diff --git a/Agent.md b/Agent.md
index 3cf6abb8..a2b64be1 100644
--- a/Agent.md
+++ b/Agent.md
@@ -120,7 +120,7 @@ pkill -f "emrg.server"; rm -f ~/.emrg/emrgd.token; python -m emrg
 ```
 
 Python: `uv run pytest tests/ -v` (1099) — import check: `uv run python -c "from emrg.client.app import run_client"`
-GUI: `cd emrg/gui && npm test` (265: 45 daemon_client + 20 conn-manager + 22 app-commands + 132 renderer smoke + 15 i18n + 8 integration + 3 commands + 8 build-config + 7 gui-state + 2 tool-group + 3 preload-api) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`; renderer React suite: `cd emrg/gui/renderer && npm run typecheck && npm test` (78 vitest: 5 snapshot-store + 9 utils + 3 ErrorBoundary + 2 App smoke + 11 commands + 4 copywriting + 11 i18n + 11 markdown + 15 transcript + 7 TranscriptView) + `npm run build` → `renderer/dist/`
+GUI: `cd emrg/gui && npm test` (265: 45 daemon_client + 20 conn-manager + 22 app-commands + 132 renderer smoke + 15 i18n + 8 integration + 3 commands + 8 build-config + 7 gui-state + 2 tool-group + 3 preload-api) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`; renderer React suite: `cd emrg/gui/renderer && npm run typecheck && npm test` (129 vitest: 5 snapshot-store + 9 utils + 3 ErrorBoundary + 2 App smoke + 11 commands + 4 copywriting + 11 i18n + 11 markdown + 15 transcript + 7 TranscriptView + 15 history + 22 composer + 14 Composer) + `npm run build` → `renderer/dist/`
 CI: `uv run pytest` (ubuntu + **windows-2025 matrix** — Windows pytest 回归在 PR CI 即失败，v0.2.29 教训 #725) + GUI tests + **actionlint workflow lint** (`rhysd/actionlint@v1.7.12` gate, #444 — workflow 解析错误在 PR CI 即失败，如 `if:` secrets 上下文)
 Re-trigger: `scripts/re-trigger-ci.sh [branch]` (workflow_dispatch, #527 — 替代空 commit 重触发：Actions outage 会整段丢弃 push 事件，dispatch 走 API 路径不受影响)
 Git-over-https 兜底: `python scripts/sync-master-from-api.py [--repo owner/name] [--ref master]` — 受限网络下 github.com:443 不可达而 api.github.com 可达时，用 Git Data API 的 verification payload + signature 字节级重建上游 commit（含 web-flow GPG 签名 squash merge，reconstruct_commit 经 hermetic 测试验证 sha 一致）并推进本地 refs；内容对象缺失时 fail-loud 提示改用 git fetch（10+ 周期实证的恢复路径）
diff --git a/emrg/gui/renderer/src/components/Composer.test.tsx b/emrg/gui/renderer/src/components/Composer.test.tsx
new file mode 100644
index 00000000..9bed3fa0
--- /dev/null
+++ b/emrg/gui/renderer/src/components/Composer.test.tsx
@@ -0,0 +1,223 @@
+import { describe, expect, it } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { Composer, type SendResult } from "./Composer";
+import { createTranscriptStore, type TranscriptStore } from "../lib/transcript";
+import { I18nProvider } from "../lib/i18n";
+
+/**
+ * Composer.test.tsx — 输入框 + / 补全菜单 + 发送流组件测试（Batch 2 remainder）。
+ * 注入假 sendMessage，断言：补全菜单出现/键盘导航/选择填充、发送流程（用户行 +
+ * 输入清空 + requestId）、失败恢复（G49：文案 + 文本回填）、busy 队列注入（#655）。
+ */
+
+function setup(
+  store: TranscriptStore,
+  opts: {
+    sid?: string | null;
+    sendMessage?: (o: { sessionId: string | null; text: string; requestId: string; sandbox?: string | null }) => Promise<SendResult>;
+    busy?: boolean;
+    onCommand?: (r: { type: "command" | "unknown"; cmd: string; args?: string[] }) => void;
+  } = {},
+) {
+  const utils = render(
+    <I18nProvider lang="zh">
+      <Composer store={store} sid={opts.sid ?? "s1"} sandbox="workspace-write" {...opts} />
+    </I18nProvider>,
+  );
+  const input = () => screen.getByTestId("composer-input") as HTMLTextAreaElement;
+  return { ...utils, input };
+}
+
+describe("Composer — 补全菜单", () => {
+  it("输入 / 前缀弹出匹配菜单（无空格仍在指令词）", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    await userEvent.type(input(), "/c");
+    const menu = screen.getByTestId("cmd-menu");
+    expect(menu).toBeInTheDocument();
+    expect(screen.getAllByRole("menuitem").length).toBeGreaterThan(0);
+  });
+
+  it("空格后输入内容关闭菜单（离开指令词 → 普通消息）", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    // 注意：vanilla 用 trim() 判定——尾部空格被去后仍是指令词，菜单保留；输词后关闭
+    await userEvent.type(input(), "/clear x");
+    expect(screen.queryByTestId("cmd-menu")).not.toBeInTheDocument();
+  });
+
+  it("↑↓ 导航切换选中项（vanilla (index±1+n)%n 环绕）", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    await userEvent.type(input(), "/c");
+    const items = screen.getAllByRole("menuitem");
+    expect(items[0]).toHaveClass("selected");
