Release Notes

Released on 2026-04-20.

Bug fixes

• Fix panic when __get__ uses Concatenate self-type and wraps a __call__ (#24692)
• Avoid panicking on overloaded Callable type context (#24661)
• Expand class bases in per-base lint checks (#24695, #24699)
• Fix stack overflow for binary operator inference involving recursive types (#24551)

LSP server

• Dim out unreachable code in IDEs (#24580)
• Do not suggest argument completion when typing the value of a keyword argument (#24669)
• Retrieve the docstring from the overload implementation if an @overload-decorated function has no docstring (#23920)

Core type checking

• Allow if statements in TypedDict bodies (#24702)
• Disallow @disjoint_base on TypedDicts and Protocols (#24671)
• Do not consider a subclass of a @dataclass_transform-decorated class to have dataclass-like semantics if it has type in its MRO (#24679)
• Reject using properties with Never setters or deleters (#24510)
• Sync vendored typeshed stubs (#24646). Typeshed diff

Diagnostics

• Show error context for assignability diagnostics (#24309)
• Use partially qualified names when reporting diagnostics regarding bad calls to methods (#24560)
• Reduce source code context window to zero (#24689)
• Merge same-file annotations if there is only a single line separating them (#24694)

Performance

• Memoize binary operator return types (#24700)
• Gate protocol compatibility on member count (#24684)

Contributors

• @JelleZijlstra
• @kc0506
• @denyszhak
• @carljm
• @dcreager
• @AlexWaygood
• @dylwil3
• @charliermarsh
• @sharkdp
• @ibraheemdev

Install ty 0.0.32

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.32/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.32/ty-installer.ps1 | iex"

Download ty 0.0.32

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-04-15.

Bug fixes

• Avoid panic from double inference for namedtuple(typename=T, field_names=x, **{}) (#24641)
• Avoid panic from double inference with missing functional Enum(...) names (#24638)
• Avoid panic from double inference with functional Enum(value=...) (#24639)
• Fix cases where invalid-key fix doesn't converge, and override-of-final-method produces invalid syntax (#24649)
• Fix unnecessary ty:ignore comments inserted by --add-ignore for diagnostics starting on the same line (#24651)

CLI

• Add --fix mode to enable auto-fix for diagnostics (#24097)

Performance

• Avoid excessive memory usage for dataclasses with many fields (#24620)

Core type checking

• Check inherited NamedTuple field conflicts (#24542)
• Error when duplicate keywords are provided to TypedDict constructors (#24449)
• Respect mixed positional and keyword arguments in TypedDict constructor (#24448)
• Respect subclass shadowing for inherited NamedTuple fields (#24640)
• Skip EnumMeta.__call__ for enum constructor signatures (#24513)

Contributors

• @sharkdp
• @Glyphack
• @MichaReiser
• @charliermarsh

Install ty 0.0.31

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.31/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.31/ty-installer.ps1 | iex"

Download ty 0.0.31

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-04-13.

As of v0.0.30, ty no longer unions Unknown into most inferred types of unannotated attributes. For example:

class Foo:
    def __init__(self) -> None:
        self.value = 1

reveal_type(Foo().value)  # revealed: int
Foo().value = "x"  # error: [invalid-assignment]

In previous versions, reveal_type(Foo().value) would have included Unknown, so the assignment to "x" would not have been flagged. Since this can affect inferred attribute types throughout a codebase, upgrading may lead to both new and resolved diagnostics. Initializers of None and other non-literal singleton types remain exceptions. See #24531 for details.

Bug fixes

• Disallow bare ParamSpec in Concatenate prefixes (#24474)
• Ensure '/' parameter appears before '*' when rendering Callable types (#24497)
• Ensure nested conditional blocks inherit TYPE_CHECKING state from outer blocks (#24470)
• Fix bad diagnostic range for incorrect implicit __init_subclass__ calls (#24541)
• Fix incorrect assignability of type[T] to a metaclass (#24515)
• Fix stack overflows from recursive types (#24413)
• Server: fix signature help for ParamSpec-specialized class calls (#24399)
• Use TypedDict field types as type context to inform the inference of arguments passed to TypedDict constructors (#24422)

LSP server

• Adjust semantic tokens implementation to ensure that type alias values have "type form" syntax highlighting in IDEs (#24478)
• Completions: rank symbols from typing and collections higher than third party re-exports (#23643)
• Ignore unsupported editor-selected Python versions (#24498)
• Improve TypedDict constructor support in the LSP by synthesizing __init__ (#24476, #24522, #24535)
• Return all attribute definitions for goto definition, rather than just the last definition in the given scope (#24332)
• Show info subdiagnostics in LSP diagnostic messages (#24328)
• Use the context of the kind of object a parameter is expected to receive to inform syntax highlighting of arguments passed to call expressions (#23949)

Diagnostics

• Hide "Rule xyz is enabled"-style hints unless verbose mode was specified (#24469)
• Improve consistency of pedantic lints complaining about badly named types (#24575)
• Point to the first reachable declaration, rather than the first declaration, in declaration-based diagnostics (#24564)

