diff --git a/changelog.d/test-runner-swap-lock.fixed.md b/changelog.d/test-runner-swap-lock.fixed.md
new file mode 100644
index 0000000000..2d99a95458
--- /dev/null
+++ b/changelog.d/test-runner-swap-lock.fixed.md
@@ -0,0 +1,11 @@
+- Web test runner (`/wheels/core/tests` and `/wheels/app/tests`): the swap→run→restore window that
+  temporarily replaces the live `application.wheels` config with test configuration is now serialized
+  under an exclusive named lock, and the restore runs in a `finally` block. Overlapping test requests
+  can no longer clobber each other's `application.$$$wheels` backup and leave test config live until
+  the next `reload=true`, and an erroring suite now restores the original config too. ParallelRunner
+  partition sub-requests detect the already-applied swap and skip both the swap and the shared lock,
+  so parallel test mode does not deadlock. Note: this serializes test-vs-test only — a normal request
+  concurrent with a test run still sees swapped config; true isolation is deferred to a
+  separate-application-context design (refs [#3025](https://github.com/wheels-dev/wheels/issues/3025)).
+  Also removes the orphaned legacy RocketUnit runner twin `vendor/wheels/rocketunit_tests/Test.cfc`
+  (nothing loads it; the active legacy chain via `wheels.Test` is unchanged).
diff --git a/vendor/wheels/rocketunit_tests/Test.cfc b/vendor/wheels/rocketunit_tests/Test.cfc
deleted file mode 100644
index 213670c91c..0000000000
--- a/vendor/wheels/rocketunit_tests/Test.cfc
+++ /dev/null
@@ -1,37 +0,0 @@
-component extends="wheels.Test" {
-
-	/*
-	 * Executes once before the test suite runs.
-	 * Populates the test database on reload or if the authors table does not exist.
-	 */
-	function beforeAll() {
-		application.$$$wheels = duplicate(application.wheels);
-		local.tables = $dbinfo(datasource = application.wheels.dataSourceName, type = "tables");
-		local.tableList = ValueList(local.tables.table_name);
-		local.populate = StructKeyExists(url, "populate") ? url.populate : true;
-		if (local.populate || !FindNoCase("c_o_r_e_authors", local.tableList)) {
-			include "populate.cfm";
-		}
-	}
-
-	/*
-	 * Executes before every test case if called from the package via super.superSetup().
-	 */
-	function setup() {
-	}
-
-	/*
-	 * Executes after every test case if called from the package via super.superTeardown().
-	 */
-	function teardown() {
-	}
-
-	/*
-	 * Executes once after the test suite runs.
-	 */
-	function afterAll() {
-		application.wheels = application.$$$wheels;
-		structDelete(application, "$$$wheels");
-	}
-
-}
diff --git a/vendor/wheels/tests/runner.cfm b/vendor/wheels/tests/runner.cfm
index 8e88cc8a9a..13cccdb103 100644
--- a/vendor/wheels/tests/runner.cfm
+++ b/vendor/wheels/tests/runner.cfm
@@ -166,143 +166,176 @@
         bundlesDiscovered = local.bundlesDiscovered
     )
 
-    variables.$_setTestboxEnv()
-    if (!structKeyExists(url, "format") || url.format eq "html") {
-        result = testBox.run(
-            reporter = "wheels.wheelstest.system.reports.JSONReporter"
-        );
-        DeJsonResult = DeserializeJSON(result);
-
-        if (DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0) {
-            application.wo.$header(statuscode=417);
-        } else {
-            application.wo.$header(statuscode=200);
-        }
-    }
-    else if(url.format eq "json"){
-        result = testBox.run(
-            reporter = "wheels.wheelstest.system.reports.JSONReporter"
-        );
-        // `$header()` / `$content()` short-circuit when the servlet response is
-        // already committed (Adobe CF 2023/2025 commits mid-`testBox.run()` once
-        // any test output flushes the buffer). The status-code header is the
-        // signal the CI parser keys on, so best-effort is the right contract —
-        // a committed response keeps whatever statuscode the engine already
-        // wrote, and the JSON body still appends below.
