fleetd/src/main/java/dev/ltms/fleet/herdr/PaneLocator.java

@@ -192,6 +192,31 @@ public final class PaneLocator {
         return out;
     }
 
+    /**
+     * The tab and workspace id of the herdr pane carrying {@code terminal}, from {@code pane.list}
+     * across every searched daemon — the same call {@link #terminalForPid} scans. Either field is
+     * {@code null} when no pane matches {@code terminal}, or when the matching pane itself carries
+     * no tab or workspace id.
+     */
+    public record PaneLocation(String tabId, String workspaceId) {
+        static final PaneLocation NONE = new PaneLocation(null, null);
+    }
+
+    /** Resolve {@code terminal} to the tab/workspace id of the pane it occupies. See {@link PaneLocation}. */
+    public PaneLocation locate(String terminal) {
+        if (terminal == null) {
+            return PaneLocation.NONE;
+        }
+        for (HerdrClient herdr : herdrs) {
+            for (JsonNode pane : herdr.call("pane.list", Map.of()).path("panes")) {
+                if (terminal.equals(pane.path("terminal_id").asText(null))) {
+                    return new PaneLocation(pane.path("tab_id").asText(null), pane.path("workspace_id").asText(null));
+                }
+            }
+        }
+        return PaneLocation.NONE;
+    }
+
     /** Whether a pane owns one of the scanned pid's ancestors, or the check of it failed outright. */
     private enum Ownership { OWNS, DOES_NOT_OWN, UNKNOWN }
 

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

@@ -9,6 +9,7 @@ import dev.ltms.fleet.auth.Role;
 import dev.ltms.fleet.guard.GuardException;
 import dev.ltms.fleet.herdr.Agent;
 import dev.ltms.fleet.herdr.AgentStatus;
+import dev.ltms.fleet.herdr.PaneLocator;
 import dev.ltms.fleet.metrics.FleetMetrics;
 import dev.ltms.fleet.metrics.Metrics;
 import dev.ltms.fleet.inject.MemberPresence;
@@ -503,7 +504,7 @@ public final class FleetMcp {
                     // An observer's SEND reaches a pane that cannot otherwise distinguish this
                     // from a human paste (see attributeIfObserver); every other caller's content
                     // passes through unchanged.
-                    String content = attributeIfObserver(caller, str(a, "content"));
+                    String content = attributeIfObserver(caller, str(a, "content"), identity.panes());
                     String turnId = str(a, "turnId");
                     String coordId = str(a, "coordId");
                     if (coordId != null && !coordId.isBlank()) {
@@ -987,12 +988,49 @@ public final class FleetMcp {
     /**
      * The text an observer's {@code SEND} actually delivers: prefixed with the sender's own
      * connection-resolved terminal, which the receiving pane cannot otherwise tell apart from a
-     * human paste. Every other caller's content passes through unchanged. Shared with {@code
-     * FleetApp}'s REST entry path so both surfaces attribute identically.
+     * human paste, plus its tab and workspace display label in parentheses when herdr can supply
+     * either. The terminal id is the only thing in the header a reply can target — a label is
+     * display-only, is never unique, and is never substituted for it. Every other caller's content
+     * passes through unchanged. Shared with {@code FleetApp}'s REST entry path so both surfaces
+     * attribute identically.
      */
-    public static String attributeIfObserver(Principal caller, String content) {
-        return caller != null && caller.isObserver()
-                ? "[fleet_send from observer " + caller.terminal() + "]\n" + content : content;
+    public static String attributeIfObserver(Principal caller, String content, PaneLocator panes) {
+        if (caller == null || !caller.isObserver()) {
+            return content;
+        }
+        return "[fleet_send from observer " + observerHeader(caller.terminal(), panes) + "]\n" + content;
+    }
+
+    /**
+     * {@code terminal}, plus {@code (space "…", tab "…")} for whichever of its workspace/tab
+     * labels herdr reports — omitted entirely when neither is known, so a degraded lookup still
+     * reads as the bare id and never as {@code null} or an empty parenthetical.
+     */
+    private static String observerHeader(String terminal, PaneLocator panes) {
+        String tabLabel = null;
+        String workspaceLabel = null;
+        try {
+            PaneLocator.PaneLocation location = panes.locate(terminal);
+            tabLabel = location.tabId() == null ? null : panes.tabLabelsByTabId().get(location.tabId());
+            workspaceLabel = location.workspaceId() == null ? null
+                    : panes.workspaceLabelsByWorkspaceId().get(location.workspaceId());
+        } catch (HerdrException e) {
+            // degrade to the id alone
+        }
+        if (tabLabel == null && workspaceLabel == null) {
+            return terminal;
+        }
+        StringBuilder header = new StringBuilder(terminal).append(" (");
+        if (workspaceLabel != null) {
+            header.append("space \"").append(workspaceLabel).append('"');
+        }
+        if (tabLabel != null && workspaceLabel != null) {
+            header.append(", ");
+        }
+        if (tabLabel != null) {
+            header.append("tab \"").append(tabLabel).append('"');
+        }
+        return header.append(')').toString();
     }
 
