diff --git a/tests/test_web_concurrent_sessions.py b/tests/test_web_concurrent_sessions.py
index 16aa14b..0b3cac9 100644
--- a/tests/test_web_concurrent_sessions.py
+++ b/tests/test_web_concurrent_sessions.py
@@ -259,6 +259,26 @@ def test_plain_text_blocks_keep_history_order_and_stable_identity() -> None:
     assert '${item.timelineId || "text:legacy"}:content' in main
 
 
+def test_agent_graph_stops_animation_and_uses_one_update_transport() -> None:
+    graph = (Path(__file__).parents[1] / "web" / "vite-frontend" / "src" / "features" / "graphs" / "AgentGraphView.js").read_text(encoding="utf-8")
+    start_polling = graph[graph.index("  startPolling(sessionId)"):graph.index("  async _poll(sessionId)")]
+
+    assert "this.stopPolling();" in start_polling
+    assert "if (this._eventStream !== eventStream) return;" in start_polling
+    assert "eventStream.close();" in start_polling
+    assert start_polling.index("eventStream.close();") < start_polling.index("setInterval(")
+    assert "this._hasRunningNodes = false;" in start_polling
+    assert "cancelAnimationFrame(this._animationFrame);" in start_polling
+
+
+def test_orbital_indicator_skips_duplicate_state_renders() -> None:
+    indicator = (Path(__file__).parents[1] / "web" / "vite-frontend" / "src" / "components" / "mountOrbitalAgentIndicator.js").read_text(encoding="utf-8")
+
+    assert "let renderedState = null;" in indicator
+    assert "if (state === renderedState) return;" in indicator
+    assert "renderedState = state;" in indicator
+
+
 def test_step_cancellation_identifies_the_active_session_owner() -> None:
     content = _main_js()
     request_step_cancellation = content[
diff --git a/web/vite-frontend/src/components/mountOrbitalAgentIndicator.js b/web/vite-frontend/src/components/mountOrbitalAgentIndicator.js
index 5531c2a..6bd579a 100644
--- a/web/vite-frontend/src/components/mountOrbitalAgentIndicator.js
+++ b/web/vite-frontend/src/components/mountOrbitalAgentIndicator.js
@@ -7,12 +7,17 @@ import OrbitalAgentIndicator from "./OrbitalAgentIndicator.jsx";
 export function mountOrbitalAgentIndicator(target) {
   if (!target) return null;
   const root = createRoot(target);
-  const render = (state = "idle") => root.render(React.createElement(OrbitalAgentIndicator, {
-    state,
-    size: 18,
-    color: "var(--accent)",
-    title: `MatCreator is ${state}`,
-  }));
+  let renderedState = null;
+  const render = (state = "idle") => {
+    if (state === renderedState) return;
+    renderedState = state;
+    root.render(React.createElement(OrbitalAgentIndicator, {
+      state,
+      size: 18,
+      color: "var(--accent)",
+      title: `MatCreator is ${state}`,
+    }));
+  };
   render();
   return { render, unmount: () => root.unmount() };
 }
diff --git a/web/vite-frontend/src/features/chat/messageStream.js b/web/vite-frontend/src/features/chat/messageStream.js
index 38f8cae..ddf87b9 100644
--- a/web/vite-frontend/src/features/chat/messageStream.js
+++ b/web/vite-frontend/src/features/chat/messageStream.js
@@ -75,7 +75,7 @@ export function createMessageStreamController(deps) {
     renderStopStatus(request);
     request.controller.abort();
     updateAgentRunningStatus("working");
-    pollCancellationConfirmed(request.sessionId, request.owner);
+    void pollCancellationConfirmed(request);
   }
 
   async function send(message) {
@@ -160,8 +160,7 @@ export function createMessageStreamController(deps) {
               && response.response?.status === "ok") executionApprovedThisTurn = true;
           } else if (part.text) {
             updateAgentRunningStatus("thinking");
-            accumulatedText = mergeReplayedText(accumulatedText, part.text);
-            upsertTimelineText(timeline, compactRepeatedPrefixSnapshots(accumulatedText));
+            upsertTimelineText(timeline, part.text);
             if (!summaryTriggered && !state.summaryGeneratedFor.has(request.sessionId) && !state.sessionSummaries[request.sessionId]) {
               summaryTriggered = true;
               generateSessionSummary(request.sessionId, request.owner);
diff --git a/web/vite-frontend/src/features/graphs/AgentGraphView.js b/web/vite-frontend/src/features/graphs/AgentGraphView.js
index 21830ba..fce6ffc 100644
--- a/web/vite-frontend/src/features/graphs/AgentGraphView.js
+++ b/web/vite-frontend/src/features/graphs/AgentGraphView.js
@@ -914,11 +914,12 @@ export class AgentGraphView {
   }
 
   startPolling(sessionId) {
+    this.stopPolling();
     this._currentSessionId = sessionId;
-    this._poll(sessionId);
-    this._eventStream?.close();
-    this._eventStream = new EventSource(`/api/agent-graph/${encodeURIComponent(sessionId)}/events`);
-    this._eventStream.onmessage = (event) => {
+    void this._poll(sessionId);
+    const eventStream = new EventSource(`/api/agent-graph/${encodeURIComponent(sessionId)}/events`);
+    this._eventStream = eventStream;
+    eventStream.onmessage = (event) => {
       try {
         if (sessionId !== this._currentSessionId) return;
         this.update(JSON.parse(event.data));
@@ -927,8 +928,13 @@ export class AgentGraphView {
       }
     };
     // Keep a low-frequency fallback for deployments running an older web
-    // backend that does not yet expose the graph event endpoint.
-    this._eventStream.onerror = () => {
+    // backend that does not yet expose the graph event endpoint. Close the
+    // EventSource before starting it so browser reconnects cannot deliver the
+    // same snapshots alongside the fallback poller.
+    eventStream.onerror = () => {
+      if (this._eventStream !== eventStream) return;
+      eventStream.close();
+      this._eventStream = null;
       if (!this._pollInterval) this._pollInterval = setInterval(() => this._poll(sessionId), 2000);
     };
   }
@@ -940,6 +946,14 @@ export class AgentGraphView {
       clearInterval(this._pollInterval);
       this._pollInterval = null;
     }
+    // Polling owns the running-node animation lifecycle. A cancellation can
+    // stop updates while the last received snapshot still says "running";
+    // without clearing that stale flag the canvas redraw loop never ends.
+    this._hasRunningNodes = false;
+    this._activeEdges = [];
+    if (this._animationFrame !== null) cancelAnimationFrame(this._animationFrame);
+    this._animationFrame = null;
+    this._network?.redraw();
   }
 
   async _poll(sessionId) {