diff --git a/packages/trace-viewer/src/ui/modelUtil.ts b/packages/trace-viewer/src/ui/modelUtil.ts
index ba866ad7caf29..7993699e3f344 100644
--- a/packages/trace-viewer/src/ui/modelUtil.ts
+++ b/packages/trace-viewer/src/ui/modelUtil.ts
@@ -183,8 +183,8 @@ function mergeActionsAndUpdateTiming(contexts: ContextEntry[]) {
     if (traceFileToContexts.size > 1)
       makeCallIdsUniqueAcrossTraceFiles(contexts, ++traceFileId);
     // Align action times across runner and library contexts within each trace file.
-    const map = mergeActionsAndUpdateTimingSameTrace(contexts);
-    result.push(...map.values());
+    const actions = mergeActionsAndUpdateTimingSameTrace(contexts);
+    result.push(...actions);
   }
   result.sort((a1, a2) => {
     if (a2.parentId === a1.callId)
@@ -211,12 +211,19 @@ function makeCallIdsUniqueAcrossTraceFiles(contexts: ContextEntry[], traceFileId
   }
 }
 
-function mergeActionsAndUpdateTimingSameTrace(contexts: ContextEntry[]) {
+function mergeActionsAndUpdateTimingSameTrace(contexts: ContextEntry[]): ActionTraceEventInContext[] {
   const map = new Map<string, ActionTraceEventInContext>();
 
   const libraryContexts = contexts.filter(context => context.origin === 'library');
   const testRunnerContexts = contexts.filter(context => context.origin === 'testRunner');
 
+  // With library-only or test-runner-only traces there is nothing to match.
+  if (!testRunnerContexts.length || !libraryContexts.length) {
+    return contexts.map(context => {
+      return context.actions.map(action => ({ ...action, context }));
+    }).flat();
+  }
+
   // Library actions are replaced with corresponding test runner steps. Matching with
   // the test runner steps enables us to find parent steps.
   // - In the newer versions the actions are matched by explicit step id stored in the
@@ -264,7 +271,7 @@ function mergeActionsAndUpdateTimingSameTrace(contexts: ContextEntry[]) {
       map.set(key, { ...action, context });
     }
   }
-  return map;
+  return [...map.values()];
 }
 
 function adjustMonotonicTime(contexts: ContextEntry[], monotonicTimeDelta: number) {
diff --git a/tests/assets/trace-library-1.46.zip b/tests/assets/trace-library-1.46.zip
new file mode 100644
index 0000000000000..46d7d99bb49db
Binary files /dev/null and b/tests/assets/trace-library-1.46.zip differ
diff --git a/tests/library/trace-viewer.spec.ts b/tests/library/trace-viewer.spec.ts
index c2634df148905..c55e9c6594fbd 100644
--- a/tests/library/trace-viewer.spec.ts
+++ b/tests/library/trace-viewer.spec.ts
@@ -1236,3 +1236,14 @@ test('should open snapshot in new browser context', async ({ browser, page, runA
   await expect(newPage.getByText('hello')).toBeVisible();
   await newPage.close();
 });
+
+test('should show similar actions from library-only trace', async ({ showTraceViewer, asset }) => {
+  const traceViewer = await showTraceViewer([asset('trace-library-1.46.zip')]);
+  await expect(traceViewer.actionTitles).toHaveText([
+    /page.setContent/,
+    /locator.getAttributelocator\('div'\)/,
+    /locator.isVisiblelocator\('div'\)/,
+    /locator.getAttributelocator\('div'\)/,
+    /locator.isVisiblelocator\('div'\)/,
+  ]);
+});
diff --git a/tests/playwright-test/playwright.trace.spec.ts b/tests/playwright-test/playwright.trace.spec.ts
index 3e441fbf19ce6..9a692245f04e0 100644
--- a/tests/playwright-test/playwright.trace.spec.ts
+++ b/tests/playwright-test/playwright.trace.spec.ts
@@ -1113,6 +1113,39 @@ test('trace:retain-on-first-failure should create trace if request context is di
   expect(result.failed).toBe(1);
 });
 
+test('should not corrupt actions when no library trace is present', async ({ runInlineTest }) => {
+  const result = await runInlineTest({
+    'a.spec.ts': `
+      import { test as base, expect } from '@playwright/test';
+      const test = base.extend({
+        foo: async ({}, use) => {
+          expect(1).toBe(1);
+          await use();
+          expect(2).toBe(2);
+        },
+      });
+      test('fail', async ({ foo }) => {
+        expect(1).toBe(2);
+      });
+    `,
+  }, { trace: 'on' });
+  expect(result.exitCode).toBe(1);
+  expect(result.failed).toBe(1);
+
+  const tracePath = test.info().outputPath('test-results', 'a-fail', 'trace.zip');
+  const trace = await parseTrace(tracePath);
+  expect(trace.actionTree).toEqual([
+    'Before Hooks',
+    '  fixture: foo',
+    '    expect.toBe',
+    'expect.toBe',
+    'After Hooks',
+    '  fixture: foo',
+    '    expect.toBe',
+    'Worker Cleanup',
+  ]);
+});
+
 test('should record trace for manually created context in a failed test', async ({ runInlineTest }) => {
   test.info().annotations.push({ type: 'issue', description: 'https://github.com/microsoft/playwright/issues/31541' });