diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a5bf16cca..e19d6d469 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -28,3 +28,9 @@ See the [dedicated section][section] on the Swift project website.
 After you opened your PR, a maintainer will review it and test your changes in CI (*Continuous Integration*) by adding a `@swift-ci Please test` comment on the pull request. Once your PR is approved and CI has passed, the maintainer will merge your pull request.
 
 Only contributors with [commit access](https://www.swift.org/contributing/#commit-access) are able to approve pull requests and trigger CI.
+
+## API Design
+
+### Public `enum`s
+
+Enums should generally be marked as `@frozen` or `@nonexhaustive` to allow consistent behavior when switching over them in library-evolution and non-library-evolution builds. The default should be `@frozen` unless we expect to extend the enum without adopting a new LSP or BSP version, eg. because the type is part of an LSP extension. We do not need to anticipate the LSP/BSP specification changing since we plan to release a new major version of swift-tools-protocols when it gets updated to a new LSP or BSP specification version. Custom `CodingKey` enums should always be marked as `@nonexhaustive` because we want to be able to add new members to structs.
diff --git a/Sources/BuildServerProtocol/Messages/BuildTargetSourcesRequest.swift b/Sources/BuildServerProtocol/Messages/BuildTargetSourcesRequest.swift
index 4342f4719..d8f256efd 100644
--- a/Sources/BuildServerProtocol/Messages/BuildTargetSourcesRequest.swift
+++ b/Sources/BuildServerProtocol/Messages/BuildTargetSourcesRequest.swift
@@ -94,7 +94,7 @@ public struct SourceItem: Codable, Hashable, Sendable {
   }
 }
 
-public enum SourceItemKind: Int, Codable, Hashable, Sendable {
+@frozen public enum SourceItemKind: Int, Codable, Hashable, Sendable {
   /// The source item references a normal file.
   case file = 1
 
@@ -120,7 +120,7 @@ public struct SourceItemDataKind: RawRepresentable, Codable, Hashable, Sendable
 
 /// **(BSP Extension)**
 
-public enum SourceKitSourceItemKind: String, Codable {
+/*@nonexhaustive*/ public enum SourceKitSourceItemKind: String, Codable {
   /// A source file that belongs to the target
   case source = "source"
 
diff --git a/Sources/BuildServerProtocol/Messages/OnBuildLogMessageNotification.swift b/Sources/BuildServerProtocol/Messages/OnBuildLogMessageNotification.swift
index a3008aae3..94264f4fa 100644
--- a/Sources/BuildServerProtocol/Messages/OnBuildLogMessageNotification.swift
+++ b/Sources/BuildServerProtocol/Messages/OnBuildLogMessageNotification.swift
@@ -50,7 +50,7 @@ public struct OnBuildLogMessageNotification: BSPNotification {
   }
 }
 
-public enum StructuredLogKind: Codable, Hashable, Sendable {
+@frozen public enum StructuredLogKind: Codable, Hashable, Sendable {
   case begin(StructuredLogBegin)
   case report(StructuredLogReport)
   case end(StructuredLogEnd)
diff --git a/Sources/BuildServerProtocol/Messages/OnBuildTargetDidChangeNotification.swift b/Sources/BuildServerProtocol/Messages/OnBuildTargetDidChangeNotification.swift
index 8dc6b3b9a..7737a6dc7 100644
--- a/Sources/BuildServerProtocol/Messages/OnBuildTargetDidChangeNotification.swift
+++ b/Sources/BuildServerProtocol/Messages/OnBuildTargetDidChangeNotification.swift
@@ -53,7 +53,7 @@ public struct BuildTargetEvent: Codable, Hashable, Sendable {
   }
 }
 
-public enum BuildTargetEventKind: Int, Codable, Hashable, Sendable {
+@frozen public enum BuildTargetEventKind: Int, Codable, Hashable, Sendable {
   /// The build target is new.
   case created = 1
 
diff --git a/Sources/BuildServerProtocol/Messages/RegisterForChangeNotifications.swift b/Sources/BuildServerProtocol/Messages/RegisterForChangeNotifications.swift
index b2d719f28..f8c4d9cfb 100644
--- a/Sources/BuildServerProtocol/Messages/RegisterForChangeNotifications.swift
+++ b/Sources/BuildServerProtocol/Messages/RegisterForChangeNotifications.swift
@@ -36,7 +36,7 @@ public struct RegisterForChanges: BSPRequest {
   }
 }
 
