fleetd #209 follow-up: keep roster() off the resolve path

roster() is the supplier for LeadHeartbeatLoop and FleetHealthMonitor
(both timer-driven) and for placement/exhaustion checks and the
metrics scrape — none of which read agentSessionId. Resolving there
meant every tick could open a lazy-resolving adapter's (opencode's)
on-disk session database once per member whose id was still unknown,
with no bound: a member whose id never appears would pay that cost for
the life of the process.

roster() goes back to its pre-#209 behavior (no resolve, no I/O). A
new rosterResolved() carries the resolve logic, and is used only by
the two surfaces that actually report agentSessionId to a caller:
fleet_list (FleetMcp.listFleet) and the REST roster
(FleetApp.listMembers). fleet_whoami's roster().stream() at
FleetMcp.java:768 does not surface the field, so it stays on the plain
roster(). get(paneId) (fleet_status) and the release() resolve are
caller-driven, not timers, and are unchanged.

Retargeted the roster-facing tests from #209 at rosterResolved(), and
added plainRosterDoesNotResolveAgentSessionId, which pins the split by
asserting the handle's agentSessionId() is not called again by
roster().

fleetd/src/main/java/dev/ltms/fleet/mcp/FleetMcp.java

@@ -951,7 +951,10 @@ public final class FleetMcp {
                     .sorted(Map.Entry.comparingByValue())
                     .map(e -> leadView(e.getKey(), e.getValue(), live.get(e.getKey()), selfTerm))
                     .toList();
-            List<MemberSession> roster = sessions.roster();
+            // fleetd #209: this is the caller-driven fleet_list read that actually reports
+            // agentSessionId (via memberCapacityView -> SessionManager.rosterView), so it uses the
+            // resolving roster; the heartbeat/health/metrics timers stay on the plain sessions.roster().
+            List<MemberSession> roster = sessions.rosterResolved();
             List<Map<String, Object>> out = roster.stream()
                     .map(s -> memberCapacityView(s, live.get(s.terminalId()), messages, capacity.clock().getAsLong()))
                     .toList();

fleetd/src/main/java/dev/ltms/fleet/rest/FleetApp.java

@@ -315,7 +315,9 @@ public final class FleetApp {
                 .map(Agent.class::cast)
                 .filter(a -> a.terminalId() != null)
                 .collect(Collectors.toMap(Agent::terminalId, Function.identity(), (_, b) -> b));
-        List<Map<String, Object>> out = sessions.roster().stream()
+        // fleetd #209: this REST roster reports agentSessionId via SessionManager.rosterView, so it
+        // uses the resolving roster read (caller-driven, not a timer) rather than the plain one.
+        List<Map<String, Object>> out = sessions.rosterResolved().stream()
                 .map(s -> SessionManager.rosterView(s, live.get(s.terminalId())))
                 .toList();
         Map<String, Object> body = new LinkedHashMap<>();

fleetd/src/main/java/dev/ltms/fleet/session/MemberSession.java

@@ -89,4 +89,15 @@ public record MemberSession(
         return new MemberSession(paneId, terminalId, profile, role, cwd, ownerTerminal, spawnedAtNanos,
                 nowNanos, turnCount + 1, state, worktree, branch, charterReceipt, agentSessionId);
     }
+
+    /**
+     * Return a copy with {@code agentSessionId} resolved to a non-null value (fleetd #209). Some
+     * adapters (opencode) cannot answer {@link dev.ltms.fleet.peer.PeerHandle#agentSessionId()} at
+     * spawn time — the peer has not persisted its session record yet — so the id is discovered on
+     * a later poll and swapped into the otherwise-immutable session via this wither.
+     */
+    public MemberSession withAgentSessionId(String agentSessionId) {
+        return new MemberSession(paneId, terminalId, profile, role, cwd, ownerTerminal, spawnedAtNanos,
+                lastActivityAtNanos, turnCount, state, worktree, branch, charterReceipt, agentSessionId);
+    }
 }

