Release Notes

Released on 2026-02-26.

Bug fixes

• Fix panic in diagnostic rendering when attempting to render a code frame pointing to leading whitespace (#23458)
• Fix panics and incorrect inference stemming from incorrectly considering overloads in another file as being associated with a function in the file being checked (#21977)
• Fix panic when attempting to narrow the type of a dictionary key that was assigned using a multi-target assignment, e.g. x = y = {"a": 1} (#23523)
• Fix infinite hang on mutually recursive TypeAliasType definitions (#23397)

LSP server

• Fix inlay hints for starred unpacking targets (#23454)

Core type checking

• Fix assignability, subtyping and equivalence checks relating to typing.Generator prior to Python 3.13 (#23386)
• Understand that a scope's control flow terminates after await foo() if foo returns typing.Awaitable[typing.Never] or similar (#23479)
• Implement stricter handling of calls to instances of type[T] types (#23472)
• Support basic type narrowing for case {...}: patterns in match statements (#23462)
• Fix bugs that could manifest in incorrect overload evaluation, false-positive complaints regarding assert_type calls or false-positive redundant-cast diagnostics by reimplementing the equivalence type relation as mutual subtyping of top and bottom materializations (#23428)
• Fix equality and __contains__ narrowing with PEP-695 type aliases (#23545)
• Support _value_ annotations on enum classes (#22228)

Improvements to diagnostics

• Improve diagnostics when attempting to specialize non-generic types (#23516)
• Render subdiagnostics when --output-format=github is specified (#23455)

Performance

• Add a cached method for calculating the intersection of two types (#23547)
• Add a cached method for calculating the union of two types (#23565)
• Reduce the threshold above which Literal types in unions are upcasted to nominal-instance types in situations where the union type is recursively defined (#23521)
• Control flow: isolate the calculation of "loop header reachability" in a dedicated, cached function (#23520)

Contributors

• @AlexWaygood
• @silamon
• @ibraheemdev
• @Hugo-Polloli
• @charliermarsh
• @knutwannheden
• @oconnor663
• @carljm
• @mtshiba

Install ty 0.0.19

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.19/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.19/ty-installer.ps1 | iex"

Download ty 0.0.19

Release Notes

Released on 2026-02-20.

Bug fixes

• Support classes dynamically created via type(...) with cyclic bases (#22792)
• Fix incorrect types inferred when unpacking mixed tuples (#23437)
• Fix stack overflow for self-referential TypeOf in annotations (#23407)
• Fix several server panics that could occur when computing semantic tokens for the current file (#23403), #23398, #23401)

LSP server

• Add code folding support (#23393)
• Add warning message when running ty server interactively (#23416)
• Exclude test-related symbols from non-first-party packages in auto-import completions (#23252)
• Fix bug where diagnostics could disappear after opening an external file (#23447)
• Remove spurious destination for Go-To Definition on variables defined in a loop (#23391)
• Use the fully qualified name when "baking" an inlay hint into the source code if the scope already contains a variable with the same name as the unqualified name (#23265)
• Resolve TypeVars in call_signature_details parameter types (#23149)

CLI

• Add --output-format to ty version (#23387)

Configuration

• Add replace-imports-with-any option (#23122)
• Support shellexpand for configuration paths (#23274)

Type checking

• Add a new diagnostic to detect invalid class patterns in match statements (#22939)
• Allow Self in ClassVar type annotations (#23362)
• Consider synthesized methods and ClassVar-qualified declarations when determining whether an abstract method has been overridden in a subclass (#23381)
• Add a diagnostic when combining Final and ClassVar (#23365)
• Fix return type of assert_never (#23389)
• Fix assert_type diagnostic messages (#23342)
• Ban PEP-613 type alias values from containing type-qualifier special forms (#23444)
• Infer LiteralString for f"{literal_str_a} {literal_str_b}" (#23346)
• Infer precise types for bit-shift operations on integer literals (#23301)
• Make [abstract-method-in-final-class] diagnostics less verbose for classes with many abstract methods (#23379)
• Improve diagnostics for abstract @final classes (#23376)
• Only perform literal promotion for implicitly inferred literals (#23107)
• Parenthesize callable types when they appear in the return annotation of other callable types (#23327)
• Consider a call to a generic function returning Never to terminate control flow (#23419)
• Support calls to intersection types (#22469)
• Validate annotated assignments to attributes on self (#23388)
• Treat a bytes-literal type as a subtype of Sequence[<constituent integers in the bytestring>] (#23329)
• Allow a string-literal argument to match against an Iterable parameter in type variable inference. (#23326)
• Support narrowing from a Callable type returning a TypeGuard type (#23280)

