diff --git a/packages/app/src/agent-stream/history-start-settle-scheduler.test.ts b/packages/app/src/agent-stream/history-start-settle-scheduler.test.ts
new file mode 100644
index 0000000000..d47650b057
--- /dev/null
+++ b/packages/app/src/agent-stream/history-start-settle-scheduler.test.ts
@@ -0,0 +1,42 @@
+import { describe, expect, it, vi } from "vitest";
+import { createHistoryStartSettleScheduler } from "./history-start-settle-scheduler";
+
+describe("history start settle scheduler", () => {
+  it("does not restart its countdown when geometry keeps changing", () => {
+    const frames = new Map<number, () => void>();
+    let nextFrameId = 1;
+    const onSettle = vi.fn();
+    const scheduler = createHistoryStartSettleScheduler({
+      settleFrames: 2,
+      requestFrame(callback) {
+        const id = nextFrameId;
+        nextFrameId += 1;
+        frames.set(id, callback);
+        return id;
+      },
+      cancelFrame: (id) => frames.delete(id),
+      isSettling: () => true,
+      isLoading: () => false,
+      onSettle,
+    });
+    const runNextFrame = () => {
+      const next = frames.entries().next().value as [number, () => void] | undefined;
+      if (!next) {
+        throw new Error("Expected a scheduled settlement frame");
+      }
+      frames.delete(next[0]);
+      next[1]();
+    };
+
+    scheduler.schedule();
+    scheduler.schedule();
+    runNextFrame();
+    scheduler.schedule();
+    runNextFrame();
+    scheduler.schedule();
+    runNextFrame();
+
+    expect(onSettle).toHaveBeenCalledTimes(1);
+    expect(frames.size).toBe(0);
+  });
+});
diff --git a/packages/app/src/agent-stream/history-start-settle-scheduler.ts b/packages/app/src/agent-stream/history-start-settle-scheduler.ts
new file mode 100644
index 0000000000..6c93472fca
--- /dev/null
+++ b/packages/app/src/agent-stream/history-start-settle-scheduler.ts
@@ -0,0 +1,50 @@
+export interface HistoryStartSettleScheduler {
+  schedule(): void;
+  cancel(): void;
+}
+
+export function createHistoryStartSettleScheduler(input: {
+  settleFrames: number;
+  requestFrame: (callback: () => void) => number;
+  cancelFrame: (id: number) => void;
+  isSettling: () => boolean;
+  isLoading: () => boolean;
+  onSettle: () => void;
+}): HistoryStartSettleScheduler {
+  let frameId: number | null = null;
+  let remainingFrames = 0;
+
+  const tick = () => {
+    if (!input.isSettling()) {
+      frameId = null;
+      remainingFrames = 0;
+      return;
+    }
+    if (input.isLoading() || remainingFrames > 0) {
+      if (!input.isLoading()) {
+        remainingFrames -= 1;
+      }
+      frameId = input.requestFrame(tick);
+      return;
+    }
+    frameId = null;
+    input.onSettle();
+  };
+
+  return {
+    schedule() {
+      if (frameId !== null) {
+        return;
+      }
+      remainingFrames = input.settleFrames;
+      frameId = input.requestFrame(tick);
+    },
+    cancel() {
+      if (frameId !== null) {
+        input.cancelFrame(frameId);
+      }
+      frameId = null;
+      remainingFrames = 0;
+    },
+  };
+}
diff --git a/packages/app/src/agent-stream/strategy-native.tsx b/packages/app/src/agent-stream/strategy-native.tsx
index 09948b354d..cb802918c8 100644
--- a/packages/app/src/agent-stream/strategy-native.tsx
+++ b/packages/app/src/agent-stream/strategy-native.tsx
@@ -41,6 +41,10 @@ import {
   type HistoryStartPaginationInput,
   type HistoryStartPaginationTransition,
 } from "./history-start-pagination";
+import {
+  createHistoryStartSettleScheduler,
+  type HistoryStartSettleScheduler,
+} from "./history-start-settle-scheduler";
 
