CB-564: give a voice to silent member-failure paths

Injector.drop, CompletionResolver.fail, SessionManager.onFailed/reapIdle/
acquire spawn failures, and MessageService.abandon used to fail a member
or a caller's request with no log, a bare DEBUG, or a log that named only
the symptom ("session marked failed", "failed send via turn-stall
fallback"). Each now logs at WARN and names the real cause and the
numbers involved. Observability only — no behaviour changed.

bridged/src/test/java/dev/ltms/bridged/inject/CompletionResolverTest.java

@@ -1,9 +1,14 @@
 package dev.ltms.bridged.inject;
 
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
 import dev.ltms.bridged.herdr.AgentControl;
 import dev.ltms.bridged.herdr.FakeHerdr;
 import dev.ltms.bridged.msg.Rendezvous;
 import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -270,6 +275,40 @@ class CompletionResolverTest {
         assertEquals("stuck on an error screen", waiter.getNow(null).text());
     }
 
+    @Test
+    void failIsLoggedAtWarnWithTheReason() {
+        // CB-564: this used to be a bare DEBUG "failed send to X via turn-stall fallback" — a symptom
+        // with no cause, and below the level anyone watching for member health would see. A fail that
+        // resolves a caller's blocked send is at least WARN and must carry the reason.
+        LoggerContext ctx = (LoggerContext) LoggerFactory.getILoggerFactory();
+        ch.qos.logback.classic.Logger resolverLog =
+                (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(CompletionResolver.class);
+        ListAppender<ILoggingEvent> appender = new ListAppender<>();
+        appender.setContext(ctx);
+        appender.start();
+        resolverLog.addAppender(appender);
+        resolverLog.setLevel(Level.WARN);
+        try {
+            FakeHerdr herdr = new FakeHerdr().readText("stuck on an error screen");
+            Rendezvous rendezvous = new Rendezvous();
+            CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous);
+            var waiter = rendezvous.open("term_a");
+
+            resolver.fail("term_a", null);
+
+            String warn = appender.list.stream()
+                    .filter(e -> e.getLevel().equals(Level.WARN))
+                    .map(ILoggingEvent::getFormattedMessage)
+                    .findFirst()
+                    .orElse("no turn-stall WARN logged");
+            assertTrue(warn.contains("term_a"), "the log names the target: " + warn);
+            assertTrue(warn.contains("stuck on an error screen"), "the log carries the reason: " + warn);
+            assertTrue(waiter.isDone());
+        } finally {
+            resolverLog.detachAppender(appender);
+        }
+    }
+
     // --- CB-116 waiter identity: a late completion never crosses into the next turn ---------
 
     @Test

bridged/src/test/java/dev/ltms/bridged/inject/InjectorTest.java

@@ -436,6 +436,38 @@ class InjectorTest {
         assertEquals(List.of(T), forgotten, "drop clears the gone worker's presence");
     }
 
+    @Test
+    void dropIsLogged() {
+        // CB-564: a vanished worker used to drop its queue with no log at all — the only trace was
+        // whatever failed downstream (e.g. a caller's send timing out with no clue why). Assert the
+        // drop itself now names the cause and the number of messages it failed.
+        LoggerContext ctx = (LoggerContext) LoggerFactory.getILoggerFactory();
+        ch.qos.logback.classic.Logger injectorLog =
+                (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(Injector.class);
+        ListAppender<ILoggingEvent> appender = new ListAppender<>();
+        appender.setContext(ctx);
+        appender.start();
+        injectorLog.addAppender(appender);
+        injectorLog.setLevel(Level.WARN);
+        try {
+            Injector inj = new Injector(new AgentControl(herdr), TurnListener.NOOP, _ -> true, _ -> {
+            });
+            inj.enqueue(T, "orphan");
+            inj.drop(T, new HerdrException("worker gone", "pane_not_found", null));
+
+            String warn = appender.list.stream()
+                    .filter(e -> e.getLevel().equals(Level.WARN))
+                    .map(ILoggingEvent::getFormattedMessage)
+                    .findFirst()
+                    .orElse("no drop WARN logged");
+            assertTrue(warn.contains(T), "the log names the target terminal: " + warn);
+            assertTrue(warn.contains("1 message"), "the log carries the failed message count: " + warn);
+            assertTrue(warn.contains("worker gone"), "the log carries the real cause: " + warn);
+        } finally {
+            injectorLog.detachAppender(appender);
+        }
+    }
+
     @Test
     void pollerDeliversToAnIdleWorker() throws Exception {
         // End-to-end through the poller: idle worker → message delivered without manual onStatus.

bridged/src/test/java/dev/ltms/bridged/session/SessionManagerTest.java

@@ -1,5 +1,9 @@
 package dev.ltms.bridged.session;
 
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
 import dev.ltms.bridged.config.BridgedConfig;
 import dev.ltms.bridged.guard.SubscriptionGuard;
 import dev.ltms.bridged.herdr.AgentControl;
@@ -8,6 +12,7 @@ import dev.ltms.bridged.herdr.WorkspaceControl;
 import dev.ltms.bridged.member.ClaudeCodeLauncher;
 import dev.ltms.bridged.peer.PeerUnreachableException;
 import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 
 import java.util.List;
 import java.util.Map;
@@ -157,6 +162,41 @@ class SessionManagerTest {
         assertTrue(sessions.roster().contains(updated), "FAILED is still in acquired-minus-released roster");
     }
 
+    @Test
+    void onTurnFailedIsLoggedAtWarnWithThePriorState() {
+        // CB-564: this transition used to be a bare DEBUG "session marked failed" — a symptom with no
+        // cause. A member that can no longer be delegated to must be at least WARN, and should name
+        // what stage it failed at (here: BUSY, i.e. a turn was in flight and never resolved).
+        LoggerContext ctx = (LoggerContext) LoggerFactory.getILoggerFactory();
+        ch.qos.logback.classic.Logger sessionLog =
+                (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(SessionManager.class);
+        ListAppender<ILoggingEvent> appender = new ListAppender<>();
+        appender.setContext(ctx);
+        appender.start();
+        sessionLog.addAppender(appender);
+        sessionLog.setLevel(Level.WARN);
+        try {
+            FakeHerdr herdr = new FakeHerdr();
+            SessionManager sessions = sessionManager(herdr);
+            MemberSession session = sessions.acquire("ltms-local", null, "/caller", "term_primary");
+            String terminal = session.terminalId();
+            sessions.asPresence().markPresent(terminal);
+            sessions.onDelivered(terminal);
+
+            sessions.onTurnFailed(terminal);
+
+            String warn = appender.list.stream()
+                    .filter(e -> e.getLevel().equals(Level.WARN))
+                    .map(ILoggingEvent::getFormattedMessage)
+                    .findFirst()
+                    .orElse("no turn-failed WARN logged");
+            assertTrue(warn.contains(terminal), "the log names the member: " + warn);
+            assertTrue(warn.contains("BUSY"), "the log names the stage it failed at: " + warn);
+        } finally {
+            sessionLog.detachAppender(appender);
+        }
+    }
+
     @Test
     void recycleProducesNewPaneIdAndOldOneIsGone() {
         FakeHerdr herdr = new FakeHerdr();