-        application.wo.$content(type="application/json");
-        application.wo.$header(name="Access-Control-Allow-Origin", value="*");
-        DeJsonResult = DeserializeJSON(result);
-        if (DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0) {
-            if(!structKeyExists(url, "cli") || !url.cli){
-                application.wo.$header(statuscode=417);
+    // ── Concurrency guard (issue #3025) ─────────────────────────────────
+    // The swap→run→restore window below mutates the LIVE application.wheels
+    // struct ($_setTestboxEnv backs it up in application.$$$wheels and swaps
+    // in test config; the finally block swaps it back). Two overlapping test
+    // requests used to clobber each other's backup, which could restore TEST
+    // config as the live config until the next reload=true. Serialize the
+    // whole window under an exclusive named lock (precedent:
+    // migrator/TenantMigrator.cfc::$runForTenant).
+    //
+    // Re-entrancy: ParallelRunner partitions re-enter this template via
+    // fresh top-level HTTP GETs while the parent request holds the swap and
+    // the lock. Those sub-requests detect the already-applied swap
+    // (application.$$$wheels exists) and skip BOTH the swap and the shared
+    // lock — contending on the parent's lock would deadlock parallel mode.
+    // A unique per-request suffix turns their lock into a no-op.
+    local.runnerOwnsSwap = !StructKeyExists(application, "$$$wheels");
+    local.runnerLockSuffix = local.runnerOwnsSwap ? "" : "_sub_" & CreateUUID();
+    // Timeout must exceed the worst-case full-suite duration on the slowest
+    // engine; matches the requestTimeout at the top of this template.
+    lock name="wheelsTestRunner_#application.applicationName##local.runnerLockSuffix#" type="exclusive" timeout="1800" throwontimeout="true" {
+        try {
+            if (local.runnerOwnsSwap) {
+                variables.$_setTestboxEnv();
             }
-        } else {
-            application.wo.$header(statuscode=200);
-        }
-        // Check if 'only' parameter is provided in the URL
-        if (structKeyExists(url, "only") && url.only eq "failure,error") {
-            allBundles = DeJsonResult.bundleStats;
-            if(DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0){
-
-                // Filter test results
-                filteredBundles = [];
-
-                for (bundle in DeJsonResult.bundleStats) {
-                    if (bundle.totalError > 0 || bundle.totalFail > 0) {
-                        filteredSuites = [];
-
-                        for (suite in bundle.suiteStats) {
-                            if (suite.totalError > 0 || suite.totalFail > 0) {
-                                filteredSpecs = [];
-
-                                for (spec in suite.specStats) {
-                                    if (spec.status eq "Error" || spec.status eq "Failed") {
-                                        arrayAppend(filteredSpecs, spec);
+            if (!structKeyExists(url, "format") || url.format eq "html") {
+                result = testBox.run(
+                    reporter = "wheels.wheelstest.system.reports.JSONReporter"
+                );
+                DeJsonResult = DeserializeJSON(result);
+
+                if (DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0) {
+                    application.wo.$header(statuscode=417);
+                } else {
+                    application.wo.$header(statuscode=200);
+                }
+            }
+            else if(url.format eq "json"){
+                result = testBox.run(
+                    reporter = "wheels.wheelstest.system.reports.JSONReporter"
+                );
+                // `$header()` / `$content()` short-circuit when the servlet response is
+                // already committed (Adobe CF 2023/2025 commits mid-`testBox.run()` once
+                // any test output flushes the buffer). The status-code header is the
+                // signal the CI parser keys on, so best-effort is the right contract —
+                // a committed response keeps whatever statuscode the engine already
+                // wrote, and the JSON body still appends below.
