diff --git a/src/app/components/chat/chat.component.spec.ts b/src/app/components/chat/chat.component.spec.ts
index 6b4f165d..de44945b 100644
--- a/src/app/components/chat/chat.component.spec.ts
+++ b/src/app/components/chat/chat.component.spec.ts
@@ -28,6 +28,7 @@ import {ActivatedRoute, NavigationEnd, Router, UrlTree} from '@angular/router';
 import {BehaviorSubject, NEVER, of, ReplaySubject, Subject, throwError} from 'rxjs';
 
 import {EvalCase} from '../../core/models/Eval';
+import {OPERATION_GENERATE_CONTENT} from '../../core/models/Trace';
 import {Session} from '../../core/models/Session';
 import {UiEvent} from '../../core/models/UiEvent';
 import {AGENT_SERVICE, AgentService} from '../../core/services/interfaces/agent';
@@ -2149,4 +2150,76 @@ describe('ChatComponent', () => {
       });
     });
   });
+
+  describe('updateSystemInstructionFlags', () => {
+    function llmSpan(
+      eventId: string, startTime: number, systemInstruction: string): any {
+      return {
+        attrEventId: eventId,
+        attrOperationName: OPERATION_GENERATE_CONTENT,
+        start_time: startTime,
+        io: {inputs: {system_instruction: systemInstruction}},
+      };
+    }
+
+    it('should not flag a system instruction change across an agent boundary',
+       () => {
+         component.eventData.set(
+             'event-root-1', {id: 'event-root-1', author: 'root_agent'});
+         component.eventData.set(
+             'event-sub-1', {id: 'event-sub-1', author: 'sub_agent'});
+         component.eventData.set(
+             'event-root-2', {id: 'event-root-2', author: 'root_agent'});
+         component.traceData = [
+           llmSpan('event-root-1', 1, 'root instruction'),
+           llmSpan('event-sub-1', 2, 'sub instruction'),
+           llmSpan('event-root-2', 3, 'root instruction'),
+         ];
+
+         component['updateSystemInstructionFlags']();
+
+         expect(component.eventData.get('event-sub-1').systemInstructionChanged)
+             .toBeFalsy();
+         expect(component.eventData.get('event-root-2').systemInstructionChanged)
+             .toBeFalsy();
+       });
+
+    it('should still flag a real system instruction change within the same agent',
+       () => {
+         component.eventData.set(
+             'event-root-1', {id: 'event-root-1', author: 'root_agent'});
+         component.eventData.set(
+             'event-root-2', {id: 'event-root-2', author: 'root_agent'});
+         component.traceData = [
+           llmSpan('event-root-1', 1, 'instruction v1'),
+           llmSpan('event-root-2', 2, 'instruction v2'),
+         ];
+
+         component['updateSystemInstructionFlags']();
+
+         const event = component.eventData.get('event-root-2');
+         expect(event.systemInstructionChanged).toBeTrue();
+         expect(event.precedingSystemInstruction).toBe('instruction v1');
+         expect(event.currentSystemInstruction).toBe('instruction v2');
+       });
+
+    it('should fall back to the span\'s own attrAgentName when the event has no author',
+       () => {
+         component.eventData.set('event-root-1', {id: 'event-root-1'});
+         component.eventData.set('event-sub-1', {id: 'event-sub-1'});
+         component.eventData.set('event-root-2', {id: 'event-root-2'});
+         component.traceData = [
+           {...llmSpan('event-root-1', 1, 'root instruction'), attrAgentName: 'root_agent'},
+           {...llmSpan('event-sub-1', 2, 'sub instruction'), attrAgentName: 'sub_agent'},
+           {...llmSpan('event-root-2', 3, 'root instruction'), attrAgentName: 'root_agent'},
+         ];
+
+         component['updateSystemInstructionFlags']();
+
+         expect(component.eventData.get('event-sub-1').systemInstructionChanged)
+             .toBeFalsy();
+         expect(component.eventData.get('event-root-2').systemInstructionChanged)
+             .toBeFalsy();
+       });
+  });
 });
diff --git a/src/app/components/chat/chat.component.ts b/src/app/components/chat/chat.component.ts
index 7b19e8cb..bfaa5e03 100644
--- a/src/app/components/chat/chat.component.ts
+++ b/src/app/components/chat/chat.component.ts
@@ -2694,22 +2694,42 @@ export class ChatComponent implements OnInit, AfterViewInit, OnDestroy {
       event.currentSystemInstruction = undefined;
     }
 
-    // Compare consecutive LLM turns
-    for (let i = 1; i < llmSpans.length; i++) {
-      const currentSpan = llmSpans[i];
-      const precedingSpan = llmSpans[i - 1];
-
-      const currentSys = extractSystemInstruction(currentSpan.io?.inputs);
-      const precedingSys = extractSystemInstruction(precedingSpan.io?.inputs);
-
-      if (currentSys && precedingSys && currentSys !== precedingSys) {
-        const eventId = currentSpan.attrEventId;
-        if (eventId) {
-          const event = this.eventData.get(eventId);
-          if (event) {
-            event.systemInstructionChanged = true;
-            event.precedingSystemInstruction = precedingSys;
-            event.currentSystemInstruction = currentSys;
+    // A system instruction is only meaningful *within* a single agent's own
+    // sequence of calls: distinct agents never shared a cache context to
+    // begin with, so crossing an agent boundary is not a real "change".
+    // Group the (already time-sorted) spans by agent before comparing
+    // consecutive turns, instead of comparing across the whole session.
+    const spansByAgent = new Map<string, Span[]>();
+    for (const span of llmSpans) {
+      const eventId = span.attrEventId;
+      const event = eventId ? this.eventData.get(eventId) : undefined;
+      const agentKey = event?.author || span.attrAgentName || '';
+      const bucket = spansByAgent.get(agentKey);
+      if (bucket) {
+        bucket.push(span);
+      } else {
+        spansByAgent.set(agentKey, [span]);
+      }
+    }
+
+    // Compare consecutive LLM turns within each agent's own sequence.
+    for (const agentSpans of spansByAgent.values()) {
+      for (let i = 1; i < agentSpans.length; i++) {
+        const currentSpan = agentSpans[i];
+        const precedingSpan = agentSpans[i - 1];
+
+        const currentSys = extractSystemInstruction(currentSpan.io?.inputs);
+        const precedingSys = extractSystemInstruction(precedingSpan.io?.inputs);
+
+        if (currentSys && precedingSys && currentSys !== precedingSys) {
+          const eventId = currentSpan.attrEventId;
+          if (eventId) {
+            const event = this.eventData.get(eventId);
+            if (event) {
+              event.systemInstructionChanged = true;
+              event.precedingSystemInstruction = precedingSys;
+              event.currentSystemInstruction = currentSys;
+            }
           }
         }
       }