diff --git a/Agent.md b/Agent.md
index 0bf1fe4..20815f9 100644
--- a/Agent.md
+++ b/Agent.md
@@ -66,7 +66,7 @@ EMRG is a self-evolving AI agent architecture experiment. Python implementation,
   - Streaming chat with delta rendering (16ms batching), markdown on done (marked + DOMPurify + local highlight.js subset), tool call status cards (2000-char truncation + expand)
   - Session list/switch/new/delete + right-click rename (context menu, #423) synced with daemon; own-stream busy lock (G65); broadcast streams from other clients tagged "来自其他客户端"
   - Disconnect/reconnect: red status dot, auto daemon respawn (stale-port detection), session resume, input bar restored on disconnect (no 30s fake-timeout)
-  - Unit tests `npm test` (172: 43 daemon_client + 17 conn-manager + 22 app-commands + 55 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state); RESPONSE_TYPES mirror daemon protocol verified against `daemon.py`
+  - Unit tests `npm test` (175: 43 daemon_client + 19 conn-manager + 22 app-commands + 56 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state); RESPONSE_TYPES mirror daemon protocol verified against `daemon.py`
 - **Auto project tracking** — Automatically detects and records working directories; project-scoped sessions
 - **Rant-driven evolution** — User feedback via `/rant` drives automatic self-improvement cycles
 - **Headless GitHub auth** — Non-interactive evolution auto-extracts `GH_TOKEN` from git credential store (osxkeychain / credential helper); PR comment/LGTM queries fall back to REST API (GraphQL needs `read:org` scope)
@@ -94,7 +94,7 @@ pkill -f "emrg.server"; rm -f ~/.emrg/emrgd.port; python -m emrg
 ```
 
 Python: `uv run pytest tests/ -v` (680) — import check: `uv run python -c "from emrg.client.app import run_client"`
-GUI: `cd emrg/gui && npm test` (172: 43 daemon_client + 17 conn-manager + 22 app-commands + 55 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`
+GUI: `cd emrg/gui && npm test` (175: 43 daemon_client + 19 conn-manager + 22 app-commands + 56 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`
 CI: `uv run pytest` + 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)
 
diff --git a/README.cn.md b/README.cn.md
index 40020a5..1579341 100644
--- a/README.cn.md
+++ b/README.cn.md
@@ -282,7 +282,7 @@ uv run python -m emrg     # 启动 TUI
 cd emrg/gui
 npm ci               # 安装依赖（生产模式可 --omit=dev）
 npm start            # 启动 GUI（自动拉起 daemon）
-npm test             # 运行 Node 测试（172 项：43 daemon_client + 17 conn-manager + 22 app-commands + 55 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state；集成测试在 CI 跑，本地可 npm run test:integration）
+npm test             # 运行 Node 测试（175 项：43 daemon_client + 19 conn-manager + 22 app-commands + 56 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state；集成测试在 CI 跑，本地可 npm run test:integration）
 ```
 
 CI 通过 GitHub Actions 自动运行测试并检查冲突标记（`.github/workflows/test.yml`）。
diff --git a/README.md b/README.md
index 5278347..b1c4b60 100644
--- a/README.md
+++ b/README.md
@@ -281,7 +281,7 @@ uv run python -m emrg     # launch TUI
 cd emrg/gui
 npm ci               # install deps (production: --omit=dev)
 npm start            # launch GUI (auto-starts daemon)
-npm test             # run Node tests (172: 43 daemon_client + 17 conn-manager + 22 app-commands + 55 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state; integration runs in CI, local: npm run test:integration)
+npm test             # run Node tests (175: 43 daemon_client + 19 conn-manager + 22 app-commands + 56 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config + 7 gui-state; integration runs in CI, local: npm run test:integration)
 ```
 
 CI runs tests and checks for conflict markers automatically via GitHub Actions (`.github/workflows/test.yml`).