-public enum RegisterAction: String, Hashable, Codable, Sendable {
+@frozen public enum RegisterAction: String, Hashable, Codable, Sendable {
   case register = "register"
   case unregister = "unregister"
 }
diff --git a/Sources/BuildServerProtocol/Messages/TaskFinishNotification.swift b/Sources/BuildServerProtocol/Messages/TaskFinishNotification.swift
index 9504fd137..2ea6c4a91 100644
--- a/Sources/BuildServerProtocol/Messages/TaskFinishNotification.swift
+++ b/Sources/BuildServerProtocol/Messages/TaskFinishNotification.swift
@@ -165,7 +165,7 @@ public struct TestFinishData: Codable, Hashable, Sendable {
 
 }
 
-public enum TestStatus: Int, Codable, Hashable, Sendable {
+@frozen public enum TestStatus: Int, Codable, Hashable, Sendable {
   /// The test passed successfully.
   case passed = 1
 
diff --git a/Sources/BuildServerProtocol/SupportTypes/MessageType.swift b/Sources/BuildServerProtocol/SupportTypes/MessageType.swift
index 3e18cf2fa..01feca83b 100644
--- a/Sources/BuildServerProtocol/SupportTypes/MessageType.swift
+++ b/Sources/BuildServerProtocol/SupportTypes/MessageType.swift
@@ -12,7 +12,7 @@
 
 import LanguageServerProtocol
 
-public enum MessageType: Int, Sendable, Codable {
+@frozen public enum MessageType: Int, Sendable, Codable {
   /// An error message.
   case error = 1
 
diff --git a/Sources/BuildServerProtocol/SupportTypes/StatusCode.swift b/Sources/BuildServerProtocol/SupportTypes/StatusCode.swift
index 109a0be47..b59bee88c 100644
--- a/Sources/BuildServerProtocol/SupportTypes/StatusCode.swift
+++ b/Sources/BuildServerProtocol/SupportTypes/StatusCode.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum StatusCode: Int, Codable, Hashable, Sendable {
+@frozen public enum StatusCode: Int, Codable, Hashable, Sendable {
   /// Execution was successful.
   case ok = 1
 
diff --git a/Sources/LanguageServerProtocol/Notifications/LogMessageNotification.swift b/Sources/LanguageServerProtocol/Notifications/LogMessageNotification.swift
index 32ba39e64..e47a5501a 100644
--- a/Sources/LanguageServerProtocol/Notifications/LogMessageNotification.swift
+++ b/Sources/LanguageServerProtocol/Notifications/LogMessageNotification.swift
@@ -44,7 +44,7 @@ public struct LogMessageNotification: LSPNotification, Hashable {
   }
 }
 
-public enum StructuredLogKind: Codable, Hashable, Sendable {
+@frozen public enum StructuredLogKind: Codable, Hashable, Sendable {
   case begin(StructuredLogBegin)
   case report(StructuredLogReport)
   case end(StructuredLogEnd)
diff --git a/Sources/LanguageServerProtocol/Notifications/WorkDoneProgress.swift b/Sources/LanguageServerProtocol/Notifications/WorkDoneProgress.swift
index c8ae9c297..7102cefb3 100644
--- a/Sources/LanguageServerProtocol/Notifications/WorkDoneProgress.swift
+++ b/Sources/LanguageServerProtocol/Notifications/WorkDoneProgress.swift
@@ -25,7 +25,7 @@ public struct WorkDoneProgress: LSPNotification, Hashable {
   }
 }
 
-public enum WorkDoneProgressKind: Codable, Hashable, Sendable {
+@frozen public enum WorkDoneProgressKind: Codable, Hashable, Sendable {
   case begin(WorkDoneProgressBegin)
   case report(WorkDoneProgressReport)
   case end(WorkDoneProgressEnd)
diff --git a/Sources/LanguageServerProtocol/RequestID.swift b/Sources/LanguageServerProtocol/RequestID.swift
index ddf45cdbe..46c782d27 100644
--- a/Sources/LanguageServerProtocol/RequestID.swift
+++ b/Sources/LanguageServerProtocol/RequestID.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum RequestID: Hashable, Sendable {
+@frozen public enum RequestID: Hashable, Sendable {
   case string(String)
   case number(Int)
 }
diff --git a/Sources/LanguageServerProtocol/Requests/CodeActionRequest.swift b/Sources/LanguageServerProtocol/Requests/CodeActionRequest.swift
index 09db58055..12e376357 100644
--- a/Sources/LanguageServerProtocol/Requests/CodeActionRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/CodeActionRequest.swift
@@ -50,7 +50,7 @@ public struct CodeActionRequest: TextDocumentRequest, Hashable {
 /// Wrapper type for the response of a CodeAction request.
 /// If the client supports CodeAction literals, the encoded type will be the CodeAction array itself.
 /// Otherwise, the encoded value will be an array of CodeActions' inner Command structs.
-public enum CodeActionRequestResponse: ResponseType, Codable, Equatable {
+@frozen public enum CodeActionRequestResponse: ResponseType, Codable, Equatable {
   case codeActions([CodeAction])
   case commands([Command])
 
