#315: fix self-contradicting javadoc left by the previous commit

FixedPlacementPolicy's class javadoc still opened with "This ignores caps
and reachability" after the previous commit added reachability as the
fourth carve-out that is explicitly NOT ignored — caught by a shape-check
survey run against this same file as part of #315's own request ("look in
placement/ ... for the same shape: a caller/comment that documents an
expectation ... where an implementation does not meet it"). Reworded the
opening sentence: fixed still ignores caps (maxLoad) by design, but
reachability is now a narrower, per-call retry exclusion, not an ignored
concern.

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

@@ -22,6 +22,7 @@ import dev.ltms.fleet.placement.BackendQuarantine;
 import dev.ltms.fleet.placement.PlacementException;
 import dev.ltms.fleet.session.SessionManager;
 import dev.ltms.fleet.session.MemberSession;
+import dev.ltms.fleet.session.ShuttingDownException;
 import dev.ltms.fleet.session.WorktreeRequest;
 import dev.ltms.fleet.peer.MemberRole;
 import dev.ltms.fleet.peer.PeerLauncher;
@@ -962,6 +963,10 @@ public final class FleetMcp {
             return text(json(memberView(member)));
         } catch (GuardException e) {
             return error("subscription boundary: " + e.getMessage());
+        } catch (ShuttingDownException e) {
+            // fleetd #308: the daemon's shutdown drain has already started — refuse loudly rather
+            // than register a session drainAll will never see again.
+            return error("shutting down: " + e.getMessage());
         } catch (PlacementException e) {
             // CB-599: no candidate had capacity (maxLoad, quarantine, or all-exhausted) — distinct
             // from "profile does not exist" below.

fleetd/src/main/java/dev/ltms/fleet/member/CompositePeerLauncher.java

@@ -385,9 +385,12 @@ public final class CompositePeerLauncher implements PeerLauncher {
             }
         }
 
+        // unreachable.size() counts DISTINCT profiles, not attempts (a HashSet dedupes a profile
+        // added twice) — say "distinct" so the count matches the sentence and the profile list that
+        // follows, rather than reading as a count of attempts made (fleetd #315).
         throw new PeerUnreachableException(
                 "no reachable worker profile available after trying " + unreachable.size()
-                        + " candidate(s): " + String.join(", ", unreachable));
+                        + " distinct candidate(s): " + String.join(", ", unreachable));
     }
 
     /**

fleetd/src/main/java/dev/ltms/fleet/placement/FixedPlacementPolicy.java

@@ -5,10 +5,14 @@ import java.util.List;
 
 /**
  * Backward-compatible placement: an unqualified spawn always resolves to the configured default
- * profile, exactly as {@code CompositePeerLauncher} did before CB-518. This ignores caps and
- * reachability so that a pre-existing config behaves identically after upgrade.
+ * profile, exactly as {@code CompositePeerLauncher} did before CB-518. This ignores caps
+ * ({@code maxLoad}) so that a pre-existing config behaves identically after upgrade — capacity
+ * gating for automatic placement is deliberately out of scope for {@code fixed}, exactly as it
+ * always has been. Reachability is a narrower exception (fleetd #315, below): a profile is never
+ * checked for reachability up front, only skipped once it has already failed in <em>this same</em>
+ * spawn call's retry loop — see the unreachable case below.
  *
- * <p>Three exceptions walk past the default instead of returning it unconditionally:
+ * <p>Four exceptions walk past the default instead of returning it unconditionally:
  * <ul>
  *   <li>Quarantine (CB-578 stage B): a quarantined default is a credential that just refused on
  *       a usage limit, not a transient capacity or reachability concern.
@@ -16,13 +20,21 @@ import java.util.List;
  *       ({@code BackendOutagePolicy}) — a separate, shorter-lived source from quarantine. When a
  *       profile is both quarantined and cooling off, only the quarantine reason is reported
  *       (exhaustion takes priority), matching {@code CompositePeerLauncher}'s explicit-spawn order.
+ *   <li>Unreachable (fleetd #315): {@code CompositePeerLauncher.spawn} retries a failed candidate
+ *       on the next one and rebuilds the {@link PlacementContext} so {@code ctx.unreachable()}
+ *       names every profile that already failed with {@code PeerUnreachableException} in this same
+ *       call. Without this check {@code select} kept handing back the same dead default forever —
+ *       the retry loop's own comment says "so the policy excludes this profile", and this is what
+ *       makes that true for {@code fixed} too, matching {@code weighted}/{@code round-robin}
+ *       (both filter on {@code ctx.unreachable()} via {@link PlacementPolicyUtil#available}).
  *   <li>Weight 0 (CB-554): {@code fixed} is still automatic selection, so a profile the operator
  *       marked "never auto-select me" ({@code weight <= 0}) must be skipped here exactly as
  *       {@code weighted}/{@code round-robin} skip it — an explicit {@code fleet_spawn} naming
  *       the profile is unaffected, only this automatic fallback walk.
  * </ul>
- * A fleet where nothing is ever quarantined, cooling off, or weight-0 never exercises any of these
- * paths, so today's behaviour is unchanged.
+ * A fleet where nothing is ever quarantined, cooling off, unreachable, or weight-0 never exercises
+ * any of these paths, so today's behaviour is unchanged — in particular, the very first selection
+ * of a spawn call always sees an empty {@code unreachable} set, so the first choice is untouched.
  */
 final class FixedPlacementPolicy implements PlacementPolicy {
 
