diff --git a/tools/check_cowork_screen.py b/tools/check_cowork_screen.py
index a7331be..5e54e74 100644
--- a/tools/check_cowork_screen.py
+++ b/tools/check_cowork_screen.py
@@ -87,6 +87,47 @@ def main() -> int:
             fails.append(f"thieu nut {name} tren thanh cong cu")
     print(f"nut tren thanh cong cu: {c.skills_btn.text()!r}, {c._new_btn.text()!r}")
 
+    # one heading on the files panel, with the chevron at its right — the
+    # drawing has "TỆP ĐẦU RA (3) ›" and nothing above it
+    from PySide6.QtCore import QPoint as _QP
+
+    hdr_w = c.output_section.header
+    chev = c._io_collapse_btn
+    same_row = abs(hdr_w.mapTo(c, _QP(0, 0)).y() - chev.mapTo(c, _QP(0, 0)).y()) <= 8
+    chev_right = chev.mapTo(c, _QP(0, 0)).x() > hdr_w.mapTo(c, _QP(0, 0)).x()
+    # Count what the panel actually shows as headings. Asking whether the old
+    # label is visible proved nothing: unparented, it reports invisible whether
+    # or not the code hides it.
+    from PySide6.QtWidgets import QLabel
+
+    heads = [l.text() for l in c._io_widget.findChildren(QLabel)
+             if l.isVisible() and l.text().strip()]
+    print(f"tieu de hien trong pane: {heads} | "
+          f"chevron cung hang={same_row} ben phai={chev_right}")
+    if heads:
+        fails.append(f"pane co tieu de thua ngoai '{hdr_w.text()}': {heads}")
+    if not (same_row and chev_right):
+        fails.append("chevron thu gon khong nam cuoi hang tieu de pane")
+
+    # the composer spans the screen, under BOTH columns — inside the chat
+    # column it stopped at the files panel's edge and shrank when files arrived
+    from PySide6.QtCore import QPoint
+
+    c._set_io_collapsed(False)
+    app.processEvents()
+    split = c.center_split
+    files_pane = split.widget(1)
+    comp_right = c.composer.mapTo(c, QPoint(c.composer.width(), 0)).x()
+    files_left = files_pane.mapTo(c, QPoint(0, 0)).x()
+    below = c.composer.mapTo(c, QPoint(0, 0)).y() > split.mapTo(c, QPoint(0, 0)).y()
+    spans = comp_right > files_left
+    print(f"o nhap: rong {c.composer.width()} / man {c.width()} | "
+          f"duoi splitter={below} | trai qua duoi pane tep={spans}")
+    if not below:
+        fails.append("o nhap khong nam duoi hang than")
+    if not spans:
+        fails.append("o nhap dung lai o mep pane tep, khong trai het man")
+
     print()
     for f in fails:
         print("FAIL  " + f)
diff --git a/ui/chat_panel.py b/ui/chat_panel.py
index f8e8ef7..e19bb86 100644
--- a/ui/chat_panel.py
+++ b/ui/chat_panel.py
@@ -190,15 +190,20 @@ class ChatPanel(QWidget):
         cc.addWidget(self.chat_view, 1)
         self.thinking = ThinkingIndicator()   # animated "working…" line while we wait
         cc.addWidget(self.thinking)
+        self.center_split = QSplitter(Qt.Horizontal)
+        self.center_split.addWidget(chat_col)
+        root.addWidget(self.center_split, 1)
+
+        # The composer spans the whole screen, under BOTH columns — that is how
+        # the drawing lays it out, and it is the reason the files panel can sit
+        # beside the transcript without narrowing what you type into. Inside the
+        # chat column it stopped at the panel's edge and the input shrank
+        # whenever files appeared.
         composer_wrap = QWidget()
         cwl = QVBoxLayout(composer_wrap)
         cwl.setContentsMargins(8, 4, 8, 8)
         cwl.addWidget(self.composer)
-        cc.addWidget(composer_wrap)
-
-        self.center_split = QSplitter(Qt.Horizontal)
-        self.center_split.addWidget(chat_col)
-        root.addWidget(self.center_split, 1)
+        root.addWidget(composer_wrap)
 
         # Right sidebar: Output files only (see below — Input is tracked but
         # not shown).
@@ -243,8 +248,15 @@ class ChatPanel(QWidget):
         self._io_collapse_btn.clicked.connect(lambda: self._set_io_collapsed(True))
         self._files_header = QLabel()
         self._files_header.setStyleSheet("font-weight:600;")
+        # The drawing gives this panel ONE heading — "TỆP ĐẦU RA (3) ›" — and
+        # the section already draws exactly that, count included. A separate
+        # "Files" label above it was the same thing said twice, so the section's
+        # own header moves onto this row and the collapse chevron sits at its
+        # right, where the drawing puts it. _files_header stays for the tabs
+        # that still label their panel, just not in this layout.
+        self._files_header.setVisible(False)
+        io_hdr.addWidget(self.output_section.header, 1)
         io_hdr.addWidget(self._io_collapse_btn)
-        io_hdr.addWidget(self._files_header, 1)
         # The plan now shows INLINE in the conversation (an expandable block whose
         # steps tick off as they complete), not in this right panel — so it's kept
         # out of the layout here. The object stays (its set_steps/clear calls are