+                application.wo.$content(type="application/json");
+                application.wo.$header(name="Access-Control-Allow-Origin", value="*");
+                DeJsonResult = DeserializeJSON(result);
+                if (DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0) {
+                    if(!structKeyExists(url, "cli") || !url.cli){
+                        application.wo.$header(statuscode=417);
+                    }
+                } else {
+                    application.wo.$header(statuscode=200);
+                }
+                // Check if 'only' parameter is provided in the URL
+                if (structKeyExists(url, "only") && url.only eq "failure,error") {
+                    allBundles = DeJsonResult.bundleStats;
+                    if(DeJsonResult.totalFail > 0 || DeJsonResult.totalError > 0){
+
+                        // Filter test results
+                        filteredBundles = [];
+
+                        for (bundle in DeJsonResult.bundleStats) {
+                            if (bundle.totalError > 0 || bundle.totalFail > 0) {
+                                filteredSuites = [];
+
+                                for (suite in bundle.suiteStats) {
+                                    if (suite.totalError > 0 || suite.totalFail > 0) {
+                                        filteredSpecs = [];
+
+                                        for (spec in suite.specStats) {
+                                            if (spec.status eq "Error" || spec.status eq "Failed") {
+                                                arrayAppend(filteredSpecs, spec);
+                                            }
+                                        }
+
+                                        if (arrayLen(filteredSpecs) > 0) {
+                                            suite.specStats = filteredSpecs;
+                                            arrayAppend(filteredSuites, suite);
+                                        }
                                     }
                                 }
 
-                                if (arrayLen(filteredSpecs) > 0) {
-                                    suite.specStats = filteredSpecs;
-                                    arrayAppend(filteredSuites, suite);
+                                if (arrayLen(filteredSuites) > 0) {
+                                    bundle.suiteStats = filteredSuites;
+                                    arrayAppend(filteredBundles, bundle);
                                 }
                             }
                         }
 
-                        if (arrayLen(filteredSuites) > 0) {
-                            bundle.suiteStats = filteredSuites;
-                            arrayAppend(filteredBundles, bundle);
-                        }
-                    }
-                }
+                        DeJsonResult.bundleStats = filteredBundles;
+                        // Update the result with filtered data
 
-                DeJsonResult.bundleStats = filteredBundles;
-                // Update the result with filtered data
-
-                // Build lookup of filtered bundles by name for safe access
-                filteredBundleMap = {};
-                for (fb in filteredBundles) {
-                    filteredBundleMap[fb.name] = fb;
-                }
+                        // Build lookup of filtered bundles by name for safe access
+                        filteredBundleMap = {};
+                        for (fb in filteredBundles) {
+                            filteredBundleMap[fb.name] = fb;
+                        }
 
-                for(bundle in allBundles){
-                    writeOutput("Bundle: #bundle.name##Chr(13)##Chr(10)#")
-                    writeOutput("CFML Engine: #DeJsonResult.CFMLEngine# #DeJsonResult.CFMLEngineVersion##Chr(13)##Chr(10)#")
-                    writeOutput("Duration: #bundle.totalDuration#ms#Chr(13)##Chr(10)#")
-                    writeOutput("Labels: #ArrayToList(DeJsonResult.labels, ', ')##Chr(13)##Chr(10)#")
-                    writeOutput("╔═══════════════════════════════════════════════════════════╗#Chr(13)##Chr(10)#║ Suites  ║ Specs   ║ Passed  ║ Failed  ║ Errored ║ Skipped ║#Chr(13)##Chr(10)#╠═══════════════════════════════════════════════════════════╣#Chr(13)##Chr(10)#║ #NumberFormat(bundle.totalSuites,'999')#     ║ #NumberFormat(bundle.totalSpecs,'999')#     ║ #NumberFormat(bundle.totalPass,'999')#     ║ #NumberFormat(bundle.totalFail,'999')#     ║ #NumberFormat(bundle.totalError,'999')#     ║ #NumberFormat(bundle.totalSkipped,'999')#     ║#Chr(13)##Chr(10)#╚═══════════════════════════════════════════════════════════╝#Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
-                    if(bundle.totalFail > 0 || bundle.totalError > 0){
-                        if (structKeyExists(filteredBundleMap, bundle.name)) {
-                            for(suite in filteredBundleMap[bundle.name].suiteStats){
-                                writeOutput("Suite with Error or Failure: #suite.name##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
-                                for(spec in suite.specStats){
-                                    writeOutput("       Spec Name: #spec.name##Chr(13)##Chr(10)#")