@@ -30,12 +42,12 @@ final class FixedPlacementPolicy implements PlacementPolicy {
     public PlacementCandidate select(PlacementContext ctx) {
         String d = ctx.defaultProfile();
         if (d != null && !d.isBlank() && !ctx.quarantined().contains(d) && !ctx.coolingOff().contains(d)
-                && !weightExcluded(ctx, d)) {
+                && !ctx.unreachable().contains(d) && !weightExcluded(ctx, d)) {
             return new PlacementCandidate(d, null, 1.0f, null);
         }
         for (PlacementCandidate c : ctx.candidates()) {
             if (!ctx.quarantined().contains(c.profile()) && !ctx.coolingOff().contains(c.profile())
-                    && !c.excluded()) {
+                    && !ctx.unreachable().contains(c.profile()) && !c.excluded()) {
                 return new PlacementCandidate(c.profile(), null, c.weight(), c.maxLoad());
             }
         }
@@ -44,8 +56,9 @@ final class FixedPlacementPolicy implements PlacementPolicy {
             // Exhaustion quarantine takes priority: reported only when quarantine is absent, so the
             // message never claims "cooling off" for a profile that is really backend-exhausted.
             boolean dCoolingOff = !dQuarantined && ctx.coolingOff().contains(d);
+            boolean dUnreachable = ctx.unreachable().contains(d);
             boolean dWeightExcluded = weightExcluded(ctx, d);
-            if (dQuarantined || dCoolingOff || dWeightExcluded) {
+            if (dQuarantined || dCoolingOff || dUnreachable || dWeightExcluded) {
                 List<String> reasons = new ArrayList<>();
                 if (dQuarantined) {
                     reasons.add("is quarantined (backend exhausted)");
@@ -53,6 +66,9 @@ final class FixedPlacementPolicy implements PlacementPolicy {
                 if (dCoolingOff) {
                     reasons.add("is cooling off after repeated backend errors");
                 }
+                if (dUnreachable) {
+                    reasons.add("is unreachable");
+                }
                 if (dWeightExcluded) {
                     reasons.add("has weight 0 (excluded from automatic selection)");
                 }
@@ -62,7 +78,7 @@ final class FixedPlacementPolicy implements PlacementPolicy {
         }
         if (!ctx.candidates().isEmpty()) {
             throw new PlacementException("all worker profiles are excluded from automatic "
-                    + "selection (quarantined, cooling off, or weight-0)");
+                    + "selection (quarantined, cooling off, unreachable, or weight-0)");
         }
         throw new PlacementException("no worker profiles configured");
     }

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

@@ -19,6 +19,7 @@ import dev.ltms.fleet.peer.PeerUnreachableException;
 import dev.ltms.fleet.placement.PlacementException;
 import dev.ltms.fleet.msg.MessageService;
 import dev.ltms.fleet.session.SessionManager;
+import dev.ltms.fleet.session.ShuttingDownException;
 import dev.ltms.fleet.peer.MemberRole;
 import dev.ltms.fleet.session.MemberSession;
 import dev.ltms.fleet.session.WorktreeRequest;
@@ -501,6 +502,11 @@ public final class FleetApp {
             ctx.status(201).json(view(member));
         } catch (GuardException e) {
             ctx.status(403).json(Map.of("error", "subscription_boundary", "detail", e.getMessage()));
+        } catch (ShuttingDownException e) {
+            // fleetd #308: the daemon's shutdown drain has already started — 503, not a bare 500,
+            // so this reads the same as PlacementException below: valid request, refused because
+            // of a transient daemon state rather than a bad argument.
+            ctx.status(503).json(Map.of("error", "shutting_down", "detail", e.getMessage()));
         } catch (PlacementException e) {
             // CB-599: no candidate had capacity (maxLoad, quarantine, or all-exhausted) — a benign,
             // likely-transient refusal, distinct from "profile does not exist" below. 503: the

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

@@ -93,6 +93,9 @@ public final class GitWorktrees implements Worktrees {
     /** OS group name for {@link #shareWithGroup} (fleetd #185 stage 3); {@code null} ⇒ feature off. */
     private final String group;
     private final Consumer<String> afterWorktreeAdded;
+    /** How the initial {@code git worktree add} command runs. Package-private test seam for an
+     *  interrupted command after Git has made worktree state. */
+    private final Function<String[], String> worktreeAddRunner;
     /** How {@link #shareWithGroup}'s processes (git config / chgrp / chmod / find) actually run.
      *  Defaults to the real {@link #exec(String...)}. Package-private test seam so a unit test can
      *  prove "no group configured ⇒ zero processes spawned" and inspect exactly what a configured
@@ -132,7 +135,13 @@ public final class GitWorktrees implements Worktrees {
 
