#309: clean partial worktrees after add failure

Four latches gate delivery in Injector, and only awaitingCompletion had a way
out of a sustained unknown streak. CB-109 added that escape because a worker
stuck in a state herdr cannot classify never produces a working->idle
boundary. The same is true during post-turn housekeeping, but the escape was
never extended there.

awaitingPostTurnPickup and postTurnObserved are both released only on an
injectable sample, so a worker that goes unknown and stays there wedges: the
target is polled forever, every later message to it is blocked by the delivery
gate, and no onTurnFailed fires, so the session sits at DONE and looks healthy.
The counter did not even increment, since ++unknownSinceTurn sits inside the
awaitingCompletion short-circuit.

postTurnPending needs no escape; it is cleared on the line after the listener
call that sets it.

The escape does not set turnFailed. The delegated turn already completed and
its waiter already resolved — what is outstanding is the /clear. Failing the
turn would drive SessionManager.onFailed on a session that genuinely finished.

Not reachable in the live configuration: the path needs lifecycle.clearAfterTurn,
which fleetd.yaml does not set. It becomes reachable as soon as anyone turns
that supported knob on.

Fixes #306

fleetd/src/main/java/dev/ltms/fleet/auth/CallerResolver.java

@@ -262,11 +262,15 @@ public final class CallerResolver {
         return token.isEmpty() ? null : token;
     }
 
+    /**
+     * fleetd #305: delegates to {@link ConnectionIdentity#isLoopback}. This used to be a second,
+     * independent copy of the same rule, and the two drifted: this one accepted all of
+     * {@code 127.0.0.0/8}, {@code ConnectionIdentity}'s accepted only {@code 127.0.0.1}. A caller
+     * from {@code 127.0.0.2} therefore had its identity skipped (so it had no terminal) and was
+     * then read as loopback here — which under loopback-trust is the primary. Sharing the inputs
+     * would not have prevented that; only sharing the computation does.
+     */
     private static boolean isLoopback(String remoteAddr) {
-        if (remoteAddr == null) {
-            return false;
-        }
-        return remoteAddr.equals("127.0.0.1") || remoteAddr.equals("::1")
-                || remoteAddr.equals("0:0:0:0:0:0:0:1") || remoteAddr.startsWith("127.");
+        return ConnectionIdentity.isLoopback(remoteAddr);
     }
 }

fleetd/src/main/java/dev/ltms/fleet/inject/Injector.java

@@ -157,6 +157,7 @@ public final class Injector {
         boolean awaitingCompletion; // a delivered message's turn is not yet known-complete
         boolean turnObserved;      // saw a real `working` sample since that delivery (turn ran)
         int unknownSinceTurn;      // consecutive `unknown` samples while a delegation is outstanding (CB-109)
+        int unknownSincePostTurn;  // the same, for the post-turn housekeeping phase (fleetd #306)
         int notReadySincePoll;     // consecutive injectable samples a queued message waited on the readiness gate (CB-114)
         boolean postTurnPending;   // completion observed; adapter housekeeping has not started yet
         boolean awaitingPostTurnPickup;
@@ -217,10 +218,12 @@ public final class Injector {
                 t.awaitingPickup = false;
                 t.injectableSincePickup = 0;
                 t.unknownSinceTurn = 0;
+                t.unknownSincePostTurn = 0;
                 t.notReadySincePoll = 0;
                 if (t.awaitingCompletion) t.turnObserved = true;
             } else if (status.injectable()) { // IDLE or BLOCKED
                 t.unknownSinceTurn = 0;
+                t.unknownSincePostTurn = 0;
                 if (t.awaitingPostTurnPickup) {
                     if (++t.injectableSincePostTurnPickup >= PICKUP_GRACE_POLLS) {
                         t.awaitingPostTurnPickup = false;
@@ -315,6 +318,24 @@ public final class Injector {
                     t.unknownSinceTurn = 0;
                     turnFailed = true;
                 }
+                // fleetd #306: the same escape for the post-turn housekeeping phase. Four latches
+                // gate delivery (awaitingCompletion, postTurnPending, awaitingPostTurnPickup,
+                // postTurnObserved) and only the first had a way out of a sustained unknown streak —
+                // a gate that closed one direction only. The other two below are released here as
+                // well; postTurnPending needs no escape because it is cleared unconditionally on the
+                // line after the listener call that sets it.
+                //
+                // This does NOT set turnFailed. The delegated turn already completed and its waiter
+                // already resolved — what is outstanding is adapter housekeeping (the `/clear`).
+                // Reporting a turn failure here would drive SessionManager.onFailed on a session
+                // that genuinely finished its work, which is a worse lie than the wedge.
+                if ((t.awaitingPostTurnPickup || t.postTurnObserved)
+                        && ++t.unknownSincePostTurn >= TURN_STALL_GRACE_POLLS) {
+                    t.awaitingPostTurnPickup = false;
+                    t.postTurnObserved = false;
+                    t.injectableSincePostTurnPickup = 0;
+                    t.unknownSincePostTurn = 0;
+                }
             }
 
