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>

Release Notes

Released on 2026-05-31.

Bug fixes

• Avoid panic for deferred dataclass field annotations (#25444)
• Avoid panic from cycle in function decorator inference (#25475)
• Ignore rejected assignments for synthesized bindings (#25340)
• Infer bool for not applied to dynamic values (#25445)
• Use diagnostic message as tie-breaker when sorting (#25424)

LSP server

• Add call hierarchy support (#25338)
• Add function parentheses completion (#25305)
• Display docs for matching parameter when hovering over the name of an argument passed by keyword (#25283)
• Document completeFunctionParentheses editor setting (#3513)

Diagnostics

• Introduce opt-in missing-override-decorator rule (#25111)
• Improve diagnostics for syntax errors in forward annotations (#25158)
• Improve diagnostic for failed assignment to a Callable type (#25308)

Core type checking

• Narrow bound method overloads by receiver (#24707)
• Add disjointness for protocol method members (#25315)
• Avoid treating metaclass declarations as populated values (#25432)
• Use TypeForm in ty_extensions (#25421)

Performance

• Avoid storing redundant reachability indexes (#25453)
• Compact retained semantic arrays (#25454)
• Remove excess capacity from more Salsa cached collections (#25411)
• Use compact sets for more immutable fields (#25476)
• Use ThinVec for sparse kwargs bindings (#25457)

Contributors

• @sharkdp
• @charliermarsh
• @lerebear
• @AlexWaygood
• @MichaReiser
• @mhuen
• @jelle-openai

Install ty 0.0.41

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.41/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.41/ty-installer.ps1 | iex"

Download ty 0.0.41

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 2026-05-27.

Bug fixes

• Accept complete enum-literal alias unions as enums (#25341)
• Fix diagnostics in ignored folders after adding new files (#25236)
• Show LiteralString when hovering over an inline of a literal string in an IDE (#25373)

LSP server

• Follow aliases when attempting to map a definition in a stub file to its "real" runtime definition (#25328)
• Treat Python notebook text documents as Python sources (#25393)
• Fix autocompletion for elements inside incomplete list comprehensions (#25326)

Diagnostics

• Add a subdiagnostic help message to invalid-generic-class diagnostics regarding incompatible variance (#25385)

Core type checking

• Ignore and reject annotations on non-name targets (#25324)
• Infer class attributes assigned by metaclass initialization (#25342)
• Reject inconsistent generic bases in "dynamic" classes created using type(...), types.new_type(...), etc. (#25413)
• Resolve enum names for all unions arms in Literal enum subsets (#25379)
• Support typing.TypeForm (#25334)
• Fix many issues in the generics solver by using constraint sets more widely to solve type variables (#24540)

Contributors

• @anuraaga
• @dcreager
• @charliermarsh
• @MichaReiser
• @Dev-X25874

Install ty 0.0.40

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.40/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.40/ty-installer.ps1 | iex"

Download ty 0.0.40

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>