diff --git a/src/App.tsx b/src/App.tsx
index 7925cb3..5f9e615 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,5 +1,10 @@
-import { useMemo, useState } from "react";
-import { initialWorkspaces, selectWorkspace } from "./workspace";
+import { useReducer } from "react";
+import {
+  createInitialWorkspaceState,
+  selectActiveTab,
+  selectActiveWorkspace,
+  workspaceReducer,
+} from "./workspace";
 
 const sessions = [
   { id: "NW-042", status: "ONLINE", host: "ws-fin-042", user: "nora.chen", os: "Windows 11", address: "10.42.8.17", seen: "14s ago", tags: ["finance", "priority"] },
@@ -9,25 +14,19 @@ const sessions = [
 ];
 
 export function App() {
-  const [activeServerId, setActiveServerId] = useState(initialWorkspaces[0].id);
-  const [activeTabs, setActiveTabs] = useState<Record<string, string>>(
-    Object.fromEntries(initialWorkspaces.map((server) => [server.id, server.activeTabId])),
-  );
-  const server = useMemo(
-    () => selectWorkspace(initialWorkspaces, activeServerId) ?? initialWorkspaces[0],
-    [activeServerId],
-  );
-  const activeTab = server.tabs.find((tab) => tab.id === activeTabs[server.id]) ?? server.tabs[0];
+  const [workspace, dispatch] = useReducer(workspaceReducer, undefined, createInitialWorkspaceState);
+  const server = selectActiveWorkspace(workspace);
+  const activeTab = selectActiveTab(server);
 
   return (
     <main className="shell">
       <aside className="server-rail" aria-label="Teamserver 列表">
         <div className="brand">G</div>
-        {initialWorkspaces.map((item) => (
+        {workspace.serverOrder.map((serverId) => workspace.servers[serverId]).map((item) => (
           <button
             className={`server-button ${item.id === server.id ? "active" : ""}`}
             key={item.id}
-            onClick={() => setActiveServerId(item.id)}
+            onClick={() => dispatch({ type: "switchServer", serverId: item.id })}
             aria-label={`切换到 ${item.name}`}
             title={item.name}
           >
@@ -68,23 +67,23 @@ export function App() {
               aria-selected={tab.id === activeTab.id}
               className={tab.id === activeTab.id ? "active" : ""}
               key={tab.id}
-              onClick={() => setActiveTabs((tabs) => ({ ...tabs, [server.id]: tab.id }))}
-              title={`${tab.project} / ${tab.session}`}
+              onClick={() => dispatch({ type: "activateTab", serverId: server.id, tabId: tab.id })}
+              title={`${tab.context.project} / ${tab.context.session}`}
             >
               {tab.running && <span className="running" />}{tab.title}<span className="close">×</span>
             </button>
           ))}
         </div>
         <div className="contextbar" aria-label="锁定的操作上下文">
-          <span className="context-lock">◆ LOCKED</span>{server.name} <i>/</i> {activeTab.project} <i>/</i> <b>{activeTab.session}</b> <i>/</i> {activeTab.title}
+          <span className="context-lock">◆ LOCKED</span>{server.name} <i>/</i> {activeTab.context.project} <i>/</i> <b>{activeTab.context.session}</b> <i>/</i> {activeTab.title}
         </div>
         <article className="content">
           <div className="content-heading">
-            <div><h2>{activeTab.title}</h2><p>{activeTab.project} 中的 248 个 Session · 4 个实时更新</p></div>
+            <div><h2>{activeTab.title}</h2><p>{activeTab.context.project} 中的 248 个 Session · 4 个实时更新</p></div>
             <div className="heading-actions"><button className="secondary">导出视图</button><button className="primary">＋ 新建操作</button></div>
           </div>