             // Reclaim the entry once the worker is fully quiescent (nothing queued, no pickup or

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

@@ -60,7 +60,30 @@ public final class ConnectionIdentity {
         return pid > 0 ? cwds.cwdForPid(pid) : null;
     }
 
-    private static boolean isLoopback(String addr) {
-        return "127.0.0.1".equals(addr) || "::1".equals(addr) || "0:0:0:0:0:0:0:1".equals(addr);
+    /**
+     * Whether {@code addr} is a same-host address, and therefore one whose peer PID is worth
+     * looking up. <strong>This is the one definition of loopback in the daemon</strong> —
+     * {@code CallerResolver} calls it rather than keeping its own, because the two used to differ
+     * and that difference was a privilege escalation (fleetd #305).
+     *
+     * <p>The whole of {@code 127.0.0.0/8} counts, not just {@code 127.0.0.1}. On Linux every
+     * address in that range is bound to {@code lo} by default, so a process can connect to
+     * {@code 127.0.0.1:8765} with a source address of {@code 127.0.0.2} — measured on the Linux
+     * fleet host, where binding that source succeeds.
+     *
+     * <p><strong>Being strict here does not make the daemon safer; it makes it unsafe.</strong>
+     * That reads backwards, so it is worth stating plainly. This predicate does not decide whether
+     * a caller is trusted — it decides whether the caller's identity is <em>resolved at all</em>.
+     * Returning false means {@link #resolve} answers "no terminal", and downstream a caller with no
+     * terminal is treated as the primary under loopback-trust. So every address excluded here is an
+     * address on which a worker silently becomes the lead. Widening a check normally weakens it;
+     * widening this one is what closes the hole.
+     */
+    public static boolean isLoopback(String addr) {
+        if (addr == null) {
+            return false;
+        }
+        String a = addr.startsWith("::ffff:") ? addr.substring(7) : addr; // IPv4-mapped IPv6
+        return a.startsWith("127.") || "::1".equals(a) || "0:0:0:0:0:0:0:1".equals(a);
     }
 }

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

@@ -813,7 +813,12 @@ public final class FleetMcp {
             return error("fleet_reply is for workers only — could not identify the calling worker "
                     + "from the connection");
         }
-        if (content == null) {
+        // fleetd #302: isBlank, not == null, to match fleet_send's own guard above. MessageService
+        // .reply now REJECTS blank content, and this handler is a bare BiFunction with no try/catch
+        // around it — so a whitespace-only fleet_reply would leave here as an uncaught
+        // IllegalArgumentException instead of this clean tool error. Null and whitespace are the
+        // same mistake by the caller and must get the same answer.
+        if (isBlank(content)) {
             return error("content is required");
         }
         messages.reply(callerTerminal, content);

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

@@ -510,6 +510,12 @@ public final class FleetApp {
             ctx.status(400).json(Map.of("error", "unknown_profile", "detail", e.getMessage()));
         } catch (PeerUnreachableException e) {
             ctx.status(502).json(Map.of("error", "spawn_timeout", "detail", e.getMessage()));
+        } catch (HerdrException e) {
+            // fleetd #304: not every herdr failure on the spawn path is a readiness timeout, so
+            // PeerUnreachableException above does not cover this. Without this catch the exception
+            // escapes to Javalin's default 500, while fleet_spawn reports the same failure as a
+            // clean named error (FleetMcp.spawn) — the #297 one-door-guarded shape.
+            herdrError(ctx, e);
         }
     }
 
