diff --git a/crates/ruff_graph/src/db.rs b/crates/ruff_graph/src/db.rs
index 9626b63b6d..06b3eca96c 100644
--- a/crates/ruff_graph/src/db.rs
+++ b/crates/ruff_graph/src/db.rs
@@ -9,8 +9,8 @@ use ruff_db::{Db as SourceDb, Upcast};
 use ruff_python_ast::PythonVersion;
 use ty_python_semantic::lint::{LintRegistry, RuleSelection};
 use ty_python_semantic::{
-    Db, Program, ProgramSettings, PythonPath, PythonPlatform, SearchPathSettings,
-    default_lint_registry,
+    Db, Program, ProgramSettings, PythonPath, PythonPlatform, PythonVersionSource,
+    PythonVersionWithSource, SearchPathSettings, default_lint_registry,
 };
 
 static EMPTY_VENDORED: std::sync::LazyLock<VendoredFileSystem> = std::sync::LazyLock::new(|| {
@@ -44,7 +44,10 @@ impl ModuleDb {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: PythonVersionWithSource {
+                    version: python_version,
+                    source: PythonVersionSource::default(),
+                },
                 python_platform: PythonPlatform::default(),
                 search_paths,
             },
diff --git a/crates/ty/docs/rules.md b/crates/ty/docs/rules.md
index 5acf281cce..7cc1eb9ef0 100644
--- a/crates/ty/docs/rules.md
+++ b/crates/ty/docs/rules.md
@@ -50,7 +50,7 @@ Calling a non-callable object will raise a `TypeError` at runtime.
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20call-non-callable)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L87)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L88)
 </details>
 
 ## `conflicting-argument-forms`
@@ -81,7 +81,7 @@ f(int)  # error
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-argument-forms)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L118)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L119)
 </details>
 
 ## `conflicting-declarations`
@@ -111,7 +111,7 @@ a = 1
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-declarations)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L144)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L145)
 </details>
 
 ## `conflicting-metaclass`
@@ -142,7 +142,7 @@ class C(A, B): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-metaclass)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L169)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L170)
 </details>
 
 ## `cyclic-class-definition`
@@ -173,7 +173,7 @@ class B(A): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20cyclic-class-definition)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L195)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L196)
 </details>
 
 ## `duplicate-base`
@@ -199,7 +199,7 @@ class B(A, A): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20duplicate-base)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L239)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L240)
 </details>
 
 ## `escape-character-in-forward-annotation`
@@ -336,7 +336,7 @@ TypeError: multiple bases have instance lay-out conflict
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20incompatible-slots)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L260)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L261)
 </details>
 
 ## `inconsistent-mro`
@@ -365,7 +365,7 @@ class C(A, B): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20inconsistent-mro)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L346)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L347)
 </details>
 
 ## `index-out-of-bounds`
@@ -390,7 +390,7 @@ t[3]  # IndexError: tuple index out of range
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20index-out-of-bounds)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L370)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L371)
 </details>
 
 ## `invalid-argument-type`
@@ -416,7 +416,7 @@ func("foo")  # error: [invalid-argument-type]
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-argument-type)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L390)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L391)
 </details>
 
 ## `invalid-assignment`
@@ -443,7 +443,7 @@ a: int = ''
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-assignment)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L430)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L431)
 </details>
 
 ## `invalid-attribute-access`
@@ -476,7 +476,7 @@ C.instance_var = 3  # error: Cannot assign to instance variable
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-attribute-access)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1336)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1337)
 </details>
 
 ## `invalid-base`
@@ -490,7 +490,7 @@ TODO #14889
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-base)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L452)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L453)
 </details>
 
 ## `invalid-context-manager`
@@ -516,7 +516,7 @@ with 1:
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-context-manager)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L461)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L462)
 </details>
 
 ## `invalid-declaration`
@@ -544,7 +544,7 @@ a: str
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-declaration)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L482)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L483)
 </details>
 
 ## `invalid-exception-caught`
@@ -585,7 +585,7 @@ except ZeroDivisionError:
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-exception-caught)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L505)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L506)
 </details>
 
 ## `invalid-generic-class`
@@ -616,7 +616,7 @@ class C[U](Generic[T]): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-generic-class)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L541)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L542)
 </details>
 
 ## `invalid-legacy-type-variable`
@@ -649,7 +649,7 @@ def f(t: TypeVar("U")): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-legacy-type-variable)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L567)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L568)
 </details>
 
 ## `invalid-metaclass`
@@ -681,7 +681,7 @@ class B(metaclass=f): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-metaclass)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L616)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L617)
 </details>
 
 ## `invalid-overload`
@@ -729,7 +729,7 @@ def foo(x: int) -> int: ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-overload)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L643)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L644)
 </details>
 
 ## `invalid-parameter-default`
@@ -754,7 +754,7 @@ def f(a: int = ''): ...
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-parameter-default)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L686)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L687)
 </details>
 
 ## `invalid-protocol`
@@ -787,7 +787,7 @@ TypeError: Protocols can only inherit from other protocols, got <class 'int'>
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-protocol)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L318)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L319)
 </details>
 