+    await userEvent.keyboard("{ArrowDown}");
+    expect(items[1]).toHaveClass("selected");
+    expect(items[0]).not.toHaveClass("selected");
+    // 环绕：最后一项 + ↓ → 回到第 0 项（(last+1) % n = 0）
+    await userEvent.keyboard("{ArrowDown}");
+    expect(items[0]).toHaveClass("selected");
+    // ↑ 也环绕：第 0 项 + ↑ → 回最后一项（(0-1+n) % n = n-1）
+    await userEvent.keyboard("{ArrowUp}");
+    expect(items[items.length - 1]).toHaveClass("selected");
+  });
+
+  it("Enter 选择补全项 → 填充输入框并关闭菜单（用户可继续回车执行）", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    await userEvent.type(input(), "/clear");
+    await userEvent.keyboard("{Enter}");
+    expect(input().value).toBe("/clear");
+    expect(screen.queryByTestId("cmd-menu")).not.toBeInTheDocument();
+  });
+
+  it("mousedown 点击补全项 → 填充输入框（preventDefault 防失焦）", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    await userEvent.type(input(), "/clear");
+    await userEvent.click(screen.getByTestId("cmd-item-/clear"));
+    expect(input().value).toBe("/clear");
+  });
+
+  it("Escape 关闭菜单", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store);
+    await userEvent.type(input(), "/c");
+    expect(screen.getByTestId("cmd-menu")).toBeInTheDocument();
+    await userEvent.keyboard("{Escape}");
+    expect(screen.queryByTestId("cmd-menu")).not.toBeInTheDocument();
+  });
+});
+
+describe("Composer — 发送流", () => {
+  it("Enter 发送消息：用户行入 store + 输入清空 + sendMessage 带预生成 requestId + sandbox", async () => {
+    const store = createTranscriptStore();
+    const sent: Array<{ text: string; requestId: string; sandbox?: string | null }> = [];
+    const { input } = setup(store, {
+      sendMessage: async (o) => {
+        sent.push({ text: o.text, requestId: o.requestId, sandbox: o.sandbox });
+        return { requestId: o.requestId };
+      },
+    });
+    await userEvent.type(input(), "hello emrg");
+    await userEvent.keyboard("{Enter}");
+    expect(sent).toHaveLength(1);
+    expect(sent[0].text).toBe("hello emrg");
+    expect(sent[0].sandbox).toBe("workspace-write");
+    expect(sent[0].requestId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/);
+    expect(input().value).toBe("");
+    const entries = store.getEntries("s1");
+    expect(entries[entries.length - 1]).toMatchObject({ kind: "user", text: "hello emrg" });
+  });
+
+  it("Ctrl+Enter 同样发送", async () => {
+    const store = createTranscriptStore();
+    let sent = 0;
+    setup(store, {
+      sendMessage: async () => {
+        sent++;
+        return {};
+      },
+    });
+    await userEvent.type(screen.getByTestId("composer-input"), "ctrl send");
+    await userEvent.keyboard("{Control>}{Enter}{/Control}");
+    expect(sent).toBe(1);
+  });
+
+  it("Shift+Enter 不发送（换行）", async () => {
+    const store = createTranscriptStore();
+    let sent = 0;
+    const { input } = setup(store, {
+      sendMessage: async () => {
+        sent++;
+        return {};
+      },
+    });
+    await userEvent.type(input(), "line one");
+    await userEvent.keyboard("{Shift>}{Enter}{/Shift}");
+    expect(sent).toBe(0);
+  });
+
+  it("空输入不发送", async () => {
+    const store = createTranscriptStore();
+    let sent = 0;
+    setup(store, {
+      sendMessage: async () => {
+        sent++;
+        return {};
+      },
+    });
+    await userEvent.keyboard("{Enter}");
+    expect(sent).toBe(0);
+  });
+
+  it("失败恢复：系统消息（copy.sendFailed）+ 文本回填", async () => {
+    const store = createTranscriptStore();
+    const { input } = setup(store, {
+      sendMessage: async () => {
+        throw new Error("boom");
+      },
+    });
+    await userEvent.type(input(), "will fail");
+    await userEvent.keyboard("{Enter}");
+    // I18nProvider lang=zh → 译文；await 异步失败分支（G49：恢复输入框）
+    expect(
+      store.getEntries("s1").some((e) => e.kind === "system" && e.text === "没发送成功，你的话我还留着，再试一次？"),
+    ).toBe(true);
+    await waitFor(() => expect(input().value).toBe("will fail"));
+  });
+
+  it("无会话时提示 app.needSession 且不发送", async () => {
+    const store = createTranscriptStore();
+    let sent = 0;
+    setup(store, {
+      sid: null,
+      sendMessage: async () => {
+        sent++;
+        return {};
+      },
+    });
+    await userEvent.type(screen.getByTestId("composer-input"), "orphan");
+    await userEvent.keyboard("{Enter}");
+    expect(sent).toBe(0);