 const DEFAULT_MAINTAIN_VISIBLE_CONTENT_POSITION = Object.freeze({
   minIndexForVisible: 0,
@@ -127,7 +131,7 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     createHistoryStartPaginationState,
   );
   const historyStartPaginationStateRef = useRef(historyStartPaginationState);
-  const historyStartSettleFrameIdRef = useRef<number | null>(null);
+  const historyStartSettleSchedulerRef = useRef<HistoryStartSettleScheduler | null>(null);
 
   const historyItems = useMemo(() => {
     if (segments.historyVirtualized.length === 0) {
@@ -183,7 +187,7 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
         }
         void (async () => {
           const started = await onNearHistoryStart();
-          if (started !== false) {
+          if (started === true) {
             return;
           }
           applyHistoryStartPaginationTransition({
@@ -205,30 +209,25 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     applyHistoryStartPaginationTransition(transition);
   });
   const scheduleHistoryStartSettle = useStableEvent(() => {
-    const pendingFrame = historyStartSettleFrameIdRef.current;
-    if (pendingFrame !== null) {
-      cancelAnimationFrame(pendingFrame);
+    let scheduler = historyStartSettleSchedulerRef.current;
+    if (!scheduler) {
+      scheduler = createHistoryStartSettleScheduler({
+        settleFrames: HISTORY_START_SETTLE_FRAMES,
+        requestFrame: requestAnimationFrame,
+        cancelFrame: cancelAnimationFrame,
+        isSettling: () => historyStartPaginationStateRef.current.status === "settling",
+        isLoading: () => getHistoryStartPaginationInput().isLoadingOlderHistory,
+        onSettle: () => {
+          const transition = settleHistoryStartPagination(
+            historyStartPaginationStateRef.current,
+            getHistoryStartPaginationInput(),
+          );
+          applyHistoryStartPaginationTransition(transition);
+        },
+      });
+      historyStartSettleSchedulerRef.current = scheduler;
     }
-    let remainingFrames = HISTORY_START_SETTLE_FRAMES;
-    const settle = () => {
-      if (historyStartPaginationStateRef.current.status !== "settling") {
-        historyStartSettleFrameIdRef.current = null;
-        return;
-      }
-      const input = getHistoryStartPaginationInput();
-      if (input.isLoadingOlderHistory || remainingFrames > 0) {
-        remainingFrames -= input.isLoadingOlderHistory ? 0 : 1;
-        historyStartSettleFrameIdRef.current = requestAnimationFrame(settle);
-        return;
-      }
-      historyStartSettleFrameIdRef.current = null;
-      const transition = settleHistoryStartPagination(
-        historyStartPaginationStateRef.current,
-        input,
-      );
-      applyHistoryStartPaginationTransition(transition);
-    };
-    historyStartSettleFrameIdRef.current = requestAnimationFrame(settle);
+    scheduler.schedule();
   });
 
   const clearNativeViewportSettling = useCallback(() => {
@@ -339,11 +338,8 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     return () => {
       cancelAnimationFrame(frame);
       clearPendingUserScrollEnd();
-      const settleFrame = historyStartSettleFrameIdRef.current;
-      if (settleFrame !== null) {
-        historyStartSettleFrameIdRef.current = null;
-        cancelAnimationFrame(settleFrame);
-      }
+      historyStartSettleSchedulerRef.current?.cancel();
+      historyStartSettleSchedulerRef.current = null;
     };
   }, [agentId, clearNativeViewportSettling, clearPendingUserScrollEnd, evaluateHistoryStart]);
 