 ## `invalid-raise`
@@ -835,7 +835,7 @@ def g():
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-raise)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L706)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L707)
 </details>
 
 ## `invalid-return-type`
@@ -859,7 +859,7 @@ def func() -> int:
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-return-type)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L411)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L412)
 </details>
 
 ## `invalid-super-argument`
@@ -903,7 +903,7 @@ super(B, A)  # error: `A` does not satisfy `issubclass(A, B)`
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-super-argument)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L749)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L750)
 </details>
 
 ## `invalid-syntax-in-forward-annotation`
@@ -943,7 +943,7 @@ NewAlias = TypeAliasType(get_name(), int)        # error: TypeAliasType name mus
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-alias-type)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L595)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L596)
 </details>
 
 ## `invalid-type-checking-constant`
@@ -972,7 +972,7 @@ TYPE_CHECKING = ''
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-checking-constant)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L788)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L789)
 </details>
 
 ## `invalid-type-form`
@@ -1001,7 +1001,7 @@ b: Annotated[int]  # `Annotated` expects at least two arguments
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-form)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L812)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L813)
 </details>
 
 ## `invalid-type-variable-constraints`
@@ -1035,7 +1035,7 @@ T = TypeVar('T', bound=str)  # valid bound TypeVar
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-variable-constraints)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L836)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L837)
 </details>
 
 ## `missing-argument`
@@ -1059,7 +1059,7 @@ func()  # TypeError: func() missing 1 required positional argument: 'x'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20missing-argument)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L865)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L866)
 </details>
 
 ## `no-matching-overload`
@@ -1087,7 +1087,7 @@ func("string")  # error: [no-matching-overload]
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20no-matching-overload)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L884)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L885)
 </details>
 
 ## `non-subscriptable`
@@ -1110,7 +1110,7 @@ Subscripting an object that does not support it will raise a `TypeError` at runt
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20non-subscriptable)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L907)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L908)
 </details>
 
 ## `not-iterable`
@@ -1135,7 +1135,7 @@ for i in 34:  # TypeError: 'int' object is not iterable
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20not-iterable)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L925)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L926)
 </details>
 
 ## `parameter-already-assigned`
@@ -1161,7 +1161,7 @@ f(1, x=2)  # Error raised here
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20parameter-already-assigned)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L976)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L977)
 </details>
 
 ## `raw-string-type-annotation`
@@ -1220,7 +1220,7 @@ static_assert(int(2.0 * 3.0) == 6)  # error: does not have a statically known tr
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20static-assert-error)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1312)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1313)
 </details>
 
 ## `subclass-of-final-class`
@@ -1248,7 +1248,7 @@ class B(A): ...  # Error raised here
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20subclass-of-final-class)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1067)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1068)
 </details>
 
 ## `too-many-positional-arguments`
@@ -1274,7 +1274,7 @@ f("foo")  # Error raised here
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20too-many-positional-arguments)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1112)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1113)
 </details>
 
 ## `type-assertion-failure`
@@ -1301,7 +1301,7 @@ def _(x: int):
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20type-assertion-failure)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1090)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1091)
 </details>
 
 ## `unavailable-implicit-super-arguments`
@@ -1345,7 +1345,7 @@ class A:
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unavailable-implicit-super-arguments)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1133)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1134)
 </details>
 
 ## `unknown-argument`
@@ -1371,7 +1371,7 @@ f(x=1, y=2)  # Error raised here
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unknown-argument)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1190)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1191)
 </details>
 
 ## `unresolved-attribute`
@@ -1398,7 +1398,7 @@ A().foo  # AttributeError: 'A' object has no attribute 'foo'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-attribute)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1211)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1212)
 </details>
 
 ## `unresolved-import`
@@ -1422,7 +1422,7 @@ import foo  # ModuleNotFoundError: No module named 'foo'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-import)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1233)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1234)
 </details>
 
 ## `unresolved-reference`
@@ -1446,7 +1446,7 @@ print(x)  # NameError: name 'x' is not defined
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-reference)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1252)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1253)
 </details>
 
 ## `unsupported-bool-conversion`
@@ -1482,7 +1482,7 @@ b1 < b2 < b1  # exception raised here
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unsupported-bool-conversion)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L945)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L946)
 </details>
 
 ## `unsupported-operator`
@@ -1509,7 +1509,7 @@ A() + A()  # TypeError: unsupported operand type(s) for +: 'A' and 'A'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unsupported-operator)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1271)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1272)
 </details>
 
 ## `zero-stepsize-in-slice`
@@ -1533,7 +1533,7 @@ l[1:10:0]  # ValueError: slice step cannot be zero
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20zero-stepsize-in-slice)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1293)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1294)
 </details>
 
 ## `call-possibly-unbound-method`
@@ -1551,7 +1551,7 @@ Calling an unbound method will raise an `AttributeError` at runtime.
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20call-possibly-unbound-method)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L105)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L106)
 </details>
 