fleetd/src/main/java/dev/ltms/fleet/session/SessionManager.java

@@ -46,6 +46,15 @@ public final class SessionManager implements TurnListener {
     private final PeerLauncher launcher;
     private final Worktrees worktrees;
     private final ConcurrentHashMap<String /*paneId*/, MemberSession> registry = new ConcurrentHashMap<>();
+    /**
+     * fleetd #209: the live {@link PeerHandle} for every registered pane, retained solely so
+     * {@link #resolveAgentSessionId} can re-poll {@link PeerHandle#agentSessionId()} after spawn.
+     * The handle used to go out of scope at the end of the spawn method, so a launcher that answers
+     * the id lazily (opencode — the on-disk session row is written after the pane is created) could
+     * never be re-asked, and {@code fleet_list}/{@code fleet_spawn resumeSessionId} never saw it.
+     * Populated on every spawn path, removed on {@link #release}.
+     */
+    private final ConcurrentHashMap<String /*paneId*/, PeerHandle> handles = new ConcurrentHashMap<>();
     private final MemberPresence presence;
     private final SecureRandom nonceRandom = new SecureRandom();
     private final AtomicLong nonceSeq = new AtomicLong();
@@ -205,6 +214,7 @@ public final class SessionManager implements TurnListener {
                     handle.charterReceipt(),
                     handle.agentSessionId());
             registry.put(handle.id(), session);
+            handles.put(handle.id(), handle);
             memberLifecycle.acquired(session.role(), session.profile(), session.terminalId());
             log.debug("acquired session id={} terminal={} profile={} owner={}",
                     handle.id(), handle.terminalId(), session.profile(), session.ownerTerminal());
@@ -257,6 +267,10 @@ public final class SessionManager implements TurnListener {
      */
     private void release(String paneId, ReleaseCause cause) {
         MemberSession removed = registry.remove(paneId);
+        // fleetd #209: remove right alongside the registry entry so a released session's handle is
+        // never leaked — but keep the local reference below, so the id can still be resolved for
+        // the ReleaseDetail this teardown notifies with.
+        PeerHandle removedHandle = handles.remove(paneId);
         boolean preserveWorktree = cause == ReleaseCause.SHUTDOWN;
         String snapshotRef = null;
         if (removed != null) {
@@ -303,8 +317,11 @@ public final class SessionManager implements TurnListener {
                 // too, so a failed ticket's detail can point a lead at the same tree to re-dispatch.
                 // CB-584 (issue #65 criterion 5): carry agentSessionId alongside them, so a lead can
                 // also resume the member's conversation, not just re-dispatch onto its files.
-                notifyReleased(new ReleaseDetail(removed.terminalId(), removed.worktree(),
-                        removed.branch(), snapshotRef, removed.agentSessionId()));
+                // fleetd #209: a late-resolving adapter (opencode) may only now have an id — resolve
+                // one last time so a released member's detail carries the id it now has.
+                MemberSession resolved = resolveAgentSessionId(removed, removedHandle);
+                notifyReleased(new ReleaseDetail(resolved.terminalId(), resolved.worktree(),
+                        resolved.branch(), snapshotRef, resolved.agentSessionId()));
             }
         }
         // CB-581: the pane must always stop, even if the dirty check above threw. A session removed
@@ -508,6 +525,7 @@ public final class SessionManager implements TurnListener {
                 handle.charterReceipt(),
                 handle.agentSessionId());
         registry.put(handle.id(), session);
+        handles.put(handle.id(), handle);
         memberLifecycle.acquired(session.role(), session.profile(), session.terminalId());
         log.debug("acquired worktree session id={} terminal={} profile={} branch={} path={}",
                 handle.id(), handle.terminalId(), session.profile(), session.branch(), session.worktree());
@@ -539,16 +557,73 @@ public final class SessionManager implements TurnListener {
         return launcher.defaultProfile();
     }
 
-    /** The session for {@code paneId}, if it is still registered and not released. */
+    /**
+     * The session for {@code paneId}, if it is still registered and not released. fleetd #209:
+     * resolves a still-unknown {@code agentSessionId} against the retained handle before returning,
+     * so {@code fleet_status} sees an id a lazy-resolving adapter has since written.
+     */
     public Optional<MemberSession> get(String paneId) {
-        return Optional.ofNullable(registry.get(paneId));
+        return Optional.ofNullable(registry.get(paneId)).map(this::resolveAgentSessionId);
     }
 