     /** Test seam combining a configurable {@code group} with {@link #afterWorktreeAdded}. */
     GitWorktrees(String configuredRoot, String group, Consumer<String> afterWorktreeAdded) {
-        this(configuredRoot, group, afterWorktreeAdded, null);
+        this(configuredRoot, group, afterWorktreeAdded, null, null);
+    }
+
+    /** Test seam for changing how {@link #shareWithGroup}'s processes run. */
+    GitWorktrees(String configuredRoot, String group, Consumer<String> afterWorktreeAdded,
+                  Function<String[], String> shareGroupRunner) {
+        this(configuredRoot, group, afterWorktreeAdded, shareGroupRunner, null);
     }
 
     /**
@@ -141,13 +150,15 @@ public final class GitWorktrees implements Worktrees {
      * exactly what commands a configured group runs, without a real second OS user/group.
      *
      * @param shareGroupRunner {@code null} ⇒ the real {@link #exec(String...)}.
+     * @param worktreeAddRunner {@code null} ⇒ the real {@link #exec(String...)}.
      */
     GitWorktrees(String configuredRoot, String group, Consumer<String> afterWorktreeAdded,
-                 Function<String[], String> shareGroupRunner) {
+                  Function<String[], String> shareGroupRunner, Function<String[], String> worktreeAddRunner) {
         this.configuredRoot = configuredRoot;
         this.group = (group == null || group.isBlank()) ? null : group;
         this.afterWorktreeAdded = afterWorktreeAdded == null ? _ -> {} : afterWorktreeAdded;
         this.shareGroupRunner = shareGroupRunner != null ? shareGroupRunner : this::exec;
+        this.worktreeAddRunner = worktreeAddRunner != null ? worktreeAddRunner : this::exec;
     }
 
     @Override
@@ -166,8 +177,8 @@ public final class GitWorktrees implements Worktrees {
         String wt = path.toAbsolutePath().toString();
         log.info("adding worktree branch={} path={} base={}", branch, wt, base);
         removeUserInfoFromHttpsOrigin(repoRoot);
-        exec("git", "-C", repoRoot, "worktree", "add", wt, "-b", branch, base);
         try {
+            worktreeAddRunner.apply(new String[] {"git", "-C", repoRoot, "worktree", "add", wt, "-b", branch, base});
             afterWorktreeAdded.accept(wt);
             requireCredentialFreeHttpsOrigin(wt);
             configureEnvironmentCredentialHelper(repoRoot, wt);
@@ -181,10 +192,11 @@ public final class GitWorktrees implements Worktrees {
     }
 
     /**
-     * {@code add()} has already created the worktree and its branch by the time any step from
-     * {@link #afterWorktreeAdded} through {@link #isolateToolSurface} can throw — including
+     * {@code git worktree add} may have created the worktree and its branch by the time it, or any
+     * later step through {@link #isolateToolSurface}, throws. This includes
      * {@link #requireCredentialFreeHttpsOrigin}, an intended security refusal, not only an IO
-     * accident. Without this, {@code add()} never returns, so its caller
+     * accident. A Git-reported {@code worktree add} failure usually creates nothing, but an
+     * interrupted command can leave partial state. Without cleanup, {@code add()} never returns, so its caller
      * ({@code SessionManager#acquireWithWorktree}) never receives a path to register or clean up:
      * its local {@code path} stays null, the {@code if (path != null)} guard in its own catch block
      * never runs, and the worktree directory and branch leak on disk forever with nothing tracking
@@ -204,6 +216,10 @@ public final class GitWorktrees implements Worktrees {
      * used in {@code SessionManager#acquireWithWorktree}'s own catch block.
      */
     private void cleanupAfterAddFailure(String repoRoot, String worktreePath, String branch, RuntimeException original) {
+        if (!Files.exists(Path.of(worktreePath))) {
+            log.debug("provisioning failed before worktree {} existed; nothing to clean up", worktreePath);
+            return;
+        }
         log.warn("provisioning failed for branch={} path={}: {} — cleaning up before rethrowing",
                 branch, worktreePath, original.getMessage());
         try {

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

@@ -21,6 +21,7 @@ import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Consumer;
 import java.util.function.LongSupplier;
@@ -61,6 +62,8 @@ public final class SessionManager implements TurnListener {
     private final LongSupplier nowNanos;
     private final int contextCap;
     private final boolean clearAfterTurn;
+    /** Null in production; test seam for the interval before an idle session's conditional release. */
+    private final Consumer<MemberSession> beforeIdleRelease;
     private volatile MemberLifecycle memberLifecycle = MemberLifecycle.NONE;
     /**
      * CB-586: the repo root the fleet actually works in, remembered the first time a worktree
@@ -71,6 +74,16 @@ public final class SessionManager implements TurnListener {
      */
     private volatile String fleetRepoRoot;
 
