diff --git a/fleetd/src/test/java/dev/ltms/fleet/FleetdAssemblyTurnRegistrarBehaviouralTest.java b/fleetd/src/test/java/dev/ltms/fleet/FleetdAssemblyTurnRegistrarBehaviouralTest.java
new file mode 100644
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--- /dev/null
+++ b/fleetd/src/test/java/dev/ltms/fleet/FleetdAssemblyTurnRegistrarBehaviouralTest.java
@@ -0,0 +1,184 @@
+package dev.ltms.fleet;
+
+import dev.ltms.fleet.config.ConfigRef;
+import dev.ltms.fleet.config.FleetConfig;
+import dev.ltms.fleet.guard.SubscriptionGuard;
+import dev.ltms.fleet.herdr.AgentStatus;
+import dev.ltms.fleet.herdr.FakeHerdr;
+import dev.ltms.fleet.herdr.HerdrClient;
+import dev.ltms.fleet.inject.Injector;
+import dev.ltms.fleet.inject.TurnListener;
+import dev.ltms.fleet.msg.Rendezvous;
+import dev.ltms.fleet.msg.TurnToken;
+import io.javalin.Javalin;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.lang.reflect.Field;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.LongSupplier;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * fleetd #612 rank 12 — {@code FleetdAssembly} supplies the {@link Injector}'s {@code TurnRegistrar}
+ * with {@code Fleetd.turnRegistrar(completion)}. The normal delivery path cannot distinguish that
+ * registrar from {@code TurnRegistrar.NOOP}: {@link dev.ltms.fleet.inject.CompletionResolver#onDelivered}
+ * registers the same turn shortly afterwards. The distinction matters when a delivery listener throws
+ * after the pane received the message but before normal completion runs. The registrar must already have
+ * registered the waiter with the REAL assembled resolver, so a later completion can still resolve it.
+ *
+ * <p>The test installs a throwing wrapper around the real assembled listener. It does not replace the
+ * registrar or resolver. This constructs the narrow failure condition without a sleep, then observes the
+ * real resolver through {@link FleetdRuntime#completion()}. An inert registrar, or a registrar wired to a
+ * throwaway resolver, leaves this waiter's turn absent from the real resolver and makes the final assertion
+ * fail.
+ */
+class FleetdAssemblyTurnRegistrarBehaviouralTest {
+
+    private static final String TARGET = "term_a";
+
+    private static final class ControllableResourcePorts implements ResourcePorts {
+        final FakeHerdr herdr = new FakeHerdr();
+        final AtomicLong nowNanos = new AtomicLong(1_000_000_000L);
+        Runnable shutdownHook;
+
+        void advanceSeconds(long seconds) {
+            nowNanos.addAndGet(TimeUnit.SECONDS.toNanos(seconds));
+        }
+
+        @Override
+        public Map<String, String> environment() {
+            return Map.of();
+        }
+
+        @Override
+        public HerdrClient connectHerdr(Path socketPath) {
+            return herdr;
+        }
+
+        @Override
+        public Fleetd.AmqpOpener replyInboxOpener() {
+            return (uri, prefetch) -> {
+                throw new UnsupportedOperationException("no broker: block is configured");
+            };
+        }
+
+        @Override
+        public Fleetd.LeadMailboxOpener leadMailboxOpener() {
+            return (uri, selfCoordId, prefetch) -> {
+                throw new UnsupportedOperationException("no coordinator: block is configured");
+            };
+        }
+
+        @Override
+        public LongSupplier nanoClock() {
+            return nowNanos::get;
+        }
+
+        @Override
+        public LongSupplier wallClockNanos() {
+            return nowNanos::get;
+        }
+
+        @Override
+        public ScheduledExecutorService newScheduler(String purpose) {
+            return Executors.newSingleThreadScheduledExecutor();
+        }
+
+        @Override
+        public void addShutdownHook(Runnable hook) {
+            shutdownHook = hook;
+        }
+
+        @Override
+        public void startHttp(Javalin app, String host, int port) {
+            // Do not bind a real port in this assembly test.
+        }
+
+        @Override
+        public Runnable herdrPollWait() {
+            return () -> {
+                throw new UnsupportedOperationException("FakeHerdr is healthy; no poll wait is expected");
+            };
+        }
+    }
+
+    private static FleetConfig writeConfig(Path dir) throws Exception {
+        Path file = dir.resolve("fleetd.yaml");
+        Files.writeString(file, """
+                bind:
+                  host: 127.0.0.1
+                  port: 8765
+                idleSleepGuard:
+                  enabled: false
+                fleet:
+                  leaders:
+                    primary:
+                      tab: "lead: primary"
+                      profile: sonnet
+                profiles:
+                  sonnet:
+                    subscription: true
+                    argv: ["ccs", "sonnet"]
+                """);
+        return FleetConfig.load(file);
+    }
+
+    @Test
+    void realAssembledResolverStillResolvesAfterDeliveredListenerThrows(@TempDir Path dir) throws Exception {
+        FleetConfig cfg = writeConfig(dir);
+        ControllableResourcePorts ports = new ControllableResourcePorts();
+        ports.herdr.withTab("w2", "w2:t7", "lead: primary");
+        FleetdRuntime runtime = FleetdAssembly.assembleAndStart(new AssemblyInputs(cfg,
+                new ConfigRef(dir.resolve("fleetd.yaml"), cfg), new SubscriptionGuard(cfg.guard().hostSet())), ports);
+        try {
+            Injector injector = runtime.injector();
+            installThrowingDeliveredListener(injector);
+
+            CompletableFuture<Rendezvous.Resolution> waiter = new CompletableFuture<>();
+            injector.enqueue(TARGET, "brief", new TurnToken(TARGET, waiter));
+
+            IllegalStateException thrown = assertThrows(IllegalStateException.class,
+                    () -> injector.onStatus(TARGET, AgentStatus.IDLE),
+                    "control: delivery must reach the installed listener and it must throw after delivery");
+            assertTrue(thrown.getMessage().contains("listener failure"), thrown::getMessage);
+
+            ports.herdr.readText("worker report after the listener failure");
+            ports.advanceSeconds(3);
+            runtime.completion().resolveBeforePostAction(TARGET);
+
+            assertTrue(waiter.isDone(),
+                    "FleetdAssembly must wire the Injector registrar to this runtime's real CompletionResolver: "
+                            + "after a delivered listener throws, resolveBeforePostAction must still find and "
+                            + "resolve the registered waiter");
+        } finally {
+            assertTrue(ports.shutdownHook != null, "control: assembly must capture its shutdown hook");
+            ports.shutdownHook.run();
+            assertTrue(ports.herdr.closed, "teardown control: the captured shutdown hook must close herdr");
+        }
+    }
+
+    private static void installThrowingDeliveredListener(Injector injector) throws Exception {
+        Field field = Injector.class.getDeclaredField("turnListener");
+        field.setAccessible(true);
+        field.set(injector, new TurnListener() {
+            @Override
+            public void onTurnComplete(String target) {
+            }
+
+            @Override
+            public void onDelivered(String target, TurnToken token) {
+                throw new IllegalStateException("listener failure after delivery");
+            }
+        });
+    }
+}