CB-586: prune refs/wip/* older than 24h whose tree is reachable from main

Add the CB-586 retention rule to GitWorktrees and drive it from the reaper:
a snapshot is deleted only when its tree content is already reachable from
main AND the ref is older than 24h. Reachability keeps the last copy of a
worker's work; the age floor stops a fresh snapshot being swept while a
lead is still looking at it. Every deletion logs the ref name and commit
sha so it is recoverable from the reflog. The /members response gains a
wipRefs{count,costBytes} census the operator can read without shelling
into the repo.

bridged/src/main/java/dev/ltms/bridged/rest/BridgedApp.java

@@ -234,7 +234,14 @@ public final class BridgedApp {
         List<Map<String, Object>> out = sessions.roster().stream()
                 .map(s -> SessionManager.rosterView(s, live.get(s.terminalId())))
                 .toList();
-        ctx.status(200).json(Map.of("workers", out));
+        Map<String, Object> body = new LinkedHashMap<>();
+        body.put("workers", out);
+        // CB-586: operator visibility for the refs/wip snapshot store without shelling into the
+        // repo — how many snapshot refs exist and roughly what they cost. Present only once a
+        // worktree session has established the repo, so a never-snapshotted fleet reports nothing.
+        sessions.wipRefs().ifPresent(st -> body.put("wipRefs",
+                Map.of("count", st.count(), "costBytes", st.costBytes())));
+        ctx.status(200).json(body);
     }
 
     /** The configured worker profiles and which one a no-argument spawn uses. */

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

@@ -12,9 +12,12 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Collectors;
@@ -299,6 +302,129 @@ public final class GitWorktrees implements Worktrees {
         return index;
     }
 