-    /** Fleet-owned roster: all registered sessions (acquired minus released). */
+    /**
+     * Fleet-owned roster: all registered sessions (acquired minus released). Deliberately does
+     * <strong>not</strong> resolve {@code agentSessionId} (fleetd #209 follow-up) — this is the
+     * roster supplier on the heartbeat and health-tick timers ({@code LeadHeartbeatLoop},
+     * {@code FleetHealthMonitor} in {@code Fleetd}), on the placement/exhaustion paths, and on the
+     * metrics scrape ({@code FleetMetrics}), all called far more often than any caller actually
+     * reads {@code agentSessionId}. Resolving here would mean every tick opens a lazy-resolving
+     * adapter's (opencode's) on-disk session store once per member whose id is still unknown — and
+     * for a member whose id never appears, that cost never stops, for the life of the process. Use
+     * {@link #rosterResolved()} instead wherever the id must be current.
+     */
     public List<MemberSession> roster() {
         return List.copyOf(registry.values());
     }
 
+    /**
+     * {@link #roster()}, with each session's still-unknown {@code agentSessionId} re-resolved
+     * against its retained handle (fleetd #209) — so a caller that actually reports the id (
+     * {@code fleet_list}, the REST roster) sees one a lazy-resolving adapter (opencode) has since
+     * written, rather than the null frozen in at spawn time. Reserved for caller-driven reads, not
+     * timers: see {@link #roster()}'s javadoc for why the plain roster must stay non-resolving.
+     */
+    public List<MemberSession> rosterResolved() {
+        return registry.values().stream().map(this::resolveAgentSessionId).toList();
+    }
+
+    /**
+     * Resolve {@code session}'s {@code agentSessionId} if still unknown, re-polling the retained
+     * {@link PeerHandle} for this pane (fleetd #209). A no-op — returning {@code session} unchanged
+     * — once the id is already known, once no handle is retained for this pane (never spawned, or
+     * already released), or if the handle throws while answering. A resolved id is best-effort
+     * CAS-swapped into the registry via {@link #replace}; a lost race just means another caller
+     * already applied the same update, so the resolved value is returned either way.
+     */
+    private MemberSession resolveAgentSessionId(MemberSession session) {
+        return resolveAgentSessionId(session, handles.get(session.paneId()));
+    }
+
+    private MemberSession resolveAgentSessionId(MemberSession session, PeerHandle handle) {
+        if (session.agentSessionId() != null || handle == null) {
+            return session;
+        }
+        String resolved;
+        try {
+            resolved = handle.agentSessionId();
+        } catch (RuntimeException e) {
+            log.debug("agentSessionId lookup failed for pane={} terminal={}: {}",
+                    session.paneId(), session.terminalId(), e.toString());
+            return session;
+        }
+        if (resolved == null) {
+            return session;
+        }
+        MemberSession updated = session.withAgentSessionId(resolved);
+        replace(session, updated); // best-effort; a lost CAS just means the resolved value stands anyway
+        return updated;
+    }
+
     /**
      * CB-304 merged roster+live view. The registry is authoritative for worktree, branch,
      * profile, owner, and state; the optional live agent supplies the herdr-reported status.

