Release Notes

Released on 2026-06-18.

Bug fixes

• Fix bound TypeVar default cycle recovery (#26124)
• Support Annotated[Any, ...] as a class base (#26133)

LSP server

• Suggest keyword-only arguments between variadic parameters (#26134)

Core type checking

• Avoid assuming classes with Any or Unknown bases are descriptors (#26120)
• Infer simpler types in complex lambda cycles (#26137)
• Preserve exact class objects during identity narrowing (#26117)

Diagnostics

• Preserve unpacking diagnostics for nested assignment targets (#26121)

Performance

• Compact indexed AST node storage (#25998)
• Discard dead DNF branches in intersection building (#26144)

Documentation

• Remove broken gradual guarantee link (#3806)

Contributors

• @charliermarsh
• @ibraheemdev
• @carljm
• @MichaReiser
• @sharkdp

Install ty 0.0.51

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.51/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.51/ty-installer.ps1 | iex"

Download ty 0.0.51

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 2026-06-17.

Bug fixes

• Avoid cross-TypeVar leakage in generic inference (#26099)
• Fix panic from oscillating collection-use constraints (#26031)
• Preserve type variables in fixed tuple aliases (#26041)
• Respect ParamSpec binding contexts (#25993)
• Show bare Final as a special form on hover (#26029)
• Support options in functional dataclass calls (#25989)

LSP server

• Add context-sensitive keyword completions (#26036)
• Fix wildcard import symbol range (#25740)
• Highlight decorated methods consistently (#26003)
• Preserve narrowing after qualified TYPE_CHECKING (#26051)
• Respect client's content format preference (#25957)
• Retain all diagnostic annotations in the server (#26006)
• Track unused-binding captures across nested scopes (#25536)

Diagnostics

• Fix override diagnostics for decorated methods (#25671)
• Improve duplicate-base diagnostics (#26107)
• Reject invalid dataclass flag combinations (#25985)
• Reject legacy TypeVars in PEP 695 class bases (#25975)
• Reject legacy TypeVars in PEP 695 functions (#25979)
• Respect @no_type_check in function validation (#25994)

Performance

• Avoid rebuilding unchanged specializations (#25826)
• Avoid redundant equality intersections (#26057)
• Avoid retaining empty use-def tables (#26018)
• Compact retained definition inference extras (#25838)
• Deduplicate retained scope inference types (#25846)
• Disable LRU tracking for one-shot checks (#26106)
• Fast path collection literals with exact type contexts (#25878)
• Flatten retained declaration states (#25912)
• Improve flow snapshot performance (#26012)
• Skip stub package checks in stub-free search paths (#25963)
• Speed up large-union narrowing (#26048)
• Speed up module resolution for projects with many search paths (#25962)
• Store cumulative binding end offsets (#25913)
• Use compact frozen representation for narrowing constraints (#25990)

Core type checking

• Annotate intersection and negation types using & and ~ (#26035)
• Diagnose zero-step slices on lists (#25966)
• Full-scope bidirectional inference for non-empty collection literals (#25280)
• Improve equality-based narrowing for ==, !=, and match (#25788)
• Infer precise values for standard-library enums (#26103)
• Make equality evaluation cycle-aware (#26055)
• Narrow equality across IntEnum classes (#26079)
• Narrow tuple expression match subjects (#25874)
• Preserve literal types for loop variables over literal collections (#25083)
• Preserve negative narrowing for starred sequence patterns (#25927)
• Preserve non-final types in Hashable unions (#26039)
• Support enum literals as tagged-union discriminants (#25855)
• Sync vendored typeshed stubs (#25952). Typeshed diff
• Sync vendored typeshed stubs (#25997). Typeshed diff
• Synthesize NamedTuple __match_args__ (#25934)
• Treat assigned enum hooks conservatively (#25958)
• Validate deprecated warning categories (#26025)

Contributors

• @AlexWaygood
• @MichaReiser
• @ankddev
• @sqqueak
• @lerebear
• @sharkdp
• @denyszhak
• @ibraheemdev
• @charliermarsh

Install ty 0.0.50

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.50/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.50/ty-installer.ps1 | iex"

Download ty 0.0.50

Release Notes

Released on 2026-06-11.