Performance

• Consider all code paths as being ambiguously reachable in cases with pathologically large control-flow graphs (#23399)

Typeshed

• Sync vendored typeshed stubs (#23279, Typeshed diff)

Contributors

• @toby-bro
• @Hugo-Polloli
• @MatthewMckee4
• @BurntSushi
• @ibraheemdev
• @knutwannheden
• @Glyphack
• @charliermarsh
• @AlexWaygood
• @abhijeetbodas2001
• @carljm
• @sharkdp

Install ty 0.0.18

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.18/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.18/ty-installer.ps1 | iex"

Download ty 0.0.18

Release Notes

Released on 2026-02-13.

Bug fixes

• Avoid Literal promotion for constrained TypeVars with Literal bounds (#23209)
• Fix false positives in TypeVar shadowing checks (#23222)

Core type checking

• Support generic protocols (#21902)
• Perform control-flow analysis in loops (#22794)
• Support typing.Self in attribute annotations (#23108)
• Support type narrowing in situations with calls to NoReturn functions (#23109)
• Support type narrowing and reachability analysis based on os.name checks (#23230)
• Detect overrides of Final class variables in subclasses (#23180)
• Fix bound method access on None (#23246)
• Fix method calls on subclasses of Any (#23248)
• Disallow type variables within PEP-695 type variable bounds and constraints (#22982)
• Emit error for attribute access on union where some elements lack the attribute (#23042)
• Emit error for invalid typevar defaults (#23194)
• Improve display of ParamSpecs in some situations (#23211)

LSP server

• Add hover and go-to-declaration support for subscript literals (#22837)
• Assign lower completion ranking to deprecated names in auto import (#23188)
• Improve spans of references to submodules imported in an __init__.py (#21795)
• Include conditional symbols (like datetime.UTC) in auto-import in more cases (#23249)
• Support auto-import for symbols in inlay hints (#22111)
• Include overload declarations in find-references (#23215)

Performance

• Avoid UnionBuilder overhead when creating a new union from the filtered elements of an existing union (#22352)

Other changes

• Allow discovering dependencies in system Python environments (#22994)
• Apply workspace settings to virtual files (#23228)
• Add support for --output-format=junit (#22125)
• Use a smaller diagnostic range for inconsistent-mro diagnostics (#23213)

Contributors

• @carljm
• @BurntSushi
• @charliermarsh
• @Glyphack
• @cetanu
• @AlexWaygood
• @joelostblom
• @Gankra
• @mtshiba
• @MatthewMckee4
• @Hugo-Polloli
• @sharkdp
• @alex
• @dcreager
• @oconnor663

Install ty 0.0.17

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.17/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.17/ty-installer.ps1 | iex"

Download ty 0.0.17

Release Notes

Released on 2026-02-10.

