Merge PR #697: fleetd #669 Unit B — recognise-only fleet.collaborators config block

fleetd/fleetd.example.yaml

@@ -669,6 +669,15 @@ fleet:
   #     kind: opencode
   #     model: openai/gpt-5.6-terra
 
+  # A collaborator tab, keyed by name (fleetd #669). This block is parsed and validated today;
+  # nothing yet recognises or addresses the tab it names. Recognise-only, like a profile-less
+  # `leaders:` entry above: there is no `profile:`, no `instances:` and no `kind:`. `tab:` is
+  # REQUIRED and is the only field identity depends on, matched case-insensitively — the same
+  # GET-THE-VALUE-RIGHT warning above the `leaders:` block applies here too.
+  # collaborators:
+  #   reviewer-alex:
+  #     tab: "collab: alex"
+
   # architects:
   #   architect-1:
   #     profile: opus                # a strong model, on the operator's subscription

fleetd/src/main/java/dev/ltms/fleet/config/FleetConfig.java

@@ -1176,6 +1176,25 @@ public record FleetConfig(
         }
     }
 
+    /**
+     * A tab fleetd recognises as a collaborator, keyed by name (fleetd #669).
+     *
+     * <p>Recognise-only: there is no {@code profile}, no {@code instances} and no {@code kind}.
+     * Nothing here ever launches a pane.
+     *
+     * <p>{@code tabPrefix} is absent. Identity is matched on the exact {@code tab} alone.
+     *
+     * @param tab the exact tab label hosting this collaborator, matched case-insensitively; the
+     *            only field identity depends on. Required — an entry with no {@code tab} can
+     *            never be discovered.
+     */
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    public record Collaborator(String tab) {
+        public Collaborator {
+            tab = (tab == null || tab.isBlank()) ? null : tab.strip();
+        }
+    }
+
     /**
      * One entry of a {@code fleet:} role pool — a role paired with the backend it runs on.
      *
@@ -1213,15 +1232,18 @@ public record FleetConfig(
      * is exactly compatible with that. The pool is also what replaced {@code defaultProfile:} — an
      * unqualified spawn names a role, and the role's pool supplies the candidates.
      *
-     * @param leaders     panes that orchestrate rather than are orchestrated, keyed by lead name
+     * @param leaders       panes that orchestrate rather than are orchestrated, keyed by lead name
-     * @param architects  profiles the {@code architect} role may run on
+     * @param architects    profiles the {@code architect} role may run on
-     * @param developers  profiles the {@code dev} role may run on
+     * @param developers    profiles the {@code dev} role may run on
-     * @param hunters     profiles the {@code hunter} role may run on
+     * @param hunters       profiles the {@code hunter} role may run on
-     * @param reviewers   profiles the {@code reviewer} role may run on
+     * @param reviewers     profiles the {@code reviewer} role may run on
-     * @param charters    optional launch-charter text keyed by singular role wire name
+     * @param charters      optional launch-charter text keyed by singular role wire name
-     * @param tabLabel    template for a member tab's label; {@code {role}}, {@code {profile}},
+     * @param tabLabel      template for a member tab's label; {@code {role}}, {@code {profile}},
-     *                    {@code {model}} and {@code {n}} (a per role+profile counter) are
+     *                      {@code {model}} and {@code {n}} (a per role+profile counter) are
-     *                    substituted. Default {@link #DEFAULT_TAB_LABEL}
+     *                      substituted. Default {@link #DEFAULT_TAB_LABEL}
+     * @param collaborators tabs fleetd recognises as collaborators (fleetd #669), keyed by name.
+     *                      Recognise-only, exactly like a {@code profile}-less {@link Leader}:
+     *                      nothing here is ever auto-launched.
      */
     @JsonIgnoreProperties(ignoreUnknown = true)
     public record Fleet(Map<String, Leader> leaders,
@@ -1230,7 +1252,8 @@ public record FleetConfig(
                         Map<String, Slot> hunters,
                         Map<String, Slot> reviewers,
                         Map<String, String> charters,
-                        String tabLabel) {
+                        String tabLabel,
+                        Map<String, Collaborator> collaborators) {
 