+    /**
+     * One {@code refs/wip/<branch>} snapshot ref as read by {@link #listWipRefs}: its full ref name,
+     * the snapshot commit's sha, and that commit's committer time in unix millis (the age of the
+     * snapshot — a snapshot is written once and never rewritten, so the commit date is the ref's).
+     */
+    private record WipRef(String refName, String sha, long committerMillis) {
+        String branch() {
+            return refName.substring("refs/wip/".length());
+        }
+    }
+
+    @Override
+    public WipRefStats wipRefs(String repoRoot) {
+        List<WipRef> refs = listWipRefs(repoRoot);
+        long costBytes = 0;
+        for (WipRef ref : refs) {
+            costBytes += treeSize(repoRoot, ref.sha());
+        }
+        return new WipRefStats(refs.size(), costBytes);
+    }
+
+    @Override
+    public int pruneWipRefs(String repoRoot, long minAgeMillis) {
+        // The rule is documented on Worktrees#pruneWipRefs: delete only a snapshot whose tree
+        // content is already reachable from main AND that is older than minAgeMillis. Reachability
+        // is the floor that keeps a worker's last copy; the age floor keeps a just-written snapshot
+        // from being swept while a lead may still be looking at it.
+        List<WipRef> refs = listWipRefs(repoRoot);
+        if (refs.isEmpty()) {
+            return 0;
+        }
+        long nowMillis = System.currentTimeMillis();
+        // Resolve what main carries once per sweep, not once per ref.
+        Set<String> mainObjects = reachableObjectsFromMain(repoRoot);
+        int deleted = 0;
+        for (WipRef ref : refs) {
+            long ageMillis = nowMillis - ref.committerMillis();
+            if (ageMillis <= minAgeMillis) {
+                continue; // too recent — never swept, even if it looks recoverable (CB-586)
+            }
+            String tree = exec("git", "-C", repoRoot, "rev-parse", ref.sha() + "^{tree}").trim();
+            if (!mainObjects.contains(tree)) {
+                // Last copy of the snapshot's content — the worker's work exists nowhere else.
+                // Never delete automatically (CB-586 criterion 2).
+                continue;
+            }
+            exec("git", "-C", repoRoot, "update-ref", "-d", ref.refName());
+            deleted++;
+            log.info("pruned snapshot ref refs/wip/{} commit={} (age {}h): its tree is already "
+                     + "reachable from main, so the work is preserved; recover from reflog via "
+                     + "git update-ref refs/wip/{} {}",
+                    ref.branch(), ref.sha(), TimeUnit.MILLISECONDS.toHours(ageMillis),
+                    ref.branch(), ref.sha());
+        }
+        return deleted;
+    }
+
+    /**
+     * Every {@code refs/wip/*} ref (see {@link WipRef}). The committer date is read as a unix
+     * count of seconds and converted to millis. {@code %00} (NUL) separates the fields because a
+     * branch name may contain spaces.
+     */
+    private List<WipRef> listWipRefs(String repoRoot) {
+        String out = exec("git", "-C", repoRoot, "for-each-ref",
+                "--format=%(refname)%00%(objectname)%00%(committerdate:unix)", "refs/wip/");
+        List<WipRef> refs = new ArrayList<>();
+        for (String line : out.split("\\R")) {
+            if (line.isBlank()) {
+                continue;
+            }
+            String[] parts = line.split("\u0000", -1);
+            if (parts.length == 3 && !parts[1].isBlank()) {
+                refs.add(new WipRef(parts[0], parts[1], Long.parseLong(parts[2]) * 1000L));
+            }
+        }
+        return refs;
+    }
+
+    /**
+     * The set of object shas reachable from {@code main}, or an empty set when {@code main} cannot
+     * be resolved. An empty set is the safe direction: the retention sweep then concludes nothing
+     * is recoverable, so it deletes nothing — a repo with no {@code main} must never cause a
+     * worker's last copy of a snapshot to be dropped on a reachability misreading.
+     */
+    private Set<String> reachableObjectsFromMain(String repoRoot) {
+        if (exitCode("git", "-C", repoRoot, "rev-parse", "--verify", "main") != 0) {
+            log.debug("refs/wip retention: no 'main' ref in {} — treating nothing as reachable", repoRoot);
+            return Set.of();
+        }
+        String out = exec("git", "-C", repoRoot, "rev-list", "--objects", "main");
+        Set<String> objects = new HashSet<>();
+        for (String line : out.split("\\R")) {
+            if (line.isBlank()) {
+                continue;
+            }
+            int sp = line.indexOf(' ');
+            objects.add(sp < 0 ? line : line.substring(0, sp));
+        }
+        return objects;
+    }
+
+    /** Approximate cost of a snapshot: the sum of every blob's size in its committed tree. */
+    private long treeSize(String repoRoot, String sha) {
+        String out = exec("git", "-C", repoRoot, "ls-tree", "-r", "-l", sha);
+        long total = 0;
+        for (String line : out.split("\\R")) {
+            if (line.isBlank()) {
+                continue;
+            }
+            // ls-tree -l row: "<mode> <type> <object> <size>\t<path>"; the size is only numeric for
+            // blobs (trees read "-"), so gate on the type token and take the 4th whitespace field.
+            String[] parts = line.split("\\s+");
+            if (parts.length >= 4 && "blob".equals(parts[1])) {
+                try {
+                    total += Long.parseLong(parts[3]);
+                } catch (NumberFormatException ignored) {
+                    // a '-' size (or any anomaly) contributes nothing to the rough figure
+                }
+            }
+        }
+        return total;
+    }
+
     /** Resolve the directory that will hold per-session worktree checkouts. */
     private Path resolveRoot(String repoRoot) {
         if (configuredRoot != null && !configuredRoot.isBlank()) {

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

@@ -53,6 +53,14 @@ public final class SessionManager implements TurnListener {
     private final int contextCap;
     private final boolean clearAfterTurn;
     private volatile MemberLifecycle memberLifecycle = MemberLifecycle.NONE;
+    /**
+     * CB-586: the repo root the fleet actually works in, remembered the first time a worktree
+     * session is spawned (worktrees are checkouts of it). {@code refs/wip/*} live there, and this
+     * single cached value is what the snapshot retention sweep and the operator-visible census run
+     * against. The daemon is bridged into one project at a time, so "the first worktree's repo" is
+     * the repo; {@code null} until any worktree is spawned, meaning nothing to sweep or measure.
+     */
+    private volatile String fleetRepoRoot;
 
