Merge CB-564: give every silent failure path a voice

The bridge cannot classify what it never emits. Fleet-health monitoring —
detect a wedged member, decide, escalate — is blocked on that, so this is the
foundation rather than the feature.

A survey of Injector, CompletionResolver, StatusPoller, SessionManager,
SessionReaper and MessageService found six conditions that ended a member's
usefulness while saying nothing useful:

  * Injector.drop()             — worker gone, queue cleared: SILENT
  * CompletionResolver.fail()   — "via turn-stall fallback" at DEBUG, no reason
  * SessionManager.onFailed()   — "session marked failed" at DEBUG, no stage
  * SessionManager.reapIdle()   — indistinguishable from any other release
  * SessionManager.acquire()    — spawn failure rethrown with no log at all
  * MessageService.abandon()    — failed a caller's request at DEBUG

The first two are the exact phrases that misled the CB-560 diagnosis: both name
a symptom and neither names a cause. They are now WARN and carry the reason,
the stage, and the counts.

Conditions already loud were left alone, and so were two by-design timeouts in
MessageService — an async model exists precisely for those, and promoting them
would turn healthy operation into noise.

Behaviour is unchanged: every edit is a log statement.

Merge note: the recycle test deleted by CB-565 conflicted with a test added
here. Resolved by keeping the new onTurnFailed assertion and dropping the
recycle test, which tests a method that no longer exists.

bridged/src/main/java/dev/ltms/bridged/inject/CompletionResolver.java

@@ -214,7 +214,7 @@ public final class CompletionResolver implements TurnListener {
         }
         if (rendezvous.resolveFailure(waiter, reason)) {
             inFlight.remove(target, turn);
-            log.debug("failed send to {} via turn-stall fallback", target);
+            log.warn("failing send to {} via turn-stall fallback: {}", target, reason);
         }
     }
 

bridged/src/main/java/dev/ltms/bridged/inject/Injector.java

@@ -402,6 +402,10 @@ public final class Injector {
             t.awaitingPostTurnPickup = false;
             t.postTurnObserved = false;
         }
+        log.warn("{} is gone, dropping its queue: {} message(s) failed{}; cause: {}", target,
+                pending.size(),
+                hadDeliveredTurn ? " (including one turn already in flight whose completion was never confirmed)" : "",
+                cause.getMessage());
         forget.accept(target); // the worker is gone — clear its readiness/presence too (CB-114)
         for (Pending p : pending) {
             p.delivered().completeExceptionally(cause);

bridged/src/main/java/dev/ltms/bridged/msg/MessageService.java

@@ -277,7 +277,7 @@ public final class MessageService {
         }
         boolean failed = rendezvous.resolveFailure(waiter, reason);
         if (failed) {
-            log.debug("abandoned send to {}: {}", target, reason);
+            log.warn("abandoning the blocked send to {}: {}", target, reason);
         }
         return failed;
     }

bridged/src/main/java/dev/ltms/bridged/session/SessionManager.java

@@ -140,7 +140,13 @@ public final class SessionManager implements TurnListener {
             // to pick the profile out of that role's pool and to label the tab; a role kept only on
             // the MemberSession is recorded after the spawn it was supposed to steer.
             SpawnRequest req = new SpawnRequest(profile, requestedCwd, callerCwd, null, null, memberRole);
-            PeerHandle handle = launcher.spawn(req);
+            PeerHandle handle;
+            try {
+                handle = launcher.spawn(req);
+            } catch (RuntimeException e) {
+                log.warn("spawn failed for profile={} role={}: {}", profile, memberRole, e.getMessage());
+                throw e;
+            }
             String resolvedProfile = resolveProfile(handle, profile);
             String cwd = launcher.effectiveCwd(new SpawnRequest(resolvedProfile, requestedCwd, callerCwd));
             long now = nowNanos.getAsLong();
@@ -312,6 +318,8 @@ public final class SessionManager implements TurnListener {
             worktrees.overlayParity(repoRoot, path, launcher.parityOverlay(preResolvedProfile));
             handle = launcher.spawn(new SpawnRequest(profile, path, callerCwd, null, null, memberRole));
         } catch (RuntimeException e) {
+            log.warn("spawn failed for profile={} role={} branch={} path={}: {}",
+                    preResolvedProfile, memberRole, branch, path, e.getMessage());
             if (path != null) {
                 try {
                     worktrees.remove(repoRoot, path);
@@ -484,8 +492,10 @@ public final class SessionManager implements TurnListener {
         MemberSession current = findByTerminal(target);
         if (current == null) return;
         if (current.state() == MemberSession.State.RELEASED) return;
+        MemberSession.State priorState = current.state();
         if (replace(current, current.withState(MemberSession.State.FAILED))) {
-            log.debug("session marked failed terminal={} pane={}", target, current.paneId());
+            log.warn("member terminal={} pane={} can no longer be delegated to: its turn never resolved "
+                    + "(was {} when it failed)", target, current.paneId(), priorState);
         }
     }
 
@@ -501,7 +511,11 @@ public final class SessionManager implements TurnListener {
             if (s.state() != MemberSession.State.READY && s.state() != MemberSession.State.DONE) {
                 continue;
             }
-            if (now - s.lastActivityAtNanos() > idleTtlNanos) {
+            long idleNanos = now - s.lastActivityAtNanos();
+            if (idleNanos > idleTtlNanos) {
+                log.debug("reaping idle session terminal={} pane={}: idle {}s exceeds the {}s ttl",
+                        s.terminalId(), s.paneId(), TimeUnit.NANOSECONDS.toSeconds(idleNanos),
+                        TimeUnit.NANOSECONDS.toSeconds(idleTtlNanos));
                 release(s.paneId());
                 reaped++;
             }

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;
@@ -298,6 +303,40 @@ 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 rosterReflectsAcquiredMinusReleased() {
         FakeHerdr herdr = new FakeHerdr();