+    /**
+     * fleetd #308: flips true the instant {@link #drainAll} starts, before its registry snapshot
+     * is even taken — so a spawn already in flight sees the refusal as early as a plain flag can
+     * make it. This alone cannot close the race completely: a caller that read {@code false} just
+     * before the flip can still land in the registry after the snapshot. {@link #drainAll}'s
+     * post-loop sweep is what catches that straggler; the two mechanisms are deliberately paired,
+     * see {@link #drainAll}'s javadoc.
+     */
+    private final AtomicBoolean draining = new AtomicBoolean(false);
+
     /** CB-520: notified with a terminalId on every acquire; no-op until wired. */
     private final List<Consumer<String>> acquireListeners = new java.util.concurrent.CopyOnWriteArrayList<>();
     /** CB-516: notified with a {@link ReleaseDetail} on every release; no-op until wired. */
@@ -102,13 +115,23 @@ public final class SessionManager implements TurnListener {
     }
 
     public SessionManager(PeerLauncher launcher, Worktrees worktrees, LongSupplier nowNanos,
-                          int contextCap, boolean clearAfterTurn) {
+                           int contextCap, boolean clearAfterTurn) {
+        this(launcher, worktrees, nowNanos, contextCap, clearAfterTurn, null);
+    }
+
+    /**
+     * Package-private constructor for a deterministic reap/delivery race test. Production callers
+     * use the constructor above, whose null hook adds no callback or lock to an ordinary reap.
+     */
+    SessionManager(PeerLauncher launcher, Worktrees worktrees, LongSupplier nowNanos,
+                   int contextCap, boolean clearAfterTurn, Consumer<MemberSession> beforeIdleRelease) {
         this.launcher = launcher;
         this.worktrees = worktrees;
         this.presence = new PresenceFleet(this);
         this.nowNanos = nowNanos;
         this.contextCap = contextCap;
         this.clearAfterTurn = clearAfterTurn;
+        this.beforeIdleRelease = beforeIdleRelease;
     }
 
     /**
@@ -181,6 +204,14 @@ public final class SessionManager implements TurnListener {
     public MemberSession acquire(String profile, MemberRole role, String requestedCwd, String callerCwd,
                                  String ownerTerminal, WorktreeRequest wt,
                                  String sessionName, String resumeSessionId) {
+        // fleetd #308: refuse before anything else runs — no slot reservation, no launcher spawn —
+        // so a caller learns the daemon is going down instead of getting a session drainAll will
+        // never see again. Checked here because every other acquire(...) overload delegates to
+        // this one, so this is the single point every spawn path passes through.
+        if (draining.get()) {
+            throw new ShuttingDownException("fleetd is shutting down; refusing to spawn a session "
+                    + "the shutdown drain would never see");
+        }
         MemberRole memberRole = (role == null) ? MemberRole.DEV : role;
         requireResumeCapability(profile, resumeSessionId);
         // CB-619 / fleetd #123: an explicit profile bypasses placement (CompositePeerLauncher only
@@ -272,10 +303,32 @@ public final class SessionManager implements TurnListener {
      */
     private void release(String paneId, ReleaseCause cause) {
         MemberSession removed = registry.remove(paneId);
+        releaseRemoved(paneId, removed, handles.remove(paneId), cause);
+    }
+
+    /**
+     * Tear a session down only while {@code expected} is still its registry value. A lifecycle
+     * transition replaces the immutable record, so this prevents a reap based on an old READY or
+     * DONE record from stopping a worker that delivery has made BUSY.
+     */
+    private boolean releaseIfCurrent(MemberSession expected, ReleaseCause cause) {
+        if (!registry.remove(expected.paneId(), expected)) {
+            // A lifecycle transition replaced the record between the caller's check and this remove.
+            // Log it: this race is by definition unobservable otherwise, and a reaper that silently
+            // declines to reap is the hardest kind of behaviour to diagnose after the fact.
+            log.debug("skipping reap of pane={}: its registry record changed after the idle check "
+                    + "(most likely a delivery made it BUSY)", expected.paneId());
+            return false;
+        }
+        releaseRemoved(expected.paneId(), expected, handles.remove(expected.paneId()), cause);
+        return true;
+    }
+
+    private void releaseRemoved(String paneId, MemberSession removed, PeerHandle removedHandle,
+                                ReleaseCause cause) {
         // 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) {
@@ -846,14 +899,18 @@ public final class SessionManager implements TurnListener {
             }
             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));
                 // CB-581: one session that fails to release must not abort the whole reaping pass —
                 // match drainAll's per-session try/catch so the rest of the roster still gets reaped.
                 try {
-                    release(s.paneId());
-                    reaped++;
+                    if (beforeIdleRelease != null) {
+                        beforeIdleRelease.accept(s);
+                    }
+                    if (releaseIfCurrent(s, ReleaseCause.COMPLETED)) {
+                        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));
+                        reaped++;
+                    }
                 } catch (RuntimeException e) {
                     log.warn("reap failed for pane={} terminal={} worktree={}; continuing with "
                             + "remaining sessions", s.paneId(), s.terminalId(), s.worktree(), e);
@@ -884,10 +941,40 @@ public final class SessionManager implements TurnListener {
      * a reason to delete a worker's only copy of its uncommitted work. A session still {@code BUSY}
      * when the timeout expired is abandoned mid-turn and logged loudly so an operator can find its
      * kept worktree.
+     *
+     * <p>fleetd #308: {@code roster()} is a one-shot snapshot (see its javadoc), and nothing used
+     * to stop a new session from registering after it was taken — {@link #acquire} stayed open for
+     * as long as this drain waited on a {@code BUSY} session, up to the whole {@code timeoutNanos}
+     * budget. Two things close that window, deliberately paired because neither alone is complete:
+     * {@link #draining} is flipped true before the snapshot is even taken, so {@link #acquire}
+     * refuses (invariant 3: loudly, via {@link ShuttingDownException}) as much of the window as a
+     * plain flag can close; and the sweep below re-reads the registry once the initial snapshot has
+     * fully drained and drains whatever a straggler — a caller that read the flag as {@code false}
+     * a moment before it flipped — still managed to register. The sweep shares the same
+     * {@code deadline} rather than getting its own: {@code timeoutNanos} is a budget for the WHOLE
+     * drain (see above), and a straggler must not buy the drain more time than the flag it lost the
+     * race against would have. In the ordinary case the sweep finds nothing and costs one empty
+     * {@link #roster()} call.
      */
     void drainAll(long timeoutNanos) {
         long deadline = System.nanoTime() + timeoutNanos;
-        for (MemberSession s : roster()) {
+        draining.set(true);
+        drainSnapshot(roster(), deadline);
+        List<MemberSession> stragglers = roster();
+        if (!stragglers.isEmpty()) {
+            log.warn("drain sweep found {} session(s) registered after the drain snapshot was "
+                    + "taken (raced past the shutdown guard); draining them too", stragglers.size());
+            drainSnapshot(stragglers, deadline);
+        }
+    }
+
+    /**
+     * Drain exactly the sessions in {@code snapshot}, waiting out a {@code BUSY} one against the
+     * shared whole-drain {@code deadline} before releasing it. Shared by {@link #drainAll}'s main
+     * pass and its post-loop straggler sweep (fleetd #308) so both honor the same one budget.
+     */
+    private void drainSnapshot(List<MemberSession> snapshot, long deadline) {
+        for (MemberSession s : snapshot) {
             try {
                 if (s.state() == MemberSession.State.BUSY) {
                     while (System.nanoTime() < deadline) {