         /**
          * Role first, so the tab bar identifies the member's fleet role.
@@ -1245,26 +1268,30 @@ public record FleetConfig(
             reviewers = unmodifiableOrEmpty(reviewers);
             charters = unmodifiableOrEmpty(charters);
             tabLabel = (tabLabel == null || tabLabel.isBlank()) ? DEFAULT_TAB_LABEL : tabLabel;
+            collaborators = unmodifiableOrEmpty(collaborators);
         }
 
         /**
-         * A fleet with no configured launch charters — the shape every deployment had before
+         * A fleet with no configured launch charters and no collaborators — the shape every
-         * CB-566, and what most tests want.
+         * deployment had before CB-566, and what most tests want.
          *
          * <p>Kept deliberately, even though an overload that drops a new field is normally the
          * shape to avoid. It is safe here because nothing <em>reads</em> a charter through a
          * constructor: the launcher reads {@code fleet.charters()} from the live config. Jackson
          * binds the canonical constructor, so this one cannot swallow an operator's YAML.
+         * {@code collaborators} is dropped the same way and for the same reason: no caller of
+         * this overload has ever needed to set it, so it defaults to empty here exactly as the
+         * canonical constructor would default an absent YAML key.
          */
         public Fleet(Map<String, Leader> leaders, Map<String, Slot> architects,
                      Map<String, Slot> developers, Map<String, Slot> reviewers,
                      Map<String, String> charters, String tabLabel) {
-            this(leaders, architects, developers, null, reviewers, charters, tabLabel);
+            this(leaders, architects, developers, null, reviewers, charters, tabLabel, null);
         }
 
         public Fleet(Map<String, Leader> leaders, Map<String, Slot> architects,
                      Map<String, Slot> developers, Map<String, Slot> reviewers, String tabLabel) {
-            this(leaders, architects, developers, null, reviewers, null, tabLabel);
+            this(leaders, architects, developers, null, reviewers, null, tabLabel, null);
         }
 
         /**
@@ -1910,7 +1937,7 @@ public record FleetConfig(
 
     /** The {@code fleet:} child blocks whose direct children are slot names. */
     private static final Set<String> FLEET_POOL_KEYS =
-            Set.of("leaders", "architects", "developers", "hunters", "reviewers");
+            Set.of("leaders", "architects", "developers", "hunters", "reviewers", "collaborators");
 
     /**
      * Reject a {@code fleet:} role pool whose slot names repeat (CB-548, re-homed by CB-557).
@@ -1920,7 +1947,7 @@ public record FleetConfig(
      * daemon would never know. Jackson's YAML parser does not fail on duplicate mapping keys by
      * default, so duplicates are caught here, at parse time, before the map is built.
      *
-     * <p>Only the five pools <em>directly under the top-level {@code fleet:}</em> are considered,
+     * <p>Only the six pools <em>directly under the top-level {@code fleet:}</em> are considered,
      * and only their direct child keys (the slot names). A nested field elsewhere, even one also
      * named {@code developers:}, is ignored, so parsing of the rest of the config is unaffected.
      *
@@ -2679,17 +2706,21 @@ public record FleetConfig(
     }
 