Bug fixes

• Allow stringified argument in PEP-613 alias to Optional (#23200)
• Fix fuzzer panic on slice expression in unclosed comprehension (#23146)
• Fix combinatorial explosion due to fixed-length tuple expansion in overload matching (#23190)
• Respect @no_type_check when combined with other decorators (#23177)
• Fix diagnostic location for an incorrect sub-call to a specialized ParamSpec (#23036)

LSP server

• Assign lower completions ranking to deprecated functions and classes (#23089)
• Change goto-def for class constructors to always go to class definition (#23071)
• Ensure diagnostic mode is consistent across projects inside the LSP server (#23121)
• Don't include the class Foo in autocomplete suggestions when the user is typing out Foo's bases (#23141)
• Fix parameter references across files via keyword args (#23012)
• Fix wrong inlay hints for overloaded function arguments (#23179)
• Support diagnostics in newly created files inside neovim (#23095)
• Exclude already-included classes when providing completion suggestions for class bases (#23085)

CLI

• Add support for TY_OUTPUT_FORMAT environment variable (#23123)
• Fall back to python3 found in $PATH if no environment is found (#22843)

Type checking

• Add inconsistent-mro autofix to move Generic[] to the end of the bases list (#22998)
• Add precise return-type inference for struct.unpack (#22562, #23130)
• Disallow TypeVars within ClassVars (#23184)
• Emit diagnostic on unbound call to abstract @classmethod or @staticmethod (#23182)
• Fix false-positive diagnostics when providing the total= keyword to TypedDict classes that had PEP-695 type parameters (#23114)
• Narrow both left- and right-hand operands where possible (#23084)
• Narrow chained operators (#23093)
• Narrow equality subscripts on either operand (#23104)
• Recognize __dataclass_transform__ to support SQLModel (#23070)
• Relax the attribute narrowing condition to support deeper-nested attribute type narrowing (#22440)
• Support constrained TypeVar compatibility across function boundaries (#23103)
• Support comparison methods (__gt__, etc.) where a parameter is annotated with a Literal type (#23100)
• Support partially specialized type context (#22748)
• Use type context when inferring constructor argument types (#23139)
• Validate TypedDict constructor calls for generic aliases and type[...] targets (#23113)

Performance

• Conservative narrowing places optimization (#22734)

Contributors

• @rbange
• @rayzeller
• @charliermarsh
• @11happy
• @figsoda
• @mtshiba
• @ibraheemdev
• @ngnpope
• @sakgoyal
• @oconnor663
• @ericmarkmartin
• @Hugo-Polloli
• @Glyphack
• @sharkdp
• @carljm
• @BurntSushi

Install ty 0.0.16

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.16/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.16/ty-installer.ps1 | iex"

Download ty 0.0.16

Release Notes

Released on 2026-02-04.

Bug fixes

• Add support for resolving imports of packages installed into Debian/Ubuntu dist-packages directories (#22466)
• Avoid not-iterable false positives when iterating over an instance of an intersection type with only negated elements (#22089)
• Fix support for stringized annotations in very large files (#22913)
• Don't emit Liskov diagnostics for methods with mangled names (#23062)
• Enforce that a Final symbol cannot be reassigned even after a conditional binding (#22986)
• Fix TypedDict construction from existing TypedDict values (#22904)
• Fix Self resolution for classes nested within methods (#22964)
• Fix bidirectional inference with PEP 695 union type aliases (#22988)
• Fix edge-case bugs when narrowing tagged unions in match statements (#22870)
• Fix false-positive diagnostics when iterating over an instance of an intersection that includes a TypeVar of which the upper bound is a union where the union includes a non-iterable type (#22117)
• Fix lookup of __contains__ to respect descriptors (#23056)
• Fix narrowing of nonlocal variables with conditional assignments (#22966)
• Fix several bugs that could affect NewTypes of NewTypes of float (#22997)
• Fix several type narrowing bugs involving PEP-695 type aliases (#22894)
• Fix spurious query cycles in decorated functions with parameter defaults, for improved performance and improved determinism (#23014)
• Fix unary and comparison operators for TypeVars with union bounds (#22925)
• Understand functions as method descriptors even if they are decorated with a decorator annotated as returning a PEP-695 alias to a Callable type (#22902)
• dataclass_transform: Fix visibility of field specifiers when models are nested inside methods (#23069)

LSP server

• Fix hover showing Unknown for bare Final instance attributes (#23003)
• Improve support for goto-type, goto-declaration, hover, and highlighting of string annotations (#22878)
• Include setters and deleters when renaming properties (#22999)
• Show type qualifiers like Final in on-hover hints (#23005)