@@ -530,13 +536,29 @@ public final class FleetApp {
         return (s == null || s.isBlank()) ? null : s;
     }
 
-    /** Tear a worker down by pane id. */
+    /**
+     * Tear a worker down by pane id.
+     *
+     * <p>fleetd #304: the {@code HerdrException} catch is not cosmetic. {@code release} deregisters
+     * the session, notifies the release listener and preserves a dirty worktree <em>before</em> it
+     * calls {@code launcher.stop}, so a throw from that stop arrives after the teardown the caller
+     * asked for has already happened. Letting it escape gave Javalin's default 500, which tells the
+     * caller to retry — and the retry finds nothing in the registry, reaches the same stop, and
+     * throws again, so it can never succeed. {@code herdrError} instead answers 404 ("the pane is
+     * gone, stop retrying") or 502 ("herdr is upstream and broken, a retry may help"), matching what
+     * {@code fleet_stop} reports for the same failure.
+     */
     private void stopMember(Context ctx) {
         String paneId = ctx.pathParam("paneId");
         if (!allow(ctx, routeAction("DELETE /members/{paneId}"), paneId)) {
             return;
         }
-        sessions.release(paneId);
+        try {
+            sessions.release(paneId);
+        } catch (HerdrException e) {
+            herdrError(ctx, e);
+            return;
+        }
         ctx.status(204);
     }
 

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/test/java/dev/ltms/fleet/auth/CallerResolverTest.java

@@ -413,4 +413,29 @@ class CallerResolverTest {
         assertThrows(IllegalArgumentException.class, () -> new CallerResolver(id, true, null));
         assertThrows(IllegalArgumentException.class, () -> new CallerResolver(id, true, "  "));
     }
+    @Test
+    void aWorkerOnAnyLoopbackSourceAddressIsStillAWorkerNotThePrimary() {
+        // fleetd #305: the escalation. ConnectionIdentity used to accept only 127.0.0.1, so a
+        // worker connecting from 127.0.0.2 resolved to no terminal, and this resolver's own
+        // (wider) loopback check then made it the PRIMARY — granting spawn, stop, send and drain.
+        // Measured on the Linux fleet host: binding a source of 127.0.0.2 succeeds there, so the
+        // path is real and not theoretical.
+        CallerResolver r = new CallerResolver(workerIdentity(), false, null);
+        for (String src : new String[]{"127.0.0.1", "127.0.0.2", "127.1.2.3", "::ffff:127.0.0.2"}) {
+            Principal p = r.resolve(src, 55555, null);
+            assertEquals(Role.WORKER, p.role(), "a worker must stay a worker from source " + src);
+            assertEquals("term_a", p.terminal(), "worker terminal from source " + src);
+        }
+    }
+
+    @Test
+    void aNonWorkerOnAnyLoopbackSourceAddressIsStillThePrimary() {
+        // The other direction of the same fix: widening the identity check must not demote a
+        // legitimate same-host primary that happens to connect from another 127.* address.
+        CallerResolver r = new CallerResolver(nonWorkerIdentity(), false, null);
+        for (String src : new String[]{"127.0.0.1", "127.0.0.2", "::ffff:127.0.0.1"}) {
+            assertEquals(Role.PRIMARY, r.resolve(src, 55555, null).role(), "source " + src);
+        }
+    }
+
 }

fleetd/src/test/java/dev/ltms/fleet/inject/InjectorTest.java

@@ -297,6 +297,68 @@ class InjectorTest {
         assertTrue(inj.activeTargets().isEmpty(), "the wedged target is reclaimed, not polled forever");
     }
 