     /**

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

@@ -714,7 +714,7 @@ public final class FleetApp {
         // An observer's SEND reaches a pane that cannot otherwise distinguish this from a human
         // paste (see FleetMcp#attributeIfObserver, the same rule on the MCP entry path); every
         // other caller's content passes through unchanged.
-        content = FleetMcp.attributeIfObserver(caller, content);
+        content = FleetMcp.attributeIfObserver(caller, content, new PaneLocator(herdr, memberHerdr));
         timeout = Math.clamp(timeout, 1, MAX_MESSAGE_TIMEOUT_MS);
 
         // Answering a worker's fleet_ask (CB-205): always blocks, and derives the worker from turnId.

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

@@ -0,0 +1,93 @@
+package dev.ltms.fleet.mcp;
+
+import dev.ltms.fleet.auth.Principal;
+import dev.ltms.fleet.herdr.FakeHerdr;
+import dev.ltms.fleet.herdr.PaneLocator;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * {@link FleetMcp#attributeIfObserver}: the terminal id in an observer's header is always
+ * present, a tab/workspace label is display-only and additive, and a missing label degrades to
+ * the id alone rather than rendering {@code null} or an empty parenthetical.
+ */
+class FleetMcpAttributeIfObserverTest {
+
+    @Test
+    void aNonObserverPassesContentThroughUnchangedRegardlessOfPanes() {
+        Principal worker = Principal.worker("term_worker", 1);
+        assertEquals("hello", FleetMcp.attributeIfObserver(worker, "hello", null));
+    }
+
+    @Test
+    void theTerminalIdIsAlwaysPresentAndNeverReplacedByALabel() {
+        FakeHerdr herdr = new FakeHerdr()
+                .withTab("w2", "w2:t8", "shell-tab");
+        PaneLocator panes = new PaneLocator(herdr);
+        Principal observer = Principal.observer("term_shell", 2);
+
+        String result = FleetMcp.attributeIfObserver(observer, "hi", panes);
+
+        assertEquals("[fleet_send from observer term_shell (space \"ltms\", tab \"shell-tab\")]\nhi", result);
+    }
+
+    /**
+     * Two tabs sharing one label must still read as two different senders. The label is the same
+     * on both headers; the id is what differs, and is the only part of either header a reply can
+     * target.
+     */
+    @Test
+    void aSharedLabelStillYieldsDistinctHeadersByTerminalId() {
+        FakeHerdr herdr = new FakeHerdr()
+                .withTab("w2", "w2:t7", "lead")
+                .withTab("w2", "w2:t8", "lead");
+        PaneLocator panes = new PaneLocator(herdr);
+
+        String fromA = FleetMcp.attributeIfObserver(Principal.observer("term_a", 1), "msg", panes);
+        String fromShell = FleetMcp.attributeIfObserver(Principal.observer("term_shell", 2), "msg", panes);
+
+        assertEquals("[fleet_send from observer term_a (space \"ltms\", tab \"lead\")]\nmsg", fromA);
+        assertEquals("[fleet_send from observer term_shell (space \"ltms\", tab \"lead\")]\nmsg", fromShell);
+        assertNotEquals(fromA, fromShell, "identical labels must not collapse two senders into one header");
+    }
+
+    @Test
+    void anUnknownPaneDegradesToTheIdAloneWithNoLabelAndNoEmptyParens() {
+        PaneLocator panes = new PaneLocator(new FakeHerdr().withNoPanes());
