diff --git a/web/src/components/repeater/repeater-editor.tsx b/web/src/components/repeater/repeater-editor.tsx
index 4cab00a..b3a0e17 100644
--- a/web/src/components/repeater/repeater-editor.tsx
+++ b/web/src/components/repeater/repeater-editor.tsx
@@ -1,7 +1,5 @@
 "use client";
 
-import * as React from "react";
-
 import { SendIcon } from "lucide-react";
 import { toast } from "sonner";
 
@@ -24,35 +22,23 @@ const METHODS = ["GET", "POST", "PUT", "PATCH", "DELETE", "HEAD", "OPTIONS"];
 export function RepeaterEditor({ tab }: { tab: RepeaterTab }) {
   const { method, url, headersText, body, useProxy, insecure, response, history } = tab;
   const updateTab = useRepeaterStore((state) => state.updateTab);
-  const recordSend = useRepeaterStore((state) => state.recordSend);
+  const busy = useRepeaterStore((state) => state.inflight[tab.id] !== undefined);
   const setMethod = (method: string) => updateTab(tab.id, { method });
   const setURL = (url: string) => updateTab(tab.id, { url });
   const setHeadersText = (headersText: string) => updateTab(tab.id, { headersText });
   const setBody = (body: string) => updateTab(tab.id, { body });
   const setUseProxy = (useProxy: boolean) => updateTab(tab.id, { useProxy });
   const setInsecure = (insecure: boolean) => updateTab(tab.id, { insecure });
-  const [busy, setBusy] = React.useState(false);
-  const generation = React.useRef(0);
-  const sending = React.useRef(false);
-  React.useEffect(
-    () => () => {
-      generation.current += 1;
-      sending.current = false;
-    },
-    [],
-  );
-
   async function send() {
-    if (sending.current) return;
+    const store = useRepeaterStore.getState();
+    if (store.inflight[tab.id] !== undefined) return;
     const target = url.trim();
     if (!target) {
       toast.error("请填写 URL");
       return;
     }
-    const requestGeneration = ++generation.current;
-    sending.current = true;
-    setBusy(true);
-    updateTab(tab.id, { response: null });
+    const requestGeneration = store.beginSend(tab.id);
+    if (requestGeneration === undefined) return;
     try {
       const result = await api.repeaterSend({
         method,
@@ -62,8 +48,7 @@ export function RepeaterEditor({ tab }: { tab: RepeaterTab }) {
         use_recording_proxy: useProxy,
         insecure_skip_verify: insecure,
       });
-      if (requestGeneration !== generation.current) return;
-      recordSend(tab.id, {
+      store.completeSend(tab.id, requestGeneration, {
         id: newId(),
         method,
         url: target,
@@ -75,12 +60,9 @@ export function RepeaterEditor({ tab }: { tab: RepeaterTab }) {
         at: new Date().toISOString(),
       });
     } catch (error) {
-      if (requestGeneration === generation.current) toast.error((error as Error).message);
+      if (store.isCurrentSend(tab.id, requestGeneration)) toast.error((error as Error).message);
     } finally {
-      if (requestGeneration === generation.current) {
-        sending.current = false;
-        setBusy(false);
-      }
+      store.clearInflight(tab.id, requestGeneration);
     }
   }
 
diff --git a/web/src/components/repeater/repeater-state.ts b/web/src/components/repeater/repeater-state.ts
index 5b94f86..8279147 100644
--- a/web/src/components/repeater/repeater-state.ts
+++ b/web/src/components/repeater/repeater-state.ts
@@ -5,7 +5,9 @@ import type { RepeaterInitial } from "./repeater-http";
 export const STORAGE_KEY = "artex_repeater_workspace_v1";
 export const MAX_HISTORY = 20;
 export const MAX_RESPONSE_CHARS = 256 * 1024;
-export const MAX_STORAGE_BYTES = 2.5 * 1024 * 1024;
+// Count UTF-16 storage bytes (two per code unit), reserving headroom below 5 MiB
+// for the storage key and other browser preferences.
+export const MAX_STORAGE_BYTES = 4 * 1024 * 1024;
 export const DEFAULT_GROUP_ID = "default";
 