     /**
-     * Reject a member tab-label template that could render as a configured lead tab or match a
+     * Reject a member tab-label template that could render as a configured lead or collaborator
-     * lead-tab naming convention, and reject two {@code fleet.leaders} entries that share one exact
+     * tab or match a lead-tab naming convention, and reject two {@code fleet.leaders} or
-     * tab.
+     * {@code fleet.collaborators} entries — across either registry — that share one exact tab.
+     *
+     * <p>{@code fleet.collaborators} has no {@code tabPrefix}: identity is matched on the exact
+     * {@code tab} alone, so only the exact-render check applies there, not the prefix check.
      *
      * @throws IllegalStateException when the fleet template or a profile {@code tabLabel} override
-     *                               can render as a configured lead tab or match a lead-tab prefix,
+     *                               can render as a configured lead or collaborator tab or match a
-     *                               or when two {@code fleet.leaders} entries carry the same exact
+     *                               lead-tab prefix, or when two entries — of either registry, or
-     *                               {@code tab} (case-insensitively)
+     *                               one of each — carry the same exact {@code tab}
+     *                               (case-insensitively)
      */
     public void validateLeadTabPrefixes() {
-        if (fleet == null || fleet.leaders().isEmpty()) {
+        if (fleet == null) {
             return;
         }
         List<String> bad = new ArrayList<>();
@@ -2722,11 +2753,32 @@ public record FleetConfig(
                         }
                     });
         });
+        fleet.collaborators().forEach((collabName, collaborator) -> {
+            if (collaborator == null) {
+                return;
+            }
+            String tab = collaborator.tab();
+            if (templateCanRenderAs(fleet.tabLabel(), tab)) {
+                bad.add("fleet.tabLabel=\"" + fleet.tabLabel() + "\" can render as the tab of "
+                        + "collaborator '" + collabName + "' (\"" + tab + "\")");
+            }
+            profiles().entrySet().stream()
+                    .map(Map.Entry::getKey)
+                    .sorted()
+                    .forEach(p -> {
+                        String label = profiles().get(p).tabLabel();
+                        if (templateCanRenderAs(label, tab)) {
+                            bad.add("profile '" + p + "' overrides tabLabel with \"" + label
+                                    + "\", which can render as the tab of collaborator '"
+                                    + collabName + "' (\"" + tab + "\")");
+                        }
+                    });
+        });
         if (!bad.isEmpty()) {
             throw new IllegalStateException("refusing to start: " + String.join("; ", bad)
-                    + ". Every member labelled that way would be read back as a lead and granted "
+                    + ". Every member labelled that way would be read back as a lead or "
-                    + "spawn/stop/send on the whole fleet. Change one of the two so member tabs "
+                    + "collaborator and granted that identity's authority. Change one of the two "
-                    + "and lead tabs cannot be confused.");
+                    + "so member tabs cannot be confused with a lead's or collaborator's tab.");
         }
 
         List<String> collisions = new ArrayList<>();
@@ -2749,13 +2801,49 @@ public record FleetConfig(
                 }
             }
         }
+        List<String> collabNames = fleet.collaborators().keySet().stream().sorted().toList();
+        for (int i = 0; i < collabNames.size(); i++) {
+            String nameA = collabNames.get(i);
+            Collaborator a = fleet.collaborators().get(nameA);
+            if (a == null || a.tab() == null || a.tab().isBlank()) {
+                continue;
+            }
+            for (int j = i + 1; j < collabNames.size(); j++) {
+                String nameB = collabNames.get(j);
+                Collaborator b = fleet.collaborators().get(nameB);
+                if (b == null || b.tab() == null || b.tab().isBlank()) {
+                    continue;
+                }
+                if (a.tab().equalsIgnoreCase(b.tab())) {
+                    collisions.add("collaborator '" + nameA + "' and collaborator '" + nameB
+                            + "' both use tab \"" + a.tab() + "\"");
+                }
+            }
+        }
+        for (String leadName : leadNames) {
+            Leader lead = fleet.leaders().get(leadName);
+            if (lead == null || lead.tab() == null || lead.tab().isBlank()) {
+                continue;
+            }
+            for (String collabName : collabNames) {
+                Collaborator collaborator = fleet.collaborators().get(collabName);
+                if (collaborator == null || collaborator.tab() == null
+                        || collaborator.tab().isBlank()) {
+                    continue;
+                }
+                if (lead.tab().equalsIgnoreCase(collaborator.tab())) {
+                    collisions.add("lead '" + leadName + "' and collaborator '" + collabName
+                            + "' both use tab \"" + lead.tab() + "\"");
+                }
+            }
+        }
         if (collisions.isEmpty()) {
             return;
         }
         throw new IllegalStateException("refusing to start: " + String.join("; ", collisions)
-                + ". Tab identity is matched exactly, so only one of two leads sharing a tab can "
+                + ". Tab identity is matched exactly, so only one of two entries sharing a tab can "
-                + "ever be found — the other is silently unreachable. Give each lead its own "
+                + "ever be found — the other is silently unreachable. Give each lead and "
-                + "exact tab.");
+                + "collaborator its own exact tab.");
     }
 