Configuration

• Add new unused-type-ignore-comment rule (#22790)
• Add a mechanism to ignore/warn/select all rules (#22832)
• Support multiple workspace folders in a single ty LSP server instance (#22953)
• Only add ./src as a search path if ./src/__init__.py(i) does not exist (#22851)

Type checking

• Add a diagnostic detecting if a variable is declared as Final but never has any bindings (#23001)
• Add a diagnostic detecting overridden comparison dunder methods on order=True dataclasses (#22689)
• Add a hint to invalid-argument-type and invalid-assignment diagnostics if a variable is annotated with a type from the numbers module (#22931, #22938)
• Add diagnostic hint on unresolved-reference to suggest using "list" instead of "List" (#22827)
• Add new diagnostic for invalid dataclass field orders (#19825)
• Allow a subclass method with a positional-only parameter to override a superclass method without that parameter if the parameter in the subclass method has a default value (#23037)
• Allow self-referential imports outside the global scope (#22963)
• Ban ... in odd places inside tuple specializations (#22889)
• Ban Required, NotRequired and ReadOnly in parameter annotations (#22888)
• Ban legacy TypeVar bounds or constraints from containing type variables (#22949)
• Ban multiple unpacked variadic tuples in a tuple specialization (#22884)
• Detect generic Callables in the return type of function signatures (#22954)
• Detect invalid isinstance() and issubclass() calls against TypedDict classes (#22887)
• Detect invalid issubclass() calls against Protocol classes with non-method members (#22896)
• Detect invalid attempts to subclass Protocol[] and Generic[] simultaneously (#22948)
• Emit a diagnostic on incorrect applications of the legacy convention for specifying positional-only parameters (#22943)
• Emit an error if a TypeVarTuple is used to subscript Generic or Protocol without being unpacked (#22952)
• Fallback to metaclass __getattr__ or __getattribute__ when looking up attributes on class objects (#22985)
• Fix a bug where an overridden type in a dataclass subclass would not be respected if the dataclass subclass field had a default value but the superclass field did not (#22965)
• Improve bidirectional type inference involving PEP-695 type aliases (#22989)
• Improve detection of invalid NewTypes with generic bases (#22961)
• Improve reachability analysis when evaluating the truthiness of expressions that involve variables that may not be bound in all code paths (#22971)
• Improve the error message if ** is used with a non-mapping in the context of a call to an overloaded function (#22921)
• Infer ParamSpec from class constructors for callable protocols (#22853)
• Move the location of some invalid-overload diagnostics (#22933)
• Point to an overload with an invalid @final decorator when emitting invalid-overload errors for invalid @final decorators (#22893)
• Avoid false positives when iterating over an instance of an intersection with only negated elements by preserving "pure negation" types in descriptor lookups (#22907)
• Promote Literal types when inferring elements for very large unannotated tuples, for improved performance (#22841)
• Recognize functions with stub bodies in Protocol classes as implicitly abstract (#22838)
• Reduce false positives involving heterogeneous dicts by tracking dictionary literal keys as individual places (#22882)
• Reduce false positives when subscripting classes generic over TypeVarTuples (#22950)
• Remove special handling for Any() in match class patterns (#23011)
• Support type[None] in type expressions (#22892)
• Support legacy namespace packages declared using pkg_resources.declare_namespace (#22987)
• Sync vendored typeshed stubs (#23006), Typeshed diff
• Validate signatures of dataclass __post_init__ methods (#22730)

Contributors

• @charliermarsh
• @stefanvanburen
• @ibraheemdev
• @abhijeetbodas2001
• @MichaReiser
• @dcreager
• @PrettyWood
• @sharkdp
• @oconnor663
• @Feiyang472
• @denyszhak
• @mtshiba
• @AlexWaygood
• @11happy
• @BurntSushi
• @carljm
• [@Gankra](...

Release Notes

Released on 2026-01-26.