diff --git a/Sources/LanguageServerProtocol/Requests/CompletionRequest.swift b/Sources/LanguageServerProtocol/Requests/CompletionRequest.swift
index 3d995a728..3c2b83408 100644
--- a/Sources/LanguageServerProtocol/Requests/CompletionRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/CompletionRequest.swift
@@ -93,7 +93,7 @@ public struct CompletionList: ResponseType, Hashable {
     }
   }
 
-  public enum ItemDefaultsEditRange: Codable, Hashable, Sendable {
+  @frozen public enum ItemDefaultsEditRange: Codable, Hashable, Sendable {
     case range(Range<Position>)
     case insertReplaceRanges(InsertReplaceRanges)
 
diff --git a/Sources/LanguageServerProtocol/Requests/DocumentDiagnosticsRequest.swift b/Sources/LanguageServerProtocol/Requests/DocumentDiagnosticsRequest.swift
index 63ed427af..45e57128f 100644
--- a/Sources/LanguageServerProtocol/Requests/DocumentDiagnosticsRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/DocumentDiagnosticsRequest.swift
@@ -35,7 +35,7 @@ public struct DocumentDiagnosticsRequest: TextDocumentRequest {
 /// requested document or a unchanged report indicating that nothing
 /// has changed in terms of diagnostics in comparison to the last
 /// pull request.
-public enum DocumentDiagnosticReport: ResponseType, Codable, Hashable {
+@frozen public enum DocumentDiagnosticReport: ResponseType, Codable, Hashable {
   case full(RelatedFullDocumentDiagnosticReport)
   case unchanged(RelatedUnchangedDocumentDiagnosticReport)
 
diff --git a/Sources/LanguageServerProtocol/Requests/DocumentHighlightRequest.swift b/Sources/LanguageServerProtocol/Requests/DocumentHighlightRequest.swift
index 05277b968..9dc1633e2 100644
--- a/Sources/LanguageServerProtocol/Requests/DocumentHighlightRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/DocumentHighlightRequest.swift
@@ -41,7 +41,7 @@ public struct DocumentHighlightRequest: TextDocumentRequest, Hashable {
 }
 
 /// The kind of document highlight - read, write, or text (fuzzy).
-public enum DocumentHighlightKind: Int, Codable, Hashable, Sendable {
+@frozen public enum DocumentHighlightKind: Int, Codable, Hashable, Sendable {
 
   /// Textual match.
   case text = 1
diff --git a/Sources/LanguageServerProtocol/Requests/DocumentSemanticTokensDeltaRequest.swift b/Sources/LanguageServerProtocol/Requests/DocumentSemanticTokensDeltaRequest.swift
index 55881c03b..e5a0297d9 100644
--- a/Sources/LanguageServerProtocol/Requests/DocumentSemanticTokensDeltaRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/DocumentSemanticTokensDeltaRequest.swift
@@ -28,7 +28,7 @@ public struct DocumentSemanticTokensDeltaRequest: TextDocumentRequest, Hashable
   }
 }
 
-public enum DocumentSemanticTokensDeltaResponse: ResponseType, Codable, Equatable {
+@frozen public enum DocumentSemanticTokensDeltaResponse: ResponseType, Codable, Equatable {
   case tokens(DocumentSemanticTokensResponse)
   case delta(SemanticTokensDelta)
 
diff --git a/Sources/LanguageServerProtocol/Requests/DocumentSymbolRequest.swift b/Sources/LanguageServerProtocol/Requests/DocumentSymbolRequest.swift
index 9ec14a5c9..a87697e3d 100644
--- a/Sources/LanguageServerProtocol/Requests/DocumentSymbolRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/DocumentSymbolRequest.swift
@@ -34,7 +34,7 @@ public struct DocumentSymbolRequest: TextDocumentRequest, Hashable {
   }
 }
 
-public enum DocumentSymbolResponse: ResponseType, Hashable {
+@frozen public enum DocumentSymbolResponse: ResponseType, Hashable {
   case documentSymbols([DocumentSymbol])
   case symbolInformation([SymbolInformation])
 
diff --git a/Sources/LanguageServerProtocol/Requests/HoverRequest.swift b/Sources/LanguageServerProtocol/Requests/HoverRequest.swift
index 87c1d407c..946ddbe59 100644
--- a/Sources/LanguageServerProtocol/Requests/HoverRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/HoverRequest.swift
@@ -55,12 +55,12 @@ public struct HoverResponse: ResponseType, Hashable {
   }
 }
 