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

@@ -0,0 +1,18 @@
+package dev.ltms.fleet.session;
+
+/**
+ * Thrown by {@link SessionManager#acquire} when a spawn is requested after the daemon's shutdown
+ * drain has already begun (fleetd #308).
+ *
+ * <p>{@link SessionManager#drainAll} snapshots the registry once and tears down exactly what is
+ * in that snapshot. A session registered after the snapshot is invisible to the drain loop: its
+ * pane is left running and its worktree is never preserved, and nothing else ever reclaims
+ * either — the daemon's in-memory registry dies with the process. Refusing the spawn here,
+ * loudly, is what stops that session from ever being created in the first place, rather than
+ * silently handing the caller a session the daemon can no longer manage.
+ */
+public final class ShuttingDownException extends RuntimeException {
+    public ShuttingDownException(String message) {
+        super(message);
+    }
+}

fleetd/src/test/java/dev/ltms/fleet/member/CompositePeerLauncherTest.java

@@ -615,6 +615,67 @@ class CompositePeerLauncherTest {
         assertEquals(1, adapter.spawnCount("b"));
     }
 
+    /**
+     * fleetd #315: {@code CompositePeerLauncher.spawn} rebuilds the {@link PlacementContext} after
+     * every failed attempt "so the policy excludes this profile" (see the comment at the retry call
+     * site) — but {@code FixedPlacementPolicy} never read {@code ctx.unreachable()}, so under the
+     * default {@code fixed} placement every retry re-picked the same dead default and a second,
+     * healthy, configured profile was never tried. This is the same scenario as
+     * {@link #failoverRetriesNextCandidateWhenProfileIsUnreachable}, but pinned to {@code fixed()}
+     * instead of {@code weighted()} — the three existing failover tests all use {@code weighted()},
+     * which is exactly why nobody caught this: the retry loop's contract has no coverage under its
+     * own default policy.
+     */
+    @Test
+    void failoverRetriesNextCandidateUnderFixedPlacementWhenProfileIsUnreachable() {
+        FakeHerdr herdr = new FakeHerdr();
+        Map<String, FleetConfig.Profile> profiles = ordered(
+                "a", stubWorker("a"),
+                "b", stubWorker("b"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, profiles, "a", Set.of("a"));
+        CompositePeerLauncher composite = new CompositePeerLauncher(
+                List.of(adapter), "a", profiles, PlacementPolicies.fixed(), _ -> 0);
+
+        PeerHandle h = composite.spawn(new SpawnRequest(null, null, null));
+        assertEquals("b", h.profile(),
+                "fixed placement must fail over from the unreachable default a to the healthy b");
+        assertEquals(1, adapter.spawnCount("a"), "a was tried once and failed");
+        assertEquals(1, adapter.spawnCount("b"), "b was tried once and succeeded");
+    }
+
+    /**
+     * fleetd #315: the same fix — {@code FixedPlacementPolicy} consulting {@code ctx.unreachable()}
+     * — also covers the wiring-bug branch in {@code CompositePeerLauncher.spawn}: a profile that
+     * placement is allowed to choose (it is in the configured candidate list) but that no delegate
+     * declares ({@code byProfile.get(chosen.profile()) == null}). That branch adds the profile to
+     * {@code unreachable} and {@code continue}s without ever calling a launcher, so before this fix
+     * {@code fixed} handed back the same adapterless profile on every remaining attempt too.
+     */
+    @Test
+    void failoverSkipsAConfiguredProfileNoAdapterDeclaresUnderFixedPlacement() {
+        FakeHerdr herdr = new FakeHerdr();
+        // Placement's candidate list has three profiles, in this order (LinkedHashMap preserves it,
+        // and the fixed default resolves to the first — see the `ordered` helper's own javadoc).
+        Map<String, FleetConfig.Profile> profiles = new LinkedHashMap<>();
+        profiles.put("c", stubWorker("c"));
+        profiles.put("a", stubWorker("a"));
+        profiles.put("b", stubWorker("b"));
+        // The adapter only declares a and b — c is a configured profile with no owning adapter,
+        // the "wiring bug" the comment in CompositePeerLauncher.spawn calls out.
+        Map<String, FleetConfig.Profile> adapterProfiles = new LinkedHashMap<>();
+        adapterProfiles.put("a", stubWorker("a"));
+        adapterProfiles.put("b", stubWorker("b"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, adapterProfiles, "a", Set.of());
+        CompositePeerLauncher composite = new CompositePeerLauncher(
+                List.of(adapter), "a", profiles, PlacementPolicies.fixed(), _ -> 0);
+
+        PeerHandle h = composite.spawn(new SpawnRequest(null, null, null));
+        assertEquals("a", h.profile(),
+                "c has no adapter, so fixed placement must skip it and land on the next candidate, a");
+        assertEquals(0, adapter.spawnCount("c"), "c is never spawned — no adapter owns it");
+        assertEquals(1, adapter.spawnCount("a"));
+    }
+
     @Test
     void explicitSpawnAtMaxLoadThrowsPlacementExceptionNamingProfileLiveAndCap() {
         FakeHerdr herdr = new FakeHerdr();