 ## `invalid-ignore-comment`
@@ -1607,7 +1607,7 @@ A.c  # AttributeError: type object 'A' has no attribute 'c'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unbound-attribute)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L997)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L998)
 </details>
 
 ## `possibly-unbound-import`
@@ -1638,7 +1638,7 @@ from module import a  # ImportError: cannot import name 'a' from 'module'
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unbound-import)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1019)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1020)
 </details>
 
 ## `redundant-cast`
@@ -1664,7 +1664,7 @@ cast(int, f())  # Redundant
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20redundant-cast)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1364)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1365)
 </details>
 
 ## `undefined-reveal`
@@ -1687,7 +1687,7 @@ reveal_type(1)  # NameError: name 'reveal_type' is not defined
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20undefined-reveal)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1172)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1173)
 </details>
 
 ## `unknown-rule`
@@ -1740,7 +1740,7 @@ Dividing by zero raises a `ZeroDivisionError` at runtime.
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20division-by-zero)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L221)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L222)
 </details>
 
 ## `possibly-unresolved-reference`
@@ -1767,7 +1767,7 @@ print(x)  # NameError: name 'x' is not defined
 
 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unresolved-reference)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1045)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1046)
 </details>
 
 ## `unused-ignore-comment`
diff --git a/crates/ty/tests/cli.rs b/crates/ty/tests/cli.rs
index f0e7e2c0ba..c0a510a143 100644
--- a/crates/ty/tests/cli.rs
+++ b/crates/ty/tests/cli.rs
@@ -241,6 +241,73 @@ fn config_override_python_platform() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[test]
+fn config_file_annotation_showing_where_python_version_set() -> anyhow::Result<()> {
+    let case = TestCase::with_files([
+        (
+            "pyproject.toml",
+            r#"
+            [tool.ty.environment]
+            python-version = "3.8"
+            "#,
+        ),
+        (
+            "test.py",
+            r#"
+            aiter
+            "#,
+        ),
+    ])?;
+
+    assert_cmd_snapshot!(case.command(), @r#"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-reference]: Name `aiter` used when not defined
+     --> test.py:2:1
+      |
+    2 | aiter
+      | ^^^^^
+      |
+    info: `aiter` was added as a builtin in Python 3.10
+    info: Python 3.8 was assumed when resolving types
+     --> pyproject.toml:3:18
+      |
+    2 | [tool.ty.environment]
+    3 | python-version = "3.8"
+      |                  ^^^^^ Python 3.8 assumed due to this configuration setting
+      |
+    info: rule `unresolved-reference` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    "#);
+
+    assert_cmd_snapshot!(case.command().arg("--python-version=3.9"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-reference]: Name `aiter` used when not defined
+     --> test.py:2:1
+      |
+    2 | aiter
+      | ^^^^^
+      |
+    info: `aiter` was added as a builtin in Python 3.10
+    info: Python 3.9 was assumed when resolving types because it was specified on the command line
+    info: rule `unresolved-reference` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    Ok(())
+}
+
 /// Paths specified on the CLI are relative to the current working directory and not the project root.
 ///
 /// We test this by adding an extra search path from the CLI to the libs directory when
diff --git a/crates/ty_ide/src/inlay_hints.rs b/crates/ty_ide/src/inlay_hints.rs
index 263e56cbc9..4539b54308 100644
--- a/crates/ty_ide/src/inlay_hints.rs
+++ b/crates/ty_ide/src/inlay_hints.rs
@@ -158,9 +158,9 @@ mod tests {
     use crate::db::tests::TestDb;
 
     use ruff_db::system::{DbWithWritableSystem, SystemPathBuf};
-    use ruff_python_ast::PythonVersion;
     use ty_python_semantic::{
-        Program, ProgramSettings, PythonPath, PythonPlatform, SearchPathSettings,
+        Program, ProgramSettings, PythonPath, PythonPlatform, PythonVersionWithSource,
+        SearchPathSettings,
     };
 
     pub(super) fn inlay_hint_test(source: &str) -> InlayHintTest {
@@ -191,7 +191,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::latest_ty(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
diff --git a/crates/ty_ide/src/lib.rs b/crates/ty_ide/src/lib.rs
index fe86113064..e403996788 100644
--- a/crates/ty_ide/src/lib.rs
+++ b/crates/ty_ide/src/lib.rs
@@ -207,10 +207,10 @@ mod tests {
     use ruff_db::diagnostic::{Diagnostic, DiagnosticFormat, DisplayDiagnosticConfig};
     use ruff_db::files::{File, system_path_to_file};
     use ruff_db::system::{DbWithWritableSystem, SystemPath, SystemPathBuf};
-    use ruff_python_ast::PythonVersion;
     use ruff_text_size::TextSize;
     use ty_python_semantic::{
-        Program, ProgramSettings, PythonPath, PythonPlatform, SearchPathSettings,
+        Program, ProgramSettings, PythonPath, PythonPlatform, PythonVersionWithSource,
+        SearchPathSettings,
     };
 