-public enum HoverResponseContents: Hashable, Sendable {
+@frozen public enum HoverResponseContents: Hashable, Sendable {
   case markedStrings([MarkedString])
   case markupContent(MarkupContent)
 }
 
-public enum MarkedString: Hashable {
+@frozen public enum MarkedString: Hashable {
   private struct MarkdownCodeBlock: Codable {
     let language: String
     let value: String
diff --git a/Sources/LanguageServerProtocol/Requests/InlineValueRequest.swift b/Sources/LanguageServerProtocol/Requests/InlineValueRequest.swift
index ae0ef4788..9fc79728b 100644
--- a/Sources/LanguageServerProtocol/Requests/InlineValueRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/InlineValueRequest.swift
@@ -117,7 +117,7 @@ public struct InlineValueEvaluatableExpression: Codable, Hashable, Sendable {
 /// - as a name to use for a variable lookup (class InlineValueVariableLookup)
 /// - as an evaluatable expression (class InlineValueEvaluatableExpression)
 /// The InlineValue types combines all inline value types into one type.
-public enum InlineValue: ResponseType, Hashable, Sendable {
+@frozen public enum InlineValue: ResponseType, Hashable, Sendable {
   case text(InlineValueText)
   case variableLookup(InlineValueVariableLookup)
   case evaluatableExpression(InlineValueEvaluatableExpression)
diff --git a/Sources/LanguageServerProtocol/Requests/SignatureHelpRequest.swift b/Sources/LanguageServerProtocol/Requests/SignatureHelpRequest.swift
index 5abd1e87a..0cddae5de 100644
--- a/Sources/LanguageServerProtocol/Requests/SignatureHelpRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/SignatureHelpRequest.swift
@@ -160,7 +160,7 @@ public struct SignatureInformation: Codable, Hashable, Sendable {
 /// Represents a parameter of a callable-signature. A parameter can
 /// have a label and a doc-comment.
 public struct ParameterInformation: Codable, Hashable, Sendable {
-  public enum Label: Codable, Hashable, Sendable {
+  @frozen public enum Label: Codable, Hashable, Sendable {
     case string(String)
     case offsets(start: Int, end: Int)
 
diff --git a/Sources/LanguageServerProtocol/Requests/WorkspaceDiagnosticsRequest.swift b/Sources/LanguageServerProtocol/Requests/WorkspaceDiagnosticsRequest.swift
index 7abc34134..c383a2dbc 100644
--- a/Sources/LanguageServerProtocol/Requests/WorkspaceDiagnosticsRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/WorkspaceDiagnosticsRequest.swift
@@ -159,7 +159,7 @@ public struct WorkspaceUnchangedDocumentDiagnosticReport: Codable, Hashable, Sen
 }
 
 /// A workspace diagnostic document report.
-public enum WorkspaceDocumentDiagnosticReport: Codable, Hashable, Sendable {
+@frozen public enum WorkspaceDocumentDiagnosticReport: Codable, Hashable, Sendable {
   case full(WorkspaceFullDocumentDiagnosticReport)
   case unchanged(WorkspaceUnchangedDocumentDiagnosticReport)
 
diff --git a/Sources/LanguageServerProtocol/Requests/WorkspaceSymbolsRequest.swift b/Sources/LanguageServerProtocol/Requests/WorkspaceSymbolsRequest.swift
index 27543fc9b..f0f3511ba 100644
--- a/Sources/LanguageServerProtocol/Requests/WorkspaceSymbolsRequest.swift
+++ b/Sources/LanguageServerProtocol/Requests/WorkspaceSymbolsRequest.swift
@@ -34,7 +34,7 @@ public struct WorkspaceSymbolsRequest: LSPRequest, Hashable {
   }
 }
 
-public enum WorkspaceSymbolItem: ResponseType, Hashable {
+@frozen public enum WorkspaceSymbolItem: ResponseType, Hashable {
   case symbolInformation(SymbolInformation)
   case workspaceSymbol(WorkspaceSymbol)
 
