diff --git a/CHANGELOG.md b/CHANGELOG.md
index 51291d3c03..0ffddf2f9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4156,6 +4156,17 @@ This release closes that milestone with **439 merged pull requests**.
   missing; `verify-versions.yml` installs the uv version the backend image pins.
   ([#6588])
 
+- **tui:** `deerflow --print` and `--json` no longer drop words of an unquoted
+  message. Each flag took a single value and never read the positional words,
+  so `deerflow --print summarize this repo` sent only `summarize`,
+  `deerflow summarize this repo --print` exited 2 asking for a message on a
+  terminal, and with piped stdin the typed words were silently ignored. Both flags now take every word
+  that follows them and fall back to words given before them, as `--cli` does;
+  a typed message wins over piped stdin. A message split around the flag
+  (`deerflow hello --print there`) exits 2 with a hint to quote it, since its
+  word order cannot be recovered. Passing both `--print` and `--json` now exits
+  2 instead of running `--print` and dropping the `--json` message. ([#6636])
+
 ### Security
 
 - **authz:** Enforce permission checks on routes that only had authentication, and
@@ -9565,3 +9576,4 @@ with **180 merged pull requests** since the first 2.0 milestone tag.
 [#6611]: https://github.com/bytedance/deer-flow/pull/6611
 [#6613]: https://github.com/bytedance/deer-flow/pull/6613
 [#6635]: https://github.com/bytedance/deer-flow/pull/6635
+[#6636]: https://github.com/bytedance/deer-flow/pull/6636
diff --git a/CHANGELOG_zh.md b/CHANGELOG_zh.md
index 97a66fc5ef..a4b6b910b8 100644
--- a/CHANGELOG_zh.md
+++ b/CHANGELOG_zh.md
@@ -3193,6 +3193,15 @@
   规范化交给 uv，`2.1.0-rc0` 仍与 `2.1.0rc0` 匹配），缺少 `uv` 时直接失败；
   `verify-versions.yml` 会安装与 backend 镜像相同的固定 uv 版本。([#6588])
 
+- **TUI：** `deerflow --print` 和 `--json` 不再丢弃未加引号消息中的词。此前这两个
+  选项只接收一个值，也从不读取位置参数，因此 `deerflow --print summarize this repo`
+  只会发送 `summarize`，`deerflow summarize this repo --print` 在终端中会以退出码 2
+  要求提供消息，而有管道 stdin 时命令行上输入的词会被悄悄忽略。现在两个选项会接收
+  其后的所有词，并像 `--cli` 一样在没有值时使用选项之前的词；命令行上输入的消息
+  优先于管道 stdin。消息被选项分隔在两侧时（`deerflow hello --print there`），
+  由于词序无法还原，会以退出码 2 退出并提示加引号。同时传入 `--print` 和 `--json`
+  现在会以退出码 2 退出，而不是运行 `--print` 并丢弃 `--json` 的消息。([#6636])
+
 ### 安全
 
 - **鉴权：** 仅有认证而无权限校验的路由现在会强制执行权限检查，且
@@ -7690,3 +7699,4 @@ DeerFlow 2.0 是围绕"超级智能体"框架的彻底重写，核心包含子
 [#6611]: https://github.com/bytedance/deer-flow/pull/6611
 [#6613]: https://github.com/bytedance/deer-flow/pull/6613
 [#6635]: https://github.com/bytedance/deer-flow/pull/6635
+[#6636]: https://github.com/bytedance/deer-flow/pull/6636
diff --git a/backend/docs/TUI.md b/backend/docs/TUI.md
index 453d219df6..86bbbdf686 100644
--- a/backend/docs/TUI.md
+++ b/backend/docs/TUI.md
@@ -33,6 +33,12 @@ Launch modes:
 | `DEER_FLOW_TUI=1 deerflow` | Force the TUI via environment |
 | `DEER_FLOW_TUI_TRANSPARENT=1 deerflow` | Persist terminal-background rendering via environment |
 
+`--print` and `--json` keep every word of an unquoted message, and words before
+a bare flag (`deerflow summarize this repo --print`) are the message, as with
+`--cli`. A message given on the command line wins over piped stdin. Words on
+both sides of the flag are rejected with exit 2, since their order cannot be
+recovered. `--print` and `--json` cannot be combined; pick one output mode.
+
 If no TTY is available and no headless flag is given, `deerflow` prints guidance
 instead of hanging.
 
diff --git a/backend/packages/harness/deerflow/tui/cli.py b/backend/packages/harness/deerflow/tui/cli.py
index 208500c445..0eccbbbb69 100644
--- a/backend/packages/harness/deerflow/tui/cli.py
+++ b/backend/packages/harness/deerflow/tui/cli.py
@@ -55,21 +55,21 @@ def build_parser() -> argparse.ArgumentParser:
         epilog="Extension management: deerflow extensions --help",
         add_help=True,
     )
-    parser.add_argument("message", nargs="*", help="initial prompt for the TUI, or message in --cli mode")
-    parser.add_argument(
+    parser.add_argument("message", nargs="*", help="initial prompt for the TUI, or the message for --print, --json or --cli")
+    # One headless mode runs per invocation; refuse both so neither message is dropped.
+    headless = parser.add_mutually_exclusive_group()
+    headless.add_argument(
         "--print",
         dest="print",
-        nargs="?",
-        const=None,
+        nargs="*",
         default=_UNSET,
         metavar="MESSAGE",
         help="headless one-shot: print the final answer and exit (reads stdin if no MESSAGE)",
     )
-    parser.add_argument(
+    headless.add_argument(
         "--json",
         dest="json",
-        nargs="?",
-        const=None,
+        nargs="*",
         default=_UNSET,
         metavar="MESSAGE",
         help="headless streaming: emit newline-delimited JSON StreamEvents and exit",
@@ -100,6 +100,18 @@ def _strip_chat(argv: Sequence[str]) -> list[str]:
     return argv
 