     pub(super) fn cursor_test(source: &str) -> CursorTest {
@@ -230,7 +230,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::latest_ty(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
diff --git a/crates/ty_project/src/lib.rs b/crates/ty_project/src/lib.rs
index ae395ecfc0..bbe84382af 100644
--- a/crates/ty_project/src/lib.rs
+++ b/crates/ty_project/src/lib.rs
@@ -663,10 +663,11 @@ mod tests {
     use ruff_db::source::source_text;
     use ruff_db::system::{DbWithTestSystem, DbWithWritableSystem as _, SystemPath, SystemPathBuf};
     use ruff_db::testing::assert_function_query_was_not_run;
-    use ruff_python_ast::PythonVersion;
     use ruff_python_ast::name::Name;
     use ty_python_semantic::types::check_types;
-    use ty_python_semantic::{Program, ProgramSettings, PythonPlatform, SearchPathSettings};
+    use ty_python_semantic::{
+        Program, ProgramSettings, PythonPlatform, PythonVersionWithSource, SearchPathSettings,
+    };
 
     #[test]
     fn check_file_skips_type_checking_when_file_cant_be_read() -> ruff_db::system::Result<()> {
@@ -677,7 +678,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings::new(vec![SystemPathBuf::from(".")]),
             },
diff --git a/crates/ty_project/src/metadata/options.rs b/crates/ty_project/src/metadata/options.rs
index f8c83ad5b4..00bab6dd95 100644
--- a/crates/ty_project/src/metadata/options.rs
+++ b/crates/ty_project/src/metadata/options.rs
@@ -10,7 +10,10 @@ use serde::{Deserialize, Serialize};
 use std::fmt::Debug;
 use thiserror::Error;
 use ty_python_semantic::lint::{GetLintError, Level, LintSource, RuleSelection};
-use ty_python_semantic::{ProgramSettings, PythonPath, PythonPlatform, SearchPathSettings};
+use ty_python_semantic::{
+    ProgramSettings, PythonPath, PythonPlatform, PythonVersionSource, PythonVersionWithSource,
+    SearchPathSettings,
+};
 
 use super::settings::{Settings, TerminalSettings};
 
@@ -93,8 +96,17 @@ impl Options {
         let python_version = self
             .environment
             .as_ref()
-            .and_then(|env| env.python_version.as_deref().copied())
-            .unwrap_or(PythonVersion::latest_ty());
+            .and_then(|env| env.python_version.as_ref())
+            .map(|ranged_version| PythonVersionWithSource {
+                version: **ranged_version,
+                source: match ranged_version.source() {
+                    ValueSource::Cli => PythonVersionSource::Cli,
+                    ValueSource::File(path) => {
+                        PythonVersionSource::File(path.clone(), ranged_version.range())
+                    }
+                },
+            })
+            .unwrap_or_default();
         let python_platform = self
             .environment
             .as_ref()
diff --git a/crates/ty_python_semantic/resources/mdtest/snapshots/annotations.md_-_Assignment_with_anno…_-_PEP-604_in_non-type-…_-_Earlier_versions_(f2859c9800f37c7).snap b/crates/ty_python_semantic/resources/mdtest/snapshots/annotations.md_-_Assignment_with_anno…_-_PEP-604_in_non-type-…_-_Earlier_versions_(f2859c9800f37c7).snap
index c66ac9c49c..3cfe98c8f7 100644
--- a/crates/ty_python_semantic/resources/mdtest/snapshots/annotations.md_-_Assignment_with_anno…_-_PEP-604_in_non-type-…_-_Earlier_versions_(f2859c9800f37c7).snap
+++ b/crates/ty_python_semantic/resources/mdtest/snapshots/annotations.md_-_Assignment_with_anno…_-_PEP-604_in_non-type-…_-_Earlier_versions_(f2859c9800f37c7).snap
@@ -27,8 +27,7 @@ error[unsupported-operator]: Operator `|` is unsupported between objects of type
   |            ^^^^^^^^^
   |
 info: Note that `X | Y` PEP 604 union syntax is only available in Python 3.10 and later
-info: The inferred target version of your project is Python 3.9
-info: If using a pyproject.toml file, consider adjusting the `project.requires-python` or `tool.ty.environment.python-version` field
+info: Python 3.9 was assumed when resolving types because it was specified on the command line
 info: rule `unsupported-operator` is enabled by default
 
 ```
diff --git a/crates/ty_python_semantic/resources/mdtest/snapshots/unresolved_reference…_-_Diagnostics_for_unre…_-_New_builtin_used_on_…_(51edda0b1aebc2bf).snap b/crates/ty_python_semantic/resources/mdtest/snapshots/unresolved_reference…_-_Diagnostics_for_unre…_-_New_builtin_used_on_…_(51edda0b1aebc2bf).snap
index 4669867bfa..fd14c51a15 100644
--- a/crates/ty_python_semantic/resources/mdtest/snapshots/unresolved_reference…_-_Diagnostics_for_unre…_-_New_builtin_used_on_…_(51edda0b1aebc2bf).snap
+++ b/crates/ty_python_semantic/resources/mdtest/snapshots/unresolved_reference…_-_Diagnostics_for_unre…_-_New_builtin_used_on_…_(51edda0b1aebc2bf).snap
@@ -25,8 +25,7 @@ error[unresolved-reference]: Name `aiter` used when not defined
   | ^^^^^
   |
 info: `aiter` was added as a builtin in Python 3.10
-info: The inferred target version of your project is Python 3.9
-info: If using a pyproject.toml file, consider adjusting the `project.requires-python` or `tool.ty.environment.python-version` field
+info: Python 3.9 was assumed when resolving types because it was specified on the command line
 info: rule `unresolved-reference` is enabled by default
 