Bug fixes

• Consider keyword arguments when unpacking a variadic argument (#22796)
• Fix binary operator false-positive for constrained TypeVars (#22782)
• Fix docstring rendering for literal blocks after doctests (#22676)
• Fix false-positive unsupported-operator for "symmetric" TypeVars (#22756)
• Fix panic when overriding a final method using an assignment (#22831)
• Fix unary operator false-positive for constrained TypeVars (#22783)
• Fix generic functions with a generic (ParamSpec) decorator (#22544)
• Fix memo.changed_at assertion panics (#22498)

LSP server

• Look up attributes on metaclasses for Go to Definition (#22758)
• Suppress type inlay hints for leading-underscore assignments (#22855)

Configuration

• Add allowed-unresolved-imports setting (#22800)

Other changes

• Add assert-type-unspellable-subtype diagnostic, for failed assert_type() where the actual type is a subtype of the named type that can't be spelled in a type expression (#22815)
• Add a new empty-body return code for functions with stub bodies that have non-None return annotations (#22846)
• Add diagnostic disambiguation for different type aliases with the same name (#22852)
• Add support for dict literals and dict() calls as default values for parameters with TypedDict types (#22161)
• Add support for subscripts on intersections (#22654)
• Avoid duplicate syntax errors for await outside functions (#22826)
• Emit an error if the same type parameter appears more than once in a Generic[] subscript (#22738)
• Emit diagnostic for unimplemented abstract method on @Final class (#22753)
• Fix GitLab Code Quality output format for empty diagnostics (#22833)
• Fix assignment in decorated method causing Unknown fallback (#22778)
• Fix false negative when using a non-runtime-checkable protocol in a match class pattern (#22836)
• Improve completion rankings for raise-from/except contexts (#22775)
• Improve invalid assignment diagnostics with type context (#22643)
• Improve support for kwarg splats in dictionary literals (#22781)
• Infer TypedDict types with >=1 required key as being always truthy (#22808)
• Point to an overload with an invalid @final decoator when emitting invalid-overload errors for invalid @final decorators (#22812)
• Require both *args and **kwargs when calling a ParamSpec callable (#22820)
• Stricter validation of TypedDict definitions (#22811)
• Support recursive and stringified annotations in functional typing.NamedTuples (#22718)
• Support solving generics involving PEP 695 type aliases (#22678)
• Use a more lenient fallback type for failed namedtuple() and NamedTuple calls (#22765)
• Use type context from augmented assignment dunder calls (#22540)
• Check that starred arguments in function calls are iterable (#22805)

Contributors

• @AlexWaygood
• @maifeeulasad
• @RasmusNygren
• @ntBre
• @Imbuzi
• @dhruvmanila
• @ibraheemdev
• @carljm
• @Hugo-Polloli
• @charliermarsh
• @MichaReiser
• @bxff
• @felixscherz
• @denyszhak

Install ty 0.0.14

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.14/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.14/ty-installer.ps1 | iex"

Download ty 0.0.14

Release Notes

Released on 2026-01-21.

Bug fixes

• Fix --force-exclude when excluding entire directories (#22595)
• Fix missing syntax highlighting for aliased import names (#22675)
• Highlight interpolated-parts in t-strings (#22674)
• Fix the inferred MRO of functional namedtuple classes (#22722)
• Make special cases for subscript inference exhaustive, ensuring that the special casing for tuple subscripts is applied when a union of tuples or an alias to a tuple type is subscripted (#22035)

LSP server

• Improve completion suggestions inside class definitions (#22571)
• Improve performance of completions (#22630)
• Remove completion suggestions for redundant re-exports that share the same top-most module (#22581)