-                                    writeOutput("       Error Message: #spec.failMessage##Chr(13)##Chr(10)#")
-                                    writeOutput("       Error Detail: #spec.failDetail##Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                        for(bundle in allBundles){
+                            writeOutput("Bundle: #bundle.name##Chr(13)##Chr(10)#")
+                            writeOutput("CFML Engine: #DeJsonResult.CFMLEngine# #DeJsonResult.CFMLEngineVersion##Chr(13)##Chr(10)#")
+                            writeOutput("Duration: #bundle.totalDuration#ms#Chr(13)##Chr(10)#")
+                            writeOutput("Labels: #ArrayToList(DeJsonResult.labels, ', ')##Chr(13)##Chr(10)#")
+                            writeOutput("╔═══════════════════════════════════════════════════════════╗#Chr(13)##Chr(10)#║ Suites  ║ Specs   ║ Passed  ║ Failed  ║ Errored ║ Skipped ║#Chr(13)##Chr(10)#╠═══════════════════════════════════════════════════════════╣#Chr(13)##Chr(10)#║ #NumberFormat(bundle.totalSuites,'999')#     ║ #NumberFormat(bundle.totalSpecs,'999')#     ║ #NumberFormat(bundle.totalPass,'999')#     ║ #NumberFormat(bundle.totalFail,'999')#     ║ #NumberFormat(bundle.totalError,'999')#     ║ #NumberFormat(bundle.totalSkipped,'999')#     ║#Chr(13)##Chr(10)#╚═══════════════════════════════════════════════════════════╝#Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                            if(bundle.totalFail > 0 || bundle.totalError > 0){
+                                if (structKeyExists(filteredBundleMap, bundle.name)) {
+                                    for(suite in filteredBundleMap[bundle.name].suiteStats){
+                                        writeOutput("Suite with Error or Failure: #suite.name##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                                        for(spec in suite.specStats){
+                                            writeOutput("       Spec Name: #spec.name##Chr(13)##Chr(10)#")
+                                            writeOutput("       Error Message: #spec.failMessage##Chr(13)##Chr(10)#")
+                                            writeOutput("       Error Detail: #spec.failDetail##Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                                        }
+                                    }
                                 }
                             }
+                            writeOutput("#Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
                         }
-                    }
-                    writeOutput("#Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
-                }
 
-            }else{
-                for(bundle in DeJsonResult.bundleStats){
-                    writeOutput("Bundle: #bundle.name##Chr(13)##Chr(10)#")
-                    writeOutput("CFML Engine: #DeJsonResult.CFMLEngine# #DeJsonResult.CFMLEngineVersion##Chr(13)##Chr(10)#")
-                    writeOutput("Duration: #bundle.totalDuration#ms#Chr(13)##Chr(10)#")
-                    writeOutput("Labels: #ArrayToList(DeJsonResult.labels, ', ')##Chr(13)##Chr(10)#")
-                    writeOutput("╔═══════════════════════════════════════════════════════════╗#Chr(13)##Chr(10)#║ Suites  ║ Specs   ║ Passed  ║ Failed  ║ Errored ║ Skipped ║#Chr(13)##Chr(10)#╠═══════════════════════════════════════════════════════════╣#Chr(13)##Chr(10)#║ #NumberFormat(bundle.totalSuites,'999')#     ║ #NumberFormat(bundle.totalSpecs,'999')#     ║ #NumberFormat(bundle.totalPass,'999')#     ║ #NumberFormat(bundle.totalFail,'999')#     ║ #NumberFormat(bundle.totalError,'999')#     ║ #NumberFormat(bundle.totalSkipped,'999')#     ║#Chr(13)##Chr(10)#╚═══════════════════════════════════════════════════════════╝#Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                    }else{
+                        for(bundle in DeJsonResult.bundleStats){
+                            writeOutput("Bundle: #bundle.name##Chr(13)##Chr(10)#")
+                            writeOutput("CFML Engine: #DeJsonResult.CFMLEngine# #DeJsonResult.CFMLEngineVersion##Chr(13)##Chr(10)#")
+                            writeOutput("Duration: #bundle.totalDuration#ms#Chr(13)##Chr(10)#")
+                            writeOutput("Labels: #ArrayToList(DeJsonResult.labels, ', ')##Chr(13)##Chr(10)#")
+                            writeOutput("╔═══════════════════════════════════════════════════════════╗#Chr(13)##Chr(10)#║ Suites  ║ Specs   ║ Passed  ║ Failed  ║ Errored ║ Skipped ║#Chr(13)##Chr(10)#╠═══════════════════════════════════════════════════════════╣#Chr(13)##Chr(10)#║ #NumberFormat(bundle.totalSuites,'999')#     ║ #NumberFormat(bundle.totalSpecs,'999')#     ║ #NumberFormat(bundle.totalPass,'999')#     ║ #NumberFormat(bundle.totalFail,'999')#     ║ #NumberFormat(bundle.totalError,'999')#     ║ #NumberFormat(bundle.totalSkipped,'999')#     ║#Chr(13)##Chr(10)#╚═══════════════════════════════════════════════════════════╝#Chr(13)##Chr(10)##Chr(13)##Chr(10)##Chr(13)##Chr(10)#")
+                        }
+                    }
+                }else{
+                    // Thread the resolved-scope facts (and any warnings) into the JSON
+                    // payload so a rejected directory or a 0-bundle discovery is
+                    // detectable instead of masquerading as a green run (issue #3083).
