Highlights

This release fixes a security issue in Black's bundled GitHub Action. Repositories that
use the action are encouraged to update to the latest version of Black immediately. This
update is received automatically when using psf/black@stable, and is independent of
the version of Black installed by the action.

When the GitHub Action reads version specifiers from tool.black.required-version, it
now only accepts released versions of Black, as it already did for black requirements
in dependency lists. Other values, such as URL references, are now rejected. This issue
has been registered as GHSA-cg8m-r9f2-5wm2; a CVE identifier is pending.

Stable style

• Fix a long Jupyter notebook assignment magic (for example x = !ls -la) being wrapped
  in parentheses, which IPython can no longer run; such cells are now left unchanged
  (#5481)
• Keep repeated lines outside the selected --line-ranges unchanged (#5436)
• Fix --line-ranges formatting lines that follow a statement when formatting joins or
  re-indents that statement (#5484)
• Fix --line-ranges crashing with an internal error when an unselected statement has a
  # fmt: skip comment on the last line before a closing bracket (#5477)
• Prevent moving an encoding declaration (for example # -*- coding: latin-1 -*-) onto
  the first two lines of a file (#5487)
• Fix adding an extra trailing blank line inside a multi-line module docstring when its
  last line is near the line length limit (#5494)

Preview style

• Do not split short expressions on delimiters (such as binary operators, comparisons,
  or comprehensions) inside brackets when preceded by a standalone comment (#5455)
• Fix the unstable string_processing feature removing backslash-newline sequences from
  raw strings, which changed their value (#5482)
• Avoid adding unnecessary parentheses around unbreakable right-hand side expressions in
  assignments (such as annotated assignments or subscript targets) (#5473)
• Parenthesize expressions with parameter comments when they exceed the line length
  under --preview (#5442)
• Fix wrap_long_dict_values_in_parens dropping the parentheses around a right-hand
  side that contains a dictionary, leaving a line over the length limit (#5492)
• Fix the unstable string_processing feature adding a space after * or ** in a PEP
  695 type parameter (* Ts = ...) when it splits a string in the parameter's default
  (#5504)
• Avoid unnecessary line splits of trailers (such as indexing/subscripts) when an
  earlier bracket split exceeds the line length only due to a trailing comment (#5498)

Configuration

• Add --cache-dir to configure the cache directory from the command line (#5433)
• Don't cache a file as formatted after formatting or checking it with --line-ranges,
  which made a later full black --check pass and black skip the unformatted lines
  (#5476)
• Respect a .gitignore that starts with a UTF-8 byte order mark. The mark became part
  of the first pattern, so that pattern never matched and Black formatted files that git
  ignores (#5497)

Performance

• Avoid quadratic runtime when splitting very long lines with many trailing bracket
  pairs (such as consecutive subscripts) (#5475)

Integrations

• Fix the GitHub Action crashing on dependency-group includes when use_pyproject is
  enabled (#5479)
• When the GitHub Action reads version specifiers from tool.black.required-version, it
  now only accepts released versions of Black, as it already did for black
  requirements in dependency lists. Other values, such as URL references, are now
  rejected. (#5510)