Core type checking

• Add basic support for overloads in ParamSpec (#21946)
• Allow ... as a default value for any parameter if the function is in an if TYPE_CHECKING block (#22624)
• Allow if type(x) is Y narrowing for types other than class-literal types (#22729)
• Avoid overload errors when detecting dataclass-on-tuple (#22687)
• Avoid reporting overload errors for successful union variants (#22688)
• Ban NewTypes with generic bases (#22653)
• Fix PEP 695 type aliases not expanding in overload resolution (#22589)
• Fix the return type for synthesized NamedTuple.__new__ methods (#22625)
• Emit diagnostics for NamedTuple, TypedDict, Enum or Protocol classes decorated with @dataclass (#22672)
• Emit invalid-type-form diagnostics for stringified annotations where the quoted expression is invalid (#22752)
• Infer the implicit type of cls in __new__ methods (#22584)
• Make ModuleType and object attributes available on namespace packages (#22606)
• Make NamedTuple(...) and namedtuple(...) calls stricter (#22601)
• Narrow on bool and byte subscripts (#22684)
• Narrow on negative subscript indexing (#22682)
• Override __file__ to str when applicable on imported modules (#22333)
• Add bidirectional inference for comprehensions (#22564)
• Recognize string-literal types as subtypes of Sequence[Literal[chars]] (#22415)
• Add right-hand-side narrowing for if Foo is type(x) expressions (#22608)
• Add simple syntactic validation for the right-hand side of PEP-613 type aliases (#22652)
• Add support for passing typename and field_names by keyword argument to collections.namedtuple() calls (#22660)
• Add support for starred unpacking in class bases (#22591)
• Validate constructor arguments when a class is used as a decorator (#22377)
• Validate field names for typing.NamedTuple(...) (#22599)
• Add diagnostic on overridden __setattr__ and __delattr__ in frozen dataclasses (#21430)
• Fix unary operators on NewTypes of float or complex (#22605)

Configuration

• Support overriding respect-type-ignore-comments (#22615)

Diagnostics

• Don't add a subdiagnostic pointing to the TypeVar definition if the TypeVar is Self (#22646)
• Show final search path instead of "and 1 more paths" (#22776)
• Group type[] elements together when displaying union types (#22592)

Performance

• Cache ClassType::nearest_disjoint_base (#22065)

Other changes

• Sync vendored typeshed stubs (#22590, Typeshed diff

Contributors

• @bxff
• @jhartum
• @thejchap
• @AlexWaygood
• @charliermarsh
• @RasmusNygren
• @mswart
• @MatthewMckee4
• @11happy
• @ibraheemdev
• @sinon
• @MichaReiser
• @carljm
• @BurntSushi
• @dhruvmanila
• @oconnor663
• @zanieb

Install ty 0.0.13

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.13/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.13/ty-installer.ps1 | iex"

Download ty 0.0.13

Release Notes

Released on 2026-01-14.

Bug fixes

• Avoid panic that could occur when casting an object to a TypedDict or union of TypedDicts (#22509)
• Fix incorrect narrowing for if type(x) == y (#22531)
• Fix stack overflow with recursive type aliases containing tuple types (#22543)
• functools.total_ordering: ensure the signatures of generated methods reflect the signature of the user-provided method (#22496)
• Support dataclass_transform as a function call (#22378)
• Use the top materialization of classes for if type(x) is y narrowing. For example, if type(x) is tuple will cause the type of x to be intersected with tuple[object, ...] rather than tuple[Unknown, ...]. (#22553)
• Avoid emitting Liskov violations with respect to a grandparent class if such violations could not be fixed without introducing Liskov violations with respect to a parent class (#22484)
• Fix interaction between classmethod, contextmanager, and Self (#22407)
• Check contravariant type variable bounds contravariantly in specialization inference (#22488)
• Fix false positive for bounded type parameters with NewType (#22542)

Type checking

• Add support for dynamic type() classes (#22291, #22499, #22537, #22480)
• Add support for functional namedtuple creation (#22327, #22573, #22575, #22574)
• Add a diagnostic for non-decorator uses of final (#22555)
• Add diagnostic to catch generic enums (#22482)
• Add diagnostics for __init_subclass__ argument mismatch (#22185)
• Add diagnostics to validate TypeIs and TypeGuard definitions (#22300)
• Apply type narrowing to walrus targets (#22369)
• Detect invalid @total_ordering applications in non-decorator contexts (#22486)
• Fix @Todo type for starred expressions (#22503)
• Improve disambiguation of types in diagnostics (#22547)
• Include type parameters in the display for generic Callable types (#22435)
• Infer type[Unknown] for calls to type() when overload evaluation is ambiguous (#22569)
• Support assignment to unions of TypedDicts (#22294)
• Use the key and value parameter types as type context for __setitem__ dunder calls (#22148)
• Narrow the right-hand side of ==, !=, is and is not conditions when the left-hand side is not narrowable (#22511)