+                    writeOutput(local.scopeResolver.injectScopeMetadata(
+                        resultJson = result,
+                        scope = local.testScope,
+                        bundlesDiscovered = local.bundlesDiscovered,
+                        warnings = local.scopeWarnings
+                    ))
                 }
             }
-        }else{
-            // Thread the resolved-scope facts (and any warnings) into the JSON
-            // payload so a rejected directory or a 0-bundle discovery is
-            // detectable instead of masquerading as a green run (issue #3083).
-            writeOutput(local.scopeResolver.injectScopeMetadata(
-                resultJson = result,
-                scope = local.testScope,
-                bundlesDiscovered = local.bundlesDiscovered,
-                warnings = local.scopeWarnings
-            ))
+            else if (url.format eq "txt") {
+                result = testBox.run(
+                    reporter = "wheels.wheelstest.system.reports.TextReporter"
+                )
+                application.wo.$content(type="text/plain");
+                writeOutput(result)
+            }
+            else if(url.format eq "junit"){
+                result = testBox.run(
+                    reporter = "wheels.wheelstest.system.reports.ANTJUnitReporter"
+                )
+                application.wo.$content(type="text/xml");
+                writeOutput(result)
+            }
+        } finally {
+            // Reset the original environment. Only the request that created
+            // the backup restores it — sub-requests never touch the live
+            // config — and the restore now also runs when the suite errors
+            // out (previously an exception left test config live until the
+            // next reload). No loops in this finally block (Lucee 7
+            // miscompiles local-scoped loops in finally — invariant 12).
+            if (local.runnerOwnsSwap && StructKeyExists(application, "$$$wheels")) {
+                application.wheels = application.$$$wheels;
+                structDelete(application, "$$$wheels");
+            }
         }
     }
-    else if (url.format eq "txt") {
-        result = testBox.run(
-            reporter = "wheels.wheelstest.system.reports.TextReporter"
-        )
-        application.wo.$content(type="text/plain");
-        writeOutput(result)
-    }
-    else if(url.format eq "junit"){
-        result = testBox.run(
-            reporter = "wheels.wheelstest.system.reports.ANTJUnitReporter"
-        )
-        application.wo.$content(type="text/xml");
-        writeOutput(result)
-    }
-    // reset the original environment
-    application.wheels = application.$$$wheels
-    structDelete(application, "$$$wheels")
     if(!structKeyExists(url, "format") || url.format eq "html"){
         // Use our html template
         type = "Core";
diff --git a/vendor/wheels/tests/specs/internal/TestRunnerSwapLockSpec.cfc b/vendor/wheels/tests/specs/internal/TestRunnerSwapLockSpec.cfc
new file mode 100644
index 0000000000..da0000241b
--- /dev/null
+++ b/vendor/wheels/tests/specs/internal/TestRunnerSwapLockSpec.cfc
@@ -0,0 +1,122 @@
+/**
+ * Guards for issue #3025 (Stage-1 slice): the web test runner
+ * (vendor/wheels/tests/runner.cfm) swaps the LIVE application.wheels struct
+ * for test configuration (backing it up in application.$$$wheels) and
+ * restores it when the suite completes. Two overlapping test requests used
+ * to clobber each other's backup, which could restore TEST config as the
+ * live config until the next reload=true (issue #2887 "they fight each
+ * other"). The fix serializes the swap->run->restore window under an
+ * exclusive named lock, with a re-entrancy guard so ParallelRunner
+ * partition sub-requests (fresh top-level HTTP GETs issued while the parent
+ * request holds the swap) skip BOTH the swap and the shared lock instead of
+ * deadlocking parallel mode.
+ *
+ * Two kinds of coverage:
+ *
+ * 1. Structural (precedent: security/BareCfabortGuardSpec.cfc) — runner.cfm
+ *    must contain the exclusive named-lock acquisition and the
+ *    already-swapped detection. The lock itself cannot be observed from
+ *    inside the suite (this spec executes while the lock is held), so the
+ *    source scan is the practical gate.
+ *
+ * 2. Behavioral — a completed nested run (same shape as a ParallelRunner
+ *    partition request) must leave the parent request's swap fully intact:
+ *    application.$$$wheels still present and application.wheels still
+ *    pointing at test config. Before the fix the nested run overwrote the
+ *    parent's backup with test config, restored it as "live", and deleted
+ *    the backup key — erroring the parent's own restore.
