# Black 26.3.1

- Product: Black (https://whatsnew.fyi/product/black)
- Vendor: Python Software Foundation
- Date: 2026-03-12
- Version: 26.3.1
- Original notes: https://github.com/psf/black/releases/tag/26.3.1
- Permalink: https://whatsnew.fyi/product/black/releases/26.3.1

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — Prevent Jupyter notebook magic masking collisions from corrupting cells by using exact-length placeholders for short magics and aborting if a placeholder can no longer be unmasked safely
- **changed** — Always hash cache filename components derived from --python-cell-magics so custom magic names cannot affect cache paths
- **changed** — Disable browser-originated requests by default in Blackd, add configurable origin allowlisting and request body limits, and bound executor submissions to improve backpressure

###### Stable style

- Prevent Jupyter notebook magic masking collisions from corrupting cells by using
  exact-length placeholders for short magics and aborting if a placeholder can no longer
  be unmasked safely (#5038)

###### Configuration

- Always hash cache filename components derived from `--python-cell-magics` so custom
  magic names cannot affect cache paths (#5038)

###### _Blackd_

- Disable browser-originated requests by default, add configurable origin allowlisting
  and request body limits, and bound executor submissions to improve backpressure
  (#5039)