diff --git a/src/traceDiagnosticFilter.ts b/src/traceDiagnosticFilter.ts
new file mode 100644
index 0000000..ed4cb29
--- /dev/null
+++ b/src/traceDiagnosticFilter.ts
@@ -0,0 +1,32 @@
+import * as ts from 'typescript'
+
+const declarationFilePattern = /\.d\.(?:cts|mts|ts)$/i
+
+export function shouldSuppressTraceDiagnostic(fileName: string, sourceText: string, position: number): boolean {
+  return createTraceDiagnosticFilter(fileName, sourceText)(position)
+}
+
+export function createTraceDiagnosticFilter(fileName: string, sourceText: string) {
+  if (declarationFilePattern.test(fileName))
+    return () => true
+
+  const sourceFile = ts.createSourceFile(fileName, sourceText, ts.ScriptTarget.Latest, true)
+  return (position: number) => {
+    const node = findNodeAtPosition(sourceFile, position)
+
+    for (let current = node; current; current = current.parent) {
+      if (ts.isTypeAliasDeclaration(current) || ts.isInterfaceDeclaration(current))
+        return true
+    }
+
+    return false
+  }
+}
+
+function findNodeAtPosition(node: ts.Node, position: number): ts.Node | undefined {
+  if (position < node.getStart() || position >= node.getEnd())
+    return undefined
+
+  const child = ts.forEachChild(node, current => findNodeAtPosition(current, position))
+  return child ?? node
+}
diff --git a/src/traceDiagnostics.ts b/src/traceDiagnostics.ts
index 48e5601..7af59d9 100644
--- a/src/traceDiagnostics.ts
+++ b/src/traceDiagnostics.ts
@@ -2,6 +2,7 @@ import * as vscode from 'vscode'
 import type { FileStat } from '../shared/src/messages'
 import { getStatsFromTree } from './traceTree'
 import { afterConfigUpdate, getCurrentConfig } from './configuration'
+import { createTraceDiagnosticFilter } from './traceDiagnosticFilter'
 
 let diagnosticCollection: vscode.DiagnosticCollection
 
@@ -49,6 +50,8 @@ export async function addTraceDiagnostics(fileName: string, stats: FileStat[]) {
   fileStatus.set(fileName, 'clean')
 
   const document = await vscode.workspace.openTextDocument(uri)
+  const sourceText = document.getText()
+  const shouldSuppressTraceDiagnostic = createTraceDiagnosticFilter(document.fileName, sourceText)
 
   let averages
 
@@ -72,6 +75,9 @@ export async function addTraceDiagnostics(fileName: string, stats: FileStat[]) {
     if (lastPos === stat.pos)
       continue // do not create diagnostics for further checks at the same starting position
 
+    if (shouldSuppressTraceDiagnostic(stat.pos))
+      continue
+
     const diagnostic = toDiagnistic(stat, document, averages!)
     if (diagnostic)
       diagnostics.push(diagnostic)
diff --git a/test/trace-diagnostic-filter.test.ts b/test/trace-diagnostic-filter.test.ts
new file mode 100644
index 0000000..d81def7
--- /dev/null
+++ b/test/trace-diagnostic-filter.test.ts
@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest'
+import { shouldSuppressTraceDiagnostic } from '../src/traceDiagnosticFilter'
+
+describe('shouldSuppressTraceDiagnostic', () => {
+  it('suppresses declaration files', () => {
+    expect(shouldSuppressTraceDiagnostic('node_modules/typescript/lib/lib.es2020.date.d.ts', 'declare const Date: DateConstructor', 10)).toBe(true)
+  })
+
+  it('suppresses type alias diagnostics anywhere in the declaration', () => {
+    const source = `export type ConstructorOf<Instance extends object> = new (
+  ...args: any[]
+) => Instance`
+
+    expect(shouldSuppressTraceDiagnostic('src/example.ts', source, source.indexOf('any[]'))).toBe(true)
+  })
+
+  it('suppresses interface diagnostics', () => {
+    const source = `export interface Person {
+  name: string
+}`
+
+    expect(shouldSuppressTraceDiagnostic('src/example.ts', source, source.indexOf('string'))).toBe(true)
+  })
+
+  it('keeps value-level diagnostics', () => {
+    const source = `export const person: Person = {
+  name: 'Ada',
+}`
+
+    expect(shouldSuppressTraceDiagnostic('src/example.ts', source, source.indexOf('Person'))).toBe(false)
+  })
+})