     private static boolean templateCanRenderAs(String template, String tab) {
@@ -2785,25 +2873,28 @@ public record FleetConfig(
 
     /**
      * Reject a profile that places its members by {@code "pane"} while any {@code fleet.leaders}
-     * entry names a {@code tab}. A pane-placed member lands inside the focused tab rather than its
+     * or {@code fleet.collaborators} entry names a {@code tab}. A pane-placed member lands inside
-     * own, so it can land inside a lead's own labelled tab. {@link
+     * the focused tab rather than its own, so it can land inside a lead's or collaborator's own
-     * dev.ltms.fleet.herdr.LeadTabScanner} identifies a lead purely by that tab's label — it does
+     * labelled tab. {@link dev.ltms.fleet.herdr.LeadTabScanner} identifies a lead or collaborator
-     * not exclude the member space — so a member that ends up there would be read back as the lead
+     * purely by that tab's label — it does not exclude the member space — so a member that ends up
-     * and granted spawn/stop/send on the whole fleet.
+     * there would be read back as that lead or collaborator and granted that identity's authority.
      *
-     * <p>Only a leader with a non-blank {@code tab} is in scope: one with no {@code tab} feeds
+     * <p>Only an entry with a non-blank {@code tab} is in scope: one with no {@code tab} feeds
      * nothing into {@link dev.ltms.fleet.herdr.LeadTabScanner}, so it creates no hazard here.
      *
      * @throws IllegalStateException when any {@code profiles:} entry is pane-placed while any
-     *                               {@code fleet.leaders} entry names a non-blank {@code tab}
+     *                               {@code fleet.leaders} or {@code fleet.collaborators} entry
+     *                               names a non-blank {@code tab}
      */
     public void validatePanePlacementAgainstLeadTabs() {
-        if (fleet == null || fleet.leaders().isEmpty()) {
+        if (fleet == null) {
             return;
         }
         boolean anyLeaderHasTab = fleet.leaders().values().stream()
                 .anyMatch(leader -> leader != null && leader.tab() != null && !leader.tab().isBlank());
-        if (!anyLeaderHasTab) {
+        boolean anyCollaboratorHasTab = fleet.collaborators().values().stream()
+                .anyMatch(c -> c != null && c.tab() != null && !c.tab().isBlank());
+        if (!anyLeaderHasTab && !anyCollaboratorHasTab) {
             return;
         }
         List<String> bad = new ArrayList<>();
@@ -2816,10 +2907,11 @@ public record FleetConfig(
             return;
         }
         throw new IllegalStateException("refusing to start: profile(s) " + bad
-                + " use placement: pane while fleet.leaders names a tab. A pane-placed member can "
+                + " use placement: pane while fleet.leaders or fleet.collaborators names a tab. A "
-                + "land inside a lead's labelled tab and be read back as the lead, granted "
+                + "pane-placed member can land inside that labelled tab and be read back as the "
-                + "spawn/stop/send on the whole fleet. Set placement: tab for each named profile, "
+                + "lead or collaborator, granted that identity's authority. Set placement: tab for "
-                + "or remove the tab from every fleet.leaders entry.");
+                + "each named profile, or remove the tab from every fleet.leaders and "
+                + "fleet.collaborators entry.");
     }
 