Core type checking

• Add support for functional Enum(...) syntax (#23602, #24570, #24571)
• Allow Final variable assignments in __post_init__ (#24529)
• Allow partially stringified type[...] annotations, e.g. type["MyClass"] (#24518)
• Emit a diagnostic when attempting to inherit from a class with __init_subclass__ = None (#24543)
• Fix TypeGuard and TypeIs narrowing for unbound method calls (#24612)
• Fix assignability of intersections with bounded TypeVars (#24502)
• Fix excess subscript argument inference for non-generic types so that list[int][0] leads to 1 diagnostic, rather than 2 (#24354)
• Inherit dataclass_transform metadata from metaclass bases (#24615)
• Lazily evaluate declaration reachability in field and enum filters (#24451)
• Normalize explicit None accessors in manual property construction (#24492)
• Reject deleting Final attributes (#24508)
• Respect non-required keys in TypedDict unpacking (#24446)
• Respect property deleters in attribute deletion checks (#24500)
• Stop special-casing str constructor (#24514)
• Stop unioning Unknown into types of un-annotated attributes (#24531)
• Support super() in metaclass methods (#24483)
• Tighten up a few edge cases in Concatenate type-expression parsing (#24172)
• Use basic blocks for determining if a node is in an if TYPE_CHECKING block (#24394)

Contributors

• @charliermarsh
• @Glyphack
• @MichaReiser
• @sharkdp
• @carljm
• @YilunAllenChen
• @zanieb
• @AlexWaygood
• @thejchap

Install ty 0.0.30

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.30/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.30/ty-installer.ps1 | iex"

Download ty 0.0.30

Release Notes

Released on 2026-04-05.

Bug fixes

• Avoid special-casing for dataclasses.field if it's not in field_specifiers (#24397)
• Reject unsupported environment.python-version values in configuration files (#24402)
• Respect supported lower bounds from requires-python (#24401)

Core type checking

• Add support for types.new_class (#23144)
• Fix PEP 695 type aliases in with statement (#24395)
• Respect __new__ and metaclass __call__ return types (#24357)
• Treat enum attributes with type annotations as members (#23776)

Contributors

• @charliermarsh
• @carljm

Install ty 0.0.29

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.29/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.29/ty-installer.ps1 | iex"

Download ty 0.0.29

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-04-02.

Bug fixes

• Mark loop header assignments as used to avoid false positives in "unused variable" diagnostics (#24336)

LSP server

• Show constructor signature of classes when hovering over them (#24257)

Core type checking

• Avoid emitting cascading diagnostics when parsing invalid type expressions (#24326)
• Handle most "deep" mutual TypeVar constraints (#24079)
• Improve consistency and quality of diagnostics relating to invalid type forms (#24325)
• Improve robustness of various type-qualifier-related checks (#24251)
• Infer the extra_items keyword argument to class-based TypedDicts as an annotation expression (#24362)
• Use bidirectional inference to fix false positives on operations such as x: list[int | None] = [None] * 2 (#24197)
• Sync vendored typeshed stubs (#24340). Typeshed diff
• Tighten up validation of subscripts and attributes in type expressions (#24329)
• Use infer_type_expression for parsing parameter annotations and return-type annotations (#24353)
• Use infer_type_expression for validating PEP-613 type aliases (#24370)
• Validate TypedDict fields when subclassing (#24338)
• Validate type qualifiers in functional TypedDict fields and the extra_items keyword to functional TypedDicts (#24360)
• Improve diagnostics for invalid functional TypedDicts (#24345)

Contributors

• @zsol
• @dcreager
• @charliermarsh
• @oconnor663
• @AlexWaygood
• @Glyphack

Install ty 0.0.28

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.28/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.28/ty-installer.ps1 | iex"

Download ty 0.0.28

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-03-31.

Bug fixes

• Fix panic on debug builds when attempting to provide autocomplete suggestions for list[int]<CURSOR>() (#24167)
• Fix instance-attribute lookup in methods of protocol classes (#24213)
• Fix nested global and nonlocal lookups through forwarding scopes (#24279)
• Fix panic on list[Annotated[()]] (#24303)
• Fix stack overflow on type A = TypeIs[Callable[[], A]] (#24245)
• Use _cls as the name of the first argument for synthesized collections.namedtuple constructor methods (#24333)

LSP server

• Fix semantic token classification for properties accessed on instances (#24065)
• Grey out unused bindings in the editor (#23305)

Core type checking

• Add bidirectional type context for TypedDict get() defaults (#24231)
• Add bidirectional type context for TypedDict pop() defaults (#24229)
• Add support for functional TypedDict (#24174, #24331, #24295)
• Ban type qualifiers in PEP-695 type aliases (#24242)
• Enforce Final attribute assignment rules for annotated and augmented writes (#23880)
• Improve support for Callable type context (#23888)
• Infer lambda expressions with Callable type context (#22633)
• Don't incorrectly infer the type of a method as being a singleton type when it's accessed off an instance (#24039)
• Propagate type context through await expressions (#24256)
• Resolve union-likes in emitting union attribute errors (#24263)
• Show the user where the variable was declared as Final when emitting a diagnostic about a Final variable being reassigned (#24194)

Contributors

• @carljm
• @mvanhorn
• @oconnor663
• @ibraheemdev
• @zanieb
• @denyszhak
• @Glyphack
• @charliermarsh
• @AlexWaygood

Install ty 0.0.27

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.27/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.27/ty-installer.ps1 | iex"

Download ty 0.0.27

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-03-26.

