytes, File()]) or as an UploadFile object with filename and content type metadata.

Cookie parameter support for OpenAPI

Docs

You can now use cookies as typed, validated parameters in your API endpoints - just like Query(), Header(), or Form(). The OpenAPI schema generates in: cookie parameters automatically, and validation works across all resolver types.

from typing import Annotated
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Sourced from aws-lambda-powertools's changelog.

[v3.27.0] - 2026-04-06

Maintenance

• version bump

• 31d0872 chore: version bump
• a03795f ci: remove me-south-1 region (#8108)
• bf7e555 docs: adding docs to Request object (#8105)
• a26d64b feat(event_handler): add File parameter support for multipart/form-data uploa...
• 7c9589c feat(event_handler): add Cookie parameter support for OpenAPI utility (#8095)
• ccdc52e fix(data_classes): support {proxy+} and path parameters in authorizer respons...
• 74fbcc5 fix(event_handler): sync middleware receives real response in async ASGI cont...
• 2b95d7f chore(deps-dev): bump isort from 7.0.0 to 8.0.1 (#8101)
• 30e43c1 chore(deps-dev): bump aws-cdk-aws-lambda-python-alpha from 2.243.0a0 to 2.248...
• 779c85c chore(deps-dev): bump types-requests from 2.32.4.20260107 to 2.33.0.20260402 ...
• Additional commits viewable in compare view