diff --git a/src/main/services/infrastructure/teamWatchScope.ts b/src/main/services/infrastructure/teamWatchScope.ts
index 0137882b..9e471781 100644
--- a/src/main/services/infrastructure/teamWatchScope.ts
+++ b/src/main/services/infrastructure/teamWatchScope.ts
@@ -29,9 +29,9 @@ export function notifyTeamWatchScopeChanged(): void {
   scopeChangeListener?.();
 }
 
-function collectAliveTeams(scope: Set<string>): void {
+function collectAliveTeams(scope: Set<string>): boolean {
   if (!aliveTeamsProvider) {
-    return;
+    return true;
   }
   try {
     for (const teamName of aliveTeamsProvider()) {
@@ -39,9 +39,11 @@ function collectAliveTeams(scope: Set<string>): void {
         scope.add(teamName);
       }
     }
+    return true;
   } catch {
-    // A provider failure must never break watching. The watcher treats a thrown
-    // or empty scope conservatively (inboxes + root stay watched either way).
+    // A provider failure must never narrow watching. Returning null below is the
+    // safe fallback: watch every team, matching the original behavior.
+    return false;
   }
 }
 
@@ -49,9 +51,11 @@ function collectAliveTeams(scope: Set<string>): void {
  * Current set of teams whose team-root/task artifacts should be watched. Prunes
  * engaged entries past their TTL as a side effect of being called.
  */
-export function computeTeamWatchScope(nowMs: number = Date.now()): ReadonlySet<string> {
+export function computeTeamWatchScope(nowMs: number = Date.now()): ReadonlySet<string> | null {
   const scope = new Set<string>();
-  collectAliveTeams(scope);
+  if (!collectAliveTeams(scope)) {
+    return null;
+  }
   for (const [teamName, engagedAt] of engagedAtByTeam) {
     if (nowMs - engagedAt <= ENGAGED_TTL_MS) {
       scope.add(teamName);
@@ -71,7 +75,8 @@ export function markTeamEngaged(teamName: string, nowMs: number = Date.now()): v
   if (!teamName) {
     return;
   }
-  const wasInScope = computeTeamWatchScope(nowMs).has(teamName);
+  const currentScope = computeTeamWatchScope(nowMs);
+  const wasInScope = currentScope === null || currentScope.has(teamName);
   engagedAtByTeam.set(teamName, nowMs);
   if (!wasInScope) {
     scopeChangeListener?.();
diff --git a/test/main/ipc/teams.test.ts b/test/main/ipc/teams.test.ts
index ca43152d..a43f261a 100644
--- a/test/main/ipc/teams.test.ts
+++ b/test/main/ipc/teams.test.ts
@@ -1323,7 +1323,7 @@ describe('ipc teams handlers', () => {
   it('marks created teams engaged before provisioning writes startup artifacts', async () => {
     const createTeam = 'created-watch-scope';
     provisioningService.createTeam.mockImplementationOnce(async () => {
-      expect(computeTeamWatchScope().has(createTeam)).toBe(true);
+      expect(computeTeamWatchScope()?.has(createTeam)).toBe(true);
       return { runId: 'run-created-watch-scope' };
     });
 
@@ -1334,7 +1334,7 @@ describe('ipc teams handlers', () => {
     })) as { success: boolean };
 
     expect(result.success).toBe(true);
-    expect(computeTeamWatchScope().has(createTeam)).toBe(true);
+    expect(computeTeamWatchScope()?.has(createTeam)).toBe(true);
   });
 
   it('returns cached TEAM_LIST data under active launch pressure without starting another scan', async () => {
@@ -4401,7 +4401,7 @@ describe('ipc teams handlers', () => {
         })) as { success: boolean };
 
         expect(result.success).toBe(true);
-        expect(computeTeamWatchScope().has('draft-team')).toBe(true);
+        expect(computeTeamWatchScope()?.has('draft-team')).toBe(true);
         expect(provisioningService.launchTeam).not.toHaveBeenCalled();
         expect(provisioningService.createTeam).toHaveBeenCalledWith(
           {
diff --git a/test/main/services/infrastructure/teamWatchScope.test.ts b/test/main/services/infrastructure/teamWatchScope.test.ts
index 5901c34f..fff0f888 100644
--- a/test/main/services/infrastructure/teamWatchScope.test.ts
+++ b/test/main/services/infrastructure/teamWatchScope.test.ts
@@ -18,23 +18,23 @@ afterEach(() => {
 describe('teamWatchScope', () => {
   it('includes alive teams from the provider', () => {
     setAliveTeamsProvider(() => ['t-alive']);
-    expect([...computeTeamWatchScope(1000)]).toContain('t-alive');
+    expect([...(computeTeamWatchScope(1000) ?? [])]).toContain('t-alive');
   });
 
   it('includes engaged teams within TTL and prunes after expiry', () => {
     markTeamEngaged('t-eng', 0);
-    expect(computeTeamWatchScope(FIVE_MIN).has('t-eng')).toBe(true);
-    expect(computeTeamWatchScope(FIVE_MIN + 1).has('t-eng')).toBe(false);
+    expect(computeTeamWatchScope(FIVE_MIN)?.has('t-eng')).toBe(true);
+    expect(computeTeamWatchScope(FIVE_MIN + 1)?.has('t-eng')).toBe(false);
     // pruning is sticky: it stays out without re-engaging
-    expect(computeTeamWatchScope(FIVE_MIN + 2).has('t-eng')).toBe(false);
+    expect(computeTeamWatchScope(FIVE_MIN + 2)?.has('t-eng')).toBe(false);
   });
 
   it('unions alive and engaged teams', () => {
     setAliveTeamsProvider(() => ['a']);
     markTeamEngaged('b', 0);
     const scope = computeTeamWatchScope(1000);
-    expect(scope.has('a')).toBe(true);
-    expect(scope.has('b')).toBe(true);
+    expect(scope?.has('a')).toBe(true);
+    expect(scope?.has('b')).toBe(true);
   });
 
   it('notifies the listener only when engagement newly adds to scope', () => {
@@ -66,7 +66,7 @@ describe('teamWatchScope', () => {
       throw new Error('boom');
     });
     expect(() => computeTeamWatchScope(0)).not.toThrow();
-    expect([...computeTeamWatchScope(0)]).toEqual([]);
+    expect(computeTeamWatchScope(0)).toBeNull();
   });
 
   it('ignores empty team names', () => {
@@ -74,6 +74,6 @@ describe('teamWatchScope', () => {
     setTeamWatchScopeChangeListener(listener);
     markTeamEngaged('', 0);
     expect(listener).not.toHaveBeenCalled();
-    expect(computeTeamWatchScope(0).size).toBe(0);
+    expect(computeTeamWatchScope(0)?.size).toBe(0);
   });
 });