fleetd/src/test/java/dev/ltms/fleet/session/SessionManagerTest.java

@@ -931,4 +931,235 @@ class SessionManagerTest {
         assertTrue(e.getMessage().contains("SESSION_RESUME"), e.getMessage());
         assertTrue(e.getMessage().contains("stub-profile"), e.getMessage());
     }
+
+    // ── fleetd #209: agentSessionId resolved lazily against the retained handle ─────────────────
+    //
+    // The opencode adapter cannot answer PeerHandle.agentSessionId() at spawn time — the on-disk
+    // session row is written only after the pane is live — so the id must be re-polled on a LATER
+    // call, against the SAME handle instance the launcher returned at spawn. SessionManager used
+    // to let that handle go out of scope at the end of the spawn method, so no caller ever re-asked
+    // it and fleet_list/fleet_status never saw the id. LazyIdHandle below reproduces exactly that
+    // shape: null on the first N calls (the spawn-time call included), a real id after.
+
+    /**
+     * A {@link PeerHandle} whose {@link #agentSessionId()} answers {@code null} for its first
+     * {@code nullCalls} invocations, then either a fixed id or a configured throw on every call
+     * after that — the shape of the opencode bug (fleetd #209): the session row is not written
+     * until after the pane is live, so early polls come back empty and a later one finds it.
+     */
+    private static final class LazyIdHandle implements PeerHandle {
+        private final String id;
+        private final String terminalId;
+        private final int nullCalls;
+        private final String resolvedId;
+        private final java.util.concurrent.atomic.AtomicInteger calls =
+                new java.util.concurrent.atomic.AtomicInteger();
+        private volatile RuntimeException throwAfter;
+
+        LazyIdHandle(String id, String terminalId, int nullCalls, String resolvedId) {
+            this.id = id;
+            this.terminalId = terminalId;
+            this.nullCalls = nullCalls;
+            this.resolvedId = resolvedId;
+        }
+
+        /** After the null calls are exhausted, throw instead of answering the resolved id. */
+        LazyIdHandle throwing(RuntimeException e) {
+            this.throwAfter = e;
+            return this;
+        }
+
+        @Override
+        public String id() {
+            return id;
+        }
+
+        @Override
+        public String terminalId() {
+            return terminalId;
+        }
+
+        @Override
+        public String agentSessionId() {
+            int n = calls.incrementAndGet();
+            if (n <= nullCalls) {
+                return null;
+            }
+            if (throwAfter != null) {
+                throw throwAfter;
+            }
+            return resolvedId;
+        }
+
+        @Override
+        public CharterReceipt charterReceipt() {
+            return null;
+        }
+
+        int callCount() {
+            return calls.get();
+        }
+    }
+
+    /** A minimal {@link PeerLauncher} that hands out pre-built {@link LazyIdHandle}s, one per spawn. */
+    private static final class LazyIdLauncher implements PeerLauncher {
+        private final java.util.Deque<LazyIdHandle> queued = new java.util.ArrayDeque<>();
+
+        LazyIdLauncher queue(LazyIdHandle handle) {
+            queued.add(handle);
+            return this;
+        }
+
+        @Override
+        public Set<Capability> capabilities() {
+            return Set.of(Capability.WORKTREE, Capability.SESSION_RESUME);
+        }
+
+        @Override
+        public Set<Capability> capabilitiesFor(String profileName) {
+            return capabilities();
+        }
+
+        @Override
+        public PeerHandle spawn(SpawnRequest req) {
+            LazyIdHandle handle = queued.poll();
+            if (handle == null) {
+                throw new IllegalStateException("no queued LazyIdHandle for this spawn");
+            }
+            return handle;
+        }
+
+        @Override
+        public Set<String> profiles() {
+            return Set.of("lazy");
+        }
+
+        @Override
+        public String defaultProfile() {
+            return "lazy";
+        }
+
+        @Override
+        public String effectiveCwd(SpawnRequest req) {
+            return "/cwd";
+        }
+
+        @Override
+        public List<String> parityOverlay(String profileName) {
+            return List.of();
+        }
+
+        @Override
+        public List<?> list() {
+            return List.of();
+        }
+
+        @Override
+        public int reapOrphanWorkers() {
+            return 0;
+        }
+
+        @Override
+        public void stop(String id) {
+        }
+
+        @Override
+        public boolean clearContext(String id) {
+            return false;