     /** CB-520: notified with a terminalId on every acquire; no-op until wired. */
     private final List<Consumer<String>> acquireListeners = new java.util.concurrent.CopyOnWriteArrayList<>();
@@ -450,6 +458,11 @@ public final class SessionManager implements TurnListener {
         // The non-worktree path always used this chain; only this branch was missed.
         String repoRoot = worktrees.repoRoot(
                 launcher.effectiveCwd(new SpawnRequest(preResolvedProfile, requestedCwd, callerCwd)));
+        if (fleetRepoRoot == null) {
+            // CB-586: remember the repo whose worktrees the fleet spawns — its refs/wip/* are the
+            // snapshot store the retention sweep and the operator census operate on.
+            fleetRepoRoot = repoRoot;
+        }
         String branch = "worker/" + slug(wt.ticketSlug()) + "-" + nonce();
         String path = null;
         PeerHandle handle;
@@ -740,6 +753,26 @@ public final class SessionManager implements TurnListener {
         return registry.size();
     }
 
+    /**
+     * CB-586: the operator-visible census of {@code refs/wip/*} in the repo the fleet works in —
+     * how many snapshot refs exist and roughly what they cost. Empty (no repo known) until at
+     * least one worktree session has been spawned, exactly so a fleet that has never snapshotted
+     * anything surfaces nothing new, as it did before CB-586.
+     */
+    public Optional<Worktrees.WipRefStats> wipRefs() {
+        String repo = fleetRepoRoot;
+        return repo == null ? Optional.empty() : Optional.of(worktrees.wipRefs(repo));
+    }
+
+    /**
+     * CB-586: run the snapshot retention sweep in the fleet's repo (a no-op until a worktree has
+     * been spawned, which establishes the repo). Returns how many {@code refs/wip/*} it deleted.
+     */
+    public int sweepWipRefs(long minAgeMillis) {
+        String repo = fleetRepoRoot;
+        return repo == null ? 0 : worktrees.pruneWipRefs(repo, minAgeMillis);
+    }
+
     /**
      * The registered session owning {@code terminalId}, or {@code null} if none does.
      *

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

@@ -14,12 +14,20 @@ public final class SessionReaper {
 
     private static final Logger log = LoggerFactory.getLogger(SessionReaper.class);
     private static final long DEFAULT_INTERVAL_MILLIS = 5000;
+    /** CB-586: the refs/wip age floor — never sweep a snapshot younger than 24h (the CB-586 rule). */
+    private static final long WIP_MIN_AGE_MILLIS = TimeUnit.HOURS.toMillis(24);
+    /**
+     * CB-586: how often the retention sweep runs. Given the 24h age floor, running it every few
+     * hours means a ref is dropped within hours of becoming eligible, never within minutes.
+     */
+    private static final long WIP_SWEEP_INTERVAL_NANOS = TimeUnit.HOURS.toNanos(6);
 
     private final SessionManager sessions;
     private final long idleTtlNanos;
     private final long intervalMillis;
     private volatile boolean running;
     private Thread thread;
+    private volatile long lastWipSweepNanos = Long.MIN_VALUE;
 
     /** Construct a reaper with the default 5-second polling interval. */
     public SessionReaper(SessionManager sessions, long idleTtlSeconds) {
@@ -49,10 +57,32 @@ public final class SessionReaper {
             } catch (RuntimeException e) {
                 log.warn("session reaper iteration failed; continuing", e);
             }
+            maybeSweepWipRefs();
             sleep();
         }
     }
 
+    /**
+     * CB-586: run the refs/wip retention sweep on a slow cadence (hours, not the per-iteration
+     * millisecond loop). Best-effort — a failure must never take the idle-reap loop down with it.
+     */
+    private void maybeSweepWipRefs() {
+        long now = System.nanoTime();
+        if (now - lastWipSweepNanos < WIP_SWEEP_INTERVAL_NANOS) {
+            return;
+        }
+        try {
+            int deleted = sessions.sweepWipRefs(WIP_MIN_AGE_MILLIS);
+            if (deleted > 0) {
+                log.info("refs/wip retention sweep deleted {} snapshot ref(s) older than 24h whose "
+                        + "content was already reachable from main", deleted);
+            }
+        } catch (RuntimeException e) {
+            log.warn("refs/wip retention sweep failed; continuing", e);
+        }
+        lastWipSweepNanos = now;
+    }
+
     private void sleep() {
         try {
             Thread.sleep(intervalMillis);