Bug fixes

• Prevent "too many cycle iteration" panics in more situations (#24061)
• Fix false positives and false negatives when unpacking a union of tuples into a function call (#23298)

Core type checking

• Add support for typing.Concatenate (#23689)
• Validate the return type of generator functions (#24026)
• Support dataclass field converters (#23088)
• Disallow Self in metaclass and static methods (#23231)
• Improve call inference for keyword-only dict() (#24103)
• Respect non-explicitly defined dataclass_transform params (#24170)
• Unconditionally silence diagnostics in unreachable code (#24179)
• Respect terminal-function-call narrowing in global scope (#23245)

Performance

• Fix performance regression for narrowing on a larger Literal type(#24185)

Contributors

• @sharkdp
• @Glyphack
• @charliermarsh
• @mtshiba
• @dhruvmanila
• @carljm
• @choucavalier

Install ty 0.0.26

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.26/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.26/ty-installer.ps1 | iex"

Download ty 0.0.26

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-03-24.

Breaking changes

• Support type:ignore[ty:code] suppressions (#24096)

Bug fixes

• Avoid eager TypedDict diagnostics in TypedDict | dict unions (#24151)
• Fix Salsa panic propagation (#24141)
• Fix folding ranges of comments separated by statements (#24132)
• Fix loop-header reachability cycles in conditional unpacking (#24006)
• Fix subtyping of intersections containing NewTypes of unions vs. unions (#24087)
• Fix untracked reads in Salsa queries that can lead to backdating panics (#24051)
• Prevent tainted loop bindings in cycle normalization (#24143)
• Simplify an intersection of N & ~T to Never if B & ~T would simplify to Never, where B is the concrete base type of a NewType N (#24086)

LSP

• Preserve blank lines between comments and imports in add-import action (#24066)

Type checking

• Add diagnostic hint for invalid assignments involving invariant generics (#24032)
• Add precisely-typed overloads for TypedDict update (#24101)
• Disallow read-only fields in TypedDict updates (#24128)
• Expand bounded typevars to their upper bounds when evaluating truthiness comparisons between intersections and literal types (#24082)
• Emit reveal_type diagnostics in unreachable code (#24070)
• Improve isinstance() reachability analysis (#24077)
• Improve keyword argument narrowing for nested dictionaries (#24010)
• Infer yield expression types (#23796)
• Reduce diagnostic range for invalid-metaclass (#24145)
• Support narrowing for extended walrus targets (#24129)
• Unions/intersections of gradual types should be assignable to Never (#24056)

Contributors

• @MichaReiser
• @AlexWaygood
• @Glyphack
• @sharkdp
• @ibraheemdev
• @charliermarsh
• @mvanhorn
• @carljm

Install ty 0.0.25

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.25/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.25/ty-installer.ps1 | iex"

Download ty 0.0.25

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-03-19.

Bug fixes

• Ensure TypedDict subscripts for unknown keys return Unknown (#23926)
• Fix overflow with recursive TypeIs (#23784)
• Fix variance of frozen dataclass-transform models (#23931)

LSP server

• Improve semantic token classification for attribute access on union types (#23841)

Core type checking

• Improve performance and correctness by avoiding inferring intersection types for call arguments as a result of bidirectional inference (#23933)
• Narrow keyword arguments when unpacking dictionary instances (#23436)
• Discover /usr/local/lib dist-packages on Debian/Ubuntu (#23797)
• Sync vendored typeshed stubs (#23963). Typeshed diff

Install ty 0.0.24

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.24/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.24/ty-installer.ps1 | iex"

Download ty 0.0.24

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo astral-sh/ty

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>

Release Notes

Released on 2026-03-13.

Bug fixes

• Fix false-positive diagnostics for PEP-604 union annotations on attribute targets on Python 3.9 when from __future__ import annotations is active (#23915)
• dataclass_transform: Respect kw_only overwrites in dataclasses (#23930)
• Fix too-many-cycle panics when inferring loop variables with Literal types (#23875)

Server

• Fix folding range classification of lines starting with # (#23831)
• Fix folding ranges for notebooks (#23830)

Core type checking

• Split errors for possibly missing submodules into a new possibly-missing-submodule error code (enabled by default), and make possibly-missing-attribute ignored by default (#23918)
• Improve handling of bidirectional inference when (#23844)
• Fix inference of conditionally defined properties (#23925)

Improvements to diagnostics

• Clarify in diagnostics that from __future__ import annotations only stringifies type annotations (#23928)

Performance improvements

• Avoid duplicated work during multi-inference (#23923)

Contributors

• @ibraheemdev
• @sharkdp
• @oconnor663
• @mtshiba
• @MichaReiser
• @carljm
• @AlexWaygood

Install ty 0.0.23

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.23/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.23/ty-installer.ps1 | iex"

Download ty 0.0.23