@@ -94,7 +94,7 @@ public struct SymbolInformation: Hashable, ResponseType {
 
 /// A special workspace symbol that supports locations without a range
 public struct WorkspaceSymbol: ResponseType, Hashable {
-  public enum WorkspaceSymbolLocation: Codable, Hashable, Sendable {
+  @frozen public enum WorkspaceSymbolLocation: Codable, Hashable, Sendable {
     public struct URI: Codable, Hashable, Sendable {
       public var uri: DocumentURI
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/ClientCapabilities.swift b/Sources/LanguageServerProtocol/SupportTypes/ClientCapabilities.swift
index 231b6057b..a82154133 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/ClientCapabilities.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/ClientCapabilities.swift
@@ -977,7 +977,7 @@ public struct GeneralClientCapabilities: Hashable, Codable, Sendable {
 
   /// A type indicating how positions are encoded,
   /// specifically what column offsets mean.
-  public enum PositionEncodingKind: String, Hashable, Codable, Sendable {
+  @frozen public enum PositionEncodingKind: String, Hashable, Codable, Sendable {
 
     /// Character offsets count UTF-8 code units (e.g bytes).
     case utf8 = "utf-8"
diff --git a/Sources/LanguageServerProtocol/SupportTypes/CompletionItem.swift b/Sources/LanguageServerProtocol/SupportTypes/CompletionItem.swift
index 4bedc3230..f55808a81 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/CompletionItem.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/CompletionItem.swift
@@ -42,7 +42,7 @@ public struct CompletionItemTag: RawRepresentable, Codable, Hashable, Sendable {
   public static let deprecated = CompletionItemTag(rawValue: 1)
 }
 
-public enum CompletionItemEdit: Codable, Hashable, Sendable {
+@frozen public enum CompletionItemEdit: Codable, Hashable, Sendable {
   case textEdit(TextEdit)
   case insertReplaceEdit(InsertReplaceEdit)
 
@@ -205,7 +205,7 @@ public struct CompletionItem: ResponseType, Codable, Hashable, Sendable {
 }
 
 /// The format of the returned insertion text - either literal plain text or a snippet.
-public enum InsertTextFormat: Int, Codable, Hashable, Sendable {
+@frozen public enum InsertTextFormat: Int, Codable, Hashable, Sendable {
 
   /// The text to insert is plain text.
   case plain = 1
diff --git a/Sources/LanguageServerProtocol/SupportTypes/Diagnostic.swift b/Sources/LanguageServerProtocol/SupportTypes/Diagnostic.swift
index 1cef3d57e..18a4002b8 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/Diagnostic.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/Diagnostic.swift
@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 /// The severity level of a Diagnostic, between hint and error.
-public enum DiagnosticSeverity: Int, Codable, Hashable, Sendable {
+@frozen public enum DiagnosticSeverity: Int, Codable, Hashable, Sendable {
   case error = 1
   case warning = 2
   case information = 3
@@ -19,7 +19,7 @@ public enum DiagnosticSeverity: Int, Codable, Hashable, Sendable {
 }
 
 /// A unique diagnostic code, which may be used identifier the diagnostic in e.g. documentation.
-public enum DiagnosticCode: Hashable, Sendable {
+@frozen public enum DiagnosticCode: Hashable, Sendable {
   case number(Int)
   case string(String)
 }
diff --git a/Sources/LanguageServerProtocol/SupportTypes/InlayHint.swift b/Sources/LanguageServerProtocol/SupportTypes/InlayHint.swift
index d1d520559..1c1a86ca6 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/InlayHint.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/InlayHint.swift
@@ -74,7 +74,7 @@ public struct InlayHintKind: RawRepresentable, Codable, Hashable, Sendable {
 }
 
 /// A hint's label, either being a single string or a composition of parts.
-public enum InlayHintLabel: Codable, Hashable, Sendable {
+@frozen public enum InlayHintLabel: Codable, Hashable, Sendable {
   case parts([InlayHintLabelPart])
   case string(String)
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/LSPAny.swift b/Sources/LanguageServerProtocol/SupportTypes/LSPAny.swift
index 2b16e1cf2..f3d06b82a 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/LSPAny.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/LSPAny.swift
@@ -12,7 +12,7 @@
 
