diff --git a/src/gui/_home.py b/src/gui/_home.py
index a30af7a..b59aa8e 100644
--- a/src/gui/_home.py
+++ b/src/gui/_home.py
@@ -279,7 +279,16 @@ def _home_page() -> None:
             digest = hashlib.sha1(
                 name.encode("utf-8"), usedforsecurity=False,
             ).hexdigest()[:10]
-            col_name, col_size, col_x = st.columns([8, 1.6, 0.55])
+            # X button on the LEFT of the row per UX feedback —
+            # ``✕ | filename + chip | size``.
+            col_x, col_name, col_size = st.columns([0.55, 8, 1.6])
+            if col_x.button(
+                "✕",
+                key=f"_home_remove_{digest}",
+                help=f"Remove {name}",
+                type="tertiary",
+            ):
+                to_remove = name
             col_name.markdown(
                 '<div class="dt-file-row">'
                 f'<span class="dt-file-icon-chip">{_DOC_SVG}</span>'
@@ -294,13 +303,6 @@ def _home_page() -> None:
                 '</span></div>',
                 unsafe_allow_html=True,
             )
-            if col_x.button(
-                "✕",
-                key=f"_home_remove_{digest}",
-                help=f"Remove {name}",
-                type="tertiary",
-            ):
-                to_remove = name
         # In-card "Add more files" — clicks the (off-screen)
         # ``stFileUploaderDropzoneInput`` so the OS file picker opens.
         # Inline ``onclick`` would be cleanest but Streamlit's HTML
diff --git a/src/gui/components/_legacy.py b/src/gui/components/_legacy.py
index 2661bc2..67b1fb5 100644
--- a/src/gui/components/_legacy.py
+++ b/src/gui/components/_legacy.py
@@ -179,6 +179,50 @@ body, .stApp {
     background: #f5f4ef !important;
 }
 
+/* Brand block at the top of the sidebar (mockup §brand) — a 28px
+   ink-filled rounded square with the wordmark "D" + "DataTools"
+   text. Injected into ``[data-testid="stSidebarHeader"]`` by the JS
+   below; ``stLogoSpacer`` is hidden so the brand block takes its
+   place flush against the left edge of the sidebar header. */
+.dt-brand {
+    display: flex !important;
+    align-items: center;
+    gap: 10px;
+    padding: 0 0 0 4px;
+    margin: 0;
+    height: 100%;
+    flex: 1;
+}
+.dt-brand-mark {
+    width: 28px;
+    height: 28px;
+    border-radius: 7px;
+    background: var(--ink);
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    color: var(--accent-fill);
+    font-family: var(--font-sans);
+    font-weight: 600;
+    font-size: 16px;
+    letter-spacing: -0.02em;
+    line-height: 1;
+    flex-shrink: 0;
+}
+.dt-brand-name {
+    font-family: var(--font-sans);
+    font-weight: 600;
+    font-size: 16px;
+    letter-spacing: -0.02em;
+    color: var(--ink);
+    line-height: 1;
+}
+/* The stock Streamlit logo placeholder takes 100x32 of space; hide
+   it so the injected brand has room to breathe. */
+[data-testid="stLogoSpacer"]:not(:has(.dt-brand)) {
+    display: none !important;
+}
+
 /* Section labels in the page-nav: tiny uppercase tracking — the
    "Eyebrow" row from spec §4. Streamlit renders these as <span> nodes
    with class ``st-emotion-cache-…`` inside ``stSidebarNav`` — class
@@ -200,16 +244,25 @@ body, .stApp {
     margin: 0 !important;
 }
 