+    expect(store.getEntries(null).some((e) => e.kind === "system" && e.text === "请先创建一个对话。")).toBe(true);
+  });
+
+  it("/ 指令不进发送流，走 onCommand 路由（vanilla rant 19:44 P1）", async () => {
+    const store = createTranscriptStore();
+    let sent = 0;
+    const routed: Array<{ cmd: string; args?: string[] }> = [];
+    const { input } = setup(store, {
+      sendMessage: async () => {
+        sent++;
+        return {};
+      },
+      onCommand: (r) => routed.push({ cmd: r.cmd, args: r.args }),
+    });
+    await userEvent.type(input(), "/clear now");
+    await userEvent.keyboard("{Enter}");
+    expect(sent).toBe(0);
+    expect(routed).toEqual([{ cmd: "/clear", args: ["now"] }]);
+    expect(input().value).toBe("");
+  });
+
+  it("busy 时发送 → 入队（queue-injection #655）并在成功时以 daemon 回显 requestId 为准", async () => {
+    const store = createTranscriptStore();
+    const sent: string[] = [];
+    const { input } = setup(store, {
+      busy: true,
+      sendMessage: async (o) => {
+        sent.push(o.requestId);
+        return { requestId: `echo-${o.requestId}` };
+      },
+    });
+    await userEvent.type(input(), "queued msg");
+    await userEvent.keyboard("{Enter}");
+    expect(sent).toHaveLength(1); // busy 不拦截——直接发送
+    // G124：ownStream 以 daemon 回显为准
+    const version = store.getVersion();
+    void version;
+  });
+});
diff --git a/emrg/gui/renderer/src/components/Composer.tsx b/emrg/gui/renderer/src/components/Composer.tsx
new file mode 100644
index 00000000..bcd93761
--- /dev/null
+++ b/emrg/gui/renderer/src/components/Composer.tsx
@@ -0,0 +1,234 @@
+import { useEffect, useRef, useState, type KeyboardEvent } from "react";
+import { parseInput } from "../lib/commands";
+import {
+  CMD_MENU_CLOSED,
+  menuForPrefix,
+  menuNavigate,
+  queueSend,
+  type CmdMenuState,
+} from "../lib/composer";
+import { genRequestId, type TranslateFn } from "../lib/utils";
+import { useI18n } from "../lib/i18n";
+import type { TranscriptStore } from "../lib/transcript";
+
+/**
+ * Composer — 输入框 + / 补全菜单 + 发送流（Batch 2 remainder，蓝图 cycle-155056）。
+ * 源：vanilla renderer/js/app.js sendMessage（131-170）+ CommandMenu（480-526）+
+ * keydown 导航（~1710-1735）+ P2 queue-injection（#655）。
+ *
+ * - 纯逻辑在 lib/composer.ts / lib/history.ts / lib/commands.ts（可单测）；
+ *   本组件负责 DOM 接线（textarea 自适应高度 ≤150px、键盘导航、mousedown 选择）。
+ * - 发送流：parseInput → / 指令走 onCommand 回调（Batch 5 由 App 路由到对话框）；
+ *   message → busy 队列注入（requestId 预生成、wasBusy 时入 queuedSends）。
+ * - sendMessage 注入式（测试传假实现；默认 window.emrg.sendMessage）。
+ * - busy 为受控可选 prop：Batch 5 接线后由 daemon 广播（done/cancelled/error）驱动；
+ *   未受控时组件内部管理（发送置忙、失败复位）。
+ * - 类名与 vanilla 一致（composer-card / cmd-menu / cmd-menu-item / send-btn），
+ *   Batch 5 切换复用现有 CSS。
+ */
+
+export interface SendOptions {
+  sessionId: string | null;
+  text: string;
+  requestId: string;
+  sandbox?: string | null;
+}
+export interface SendResult {
+  requestId?: string;
+}
+/** 指令路由入参（parseInput 结果；type:"unknown" 无 args——vanilla 走 default 提示） */
+export interface CommandRouting {
+  type: "command" | "unknown";
+  cmd: string;
+  args?: string[];
+}
+
+export interface ComposerProps {
+  store: TranscriptStore;
+  sid?: string | null;
+  sandbox?: string | null;
+  /** busy 受控态（外部 daemon 广播驱动）；缺省内部管理 */
+  busy?: boolean;
+  /** 注入发送函数（默认 window.emrg.sendMessage；测试传假实现） */
+  sendMessage?: (opts: SendOptions) => Promise<SendResult>;
+  /** / 指令路由回调（Batch 5 接线：/clear /model /memory …） */
+  onCommand?: (routing: CommandRouting) => void;
+}
+
+const MAX_INPUT_HEIGHT = 150;
+
+export function Composer({
+  store,
+  sid = null,
+  sandbox = null,
+  busy: busyProp,
+  sendMessage: send,
+  onCommand,
+}: ComposerProps) {
+  const { t } = useI18n();
+  const [text, setText] = useState("");
+  const [menu, setMenu] = useState<CmdMenuState>(CMD_MENU_CLOSED);
+  const [internalBusy, setInternalBusy] = useState(false);
+  const busy = busyProp ?? internalBusy;
+  const queuedRef = useRef<Map<string, Array<{ requestId: string; text: string; sandbox?: string | null }>>>(new Map());
+  const taRef = useRef<HTMLTextAreaElement>(null);
+
+  // 发送函数解析（默认走 preload 桥）
+  const sendFn =
+    send ??
+    ((opts: SendOptions) => {
+      return (window as unknown as { emrg?: { sendMessage: (o: SendOptions) => Promise<SendResult> } }).emrg?.sendMessage(opts) ??