 /// Representation of 'any' in the Language Server Protocol, which is equivalent
 /// to an arbitrary JSON value.
-public enum LSPAny: Hashable, Sendable {
+@frozen public enum LSPAny: Hashable, Sendable {
   case null
   case int(Int)
   case bool(Bool)
diff --git a/Sources/LanguageServerProtocol/SupportTypes/LocationsOrLocationLinksResponse.swift b/Sources/LanguageServerProtocol/SupportTypes/LocationsOrLocationLinksResponse.swift
index 6ba402a33..a9b01f4dc 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/LocationsOrLocationLinksResponse.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/LocationsOrLocationLinksResponse.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum LocationsOrLocationLinksResponse: ResponseType, Hashable, Sendable {
+@frozen public enum LocationsOrLocationLinksResponse: ResponseType, Hashable, Sendable {
   case locations([Location])
   case locationLinks([LocationLink])
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/NotebookCellTextDocumentFilter.swift b/Sources/LanguageServerProtocol/SupportTypes/NotebookCellTextDocumentFilter.swift
index f1e2ae240..97c81bca4 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/NotebookCellTextDocumentFilter.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/NotebookCellTextDocumentFilter.swift
@@ -31,7 +31,7 @@ public struct NotebookDocumentFilter: Codable, Hashable, Sendable {
 /// A notebook cell text document filter denotes a cell text
 /// document by different properties.
 public struct NotebookCellTextDocumentFilter: Codable, Hashable, Sendable {
-  public enum NotebookFilter: Codable, Hashable, Sendable {
+  @frozen public enum NotebookFilter: Codable, Hashable, Sendable {
     case string(String)
     case notebookDocumentFilter(NotebookDocumentFilter)
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/ProgressToken.swift b/Sources/LanguageServerProtocol/SupportTypes/ProgressToken.swift
index 189a3c3ba..ffb5a4e4c 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/ProgressToken.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/ProgressToken.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum ProgressToken: Codable, Hashable, Sendable {
+@frozen public enum ProgressToken: Codable, Hashable, Sendable {
   case integer(Int)
   case string(String)
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/ServerCapabilities.swift b/Sources/LanguageServerProtocol/SupportTypes/ServerCapabilities.swift
index 0425df6e7..5f59e0671 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/ServerCapabilities.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/ServerCapabilities.swift
@@ -200,7 +200,7 @@ public struct ServerCapabilities: Codable, Hashable, Sendable {
   }
 }
 
-public enum ValueOrBool<ValueType: Codable>: Codable, Hashable where ValueType: Hashable {
+@frozen public enum ValueOrBool<ValueType: Codable>: Codable, Hashable where ValueType: Hashable {
   case bool(Bool)
   case value(ValueType)
 
@@ -240,7 +240,7 @@ public enum ValueOrBool<ValueType: Codable>: Codable, Hashable where ValueType:
 
 extension ValueOrBool: Sendable where ValueType: Sendable {}
 
-public enum TextDocumentSync: Codable, Hashable, Sendable {
+@frozen public enum TextDocumentSync: Codable, Hashable, Sendable {
   case options(TextDocumentSyncOptions)
   case kind(TextDocumentSyncKind)
 
@@ -342,7 +342,7 @@ public struct TextDocumentSyncOptions: Codable, Hashable, Sendable {
   }
 }
 
-public enum TextDocumentSyncKind: Int, Codable, Hashable, Sendable {
+@frozen public enum TextDocumentSyncKind: Int, Codable, Hashable, Sendable {
 
   /// Documents should not be synced at all.
   case none = 0
@@ -355,7 +355,7 @@ public enum TextDocumentSyncKind: Int, Codable, Hashable, Sendable {
   case incremental = 2
 }
 
-public enum NotebookFilter: Codable, Hashable, Sendable {
+@frozen public enum NotebookFilter: Codable, Hashable, Sendable {
   case string(String)
   case documentFilter(DocumentFilter)
 
@@ -748,7 +748,7 @@ public struct DocumentOnTypeFormattingOptions: Codable, Hashable, Sendable {
 /// Wrapper type for a server's CodeActions' capabilities.
 /// If the client supports CodeAction literals, the server can return specific information about
 /// how CodeActions will be sent. Otherwise, the server's capabilities are determined by a boolean.
-public enum CodeActionServerCapabilities: Codable, Hashable, Sendable {
+@frozen public enum CodeActionServerCapabilities: Codable, Hashable, Sendable {
 
   case supportsCodeActionRequests(Bool)
   case supportsCodeActionRequestsWithLiterals(CodeActionOptions)
@@ -1157,7 +1157,7 @@ public struct WorkspaceServerCapabilities: Codable, Hashable, Sendable {
     }
   }
 