-/* Nav items: comfortable padding, soft hover. */
+/* Nav items — tight padding so the menu lists feel dense and don't
+   waste vertical space. */
 [data-testid="stSidebarNav"] a[data-testid="stSidebarNavLink"],
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"] a {
     color: var(--ink-secondary) !important;
     font-size: 13.5px !important;
-    line-height: 1.3 !important;
-    padding: 7px 10px !important;
+    line-height: 1.25 !important;
+    padding: 4px 10px !important;
     border-radius: var(--r-sm) !important;
     transition: background 0.12s ease, color 0.12s ease;
 }
+[data-testid="stSidebarNav"] li,
+[data-testid="stSidebarNavItems"] > li {
+    margin-bottom: 1px !important;
+}
+[data-testid="stSidebarNavSectionHeader"] {
+    padding-top: 10px !important;
+    padding-bottom: 2px !important;
+}
 [data-testid="stSidebarNav"] a[data-testid="stSidebarNavLink"]:hover,
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"] a:hover {
     background: rgba(0,0,0,0.04) !important;
@@ -393,6 +446,12 @@ div[data-testid="stContainer"][data-border="true"] {
     border-radius: var(--r-lg) !important;
     box-shadow: 0 1px 2px rgba(28,25,23,0.03);
 }
+/* Tighten the inter-row gap inside bordered containers — applies to
+   the Files card rows after import and the findings-card rows alike,
+   so the dense card body has less wasted vertical whitespace. */
+[data-testid="stVerticalBlockBorderWrapper"] [data-testid="stVerticalBlock"] {
+    gap: 0.25rem !important;
+}
 
 /* ---------- Alerts — soft fills, no harsh borders ---------- */
 [data-testid="stAlert"] [data-testid="stAlertContainer"],
@@ -438,6 +497,39 @@ div[data-testid="stContainer"][data-border="true"] {
     font-family: var(--font-sans) !important;
 }
 