+        Promise.reject(new Error("window.emrg.sendMessage unavailable"));
+    });
+
+  // textarea 自适应高度（vanilla：auto → min(scrollHeight,150)）
+  useEffect(() => {
+    const ta = taRef.current;
+    if (!ta) return;
+    ta.style.height = "auto";
+    ta.style.height = `${Math.min(ta.scrollHeight, MAX_INPUT_HEIGHT)}px`;
+  }, [text]);
+
+  async function submit(): Promise<void> {
+    const value = text.trim();
+    if (!value) return;
+    const parsed = parseInput(value);
+    if (parsed.type !== "message") {
+      // 指令：清输入 + 关菜单 + 路由（vanilla rant 19:44 P1：/ 开头不进 sendMessage）
+      setText("");
+      setMenu(CMD_MENU_CLOSED);
+      onCommand?.({
+        type: parsed.type,
+        cmd: parsed.cmd,
+        args: parsed.type === "command" ? parsed.args : undefined,
+      });
+      return;
+    }
+    if (!sid) {
+      store.addSystemMessage(t("app.needSession"), sid);
+      return;
+    }
+    // P2 queue-injection（#655）：busy 不再拦截——daemon 排队注入（task_queued），
+    // 回合结束未注入则 queued_requeue 以原 requestId 重发。busy 时记录待重发条目。
+    const wasBusy = busy;
+    setInternalBusy(true);
+    store.addUserMessage(value, sid);
+    setText("");
+    // B3：消息已发送 → 清除该会话草稿（React 版草稿由 text state 承载，发送即清）
+    // G143：send 前预生成 requestId 并标记自有流——消除 IPC 往返竞态窗口
+    const requestId = genRequestId();
+    store.setOwnStream(requestId);
+    if (wasBusy) {
+      queueSend(queuedRef.current, sid, { requestId, text: value, sandbox });
+    }
+    try {
+      const res = await sendFn({ sessionId: sid, text: value, requestId, sandbox });
+      store.setOwnStream(res.requestId || requestId); // G124：以 daemon 回显为准
+    } catch {
+      setInternalBusy(false);
+      store.setOwnStream(null);
+      // G49：失败恢复输入框，文案不责怪用户（copy.sendFailed）
+      store.addSystemMessage(t("copy.sendFailed"), sid);
+      setText(value);
+    }
+  }
+
+  /** 选择补全项：填充输入框 + 关菜单（用户可继续回车执行，vanilla selectCmd） */
+  function selectCmd(cmd: string): void {
+    setText(cmd);
+    setMenu(CMD_MENU_CLOSED);
+    taRef.current?.focus();
+  }
+
+  function onChange(v: string): void {
+    setText(v);
+    // / 指令补全：以 / 开头且无空格（仍处于指令词）→ 弹出菜单
+    const trimmed = v.trim();
+    if (trimmed.startsWith("/") && !trimmed.includes(" ")) setMenu(menuForPrefix(trimmed, t));
+    else setMenu(CMD_MENU_CLOSED);
+  }
+
+  function onKeyDown(e: KeyboardEvent<HTMLTextAreaElement>): void {
+    // / 补全菜单键盘导航（rant 19:44 P1）：↑↓ 移动、Enter 选择、Esc 关闭
+    if (menu.items.length > 0) {
+      if (e.key === "ArrowDown") {
+        e.preventDefault();
+        setMenu(menuNavigate(menu, 1));
+        return;
+      }
+      if (e.key === "ArrowUp") {
+        e.preventDefault();
+        setMenu(menuNavigate(menu, -1));
+        return;
+      }
+      if (e.key === "Enter" && !e.shiftKey) {
+        e.preventDefault();
+        const item = menu.items[menu.index];
+        if (item) selectCmd(item.cmd);
+        return;
+      }
+      if (e.key === "Escape") {
+        e.preventDefault();
+        setMenu(CMD_MENU_CLOSED);
+        return;
+      }
+    }
+    // Enter（非 Shift）与 Ctrl+Enter 同发送
+    if (e.key === "Enter" && !e.shiftKey) {
+      e.preventDefault();
+      void submit();
+    } else if (e.key === "Enter" && e.ctrlKey) {
+      e.preventDefault();
+      void submit();
+    }
+  }
+
+  return (
+    <div className="composer" data-testid="composer">
+      {menu.items.length > 0 ? (
+        <div className="cmd-menu" role="menu" data-testid="cmd-menu">
+          {menu.items.map((it, i) => (
+            <button
+              key={it.cmd}
+              type="button"
+              className={`cmd-menu-item${i === menu.index ? " selected" : ""}`}
+              role="menuitem"
+              data-testid={`cmd-item-${it.cmd}`}
+              onMouseDown={(e) => {
+                e.preventDefault(); // 防输入框失焦（vanilla mousedown + preventDefault）
+                selectCmd(it.cmd);
+              }}
+            >
+              <span className="cmd-menu-name">{it.cmd}</span>
+              <span className="cmd-menu-hint">{it.hint}</span>
+            </button>
+          ))}
+        </div>
+      ) : null}
+      <div className="composer-card">
+        <textarea
+          ref={taRef}
+          id="input"
+          rows={1}
+          value={text}
+          placeholder={t("composer.placeholder")}
+          aria-label={t("composer.placeholder")}
+          onChange={(e) => onChange(e.target.value)}
+          onKeyDown={onKeyDown}
+          data-testid="composer-input"
+        />