+    /** A listener whose post-turn housekeeping always starts, as SessionManager's does with clearAfterTurn on. */
+    private static final class PostTurnListener implements TurnListener {
+        @Override public void onTurnComplete(String target) { }
+        @Override public boolean hasPostTurnAction(String target) { return true; }
+        @Override public boolean onTurnCompleteWithPostAction(String target) { return true; }
+    }
+
+    @Test
+    void aWorkerThatWedgesInUnknownAwaitingPostTurnPickupIsReleased() {
+        // fleetd #306: the post-turn phase had no way out of a sustained unknown streak, so the
+        // pickup latch stayed set, the target was polled forever, and every later message to it was
+        // blocked by the delivery gate — while the session still looked healthy.
+        Captor cap = new Captor();
+        Injector inj = new Injector(new AgentControl(herdr), new PostTurnListener());
+        inj.enqueue(T, "task", TestTurnTokens.inert(T));
+
+        inj.onStatus(T, AgentStatus.IDLE);    // deliver
+        inj.onStatus(T, AgentStatus.WORKING); // turn starts
+        inj.onStatus(T, AgentStatus.IDLE);    // turn completes; housekeeping dispatched
+        for (int i = 0; i < STALL_SAMPLES; i++) inj.onStatus(T, AgentStatus.UNKNOWN); // then wedges
+
+        assertTrue(inj.activeTargets().isEmpty(),
+                "a target wedged awaiting post-turn pickup must be reclaimed, not polled forever");
+        assertEquals(List.of(), cap.failed,
+                "the delegated turn already completed — a stuck /clear must not be reported as a failed turn");
+    }
+
+    @Test
+    void aWorkerThatWedgesInUnknownAfterPickingUpTheResetIsReleased() {
+        // The sibling latch. postTurnObserved is set when the reset is seen picked up (WORKING) and
+        // is cleared only on a later injectable sample, so a wedge right after pickup sticks too.
+        Captor cap = new Captor();
+        Injector inj = new Injector(new AgentControl(herdr), new PostTurnListener());
+        inj.enqueue(T, "task", TestTurnTokens.inert(T));
+
+        inj.onStatus(T, AgentStatus.IDLE);
+        inj.onStatus(T, AgentStatus.WORKING);
+        inj.onStatus(T, AgentStatus.IDLE);    // turn complete; reset dispatched
+        inj.onStatus(T, AgentStatus.WORKING); // reset picked up -> postTurnObserved
+        for (int i = 0; i < STALL_SAMPLES; i++) inj.onStatus(T, AgentStatus.UNKNOWN);
+
+        assertTrue(inj.activeTargets().isEmpty(), "a wedge after reset pickup must also be reclaimed");
+        assertEquals(List.of(), cap.failed, "still not a turn failure");
+    }
+
+    @Test
+    void aBriefUnknownDuringPostTurnHousekeepingDoesNotDropTheLatch() {
+        // The other direction: the escape must not fire on a glitch, or the queued next delegation
+        // would overtake housekeeping that is still running.
+        Injector inj = new Injector(new AgentControl(herdr), new PostTurnListener());
+        inj.enqueue(T, "first", TestTurnTokens.inert(T));
+        inj.enqueue(T, "second", TestTurnTokens.inert(T));
+
+        inj.onStatus(T, AgentStatus.IDLE);
+        inj.onStatus(T, AgentStatus.WORKING);
+        inj.onStatus(T, AgentStatus.IDLE);    // first completes; reset dispatched
+        for (int i = 0; i < 10; i++) inj.onStatus(T, AgentStatus.UNKNOWN); // well under the grace
+
+        assertFalse(inj.activeTargets().isEmpty(), "a brief glitch must not release the post-turn latch");
+        assertEquals(List.of("first"), sent(), "the queued delegation must not overtake housekeeping");
+    }
+
     @Test
     void aTransientUnknownGlitchNeitherFailsNorBlocksCompletion() {
         Captor cap = new Captor();

fleetd/src/test/java/dev/ltms/fleet/mcp/ConnectionIdentityTest.java

@@ -20,6 +20,17 @@ class ConnectionIdentityTest {
         assertEquals("term_a", with(_ -> FakeHerdr.WORKER_PID).callerTerminal("127.0.0.1", 55555));
     }
 