 export type RepeaterHistoryEntry = {
@@ -119,7 +121,7 @@ export function serializeWorkspace(workspace: RepeaterWorkspace, maxBytes = MAX_
     })),
   };
   let json = JSON.stringify(saved);
-  const size = () => new TextEncoder().encode(json).length;
+  const size = () => json.length * 2;
   // Remove the oldest send globally, including its request snapshot, first.
   const oldest = saved.tabs
     .flatMap((tab) => tab.history.map((entry) => ({ tab, entry })))
diff --git a/web/src/components/repeater/repeater-store.test.mjs b/web/src/components/repeater/repeater-store.test.mjs
index 40d44c1..a0f47c9 100644
--- a/web/src/components/repeater/repeater-store.test.mjs
+++ b/web/src/components/repeater/repeater-store.test.mjs
@@ -26,6 +26,8 @@ const {
   parseHeadersText,
   setHostHeader,
 } = require("./repeater-http.ts");
+const { flush, useRepeaterStore } = require("./repeater-store.ts");
+const { toast } = require("sonner");
 
 const response = (body = "ok") => ({
   status: 200,
@@ -134,7 +136,7 @@ test("budget removes globally oldest history first then strips responses, preser
   const workspace = addTab(defaultWorkspace());
   workspace.tabs[0].history = [entry(3), entry(1)];
   workspace.tabs[1].history = [entry(4), entry(2)];
-  const limit = Buffer.byteLength(serializeWorkspace(workspace)) - Buffer.byteLength(JSON.stringify(entry(1))) - 1;
+  const limit = (serializeWorkspace(workspace).length - JSON.stringify(entry(1)).length - 1) * 2;
   const saved = JSON.parse(serializeWorkspace(workspace, limit));
   assert.deepEqual(
     saved.tabs.map((tab) => tab.history.map((item) => item.id)),
@@ -154,7 +156,189 @@ test("budget removes globally oldest history first then strips responses, preser
     tab.response = response("中".repeat(MAX_RESPONSE_CHARS));
     tab.history = [entry(1, "中".repeat(MAX_RESPONSE_CHARS))];
   }
-  assert.ok(Buffer.byteLength(serializeWorkspace(large)) <= MAX_STORAGE_BYTES);
+  assert.ok(serializeWorkspace(large).length * 2 <= MAX_STORAGE_BYTES);
+});
+
+test("storage cap counts UTF-16 bytes for ASCII, Chinese and surrogate pairs", () => {
+  for (const text of ["x", "中", "😀"]) {
+    let workspace = defaultWorkspace();
+    for (let index = 0; index < 5; index++) workspace = addTab(workspace);
+    for (const tab of workspace.tabs) {
+      const body = text.repeat(MAX_RESPONSE_CHARS).slice(0, MAX_RESPONSE_CHARS);
+      tab.response = response(body);
+      tab.history = [entry(1, body)];
+      tab.body = `保留草稿 ${text}`;
+    }
+    assert.ok(JSON.stringify(workspace).length * 2 > MAX_STORAGE_BYTES);
+    const json = serializeWorkspace(workspace);
+    assert.ok(json.length * 2 <= MAX_STORAGE_BYTES);
+    assert.deepEqual(
+      JSON.parse(json).tabs.map((tab) => tab.body),
+      workspace.tabs.map((tab) => tab.body),
+    );
+  }
+});
+
+test("drafts exceeding the soft UTF-16 budget are never discarded", () => {
+  const workspace = defaultWorkspace();
+  workspace.tabs[0].body = "x".repeat(MAX_STORAGE_BYTES / 2);
+  workspace.tabs[0].response = response("previous");
+  workspace.tabs[0].history = [entry(1)];
+  const json = serializeWorkspace(workspace);
+  const saved = JSON.parse(json);
+  assert.ok(json.length * 2 > MAX_STORAGE_BYTES);
+  assert.equal(saved.tabs[0].body, workspace.tabs[0].body);
+  assert.deepEqual(saved.tabs[0].history, []);
+  assert.equal(saved.tabs[0].response.body, "");
+});
+
+function setupStore(t) {
+  const previousWindow = globalThis.window;