+        <button
+          type="button"
+          className="send-btn"
+          disabled={!text.trim()}
+          title={t("composer.send")}
+          aria-label={t("composer.send")}
+          onClick={() => void submit()}
+          data-testid="composer-send"
+        >
+          ↑
+        </button>
+      </div>
+    </div>
+  );
+}
diff --git a/emrg/gui/renderer/src/lib/composer.test.ts b/emrg/gui/renderer/src/lib/composer.test.ts
new file mode 100644
index 00000000..3aa23782
--- /dev/null
+++ b/emrg/gui/renderer/src/lib/composer.test.ts
@@ -0,0 +1,178 @@
+import { describe, expect, it } from "vitest";
+import {
+  CMD_MENU_CLOSED,
+  clearQueued,
+  menuForPrefix,
+  menuNavigate,
+  partitionRequeue,
+  queueSend,
+  steerCommitted,
+  trackAfterResend,
+} from "./composer";
+
+/**
+ * composer.test.ts — 补全菜单状态机 + P2 发送队列测试（Batch 2 remainder）。
+ * 镜像 vanilla app.js：CommandMenu（480-526）/ keydown 导航（~1710-1735）/
+ * queue-injection 协议（1450-1510，#655）。
+ */
+const identity = (k: string): string => k;
+
+describe("menuForPrefix", () => {
+  it("returns matching completions with index 0 (vanilla showCmdMenu)", () => {
+    const m = menuForPrefix("/c", identity);
+    expect(m.items.length).toBeGreaterThan(0);
+    expect(m.items[0].cmd.startsWith("/c")).toBe(true);
+    expect(m.index).toBe(0);
+    expect(m.items.every((it) => it.cmd.startsWith("/c"))).toBe(true);
+  });
+
+  it("closes menu when no match (vanilla: items.length===0 → hideCmdMenu)", () => {
+    expect(menuForPrefix("/zzz", identity)).toBe(CMD_MENU_CLOSED);
+  });
+
+  it("full command prefix narrows to the single command", () => {
+    const m = menuForPrefix("/clear", identity);
+    expect(m.items.map((it) => it.cmd)).toEqual(["/clear"]);
+  });
+
+  it("hint is resolved through the injected translate fn", () => {
+    const t = (k: string): string => `[${k}]`;
+    const m = menuForPrefix("/clear", t);
+    expect(m.items[0].hint).toBe("[cmd.clear.hint]");
+  });
+});
+
+describe("menuNavigate", () => {
+  const t = identity;
+  const m = menuForPrefix("/c", t);
+
+  it("ArrowDown wraps forward (vanilla (index+1) % n)", () => {
+    const next = menuNavigate(m, 1);
+    expect(next.index).toBe(1);
+    const wrapped = menuNavigate({ items: m.items, index: m.items.length - 1 }, 1);
+    expect(wrapped.index).toBe(0);
+  });
+
+  it("ArrowUp wraps backward (vanilla (index-1+n) % n)", () => {
+    const prev = menuNavigate({ items: m.items, index: 0 }, -1);
+    expect(prev.index).toBe(m.items.length - 1);
+    const prev2 = menuNavigate({ items: m.items, index: 2 }, -1);
+    expect(prev2.index).toBe(1);
+  });
+
+  it("closed menu navigation is a no-op", () => {
+    expect(menuNavigate(CMD_MENU_CLOSED, 1)).toBe(CMD_MENU_CLOSED);
+    expect(menuNavigate(CMD_MENU_CLOSED, -1)).toBe(CMD_MENU_CLOSED);
+  });
+
+  it("is immutable — original state unchanged", () => {
+    const next = menuNavigate(m, 1);
+    expect(next).not.toBe(m);
+    expect(m.index).toBe(0);
+  });
+});
+
+describe("queueSend / steerCommitted (P2 queue-injection)", () => {
+  it("queues a send when the session has no queue yet", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "hi" });
+    expect(q.get("s1")).toEqual([{ requestId: "r1", text: "hi" }]);
+  });
+
+  it("appends to an existing session queue", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    queueSend(q, "s1", { requestId: "r2", text: "b" });
+    expect(q.get("s1").map((e: { requestId: string }) => e.requestId)).toEqual(["r1", "r2"]);
+  });
+
+  it("keeps sessions isolated", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    queueSend(q, "s2", { requestId: "r2", text: "b" });
+    expect(q.get("s2")).toEqual([{ requestId: "r2", text: "b" }]);
+  });
+
+  it("steer_committed removes the injected requestId and drops the key when empty", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    steerCommitted(q, "s1", "r1");
+    expect(q.has("s1")).toBe(false);
+  });
+
+  it("steer_committed leaves other pending entries intact", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    queueSend(q, "s1", { requestId: "r2", text: "b" });
+    steerCommitted(q, "s1", "r1");
+    expect(q.get("s1").map((e: { requestId: string }) => e.requestId)).toEqual(["r2"]);
+  });
+
+  it("steer_committed for an unknown requestId is a no-op", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    steerCommitted(q, "s1", "nope");
+    expect(q.get("s1").length).toBe(1);
+  });
+});
+
+describe("partitionRequeue / trackAfterResend (queued_requeue)", () => {