Stable style

• --line-ranges no longer inserts an empty line after a docstring when the range
  covers only the docstring itself (#5312)
• Fix # fmt: skip on a bracketed ternary turning the surrounding tuple into a call
  (#5464)
• Fix crash when # fmt: skip is placed on a one-line function or class with PEP 695
  type parameters (#5429)
• Fix an inline comment after the closing bracket of optional parentheses being moved
  inside the parentheses when the parenthesized expression contains own-line comments
  (#5395)
• Fix unparseable output when # fmt: skip is placed on a bracket of an if, while,
  for, or with header (#5401, #5405)
• Fix crash when formatting parenthesized expressions with multiple inline comments and
  # fmt: skip (#5414)
• Fix parsing Jupyter notebook assignment magics when non-ASCII characters appear
  earlier on the line (#5381)
• Preserve blank lines that come immediately before a # fmt: on comment (#5300)
• Keep the parentheses around the target of an annotated assignment (e.g.
  (x): int = 5), which prevent CPython from including the name in __annotations__
  (#5321)
• Stop treating a t-string in docstring position as a docstring (e.g. t" spam " as
  the first statement of a module, class or function) (#5287)
• Fix unparseable output for a t-string whose replacement field contains a quote (e.g.
  t'\'{a["b"]}\'') (#5265)
• Fix unparseable output for a triple-quoted string whose body ends in an
  already-escaped double quote (e.g. '''\'''\"''') (#5262)
• Fix --skip-magic-trailing-comma dropping the trailing comma from a split
  single-element tuple used as a lambda parameter default (#5246)
• Fix unstable formatting when an inline comment sits on optional parentheses (e.g. a
  parenthesized assert message) (#5241)
• Fix --skip-magic-trailing-comma dropping the trailing comma of a one-element
  subscript (a[x,]) when the line is long enough to be split and contains a power
  operator (#5272)
• Fix crash when a standalone comment sits between tokens of a comprehension or lambda
  (#5144)
• Fix inline comments on a bracket inside a comprehension being dropped (#5330)
• Respect the magic trailing comma in a PEP 695 type parameter list containing a
  *TypeVarTuple or **ParamSpec (#5244)
• Fix crash when a comment-only # fmt: off/# fmt: on block is followed by a with
  statement after another standalone comment (#5189)
• Fix a crash when splitting case case if ... match patterns at very small line
  lengths (#5147)
• Fix multiline docstring indentation when leading tabs are used inside indented
  docstrings (#5148)
• Respect # fmt: skip on a line that opens a bracket (e.g.
  from x import ( # fmt: skip) when a standalone comment is among the bracket's
  contents (#5161)
• Fix an AST safety error when separate # type: ignore comments in a parenthesized
  attribute chain were merged onto one physical line (#5297)
• Preserve comments and blank lines outside requested ranges when formatting with
  --line-ranges (#5175)
• Fix crash when # fmt: skip is used on one-line async def, async with, and
  async for statements containing a semicolon (#5311)
• Stop converting form feeds or other similar characters in docstrings into newlines
  (#5461)
• Fix --skip-source-first-line turning the skipped line's CRLF ending into \r\r\n
  when reformatting a file with CRLF line endings (#5438)

Preview style

New preview features

• Add missing blank lines after classes whose last method has an ellipsis body (#5439)
• Split only the brackets holding a magic trailing comma when more trailers follow them
  (e.g. stop splitting inside the [2] of [1,][2](3)) (#5448)
• Keep dictionary keys containing operators together on one line when the value can be
  wrapped onto a new line instead (#5435)
• Remove redundant parentheses around individual variables in unpacking targets (e.g.
  for (x), (y) in points: becomes for x, y in points:) (#5416)
• Normalize uppercase T prefixes on t-strings to lowercase (#5425)
• Remove redundant parentheses around generator expressions (#5304, #5369)
• Preserve two blank lines before a top-level class starting inside a # fmt: off block
  after an import (#5238)
• Fix unnecessary parentheses around short right-hand expressions in indexed assignments
  (e.g. x[key] = expr) (#5095)
• Parenthesize tuple expressions in yield statements for consistency with function
  calls and returns (#5170)
• Stop splitting between a variable and its operator (not in, ==, is, ...) when
  the right-hand side is a bracketed expression, and instead split inside the brackets
  (#5135)
• In .pyi stub files, enforce a blank line after a function or method that has a
  docstring-only body when another comment or statement follows it (#5158)

Updates to existing preview features

• Fix crash in stub files when # fmt: skip is placed on a function in a group of
  same-name decorated functions (e.g. @overloads or a property setter) (#5430)
• Keep the parentheses around a lambda used as the iterable of a comprehension (e.g.
  [x for x in (lambda: 0) if x]) (#5176, #5200)

Updates to existing unstable features

• Do not treat multi-line expressions with merged strings and trailing # type: ignore
  comments as single-line unsplittable expressions (#5466)
• Fix duplicated inline comment when stripping the parentheses around a string or
  merging a backslash-continued string on the same line (#5449)
• Split long stringified return annotations even when the function has parameters
  (#5427)
• Don't hug brackets when doing so would join two # type: ignore comments onto one
  line (#5271)
• Fix a crash when # type: ignore is lost during formatting of a long parenthesized
  string (#5329)
• Fix only the first part of an implicitly concatenated unmergeable string (e.g.
  r"..." r"...") being wrapped in parentheses (#5434)

Configuration

• Add support for NO_COLOR environment variable to disable ANSI output (#5129)
• Remove spurious target version warning when runtime version is included in a
  --target-version flag (#5167)
• Fix --force-exclude not excluding files whose path contains .. (e.g.
  black ../generated/file.py run from a subdirectory) (#5471)
• Fall back to the default configuration, with a warning, when the given sources share
  no common project root (e.g. they are on different drives on Windows) instead of
  crashing (#5386)
• Fix loading a stale cached pyproject.toml path when --code is used from different
  working directories in the same process (#5152)
• Add validation for --line-ranges values (#5107)
• Ignore empty cache files instead of raising an EOFError (#5192)
• Reject non-string include and force-exclude values in pyproject.toml (#5193)
• Validate BLACK_NUM_WORKERS values and report invalid values as usage errors instead
  of crashing (#5211)
• Ignore permission errors when reading cache (#5258)