+  const writes = [];
+  globalThis.window = {
+    localStorage: {
+      setItem: (key, value) => writes.push({ key, value }),
+    },
+  };
+  useRepeaterStore.setState({ workspace: addTab(defaultWorkspace()), inflight: {} });
+  t.after(() => {
+    useRepeaterStore.setState({ workspace: null, inflight: {} });
+    flush(); // Cancel pending persistence without writing to another test's storage.
+    if (previousWindow === undefined) delete globalThis.window;
+    else globalThis.window = previousWindow;
+  });
+  return { store: useRepeaterStore.getState(), writes };
+}
+
+test("a second send invalidates only that tab's first send and stale cleanup cannot clear it", (t) => {
+  const { store } = setupStore(t);
+  const [first, other] = store.workspace.tabs;
+  store.recordSend(first.id, entry(1, "previous"));
+  const generation1 = store.beginSend(first.id);
+  const otherGeneration = store.beginSend(other.id);
+  const generation2 = store.beginSend(first.id);
+  assert.notEqual(generation1, generation2);
+  assert.equal(store.isCurrentSend(first.id, generation1), false);
+  assert.equal(store.isCurrentSend(first.id, generation2), true);
+  assert.equal(store.isCurrentSend(other.id, otherGeneration), true);
+  store.completeSend(first.id, generation1, entry(2, "stale"));
+  store.clearInflight(first.id, generation1);
+  assert.equal(useRepeaterStore.getState().inflight[first.id], generation2);
+  assert.equal(useRepeaterStore.getState().workspace.tabs[0].response.body, "previous");
+  store.completeSend(first.id, generation2, entry(3, "newest"));
+  const state = useRepeaterStore.getState();
+  assert.equal(state.workspace.tabs[0].response.body, "newest");
+  assert.deepEqual(
+    state.workspace.tabs[0].history.map((item) => item.id),
+    ["3", "1"],
+  );
+  assert.equal(state.inflight[first.id], undefined);
+  assert.equal(state.inflight[other.id], otherGeneration);
+});
+
+test("closing a tab or clearing the workspace drops pending results and history", (t) => {
+  const { store } = setupStore(t);
+  const [closed, other] = store.workspace.tabs;
+  const generation = store.beginSend(closed.id);
+  const otherGeneration = store.beginSend(other.id);
+  store.closeTab(closed.id);
+  assert.equal(store.isCurrentSend(closed.id, generation), false);
+  assert.equal(store.beginSend(closed.id), undefined);
+  store.completeSend(closed.id, generation, entry(1));
+  assert.equal(useRepeaterStore.getState().inflight[closed.id], undefined);
+  assert.equal(useRepeaterStore.getState().workspace.tabs.length, 1);
+  assert.deepEqual(useRepeaterStore.getState().workspace.tabs[0].history, []);
+  assert.equal(store.isCurrentSend(other.id, otherGeneration), true);
+  store.clearWorkspace();
+  store.completeSend(other.id, otherGeneration, entry(2));
+  assert.deepEqual(useRepeaterStore.getState().inflight, {});
+  assert.deepEqual(useRepeaterStore.getState().workspace.tabs[0].history, []);
+});
+
+test("busy state survives remount and successful completion records without an editor mounted", async (t) => {
+  const { store, writes } = setupStore(t);
+  const [tab, other] = store.workspace.tabs;
+  store.recordSend(tab.id, entry(1, "previous"));
+  const observedBusy = [];
+  const unmount = useRepeaterStore.subscribe((state) => observedBusy.push(state.inflight[tab.id] !== undefined));
+  const generation = store.beginSend(tab.id);
+  let resolveResponse;
+  const pending = new Promise((resolve) => {
