diff --git a/apps/web/src/components/Sidebar.logic.test.ts b/apps/web/src/components/Sidebar.logic.test.ts
index 669c805492bcc..71a4927d29f6e 100644
--- a/apps/web/src/components/Sidebar.logic.test.ts
+++ b/apps/web/src/components/Sidebar.logic.test.ts
@@ -38,6 +38,7 @@ import {
   sidebarFolderExpansionKeys,
 } from "./Sidebar.logic";
 import { scopeThreadRef, scopedThreadKey } from "@t3tools/client-runtime/environment";
+import type { EnvironmentConnectionPhase } from "@t3tools/client-runtime/connection";
 import {
   sortActiveThreadsByOrderKey,
   sortPinnedThreadsByOrderKey,
@@ -969,21 +970,68 @@ describe("Working shelf (beta)", () => {
     ).toBe(false);
   });
 
-  it.each([
-    ["connected", true, false],
-    ["connected", false, true],
-    ["connecting", false, false],
-    ["reconnecting", false, true],
-    ["offline", false, true],
-    ["error", false, true],
-    ["unsupported", false, true],
-    ["available", false, true],
-  ] as const)(
-    "lists threads outside the shelf on a %s environment: %s",
-    (phase, shellIsLive, disconnected) => {
-      expect(isSidebarEnvironmentDisconnected(phase, shellIsLive)).toBe(disconnected);
-    },
-  );
+  describe("isSidebarEnvironmentDisconnected", () => {
+    const follow = (
+      states: ReadonlyArray<readonly [EnvironmentConnectionPhase, boolean]>,
+    ): boolean[] => {
+      let disconnected = false;
+      return states.map(([phase, shellIsLive]) => {
+        disconnected = isSidebarEnvironmentDisconnected(phase, shellIsLive, disconnected);
+        return disconnected;
+      });
+    };
+
+    it.each(["reconnecting", "offline", "error", "unsupported", "available"] as const)(
+      "lists threads outside the shelf on a %s environment",
+      (phase) => {
+        expect(
+          follow([
+            ["connected", true],
+            [phase, false],
+          ]),
+        ).toEqual([false, true]);
+      },
+    );
+
+    it("keeps the shelf through the resync a window refocus starts on a live socket", () => {
+      expect(
+        follow([
+          ["connected", true],
+          ["connected", false],
+          ["connected", true],
+        ]),
+      ).toEqual([false, false, false]);
+    });
+
+    it("keeps threads out of the shelf after a reconnect until the shell is live", () => {
+      expect(
+        follow([
+          ["connected", true],
+          ["reconnecting", false],
+          ["connected", false],
+          ["connected", true],
+        ]),
+      ).toEqual([false, true, true, false]);
+      expect(
+        follow([
+          ["available", false],
+          ["connecting", false],
+          ["connected", false],
+          ["connected", true],
+        ]),
+      ).toEqual([true, true, true, false]);
+    });
+
+    it("keeps cached placement through a cold start", () => {
+      expect(
+        follow([
+          ["connecting", false],
+          ["connected", false],
+          ["connected", true],
+        ]),
+      ).toEqual([false, false, false]);
+    });
+  });
 
   it("lists a running thread outside the shelf while its environment is disconnected", () => {
     const thread = { ...idle, runtime, environmentId: localEnvironmentId };
diff --git a/apps/web/src/components/Sidebar.logic.ts b/apps/web/src/components/Sidebar.logic.ts
index 55cf694c2b79e..946c53ad6e42c 100644
--- a/apps/web/src/components/Sidebar.logic.ts
+++ b/apps/web/src/components/Sidebar.logic.ts
@@ -185,12 +185,16 @@ export function resolveSidebarThreadSection(input: {
   return "active";
 }
 
