diff --git a/framework/service/src/test/groovy/org/apache/ofbiz/service/eca/ServiceEcaUtilConcurrencyTest.groovy b/framework/service/src/test/groovy/org/apache/ofbiz/service/eca/ServiceEcaUtilConcurrencyTest.groovy
new file mode 100644
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+++ b/framework/service/src/test/groovy/org/apache/ofbiz/service/eca/ServiceEcaUtilConcurrencyTest.groovy
@@ -0,0 +1,190 @@
+/*******************************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *******************************************************************************/
+package org.apache.ofbiz.service.eca
+
+import org.apache.ofbiz.base.config.GenericConfigException
+import org.apache.ofbiz.base.config.ResourceHandler
+import org.apache.ofbiz.base.util.UtilXml
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Timeout
+import org.w3c.dom.Document
+
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.ExecutorService
+import java.util.concurrent.Executors
+import java.util.concurrent.Future
+import java.util.concurrent.ThreadFactory
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicBoolean
+import java.util.concurrent.atomic.AtomicReference
+
+/**
+ * Regression test for the ServiceEcaUtil cache race documented in
+ * plugins/supporting-docs/2026-08-28-testintegration-runtime-and-eca-race-fix.md
+ * and fixed by https://github.com/apache/ofbiz-framework/pull/1805.
+ *
+ * Before that fix, ServiceEcaUtil#mergeEcaDefinitions() mutated a plain
+ * HashMap/LinkedList cache with no synchronization at all between writers
+ * (readConfig()/reloadConfig()/addEcaDefinitions(), racing each other every
+ * time several ServiceDispatchers are constructed at once) and readers
+ * (evalRules(), which runs on essentially every service call and
+ * deliberately stays lock-free). A reader iterating a rule list while a
+ * writer concurrently did remove()-then-add() on that same LinkedList could
+ * observe a corrupted node link and throw a NullPointerException out of
+ * LinkedList$ListItr.next() - exactly the crash seen in 8 unrelated
+ * testIntegration suites once the artificial ECA startup delay was cut.
+ *
+ * This drives addEcaDefinitions() (writers) and evalRules() (a reader)
+ * against the very same service/event concurrently, using duplicate-equal
+ * rules so every write does the racy remove-then-add. Against the pre-fix
+ * code this reliably throws; against the fix (CONFIG_LOCK serializing
+ * writers, plus ConcurrentHashMap/CopyOnWriteArrayList so the lock-free
+ * reader tolerates a concurrent writer) it must not.
+ */
+class ServiceEcaUtilConcurrencyTest {
+
+    private static final int WRITER_THREADS = 8
+    private static final int READER_THREADS = 4
+    private static final int MERGES_PER_WRITER = 3000
+
+    @Test
+    // SEPARATE_THREAD so a genuine hang (e.g. a corrupted, cyclic rule list spinning
+    // evalRules()/mergeEcaDefinitions() forever instead of throwing) still fails this test at
+    // the deadline, rather than blocking until someone kills the build.
+    //
+    // 120s gives generous headroom over CI: all writers serialize on CONFIG_LOCK, so the
+    // 24 000 addEcaDefinitions() calls are effectively single-threaded XML-parsing work that
+    // took ~12s on an idle 10-core dev machine - comfortably longer on a shared/throttled
+    // GitHub Actions runner. This bound exists to catch a genuine hang, not to pace the workload.
+    @Timeout(value = 120, threadMode = Timeout.ThreadMode.SEPARATE_THREAD)
+    void evalRulesToleratesConcurrentAddEcaDefinitions() {
+        String serviceName = "raceRegressionTestService${UUID.randomUUID()}"
+        String eventName = 'raceRegressionTestEvent'
+        String ruleXml = "<service-eca><eca service=\"${serviceName}\" event=\"${eventName}\"/></service-eca>"
+
+        // Overrides of a Java interface's accessor methods; they can't be turned into Groovy
+        // properties without breaking the @Override contract they satisfy.
