diff --git a/openidm-script/src/test/java/org/forgerock/openidm/script/CustomEndpointFieldProjectionTest.java b/openidm-script/src/test/java/org/forgerock/openidm/script/CustomEndpointFieldProjectionTest.java
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+++ b/openidm-script/src/test/java/org/forgerock/openidm/script/CustomEndpointFieldProjectionTest.java
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+/*
+ * The contents of this file are subject to the terms of the Common Development and
+ * Distribution License (the License). You may not use this file except in compliance with the
+ * License.
+ *
+ * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
+ * specific language governing permission and limitations under the License.
+ *
+ * When distributing Covered Software, include this CDDL Header Notice in each file and include
+ * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
+ * Header, with the fields enclosed by brackets [] replaced by your own identifying
+ * information: "Portions copyright [year] [name of copyright owner]".
+ *
+ * Copyright 2026 3A Systems LLC.
+ */
+
+package org.forgerock.openidm.script;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.forgerock.json.JsonValue.field;
+import static org.forgerock.json.JsonValue.json;
+import static org.forgerock.json.JsonValue.object;
+import static org.forgerock.json.resource.Responses.newResourceResponse;
+
+import org.forgerock.json.JsonValue;
+import org.forgerock.json.resource.AbstractRequestHandler;
+import org.forgerock.json.resource.Connection;
+import org.forgerock.json.resource.ReadRequest;
+import org.forgerock.json.resource.Requests;
+import org.forgerock.json.resource.ResourceException;
+import org.forgerock.json.resource.ResourceResponse;
+import org.forgerock.json.resource.Resources;
+import org.forgerock.services.context.Context;
+import org.forgerock.services.context.RootContext;
+import org.forgerock.util.promise.Promise;
+import org.testng.annotations.Test;
+
+/**
+ * Reproduces the custom-endpoint field-projection bug discussed in
+ * <a href="https://github.com/OpenIdentityPlatform/OpenIDM/discussions/183">discussion #183</a>.
+ *
+ * <p>A custom (scripted) endpoint returns the full object without explicitly setting the
+ * response fields (see {@code ScriptedRequestHandler.evaluate()} which calls
+ * {@code newResourceResponse(id, null, resultJson)} without {@code addField(...)}). As a
+ * consequence the generic CREST field projection in
+ * {@code org.forgerock.json.resource.Resources.filterResource(JsonValue, Collection)} is applied
+ * to the raw result using {@code request.getFields()}.
+ *
+ * <p>That generic projection flattens every requested {@link org.forgerock.json.JsonPointer}
+ * down to its {@code leaf()} name when building the filtered output. When two requested fields
+ * share the same leaf name on different nesting levels (e.g. {@code userName} and
+ * {@code manager/userName}), the nested one overwrites the top-level one, so the top-level
+ * {@code userName} ends up containing the manager's {@code userName}.
+ *
+ * <p>This test asserts the <b>correct</b> behaviour. It therefore <b>fails against the buggy
+ * commons {@code json-resource} (3.1.1-SNAPSHOT)</b> and is expected to pass once the generic
+ * projection is fixed to preserve the pointer structure instead of collapsing to the leaf name.
+ */
+public class CustomEndpointFieldProjectionTest {
+
+    private static final String USER_NAME = "bjensen";
+    private static final String MANAGER_USER_NAME = "jdoe";
+
+    /**
+     * A request handler that mimics a custom scripted endpoint: it returns the full object on
+     * read and does <b>not</b> set the response fields (no {@code addField(...)}), exactly like
+     * {@code ScriptedRequestHandler.evaluate()}.
+     */
+    private static final class FullObjectEndpoint extends AbstractRequestHandler {
+        @Override
+        public Promise<ResourceResponse, ResourceException> handleRead(final Context context,
+                final ReadRequest request) {
+            final JsonValue content = json(object(
+                    field("_id", "user1"),
+                    field("userName", USER_NAME),
+                    field("givenName", "Barbara"),
+                    field("sn", "Jensen"),
+                    field("description", "Example user"),
+                    field("manager", object(
+                            field("_id", "user2"),
+                            field("userName", MANAGER_USER_NAME),
+                            field("givenName", "John"),
+                            field("sn", "Doe")))));
+            return newResourceResponse("user1", null, content).asPromise();
+        }
+    }
+
+    @Test
+    public void topLevelFieldIsNotOverwrittenByNestedFieldWithSameLeafName() throws Exception {
+        final Connection connection =
+                Resources.newInternalConnection(new FullObjectEndpoint());
+
+        // Request the same leaf name on two nesting levels: userName and manager/userName.
+        final ReadRequest request = Requests.newReadRequest("managed/user/user1")
+                .addField("description", "userName", "givenName", "sn", "manager", "manager/userName");
+
+        final ResourceResponse response = connection.read(new RootContext(), request);
+        final JsonValue content = response.getContent();
+
+        // The top-level userName must remain the user's own userName...
+        assertThat(content.get("userName").asString())
+                .as("top-level userName must not be overwritten by manager/userName")
+                .isEqualTo(USER_NAME);
+
+        // ...and the manager's userName must be nested under manager.
+        assertThat(content.get(new org.forgerock.json.JsonPointer("manager/userName")).asString())
+                .as("manager/userName must be projected into the nested manager object")
+                .isEqualTo(MANAGER_USER_NAME);
+    }
+}
+