 
+def _headless_message(parser: argparse.ArgumentParser, flag: str, values: list[str], positional: str | None) -> str | None:
+    """Return the words after a ``--print``/``--json`` flag, or else the positional words.
+
+    argparse loses the order between the flag's words and positional words, so a
+    message split around the flag is refused instead of reassembled by guess.
+    """
+    message = " ".join(values).strip() or None
+    if message and positional:
+        parser.error(f'{flag}: pass the message in one place, e.g. deerflow {flag} "your question"')
+    return message or positional
+
+
 def _truthy(value: object) -> bool:
     return isinstance(value, str) and value.strip().lower() in {"1", "true", "yes", "on"}
 
@@ -122,7 +134,7 @@ def plan_launch(
         parser.error("--recursion-limit requires --print, --json, or --cli")
 
     if args.print is not _UNSET:
-        message = args.print if isinstance(args.print, str) else None
+        message = _headless_message(parser, "--print", args.print, positional)
         if message is None and stdin_isatty:
             return LaunchPlan(mode="headless-help", reason="--print needs a MESSAGE argument or piped stdin.")
         return LaunchPlan(
@@ -135,7 +147,7 @@ def plan_launch(
         )
 
     if args.json is not _UNSET:
-        message = args.json if isinstance(args.json, str) else None
+        message = _headless_message(parser, "--json", args.json, positional)
         if message is None and stdin_isatty:
             return LaunchPlan(mode="headless-help", reason="--json needs a MESSAGE argument or piped stdin.")
         return LaunchPlan(
diff --git a/backend/tests/test_tui_cli.py b/backend/tests/test_tui_cli.py
index 00a153238e..7929dd99fa 100644
--- a/backend/tests/test_tui_cli.py
+++ b/backend/tests/test_tui_cli.py
@@ -67,6 +67,74 @@ def test_json_mode():
     assert p.message == "hello"
 
 
+@pytest.mark.parametrize("mode", ["--print", "--json"])
+def test_headless_unquoted_message_keeps_every_word(mode):
+    """An unquoted message must not be truncated to its first word."""
+    p = plan([mode, "summarize", "this", "repo"])
+    assert p.mode == mode.removeprefix("--")
+    assert p.message == "summarize this repo"
+    assert p.read_stdin is False
+
+
+@pytest.mark.parametrize("mode", ["--print", "--json"])
+def test_headless_message_before_the_flag_is_used(mode):
+    """Words before a bare --print/--json are the message, as with --cli."""
+    p = plan(["summarize", "this", "repo", mode])
+    assert p.mode == mode.removeprefix("--")
+    assert p.message == "summarize this repo"
+    assert p.read_stdin is False
+
+
+@pytest.mark.parametrize("mode", ["--print", "--json"])
+def test_headless_message_wins_over_piped_stdin(mode):
+    p = plan(["hello", mode], stdin_tty=False)
+    assert p.message == "hello"
+    assert p.read_stdin is False
+
+
+@pytest.mark.parametrize(
+    "argv",
+    [
+        ["hello", "--print", "there"],
+        ["--print", "hello", "--continue", "there"],
+        ["hello", "--json", "there"],
+    ],
+)
+def test_headless_message_split_around_the_flag_is_rejected(argv, capsys):
+    """Word order across the flag is lost by argparse, so refuse rather than guess."""
+    with pytest.raises(SystemExit) as exc:
+        plan(argv)
+    assert exc.value.code == 2
+    assert "pass the message in one place" in capsys.readouterr().err
+
+
+@pytest.mark.parametrize(
+    "argv",
+    [
+        ["--print", "hello", "--json", "world"],
+        ["--print", "--json", "hello"],
+        ["--json", "hello", "--print"],
+        ["hello", "--print", "--json"],
+    ],
+)
+def test_print_and_json_together_are_rejected(argv, capsys):
+    """Only one headless mode runs, so the other flag's message must not vanish."""
+    with pytest.raises(SystemExit) as exc:
+        plan(argv, stdin_tty=False)
+    assert exc.value.code == 2
+    assert "not allowed with argument" in capsys.readouterr().err
+
+
+@pytest.mark.parametrize("mode", ["--print", "--json"])
+def test_headless_blank_message_is_treated_as_missing(mode):
+    p = plan([mode, "  "])
+    assert p.mode == "headless-help"
+
+
+def test_headless_help_documents_multi_word_messages():
+    assert "--print [MESSAGE ...]" in build_parser().format_help()
+
+
 def test_force_tui_even_without_tty():
     p = plan(["--tui"], stdin_tty=False, stdout_tty=False)
     assert p.mode == "tui"