diff --git a/apps/lockfile-explorer/src/graph/lfxGraphLoader.ts b/apps/lockfile-explorer/src/graph/lfxGraphLoader.ts
index 732548d974..3db72dc314 100644
--- a/apps/lockfile-explorer/src/graph/lfxGraphLoader.ts
+++ b/apps/lockfile-explorer/src/graph/lfxGraphLoader.ts
@@ -21,6 +21,8 @@ import * as lockfilePath from './lockfilePath';
 type PnpmLockfileVersion = 54 | 60 | 90;
 type PeerDependenciesMeta = lockfileTypes.LockfilePackageInfo['peerDependenciesMeta'];
 
+let hasWarnedAboutOutdatedFormat: boolean = false;
+
 function createPackageLockfileDependency(options: {
   name: string;
   versionPath: string;
@@ -329,9 +331,16 @@ function createPackageLockfileEntry(options: {
     slashlessRawEntryId = rawEntryId;
   } else {
     if (!rawEntryId.startsWith('/')) {
-      throw new Error('Expecting leading "/" in path: ' + JSON.stringify(rawEntryId));
+      if (!hasWarnedAboutOutdatedFormat) {
+        console.warn(
+          'Your pnpm-lock.yaml contains outdated version formats. Please run "rush update --full" to fix this issue.'
+        );
+        hasWarnedAboutOutdatedFormat = true;
+      }
+      slashlessRawEntryId = rawEntryId;
+    } else {
+      slashlessRawEntryId = rawEntryId.substring(1);
     }
-    slashlessRawEntryId = rawEntryId.substring(1);
   }
 
   let dotPnpmSubfolder: string;
diff --git a/common/changes/@rushstack/lockfile-explorer/fix-lockfile-version-diffs_2026-02-20-02-06.json b/common/changes/@rushstack/lockfile-explorer/fix-lockfile-version-diffs_2026-02-20-02-06.json
new file mode 100644
index 0000000000..428456785c
--- /dev/null
+++ b/common/changes/@rushstack/lockfile-explorer/fix-lockfile-version-diffs_2026-02-20-02-06.json
@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/lockfile-explorer",
+      "comment": "Add user-friendly warning for outdated pnpm-lock.yaml instead of throwing an error. The warning suggests running \"rush update --full\" to fix the issue.",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@rushstack/lockfile-explorer"
+}
\ No newline at end of file