+/* Sidebar widget labels — render as the "Eyebrow" row from spec §4
+   (tiny uppercase tracking, tertiary ink) so the ``Language`` /
+   ``Core · 1820 days left`` blocks at the bottom of the sidebar
+   match the section-title rhythm of the nav above. */
+[data-testid="stSidebar"] [data-testid="stWidgetLabel"] p,
+[data-testid="stSidebar"] label[data-testid="stWidgetLabel"] {
+    font-size: 11.5px !important;
+    font-weight: 500 !important;
+    text-transform: uppercase !important;
+    letter-spacing: 0.08em !important;
+    color: var(--ink-tertiary) !important;
+    margin-bottom: 4px !important;
+}
+/* Sidebar selectbox — quiet outline, cream surface that reads as
+   part of the sidebar rather than a Streamlit-default white island. */
+[data-testid="stSidebar"] [data-testid="stSelectbox"] div[role="combobox"],
+[data-testid="stSidebar"] [data-baseweb="select"] > div {
+    background: var(--surface) !important;
+    border: 1px solid var(--border) !important;
+    border-radius: var(--r-sm) !important;
+    font-size: 13px !important;
+    min-height: 32px !important;
+}
+[data-testid="stSidebar"] [data-testid="stSelectbox"] div[role="combobox"]:hover,
+[data-testid="stSidebar"] [data-baseweb="select"] > div:hover {
+    border-color: var(--border-strong) !important;
+}
+/* Streamlit pads the selectbox internals; tighten the chevron column
+   so the control isn't taller than the nav items above it. */
+[data-testid="stSidebar"] [data-baseweb="select"] > div > div {
+    padding: 4px 8px !important;
+}
+
 /* Divider — softer warm gray instead of cool Streamlit default. */
 [data-testid="stMarkdownContainer"] hr,
 .stApp hr {
@@ -605,15 +697,57 @@ div[data-testid="stContainer"][data-border="true"] {
     display: flex;
     align-items: center;
     gap: 12px;
-    padding: 14px 18px;
+    /* Generous left/right padding so the filename + counts have visible
+       breathing room against the card's rounded edges — the head bleeds
+       out to those edges via the negative margin below, so without the
+       extra padding the content sits flush against the border. */
+    padding: 16px 22px;
     border-bottom: 1px solid var(--border);
     background: var(--surface-hover);
     /* -1rem on top/sides bleeds the head to the card edges (the parent
-       ``st.container(border=True)`` has 1rem padding). +0.75rem on the
-       bottom is the breathing room before the first finding row —
-       without it the row sits flush against the head's bottom border. */
-    margin: -1rem -1rem 0.75rem;
+       ``st.container(border=True)`` has 1rem padding). +1.5rem on the
+       bottom is breathing room before the first finding row — without
+       it the row sits flush against the head's bottom border. */
+    margin: -1rem -1rem 1.5rem;
     border-radius: var(--r-lg) var(--r-lg) 0 0;
+    cursor: pointer;
+    user-select: none;
+    transition: background 0.12s ease;
+}
+.dt-finding-group-head:hover {
+    background: var(--accent-fill);
+}
+/* Chevron lives on the right of the head, rotates to indicate state. */
+.dt-finding-group-chevron {
+    margin-left: 8px;
+    color: var(--ink-tertiary);
+    font-family: "Material Symbols Outlined" !important;
+    font-size: 20px !important;
+    font-feature-settings: normal !important;
+    line-height: 1 !important;
+    transition: transform 0.15s ease;
+    flex-shrink: 0;
+}
+.dt-finding-group-head[data-dt-collapsed="false"] .dt-finding-group-chevron {
+    transform: rotate(90deg);
+}
+/* Collapsed = body rows hidden + head tucks tight against card bottom.
+   The head's siblings inside the bordered container are the
+   ``stHorizontalBlock``s emitted by each ``st.columns`` row — when the
+   head carries ``data-dt-collapsed="true"`` they collapse to nothing
+   and the head's bottom border becomes the card's bottom edge. */
+.dt-finding-group-head[data-dt-collapsed="true"] {
+    margin: -1rem -1rem -1rem;
+    border-bottom: none;
+    border-radius: var(--r-lg);
+}
+/* Hide every sibling that comes AFTER the head's element-container
+   (the rows are emitted as ``stLayoutWrapper`` or
+   ``stElementContainer`` siblings depending on Streamlit's internal
+   layout reducer; ``~ *`` matches both and survives future renames). */
+[data-testid="stElementContainer"]:has(.dt-finding-group-head[data-dt-collapsed="true"])
+  ~ * {
+    display: none !important;
 }
 .dt-severity-dot {
     width: 8px; height: 8px;
@@ -770,6 +904,85 @@ div[data-testid="stContainer"][data-border="true"] {
 # script walks the dropzone buttons after first paint and rewrites the
 # label to "Import" — and re-runs on Streamlit's component-rerender
 # DOM mutations so the swap survives navigation and reruns.
+# Injects the sidebar brand block (mockup §brand) at the top of
+# Streamlit's ``stSidebarHeader``: the 28px ink-filled rounded square
+# with the "D" wordmark followed by the "DataTools" word. Streamlit's
+# ``stLogoSpacer`` reserves the slot but doesn't render anything
+# without a ``st.logo()`` call; we replace its content rather than
+# call ``st.logo`` because the brand wants both a chip AND wordmark
+# in one block, which ``st.logo`` can't do without shipping a static
+# image asset. MutationObserver re-injects when Streamlit remounts
+# the sidebar header.
+_INJECT_BRAND_JS = """
+<script>
+  (function () {
+    function inject(doc) {
+      var header = doc.querySelector('[data-testid="stSidebarHeader"]');
+      if (!header) return;
+      if (header.querySelector('.dt-brand')) return;
+      var brand = doc.createElement('div');
+      brand.className = 'dt-brand';
+      brand.innerHTML =
+        '<div class="dt-brand-mark">D</div>' +
+        '<div class="dt-brand-name">DataTools</div>';
+      header.insertBefore(brand, header.firstChild);
+    }
+    var doc;
+    try { doc = window.parent.document; }
+    catch (e) { doc = document; }
+    inject(doc);
+    var win = doc.defaultView || window.parent || window;
+    if ('MutationObserver' in win) {
+      var raf = 0;
+      try {
+        new win.MutationObserver(function () {
+          if (raf) return;
+          raf = win.requestAnimationFrame(function () { raf = 0; inject(doc); });
+        }).observe(doc.body, { childList: true, subtree: true });
+      } catch (e) {}
+    }
+  })();
+</script>
+"""
+
+
+# Toggle a ``.dt-finding-group-head``'s ``data-dt-collapsed`` attribute
+# on click. CSS handles the visual collapse (hide siblings, tuck the
+# head against the card bottom) — all this script does is flip the
+# attribute. MutationObserver re-binds when Streamlit remounts heads.
+_WIRE_COLLAPSIBLE_FINDINGS_JS = """
+<script>
+  (function () {
+    function wire(doc) {
+      var heads = doc.querySelectorAll('.dt-finding-group-head');
+      heads.forEach(function (h) {
+        if (h.dataset.dtWired === '1') return;
+        h.dataset.dtWired = '1';
+        h.addEventListener('click', function () {
+          var collapsed = h.getAttribute('data-dt-collapsed') === 'true';
+          h.setAttribute('data-dt-collapsed', collapsed ? 'false' : 'true');
+        });
+      });
+    }
+    var doc;
+    try { doc = window.parent.document; }
+    catch (e) { doc = document; }
+    wire(doc);
+    var win = doc.defaultView || window.parent || window;
+    if ('MutationObserver' in win) {
+      var raf = 0;
+      try {
+        new win.MutationObserver(function () {
+          if (raf) return;
+          raf = win.requestAnimationFrame(function () { raf = 0; wire(doc); });
+        }).observe(doc.body, { childList: true, subtree: true });
+      } catch (e) {}
+    }
+  })();
+</script>
+"""
+
+
 _RENAME_UPLOAD_BUTTON_JS = """
 <script>
   (function () {
@@ -836,10 +1049,16 @@ def hide_streamlit_chrome(*, gate_license: bool = True) -> None:
     from src.gui.theme import apply_theme
     apply_theme()
     st.markdown(_DESIGN_TOKENS_CSS, unsafe_allow_html=True)
-    # ``st.markdown`` doesn't execute embedded scripts; ship the
-    # Upload→Import rewriter through an iframe component the same way
-    # the sticky footer mounts on ``<body>``.
-    st.iframe(_RENAME_UPLOAD_BUTTON_JS, height=1)
+    # ``st.markdown`` doesn't execute embedded scripts; ship every
+    # DOM-mutating script through a single iframe component (same way
+    # the sticky footer mounts on ``<body>``). Bundled together so
+    # there's one component-iframe per page, not three.
+    st.iframe(
+        _INJECT_BRAND_JS
+        + _RENAME_UPLOAD_BUTTON_JS
+        + _WIRE_COLLAPSIBLE_FINDINGS_JS,
+        height=1,
+    )
     # Stamp a session-start record into the audit log the first time
     # any page renders. Idempotent — subsequent calls are no-ops.
     # Wrapped because a broken audit log MUST NOT take the GUI down.
@@ -2599,10 +2818,11 @@ def render_findings_panel(
         )
 
