diff --git a/internal/ls/lsconv/converters.go b/internal/ls/lsconv/converters.go
index 1caf5da494a..1035d38e852 100644
--- a/internal/ls/lsconv/converters.go
+++ b/internal/ls/lsconv/converters.go
@@ -300,9 +300,16 @@ func diagnosticToLSP(ctx context.Context, converters *Converters, diagnostic *as
 
 	var tags []lsproto.DiagnosticTag
 	if len(opts.tagValueSet) > 0 && (diagnostic.ReportsUnnecessary() || diagnostic.ReportsDeprecated()) {
-		tags = make([]lsproto.DiagnosticTag, 0, 2)
+		tags = make([]lsproto.DiagnosticTag, 0, 3)
 		if diagnostic.ReportsUnnecessary() && slices.Contains(opts.tagValueSet, lsproto.DiagnosticTagUnnecessary) {
 			tags = append(tags, lsproto.DiagnosticTagUnnecessary)
+			// Visual Studio's LSP client only renders Unnecessary diagnostics as
+			// faded-out text when they also carry the VS-internal HiddenInEditor
+			// tag; otherwise they appear as a regular squiggle. Emit it so VS
+			// matches the LSP-spec intent of the Unnecessary tag.
+			if opts.visualStudio {
+				tags = append(tags, lsproto.DiagnosticTagVsHiddenInEditor)
+			}
 		}
 		if diagnostic.ReportsDeprecated() && slices.Contains(opts.tagValueSet, lsproto.DiagnosticTagDeprecated) {
 			tags = append(tags, lsproto.DiagnosticTagDeprecated)
diff --git a/internal/lsp/lsproto/_generate/generate.mts b/internal/lsp/lsproto/_generate/generate.mts
index 33b6c7bf3fe..61a6f2cd318 100755
--- a/internal/lsp/lsproto/_generate/generate.mts
+++ b/internal/lsp/lsproto/_generate/generate.mts
@@ -1112,6 +1112,22 @@ function patchAndPreprocessModel() {
         (reg as any).isRegistrationOnly = !allRequestMethods.has(reg.registrationMethod);
     }
 
+    // Add Visual Studio-specific DiagnosticTag values.
+    // These are VS-internal extensions not part of the LSP spec. They use sentinel
+    // values near int32.MaxValue to avoid collisions with future standard additions.
+    // Servers should only emit them when the client advertises
+    // _vs_supportsVisualStudioExtensions.
+    const diagnosticTagEnum = model.enumerations.find(e => e.name === "DiagnosticTag");
+    if (diagnosticTagEnum) {
+        diagnosticTagEnum.values.push(
+            {
+                name: "VSHiddenInEditor",
+                value: 2147483641, // int32.MaxValue - 6
+                documentation: "Visual Studio-specific tag: the diagnostic is not rendered with a squiggle in the editor. When combined with Unnecessary, Visual Studio renders the code as faded-out text rather than a squiggle.",
+            },
+        );
+    }
+
     // Merge LSPErrorCodes into ErrorCodes and remove LSPErrorCodes
     const errorCodesEnum = model.enumerations.find(e => e.name === "ErrorCodes");
     const lspErrorCodesEnum = model.enumerations.find(e => e.name === "LSPErrorCodes");
diff --git a/internal/lsp/lsproto/lsp_generated.go b/internal/lsp/lsproto/lsp_generated.go
index 9acd888fa10..4f0d3013d57 100644
--- a/internal/lsp/lsproto/lsp_generated.go
+++ b/internal/lsp/lsproto/lsp_generated.go
@@ -30674,18 +30674,27 @@ const (
 	//
 	// Clients are allowed to rendered diagnostics with this tag strike through.
 	DiagnosticTagDeprecated DiagnosticTag = 2
+	// Visual Studio-specific tag: the diagnostic is not rendered with a squiggle in the editor. When combined with Unnecessary, Visual Studio renders the code as faded-out text rather than a squiggle.
+	DiagnosticTagVsHiddenInEditor DiagnosticTag = 2147483641
 )
 
-const _DiagnosticTag_name = "UnnecessaryDeprecated"
+const _DiagnosticTag_name = "UnnecessaryDeprecatedVsHiddenInEditor"
 
-var _DiagnosticTag_index = [...]uint16{0, 11, 21}
+var (
+	_DiagnosticTag_index_0 = [...]uint16{0, 11, 21}
+	_DiagnosticTag_index_1 = [...]uint16{0, 16}
+)
 
 func (e DiagnosticTag) String() string {
-	i := int(e) - 1
-	if i < 0 || i >= len(_DiagnosticTag_index)-1 {
+	switch {
+	case 1 <= e && e <= 2:
+		i := int(e) - 1
+		return _DiagnosticTag_name[0+_DiagnosticTag_index_0[i] : 0+_DiagnosticTag_index_0[i+1]]
+	case e == 2147483641:
+		return _DiagnosticTag_name[21:37]
+	default:
 		return fmt.Sprintf("DiagnosticTag(%d)", e)
 	}
-	return _DiagnosticTag_name[_DiagnosticTag_index[i]:_DiagnosticTag_index[i+1]]
 }
 
 // How a completion was triggered