           <div className="table-toolbar">
-            <label><span>⌕</span><input aria-label="筛选 Session" placeholder="筛选 Session…" /></label>
+            <label><span>⌕</span><input aria-label="筛选 Session" placeholder="筛选 Session…" value={server.filter} onChange={(event) => dispatch({ type: "setFilter", serverId: server.id, filter: event.target.value })} /></label>
             <button>状态：全部⌄</button><button>标签⌄</button><button>＋ 筛选</button>
             <span className="toolbar-spacer" /><button aria-label="调整列">☷ 列</button><button aria-label="更多操作">•••</button>
           </div>
diff --git a/src/workspace.test.ts b/src/workspace.test.ts
new file mode 100644
index 0000000..3a35a5b
--- /dev/null
+++ b/src/workspace.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from "vitest";
+import {
+  createInitialWorkspaceState,
+  selectActiveTab,
+  selectActiveWorkspace,
+  type WorkspaceAction,
+  workspaceReducer,
+} from "./workspace";
+
+describe("workspaceReducer", () => {
+  it("隔离每个 Teamserver 的导航、筛选与未读状态", () => {
+    const initial = createInitialWorkspaceState();
+    const actions: WorkspaceAction[] = [
+      { type: "navigate", serverId: "atlas", project: "Orchid", navigation: "Audit" },
+      { type: "setFilter", serverId: "atlas", filter: "status:online" },
+      { type: "setUnread", serverId: "atlas", unread: 0 },
+    ];
+    const changed = actions.reduce(workspaceReducer, initial);
+
+    expect(changed.servers.atlas).toMatchObject({ activeProject: "Orchid", navigation: "Audit", filter: "status:online", unread: 0 });
+    expect(changed.servers.ember).toMatchObject({ activeProject: "Sandbox", navigation: "Events", filter: "", unread: 5 });
+  });
+
+  it("切回 Teamserver 时恢复各自的激活标签", () => {
+    let state = createInitialWorkspaceState();
+    state = workspaceReducer(state, { type: "activateTab", serverId: "atlas", tabId: "nw-042" });
+    state = workspaceReducer(state, { type: "switchServer", serverId: "ember" });
+    state = workspaceReducer(state, { type: "activateTab", serverId: "ember", tabId: "sb-107" });
+    state = workspaceReducer(state, { type: "switchServer", serverId: "atlas" });
+
+    expect(selectActiveTab(selectActiveWorkspace(state)).id).toBe("nw-042");
+    expect(state.servers.ember.activeTabId).toBe("sb-107");
+  });
+
+  it("导航与重复 tab ID 均不能重定向已创建标签的上下文", () => {
+    let state = createInitialWorkspaceState();
+    const originalContext = state.servers.atlas.tabs[1].context;
+    state = workspaceReducer(state, { type: "navigate", serverId: "atlas", project: "Orchid", navigation: "Sessions" });
+    state = workspaceReducer(state, {
+      type: "openTab",
+      serverId: "atlas",
+      tab: { id: "nw-042", title: "被拒绝的替换", context: { serverId: "atlas", project: "Orchid", session: "OR-999" } },
+    });
+
+    expect(state.servers.atlas.tabs[1].context).toEqual(originalContext);
+    expect(state.servers.atlas.tabs[1].title).toBe("Session Overview");
+  });
+
+  it("退出等价于丢弃内存状态，新实例不恢复业务状态", () => {
+    const changed = workspaceReducer(createInitialWorkspaceState(), { type: "setFilter", serverId: "atlas", filter: "secret" });
+    const restarted = createInitialWorkspaceState();
+
+    expect(changed.servers.atlas.filter).toBe("secret");
+    expect(restarted.servers.atlas.filter).toBe("");
+    expect(restarted).not.toBe(changed);
+  });
+});
diff --git a/src/workspace.ts b/src/workspace.ts
index 5e55c3c..ceec88d 100644
--- a/src/workspace.ts
+++ b/src/workspace.ts
@@ -1,25 +1,46 @@
 export type ConnectionState = "CONNECTED" | "DEGRADED" | "RECONNECTING";
 