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

@@ -403,6 +403,52 @@ class GitWorktreesTest {
         assertTrue(heads.isBlank(), "the branch leaked after a post-creation step threw:\n" + heads);
     }
 
+    /**
+     * fleetd #309. The add runner is a narrow seam for the case where Git has created state but
+     * the caller then kills the process. The runner first performs the real add in this throwaway
+     * repo, then throws the same kind of exception that {@link GitWorktrees#exec} uses for a timeout.
+     * This proves the failure path cleans both real Git objects without waiting for a slow checkout.
+     */
+    @Test
+    void addCleansUpWhenTheWorktreeAddRunnerFailsAfterCreatingState(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        String branch = "cb-309-timeout";
+        WorktreeException timeout = new WorktreeException("command timed out: synthetic git worktree add");
+        AtomicReference<String> createdPath = new AtomicReference<>();
+        GitWorktrees worktrees = new GitWorktrees(tmp.resolve("wts").toString(), null, null, null, command -> {
+            createdPath.set(command[5]);
+            try {
+                git(repo, "worktree", "add", command[5], "-b", command[7], command[8]);
+            } catch (Exception e) {
+                throw new AssertionError("test setup could not create the worktree", e);
+            }
+            throw timeout;
+        });
+
+        WorktreeException thrown = assertThrows(WorktreeException.class,
+                () -> worktrees.add(repo.toString(), branch, "HEAD"));
+
+        assertSame(timeout, thrown, "cleanup must not replace the add failure");
+        assertNotNull(createdPath.get(), "the add runner must receive the worktree path");
+        assertFalse(Files.exists(Path.of(createdPath.get())),
+                "the worktree directory leaked after the add runner failed");
+        assertFalse(refExists(repo, "refs/heads/" + branch), "the branch leaked after the add runner failed");
+    }
+
+    /** An ordinary Git refusal must not delete the existing branch or log a cleanup warning. */
+    @Test
+    void addFailureBeforeCreatingAWorktreeIsQuiet(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        String branch = "already-exists";
+        git(repo, "branch", branch);
+
+        assertThrows(WorktreeException.class, () -> new GitWorktrees(tmp.resolve("wts").toString())
+                .add(repo.toString(), branch, "HEAD"));
+
+        assertTrue(refExists(repo, "refs/heads/" + branch), "the existing branch must remain");
+        assertTrue(capturedMessages().isEmpty(), "an ordinary Git refusal logged a warning: " + capturedMessages());
+    }
+
     // ---- CB-189: broader remote-URL coverage — every remote, both fetch and push URLs, any
     // non-SSH scheme. Reporting only, additive to the origin/https strip-and-refuse tests above. ----
 