+        }
+    }
+
+    @Test
+    void plainRosterDoesNotResolveAgentSessionId() {
+        // fleetd #209 follow-up: roster() sits on the heartbeat/health-tick timers (and the metrics
+        // scrape), so it must never trigger the resolve lookup — for opencode that lookup opens an
+        // on-disk session database, and a member whose id never appears would pay that cost forever.
+        // rosterResolved() is the one to use when a caller actually reports the id.
+        LazyIdHandle handle = new LazyIdHandle("p0", "t0", 1, "oc-session-0");
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+        MemberSession acquired = sessions.acquire("lazy", "/cwd", "/caller", null);
+        assertEquals(1, handle.callCount(), "sanity: only the spawn-time call happened so far");
+
+        List<MemberSession> roster = sessions.roster();
+
+        assertEquals(1, roster.size());
+        assertEquals(acquired.paneId(), roster.getFirst().paneId());
+        assertNull(roster.getFirst().agentSessionId(), "the plain roster must not resolve the id");
+        assertEquals(1, handle.callCount(),
+                "roster() must never call agentSessionId() again — it sits on the heartbeat/health timers");
+    }
+
+    @Test
+    void rosterResolvedResolvesALateAgentSessionIdFromTheRetainedHandle() {
+        LazyIdHandle handle = new LazyIdHandle("p1", "t1", 1, "oc-session-1");
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+
+        MemberSession acquired = sessions.acquire("lazy", "/cwd", "/caller", null);
+        assertNull(acquired.agentSessionId(),
+                "opencode has not written its session row yet at spawn time");
+
+        List<MemberSession> roster = sessions.rosterResolved();
+        assertEquals(1, roster.size());
+        assertEquals("oc-session-1", roster.getFirst().agentSessionId(),
+                "fleet_list must see the id once the adapter can answer it");
+
+        Map<String, Object> view = SessionManager.rosterView(roster.getFirst(), null);
+        assertEquals("oc-session-1", view.get("agentSessionId"),
+                "rosterView renders whatever rosterResolved() resolved");
+    }
+
+    @Test
+    void getResolvesALateAgentSessionIdFromTheRetainedHandle() {
+        LazyIdHandle handle = new LazyIdHandle("p2", "t2", 1, "oc-session-2");
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+        MemberSession acquired = sessions.acquire("lazy", "/cwd", "/caller", null);
+
+        MemberSession resolved = sessions.get(acquired.paneId()).orElseThrow();
+
+        assertEquals("oc-session-2", resolved.agentSessionId(),
+                "fleet_status (single-session lookup) must also see the late-resolved id");
+    }
+
+    @Test
+    void releaseCarriesALateResolvedAgentSessionIdIntoTheReleaseDetail() {
+        LazyIdHandle handle = new LazyIdHandle("p3", "t3", 1, "oc-session-3");
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+        MemberSession acquired = sessions.acquire("lazy", "/cwd", "/caller", null);
+        java.util.List<String> released = new java.util.concurrent.CopyOnWriteArrayList<>();
+        sessions.onRelease(detail -> released.add(detail.agentSessionId()));
+
+        sessions.release(acquired.paneId());
+
+        assertEquals(java.util.List.of("oc-session-3"), released,
+                "a released member's detail carries the id it has since resolved, not the null "
+                        + "frozen in at spawn time");
+    }
+
+    @Test
+    void aThrowingHandleDoesNotBreakRosterResolved() {
+        LazyIdHandle handle = new LazyIdHandle("p4", "t4", 1, "oc-session-4")
+                .throwing(new RuntimeException("sqlite locked"));
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+        sessions.acquire("lazy", "/cwd", "/caller", null);
+
+        List<MemberSession> roster = assertDoesNotThrow(sessions::rosterResolved,
+                "a handle that throws resolving its id must not break the roster read");
+
+        assertEquals(1, roster.size());
+        assertNull(roster.getFirst().agentSessionId(), "the id stays unresolved when the lookup throws");
+    }
+
+    @Test
+    void aResolvedAgentSessionIdIsNotLookedUpAgain() {
+        LazyIdHandle handle = new LazyIdHandle("p5", "t5", 1, "oc-session-5");
+        SessionManager sessions = new SessionManager(new LazyIdLauncher().queue(handle));
+        sessions.acquire("lazy", "/cwd", "/caller", null);
+        assertEquals(1, handle.callCount(), "sanity: only the spawn-time call happened so far");
+
+        sessions.rosterResolved();
+        assertEquals(2, handle.callCount(), "the first rosterResolved() read resolves the id");
+
+        sessions.rosterResolved();
+        assertEquals(2, handle.callCount(), "once resolved, the id must not be looked up again");
+    }
 }