 ```
diff --git a/crates/ty_python_semantic/src/db.rs b/crates/ty_python_semantic/src/db.rs
index 451cde45e7..99e560905b 100644
--- a/crates/ty_python_semantic/src/db.rs
+++ b/crates/ty_python_semantic/src/db.rs
@@ -17,7 +17,10 @@ pub(crate) mod tests {
     use std::sync::{Arc, Mutex};
 
     use crate::program::{Program, SearchPathSettings};
-    use crate::{ProgramSettings, PythonPlatform, default_lint_registry};
+    use crate::{
+        ProgramSettings, PythonPlatform, PythonVersionSource, PythonVersionWithSource,
+        default_lint_registry,
+    };
 
     use super::Db;
     use crate::lint::{LintRegistry, RuleSelection};
@@ -179,7 +182,10 @@ pub(crate) mod tests {
             Program::from_settings(
                 &db,
                 ProgramSettings {
-                    python_version: self.python_version,
+                    python_version: PythonVersionWithSource {
+                        version: self.python_version,
+                        source: PythonVersionSource::default(),
+                    },
                     python_platform: self.python_platform,
                     search_paths: SearchPathSettings::new(vec![src_root]),
                 },
diff --git a/crates/ty_python_semantic/src/lib.rs b/crates/ty_python_semantic/src/lib.rs
index 640b7cefb8..8857a48341 100644
--- a/crates/ty_python_semantic/src/lib.rs
+++ b/crates/ty_python_semantic/src/lib.rs
@@ -7,7 +7,10 @@ use crate::suppression::{INVALID_IGNORE_COMMENT, UNKNOWN_RULE, UNUSED_IGNORE_COM
 pub use db::Db;
 pub use module_name::ModuleName;
 pub use module_resolver::{KnownModule, Module, resolve_module, system_module_search_paths};
-pub use program::{Program, ProgramSettings, PythonPath, SearchPathSettings};
+pub use program::{
+    Program, ProgramSettings, PythonPath, PythonVersionSource, PythonVersionWithSource,
+    SearchPathSettings,
+};
 pub use python_platform::PythonPlatform;
 pub use semantic_model::{HasType, SemanticModel};
 pub use site_packages::SysPrefixPathOrigin;
diff --git a/crates/ty_python_semantic/src/module_resolver/resolver.rs b/crates/ty_python_semantic/src/module_resolver/resolver.rs
index d39edc57ca..49bf534e77 100644
--- a/crates/ty_python_semantic/src/module_resolver/resolver.rs
+++ b/crates/ty_python_semantic/src/module_resolver/resolver.rs
@@ -978,7 +978,7 @@ mod tests {
     use crate::module_name::ModuleName;
     use crate::module_resolver::module::ModuleKind;
     use crate::module_resolver::testing::{FileSpec, MockedTypeshed, TestCase, TestCaseBuilder};
-    use crate::{ProgramSettings, PythonPlatform};
+    use crate::{ProgramSettings, PythonPlatform, PythonVersionWithSource};
 
     use super::*;
 
@@ -1435,7 +1435,9 @@ mod tests {
     fn symlink() -> anyhow::Result<()> {
         use anyhow::Context;
 
-        use crate::{PythonPlatform, program::Program};
+        use crate::{
+            PythonPlatform, PythonVersionSource, PythonVersionWithSource, program::Program,
+        };
         use ruff_db::system::{OsSystem, SystemPath};
 
         use crate::db::tests::TestDb;
@@ -1468,7 +1470,10 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::PY38,
+                python_version: PythonVersionWithSource {
+                    version: PythonVersion::PY38,
+                    source: PythonVersionSource::default(),
+                },
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -1984,7 +1989,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -2063,7 +2068,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -2106,7 +2111,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: PythonVersionWithSource::default(),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
diff --git a/crates/ty_python_semantic/src/module_resolver/testing.rs b/crates/ty_python_semantic/src/module_resolver/testing.rs
index 75e0dfdc23..5f1e9c4b6e 100644
--- a/crates/ty_python_semantic/src/module_resolver/testing.rs
+++ b/crates/ty_python_semantic/src/module_resolver/testing.rs
@@ -6,7 +6,9 @@ use ruff_python_ast::PythonVersion;
 
 use crate::db::tests::TestDb;
 use crate::program::{Program, SearchPathSettings};
-use crate::{ProgramSettings, PythonPath, PythonPlatform};
+use crate::{
+    ProgramSettings, PythonPath, PythonPlatform, PythonVersionSource, PythonVersionWithSource,
+};
 