Packaging

• Reduce the size of Linux standalone binaries by stripping debug symbols during the
  PyInstaller release build (#5223)
• Black is now released using GitHub
  Immutable Releases
  (#5296)

Performance

• Fix superlinear runtime growth with the number of input files (#5450)
• Improve performance on strings containing many consecutive backslashes (#5163)
• Improve performance on files with many # fmt: skip/# fmt: off/# fmt: on comments
  (#5169, #5190, #5232)
• Improve performance on long calls and collections (#5177)
• Improve performance on multiline strings inside large collections (e.g. a dict literal
  with triple-quoted strings as values) (#5188)
• Improve performance on files with many soft keywords (e.g. match/case blocks)
  (#5186)
• Improve performance on long semicolon-separated statements (in the stable style) and
  large dict literals (in --preview) (#5184)
• Improve performance of --line-ranges on files with many sibling blocks (a long
  if/elif chain, a match with many cases, or many top-level definitions) (#5213)
• Improve performance on deeply nested bracketed expressions (#5171, #5242)
• Improve performance on lists and subscripts holding one long expression without
  operators (e.g. a long run of implicitly concatenated strings inside []) (#5239)
• Improve performance on deeply chained operations (e.g. a long a ** b ** c ** ...
  chain) (#5235)
• Improve performance on long if/elif chains and other compound statements with many
  clauses (#5322)
• Improve performance of string_processing:
  • when merging implicitly concatenated f-strings containing long string literals
    (#5165)
  • when merging long implicitly concatenated strings (#5173, #5194)
  • when rewriting large nodes (e.g. "%s ..." % (a, b, c, ...)) (#5178, #5199, #5220)
  • when splitting long string literals (#5183)

Output

• Report parser failures using editor-friendly path:line:column locations (#5237)
• Fix crash when writing formatted code or diffs to a sys.stdout that has no buffer
  attribute (e.g. in Jupyter notebooks) (#5411)
• Report parse failures on Black's own output as internal errors (#5383)

Blackd

• Return HTTP 400 instead of 500 when the X-Python-Variant header is empty or has an
  empty entry (e.g. a trailing comma) (#5428)
• Allow optional whitespace around comma-separated versions and pyi in the
  X-Python-Variant header (#5441)

Integrations

• Remove unused migrate-black script (#5319)
• Support PEP 440 version specifiers in tool.black.required-version for the GitHub
  Action (#5399)
• Add outputs (is_formatted, change_count, same_count, failure_count) to GitHub
  Action runs (#5408)

Documentation

• Document vim-python-pep8-indent, which provides an indentexpr for Black-style
  insert-mode indentation (#5288)

Stable style

• Fix unstable formatting of annotated assignments whose subscript annotation contains
  an inline comment (e.g. x: list[ # pyright: ignore[...]) (#5130)
• Preserve inline comments (including # type: ignore) immediately before a
  # fmt: skip line, avoiding AST equivalence failures (#5139)

Packaging

• Correct the version in the published executables (#5137)

Documentation

• Add Neovim integration guide covering conform.nvim, ALE, and simple command approaches
  (#5124)

Highlights

• Add support for unpacking in comprehensions (PEP 798) and for lazy imports (PEP 810),
  both new syntactic features in Python 3.15 (#5048)
• Python 3.15 is now supported. Compiled wheels are not yet provided for Python 3.15, so
  performance may be slower than on existing Python versions. Wheels will be provided
  once Python 3.15 is later in its release cycle. (#5127)

Stable style

• Fix # fmt: skip being ignored in nested if expressions with parenthesized in
  clauses (#4903)
• Add syntactic support for Python 3.15 (#5048)
• Fix crash when an f-string follows a # fmt: off comment inside brackets (#5097)
• Preserve multiline compound statement headers when # fmt: skip is placed on the
  colon line (#5117)

Preview style

• Improve heuristics around whether blank lines should appear before, within and after
  groups of same-name decorated functions (such as @overload groups) in .pyi stub
  files (#5021)
• Fix blank lines being removed between a function and a decorated class in .pyi stub
  files (#5092)
• Prevent string merger from creating unsplittable long lines when a pragma comment
  (e.g. # type: ignore) follows the closing bracket (#5096)

Packaging

• Run CI on 3.15 (#5127)