-  public enum FileOperationPatternKind: String, Codable, Hashable {
+  @frozen public enum FileOperationPatternKind: String, Codable, Hashable {
     /// The pattern matches a file only.
     case file = "file"
     /// The pattern matches a folder only.
diff --git a/Sources/LanguageServerProtocol/SupportTypes/StringOrMarkupContent.swift b/Sources/LanguageServerProtocol/SupportTypes/StringOrMarkupContent.swift
index 90cfd4465..29d0c3ba5 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/StringOrMarkupContent.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/StringOrMarkupContent.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum StringOrMarkupContent: Codable, Hashable, Sendable {
+@frozen public enum StringOrMarkupContent: Codable, Hashable, Sendable {
   case string(String)
   case markupContent(MarkupContent)
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/TextDocumentEdit.swift b/Sources/LanguageServerProtocol/SupportTypes/TextDocumentEdit.swift
index 60f801151..50a1ba684 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/TextDocumentEdit.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/TextDocumentEdit.swift
@@ -14,7 +14,7 @@
 ///
 /// For an edit where the document is implied, use `TextEdit`.
 public struct TextDocumentEdit: Hashable, Codable, Sendable {
-  public enum Edit: Codable, Hashable, Sendable {
+  @frozen public enum Edit: Codable, Hashable, Sendable {
     case textEdit(TextEdit)
     case annotatedTextEdit(AnnotatedTextEdit)
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/TextDocumentSaveReason.swift b/Sources/LanguageServerProtocol/SupportTypes/TextDocumentSaveReason.swift
index 23b864893..2d0aa3642 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/TextDocumentSaveReason.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/TextDocumentSaveReason.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum TextDocumentSaveReason: Int, Codable, Hashable, Sendable {
+@frozen public enum TextDocumentSaveReason: Int, Codable, Hashable, Sendable {
 
   case manual = 1
 
diff --git a/Sources/LanguageServerProtocol/SupportTypes/Tracing.swift b/Sources/LanguageServerProtocol/SupportTypes/Tracing.swift
index d008578d2..ac0219062 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/Tracing.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/Tracing.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public enum Tracing: String, Codable, Sendable {
+@frozen public enum Tracing: String, Codable, Sendable {
   case off
   case messages
   case verbose
diff --git a/Sources/LanguageServerProtocol/SupportTypes/WindowMessageType.swift b/Sources/LanguageServerProtocol/SupportTypes/WindowMessageType.swift
index e3ae78cee..62673723a 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/WindowMessageType.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/WindowMessageType.swift
@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 /// The type of message (error, etc.) for a ShowMessage or LogMessage request. Corresponds to `MessageType` in LSP.
-public enum WindowMessageType: Int, Codable, Hashable, Sendable {
+@frozen public enum WindowMessageType: Int, Codable, Hashable, Sendable {
 
   case error = 1
   case warning = 2
diff --git a/Sources/LanguageServerProtocol/SupportTypes/WorkspaceEdit.swift b/Sources/LanguageServerProtocol/SupportTypes/WorkspaceEdit.swift
index 9e2793068..76f5b7176 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/WorkspaceEdit.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/WorkspaceEdit.swift
@@ -72,7 +72,7 @@ extension WorkspaceEdit: Codable {
   }
 }
 
-public enum WorkspaceEditDocumentChange: Codable, Hashable, Sendable {
+@frozen public enum WorkspaceEditDocumentChange: Codable, Hashable, Sendable {
   case textDocumentEdit(TextDocumentEdit)
   case createFile(CreateFile)
   case renameFile(RenameFile)
@@ -140,7 +140,7 @@ public struct CreateFile: Codable, Hashable, Sendable {
 
   // MARK: Codable conformance
 
-  public enum CodingKeys: String, CodingKey {
+  /*@nonexhaustive*/ public enum CodingKeys: String, CodingKey {
     case kind
     case uri
     case options
@@ -209,7 +209,7 @@ public struct RenameFile: Codable, Hashable, Sendable {
 
   // MARK: Codable conformance
 
-  public enum CodingKeys: String, CodingKey {
+  /*@nonexhaustive*/ public enum CodingKeys: String, CodingKey {
     case kind
     case oldUri
     case newUri
@@ -273,7 +273,7 @@ public struct DeleteFile: Codable, Hashable, Sendable {
 
   // MARK: Codable conformance
 
-  public enum CodingKeys: String, CodingKey {
+  /*@nonexhaustive*/ public enum CodingKeys: String, CodingKey {
     case kind
     case uri
     case options
diff --git a/Sources/LanguageServerProtocol/SupportTypes/WorkspaceSettings.swift b/Sources/LanguageServerProtocol/SupportTypes/WorkspaceSettings.swift
index 2f10218c6..6daaeb9b6 100644
--- a/Sources/LanguageServerProtocol/SupportTypes/WorkspaceSettings.swift
+++ b/Sources/LanguageServerProtocol/SupportTypes/WorkspaceSettings.swift
@@ -13,7 +13,7 @@
 /// The `settings` field of a `workspace/didChangeConfiguration`.
 ///
 /// This is typed as `Any` in the protocol, and this enum contains the formats we support.
-public enum WorkspaceSettingsChange: Codable, Hashable, Sendable {
+/*@nonexhaustive*/ public enum WorkspaceSettingsChange: Codable, Hashable, Sendable {
 