Bug fixes

• Fix site-package error when multiple versions of Python are installed in system path (#25769)

Diagnostics

• Point at attribute's binding site in `invalid-await diagnostic (#24628)
• Report redefined legacy TypeVars (#25854)

Performance

• Add dedicated TDDs for narrowing constraints (#25834)
• Avoid caching same-file raw signatures (#25761)
• Cache reachability evaluations during inference (#25696)
• Compact retained definition maps (#25737)
• Omit redundant definition inference owner keys (#25837)

Core type checking

• Preserve nominal type of enum.property instances (#25849)
• Restrict length narrowing to types that encode their length (#25840)
• Use peer context for collection literals (#25848)

Contributors

• @charliermarsh
• @anishgirianish
• @cheparity
• @carljm

Install ty 0.0.49

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.49/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.49/ty-installer.ps1 | iex"

Download ty 0.0.49

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 2026-06-10.

Performance

• Avoid redundant constraint saturation work (#25786)

Core type checking

• Add support for TypedDict extra_items (#25591)
• Improve closed=True TypedDict precision (#25651)
• Require subtyping for transitive constraint pivots (#25778)
• Sync vendored typeshed stubs (#25828). Typeshed diff

Contributors

• @charliermarsh
• @MichaReiser

Install ty 0.0.48

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.48/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.48/ty-installer.ps1 | iex"

Download ty 0.0.48

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 2026-06-10.

Bug fixes

• Avoid panicking on encountering a recursive NamedTuple that references a recursive NewType (#25764)
• Fix out-of-bound panic in notebooks involving suppression comments (#25629)

Core type checking

• Preserve overloads through callable protocol decorators (#25806)
• Sync vendored typeshed stubs (#25779). Typeshed diff

Performance and memory-usage improvements

• Avoid caching specialization-invariant known instances (#25816)
• Avoid resolving overload sets for ordinary functions (#25817)
• Store common definition inference results inline (#25814)
• Use Box<SystemPath> etc. in Files (#25554)

Contributors

• @dhruvmanila
• @MichaReiser
• @charliermarsh

Install ty 0.0.47

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.47/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.47/ty-installer.ps1 | iex"

Download ty 0.0.47

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 2026-06-08.

Bug fixes

• Avoid crash when hovering over Callable (#25759)

Core type checking

• Support Callable() in match statement class patterns (#25541)
• Improve support for enum.property (#25681)

Contributors

• @carljm
• @charliermarsh
• @thejchap

Install ty 0.0.46

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.46/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.46/ty-installer.ps1 | iex"

Download ty 0.0.46

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 2026-06-08.

Bug fixes

• Avoid treating dynamic class attributes as instance attributes (#25678)
• Fix divergence in recursive inference due to ambiguous overload (#25548)
• Preserve literal promotion for mixed bounds (#25648)

Diagnostics

• Add missing-type-argument lint rule (#25617)

Core type checking

• Add support for narrowing on tuple match cases (#25493)
• Check implicit open TypedDict extra items (#25628)
• Create fresh copies of generic callable typevars (#24949)
• Preserve deprecation on replacement functions (#25688)
• Preserve intersection receivers during attribute lookup (#25626)
• Preserve transparent callable decorators (#25030)

Performance

• Avoid AST load for callable description names (#25728)
• Avoid caching absent class decorators and type parameters (#25689)
• Avoid caching atomic type specializations (#25663)
• Avoid caching constant constraint relations (#25656)
• Avoid caching missing implicit attributes (#25649)
• Avoid caching trivial class-header queries (#25692)
• Avoid caching trivial member lookups (#25661)
• Bypass member lookup for module imports (#25723)
• Cache constraint implication checks (#25714)
• Cache upper-bound satisfiability (#25710)
• Compact retained function type signatures (#25669)
• Compact retained use-def bindings (#25682)
• Consolidate retained narrowing constraints (#25660)
• Construct trivial constraint sets directly (#25659)
• Resolve function descriptors directly (#25675)
• Share code-generator classification across specializations (#25701)
• Share parameter lists with Arc (#25735)
• Use same-file expression inference in reachability (#25694)

Contributors

• @mtshiba
• @dhruvmanila
• @charliermarsh
• @dcreager
• @carljm
• @reginaldl

Install ty 0.0.45

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.45/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.45/ty-installer.ps1 | iex"

Download ty 0.0.45

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 2026-06-04.