+        ResourceHandler handler = new ResourceHandler() {
+
+            @Override
+            String getLoaderName() { return 'main' } // codenarc-disable GetterMethodCouldBeProperty
+
+            @Override
+            String getLocation() { return 'ServiceEcaUtilConcurrencyTest-in-memory-secas.xml' } // codenarc-disable GetterMethodCouldBeProperty
+
+            @Override
+            Document getDocument() { return UtilXml.readXmlDocument(ruleXml, false) }
+
+            @Override
+            InputStream getStream() { return null }
+
+            @Override
+            URL getURL() throws GenericConfigException {
+                // No backing resource for this in-memory handler; addEcaDefinitions() catches this
+                // and falls back to getLocation(), same as it does for any resource without a URL.
+                throw new GenericConfigException('no URL for in-memory test resource')
+            }
+
+            @Override
+            boolean isFileResource() { return false }
+
+            @Override
+            String getFullLocation() { return getLocation() } // codenarc-disable GetterMethodCouldBeProperty
+
+        }
+
+        CountDownLatch startLatch = new CountDownLatch(1)
+        AtomicBoolean stopReaders = new AtomicBoolean(false)
+        AtomicReference<Throwable> readerFailure = new AtomicReference<>()
+        AtomicReference<Throwable> writerFailure = new AtomicReference<>()
+
+        List<Thread> readers = (1..READER_THREADS).collect {
+            Thread reader = new Thread({
+                Map<String, Object> context = [:]
+                Map<String, Object> result = [:]
+                startLatch.await()
+                while (!stopReaders.get()) {
+                    try {
+                        ServiceEcaUtil.evalRules(serviceName, null, eventName, null, context, result, false, false)
+                    // Catching Throwable deliberately: a corrupted list under this exact race can throw
+                    // an Error (e.g. StackOverflowError from a cyclic node) as easily as an Exception.
+                    } catch (Throwable t) { // codenarc-disable CatchThrowable
+                        readerFailure.compareAndSet(null, t)
+                        return
+                    }
+                }
+            } as Runnable)
+            reader.daemon = true
+            reader
+        }
+        readers.each { it.start() }
+
+        // Daemon threads: if a corrupted collection ever makes a writer spin forever instead of
+        // throwing, shutdownNow() below can't force a tight, non-interruptible loop to stop, so
+        // non-daemon pool threads would otherwise keep the whole test JVM alive past the timeout.
+        ThreadFactory daemonThreadFactory = { Runnable r ->
+            Thread t = Executors.defaultThreadFactory().newThread(r)
+            t.daemon = true
+            t
+        } as ThreadFactory
+        ExecutorService writers = Executors.newFixedThreadPool(WRITER_THREADS, daemonThreadFactory)
+        try {
+            List<Future<?>> futures = (1..WRITER_THREADS).collect {
+                writers.submit({
+                    startLatch.await()
+                    for (int j = 0; j < MERGES_PER_WRITER; j++) {
+                        try {
+                            ServiceEcaUtil.addEcaDefinitions(handler)
+                        // See the matching note on the reader's catch above.
+                        } catch (Throwable t) { // codenarc-disable CatchThrowable
+                            writerFailure.compareAndSet(null, t)
+                            return
+                        }
+                    }
+                } as Runnable)
+            }
+
+            startLatch.countDown()
+            // See the @Timeout comment above for why 90s: this bound only needs to be well clear
+            // of the observed ~12s local runtime, with room for slower/shared CI hardware.
+            futures.each { it.get(90, TimeUnit.SECONDS) }
+        } finally {
+            writers.shutdownNow()
+            writers.awaitTermination(5, TimeUnit.SECONDS)
+            stopReaders.set(true)
+            readers.each { it.join(5000) }
+        }
+
+        if (writerFailure.get() != null) {
+            Assertions.fail("addEcaDefinitions() threw under concurrent load: ${writerFailure.get()}", writerFailure.get())
+        }
+        if (readerFailure.get() != null) {
+            Assertions.fail("evalRules() threw while racing concurrent addEcaDefinitions(): ${readerFailure.get()}", readerFailure.get())
+        }
+
+        // All WRITER_THREADS * MERGES_PER_WRITER merges loaded content-equal rules for the same
+        // service/event, so they should have collapsed via the remove-old/add-new dedup path down
+        // to exactly one rule - not accumulated duplicates and not lost entirely.
+        List<ServiceEcaRule> finalRules = ServiceEcaUtil.getServiceEventRules(serviceName, eventName)
+        Assertions.assertEquals(1, finalRules?.size(),
+                "Expected exactly one deduplicated rule for ${serviceName}:${eventName}, got: ${finalRules}")
+    }
+
+}