 /// A test case for the module resolver.
 ///
@@ -235,7 +237,10 @@ impl TestCaseBuilder<MockedTypeshed> {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: PythonVersionWithSource {
+                    version: python_version,
+                    source: PythonVersionSource::default(),
+                },
                 python_platform,
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -293,7 +298,10 @@ impl TestCaseBuilder<VendoredTypeshed> {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: PythonVersionWithSource {
+                    version: python_version,
+                    source: PythonVersionSource::default(),
+                },
                 python_platform,
                 search_paths: SearchPathSettings {
                     python_path: PythonPath::KnownSitePackages(vec![site_packages.clone()]),
diff --git a/crates/ty_python_semantic/src/program.rs b/crates/ty_python_semantic/src/program.rs
index f114a3e19a..74e662e355 100644
--- a/crates/ty_python_semantic/src/program.rs
+++ b/crates/ty_python_semantic/src/program.rs
@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use crate::Db;
 use crate::module_resolver::SearchPaths;
 use crate::python_platform::PythonPlatform;
@@ -6,12 +8,14 @@ use crate::site_packages::SysPrefixPathOrigin;
 use anyhow::Context;
 use ruff_db::system::{SystemPath, SystemPathBuf};
 use ruff_python_ast::PythonVersion;
+use ruff_text_size::TextRange;
 use salsa::Durability;
 use salsa::Setter;
 
 #[salsa::input(singleton)]
 pub struct Program {
-    pub python_version: PythonVersion,
+    #[returns(ref)]
+    pub python_version_with_source: PythonVersionWithSource,
 
     #[returns(ref)]
     pub python_platform: PythonPlatform,
@@ -23,23 +27,30 @@ pub struct Program {
 impl Program {
     pub fn from_settings(db: &dyn Db, settings: ProgramSettings) -> anyhow::Result<Self> {
         let ProgramSettings {
-            python_version,
+            python_version: python_version_with_source,
             python_platform,
             search_paths,
         } = settings;
 
-        tracing::info!("Python version: Python {python_version}, platform: {python_platform}");
+        tracing::info!(
+            "Python version: Python {python_version}, platform: {python_platform}",
+            python_version = python_version_with_source.version
+        );
 
         let search_paths = SearchPaths::from_settings(db, &search_paths)
             .with_context(|| "Invalid search path settings")?;
 
         Ok(
-            Program::builder(python_version, python_platform, search_paths)
+            Program::builder(python_version_with_source, python_platform, search_paths)
                 .durability(Durability::HIGH)
                 .new(db),
         )
     }
 
+    pub fn python_version(self, db: &dyn Db) -> PythonVersion {
+        self.python_version_with_source(db).version
+    }
+
     pub fn update_from_settings(
         self,
         db: &mut dyn Db,
@@ -56,9 +67,9 @@ impl Program {
             self.set_python_platform(db).to(python_platform);
         }
 
-        if python_version != self.python_version(db) {
-            tracing::debug!("Updating python version: Python {python_version}");
-            self.set_python_version(db).to(python_version);
+        if &python_version != self.python_version_with_source(db) {
+            tracing::debug!("Updating python version: `{python_version:?}`");
+            self.set_python_version_with_source(db).to(python_version);
         }
 
         self.update_search_paths(db, &search_paths)?;
@@ -87,13 +98,41 @@ impl Program {
 }
 
 #[derive(Clone, Debug, Eq, PartialEq)]
-#[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct ProgramSettings {
-    pub python_version: PythonVersion,
+    pub python_version: PythonVersionWithSource,
     pub python_platform: PythonPlatform,
     pub search_paths: SearchPathSettings,
 }
 
+#[derive(Clone, Debug, Eq, PartialEq, Default)]
+pub enum PythonVersionSource {
+    /// Value loaded from a project's configuration file.
+    File(Arc<SystemPathBuf>, Option<TextRange>),
+
+    /// The value comes from a CLI argument, while it's left open if specified using a short argument,
+    /// long argument (`--extra-paths`) or `--config key=value`.
+    Cli,
+
+    /// We fell back to a default value because the value was not specified via the CLI or a config file.
+    #[default]
+    Default,
+}
+
+#[derive(Eq, PartialEq, Debug, Clone)]
+pub struct PythonVersionWithSource {
+    pub version: PythonVersion,
+    pub source: PythonVersionSource,
+}
+
+impl Default for PythonVersionWithSource {
+    fn default() -> Self {
+        Self {
+            version: PythonVersion::latest_ty(),
+            source: PythonVersionSource::Default,
+        }
+    }
+}
+
 /// Configures the search paths for module resolution.
 #[derive(Eq, PartialEq, Debug, Clone)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
diff --git a/crates/ty_python_semantic/src/types/class.rs b/crates/ty_python_semantic/src/types/class.rs
index 22692f5696..da9ca6af97 100644
--- a/crates/ty_python_semantic/src/types/class.rs
+++ b/crates/ty_python_semantic/src/types/class.rs
@@ -2887,6 +2887,7 @@ mod tests {
     use super::*;
     use crate::db::tests::setup_db;
     use crate::module_resolver::resolve_module;
+    use crate::{PythonVersionSource, PythonVersionWithSource};
     use salsa::Setter;
     use strum::IntoEnumIterator;
 