diff --git a/packages/app/src/agent-stream/strategy-web.test.tsx b/packages/app/src/agent-stream/strategy-web.test.tsx
index 99a3a7ab11..3ef54b1c91 100644
--- a/packages/app/src/agent-stream/strategy-web.test.tsx
+++ b/packages/app/src/agent-stream/strategy-web.test.tsx
@@ -130,7 +130,7 @@ describe("createWebStreamStrategy", () => {
             routeBottomAnchorRequest: null,
             isAuthoritativeHistoryReady: true,
             onNearBottomChange: vi.fn(),
-            onNearHistoryStart: vi.fn(),
+            onNearHistoryStart: vi.fn().mockReturnValue(true),
             isLoadingOlderHistory: false,
             hasOlderHistory: false,
             olderHistoryProgressKey: null,
@@ -174,7 +174,7 @@ describe("createWebStreamStrategy", () => {
       routeBottomAnchorRequest: null,
       isAuthoritativeHistoryReady: true,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart: vi.fn(),
+      onNearHistoryStart: vi.fn().mockReturnValue(true),
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,
@@ -230,7 +230,7 @@ describe("createWebStreamStrategy", () => {
           routeBottomAnchorRequest: null,
           isAuthoritativeHistoryReady: true,
           onNearBottomChange: vi.fn(),
-          onNearHistoryStart: vi.fn(),
+          onNearHistoryStart: vi.fn().mockReturnValue(true),
           isLoadingOlderHistory: false,
           hasOlderHistory: false,
           olderHistoryProgressKey: null,
@@ -296,7 +296,7 @@ describe("createWebStreamStrategy", () => {
     });
     const strategy = createWebStreamStrategy({ isMobileBreakpoint: true });
     const viewportRef = React.createRef<StreamViewportHandle>();
-    const onNearHistoryStart = vi.fn();
+    const onNearHistoryStart = vi.fn().mockReturnValue(true);
     const renderInput = {
       agentId: "agent",
       boundary: {
@@ -370,10 +370,10 @@ describe("createWebStreamStrategy", () => {
     expect(onNearHistoryStart).not.toHaveBeenCalled();
   });
 
-  it("retries a skipped history request when the user scrolls up in a short timeline", async () => {
+  it("retries when a history callback does not start a request", async () => {
     const strategy = createWebStreamStrategy({ isMobileBreakpoint: true });
     const viewportRef = React.createRef<StreamViewportHandle>();
-    const onNearHistoryStart = vi.fn(async () => false);
+    const onNearHistoryStart = vi.fn(async () => undefined);
     const renderInput: StreamRenderInput = {
       agentId: "agent",
       segments: {
@@ -392,7 +392,7 @@ describe("createWebStreamStrategy", () => {
       routeBottomAnchorRequest: null,
       isAuthoritativeHistoryReady: true,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart,
+      onNearHistoryStart: onNearHistoryStart as unknown as StreamRenderInput["onNearHistoryStart"],
       isLoadingOlderHistory: false,
       hasOlderHistory: true,
       olderHistoryProgressKey: "epoch-1:20",
@@ -449,7 +449,7 @@ describe("createWebStreamStrategy", () => {
     );
     const strategy = createWebStreamStrategy({ isMobileBreakpoint: true });
     const viewportRef = React.createRef<StreamViewportHandle>();
-    const onNearHistoryStart = vi.fn();
+    const onNearHistoryStart = vi.fn().mockReturnValue(true);
     const initialHistory = Array.from({ length: 20 }, (_, index) => userMessage(index + 60));
     const renderInput: StreamRenderInput = {
       agentId: "agent",
@@ -566,7 +566,7 @@ describe("createWebStreamStrategy", () => {
       viewportRef,
       routeBottomAnchorRequest,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart: vi.fn(),
+      onNearHistoryStart: vi.fn().mockReturnValue(true),
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,
@@ -674,7 +674,7 @@ describe("createWebStreamStrategy", () => {
       viewportRef,
       routeBottomAnchorRequest,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart: vi.fn(),
+      onNearHistoryStart: vi.fn().mockReturnValue(true),
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,
@@ -771,7 +771,7 @@ describe("createWebStreamStrategy", () => {
       viewportRef,
       routeBottomAnchorRequest,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart: vi.fn(),
+      onNearHistoryStart: vi.fn().mockReturnValue(true),
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,
@@ -870,7 +870,7 @@ describe("createWebStreamStrategy", () => {
       viewportRef,
       routeBottomAnchorRequest: null,
       onNearBottomChange: vi.fn(),
-      onNearHistoryStart: vi.fn(),
+      onNearHistoryStart: vi.fn().mockReturnValue(true),
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,
diff --git a/packages/app/src/agent-stream/strategy-web.tsx b/packages/app/src/agent-stream/strategy-web.tsx
index 0c6f79b228..1001754d2d 100644
--- a/packages/app/src/agent-stream/strategy-web.tsx
+++ b/packages/app/src/agent-stream/strategy-web.tsx
@@ -264,7 +264,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
       const requestedProgressKey = olderHistoryProgressKey;
       void (async () => {
         const started = await onNearHistoryStart();
-        if (started !== false) {
+        if (started === true) {
           return;
         }
         applyHistoryStartPaginationTransition({
diff --git a/packages/app/src/agent-stream/strategy.ts b/packages/app/src/agent-stream/strategy.ts
index 12ded1aecd..15836f623c 100644
--- a/packages/app/src/agent-stream/strategy.ts
+++ b/packages/app/src/agent-stream/strategy.ts
@@ -69,7 +69,7 @@ export interface StreamRenderInput {
   routeBottomAnchorRequest: BottomAnchorRouteRequest | null;
   isAuthoritativeHistoryReady: boolean;
   onNearBottomChange: (value: boolean) => void;
-  onNearHistoryStart: () => void | Promise<boolean>;
+  onNearHistoryStart: () => boolean | Promise<boolean>;
   isLoadingOlderHistory: boolean;
   hasOlderHistory: boolean;
   olderHistoryProgressKey: string | null;
diff --git a/packages/app/src/agent-stream/view.tsx b/packages/app/src/agent-stream/view.tsx
index 0d6bde3c08..63308e56b3 100644
--- a/packages/app/src/agent-stream/view.tsx
+++ b/packages/app/src/agent-stream/view.tsx
@@ -77,6 +77,7 @@ import {
   type BottomAnchorLocalRequest,
   type BottomAnchorRouteRequest,
 } from "./bottom-anchor-controller";
+import { createAssistantImageOccurrenceKey } from "@/assistant-image/acquisition-cache";
 import {
   AssistantFileLinkResolverProvider,
   normalizeInlinePathTarget,
@@ -250,7 +251,7 @@ export interface AgentStreamViewProps {
     hasOlder: boolean;
     isLoadingOlder: boolean;
     progressKey: string | null;
-    onLoadOlder: () => void;
+    onLoadOlder: () => boolean | Promise<boolean>;
   };
 }
 