diff --git a/emrg/gui/conn-manager.js b/emrg/gui/conn-manager.js
index 469f94b..42cad02 100644
--- a/emrg/gui/conn-manager.js
+++ b/emrg/gui/conn-manager.js
@@ -111,10 +111,16 @@ class ConnManager {
   // close(sid)：conn.close（断开 ws）→ 移除。返回是否有关闭对象。
   // 标记 _intentionalClose：主动关闭（切走/删除）不触发 renderer 断线横幅
   // （桥检查该标记；真断连/daemon 重启的 disconnected 照常转发）。
+  // P6（rant 15:07:19 边界）：关闭在忙连接先 cancel 再 close——流式进行中
+  // （ownStream）先发 cancel 让 daemon 停流，再断 ws，防半途断线留脏状态
+  // （fire-and-forget：断连/ws 已 null 时忽略，不阻塞同步 close 语义）。
   close(sid) {
     const entry = this._conns.get(sid);
     if (!entry) return false;
     this._cancelSingleRetry(sid); // 主动关闭 → 取消该会话的独立退避
+    if (entry.conn.ownStream && entry.conn.ws) {
+      try { entry.conn.sendCommand("cancel"); } catch { /* 断连时忽略 */ }
+    }
     entry.conn._intentionalClose = true;
     entry.conn.close();
     this._conns.delete(sid);
diff --git a/emrg/gui/main.js b/emrg/gui/main.js
index d1b00e0..513175a 100644
--- a/emrg/gui/main.js
+++ b/emrg/gui/main.js
@@ -13,7 +13,7 @@ const { spawn } = require("child_process");
 const { parse: parseToml, stringify: stringifyToml } = require("smol-toml");
 const { generateSessionId, SESSION_ID_RE } = require("./daemon_client");
 const { ConnManager } = require("./conn-manager");
-const { guiStatePath, sanitizeOpenSessions, saveGuiState } = require("./gui-state");
+const { guiStatePath, sanitizeOpenSessions, saveGuiState, DEFAULT_CAP } = require("./gui-state");
 const APP_VERSION = require("./package.json").version;
 
 // ── 单实例锁（G85/G120：第二个实例退出并 focus 已有窗口）──
@@ -299,6 +299,14 @@ vision = false
 
     ipcMain.handle("emrg:switchSession", async (_e, { sessionId, projectPath } = {}) => {
       if (!validateSessionId(sessionId)) throw new Error("invalid session_id");
+      // P6（rant 15:07:19 边界）：projectPath 校验（跨项目打开时传项目路径）
+      if (projectPath !== undefined && (typeof projectPath !== "string" || !projectPath.trim())) {
+        throw new Error("invalid project path");
+      }
+      // P6（rant 15:07:19 上限 20）：显式打开新会话超限 → 提示不自动关（已打开 sid 复用不拦）
+      if (openSessions.size >= DEFAULT_CAP && !openSessions.has(sessionId)) {
+        throw new Error(`too many open sessions (${DEFAULT_CAP}) — close some first`);
+      }
       // G65：自有流运行中禁止切会话（每连接独立锁，查当前激活连接）
       if (connManager?.get(currentSessionId)?.ownStream) throw new Error("stream in progress — cannot switch");
       const prevSid = currentSessionId;
@@ -359,6 +367,10 @@ vision = false
     }));
 
     ipcMain.handle("emrg:newSession", async (_e, { projectPath } = {}) => {
+      // P6（rant 15:07:19 边界）：projectPath 校验（新建会话指定项目时）
+      if (projectPath !== undefined && (typeof projectPath !== "string" || !projectPath.trim())) {
+        throw new Error("invalid project path");
+      }
       // G14/G81：本地生成 session_id（无 new_session 消息）
       const sid = generateSessionId();
       // 同步 main 侧会话状态：重连后 resume 正确会话（G41）+ 窗口标题（G109）
diff --git a/emrg/gui/renderer/js/app.js b/emrg/gui/renderer/js/app.js
index fd08faa..91aacad 100644
--- a/emrg/gui/renderer/js/app.js
+++ b/emrg/gui/renderer/js/app.js
@@ -628,7 +628,8 @@ const App = (() => {
       Sidebar.highlight(sid);
       setComposerDisabled(false); // 防御性：独立调用 switchSession 也确保输入框可用
     } catch (e) {
-      Chat.addSystemMessage(_t("app.switchFailed", { msg: e.message }));
+      // P6（rant 15:07:19 上限 20）：超限提示本地化（main 抛 too many open sessions）
+      Chat.addSystemMessage(/too many open sessions/i.test(e.message || "") ? _t("app.tooManyOpenSessions") : _t("app.switchFailed", { msg: e.message }));
     }
   }
 
diff --git a/emrg/gui/renderer/js/i18n.js b/emrg/gui/renderer/js/i18n.js
