fix(tui): derive /help text from the command registry (#4327)

The /help string was hardcoded and had drifted from BUILTIN_COMMANDS,
omitting six real commands (help, switch, resume, uploads, artifacts,
details) and ordering the rest differently from the picker. Generate the
command line from the registry so /help can never fall out of sync again,
and add parity tests that guard against future drift.

backend/packages/harness/deerflow/tui/app.py

@@ -20,6 +20,7 @@ from textual.widgets.option_list import Option
 
 from deerflow.runtime.goal import parse_goal_command
 
+from .command_registry import format_command_help
 from .input_history import InputHistory
 from .render import render_header, render_status, render_transcript
 from .runtime import stream_actions
@@ -36,7 +37,8 @@ from .view_state import (
 )
 from .widgets.composer import ComposerInput
 
-_HELP_TEXT = "Commands:  /new  /clear  /threads  /goal  /model  /skills  /tools  /mcp  /memory  /usage  /config  /quit\nKeys:  Enter send · Ctrl+C interrupt or quit · Ctrl+L redraw · / commands · Esc close overlay"
+_HELP_KEYS = "Keys:  Enter send · Ctrl+C interrupt or quit · Ctrl+L redraw · / commands · Esc close overlay"
+_HELP_TEXT = f"{format_command_help()}\n{_HELP_KEYS}"
 
 
 class SelectScreen(ModalScreen):

backend/packages/harness/deerflow/tui/command_registry.py

@@ -57,6 +57,17 @@ BUILTIN_COMMANDS: tuple[Command, ...] = (
 _BUILTIN_NAMES = frozenset(c.name for c in BUILTIN_COMMANDS)
 
 
+def format_command_help() -> str:
+    """One-line summary of every built-in slash command, for ``/help``.
+
+    Derived from :data:`BUILTIN_COMMANDS` so the help text can never drift out
+    of sync with the registry (and, therefore, the picker). Adding a built-in
+    surfaces it in ``/help`` automatically.
+    """
+    names = "  ".join(f"/{command.name}" for command in BUILTIN_COMMANDS)
+    return f"Commands:  {names}"
+
+
 def build_registry(skills: list[dict]) -> list[Command]:
     """Merge built-ins with one command per enabled skill."""
     commands = list(BUILTIN_COMMANDS)

backend/tests/test_tui_app.py

@@ -95,10 +95,31 @@ async def test_help_command_renders_system_row_without_calling_agent():
 
     assert any(r.kind == "system" for r in app.state.rows)
     assert any(r.kind == "system" and "/clear" in r.text for r in app.state.rows)
+    # Commands previously missing from the hardcoded help string must now appear,
+    # since the help text is derived from the command registry.
+    help_rows = [r for r in app.state.rows if r.kind == "system"]
+    for command in ("/help", "/resume", "/switch", "/uploads", "/artifacts", "/details"):
+        assert any(command in r.text for r in help_rows), command
     # /help must not produce a user turn or start streaming.
     assert not any(r.kind == "user" for r in app.state.rows)
 
 
+@pytest.mark.asyncio
+async def test_help_text_matches_command_registry():
+    from deerflow.tui.command_registry import format_command_help
+
+    app = DeerFlowTUI(_FakeSession(), LaunchPlan(mode="tui"))
+    async with app.run_test() as pilot:
+        await pilot.pause()
+        for ch in "/help":
+            await pilot.press(ch)
+        await pilot.press("enter")
+        await _wait_until(lambda: any(r.kind == "system" for r in app.state.rows), pilot)
+
+    expected = format_command_help()
+    assert any(r.kind == "system" and expected in r.text for r in app.state.rows)
+
+
 @pytest.mark.asyncio
 async def test_clear_command_clears_display_without_resetting_thread_or_calling_agent():
     session = _FakeSession()

backend/tests/test_tui_command_registry.py

@@ -4,6 +4,7 @@ from deerflow.tui.command_registry import (
     BUILTIN_COMMANDS,
     build_registry,
     filter_commands,
+    format_command_help,
     resolve,
 )
 
@@ -115,3 +116,38 @@ def test_goal_builtin_takes_precedence_over_skill():
 
     assert [command.name for command in registry].count("goal") == 1
     assert resolve("/goal finish", skills=["goal"]).kind == "builtin"
+
+
+# --------------------------------------------------------------------------- #
+# /help text <-> registry parity
+# --------------------------------------------------------------------------- #
+
+
+def test_help_lists_every_builtin_command():
+    help_line = format_command_help()
+    # Every registered built-in must be advertised in /help; this is the guard
+    # against the help text silently drifting from BUILTIN_COMMANDS.
+    for command in BUILTIN_COMMANDS:
+        assert f"/{command.name}" in help_line
+
+
+def test_help_lists_only_builtin_commands():
+    help_line = format_command_help()
+    slugs = [token[1:] for token in help_line.split() if token.startswith("/")]
+    assert set(slugs) == {command.name for command in BUILTIN_COMMANDS}
+
+
+def test_help_preserves_registry_order():
+    help_line = format_command_help()
+    slugs = [token[1:] for token in help_line.split() if token.startswith("/")]
+    assert slugs == [command.name for command in BUILTIN_COMMANDS]
+
+
+def test_help_has_no_duplicate_commands():
+    help_line = format_command_help()
+    slugs = [token[1:] for token in help_line.split() if token.startswith("/")]
+    assert len(slugs) == len(set(slugs))
+
+
+def test_help_starts_with_commands_label():
+    assert format_command_help().startswith("Commands:  /")