+ */
+component extends="wheels.WheelsTest" {
+
+	function run() {
+
+		describe("Web test-runner swap serialization (issue ##3025)", () => {
+
+			it("runner.cfm acquires an exclusive named lock around the config swap window", () => {
+				var source = FileRead(ExpandPath("/wheels/tests/runner.cfm"));
+				var fileLines = ListToArray(source, Chr(10), true);
+				var foundLock = false;
+				var foundGuard = false;
+				for (var rawLine in fileLines) {
+					var trimmed = Trim(Replace(rawLine, Chr(13), "", "all"));
+					// Skip comment-only lines so a commented-out lock can
+					// never satisfy this guard (Anti-Pattern 14 spirit).
+					if (Left(trimmed, 2) == "//" || Left(trimmed, 1) == "*" || Left(trimmed, 2) == "/*") {
+						continue;
+					}
+					// The exclusive named-lock acquisition on the shared
+					// runner lock name.
+					if (
+						REFindNoCase("(^|[\s;{}])lock\s+[^{]*name\s*=", trimmed)
+						&& FindNoCase("wheelsTestRunner_", trimmed)
+						&& REFindNoCase("type\s*=\s*[""']exclusive[""']", trimmed)
+						&& REFindNoCase("throwontimeout", trimmed)
+					) {
+						foundLock = true;
+					}
+					// The re-entrancy detection: sub-requests recognize an
+					// already-applied swap via the backup key.
+					if (FindNoCase("StructKeyExists(application, ""$$$wheels"")", trimmed)) {
+						foundGuard = true;
+					}
+				}
+				expect(foundLock).toBeTrue(
+					"runner.cfm must wrap the config swap window in an exclusive named lock ('wheelsTestRunner_...', throwOnTimeout) — issue ##3025"
+				);
+				expect(foundGuard).toBeTrue(
+					"runner.cfm must detect an already-applied swap via StructKeyExists(application, '$$$wheels') so ParallelRunner sub-requests skip the swap and the shared lock"
+				);
+			});
+
+			it("runner.cfm restores the original config in a finally block", () => {
+				var source = FileRead(ExpandPath("/wheels/tests/runner.cfm"));
+				expect(Find("finally", source) > 0).toBeTrue(
+					"runner.cfm must restore application.wheels from the backup inside a finally block so an erroring suite can no longer leave test config live"
+				);
+				expect(Find("application.wheels = application.$$$wheels", source) > 0).toBeTrue(
+					"runner.cfm must restore application.wheels from application.$$$wheels"
+				);
+			});
+
+			it("a completed nested run leaves the parent request's swap intact", () => {
+				// This spec itself executes inside the swap window, so the
+				// backup key must be present right now.
+				expect(StructKeyExists(application, "$$$wheels")).toBeTrue(
+					"precondition: the suite is running inside the swap window"
+				);
+
+				// Same shape as a ParallelRunner partition request: a fresh
+				// top-level GET back into the runner while this request holds
+				// the swap. Point directory= at a single bundle file so the
+				// nested run discovers 0 bundles and completes green in
+				// milliseconds (the issue-3083 '0-bundle' shape), and pass
+				// populate=false so pre-fix engines do not repopulate the
+				// database mid-suite.
+				var requestParams = {
+					format = "json",
+					cli = "true",
+					populate = "false",
+					directory = "wheels.tests.specs.internal.parallelRunnerSpec"
+				};
+				if (StructKeyExists(url, "db")) {
+					requestParams.db = url.db;
+				}
+				var tc = $testClient().get(path = "/wheels/core/tests", params = requestParams);
+				expect(tc.statusCode()).toBe(200, "the nested runner request must complete green");
+
+				// The nested run must NOT have deleted the parent's backup...
+				expect(StructKeyExists(application, "$$$wheels")).toBeTrue(
+					"a completed nested run must not delete the parent's application.$$$wheels backup — only the request that created the swap restores it (issue ##3025)"
+				);
+				// ...and must NOT have restored live config over the
+				// in-progress parent run (transactionMode='none' is one of
+				// the swapped-in test settings).
+				expect(application.wheels.transactionMode).toBe(
+					"none",
+					"a completed nested run must not restore the live config while the parent run is still executing"
+				);
+			});
+
+		});
+	}
+}