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

@@ -26,7 +26,12 @@ import org.slf4j.LoggerFactory;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.LongSupplier;
 
 import static org.junit.jupiter.api.Assertions.*;
@@ -178,14 +183,19 @@ class SessionManagerTest {
     }
 
     private SessionManager sessionManager(FakeHerdr herdr, LongSupplier clock, int contextCap,
-                                          boolean clearAfterTurn) {
+                                           boolean clearAfterTurn) {
+        return sessionManager(herdr, clock, contextCap, clearAfterTurn, null);
+    }
+
+    private SessionManager sessionManager(FakeHerdr herdr, LongSupplier clock, int contextCap,
+                                           boolean clearAfterTurn, java.util.function.Consumer<MemberSession> hook) {
         FleetConfig.Profile cfg = new FleetConfig.Profile(
                 "ltms-local", "http://gx00.gw:8000", "coder", null, "FLEETD_WORKER_TOKEN",
                 List.of("ccs", "ltms-local"), "tab", "fleetd-workers",
                 "worker: {profile} #{n}", null, null, null);
         ClaudeCodeLauncher workers = new ClaudeCodeLauncher(new AgentControl(herdr), new WorkspaceControl(herdr),
                 new SubscriptionGuard(Set.of("gx00.gw")), Map.of(cfg.profile(), cfg), cfg.profile(), _ -> null);
-        return new SessionManager(workers, new GitWorktrees(), clock, contextCap, clearAfterTurn);
+        return new SessionManager(workers, new GitWorktrees(), clock, contextCap, clearAfterTurn, hook);
     }
 
     @Test
@@ -670,6 +680,24 @@ class SessionManagerTest {
                 "BUSY session remains");
     }
 
+    @Test
+    void reapIdleDoesNotReleaseSessionDeliveredAfterItsEligibilityCheck() {
+        long[] clock = {0};
+        FakeHerdr herdr = new FakeHerdr();
+        SessionManager[] manager = new SessionManager[1];
+        SessionManager sessions = sessionManager(herdr, () -> clock[0], 0, false,
+                session -> manager[0].onDelivered(session.terminalId(), TestTurnTokens.inert(session.terminalId())));
+        manager[0] = sessions;
+        MemberSession session = sessions.acquire("ltms-local", null, "/caller", "term_primary");
+        sessions.asPresence().markPresent(session.terminalId());
+
+        clock[0] = 11;
+        assertEquals(0, sessions.reapIdle(10), "delivery replaces the idle snapshot before release");
+        assertEquals(MemberSession.State.BUSY, sessions.get(session.paneId()).orElseThrow().state(),
+                "a just-delivered session stays registered and busy");
+        assertFalse(herdr.called("pane.close"), "the busy session pane is not stopped");
+    }
+
     @Test
     void doneSessionPastIdleTtlIsReaped() {
         long[] clock = {0};
@@ -824,6 +852,186 @@ class SessionManagerTest {
                 .count();
     }
 