Output

• Improve parse error readability by showing multi-line output with an error pointer.
  (#5068)
• Add SourceASTParseError to distinguish source parse failures from internal safety
  errors, improving error reporting when Black's lenient parser accepts input that
  ast.parse() rejects (#5080)

Blackd

• Return HTTP 400 (Bad Request) for source parse failures instead of HTTP 500, keeping
  HTTP 500 only for genuine internal safety errors (#5080)

Integrations

• Added documentation for doctest formatting tools and updated the integrations index to
  match (#4916)

Documentation

• Use "Version X.Y.Z" headings in changelog for stable permalink anchors on ReadTheDocs
  (#5063)
• Note in the editor integrations that the SublimeText sublack plugin is archived and
  unmaintained (#5082)

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)

Stable style

• Don't double-decode input, causing non-UTF-8 files to be corrupted (#4964)
• Fix crash on standalone comment in lambda default arguments (#4993)
• Preserve parentheses when # type: ignore comments would be merged with other
  comments on the same line, preventing AST equivalence failures (#4888)

Preview style

• Fix bug where if guards in case blocks were incorrectly split when the pattern had
  a trailing comma (#4884)
• Fix string_processing crashing on unassigned long string literals with trailing
  commas (one-item tuples) (#4929)
• Simplify implementation of the power operator "hugging" logic (#4918)

Packaging

• Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in
  frozen environments (#4930)

Performance

• Introduce winloop for windows as an alternative to uvloop (#4996)
• Remove deprecated function uvloop.install() in favor of uvloop.new_event_loop()
  (#4996)
• Rename maybe_install_uvloop function to maybe_use_uvloop to simplify loop
  installation and creation of either a uvloop/winloop evenloop or default eventloop
  (#4996)

Output

• Emit a clear warning when the target Python version is newer than the running Python
  version, since AST safety checks cannot parse newer syntax. Also replace the
  misleading "INTERNAL ERROR" message with an actionable error explaining the version
  mismatch (#4983)

Blackd

• Introduce winloop to be used when windows in use which enables blackd to run faster on
  windows when winloop is installed. (#4996)

Integrations

• Remove unused gallery script (#5030)
• Harden parsing of black requirements in the GitHub Action when use_pyproject is
  enabled so that only version specifiers are accepted and direct references such as
  black @ https://... are rejected. Users should upgrade to the latest version of the
  action as soon as possible. This update is received automatically when using
  psf/black@stable, and is independent of the version of Black installed by the
  action. (#5031)

Documentation

• Expand preview style documentation with detailed examples for wrap_comprehension_in,
  simplify_power_operator_hugging, and wrap_long_dict_values_in_parens features
  (#4987)
• Add detailed documentation for formatting Jupyter Notebooks (#5009)

Highlights

Introduces the 2026 stable style (#4892), stabilizing the following changes:

• always_one_newline_after_import: Always force one blank line after import
  statements, except when the line after the import is a comment or an import statement
  (#4489)
• fix_fmt_skip_in_one_liners: Fix # fmt: skip behavior on one-liner declarations,
  such as def foo(): return "mock" # fmt: skip, where previously the declaration would
  have been incorrectly collapsed (#4800)
• fix_module_docstring_detection: Fix module docstrings being treated as normal
  strings if preceded by comments (#4764)
• fix_type_expansion_split: Fix type expansions split in generic functions (#4777)
• multiline_string_handling: Make expressions involving multiline strings more compact
  (#1879)
• normalize_cr_newlines: Add \r style newlines to the potential newlines to
  normalize file newlines both from and to (#4710)
• remove_parens_around_except_types: Remove parentheses around multiple exception
  types in except and except* without as (#4720)
• remove_parens_from_assignment_lhs: Remove unnecessary parentheses from the left-hand
  side of assignments while preserving magic trailing commas and intentional multiline
  formatting (#4865)
• standardize_type_comments: Format type comments which have zero or more spaces
  between # and type: or between type: and value to # type: (value) (#4645)

The following change was not in any previous stable release:

• Regenerated the _width_table.py and added tests for the Khmer language (#4253)

This release alo bumps pathspec to v1 and fixes inconsistencies with Git's
.gitignore logic (#4958). Now, files will be ignored if a pattern matches them, even
if the parent directory is directly unignored. For example, Black would previously
format exclude/not_this/foo.py with this .gitignore:

exclude/
!exclude/not_this/

Now, exclude/not_this/foo.py will remain ignored. To ensure exclude/not_this/ and
all of it's children are included in formatting (and in Git), use this .gitignore:

*/exclude/*
!*/exclude/not_this/

This new behavior matches Git. The leading */ are only necessary if you wish to ignore
matching subdirectories (like the previous behavior did), and not just matching root
directories.