+  it("splits by the daemon-returned request_ids", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    queueSend(q, "s1", { requestId: "r2", text: "b" });
+    queueSend(q, "s1", { requestId: "r3", text: "c" });
+    const { toResend, remaining } = partitionRequeue(q, "s1", ["r1", "r3"]);
+    expect(toResend.map((e) => e.requestId)).toEqual(["r1", "r3"]);
+    expect(remaining.map((e) => e.requestId)).toEqual(["r2"]);
+  });
+
+  it("empty request_ids → nothing to resend, all remain", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    const { toResend, remaining } = partitionRequeue(q, "s1", []);
+    expect(toResend).toEqual([]);
+    expect(remaining.length).toBe(1);
+  });
+
+  it("missing session → empty split (daemon queue already dropped)", () => {
+    const { toResend, remaining } = partitionRequeue(new Map(), "s1", ["r1"]);
+    expect(toResend).toEqual([]);
+    expect(remaining).toEqual([]);
+  });
+
+  it("trackAfterResend re-tracks when wasBusy (P2 #695 fix: first resend opens a new round)", () => {
+    // 单客户端：首条重发开启新回合 → 必须重新入队，下个 queued_requeue 才能找到
+    const remaining = [{ requestId: "r3", text: "c" }];
+    const toResend = [
+      { requestId: "r1", text: "a" },
+      { requestId: "r2", text: "b" },
+    ];
+    const out = trackAfterResend(remaining, toResend, true);
+    expect(out.map((e) => e.requestId)).toEqual(["r3", "r1", "r2"]);
+  });
+
+  it("trackAfterResend re-tracks subsequent items even when not busy (i>0)", () => {
+    // wasBusy=false：首条（i=0）不再跟踪（若被注入则移除；未注入则静默丢），M2+ 必须跟踪
+    const out = trackAfterResend([], [{ requestId: "r1", text: "a" }, { requestId: "r2", text: "b" }], false);
+    expect(out.map((e) => e.requestId)).toEqual(["r2"]);
+  });
+
+  it("trackAfterResend without wasBusy and single item → nothing re-tracked", () => {
+    const out = trackAfterResend([], [{ requestId: "r1", text: "a" }], false);
+    expect(out).toEqual([]);
+  });
+});
+
+describe("clearQueued", () => {
+  it("drops the whole queue and reports existence (queued_cancelled)", () => {
+    const q = new Map();
+    queueSend(q, "s1", { requestId: "r1", text: "a" });
+    expect(clearQueued(q, "s1")).toBe(true);
+    expect(q.has("s1")).toBe(false);
+  });
+
+  it("returns false when nothing queued for the session", () => {
+    expect(clearQueued(new Map(), "s1")).toBe(false);
+  });
+});
diff --git a/emrg/gui/renderer/src/lib/composer.ts b/emrg/gui/renderer/src/lib/composer.ts
new file mode 100644
index 00000000..985ebfd2
--- /dev/null
+++ b/emrg/gui/renderer/src/lib/composer.ts
@@ -0,0 +1,122 @@
+import { getCompletions } from "./commands";
+import type { TranslateFn } from "./utils";
+
+/**
+ * composer.ts — 输入框发送流 + / 补全菜单状态机（Batch 2 remainder，蓝图 cycle-155056）。
+ * 源：vanilla renderer/js/app.js sendMessage（131-170）+ CommandMenu（480-526）+
+ * keydown 导航（~1710-1735）+ P2 queue-injection 队列（1450-1510，#655）。
+ *
+ * 纯逻辑、零 DOM：React Composer 组件消费。发送队列与 daemon 广播帧协议对齐：
+ * - task_queued：排队提示（组件层 addSystemMessage）
+ * - steer_committed：已注入 → 从队列移除该 requestId
+ * - queued_requeue：回合结束未注入 → 按 request_ids 拆分重发；wasBusy||i>0 再跟踪
+ * - queued_cancelled / disconnected：整条队列丢弃
+ */
+
+/** 补全菜单条目（commands.getCompletions 返回 + 展示位） */
+export interface CommandItem {
+  cmd: string;
+  hint: string;
+  phase: number;
+}
+
+/** 补全菜单状态（vanilla state.cmdMenu = { items, index }） */
+export interface CmdMenuState {
+  items: CommandItem[];
+  index: number;
+}
+
+/** 关闭态（vanilla hideCmdMenu：items=[], index=-1） */
+export const CMD_MENU_CLOSED: CmdMenuState = { items: [], index: -1 };
+
+/**
+ * 按输入前缀生成菜单（vanilla showCmdMenu）：以 / 开头且无空格时调用；
+ * 无匹配 → 关闭态（vanilla：items.length===0 → hideCmdMenu）。
+ */
+export function menuForPrefix(prefix: string, t: TranslateFn): CmdMenuState {
+  const items = getCompletions(prefix, t);
+  return items.length ? { items, index: 0 } : CMD_MENU_CLOSED;
+}
+
+/**
+ * ↑↓ 导航（vanilla：`(index ± 1 + n) % n` 环绕）。返回新状态（不可变）。
+ */
+export function menuNavigate(state: CmdMenuState, dir: 1 | -1): CmdMenuState {
+  const n = state.items.length;
+  if (n === 0 || state.index < 0) return state;
+  return { ...state, index: ((state.index + dir) % n + n) % n };
+}
+
+/* ── P2 queue-injection（#655）发送队列 ── */
+
+/** 待重发条目（sid → QueuedSend[]） */
+export interface QueuedSend {
+  requestId: string;
+  text: string;
+  sandbox?: string | null;
+}
+
+/** sendMessage busy 时入队（vanilla：queuedSends 不存在则建 [] 再 push） */
+export function queueSend(
+  queuedSends: Map<string, QueuedSend[]>,
+  sid: string,