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

@@ -54,4 +54,48 @@ public interface Worktrees {
      *         tolerance — a worktree that is gone holds nothing to snapshot)
      */
     Optional<String> snapshot(String worktreePath, String branch, String message);
+
+    /**
+     * CB-586: how many {@code refs/wip/*} snapshot refs exist in {@code repoRoot} and roughly what
+     * they cost. This is the operator-visible surface for the snapshot growth CB-578 stage C left
+     * behind — counts of refs alone hide that each one pins a whole tree for {@code git gc}.
+     *
+     * @param repoRoot the repository to scan
+     * @return count of snapshot refs, and {@code costBytes} = the approximate total working-tree
+     *         size of every snapshot's committed content (summed per ref, so shared objects are
+     *         counted once per ref that carries them)
+     */
+    WipRefStats wipRefs(String repoRoot);
+
+    /**
+     * CB-586: run the {@code refs/wip/*} retention sweep and return how many refs it deleted.
+     *
+     * <p>The retention rule is <em>reachability plus an age floor</em>. A snapshot ref is deleted
+     * only when <strong>both</strong> hold:
+     * <ol>
+     *   <li>its commit's <em>tree content</em> is already reachable from {@code main} — the work
+     *       the snapshot preserved has been recovered, so dropping the ref loses nothing; and</li>
+     *   <li>the ref is older than {@code minAgeMillis} — a very recent snapshot is never swept
+     *       while a lead may still be looking at it.</li>
+     * </ol>
+     *
+     * <p>Reachability is the safety property. A snapshot exists precisely because the work was not
+     * committed anywhere else, so a snapshot whose content is <em>not</em> reachable from
+     * {@code main} is the <strong>last copy</strong> of a worker's work and must never be deleted
+     * automatically — that is the failure CB-576 and CB-578 stage C were built to stop. Age alone
+     * must never drive a deletion, because age-based sweeping is exactly how the last copy gets
+     * destroyed. (Both numbers and the rule are CB-586's decision; this method only implements it.)
+     *
+     * <p>Every deletion logs the ref name and the commit sha, so an operator who finds they lost
+     * the wrong thing can still recover it from git's reflog.
+     *
+     * @param repoRoot     the repository whose {@code refs/wip/*} to sweep
+     * @param minAgeMillis the age floor; a ref younger than this is never touched
+     * @return the number of snapshot refs deleted
+     */
+    int pruneWipRefs(String repoRoot, long minAgeMillis);
+
+    /** CB-586: the operator-visible census of {@code refs/wip/*} in one repository. */
+    record WipRefStats(int count, long costBytes) {
+    }
 }

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

@@ -27,11 +27,15 @@ public final class FakeWorktrees implements Worktrees {
     public record SnapshotCall(String worktreePath, String branch, String message) {
     }
 
+    public record PruneCall(String repoRoot, long minAgeMillis) {
+    }
+
     private final List<AddCall> addCalls = new CopyOnWriteArrayList<>();
     private final List<RemoveCall> removeCalls = new CopyOnWriteArrayList<>();
     private final List<OverlayCall> overlayCalls = new CopyOnWriteArrayList<>();
     private final List<RepoRootCall> repoRootCalls = new CopyOnWriteArrayList<>();
     private final List<SnapshotCall> snapshotCalls = new CopyOnWriteArrayList<>();
+    private final List<PruneCall> pruneCalls = new CopyOnWriteArrayList<>();
     private final Set<String> existingPaths = ConcurrentHashMap.newKeySet();
     private final Set<String> trackedPaths = ConcurrentHashMap.newKeySet();
     private final AtomicLong snapshotSeq = new AtomicLong();
@@ -40,6 +44,8 @@ public final class FakeWorktrees implements Worktrees {
     private volatile boolean dirty = false;
     private volatile String repoRoot = "/repo";
     private volatile String prefix = "/worktrees";
+    private volatile WipRefStats wipRefs = new WipRefStats(0, 0L);
+    private volatile int pruneResult = 0;
 
     public FakeWorktrees withRepoRoot(String root) {
         this.repoRoot = root;
@@ -82,6 +88,18 @@ public final class FakeWorktrees implements Worktrees {
         return this;
     }
 