+        Principal observer = Principal.observer("term_ghost", 3);
+
+        String result = FleetMcp.attributeIfObserver(observer, "msg", panes);
+
+        assertEquals("[fleet_send from observer term_ghost]\nmsg", result);
+        assertFalse(result.contains("null"), "a missing label must never render as the literal \"null\"");
+        assertFalse(result.contains("()"), "a missing label must never leave an empty parenthetical");
+    }
+
+    @Test
+    void aHerdrFailureDuringTheLabelLookupDegradesToTheIdAlone() {
+        FakeHerdr herdr = new FakeHerdr().workspaceListFailsWith("unavailable");
+        PaneLocator panes = new PaneLocator(herdr);
+        Principal observer = Principal.observer("term_shell", 4);
+
+        String result = FleetMcp.attributeIfObserver(observer, "msg", panes);
+
+        assertEquals("[fleet_send from observer term_shell]\nmsg", result);
+    }
+
+    @Test
+    void onlyTheKnownLabelAppearsWhenTheOtherIsMissing() {
+        // term_shell's pane sits in workspace "w2" ("ltms"); its tab "w2:t8" carries no seeded
+        // label, so only the space label appears.
+        PaneLocator panes = new PaneLocator(new FakeHerdr());
+        Principal observer = Principal.observer("term_shell", 5);
+
+        String result = FleetMcp.attributeIfObserver(observer, "msg", panes);
+
+        assertEquals("[fleet_send from observer term_shell (space \"ltms\")]\nmsg", result);
+        assertTrue(result.contains("term_shell"), "the id must still be present");
+    }
+}

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

@@ -119,7 +119,10 @@ class FleetMcpObserverSendDeliveryTest {
 
         @SuppressWarnings("unchecked")
         Map<String, Object> params = (Map<String, Object>) herdr.lastCall("agent.prompt").params();
-        assertEquals("[fleet_send from observer term_shell]\nhi there", params.get("text"),
+        // term_shell's pane sits in workspace "w2", which FakeHerdr's workspace.list labels
+        // "ltms"; its tab "w2:t8" carries no label in FakeHerdr's tab.list, so only the space
+        // label appears.
+        assertEquals("[fleet_send from observer term_shell (space \"ltms\")]\nhi there", params.get("text"),
                 "the receiving pane must see the sender's own daemon-resolved terminal, never a raw "
                         + "echo of the content and never a client-supplied name");
     }

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

@@ -140,7 +140,10 @@ class FleetMcpObserverSendToLeadDeliveryTest {
 
         @SuppressWarnings("unchecked")
         Map<String, Object> params = (Map<String, Object>) herdr.lastCall("agent.prompt").params();
-        assertEquals("[fleet_send from observer term_shell]\ncan we split the review?",
+        // term_shell's pane sits in workspace "w2", which FakeHerdr's workspace.list labels
+        // "ltms"; its tab "w2:t8" carries no label in FakeHerdr's tab.list, so only the space
+        // label appears.
+        assertEquals("[fleet_send from observer term_shell (space \"ltms\")]\ncan we split the review?",
                 params.get("text"),
                 "a lead must see the sender's own daemon-resolved terminal, never a raw echo of "
                         + "the content and never a client-supplied name");