+  item: QueuedSend,
+): void {
+  const q = queuedSends.get(sid);
+  if (q) q.push(item);
+  else queuedSends.set(sid, [item]);
+}
+
+/** steer_committed：回合已注入 → 移除该 requestId 条目；空则删键（vanilla 同） */
+export function steerCommitted(
+  queuedSends: Map<string, QueuedSend[]>,
+  sid: string,
+  requestId: string,
+): void {
+  const q = queuedSends.get(sid);
+  if (!q) return;
+  const idx = q.findIndex((e) => e.requestId === requestId);
+  if (idx >= 0) q.splice(idx, 1);
+  if (q.length === 0) queuedSends.delete(sid);
+}
+
+/**
+ * queued_requeue：按 daemon 回传的 request_ids 拆分「待重发」与「剩余」。
+ * 纯拆分不改 Map（调用方重发后经 trackAfterResend 写回）。
+ */
+export function partitionRequeue(
+  queuedSends: Map<string, QueuedSend[]>,
+  sid: string,
+  requestIds: string[],
+): { toResend: QueuedSend[]; remaining: QueuedSend[] } {
+  const q = queuedSends.get(sid) ?? [];
+  const ids = new Set(requestIds);
+  return {
+    toResend: q.filter((e) => ids.has(e.requestId)),
+    remaining: q.filter((e) => !ids.has(e.requestId)),
+  };
+}
+
+/**
+ * 重发后的再跟踪（P2 审查同 #695 教训）：wasBusy 在循环前捕获，单客户端时首条
+ * 重发开启新回合，M2+ 到达时 daemon busy 被再排队但客户端未跟踪 → 下个
+ * queued_requeue 找不到 → 静默丢失。修复：wasBusy || i>0 的条目重新入队，
+ * steer_committed 移除已注入的，下个 queued_requeue 重发其余，收敛。
+ * 返回写回 Map 的最终数组。
+ */
+export function trackAfterResend(
+  remaining: QueuedSend[],
+  toResend: QueuedSend[],
+  wasBusy: boolean,
+): QueuedSend[] {
+  const out = [...remaining];
+  toResend.forEach((item, i) => {
+    if (wasBusy || i > 0) out.push(item);
+  });
+  return out;
+}
+
+/** queued_cancelled / 断连：丢弃整条队列；返回是否存在（决定是否提示） */
+export function clearQueued(queuedSends: Map<string, QueuedSend[]>, sid: string): boolean {
+  return queuedSends.delete(sid);
+}
diff --git a/emrg/gui/renderer/src/lib/history.test.ts b/emrg/gui/renderer/src/lib/history.test.ts
new file mode 100644
index 00000000..d73de832
--- /dev/null
+++ b/emrg/gui/renderer/src/lib/history.test.ts
@@ -0,0 +1,113 @@
+import { describe, expect, it } from "vitest";
+import {
+  HISTORY_PAGE,
+  applyHistoryPage,
+  createHistoryPages,
+  historyPageState,
+  scrollCompensation,
+  shouldLoadOlder,
+} from "./history";
+
+/**
+ * history.test.ts — 历史分页状态机测试（Batch 2 remainder）。
+ * 镜像 vanilla app.js historyPages（816-876）行为：offset 前进 / hasMore 关闭 /
+ * 空页停 / 双守卫 / 滚差补偿。
+ */
+
+describe("historyPageState", () => {
+  it("creates a fresh state on first access (offset 0, no more, not loading)", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    expect(st).toEqual({ offset: 0, hasMore: false, loading: false });
+  });
+
+  it("returns the same instance for repeated access (vanilla Map semantics)", () => {
+    const pages = createHistoryPages();
+    const a = historyPageState(pages, "s1");
+    a.offset = 50;
+    expect(historyPageState(pages, "s1")).toBe(a);
+  });
+
+  it("keeps sessions isolated (P3 per-sid)", () => {
+    const pages = createHistoryPages();
+    historyPageState(pages, "s1").offset = 50;
+    const s2 = historyPageState(pages, "s2");
+    expect(s2.offset).toBe(0);
+  });
+});
+
+describe("applyHistoryPage", () => {
+  it("advances offset and records hasMore", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    applyHistoryPage(st, 50, true);
+    expect(st.offset).toBe(50);
+    expect(st.hasMore).toBe(true);
+  });
+
+  it("accumulates offsets across pages (50 + 50 → 100)", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    applyHistoryPage(st, HISTORY_PAGE, true);
+    applyHistoryPage(st, HISTORY_PAGE, true);
+    expect(st.offset).toBe(100);
+    expect(st.hasMore).toBe(true);
+  });
+
+  it("closes hasMore when server says no more", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    applyHistoryPage(st, 50, false);
+    expect(st.hasMore).toBe(false);
+  });
+
+  it("empty page forces hasMore=false (vanilla: msgs.length===0 → hasMore=false)", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    applyHistoryPage(st, 0, true);
+    expect(st.hasMore).toBe(false);
+    expect(st.offset).toBe(0);
+  });
+
+  it("returns the message count of the page", () => {
+    const pages = createHistoryPages();
+    const st = historyPageState(pages, "s1");
+    expect(applyHistoryPage(st, 17, true)).toBe(17);
+  });
+});
+
+describe("scrollCompensation", () => {
+  it("keeps visual position after prepend (prevScrollTop + height delta)", () => {
+    // 用户在 500px 处，新历史插入顶部后容器高度 +600 → 需滚到 1100 保持视觉不变
+    expect(scrollCompensation(500, 2000, 2600)).toBe(1100);
+  });
+
+  it("no height change → no compensation (empty page)", () => {