+    resolveResponse = resolve;
+  }).then((result) => store.completeSend(tab.id, generation, result));
+  unmount();
+  store.setActiveTab(other.id);
+  store.setActiveTab(tab.id);
+  // A remounted editor reads the same store selector to disable duplicate sends.
+  assert.equal(useRepeaterStore.getState().inflight[tab.id] !== undefined, true);
+  assert.equal(useRepeaterStore.getState().workspace.tabs[0].response.body, "previous");
+  store.setActiveTab(other.id);
+  resolveResponse(entry(2, "completed offscreen"));
+  await pending;
+  const state = useRepeaterStore.getState();
+  assert.deepEqual(observedBusy, [true]);
+  assert.equal(state.inflight[tab.id], undefined);
+  assert.equal(state.workspace.activeTabId, other.id);
+  assert.equal(state.workspace.tabs[0].response.body, "completed offscreen");
+  assert.deepEqual(
+    state.workspace.tabs[0].history.map((item) => item.id),
+    ["2", "1"],
+  );
+  assert.equal(JSON.parse(writes.at(-1).value).tabs[0].history[0].id, "2");
+});
+
+test("failed send cleanup preserves the previous response and history", (t) => {
+  const { store } = setupStore(t);
+  const tab = store.workspace.tabs[0];
+  store.recordSend(tab.id, entry(1, "previous"));
+  const generation = store.beginSend(tab.id);
+  store.clearInflight(tab.id, generation);
+  const state = useRepeaterStore.getState();
+  assert.equal(state.inflight[tab.id], undefined);
+  assert.equal(state.workspace.tabs[0].response.body, "previous");
+  assert.deepEqual(
+    state.workspace.tabs[0].history.map((item) => item.id),
+    ["1"],
+  );
+});
+
+test("failed storage write retries with histories and response bodies removed, preserving live data and drafts", (t) => {
+  const { store } = setupStore(t);
+  const tab = store.workspace.tabs[0];
+  store.updateTab(tab.id, { body: "keep this draft" });
+  store.recordSend(tab.id, entry(1, "previous response"));
+  const attempts = [];
+  t.mock.method(globalThis.window.localStorage, "setItem", (_key, value) => {
+    attempts.push(value);
+    if (attempts.length === 1) throw new DOMException("full", "QuotaExceededError");
+  });
+  const error = t.mock.method(toast, "error", () => "test-toast");
+  flush();
+  assert.equal(attempts.length, 2);
+  assert.ok(attempts[1].length < attempts[0].length);
+  const saved = JSON.parse(attempts[1]).tabs[0];
+  assert.equal(saved.body, "keep this draft");
+  assert.deepEqual(saved.history, []);
+  assert.equal(saved.response.body, "");
+  assert.equal(saved.response.body_truncated, true);
+  assert.equal(useRepeaterStore.getState().workspace.tabs[0].response.body, "previous response");
+  assert.equal(useRepeaterStore.getState().workspace.tabs[0].history.length, 1);
+  assert.equal(error.mock.callCount(), 0);
+});
+
+test("two failed storage writes report save failure through a Chinese error toast", (t) => {
+  const { store } = setupStore(t);
+  const tab = store.workspace.tabs[0];
+  store.updateTab(tab.id, { body: "unsaved draft" });
+  const setItem = t.mock.method(globalThis.window.localStorage, "setItem", () => {
+    throw new DOMException("full", "QuotaExceededError");
+  });
+  const error = t.mock.method(toast, "error", () => "test-toast");
+  flush();
+  assert.equal(setItem.mock.callCount(), 2);
+  assert.equal(error.mock.callCount(), 1);
+  assert.match(error.mock.calls[0].arguments[0], /工作区保存失败/);
+  assert.equal(useRepeaterStore.getState().workspace.tabs[0].body, "unsaved draft");
 });
 