+    /** Configure the value returned by {@link #wipRefs}. */
+    public FakeWorktrees withWipRefs(WipRefStats stats) {
+        this.wipRefs = stats;
+        return this;
+    }
+
+    /** Configure the value returned by {@link #pruneWipRefs}. */
+    public FakeWorktrees withPruneResult(int deleted) {
+        this.pruneResult = deleted;
+        return this;
+    }
+
     @Override
     public String add(String repoRoot, String branch, String baseRef) {
         addCalls.add(new AddCall(repoRoot, branch, baseRef));
@@ -135,6 +153,17 @@ public final class FakeWorktrees implements Worktrees {
         return Optional.of("wip" + snapshotSeq.incrementAndGet());
     }
 
+    @Override
+    public WipRefStats wipRefs(String repoRoot) {
+        return wipRefs;
+    }
+
+    @Override
+    public int pruneWipRefs(String repoRoot, long minAgeMillis) {
+        pruneCalls.add(new PruneCall(repoRoot, minAgeMillis));
+        return pruneResult;
+    }
+
     public List<AddCall> addCalls() {
         return List.copyOf(addCalls);
     }
@@ -167,6 +196,10 @@ public final class FakeWorktrees implements Worktrees {
         return List.copyOf(snapshotCalls);
     }
 
+    public List<PruneCall> pruneCalls() {
+        return List.copyOf(pruneCalls);
+    }
+
     public SnapshotCall lastSnapshot() {
         return snapshotCalls.isEmpty() ? null : snapshotCalls.getLast();
     }

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

@@ -3,6 +3,7 @@ package dev.ltms.bridged.session;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.HashSet;
@@ -138,6 +139,53 @@ class GitWorktreesTest {
         return out;
     }
 
