FastAPI has shipped a small but meaningful patch release. Version 0.143.5 addresses a bug in request parameter handling, specifically fixing an issue where an empty value was mishandled for a list parameter of byte files. The change arrives as a single focused fix, which is typical of patch-level releases on the project's release track.
The concrete change in this release:
- Fixed handling of an empty value for a byte file list parameter, correcting how FastAPI processes a request that supplies no content for that list.
- The fix was contributed via PR
#9383by@Viicos. - The release is tagged as
0.143.5on the FastAPI repository.
For developers, a byte file list parameter is the kind of signature used when an endpoint accepts multiple uploaded files and reads them as raw bytes. These endpoints are common in APIs that handle uploads, batch ingestion, or file-processing pipelines. When the client sends an empty value for such a parameter, the previous behavior could misfire, since distinguishing "no value provided" from "an empty list" is a subtle edge case in parameter binding and validation. This patch aligns that edge case with expected semantics.
Why it matters: upload endpoints are notoriously tricky around empty and boundary inputs, and a small mishandling can surface as validation errors or unexpected 422 responses in production. A patch release like 0.143.5 is low-risk to adopt, so teams running file-list parameters should bump the version and add a test covering the empty-value case. Because the fix is scoped to one code path, it is a straightforward upgrade for most projects.
Source: https://github.com/fastapi/fastapi/releases/tag/0.143.5