   case clangd(ClangWorkspaceSettings)
   case unknown(LSPAny)
diff --git a/Sources/LanguageServerProtocolTransport/BuildServerMessageDependencyTracker.swift b/Sources/LanguageServerProtocolTransport/BuildServerMessageDependencyTracker.swift
index 0b25cb756..8eb1e5d20 100644
--- a/Sources/LanguageServerProtocolTransport/BuildServerMessageDependencyTracker.swift
+++ b/Sources/LanguageServerProtocolTransport/BuildServerMessageDependencyTracker.swift
@@ -17,7 +17,7 @@ import ToolsProtocolsSwiftExtensions
 
 /// A lightweight way of describing tasks that are created from handling BSP
 /// requests or notifications for the purpose of dependency tracking.
-public enum BuildServerMessageDependencyTracker: QueueBasedMessageHandlerDependencyTracker {
+/*@nonexhaustive*/ public enum BuildServerMessageDependencyTracker: QueueBasedMessageHandlerDependencyTracker {
   /// A task that modifies some state. It is a barrier for all requests that read state.
   case stateChange
 
diff --git a/Sources/LanguageServerProtocolTransport/JSONRPCConnection.swift b/Sources/LanguageServerProtocolTransport/JSONRPCConnection.swift
index 919b1536b..5f07daf0e 100644
--- a/Sources/LanguageServerProtocolTransport/JSONRPCConnection.swift
+++ b/Sources/LanguageServerProtocolTransport/JSONRPCConnection.swift
@@ -31,7 +31,7 @@ import struct CDispatch.dispatch_fd_t
 /// For example, inside a language server, the `JSONRPCConnection` takes the language service implementation as its
 // `receiveHandler` and itself provides the client connection for sending notifications and callbacks.
 public final class JSONRPCConnection: Connection {
-  public enum TerminationReason: Sendable, Equatable {
+  @frozen public enum TerminationReason: Sendable, Equatable {
     /// The process on the other end of the `JSONRPCConnection` terminated with the given exit code.
     case exited(exitCode: Int32)
 
diff --git a/Sources/LanguageServerProtocolTransport/MessageCoding.swift b/Sources/LanguageServerProtocolTransport/MessageCoding.swift
index 1bfac6bde..03353dbc3 100644
--- a/Sources/LanguageServerProtocolTransport/MessageCoding.swift
+++ b/Sources/LanguageServerProtocolTransport/MessageCoding.swift
@@ -13,7 +13,7 @@
 import Foundation
 public import LanguageServerProtocol
 
-@_spi(Testing) public enum JSONRPCMessage {
+@_spi(Testing) @frozen public enum JSONRPCMessage {
   case notification(NotificationType)
   case request(_RequestType, id: RequestID)
   case response(ResponseType, id: RequestID)
diff --git a/Sources/SKLogging/NonDarwinLogging.swift b/Sources/SKLogging/NonDarwinLogging.swift
index 9a7f5fd09..f56084ac3 100644
--- a/Sources/SKLogging/NonDarwinLogging.swift
+++ b/Sources/SKLogging/NonDarwinLogging.swift
@@ -21,7 +21,7 @@ import Foundation
 
 // MARK: - Log settings
 
-@_spi(SourceKitLSP) public enum LogConfig {
+@_spi(SourceKitLSP) @frozen public enum LogConfig {
   /// The globally set log level
   private static let _logLevel = ThreadSafeBox<NonDarwinLogLevel>(
     initialValue: {
@@ -80,7 +80,7 @@ import Foundation
 ///
 /// For documentation of the different log levels see
 /// https://developer.apple.com/documentation/os/oslogtype.
-@_spi(SourceKitLSP) public enum NonDarwinLogLevel: Comparable, CustomStringConvertible, Sendable {
+@_spi(SourceKitLSP) @frozen public enum NonDarwinLogLevel: Comparable, CustomStringConvertible, Sendable {
   case debug
   case info
   case `default`
@@ -137,7 +137,7 @@ import Foundation
 ///
 /// For documentation of the different privacy levels see
 /// https://developer.apple.com/documentation/os/oslogprivacy.
-@_spi(SourceKitLSP) public enum NonDarwinLogPrivacy: Comparable, Sendable {
+@_spi(SourceKitLSP) @frozen public enum NonDarwinLogPrivacy: Comparable, Sendable {
   case `public`
   case `private`
   case sensitive