@@ -2910,8 +2911,11 @@ mod tests {
         let mut db = setup_db();
 
         Program::get(&db)
-            .set_python_version(&mut db)
-            .to(PythonVersion::latest_ty());
+            .set_python_version_with_source(&mut db)
+            .to(PythonVersionWithSource {
+                version: PythonVersion::latest_ty(),
+                source: PythonVersionSource::default(),
+            });
 
         for class in KnownClass::iter() {
             assert_ne!(
@@ -2935,8 +2939,11 @@ mod tests {
             };
 
             Program::get(&db)
-                .set_python_version(&mut db)
-                .to(version_added);
+                .set_python_version_with_source(&mut db)
+                .to(PythonVersionWithSource {
+                    version: version_added,
+                    source: PythonVersionSource::default(),
+                });
 
             assert_ne!(
                 class.to_instance(&db),
diff --git a/crates/ty_python_semantic/src/types/diagnostic.rs b/crates/ty_python_semantic/src/types/diagnostic.rs
index a9e6c6075c..e7ad9c76d5 100644
--- a/crates/ty_python_semantic/src/types/diagnostic.rs
+++ b/crates/ty_python_semantic/src/types/diagnostic.rs
@@ -11,8 +11,9 @@ use crate::types::string_annotation::{
     RAW_STRING_TYPE_ANNOTATION,
 };
 use crate::types::{KnownFunction, KnownInstanceType, Type, protocol_class::ProtocolClassLiteral};
-use crate::{Program, declare_lint};
-use ruff_db::diagnostic::{Annotation, Diagnostic, Severity, SubDiagnostic};
+use crate::{Program, PythonVersionWithSource, declare_lint};
+use ruff_db::diagnostic::{Annotation, Diagnostic, Severity, Span, SubDiagnostic};
+use ruff_db::files::system_path_to_file;
 use ruff_python_ast::{self as ast, AnyNodeRef};
 use ruff_python_stdlib::builtins::version_builtin_was_added;
 use ruff_text_size::{Ranged, TextRange};
@@ -1670,15 +1671,41 @@ pub(super) fn report_possibly_unbound_attribute(
 }
 
 pub(super) fn add_inferred_python_version_hint(db: &dyn Db, mut diagnostic: LintDiagnosticGuard) {
-    diagnostic.info(format_args!(
-        "The inferred target version of your project is Python {}",
-        Program::get(db).python_version(db)
-    ));
+    let program = Program::get(db);
+    let PythonVersionWithSource { version, source } = program.python_version_with_source(db);
 
-    diagnostic.info(
-            "If using a pyproject.toml file, \
-            consider adjusting the `project.requires-python` or `tool.ty.environment.python-version` field"
-        );
+    match source {
+        crate::PythonVersionSource::Cli => {
+            diagnostic.info(format_args!(
+                "Python {version} was assumed when resolving types because it was specified on the command line",
+            ));
+        }
+        crate::PythonVersionSource::File(path, range) => {
+            if let Ok(file) = system_path_to_file(db.upcast(), &**path) {
+                let mut sub_diagnostic = SubDiagnostic::new(
+                    Severity::Info,
+                    format_args!("Python {version} was assumed when resolving types"),
+                );
+                sub_diagnostic.annotate(
+                    Annotation::primary(Span::from(file).with_optional_range(*range)).message(
+                        format_args!("Python {version} assumed due to this configuration setting"),
+                    ),
+                );
+                diagnostic.sub(sub_diagnostic);
+            } else {
+                diagnostic.info(format_args!(
+                    "Python {version} was assumed when resolving types because of your configuration file(s)",
+                ));
+            }
+        }
+        crate::PythonVersionSource::Default => {
+            diagnostic.info(format_args!(
+                "Python {version} was assumed when resolving types \
+                because it is the newest Python version supported by ty, \
+                and neither a command-line argument nor a configuration setting was provided",
+            ));
+        }
+    }
 }
 
 pub(super) fn report_unresolved_reference(context: &InferContext, expr_name_node: &ast::ExprName) {
@@ -1692,9 +1719,6 @@ pub(super) fn report_unresolved_reference(context: &InferContext, expr_name_node
         diagnostic.info(format_args!(
             "`{id}` was added as a builtin in Python 3.{version_added_to_builtins}"
         ));
-
-        // TODO: can we tell the user *why* we're inferring this target version?
-        // CLI flag? pyproject.toml? Python environment?
         add_inferred_python_version_hint(context.db(), diagnostic);
     }
 }
diff --git a/crates/ty_test/src/assertion.rs b/crates/ty_test/src/assertion.rs
index f342a16013..2e9bfd338c 100644
--- a/crates/ty_test/src/assertion.rs
+++ b/crates/ty_test/src/assertion.rs
@@ -493,16 +493,17 @@ mod tests {
     use super::*;
     use ruff_db::files::system_path_to_file;
     use ruff_db::system::DbWithWritableSystem as _;
-    use ruff_python_ast::PythonVersion;
     use ruff_python_trivia::textwrap::dedent;
     use ruff_source_file::OneIndexed;
-    use ty_python_semantic::{Program, ProgramSettings, PythonPlatform, SearchPathSettings};
+    use ty_python_semantic::{
+        Program, ProgramSettings, PythonPlatform, PythonVersionWithSource, SearchPathSettings,
+    };
 