     /**
@@ -2926,8 +3018,14 @@ public record FleetConfig(
      * so duplicates are unrepresentable by construction once loaded — and {@link #load(Path)}
      * already rejects a duplicated slot name at parse time, before the map collapses.
      *
-     * @throws IllegalStateException when a slot names no profile or an unknown one, or when a lead
+     * <p>Also rejects a {@code fleet.collaborators} entry with no (or a blank) {@code tab}. A
-     *                               can be neither found nor created, naming the offending entry
+     * {@code profile}-less lead is still useful recognise-only — {@code tab} is the only field
+     * that matters to it either way. A collaborator carries no other field at all, so a blank
+     * {@code tab} leaves nothing for the entry to mean.
+     *
+     * @throws IllegalStateException when a slot names no profile or an unknown one, when a lead
+     *                               can be neither found nor created, or when a collaborator names
+     *                               no tab, naming the offending entry
      */
     public void validateMembers() {
         if (fleet == null) {
@@ -2965,6 +3063,16 @@ public record FleetConfig(
                         + "auto-launched, labelled) purely by its tab, so every entry must name one.");
             }
         });
+        fleet.collaborators().forEach((name, collaborator) -> {
+            if (collaborator == null) {
+                return;
+            }
+            if (collaborator.tab() == null || collaborator.tab().isBlank()) {
+                bad.add("fleet.collaborators." + name + " has no tab: — a collaborator is "
+                        + "recognised purely by its tab, and carries no other field, so every "
+                        + "entry must name one.");
+            }
+        });
         if (!bad.isEmpty()) {
             throw new IllegalStateException("refusing to start: " + String.join(" ", bad));
         }

fleetd/src/test/java/dev/ltms/fleet/config/FleetConfigTest.java

@@ -1000,6 +1000,273 @@ class FleetConfigTest {
                 "no primary.terminal pin ⇒ nothing registered, even with fleet.leaders configured");
     }
 