+    /** Write {@code content} as a blob into the object database; returns its sha. */
+    private static String blobOf(Path cwd, String content) throws Exception {
+        Process p = new ProcessBuilder("git", "-C", cwd.toString(), "hash-object", "-w", "--stdin")
+                .redirectErrorStream(true).start();
+        p.getOutputStream().write(content.getBytes(StandardCharsets.UTF_8));
+        p.getOutputStream().close();
+        String out = new String(p.getInputStream().readAllBytes()).trim();
+        assertTrue(p.waitFor(30, TimeUnit.SECONDS), "git hash-object timed out");
+        assertEquals(0, p.exitValue(), "git hash-object failed:\n" + out);
+        return out;
+    }
+
+    /** Build a single-file tree object from {@code blob}; returns the tree's sha. */
+    private static String treeOf(Path cwd, String path, String blob) throws Exception {
+        Process p = new ProcessBuilder("git", "-C", cwd.toString(), "mktree")
+                .redirectErrorStream(true).start();
+        p.getOutputStream().write(("100644 blob " + blob + "\t" + path + "\n").getBytes(StandardCharsets.UTF_8));
+        p.getOutputStream().close();
+        String out = new String(p.getInputStream().readAllBytes()).trim();
+        assertTrue(p.waitFor(30, TimeUnit.SECONDS), "git mktree timed out");
+        assertEquals(0, p.exitValue(), "git mktree failed:\n" + out);
+        return out;
+    }
+
+    /** {@code git commit-tree} rooted at {@code tree} with a chosen committer date; returns the sha. */
+    private static String commitTree(Path cwd, String tree, String parent, String committerDate,
+                                     String message) throws Exception {
+        ProcessBuilder pb = new ProcessBuilder("git", "-C", cwd.toString(), "commit-tree",
+                tree, "-p", parent, "-m", message);
+        pb.environment().put("GIT_COMMITTER_DATE", committerDate);
+        Process p = pb.redirectErrorStream(true).start();
+        String out = new String(p.getInputStream().readAllBytes()).trim();
+        assertTrue(p.waitFor(30, TimeUnit.SECONDS), "git commit-tree timed out");
+        assertEquals(0, p.exitValue(), "git commit-tree failed:\n" + out);
+        return out;
+    }
+
+    /** {@code git update-ref <ref> <sha>} — create the snapshot ref directly. */
+    private static void updateRef(Path cwd, String ref, String sha) throws Exception {
+        git(cwd, "update-ref", ref, sha);
+    }
+
+    /** True when {@code ref} exists in the repo (for-each-ref on a missing ref is empty, not an error). */
+    private static boolean refExists(Path cwd, String ref) throws Exception {
+        return !forEachRef(cwd, ref).trim().isEmpty();
+    }
+
     /**
      * The heart of CB-525: a provisioned worktree must not inherit the primary's MCP servers. Without
      * the isolation step the checked-out {@code .mcp.json} carries them in, and a worker navigating
@@ -474,4 +522,104 @@ class GitWorktreesTest {
         assertThrows(WorktreeException.class, () -> gitWorktrees.snapshot(wt, branch, "test snapshot"),
                 "an unresolvable real index must fail loudly, not silently snapshot from an empty index");
     }
+
+    /**
+     * CB-586, criterion 2. A snapshot whose content is NOT reachable from {@code main} is the last
+     * copy of a worker's work, and must never be deleted automatically — even when it is old and
+     * even when the caller passes a zero age floor. Uses the real snapshot path on a dirty worktree,
+     * so the unreachable tree is exactly the shape CB-576/CB-578 stage C exist to protect.
+     */
+    @Test
+    void anUnreachableSnapshotIsNeverPruned(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        GitWorktrees gitWorktrees = new GitWorktrees(tmp.resolve("wts").toString());
+        String branch = "cb-586-unreachable";
+        String wt = gitWorktrees.add(repo.toString(), branch, "HEAD");
+        Files.writeString(Path.of(wt).resolve("worker-draft.txt"), "work that exists nowhere else\n");
+
+        Optional<String> ref = gitWorktrees.snapshot(wt, branch, "snapshot with unreachable content");
+        assertTrue(ref.isPresent());
+
+        // Age floor 0 makes age a non-issue: only reachability can save it — and it must.
+        assertEquals(0, gitWorktrees.pruneWipRefs(repo.toString(), 0),
+                "the unreachable snapshot is the last copy and must not be pruned");
+        assertTrue(refExists(repo, "refs/wip/" + branch),
+                "an unreachable snapshot must survive the sweep");
+    }
+
+    /**
+     * CB-586, criterion 1 (the reachable half). A snapshot whose tree content IS already reachable
+     * from {@code main} and which is older than the age floor is pure duplication — the work is
+     * recovered — so it must be pruned.
+     */
+    @Test
+    void aReachableSnapshotOlderThanTheFloorIsPruned(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        GitWorktrees gitWorktrees = new GitWorktrees(tmp.resolve("wts").toString());
+
+        // A snapshot whose tree is exactly main's current tree: fully reachable from main.
+        String mainTree = revParse(repo, "main^{tree}");
+        String old = commitTree(repo, mainTree, revParse(repo, "HEAD"), "2020-01-01T00:00:00", "snapshot");
+        updateRef(repo, "refs/wip/recovered", old);
+
+        assertEquals(1, gitWorktrees.pruneWipRefs(repo.toString(), TimeUnit.HOURS.toMillis(24)),
+                "an old, main-reachable snapshot must be pruned");
+        assertFalse(refExists(repo, "refs/wip/recovered"),
+                "the reachable snapshot's ref must be gone after the sweep");
+    }
+
+    /**
+     * CB-586, the age floor. A snapshot whose content IS reachable from {@code main} but which is
+     * younger than the age floor must not be swept — a lead may still be looking at it.
+     */
+    @Test
+    void aReachableButRecentSnapshotIsNotPruned(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        GitWorktrees gitWorktrees = new GitWorktrees(tmp.resolve("wts").toString());
+
+        // Reachable from main, but committed "now" — a fresh snapshot. The 24h floor must protect it.
+        String mainTree = revParse(repo, "main^{tree}");
+        String fresh = commitTree(repo, mainTree, revParse(repo, "HEAD"),
+                "2038-01-01T00:00:00", "snapshot just taken");
+        updateRef(repo, "refs/wip/fresh", fresh);
+
+        assertEquals(0, gitWorktrees.pruneWipRefs(repo.toString(), TimeUnit.HOURS.toMillis(24)),
+                "a recent snapshot must be kept even when reachable");
+        assertTrue(refExists(repo, "refs/wip/fresh"),
+                "the recent reachable snapshot must survive the sweep");
+    }
+
+    /**
+     * CB-586, criterion 5. A fleet that has never snapshotted anything has no {@code refs/wip/*},
+     * so a sweep is a no-op and the census reports none — identical to before CB-586 existed.
+     */
+    @Test
+    void aFleetWithNoSnapshotsPrunesNothingAndReportsNothing(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        GitWorktrees gitWorktrees = new GitWorktrees(tmp.resolve("wts").toString());
+
+        assertEquals(0, gitWorktrees.pruneWipRefs(repo.toString(), 0),
+                "no snapshot refs means nothing to prune");
+        Worktrees.WipRefStats stats = gitWorktrees.wipRefs(repo.toString());
+        assertEquals(0, stats.count(), "a never-snapshotted fleet has zero refs/wip refs");
+        assertEquals(0L, stats.costBytes(), "a never-snapshotted fleet costs zero bytes");
+    }
+
+    /** CB-586, criterion 4: the census reports how many refs exist and roughly what they cost. */
+    @Test
+    void wipRefsReportsCountAndCost(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        GitWorktrees gitWorktrees = new GitWorktrees(tmp.resolve("wts").toString());
+
+        String blob = blobOf(repo, "a recoverable snapshot's worth of content");
+        String tree = treeOf(repo, "snapshot.txt", blob);
+        updateRef(repo, "refs/wip/one", commitTree(repo, tree, revParse(repo, "HEAD"),
+                "2020-01-01T00:00:00", "snapshot"));
+        updateRef(repo, "refs/wip/two", commitTree(repo, tree, revParse(repo, "HEAD"),
+                "2020-01-02T00:00:00", "snapshot"));
+
+        Worktrees.WipRefStats stats = gitWorktrees.wipRefs(repo.toString());
+        assertEquals(2, stats.count(), "two snapshot refs are reported");
+        assertTrue(stats.costBytes() > 0, "the cost of the snapshots is a positive byte count");
+    }
 }