+    @Test
+    void resolvesWorkerFromAnyLoopbackSourceAddressNotJust127001() {
+        // fleetd #305. On Linux the whole 127.0.0.0/8 is bound to lo, so a worker can connect with
+        // a source address of 127.0.0.2. If identity resolution skips that address the caller has
+        // no terminal, and a caller with no terminal is the primary under loopback-trust — so this
+        // must resolve the worker, not null.
+        assertEquals("term_a", with(_ -> FakeHerdr.WORKER_PID).callerTerminal("127.0.0.2", 55555));
+        assertEquals("term_a", with(_ -> FakeHerdr.WORKER_PID).callerTerminal("127.1.2.3", 55555));
+        assertEquals("term_a", with(_ -> FakeHerdr.WORKER_PID).callerTerminal("::ffff:127.0.0.2", 55555));
+    }
+
     @Test
     void nullForOffHostCaller() {
         // A non-loopback peer can't be an on-host worker → treat as primary/unknown.

fleetd/src/test/java/dev/ltms/fleet/mcp/FleetMcpTest.java

@@ -326,6 +326,26 @@ class FleetMcpTest {
         assertEquals("orphan", drained.getFirst().content());
     }
 
+    @Test
+    void replyWithBlankContentIsACleanToolErrorNotAnUncaughtException() {
+        // fleetd #302: MessageService.reply now REJECTS blank content by throwing. fleet_reply's
+        // handler is a bare BiFunction with no try/catch around it, so if this guard only checked
+        // `== null` (as it did), a whitespace-only reply would leave the handler as an uncaught
+        // IllegalArgumentException instead of a tool error the caller can read. Null and whitespace
+        // are the same caller mistake and must get the same answer — the sibling fleet_send guard
+        // has always used isBlank for exactly this reason.
+        for (String blank : new String[] {null, "", "   ", "\n\t"}) {
+            McpSchema.CallToolResult res = assertDoesNotThrow(
+                    () -> FleetMcp.reply(messages, "term_a", blank),
+                    "blank content must be refused as a tool error, never thrown out of the handler");
+            assertEquals(Boolean.TRUE, res.isError(), "blank content is an error result");
+            assertTrue(textOf(res).contains("content is required"),
+                    "the error names the missing argument: " + textOf(res));
+        }
+        assertEquals(0, messages.drainReplies("term_a").size(),
+                "a refused reply must not reach the inbox");
+    }
+
     @Test
     void bridgePollWithTargetDrainsReplies() {
         // A reply with no open send queues it in the inbox.

fleetd/src/test/java/dev/ltms/fleet/rest/FleetAppTest.java

@@ -415,7 +415,11 @@ class FleetAppTest {
         FakeHerdr herdr = new FakeHerdr().agentNameTakenTimes(99);
         int port = start(herdr, "http://gx00.gw:8000", Set.of("gx00.gw"));
 
-        assertEquals(500, req(port, "POST", "/members").statusCode());
+        // fleetd #304: 502, not Javalin's default 500 — the herdr failure is named, and the body
+        // carries herdr's own message, matching what fleet_spawn reports for the same failure.
+        HttpResponse<String> res = req(port, "POST", "/members");
+        assertEquals(502, res.statusCode());
+        assertEquals("herdr_error", mapper.readTree(res.body()).get("error").asText());
         assertTrue(herdr.called("tab.create"), "a tab was created before the failed start");
         assertEquals("w9:t2", params(herdr, "tab.close").get("tab_id"), "orphaned tab must be closed");
     }
@@ -733,7 +737,12 @@ class FleetAppTest {
         int port = start(herdr, "http://gx00.gw:8000", Set.of("gx00.gw"));
 
         // A genuine teardown failure must surface, not be reported as a successful 204.
-        assertEquals(500, req(port, "DELETE", "/members/w9:pW").statusCode());
+        // fleetd #304: it surfaces as a named 502 rather than Javalin's default 500. The property
+        // this test guards is "not 204" and the herdr detail reaching the caller — a bare 500 gave
+        // the body "Server Error" and said nothing about herdr.
+        HttpResponse<String> res = req(port, "DELETE", "/members/w9:pW");
+        assertEquals(502, res.statusCode());
+        assertEquals("herdr_error", mapper.readTree(res.body()).get("error").asText());
         assertFalse(herdr.called("tab.close"), "tab is not removed when the pane close failed");
     }
 
@@ -746,4 +755,5 @@ class FleetAppTest {
         assertEquals(204, req(port, "DELETE", "/members/w9:pW").statusCode());
         assertTrue(herdr.called("tab.close"));
     }
+
 }

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. ----