+    // ── fleetd #669: the collaborators registry ────────────────────────────────────────────────
+
+    /**
+     * {@code Fleet} is {@code @JsonIgnoreProperties(ignoreUnknown = true)}, so a config naming
+     * {@code fleet.collaborators.<name>.tab} loads with no exception whether or not the key is
+     * ever read into the object model. Asserting only "no exception" would pass both before and
+     * after the real fix, so this asserts the parsed value is actually reachable from the loaded
+     * {@code FleetConfig} — the one thing a vacuous "no exception" test cannot tell apart.
+     */
+    @Test
+    void collaboratorsBlockIsActuallyParsedNotSilentlyDropped(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("collaborators.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    reviewer-alex:
+                      tab: "collab: alex"
+                """);
+
+        FleetConfig cfg = FleetConfig.load(f);
+        assertEquals("collab: alex", cfg.fleet().collaborators().get("reviewer-alex").tab());
+    }
+
+    /** A collaborator carries no field other than {@code tab}, so a blank one is meaningless. */
+    @Test
+    void aCollaboratorWithNoTabRefusesToStart(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("useless-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    ghost: {}
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e = assertThrows(IllegalStateException.class, cfg::validateMembers);
+        assertTrue(e.getMessage().contains("ghost"), "the message must name the useless entry");
+        assertTrue(e.getMessage().contains("tab:"), "the message must say what is missing");
+    }
+
+    /** Control for {@link #aCollaboratorWithNoTabRefusesToStart}: a named tab loads cleanly. */
+    @Test
+    void aCollaboratorWithATabIsAllowed(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("named-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    reviewer-alex:
+                      tab: "collab: alex"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        assertDoesNotThrow(cfg::validateMembers);
+    }
+
+    /**
+     * fleetd #669: the fleet-wide {@code tabLabel} template can render as a collaborator tab, the
+     * same hazard {@link #aFleetTabLabelTemplateThatCanRenderAsALeadTabRefusesToStart} covers on
+     * the lead side. Drives the fleet-wide branch directly, with no profile override involved.
+     */
+    @Test
+    void aFleetTabLabelTemplateThatCanRenderAsACollaboratorTabRefusesToStart(@TempDir Path dir)
+            throws Exception {
+        Path f = dir.resolve("collide-template-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  tabLabel: "al{profile}"
+                  collaborators:
+                    alex:
+                      tab: "alpha"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e =
+                assertThrows(IllegalStateException.class, cfg::validateLeadTabPrefixes);
+        assertTrue(e.getMessage().contains("fleet.tabLabel"));
+        assertTrue(e.getMessage().contains("alex"), "the message must name the offending collaborator");
+    }
+
+    /**
+     * fleetd #669: a member tabLabel that can render as a configured collaborator tab is the same
+     * hazard as the lead case above — a member labelled that way is read back as the collaborator.
+     */
+    @Test
+    void aProfileTabLabelOverrideMatchingACollaboratorTabRefusesToStart(@TempDir Path dir)
+            throws Exception {
+        Path f = dir.resolve("collide-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                profiles:
+                  gx10:
+                    tabLabel: "collab-tab"
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "collab-tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e =
+                assertThrows(IllegalStateException.class, cfg::validateLeadTabPrefixes);
+        assertTrue(e.getMessage().contains("gx10"), "the message must name the offending profile");
+        assertTrue(e.getMessage().contains("collab-tab"), "the message must name the offending label");
+    }
+
+    /** Control: a profile tabLabel that cannot render as the collaborator tab is allowed. */
+    @Test
+    void aProfileTabLabelThatCannotRenderAsACollaboratorTabIsAllowed(@TempDir Path dir)
+            throws Exception {
+        Path f = dir.resolve("ok-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                profiles:
+                  gx10:
+                    tabLabel: "worker-{profile}"
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "collab-tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        assertDoesNotThrow(cfg::validateLeadTabPrefixes);
+    }
+
+    /** fleetd #669: identity is matched on a collaborator's exact tab, so two sharing one are unreachable. */
+    @Test
+    void twoCollaboratorsSharingTheSameExactTabRefusesToStart(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("shared-collaborator-tab.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "shared tab"
+                    sam:
+                      tab: "Shared Tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e =
+                assertThrows(IllegalStateException.class, cfg::validateLeadTabPrefixes);
+        assertTrue(e.getMessage().contains("alex"), "the message must name one offending collaborator");
+        assertTrue(e.getMessage().contains("sam"), "the message must name the other offending collaborator");
+    }
+
+    /** Control for {@link #twoCollaboratorsSharingTheSameExactTabRefusesToStart}: distinct tabs load cleanly. */
+    @Test
+    void twoCollaboratorsWithDistinctExactTabsAreAllowed(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("distinct-collaborator-tabs.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "alex tab"
+                    sam:
+                      tab: "sam tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        assertDoesNotThrow(cfg::validateLeadTabPrefixes);
+    }
+
+    /**
+     * fleetd #669: a collaborator tab equal to a lead tab crosses a privilege boundary — the worst
+     * of the three new collisions, since only one of the two identities is ever found.
+     */
+    @Test
+    void aCollaboratorTabEqualToALeadTabRefusesToStart(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("lead-collaborator-collision.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  leaders:
+                    opus:
+                      tab: "shared tab"
+                  collaborators:
+                    alex:
+                      tab: "Shared Tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e =
+                assertThrows(IllegalStateException.class, cfg::validateLeadTabPrefixes);
+        assertTrue(e.getMessage().contains("opus"), "the message must name the offending lead");
+        assertTrue(e.getMessage().contains("alex"), "the message must name the offending collaborator");
+    }
+
+    /** Control for {@link #aCollaboratorTabEqualToALeadTabRefusesToStart}: distinct tabs load cleanly. */
+    @Test
+    void aLeadAndACollaboratorWithDistinctTabsAreAllowed(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("lead-collaborator-ok.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  leaders:
+                    opus:
+                      tab: "lead tab"
+                  collaborators:
+                    alex:
+                      tab: "collab tab"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        assertDoesNotThrow(cfg::validateLeadTabPrefixes);
+    }
+
+    /**
+     * fleetd #669: a pane-placed member can land in a collaborator's labelled tab exactly as it
+     * can land in a lead's — {@code validatePanePlacementAgainstLeadTabs()} must fire even when
+     * {@code fleet.leaders} is empty, which is the early-return the brief flagged as the bug.
+     */
+    @Test
+    void aPanePlacedProfileWithACollaboratorTabRefusesToStartEvenWithNoLeaders(@TempDir Path dir)
+            throws Exception {
+        Path f = dir.resolve("pane-hazard-collaborator.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                profiles:
+                  gx10:
+                    placement: pane
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "collab: alex"
+                """);
+        FleetConfig cfg = FleetConfig.load(f);
+
+        IllegalStateException e = assertThrows(IllegalStateException.class,
+                cfg::validatePanePlacementAgainstLeadTabs);
+        assertTrue(e.getMessage().contains("gx10"), "the message must name the offending profile");
+    }
+
+    /** Control: a pane-placed profile with no lead or collaborator tab configured is allowed. */
+    @Test
+    void aPanePlacedProfileWithNoLeaderOrCollaboratorTabIsAllowed(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("pane-no-tab-at-all.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                profiles:
+                  gx10:
+                    placement: pane
+                fleet:
+                  collaborators:
+                    alex: {}
+                """);
+
+        assertDoesNotThrow(() -> FleetConfig.load(f).validatePanePlacementAgainstLeadTabs(),
+                "a collaborator with no tab feeds nothing into the scanner, so pane placement is safe");
+    }
+
     // ── CB-548: the architects registry ────────────────────────────────────────────────────────
 