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

@@ -138,6 +138,16 @@ class SessionManagerTest {
             return java.util.Optional.of("wip" + snapshotSeq.incrementAndGet());
         }
 
+        @Override
+        public WipRefStats wipRefs(String repoRoot) {
+            return new WipRefStats(0, 0L);
+        }
+
+        @Override
+        public int pruneWipRefs(String repoRoot, long minAgeMillis) {
+            return 0;
+        }
+
         List<String> removeCalls() {
             return List.copyOf(removeCalls);
         }

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

@@ -444,4 +444,37 @@ class WorktreeSessionManagerTest {
                 "a failed snapshot leaves no ref to report");
     }
 
+    /**
+     * CB-586, criteria 4 and 1. Once a worktree session is spawned the repo is known, so the
+     * operator census and the retention sweep delegate to that repo's {@code refs/wip/*}.
+     */
+    @Test
+    void wipRefsAndSweepDelegateToTheFleetRepoOnceKnown() {
+        FakeHerdr herdr = new FakeHerdr();
+        FakeWorktrees worktrees = new FakeWorktrees().withRepoRoot("/repo").withPrefix("/wt")
+                .withWipRefs(new Worktrees.WipRefStats(3, 42L)).withPruneResult(2);
+        SessionManager sessions = new SessionManager(workerService(herdr), worktrees);
+
+        assertTrue(sessions.wipRefs().isEmpty(),
+                "no worktree spawned yet means no repo is known and nothing to report");
+        assertEquals(0, sessions.sweepWipRefs(TimeUnit.HOURS.toMillis(24)),
+                "no worktree spawned yet means the sweep is a no-op");
+
+        sessions.acquire("ltms-local", null, "/caller/proj", null,
+                new WorktreeRequest("cb-586", null));
+
+        Worktrees.WipRefStats stats = sessions.wipRefs().orElseThrow();
+        assertEquals(3, stats.count(), "the census comes from the fleet repo");
+        assertEquals(42L, stats.costBytes(), "the cost comes from the fleet repo");
+        assertEquals(2, sessions.sweepWipRefs(TimeUnit.HOURS.toMillis(24)),
+                "the sweep runs against the fleet repo");
+
+        List<FakeWorktrees.PruneCall> prunes = worktrees.pruneCalls();
+        assertEquals(1, prunes.size(), "the no-op short-circuits before reaching the seam, so only "
+                + "the repo-known sweep issues a call");
+        assertEquals("/repo", prunes.getFirst().repoRoot(), "the sweep targets the fleet repo");
+        assertEquals(TimeUnit.HOURS.toMillis(24), prunes.getFirst().minAgeMillis(),
+                "the caller's age floor is passed through");
+    }
+
 }