@@ -694,7 +695,7 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
             toast={toast}
           >
             <AssistantMessage
-              occurrenceKey={item.id}
+              occurrenceKey={createAssistantImageOccurrenceKey({ agentId, itemId: item.id })}
               message={item.text}
               timestamp={item.timestamp.getTime()}
               workspaceRoot={workspaceRoot}
@@ -705,7 +706,7 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
           </AssistantFileLinkResolverProvider>
         );
       },
-      [client, handleInlinePathPress, resolvedServerId, toast, workspaceRoot],
+      [agentId, client, handleInlinePathPress, resolvedServerId, toast, workspaceRoot],
     );
 
     const renderThoughtItem = useCallback(
diff --git a/packages/app/src/assistant-image/acquisition-cache.test.ts b/packages/app/src/assistant-image/acquisition-cache.test.ts
index 2b0ee9f675..099f88caee 100644
--- a/packages/app/src/assistant-image/acquisition-cache.test.ts
+++ b/packages/app/src/assistant-image/acquisition-cache.test.ts
@@ -3,6 +3,7 @@ import {
   createAssistantImageAcquisitionCache,
   createAssistantImageFileAcquisitionKey,
   createAssistantImageFilePreviewAttachmentId,
+  createAssistantImageOccurrenceKey,
 } from "./acquisition-cache";
 
 describe("assistant image acquisition cache", () => {
@@ -90,6 +91,7 @@ describe("assistant image acquisition cache", () => {
 
   it("scopes persisted file previews to the rendered message occurrence", () => {
     const first = createAssistantImageFilePreviewAttachmentId({
+      serverId: "server-1",
       occurrenceKey: "message-1:image-1",
       mimeType: "image/png",
       path: "/workspace/screenshot.png",
@@ -98,6 +100,7 @@ describe("assistant image acquisition cache", () => {
       contentLength: 512,
     });
     const second = createAssistantImageFilePreviewAttachmentId({
+      serverId: "server-1",
       occurrenceKey: "message-2:image-1",
       mimeType: "image/png",
       path: "/workspace/screenshot.png",
@@ -109,6 +112,13 @@ describe("assistant image acquisition cache", () => {
     expect(second).not.toBe(first);
   });
 