LSP server

• Fix __file__ type in completions to show str instead of str | None when the inferred type is str (#22510)
• Improve rendering of ReST directives in docstrings (#22512)

Contributors

• @eclbg
• @RasmusNygren
• @carljm
• @drbh
• @AryanBagade
• @bxff
• @ibraheemdev
• @charliermarsh
• @AlexWaygood

Install ty 0.0.12

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.12/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.12/ty-installer.ps1 | iex"

Download ty 0.0.12

Release Notes

Released on 2026-01-09.

Bug fixes

• Fix super() with TypeVar-annotated self and cls parameter (#22208)
• Only consider fully static pivots when deriving transitive constraints (#22444)

LSP server

• Don't show diagnostics for excluded files (#22455)
• Fix goto definition for relative imports in third-party files (#22457)
• Improve completion ranking based on origin and exact match (#22460)
• Rank top-level module symbols above most other symbols (#22465)

Configuration

• Enable unused-ignore-comment by default (#22474)

Performance

• Improve UnionBuilder performance by changing Type::is_subtype_of calls to Type::is_redundant_with (#22337)
• Optimize union building for unions with many enum-literal members (#22363)-

Other changes

• Declare support for Python 3.14 (#2407)
• Remove dark-mode handling from PyPI-uploaded README (#2422)

Contributors

• @dhruvmanila
• @AlexWaygood
• @charliermarsh
• @BurntSushi
• @MichaReiser
• @dcreager

Install ty 0.0.11

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.11/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.11/ty-installer.ps1 | iex"

Download ty 0.0.11

Release Notes

Released on 2026-01-07.

Due to an error in our wheel metadata, this release was partially published to PyPI and manually finished. Consequently, PyPI temporarily did not include all of the artifacts and the GitHub Release was published by a maintainer instead of GitHub Actions. The artifacts from GitHub Actions were used without alteration. The GitHub release attestations for the artifacts are not available for this release.

Bug fixes

• Fix stack overflow due to too small stack size (#22433)
• Fix stale semantic tokens after opening the same document with new content (#22414)
• Fix handling of ParamSpec in overloaded functions (#22416)
• Fix comparisons and arithmetic with NewTypes of float (#22105)
• Fix several issues with unannotated function return types (#22425)
• Fix handling of subclasses in Callables (#22411)

LSP server

• Add support for explicit markdown code fences in docstring rendering (#22373, #22408)
• Offer completions for T when a value has type Unknown | T (#22436)
• Sort keyword argument completions higher (#22297)

Core type checking

• Add support for @total_ordering (#22181, #22183)
• Better simplification of intersections of tuples (#22094)
• Support comparisons between variable-length tuples (#21824)
• Emit diagnostics for method definitions and other invalid statements in TypedDict class bodies (#22351)
• Improve type-narrowing in calls to len() (#22330)

CLI

• Add --add-ignore CLI option (#21696)

Configuration

• include = ["myscript"] will now check myscript even though it doesn't have a Python extension (#22243)

Performance

• Optimize intersections with a single negated element (#22344)
• Optimize negated types (#22402)

Documentation

• Link to Callable __name__ FAQ directly from unresolved-attribute diagnostic (#22437)

Contributors

• @dhruvmanila
• @charliermarsh
• @oconnor663
• @BurntSushi
• @RasmusNygren
• @carljm
• @Gankra
• @MichaReiser
• @AlexWaygood

Install ty 0.0.10

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.10/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.10/ty-installer.ps1 | iex"

Download ty 0.0.10