     @Test
@@ -1272,6 +1539,60 @@ class FleetConfigTest {
         assertEquals(Set.of("sonnet"), cfg.fleet().pool(MemberRole.REVIEWER).keySet());
     }
 
+    /**
+     * A duplicated name in {@code fleet.collaborators} is refused at parse time, like any other
+     * {@code fleet:} pool. See {@link #duplicateSlotNamesInOnePoolAreRejectedAtParseTime}.
+     */
+    @Test
+    void duplicateCollaboratorNamesAreRejectedAtParseTime(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("collaborator-dup.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                fleet:
+                  collaborators:
+                    alex:
+                      tab: "collab: alex"
+                    alex:
+                      tab: "collab: alex, second"
+                """);
+
+        IllegalStateException e =
+                assertThrows(IllegalStateException.class, () -> FleetConfig.load(f));
+        assertTrue(e.getMessage().contains("alex"),
+                "the refusal names the duplicated entry, was: " + e.getMessage());
+        assertTrue(e.getMessage().contains("fleet.collaborators"),
+                "the refusal names the pool the duplicate is in, was: " + e.getMessage());
+    }
+
+    /**
+     * Control for {@link #duplicateCollaboratorNamesAreRejectedAtParseTime}: the same name reused
+     * across the collaborators registry and a member role pool is the role × profile matrix doing
+     * its job in the other pool, not a mistake — only a repeat within one pool loses an entry.
+     */
+    @Test
+    void theSameNameInCollaboratorsAndAnotherPoolIsNotADuplicate(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("collaborator-cross-pool.yaml");
+        Files.writeString(f, """
+                bind:
+                  port: 8080
+                profiles:
+                  sonnet:
+                    baseUrl: http://gx10.gw:8000
+                fleet:
+                  architects:
+                    alex:
+                      profile: sonnet
+                  collaborators:
+                    alex:
+                      tab: "collab: alex"
+                """);
+
+        FleetConfig cfg = assertDoesNotThrow(() -> FleetConfig.load(f));
+        assertEquals(Set.of("alex"), cfg.fleet().pool(MemberRole.ARCHITECT).keySet());
+        assertEquals(Set.of("alex"), cfg.fleet().collaborators().keySet());
+    }
+
     @Test
     void duplicateKeysOutsideTheFleetPoolsAreUnaffected(@TempDir Path dir) throws Exception {
         // The duplicate check is scoped to the fleet pools — a duplicate elsewhere is not this