     head_html = (
-        '<div class="dt-finding-group-head">'
+        '<div class="dt-finding-group-head" data-dt-collapsed="true">'
         f'<span class="dt-severity-dot {worst}"></span>'
         f'<span class="dt-group-filename">{_html.escape(header)}</span>'
         f'<div class="dt-group-counts">{pills_html}</div>'
+        '<span class="dt-finding-group-chevron">chevron_right</span>'
         '</div>'
     )
     st.markdown(head_html, unsafe_allow_html=True)
@@ -2664,7 +2884,11 @@ def _render_finding_row_v2(f, *, row_key: str) -> None:
                           f"{'' if len(f.samples) == 1 else 's'} captured")
     meta_html = " · ".join(meta_parts)
 
-    col_icon, col_body, col_action = st.columns([0.4, 8, 1.6])
+    # Action button moved to the LEFT of the description per UX
+    # feedback: ``[icon] [Open <Tool> →] [description]`` — the action
+    # is now the prominent affordance in the row, with the description
+    # taking the wide remaining column.
+    col_icon, col_action, col_body = st.columns([0.4, 1.8, 8])
 
     col_icon.markdown(
         f'<div class="dt-finding-icon {f.severity}">'
@@ -2673,22 +2897,22 @@ def _render_finding_row_v2(f, *, row_key: str) -> None:
         unsafe_allow_html=True,
     )
 
-    body_html = f'<p class="dt-finding-title">{title_html}</p>'
-    if meta_html:
-        body_html += f'<p class="dt-finding-meta">{meta_html}</p>'
-    col_body.markdown(body_html, unsafe_allow_html=True)
-
     page_slug = _tool_page_slug(f.tool) if getattr(f, "tool", "") else ""
     if page_slug:
         tool_label = tool_display_name(f.tool)
         if col_action.button(
-            f"Open {tool_label} →",
+            f"{tool_label} →",
             key=f"_finding_open_{row_key}",
             type="tertiary",
             width="stretch",
         ):
             st.switch_page(page_slug)
 
+    body_html = f'<p class="dt-finding-title">{title_html}</p>'
+    if meta_html:
+        body_html += f'<p class="dt-finding-meta">{meta_html}</p>'
+    col_body.markdown(body_html, unsafe_allow_html=True)
+
 
 _PREVIEW_TABLE_CSS = """
 <style>