Bug fixes

• Avoid treating sys.implementation.version like sys.version_info (#25608)
• Fix anchor point for override diagnostics (#25621)

LSP server

• Show type alias value on hover (#25381)

Performance

• Add caching for pattern match narrowing (#25613)
• Compact retained definition and expression identities (#25606)
• Reuse expression cache for TypedDict union inference (#25643)
• Upgrade Salsa (#25545)

Core type checking

• Enable narrowing for unions of TypedDict (#25188)

Contributors

• @lerebear
• @MichaReiser
• @carljm
• @pierrem964
• @charliermarsh
• @Hugo-Polloli

Install ty 0.0.44

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.44/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.44/ty-installer.ps1 | iex"

Download ty 0.0.44

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 2026-06-03.

Bug fixes

• Don't inject Unknown from non-callable elements of intersection call (#25538)
• Don't needlessly disambiguate the same type alias (#25563)
• Fix variance inference for nested type aliases (#25567)
• Ignore rejected member annotations for synthesized bindings (#25427)
• Normalize dynamic class literals in cycle recovery (#25558)
• Register file roots for first-party search paths (#25522)
• Treat union-bound typevars like unions for possibly-missing-attribute (#25561)

LSP server

• Suppress importable completions that are already in scope (#25479)

Performance

• Avoid retaining duplicate function signatures (#25609)
• Compact retained definition inference results (#25593)
• Compact retained definition kinds (#25610)
• Compact retained definitions by node (#25498)
• Consolidate AST ID reverse lookup (#25455)
• Consolidate retained use-def definition maps (#25499)
• Omit redundant definitions-by-node entries (#25501)
• Reuse common protocol constraints for TypedDict unions (#25598)

Diagnostics

• Improve error context for not-iterable diagnostics (#24944)

Core type checking

• Detect disjointness due to incompatible generic specializations (#24822)
• Distinguish typing.Callable from collections.abc.Callable (#24954)
• Include nested global/nonlocal bindings in type inference (#25387)
• Optional lower/upper bounds in individual constraints (#25435)
• Preserve slice-bound types in subscript inference (#25446)
• Reject Self in type aliases (#25529)
• Require literal booleans for TypedDict flags (#25594)
• Support narrowing on lengths (#25347)
• Synthesize precise __len__ methods for literals (#25600)
• Use callable type context to implicitly specialize generic class (#25471)
• expand type aliases inside type context unions (#25553)

Contributors

• @carljm
• @cheparity
• @kouhe3
• @sharkdp
• @charliermarsh
• @dcreager
• @thejchap
• @oconnor663

Install ty 0.0.43

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.43/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.43/ty-installer.ps1 | iex"

Download ty 0.0.43

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 2026-06-01.

Bug fixes

• Fix narrowing of enum literal unions by member identity (#25520)
• Detect recursive expansion in constraint-set solving (#25442)

Core type checking

• Support tagged-union narrowing for nominal types (#24916)
• Extend Generator assignability workaround to Python 3.13+ (#25472)
• Sync vendored typeshed stubs (#25514)

Performance

• Avoid redundant work for empty collection context (#25527)
• Deduplicate retained use-def place states (#25450)
• Compact retained semantic maps (#25238)

Contributors

• @aholyoke
• @carljm
• @charliermarsh
• @sharkdp

Install ty 0.0.42

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.42/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.42/ty-installer.ps1 | iex"

Download ty 0.0.42

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>