     fn get_assertions(source: &str) -> InlineFileAssertions {
         let mut db = Db::setup();
 
         let settings = ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: PythonVersionWithSource::default(),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(Vec::new()),
         };
diff --git a/crates/ty_test/src/lib.rs b/crates/ty_test/src/lib.rs
index 7773875377..8375bf2046 100644
--- a/crates/ty_test/src/lib.rs
+++ b/crates/ty_test/src/lib.rs
@@ -19,7 +19,8 @@ use std::backtrace::BacktraceStatus;
 use std::fmt::Write;
 use ty_python_semantic::types::check_types;
 use ty_python_semantic::{
-    Program, ProgramSettings, PythonPath, PythonPlatform, SearchPathSettings, SysPrefixPathOrigin,
+    Program, ProgramSettings, PythonPath, PythonPlatform, PythonVersionSource,
+    PythonVersionWithSource, SearchPathSettings, SysPrefixPathOrigin,
 };
 
 mod assertion;
@@ -260,7 +261,10 @@ fn run_test(
     let configuration = test.configuration();
 
     let settings = ProgramSettings {
-        python_version,
+        python_version: PythonVersionWithSource {
+            version: python_version,
+            source: PythonVersionSource::Cli,
+        },
         python_platform: configuration
             .python_platform()
             .unwrap_or(PythonPlatform::Identifier("linux".to_string())),
diff --git a/crates/ty_test/src/matcher.rs b/crates/ty_test/src/matcher.rs
index e8094a6ce7..ff90010f78 100644
--- a/crates/ty_test/src/matcher.rs
+++ b/crates/ty_test/src/matcher.rs
@@ -341,11 +341,12 @@ mod tests {
     use ruff_db::diagnostic::{Annotation, Diagnostic, DiagnosticId, Severity, Span};
     use ruff_db::files::{File, system_path_to_file};
     use ruff_db::system::DbWithWritableSystem as _;
-    use ruff_python_ast::PythonVersion;
     use ruff_python_trivia::textwrap::dedent;
     use ruff_source_file::OneIndexed;
     use ruff_text_size::TextRange;
-    use ty_python_semantic::{Program, ProgramSettings, PythonPlatform, SearchPathSettings};
+    use ty_python_semantic::{
+        Program, ProgramSettings, PythonPlatform, PythonVersionWithSource, SearchPathSettings,
+    };
 
     struct ExpectedDiagnostic {
         id: DiagnosticId,
@@ -384,7 +385,7 @@ mod tests {
         let mut db = crate::db::Db::setup();
 
         let settings = ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: PythonVersionWithSource::default(),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(Vec::new()),
         };
diff --git a/fuzz/fuzz_targets/ty_check_invalid_syntax.rs b/fuzz/fuzz_targets/ty_check_invalid_syntax.rs
index 47b4dc5bef..dbc814644c 100644
--- a/fuzz/fuzz_targets/ty_check_invalid_syntax.rs
+++ b/fuzz/fuzz_targets/ty_check_invalid_syntax.rs
@@ -5,21 +5,21 @@
 
 use std::sync::{Arc, Mutex, OnceLock};
 
-use libfuzzer_sys::{fuzz_target, Corpus};
+use libfuzzer_sys::{Corpus, fuzz_target};
 
-use ruff_db::files::{system_path_to_file, File, Files};
+use ruff_db::files::{File, Files, system_path_to_file};
 use ruff_db::system::{
     DbWithTestSystem, DbWithWritableSystem as _, System, SystemPathBuf, TestSystem,
 };
 use ruff_db::vendored::VendoredFileSystem;
 use ruff_db::{Db as SourceDb, Upcast};
 use ruff_python_ast::PythonVersion;
-use ruff_python_parser::{parse_unchecked, Mode, ParseOptions};
+use ruff_python_parser::{Mode, ParseOptions, parse_unchecked};
 use ty_python_semantic::lint::LintRegistry;
 use ty_python_semantic::types::check_types;
 use ty_python_semantic::{
-    default_lint_registry, lint::RuleSelection, Db as SemanticDb, Program, ProgramSettings,
-    PythonPlatform, SearchPathSettings,
+    Db as SemanticDb, Program, ProgramSettings, PythonPlatform, SearchPathSettings,
+    default_lint_registry, lint::RuleSelection, PythonVersionWithSource,
 };
 
 /// Database that can be used for testing.
@@ -118,7 +118,7 @@ fn setup_db() -> TestDb {
     Program::from_settings(
         &db,
         ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: PythonVersionWithSource::default(),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(vec![src_root]),
         },