-// Keep cached placement on the first connection attempt, matching mobile's threadRouteIsHydrating.
+// Between a dropped connection and a live shell, placement holds. A first connection attempt keeps
+// the cached shelf, a reconnect keeps threads out until its resync lands, and the resync that
+// every window refocus starts on a healthy socket moves nothing.
 export function isSidebarEnvironmentDisconnected(
   phase: EnvironmentConnectionPhase,
   shellIsLive: boolean,
+  wasDisconnected: boolean,
 ): boolean {
-  return phase !== "connecting" && (phase !== "connected" || !shellIsLive);
+  if (phase === "connected" && shellIsLive) return false;
+  return phase === "connecting" || phase === "connected" ? wasDisconnected : true;
 }
 
 export function belongsInSidebarWorkingShelf<T extends { readonly environmentId: EnvironmentId }>(
diff --git a/apps/web/src/components/Sidebar.tsx b/apps/web/src/components/Sidebar.tsx
index deede26763fdd..f7bab0d1dc7bb 100644
--- a/apps/web/src/components/Sidebar.tsx
+++ b/apps/web/src/components/Sidebar.tsx
@@ -139,7 +139,6 @@ import { useNowMinute } from "../hooks/useNowMinute";
 import {
   useEnvironmentIdentities,
   useConnectedEnvironmentIds,
-  useEnvironmentConnectionSummaries,
   useEnvironmentMachines,
   usePrimaryEnvironmentId,
 } from "../state/environments";
@@ -151,7 +150,7 @@ import {
   useServerConfigs,
   useQuietThreadShells,
 } from "../state/entities";
-import { environmentPresentations } from "../state/presentation";
+import { environmentPresentations, environmentSummaries } from "../state/presentation";
 import { primaryServerKeybindingsAtom } from "../state/server";
 import { environmentProjects } from "../state/projects";
 import { threadEnvironment } from "../state/threads";
@@ -366,6 +365,30 @@ function scrollSidebarToTop(content: HTMLElement | null) {
   content?.closest("[data-slot=scroll-area-viewport]")?.scrollTo({ top: 0 });
 }
 
+let previousDisconnectedEnvironmentIds: ReadonlySet<EnvironmentId> = new Set();
+const disconnectedEnvironmentIdsAtom = Atom.make((get) => {
+  const liveShellEnvironmentIds = get(liveShellEnvironmentIdsAtom);
+  const next = new Set(
+    get(environmentSummaries.environmentsAtom)
+      .filter((environment) =>
+        isSidebarEnvironmentDisconnected(
+          environment.connectionState,
+          liveShellEnvironmentIds.has(environment.environmentId),
+          previousDisconnectedEnvironmentIds.has(environment.environmentId),
+        ),
+      )
+      .map((environment) => environment.environmentId),
+  );
+  if (
+    next.size === previousDisconnectedEnvironmentIds.size &&
+    [...next].every((environmentId) => previousDisconnectedEnvironmentIds.has(environmentId))
+  ) {
+    return previousDisconnectedEnvironmentIds;
+  }
+  previousDisconnectedEnvironmentIds = next;
+  return next;
+}).pipe(Atom.withLabel("web-sidebar-disconnected-environment-ids"));
+
 function threadShellKey(thread: Pick<SidebarThreadSummary, "environmentId" | "id">): string {
   return scopedThreadKey(scopeThreadRef(thread.environmentId, thread.id));
 }
@@ -441,18 +464,7 @@ function useSidebarThreads(input: {
   // Folders already separate the work, so boring mode has no Working shelf.
   const workingShelfEnabled =
     useClientSettings((s) => s.sidebarWorkingShelfEnabled) && folderGroups === null;
-  const environmentConnections = useEnvironmentConnectionSummaries();
-  const liveShellEnvironmentIds = useAtomValue(liveShellEnvironmentIdsAtom);
-  const disconnectedEnvironmentIds = new Set(
-    environmentConnections
-      .filter((environment) =>
-        isSidebarEnvironmentDisconnected(
-          environment.connectionState,
-          liveShellEnvironmentIds.has(environment.environmentId),
-        ),
-      )
-      .map((environment) => environment.environmentId),
-  );
+  const disconnectedEnvironmentIds = useAtomValue(disconnectedEnvironmentIdsAtom);
   const inboxReturnsVersion = useSyncExternalStore(
     inboxReturns.subscribe,
     inboxReturns.getSnapshot,
diff --git a/apps/web/src/state/environments.ts b/apps/web/src/state/environments.ts
index a35af5e094a00..0b2cab287d223 100644
--- a/apps/web/src/state/environments.ts
+++ b/apps/web/src/state/environments.ts
@@ -114,7 +114,3 @@ export function useEnvironmentMachines() {
 export function useConnectedEnvironmentIds() {
   return useAtomValue(environmentSummaries.connectedEnvironmentIdsAtom);
 }
-
-export function useEnvironmentConnectionSummaries() {
-  return useAtomValue(environmentSummaries.environmentsAtom);
-}