index 6ccea2a..8122e78 100644
--- a/emrg/gui/renderer/js/i18n.js
+++ b/emrg/gui/renderer/js/i18n.js
@@ -312,6 +312,7 @@ const I18N = (() => {
       "app.switched": "已切换对话。",
       "app.sessionDisconnected": "该会话连接已断开，正在自动重连…",
       "app.switchFailed": "切换对话失败了：{msg}",
+      "app.tooManyOpenSessions": "打开的会话已达上限（20），请先关闭一些再打开。",
       "app.newFailed": "新建对话失败了：{msg}",
       "app.deleteFailed": "删除失败了：{msg}",
       "app.rename": "✏️ 重命名",
@@ -632,6 +633,7 @@ const I18N = (() => {
       "app.switched": "Conversation switched.",
       "app.sessionDisconnected": "This session's connection is lost — reconnecting automatically…",
       "app.switchFailed": "Failed to switch: {msg}",
+      "app.tooManyOpenSessions": "Too many open sessions (20) — close some first.",
       "app.newFailed": "Failed to create conversation: {msg}",
       "app.deleteFailed": "Delete failed: {msg}",
       "app.rename": "✏️ Rename",
diff --git a/emrg/gui/test/conn-manager.test.js b/emrg/gui/test/conn-manager.test.js
index b008cb6..0b75aa5 100644
--- a/emrg/gui/test/conn-manager.test.js
+++ b/emrg/gui/test/conn-manager.test.js
@@ -180,6 +180,29 @@ test("P2 close: 主动关闭标记 _intentionalClose 且不触发重启恢复",
   assert.strictEqual(recoverCalls, 0, "intentional close must not trigger restart recovery");
 });
 
+test("P6 close: 在忙连接（ownStream）先 cancel 再 close", async () => {
+  const manager = new ConnManager({ projectDir: tmpHome });
+  // 停用自动恢复（本测试专注 close 行为；单连接全关会触发重启判定）
+  manager.recoverAll = async () => {};
+  const busy = await driveOpen(manager, "sess-busy", "/proj/a");
+  busy.conn.ownStream = true;
+  busy.sessionWs.sent.length = 0; // 清空历史帧，聚焦 close 行为
+  assert.strictEqual(manager.close("sess-busy"), true);
+  const lastFrame = JSON.parse(busy.sessionWs.sent.at(-1));
+  assert.strictEqual(lastFrame.type, "cancel", "busy close must send cancel before disconnect");
+  assert.strictEqual(busy.conn.connected, false, "close must disconnect the ws");
+});
+
+test("P6 close: 空闲连接 close 不 cancel", async () => {
+  const manager = new ConnManager({ projectDir: tmpHome });
+  manager.recoverAll = async () => {};
+  const idle = await driveOpen(manager, "sess-idle", "/proj/a");
+  idle.sessionWs.sent.length = 0;
+  assert.strictEqual(manager.close("sess-idle"), true);
+  assert.strictEqual(idle.sessionWs.sent.length, 0, "idle close must not send cancel");
+  assert.strictEqual(idle.conn.connected, false, "close must disconnect the ws");
+});
+
 test("P2 open: 断连残留连接 → 关闭重开（不返回 stale conn）", async () => {
   const manager = new ConnManager({ projectDir: tmpHome });
   const s1 = await driveOpen(manager, "sess-1", "/proj/a");
diff --git a/emrg/gui/test/renderer.smoke.test.js b/emrg/gui/test/renderer.smoke.test.js
index d086b8a..390dc0d 100644
--- a/emrg/gui/test/renderer.smoke.test.js
+++ b/emrg/gui/test/renderer.smoke.test.js
@@ -1457,3 +1457,22 @@ test("P5 slice 2: 删除项目 — 受保护 emrg 提示不可删；普通项目
   assert.strictEqual(removeCalls[0] && removeCalls[0].name, "mem", "project name passed");
   assert.strictEqual(removeCalls[0] && removeCalls[0].path, "/p/mem", "project path passed");
 });
+
+// ── P6（rant 15:07:19）：上限 20 超限提示本地化 + 边界 ──
+
+test("P6: switchSession 超限（too many open sessions）→ 本地化提示（非英文原始错误）", async () => {
+  const { ctx, els } = makeSandbox({
+    switchSession: async () => { throw new Error("too many open sessions (20) — close some first"); },
+  });
+  await tick();
+  await vm.runInContext('App.switchSession("s-over", { projectPath: "/p/x" })', ctx);
+  await tick();
+  // Chat.addSystemMessage 渲染进 chat-view 容器（系统消息节点 textContent）
