diff --git a/packages/app/src/components/ui/floating-panel-hosts.test.ts b/packages/app/src/components/ui/floating-panel-hosts.test.ts
new file mode 100644
index 0000000000..a4b52d3a2c
--- /dev/null
+++ b/packages/app/src/components/ui/floating-panel-hosts.test.ts
@@ -0,0 +1,65 @@
+import { describe, expect, it } from "vitest";
+import {
+  createFloatingPanelHosts,
+  type FloatingPanelHostRect,
+  type MeasurableFloatingPanelHost,
+} from "./floating-panel-hosts";
+
+function createHost(rect: FloatingPanelHostRect): MeasurableFloatingPanelHost {
+  return {
+    measureInWindow: (callback) => callback(rect.x, rect.y, rect.width, rect.height),
+  };
+}
+
+const WORKSPACE_RECT: FloatingPanelHostRect = { x: 10, y: 20, width: 800, height: 600 };
+const RETAINED_VIEWPORT: FloatingPanelHostRect = { x: 0, y: 0, width: 1200, height: 900 };
+
+describe("floating panel hosts", () => {
+  it("measures the newest host registered under the name", async () => {
+    const hosts = createFloatingPanelHosts();
+    hosts.register("workspace", createHost(WORKSPACE_RECT));
+    hosts.register("workspace", createHost(RETAINED_VIEWPORT));
+
+    expect(await hosts.measure("workspace")).toEqual(RETAINED_VIEWPORT);
+  });
+
+  it("keeps measuring a survivor after the newest host unregisters", async () => {
+    const hosts = createFloatingPanelHosts();
+    const unregisterSurvivor = hosts.register("workspace", createHost(WORKSPACE_RECT));
+    const unregisterNewest = hosts.register("workspace", createHost(RETAINED_VIEWPORT));
+
+    unregisterNewest();
+
+    expect(await hosts.measure("workspace")).toEqual(WORKSPACE_RECT);
+    unregisterSurvivor();
+  });
+
+  it("returns null once every host under the name is gone", async () => {
+    const hosts = createFloatingPanelHosts();
+    const unregisterFirst = hosts.register("workspace", createHost(WORKSPACE_RECT));
+    const unregisterSecond = hosts.register("workspace", createHost(RETAINED_VIEWPORT));
+
+    unregisterFirst();
+    unregisterSecond();
+
+    expect(await hosts.measure("workspace")).toBeNull();
+  });
+
+  it("skips hosts that are not laid out", async () => {
+    const hosts = createFloatingPanelHosts();
+    hosts.register("workspace", createHost(WORKSPACE_RECT));
+    hosts.register("workspace", createHost({ x: 0, y: 0, width: 0, height: 0 }));
+
+    expect(await hosts.measure("workspace")).toEqual(WORKSPACE_RECT);
+  });
+
+  it("ignores a repeated unregister of the same host", async () => {
+    const hosts = createFloatingPanelHosts();
+    const unregister = hosts.register("workspace", createHost(WORKSPACE_RECT));
+
+    unregister();
+    unregister();
+
+    expect(await hosts.measure("workspace")).toBeNull();
+  });
+});
diff --git a/packages/app/src/components/ui/floating-panel-hosts.ts b/packages/app/src/components/ui/floating-panel-hosts.ts
new file mode 100644
index 0000000000..88451b1ebc
--- /dev/null
+++ b/packages/app/src/components/ui/floating-panel-hosts.ts
@@ -0,0 +1,57 @@
+export interface FloatingPanelHostRect {
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+}
+
+export interface MeasurableFloatingPanelHost {
+  measureInWindow(callback: (x: number, y: number, width: number, height: number) => void): void;
+}
+
+export interface FloatingPanelHosts<T extends MeasurableFloatingPanelHost> {
+  register(name: string, host: T): () => void;
+  measure(name: string): Promise<FloatingPanelHostRect | null>;
+}
+
+function measureHost(host: MeasurableFloatingPanelHost): Promise<FloatingPanelHostRect> {
+  return new Promise((resolve) => {
+    host.measureInWindow((x, y, width, height) => resolve({ x, y, width, height }));
+  });
+}
+
+/**
+ * Hosts are addressed by name, and one name can have several live hosts: a workspace
+ * screen mounts its own host while retained copies of that screen stay mounted. Track
+ * every host so unmounting one leaves the others measurable.
+ */
+export function createFloatingPanelHosts<
+  T extends MeasurableFloatingPanelHost,
+>(): FloatingPanelHosts<T> {
+  const hostsByName = new Map<string, T[]>();
+
+  function register(name: string, host: T): () => void {
+    const hosts = hostsByName.get(name) ?? [];
+    hostsByName.set(name, hosts);
+    hosts.push(host);
+
+    return () => {
+      const index = hosts.indexOf(host);
+      if (index === -1) return;
+      hosts.splice(index, 1);
+      if (hosts.length === 0 && hostsByName.get(name) === hosts) {
+        hostsByName.delete(name);
+      }
+    };
+  }
+
+  async function measure(name: string): Promise<FloatingPanelHostRect | null> {
+    const hosts = hostsByName.get(name);
+    if (!hosts || hosts.length === 0) return null;
+
+    const rects = await Promise.all(hosts.toReversed().map(measureHost));
+    return rects.find((rect) => rect.width > 0 && rect.height > 0) ?? rects[0];
+  }
+
+  return { register, measure };
+}
diff --git a/packages/app/src/components/ui/floating-panel-portal.tsx b/packages/app/src/components/ui/floating-panel-portal.tsx
index 21ea94a03f..e19e1a5575 100644
--- a/packages/app/src/components/ui/floating-panel-portal.tsx
+++ b/packages/app/src/components/ui/floating-panel-portal.tsx
@@ -8,32 +8,21 @@ import {
 } from "react";
 import { StyleSheet, View } from "react-native";
 import { PortalHost } from "@gorhom/portal";
+import {
+  createFloatingPanelHosts,
+  type FloatingPanelHostRect,
+} from "@/components/ui/floating-panel-hosts";
 
 export const DEFAULT_FLOATING_PANEL_PORTAL_HOST = "content-floating-panels";
 
 const FloatingPanelPortalHostNameContext = createContext(DEFAULT_FLOATING_PANEL_PORTAL_HOST);
 
-interface Rect {
-  x: number;
-  y: number;
-  width: number;
-  height: number;
-}
+const portalHosts = createFloatingPanelHosts<View>();
 
-const portalHostElements = new Map<string, View>();
-
-function measureElement(element: View): Promise<Rect> {
-  return new Promise((resolve) => {
-    element.measureInWindow((x, y, width, height) => {
-      resolve({ x, y, width, height });
-    });
-  });
-}
-
-export function measureFloatingPanelPortalHost(name: string): Promise<Rect | null> {
-  const element = portalHostElements.get(name);
-  if (!element) return Promise.resolve(null);
-  return measureElement(element);
+export function measureFloatingPanelPortalHost(
+  name: string,
+): Promise<FloatingPanelHostRect | null> {
+  return portalHosts.measure(name);
 }
 
 export function FloatingPanelPortalHostNameProvider({
@@ -64,12 +53,7 @@ export function FloatingPanelPortalHost({
   useEffect(() => {
     const host = hostRef.current;
     if (!host) return undefined;
-    portalHostElements.set(name, host);
-    return () => {
-      if (portalHostElements.get(name) === host) {
-        portalHostElements.delete(name);
-      }
-    };
+    return portalHosts.register(name, host);
   }, [name]);
 
   return (