Output

• Explicitly shutdown the multiprocessing manager when run in diff mode too (#4952)

Integrations

• Upgraded PyPI upload workflow to use Trusted Publishing (#4611)

This is a preview of the Black stable style for 2026 (#4892). Please test it and
share your feedback!

The following formatting changes are included:

• always_one_newline_after_import: Always force one blank line after import
  statements, except when the line after the import is a comment or an import statement
  (#4489)
• fix_fmt_skip_in_one_liners: Fix # fmt: skip behavior on one-liner declarations,
  such as def foo(): return "mock" # fmt: skip, where previously the declaration would
  have been incorrectly collapsed (#4800)
• fix_module_docstring_detection: Fix module docstrings being treated as normal
  strings if preceded by comments (#4764)
• fix_type_expansion_split: Fix type expansions split in generic functions (#4777)
• multiline_string_handling: Make expressions involving multiline strings more compact
  (#1879)
• normalize_cr_newlines: Add \r style newlines to the potential newlines to
  normalize file newlines both from and to (#4710)
• remove_parens_around_except_types: Remove parentheses around multiple exception
  types in except and except* without as. See PEP 758 for details (#4720)
• remove_parens_from_assignment_lhs: Remove unnecessary parentheses from the left-hand
  side of assignments while preserving magic trailing commas and intentional multiline
  formatting (#4865)
• standardize_type_comments: Format type comments which have zero or more spaces
  between # and type: or between type: and value to # type: (value) (#4645)
• Regenerated the _width_table.py and added tests for the Khmer language (#4253)

Please test out the draft 2026 style in version 26.1a1! This style will be finalized in
the January release (26.1.0). Most of the changes in --preview will be in the 2026
stable style, but not all.
Please share your feedback!

This release (25.12.0) will still produce the 2025 style.

Highlights

• Black no longer supports running with Python 3.9 (#4842)

Stable style

• Fix bug where comments preceding # fmt: off/# fmt: on blocks were incorrectly
  removed, particularly affecting Jupytext's # %% [markdown] comments (#4845)
• Fix crash when multiple # fmt: skip comments are used in a multi-part if-clause, on
  string literals, or on dictionary entries with long lines (#4872)
• Fix possible crash when fmt: directives aren't on the top level (#4856)

Preview style

• Fix fmt: skip skipping the line after instead of the line it's on (#4855)
• Remove unnecessary parentheses from the left-hand side of assignments while preserving
  magic trailing commas and intentional multiline formatting (#4865)
• Fix fix_fmt_skip_in_one_liners crashing on with statements (#4853)
• Fix fix_fmt_skip_in_one_liners crashing on annotated parameters (#4854)
• Fix new lines being added after imports with # fmt: skip on them (#4894)

Packaging

• Releases now include arm64 Windows binaries and wheels (#4814)

Integrations

• Add output-file input to GitHub Action psf/black to write formatter output to a
  file for artifact capture and log cleanliness (#4824)

Highlights

• Enable base 3.14 support (#4804)
• Add support for the new Python 3.14 t-string syntax introduced by PEP 750 (#4805)

Stable style

• Fix bug where comments between # fmt: off and # fmt: on were reformatted (#4811)
• Comments containing fmt directives now preserve their exact formatting instead of
  being normalized (#4811)

Preview style

• Move multiline_string_handling from --unstable to --preview (#4760)
• Fix bug where module docstrings would be treated as normal strings if preceded by
  comments (#4764)
• Fix bug where python 3.12 generics syntax split line happens weirdly (#4777)
• Standardize type comments to form # type: <value> (#4645)
• Fix fix_fmt_skip_in_one_liners preview feature to respect # fmt: skip for compound
  statements with semicolon-separated bodies (#4800)

Configuration

• Add no_cache option to control caching behavior. (#4803)

Packaging

• Releases now include arm64 Linux binaries (#4773)

Output

• Write unchanged content to stdout when excluding formatting from stdin using pipes
  (#4610)

Blackd

• Implemented BlackDClient. This simple python client allows to easily send formatting
  requests to blackd (#4774)

Integrations

• Enable 3.14 base CI (#4804)
• Enhance GitHub Action psf/black to support the required-version major-version-only
  "stability" format when using pyproject.toml (#4770)
• Improve error message for vim plugin users. It now handles independently vim version
• Vim: Warn on unsupported Vim and Python versions independently (#4772)
• Vim: Print the import paths when importing black fails (#4675)
• Vim: Fix handling of virtualenvs that have a different Python version (#4675)