diff --git a/USAGE.md b/USAGE.md
index 51d58cf..b793d85 100644
--- a/USAGE.md
+++ b/USAGE.md
@@ -45,7 +45,8 @@ ykanban <path>
 ```
 
 - Exactly one argument is accepted. A relative path is resolved against the
-  current working directory, so `ykanban .` opens the current folder.
+  current working directory, so `ykanban .` opens the current folder (but see
+  [macOS](#macos) when starting through `open`).
 - YKanBan looks for `.ykanban` **only in `<path>` itself**; it does not search
   parent folders the way Git does.
 - There are no command-line options. An argument starting with `-` is never
@@ -57,7 +58,7 @@ instead:
 
 | Page | When |
 |---|---|
-| Invalid arguments | No argument, more than one argument, an empty argument, or an argument starting with `-` (including `--help`). Shows the usage line. |
+| Invalid arguments | No argument, more than one argument, an empty or whitespace-only argument, an argument starting with `-` (including `--help`), or a path the operating system cannot represent (for example one containing a NUL character). Shows the usage line. |
 | Folder not found | `<path>` does not exist or is not a folder. |
 | No workspace here | `<path>` exists but has no `.ykanban`. The **Initialize workspace** button creates one, with the columns To Do / In Progress / Done (named in the current interface language). |
 | Workspace locked | Another YKanBan window already has this workspace open. Close that window first. |
@@ -80,12 +81,17 @@ Double-clicking `YKanBan.app` starts it without a path, so it only shows the
 Launch Services or by running the executable inside the bundle:
 
 ```sh
-open -a YKanBan --args /path/to/project
+open -n -a YKanBan --args /path/to/project
 /Applications/YKanBan.app/Contents/MacOS/YKanBan /path/to/project
 ```
 
-`open -a YKanBan` finds the app once it is in `/Applications` (or another
-folder Launch Services knows about).
+- Keep `-n`: without it, `open` only brings an already running YKanBan to
+  the front and drops the path, instead of starting another window.
+- Give `open` an **absolute** path. An app started by `open` runs in `/`, so
+  `open -n -a YKanBan --args .` opens `/`, not the current folder. Running the
+  executable inside the bundle resolves relative paths normally.
+- `open -a YKanBan` finds the app once it is in `/Applications` (or another
+  folder Launch Services knows about).
 
 ## Workspaces, Git and backups
 
diff --git a/docs/ACCEPTANCE.md b/docs/ACCEPTANCE.md
index 3721c8e..33ed957 100644
--- a/docs/ACCEPTANCE.md
+++ b/docs/ACCEPTANCE.md
@@ -46,7 +46,7 @@
 
 ## B. 启动与错误页（M4 / M4R）
 
-- [ ] 无参数、两个参数、`--help`、`-x`、空字符串参数 → 参数错误页，显示 `Usage: ykanban <path>`
+- [ ] 无参数、两个参数、`--help`、`-x`、空字符串参数、纯空格参数 → 参数错误页，显示 `Usage: ykanban <path>`
 - [ ] 不存在的路径、指向文件的路径 → 目录不存在页
 - [ ] 相对路径（如 `ykanban .`）按当前目录解析
 - [ ] 无 `.ykanban` 的文件夹 → 未初始化页；点"初始化"后进入看板，预置三列
@@ -98,5 +98,5 @@
 - [ ] 产物：`YKanBan-<版本>-win-x64.zip`、`-linux-x64.tar.gz`、`-osx-x64.tar.gz`、`-osx-arm64.tar.gz`
 - [ ] Windows：解压后 `YKanBan.exe <path>` 可直接运行（自包含，无需安装 .NET）
 - [ ] Linux：解压后 `./YKanBan <path>` 可运行（可执行位保留）
-- [ ] macOS：解除隔离后 `open -a YKanBan --args <path>` 与直接运行包内可执行文件均可用；双击 `.app` 只显示参数错误页
+- [ ] macOS：解除隔离后 `open -n -a YKanBan --args <绝对路径>` 与直接运行包内可执行文件均可用；双击 `.app` 只显示参数错误页
 - [ ] 故意让某平台测试失败 → 该 RID 无产物，其余 RID 不受影响
diff --git a/docs/PLAN.md b/docs/PLAN.md
index 303e371..3fc195a 100644
--- a/docs/PLAN.md
