diff --git a/.changeset/fast-diagnostics-tests.md b/.changeset/fast-diagnostics-tests.md
new file mode 100644
index 00000000..009c35ff
--- /dev/null
+++ b/.changeset/fast-diagnostics-tests.md
@@ -0,0 +1,5 @@
+---
+"@effect/language-service": patch
+---
+
+Enable `skipLibCheck` in the diagnostics test harness to reduce test runtime and memory usage.
diff --git a/packages/language-service/test/diagnostics.test.ts b/packages/language-service/test/diagnostics.test.ts
index de079eba..8f85908c 100644
--- a/packages/language-service/test/diagnostics.test.ts
+++ b/packages/language-service/test/diagnostics.test.ts
@@ -27,6 +27,7 @@ const getExamplesDiagnosticsDir = () => getExamplesSubdir("diagnostics")
 
 function compilerOptionsFromSourceComment(sourceText: string): ts.CompilerOptions {
   return {
+    skipLibCheck: true,
     ...(sourceText.includes("// @strict") ? { strict: true } : {})
   }
 }