+  it("scopes message occurrences to their agent", () => {
+    const first = createAssistantImageOccurrenceKey({ agentId: "agent-1", itemId: "message-1" });
+    const second = createAssistantImageOccurrenceKey({ agentId: "agent-2", itemId: "message-1" });
+
+    expect(second).not.toBe(first);
+  });
+
   it("retains successful values until their cache entry is evicted", async () => {
     const retained: string[] = [];
     const released: string[] = [];
diff --git a/packages/app/src/assistant-image/acquisition-cache.ts b/packages/app/src/assistant-image/acquisition-cache.ts
index 32f0586cce..6d21379bff 100644
--- a/packages/app/src/assistant-image/acquisition-cache.ts
+++ b/packages/app/src/assistant-image/acquisition-cache.ts
@@ -5,7 +5,15 @@ export interface AssistantImageAcquisitionCache<T> {
   size(): number;
 }
 
+export function createAssistantImageOccurrenceKey(input: {
+  agentId: string;
+  itemId: string;
+}): string {
+  return `${input.agentId}:${input.itemId}`;
+}
+
 export function createAssistantImageFilePreviewAttachmentId(input: {
+  serverId?: string;
   occurrenceKey: string;
   mimeType: string;
   path: string;
@@ -19,7 +27,7 @@ export function createAssistantImageFilePreviewAttachmentId(input: {
     size: input.size,
     modifiedAt: input.modifiedAt,
     contentLength: input.contentLength,
-    contentKey: input.occurrenceKey,
+    contentKey: `${input.serverId ?? "unknown-server"}:${input.occurrenceKey}`,
   });
 }
 
diff --git a/packages/app/src/assistant-image/use-assistant-image.ts b/packages/app/src/assistant-image/use-assistant-image.ts
index 6125342e90..e2955669d0 100644
--- a/packages/app/src/assistant-image/use-assistant-image.ts
+++ b/packages/app/src/assistant-image/use-assistant-image.ts
@@ -157,6 +157,7 @@ function createFileAcquisition(input: {
       }
       return await persistAttachmentFromBytes({
         id: createAssistantImageFilePreviewAttachmentId({
+          serverId: input.serverId,
           occurrenceKey: input.occurrenceKey,
           mimeType: file.mime,
           path: file.path || resolution.path,
diff --git a/packages/app/src/panels/provider-subagent-panel.tsx b/packages/app/src/panels/provider-subagent-panel.tsx
index a5bac3b7bf..12558a2ed9 100644
--- a/packages/app/src/panels/provider-subagent-panel.tsx
+++ b/packages/app/src/panels/provider-subagent-panel.tsx
@@ -104,10 +104,12 @@ function ProviderSubagentPanel() {
       .catch(() => undefined);
   }, [client, serverId, supported, target.parentAgentId, target.subagentId]);
 
-  const loadOlder = useCallback(() => {
-    if (!client || !supported || isLoadingOlder || !timeline?.hasOlder || !timeline.epoch) return;
+  const loadOlder = useCallback((): boolean => {
+    if (!client || !supported || isLoadingOlder || !timeline?.hasOlder || !timeline.epoch) {
+      return false;
+    }
     const firstSeq = timeline.rows.size ? Math.min(...timeline.rows.keys()) : null;
-    if (firstSeq === null) return;
+    if (firstSeq === null) return false;
     setIsLoadingOlder(true);
     void client
       .fetchProviderSubagentTimeline(target.parentAgentId, target.subagentId, {
@@ -121,6 +123,7 @@ function ProviderSubagentPanel() {
       })
       .catch(() => undefined)
       .finally(() => setIsLoadingOlder(false));
+    return true;
   }, [
     client,
     isLoadingOlder,