 test("Host shortcut replaces case-insensitive duplicates and preserves other header lines", () => {
diff --git a/web/src/components/repeater/repeater-store.ts b/web/src/components/repeater/repeater-store.ts
index 912e52c..a6001f0 100644
--- a/web/src/components/repeater/repeater-store.ts
+++ b/web/src/components/repeater/repeater-store.ts
@@ -1,9 +1,9 @@
 "use client";
 
+import { toast } from "sonner";
 import { create } from "zustand";
 
-import { getLocalStorageValue, setLocalStorageValue } from "@/lib/local-storage.client";
-
+import { getLocalStorageValue } from "../../lib/local-storage.client";
 import type { RepeaterInitial } from "./repeater-http";
 import {
   addTab,
@@ -28,6 +28,11 @@ export type TabPatch = Partial<
 >;
 type Store = {
   workspace: RepeaterWorkspace | null;
+  inflight: Record<string, number>;
+  beginSend: (id: string) => number | undefined;
+  isCurrentSend: (id: string, generation: number) => boolean;
+  clearInflight: (id: string, generation: number) => void;
+  completeSend: (id: string, generation: number, entry: RepeaterHistoryEntry) => void;
   hydrate: () => void;
   createTab: (seed?: TabSeed, opts?: TabOptions) => string;
   closeTab: (id: string) => void;
@@ -44,11 +49,23 @@ type Store = {
 };
 
 let timer: ReturnType<typeof setTimeout> | undefined;
-function flush() {
+let nextGeneration = 0;
+export function flush() {
   if (timer) clearTimeout(timer);
   timer = undefined;
   const workspace = useRepeaterStore.getState().workspace;
-  if (workspace) setLocalStorageValue(STORAGE_KEY, serializeWorkspace(workspace));
+  if (!workspace) return;
+  try {
+    window.localStorage.setItem(STORAGE_KEY, serializeWorkspace(workspace));
+  } catch {
+    try {
+      // Retry with only drafts and response metadata: evict all history, then
+      // response bodies. Never shrink the request drafts, even if they exceed quota.
+      window.localStorage.setItem(STORAGE_KEY, serializeWorkspace(workspace, 0));
+    } catch {
+      toast.error("工作区保存失败，浏览器存储空间不足或不可用，请备份请求草稿");
+    }
+  }
 }
 
 export const useRepeaterStore = create<Store>((set, get) => {
@@ -73,6 +90,26 @@ export const useRepeaterStore = create<Store>((set, get) => {
   }
   return {
     workspace: null,
+    inflight: {},
+    beginSend: (id) => {
+      if (!current().tabs.some((tab) => tab.id === id)) return;
+      const generation = ++nextGeneration;
+      set({ inflight: { ...get().inflight, [id]: generation } });
+      return generation;
+    },
+    isCurrentSend: (id, generation) =>
+      get().inflight[id] === generation && !!get().workspace?.tabs.some((tab) => tab.id === id),
+    clearInflight: (id, generation) => {
+      if (get().inflight[id] !== generation) return;
+      const inflight = { ...get().inflight };
+      delete inflight[id];
+      set({ inflight });
+    },
+    completeSend: (id, generation, entry) => {
+      if (!get().isCurrentSend(id, generation)) return;
+      get().recordSend(id, entry);
+      get().clearInflight(id, generation);
+    },
     hydrate: () => {
       if (get().workspace || typeof window === "undefined") return;
       set({ workspace: deserializeWorkspace(getLocalStorageValue(STORAGE_KEY)) });
@@ -90,6 +127,8 @@ export const useRepeaterStore = create<Store>((set, get) => {
       const workspace = current();
       const index = workspace.tabs.findIndex((tab) => tab.id === id);
       if (index < 0) return;
+      const generation = get().inflight[id];
+      if (generation !== undefined) get().clearInflight(id, generation);
       const tabs = workspace.tabs.filter((tab) => tab.id !== id);
       if (!tabs.length) tabs.push(emptyTab());
       change({
@@ -120,7 +159,10 @@ export const useRepeaterStore = create<Store>((set, get) => {
     updateTab: editTab,
     recordSend: (id, entry) => {
       const tab = current().tabs.find((item) => item.id === id);
-      if (tab) editTab(id, { response: entry.response, history: [entry, ...tab.history].slice(0, MAX_HISTORY) });
+      if (tab) {
+        editTab(id, { response: entry.response, history: [entry, ...tab.history].slice(0, MAX_HISTORY) });
+        flush();
+      }
     },
     createGroup: (name) => {
       const workspace = current();
@@ -151,6 +193,7 @@ export const useRepeaterStore = create<Store>((set, get) => {
       });
     },
     clearWorkspace: () => {
+      set({ inflight: {} });
       change(defaultWorkspace());
       flush();
     },