+    // --- fleetd #308: a spawn accepted while the shutdown drain is running must not orphan ---
+
+    @Test
+    void acquireRefusesANewSpawnOnceDrainAllHasStarted() {
+        FakeHerdr herdr = new FakeHerdr();
+        SessionManager sessions = sessionManager(herdr);
+
+        sessions.drainAll(TimeUnit.MILLISECONDS.toNanos(50)); // empty roster — returns immediately,
+        // but the shutdown guard it flips must stay tripped for the life of the process.
+
+        ShuttingDownException e = assertThrows(ShuttingDownException.class,
+                () -> sessions.acquire("ltms-local", null, "/caller", "term_primary"),
+                "a spawn requested after the drain has begun must be refused loudly (invariant 3), "
+                        + "not silently registered into a registry the drain will never revisit");
+        assertNotNull(e.getMessage());
+        assertFalse(e.getMessage().isBlank(), "the refusal must say why, not just that it failed");
+        assertTrue(sessions.roster().isEmpty(), "the refused spawn must never reach the registry");
+    }
+
+    /**
+     * fleetd #308: the guard above closes most of the shutdown-race window, but it cannot close
+     * all of it — a caller that already passed the {@code draining} check before {@code drainAll}
+     * flips it can still be mid-{@code launcher.spawn()} (a real herdr round trip, not
+     * instantaneous) when {@code drainAll} takes its registry snapshot. This test forces exactly
+     * that interleaving with a launcher double that blocks the second {@code spawn()} call and the
+     * first {@code stop()} call until released, then proves the post-loop sweep in {@code
+     * drainAll} still finds and tears down the straggler that lands in the registry afterward.
+     */
+    @Test
+    void drainAllSweepsAStragglerThatRegisteredAfterTheInitialSnapshot() throws Exception {
+        FakeHerdr herdr = new FakeHerdr();
+        FleetConfig.Profile cfg = new FleetConfig.Profile(
+                "ltms-local", "http://gx00.gw:8000", "coder", null, "FLEETD_WORKER_TOKEN",
+                List.of("ccs", "ltms-local"), "tab", "fleetd-workers",
+                "worker: {profile} #{n}", null, null, null);
+        ClaudeCodeLauncher delegate = new ClaudeCodeLauncher(new AgentControl(herdr), new WorkspaceControl(herdr),
+                new SubscriptionGuard(Set.of("gx00.gw")), Map.of(cfg.profile(), cfg), cfg.profile(), _ -> null);
+        RaceLauncher race = new RaceLauncher(delegate);
+        SessionManager sessions = new SessionManager(race);
+
+        // Registered normally, before the drain starts — the first spawn call, never blocked.
+        MemberSession ready = sessions.acquire("ltms-local", "/ready", "/caller", "ownerR");
+
+        ExecutorService exec = Executors.newFixedThreadPool(2);
+        try {
+            // The straggler's acquire() reads `draining == false` (checked before this call ever
+            // touches the launcher) and then blocks inside its own spawn() — the second spawn call.
+            Future<MemberSession> straggler = exec.submit(() ->
+                    sessions.acquire("ltms-local", "/late", "/caller", "ownerLate"));
+
+            assertTrue(race.enteredSecondSpawn.await(5, TimeUnit.SECONDS),
+                    "the straggler must have passed the shutdown guard and reached spawn() before "
+                            + "drainAll ever runs");
+            assertEquals(1, sessions.roster().size(),
+                    "the straggler is still inside spawn() — not registered yet");
+
+            // drainAll flips `draining`, snapshots the registry (only `ready` is in it), and starts
+            // releasing that snapshot — its first release() call stops `ready`'s pane, which this
+            // launcher double blocks on so the interleaving below is deterministic, not a timing bet.
+            Future<?> drain = exec.submit(() -> sessions.drainAll(TimeUnit.SECONDS.toNanos(5)));
+
+            assertTrue(race.enteredFirstStop.await(5, TimeUnit.SECONDS),
+                    "drainAll must be stopping the ready session's pane — proof its initial "
+                            + "registry snapshot has already been taken");
+
+            // Only now does the straggler's spawn complete and register — strictly after the
+            // snapshot drainAll's main pass is working from.
+            race.releaseSecondSpawn.countDown();
+            MemberSession registered = straggler.get(5, TimeUnit.SECONDS);
+
+            // Let drainAll finish releasing `ready`; it then re-checks the registry and must find
+            // (and drain) the straggler that just landed in it.
+            race.releaseFirstStop.countDown();
+            drain.get(5, TimeUnit.SECONDS);
+
+            assertTrue(sessions.roster().isEmpty(),
+                    "the post-loop sweep must drain the straggler too, not just the initial snapshot");
+            assertNotNull(registered.paneId());
+            long paneCloseCalls = herdr.calls.stream().filter(c -> "pane.close".equals(c.method())).count();
+            assertEquals(2, paneCloseCalls,
+                    "both ready's pane AND the straggler's pane must actually be stopped — a pane "
+                            + "left running is exactly the orphan this ticket is about");
+        } finally {
+            exec.shutdownNow();
+        }
+    }
+
+    /**
+     * Delegates every call while blocking the SECOND {@code spawn()} call and the FIRST
+     * {@code stop()} call until the test releases them — used to force the fleetd #308 race
+     * deterministically instead of betting on real thread-scheduling timing.
+     */
+    private static final class RaceLauncher implements PeerLauncher {
+        private final PeerLauncher delegate;
+        private final AtomicInteger spawnCalls = new AtomicInteger();
+        private final AtomicInteger stopCalls = new AtomicInteger();
+        final CountDownLatch enteredSecondSpawn = new CountDownLatch(1);
+        final CountDownLatch releaseSecondSpawn = new CountDownLatch(1);
+        final CountDownLatch enteredFirstStop = new CountDownLatch(1);
+        final CountDownLatch releaseFirstStop = new CountDownLatch(1);
+
+        RaceLauncher(PeerLauncher delegate) {
+            this.delegate = delegate;
+        }
+
+        private static void awaitOrFail(CountDownLatch latch) {
+            try {
+                if (!latch.await(5, TimeUnit.SECONDS)) {
+                    throw new AssertionError("RaceLauncher latch timed out");
+                }
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new AssertionError("RaceLauncher latch interrupted", e);
+            }
+        }
+
+        @Override
+        public Set<Capability> capabilities() {
+            return delegate.capabilities();
+        }
+
+        @Override
+        public Set<Capability> capabilitiesFor(String profileName) {
+            return delegate.capabilitiesFor(profileName);
+        }
+
+        @Override
+        public PeerHandle spawn(SpawnRequest req) {
+            if (spawnCalls.incrementAndGet() == 2) {
+                enteredSecondSpawn.countDown();
+                awaitOrFail(releaseSecondSpawn);
+            }
+            return delegate.spawn(req);
+        }
+
+        @Override
+        public Set<String> profiles() {
+            return delegate.profiles();
+        }
+
+        @Override
+        public String defaultProfile() {
+            return delegate.defaultProfile();
+        }
+
+        @Override
+        public String effectiveCwd(SpawnRequest req) {
+            return delegate.effectiveCwd(req);
+        }
+
+        @Override
+        public List<String> parityOverlay(String profileName) {
+            return delegate.parityOverlay(profileName);
+        }
+
+        @Override
+        public List<?> list() {
+            return delegate.list();
+        }
+
+        @Override
+        public int reapOrphanWorkers() {
+            return delegate.reapOrphanWorkers();
+        }
+
+        @Override
+        public void stop(String id) {
+            if (stopCalls.incrementAndGet() == 1) {
+                enteredFirstStop.countDown();
+                awaitOrFail(releaseFirstStop);
+            }
+            delegate.stop(id);
+        }
+
+        @Override
+        public boolean clearContext(String id) {
+            return delegate.clearContext(id);
+        }
+    }
+
     private static List<String> promptTexts(FakeHerdr herdr) {
         return herdr.calls.stream()
                 .filter(c -> "agent.prompt".equals(c.method()))