+export interface TabContext {
+  readonly serverId: string;
+  readonly project: string;
+  readonly session: string;
+}
+
 export interface OperationTab {
-  id: string;
-  project: string;
-  session: string;
-  title: string;
-  running?: boolean;
+  readonly id: string;
+  readonly context: TabContext;
+  readonly title: string;
+  readonly running?: boolean;
 }
 
 export interface TeamserverWorkspace {
-  id: string;
-  name: string;
-  shortName: string;
-  connection: ConnectionState;
-  unread: number;
-  activeProject: string;
+  readonly id: string;
+  readonly name: string;
+  readonly shortName: string;
+  readonly connection: ConnectionState;
+  readonly tabs: readonly OperationTab[];
   activeTabId: string;
-  tabs: OperationTab[];
+  activeProject: string;
+  navigation: string;
+  filter: string;
+  unread: number;
 }
 
-export const initialWorkspaces: TeamserverWorkspace[] = [
+export interface WorkspaceState {
+  activeServerId: string;
+  servers: Record<string, TeamserverWorkspace>;
+  serverOrder: readonly string[];
+}
+
+export type WorkspaceAction =
+  | { type: "switchServer"; serverId: string }
+  | { type: "activateTab"; serverId: string; tabId: string }
+  | { type: "navigate"; serverId: string; project: string; navigation: string }
+  | { type: "setFilter"; serverId: string; filter: string }
+  | { type: "setUnread"; serverId: string; unread: number }
+  | { type: "openTab"; serverId: string; tab: OperationTab };
+
+const seedWorkspaces: readonly TeamserverWorkspace[] = [
   {
     id: "atlas",
     name: "Atlas Teamserver",
@@ -27,11 +48,13 @@ export const initialWorkspaces: TeamserverWorkspace[] = [
     connection: "CONNECTED",
     unread: 2,
     activeProject: "Northwind",
+    navigation: "Sessions",
+    filter: "",
     activeTabId: "nw-sessions",
     tabs: [
-      { id: "nw-sessions", project: "Northwind", session: "All sessions", title: "Sessions" },
-      { id: "nw-042", project: "Northwind", session: "NW-042", title: "Session Overview" },
-      { id: "or-audit", project: "Orchid", session: "Project", title: "Audit", running: true },
+      { id: "nw-sessions", context: { serverId: "atlas", project: "Northwind", session: "All sessions" }, title: "Sessions" },
+      { id: "nw-042", context: { serverId: "atlas", project: "Northwind", session: "NW-042" }, title: "Session Overview" },
+      { id: "or-audit", context: { serverId: "atlas", project: "Orchid", session: "Project" }, title: "Audit", running: true },
     ],
   },
   {
@@ -41,17 +64,81 @@ export const initialWorkspaces: TeamserverWorkspace[] = [
     connection: "DEGRADED",
     unread: 5,
     activeProject: "Sandbox",
+    navigation: "Events",
+    filter: "",
     activeTabId: "sb-events",
     tabs: [
-      { id: "sb-events", project: "Sandbox", session: "Project", title: "Events" },
-      { id: "sb-107", project: "Sandbox", session: "SB-107", title: "Task Output", running: true },
+      { id: "sb-events", context: { serverId: "ember", project: "Sandbox", session: "Project" }, title: "Events" },
+      { id: "sb-107", context: { serverId: "ember", project: "Sandbox", session: "SB-107" }, title: "Task Output", running: true },
     ],
   },
 ];
 
-export function selectWorkspace(
-  workspaces: TeamserverWorkspace[],
-  workspaceId: string,
-): TeamserverWorkspace | undefined {
-  return workspaces.find(({ id }) => id === workspaceId);
+function cloneServer(server: TeamserverWorkspace): TeamserverWorkspace {
+  return {
+    ...server,
+    tabs: server.tabs.map((tab) => ({ ...tab, context: { ...tab.context } })),
+  };
+}
+
+/** 每次进程启动都从种子数据创建全新状态，不读取或写入任何持久化存储。 */
+export function createInitialWorkspaceState(): WorkspaceState {
+  return {
+    activeServerId: seedWorkspaces[0].id,
+    serverOrder: seedWorkspaces.map(({ id }) => id),
+    servers: Object.fromEntries(seedWorkspaces.map((server) => [server.id, cloneServer(server)])),
+  };
+}
+
+function updateServer(
+  state: WorkspaceState,
+  serverId: string,
+  update: (server: TeamserverWorkspace) => TeamserverWorkspace,
+): WorkspaceState {
+  const server = state.servers[serverId];
+  if (!server) return state;
+  const nextServer = update(server);
+  if (nextServer === server) return state;
+  return { ...state, servers: { ...state.servers, [serverId]: nextServer } };
+}
+
+export function workspaceReducer(state: WorkspaceState, action: WorkspaceAction): WorkspaceState {
+  switch (action.type) {
+    case "switchServer":
+      return state.servers[action.serverId] && action.serverId !== state.activeServerId
+        ? { ...state, activeServerId: action.serverId }
+        : state;
+    case "activateTab":
+      return updateServer(state, action.serverId, (server) =>
+        server.tabs.some(({ id }) => id === action.tabId) && server.activeTabId !== action.tabId
+          ? { ...server, activeTabId: action.tabId }
+          : server,
+      );
+    case "navigate":
+      return updateServer(state, action.serverId, (server) => ({
+        ...server,
+        activeProject: action.project,
+        navigation: action.navigation,
+      }));
+    case "setFilter":
+      return updateServer(state, action.serverId, (server) => ({ ...server, filter: action.filter }));
+    case "setUnread":
+      return updateServer(state, action.serverId, (server) => ({ ...server, unread: Math.max(0, action.unread) }));
+    case "openTab":
+      return updateServer(state, action.serverId, (server) => {
+        if (action.tab.context.serverId !== action.serverId) return server;
+        const existing = server.tabs.find(({ id }) => id === action.tab.id);
+        // 相同 ID 只能重新激活，不能借导航或重复创建改写其锁定上下文。
+        if (existing) return { ...server, activeTabId: existing.id };
+        return { ...server, tabs: [...server.tabs, action.tab], activeTabId: action.tab.id };
+      });
+  }
+}
+
+export function selectActiveWorkspace(state: WorkspaceState): TeamserverWorkspace {
+  return state.servers[state.activeServerId] ?? state.servers[state.serverOrder[0]];
+}
+
+export function selectActiveTab(server: TeamserverWorkspace): OperationTab {
+  return server.tabs.find(({ id }) => id === server.activeTabId) ?? server.tabs[0];
 }