+  const texts = els["chat-view"].children.map((c) => c.textContent || "");
+  const last = texts[texts.length - 1] || "";
+  assert.ok(
+    last.includes("上限") || last.includes("Too many open sessions"),
+    "localized over-limit message shown, got: " + last
+  );
+  assert.ok(!last.includes("close some first"), "raw english error must not leak: " + last);
+});
diff --git a/emrg/server/evolution_prompt.md b/emrg/server/evolution_prompt.md
index ab1169a..1e4d81a 100644
--- a/emrg/server/evolution_prompt.md
+++ b/emrg/server/evolution_prompt.md
@@ -392,6 +392,7 @@ When reading rants, follow these rules:
 > - GUI open-sessions sidebar + gui_state restore (#639 GUI 多会话 rant 2026-08-10T15:07:19 P4 slice 2 读路径/侧边栏：main.js `restoreOpenSessions`（init 读 gui_state.json → 重开有效条目 cap 20 + resume 重订阅 → 失效跳过 + 重写盘 → activeSid 恢复/回退最近有效 → 窗口标题同步）+ `broadcastOpenSessions`（打开/激活/关闭/删除/新建每次变更推 `open_sessions` 事件给 renderer）+ init 返回 `open_sessions` + `active_sid`（renderer 直接采用恢复激活会话，免 switchSession IPC 往返）；sidebar.js `renderOpenSessions`（侧边栏顶部跨项目打开会话区：项目名/会话标题、lastActive 倒序、激活高亮、点击切换、右键关闭保留数据/重命名/删除）+ highlight 扩展覆盖；app.js `state.openSessions` + `open_sessions` 事件 + `closeOpenSession`（断开+释放容器+保留磁盘数据；关激活会话 → 切最近打开会话否则新建）+ showOpenSessionsMenu；index.html `#open-sessions` + i18n zh/en + CSS；+4 测试 renderer.smoke 46→50 + mock 升级（querySelectorAll DFS 类选择器 + classList.toggle 忠实 force）；GUI 163→167 三文档同步；680 pytest 全绿；P4 完成，P5-P6 待续) ✅
 > - GUI open-session dialog project→session (#641 GUI 多会话 rant 2026-08-10T15:07:19 P5 slice 1：打开会话弹窗两步——`showOpenSessionDialog`（listProjects → 项目行含路径 hint + 底部"＋ 新建项目…"）+ `showProjectSessions`（listProjectSessions(cwd=projectPath) → created_at 倒序 → 点击 switchSession 复用连接）；main.js `emrg:listProjectSessions`/`emrg:registerProject` IPC（G121 目录可写校验；list_sessions(cwd) 轻量命令 → daemon 隐式 `_touch_project` 注册，零 daemon 改动，**不调 init_auto_evolve** 防意外建演化任务）；preload 暴露两 API；app.js `/open` 指令（commands 15→16）+ bindUi 初始化；i18n zh/en 10 条 + cmd.open.hint；+2 测试 renderer.smoke 50→52（项目→会话下钻 / 无项目提示）；GUI 167→169 三文档同步；680 pytest 全绿；P5 剩余=slice 2 新建会话 + 删除项目) ✅
 > - GUI new-session dialog + delete-project protected guard (#642 GUI 多会话 rant 2026-08-10T15:07:19 P5 slice 2：**新建会话弹窗** `showNewSessionDialog`（listProjects 活跃序 → 点选即 `App.newSession({projectPath})`；底部"＋ 新建项目…" → pickProjectDir → registerProject → 同路径新建）+ index.html `#new-session-dialog` + 打开弹窗顶部"＋ 新建会话…"入口；**删除项目**：打开弹窗项目行右侧删除按钮 → 受保护守卫（内置 project `emrg` / 内置 task `emrg-task` 提示"系统项目不可删除"，不调 API；`.emrg` 非内置可删）→ 确认弹窗（数据保留可恢复）→ main.js `emrg:removeProject` IPC（关闭该项目已打开会话连接 + 移出簿记 + 写盘 + 激活被关 → renderer 切相邻/新建 + 广播 open_sessions）→ daemon `remove_project`（P1 已备）；**slice-1 补洞**：switchSession/sendMessage 带 per-session projectPath（跨项目 resume 用项目 cwd 非全局 projectDir）；newSession 接受 projectPath（首条消息前即记簿记）；i18n zh/en 11 条；+3 测试 renderer.smoke 52→55（新建会话选项目 / 新建项目→注册→新建 / 删除项目受保护+普通确认）；GUI 169→172 三文档同步；680 pytest 全绿；P5 完成，P6 收尾待续) ✅
+> - GUI multi-session P6 finalize (#643 GUI 多会话 rant 2026-08-10T15:07:19 收尾边界：①**关闭在忙连接先 cancel 再 close**——ConnManager.close() 检测 `conn.ownStream && conn.ws` 先发 cancel（fire-and-forget 吞断连异常，不阻塞同步 close 语义），防流式半途断线留脏状态；②**上限 20 超限提示不自动关**——switchSession 显式打开新会话时 `openSessions.size >= DEFAULT_CAP && !openSessions.has(sid)` → 抛 "too many open sessions (20) — close some first"（已打开 sid 复用不拦；sendMessage/newSession 创建路径不拦）；renderer 识别该错误 → 本地化 `app.tooManyOpenSessions` zh/en（不再漏英文原始错误）；③**projectPath 校验**——switchSession/newSession IPC 收 projectPath 时校验 string 非空；+3 测试（conn-manager 17→19：忙 close 发 cancel / 空闲 close 不 cancel；renderer.smoke 55→56：超限本地化提示）；GUI 172→175 三文档同步；680 pytest 全绿；P1-P6 全部完成，验收清单剩余宿主实测项) ✅
 
 #### 2.2 Latest GitHub code changes