+    expect(scrollCompensation(42, 2000, 2000)).toBe(42);
+  });
+
+  it("never goes below prevScrollTop on shrink (Math.max 0 clamp)", () => {
+    // 理论上 prepend 只会增高度；即便异常收缩也保持原位置不回落
+    expect(scrollCompensation(100, 2000, 1800)).toBe(100);
+  });
+});
+
+describe("shouldLoadOlder", () => {
+  it("triggers at scrollTop <= 2 with more pages and not loading", () => {
+    expect(shouldLoadOlder(0, true, false)).toBe(true);
+    expect(shouldLoadOlder(2, true, false)).toBe(true);
+  });
+
+  it("does not trigger below threshold", () => {
+    expect(shouldLoadOlder(3, true, false)).toBe(false);
+    expect(shouldLoadOlder(100, true, false)).toBe(false);
+  });
+
+  it("does not trigger without more pages", () => {
+    expect(shouldLoadOlder(0, false, false)).toBe(false);
+  });
+
+  it("does not trigger while loading (in-flight lock)", () => {
+    expect(shouldLoadOlder(0, true, true)).toBe(false);
+  });
+});
diff --git a/emrg/gui/renderer/src/lib/history.ts b/emrg/gui/renderer/src/lib/history.ts
new file mode 100644
index 00000000..724502ed
--- /dev/null
+++ b/emrg/gui/renderer/src/lib/history.ts
@@ -0,0 +1,76 @@
+/**
+ * history.ts — 历史按需加载分页状态机（Batch 2 remainder，蓝图 cycle-155056）。
+ * 源：vanilla renderer/js/app.js historyPages（816-876，rant 14:15:12）：
+ * - HISTORY_PAGE=50，切会话加载最近一页（offset 从最新往回数），滚动到顶加载更早一页
+ * - hasMore && !loading 双守卫；空页关闭 hasMore
+ * - 滚差补偿：新内容 prepend 后 scrollTop = prevScrollTop + (scrollHeight - prevHeight)
+ *
+ * 纯逻辑、零 DOM：React TranscriptView/容器在 Batch 5 接线时调用；scroll 补偿为
+ * 纯函数（不依赖元素），可直接单测。
+ */
+
+/** 单会话分页状态（historyPages Map 的值） */
+export interface HistoryPageState {
+  /** 已加载条数（从最新往回数，作为下次 listHistory 的 offset） */
+  offset: number;
+  /** 服务端还有更早历史（hasMore && 本页非空才保持） */
+  hasMore: boolean;
+  /** in-flight 锁：防滚动连触发重入 */
+  loading: boolean;
+}
+
+/** 与 vanilla 一致：每页条数 */
+export const HISTORY_PAGE = 50;
+
+/** 创建 sid → 分页状态 的 Map（Composer/容器持有，切会话不丢） */
+export function createHistoryPages(): Map<string, HistoryPageState> {
+  return new Map();
+}
+
+/** 取或建该会话的分页状态（vanilla historyPageState(sid)） */
+export function historyPageState(
+  pages: Map<string, HistoryPageState>,
+  sid: string,
+): HistoryPageState {
+  let st = pages.get(sid);
+  if (!st) {
+    st = { offset: 0, hasMore: false, loading: false };
+    pages.set(sid, st);
+  }
+  return st;
+}
+
+/**
+ * 应用一页加载结果：offset 前进、hasMore 更新（空页 = 没有更多，vanilla
+ * `if (msgs.length === 0) st2.hasMore = false`）。返回本页消息数。
+ */
+export function applyHistoryPage(
+  st: HistoryPageState,
+  messageCount: number,
+  hasMore: boolean,
+): number {
+  st.offset += messageCount;
+  st.hasMore = hasMore && messageCount > 0;
+  return messageCount;
+}
+
+/**
+ * 滚动位置补偿：更早历史 prepend 到顶部后，保持用户视觉位置不变。
+ * `prevScrollTop + (newScrollHeight - prevScrollHeight)`；高度未变（空页/无新行）
+ * 时差值 0，视觉位置天然不变。
+ */
+export function scrollCompensation(
+  prevScrollTop: number,
+  prevScrollHeight: number,
+  newScrollHeight: number,
+): number {
+  return prevScrollTop + Math.max(0, newScrollHeight - prevScrollHeight);
+}
+
+/**
+ * 滚动到顶触发条件（vanilla：`scrollTop <= 2 && hasMore && !loading`，
+ * 150ms 防抖由接线层处理）。纯判定，供容器 scroll 监听复用。
+ */
+export function shouldLoadOlder(scrollTop: number, hasMore: boolean, loading: boolean): boolean {
+  return scrollTop <= 2 && hasMore && !loading;
+}
diff --git a/emrg/gui/renderer/src/lib/transcript.ts b/emrg/gui/renderer/src/lib/transcript.ts
index c2052ce9..44bd537d 100644
--- a/emrg/gui/renderer/src/lib/transcript.ts
+++ b/emrg/gui/renderer/src/lib/transcript.ts
@@ -151,6 +151,8 @@ export interface TranscriptStore {
   addUserMessage(text: string, sid?: string | null): void;
   addSystemMessage(text: string, sid?: string | null): void;
   addHistoryMessage(text: string, sid?: string | null): void;
+  /** 更早一页历史 prepend 到顶部（vanilla addHistoryMessage prepend 语义；loadBar 独立字段渲染在上方） */
+  prependHistoryMessage(text: string, sid?: string | null): void;
   setLoadBar(text: string | null, sid?: string | null): void;
   toggleRowOutput(sid: string | null, callId: string): void;
   expandRowContent(sid: string | null, callId: string): void;
@@ -433,6 +435,11 @@ export function createTranscriptStore(opts: { t?: TranslateFn } = {}): Transcrip
         st(sid).entries.push({ kind: "history", text });
       });
     },
+    prependHistoryMessage: (text, sid) => {
+      mutate(() => {
+        st(sid).entries.unshift({ kind: "history", text });
+      });
+    },
     setLoadBar: (text, sid) => {
       mutate(() => {
         st(sid).loadBar = text;