+++ b/docs/PLAN.md
@@ -122,7 +122,7 @@ card_tags: (card_id, tag_id) 复合主键，双向 ON DELETE CASCADE
   - 恰好一个位置参数为合法；相对路径以进程当前工作目录解析为绝对路径
   - 无参数、多于一个参数、或参数以 `-` 开头（含 `--help` 等任何选项形式）→ **参数错误页**
   - 路径不存在或存在但不是目录 → 目录不存在页
-- macOS 双击 `.app` 时无参数，只会显示参数错误页——已接受（纯命令行定位）；USAGE.md 说明 macOS 启动方式（`open -a YKanBan --args <path>` 或直接运行包内可执行文件）
+- macOS 双击 `.app` 时无参数，只会显示参数错误页——已接受（纯命令行定位）；USAGE.md 说明 macOS 启动方式：`open -n -a YKanBan --args <绝对路径>` 或直接运行包内可执行文件（`-n` 保证已有实例运行时仍另起实例；经 `open` 启动时当前目录为 `/`，故须绝对路径）
 - 窗口标题：`工作区名 - YKanBan`；无有效工作区（错误页状态）时仅 `YKanBan`
 
 ### 4.2 连接管理
@@ -398,4 +398,4 @@ phrase  := '"' 任意文本 '"'   （内部支持转义：\" → 字面引号，
 2. 备份/迁移必须同时复制 `ykanban.db`、`ykanban.db-wal`、`ykanban.db-shm` 三个文件；不支持将工作区放在网络共享（SMB/NFS）上
 3. 搜索语法全文（文法、语义、`word` 字符集、转义规则、保留字、大小写折叠、严格校验与非法表达式清单、错误对话框行为，见 §6）
 4. 命令行启动规则（`ykanban <path>`；参数规则与各错误页，见 §4.1）
-5. macOS 启动方式（`open -a YKanBan --args <path>` 或直接运行包内可执行文件；双击 `.app` 只会显示参数错误页）
+5. macOS 启动方式（`open -n -a YKanBan --args <绝对路径>` 或直接运行包内可执行文件；`-n` 保证另起实例，`open` 启动时当前目录为 `/` 故须绝对路径；双击 `.app` 只会显示参数错误页）
diff --git a/packaging/package.sh b/packaging/package.sh
index 03fbfbf..627befb 100755
--- a/packaging/package.sh
+++ b/packaging/package.sh
@@ -5,7 +5,7 @@
 #
 # win-x64   -> YKanBan-<version>-win-x64.zip     (folder YKanBan-<version>-win-x64/)
 # linux-x64 -> YKanBan-<version>-linux-x64.tar.gz (folder YKanBan-<version>-linux-x64/)
-# osx-*     -> YKanBan-<version>-<rid>.tar.gz     (YKanBan.app bundle, ad-hoc signed when codesign exists)
+# osx-*     -> YKanBan-<version>-<rid>.tar.gz     (YKanBan.app bundle, ad-hoc signed when possible)
 #
 # tar.gz keeps the executable bit, which a plain zip artifact upload would lose.
 set -euo pipefail
@@ -28,9 +28,15 @@ trap 'rm -rf "$staging"' EXIT
 case "$rid" in
   win-*)
     cp -R "$publish_dir" "$staging/$name"
-    # Compress-Archive is available on every Windows host, unlike zip.
-    powershell -NoProfile -Command \
-      "Compress-Archive -Path '$(cygpath -w "$staging/$name" 2>/dev/null || echo "$staging/$name")' -DestinationPath '$(cygpath -w "$output_dir/$name.zip" 2>/dev/null || echo "$output_dir/$name.zip")' -Force"
+    rm -f "$output_dir/$name.zip"
+    # 7-Zip ships on the Windows runners and writes '/' entry separators;
+    # Windows PowerShell 5.1's Compress-Archive writes '\', which breaks
+    # extraction outside Windows.
+    if ! command -v 7z > /dev/null 2>&1; then
+      echo "7z not found" >&2
+      exit 1
+    fi
+    (cd "$staging" && 7z a -tzip -bso0 -bsp0 "$output_dir/$name.zip" "$name")
     ;;
   linux-*)
     cp -R "$publish_dir" "$staging/$name"
@@ -44,8 +50,12 @@ case "$rid" in
     chmod +x "$app/Contents/MacOS/YKanBan"
     sed "s/@VERSION@/${version}/g" "$script_dir/macos/Info.plist" > "$app/Contents/Info.plist"
     if command -v codesign > /dev/null 2>&1; then
-      # Ad-hoc signature: unsigned arm64 code does not run at all.
-      codesign --force --deep --sign - "$app"
+      # Ad-hoc signature for the bundle. Not fatal: the SDK already ad-hoc
+      # signs the apphost, which is all arm64 needs to run, and --deep may
+      # trip over the non-Mach-O files in Contents/MacOS.
+      if ! codesign --force --deep --sign - "$app"; then
+        echo "warning: ad-hoc signing of YKanBan.app failed; packing it unsigned" >&2
+      fi
     fi
     tar -C "$staging" -czf "$output_dir/$name.tar.gz" YKanBan.app
     ;;