diff --git a/static/panels.js b/static/panels.js
index 6e16b417..cb42c709 100644
--- a/static/panels.js
+++ b/static/panels.js
@@ -4614,7 +4614,14 @@ function _setMemoryHeaderButtons(mode) {
   const cancelBtn = $('btnCancelMemoryDetail');
   const saveBtn = $('btnSaveMemoryDetail');
   const meta = _memorySectionMeta(_currentMemorySection);
-  if (mode === 'read' && _currentMemorySection !== 'external_notes' && !meta.readOnly) { if (header) header.style.display = 'flex'; show(editBtn); hide(cancelBtn); hide(saveBtn); }
+  if (mode === 'read') {
+    // Any read view has a populated title → header must be visible. Only the
+    // Edit affordance is gated on the section being editable (read-only
+    // sections like Project Context / External Notes still show the header).
+    if (header) header.style.display = 'flex';
+    if (_currentMemorySection !== 'external_notes' && !meta.readOnly) show(editBtn); else hide(editBtn);
+    hide(cancelBtn); hide(saveBtn);
+  }
   else if (mode === 'edit') { if (header) header.style.display = 'flex'; hide(editBtn); show(cancelBtn); show(saveBtn); }
   else { if (header) header.style.display = 'none'; hide(editBtn); hide(cancelBtn); hide(saveBtn); }
 }
@@ -5788,7 +5795,7 @@ function _renderProfileConceptHelp(activeName){
   if (empty) empty.style.display = 'none';
   _profileMode = 'read';
   _currentProfileDetail = null;
-  _setProfileHeaderButtons('empty');
+  _setProfileHeaderButtons('help');
 }
 
 function _renderProfileDetail(p, activeName){
@@ -5848,6 +5855,11 @@ function _setProfileHeaderButtons(mode, p, activeName){
   } else if (mode === 'create') {
     if (header) header.style.display = 'flex';
     hide(actBtn); hide(delBtn); show(cancelBtn); show(saveBtn);
+  } else if (mode === 'help') {
+    // Read-only help/concept view: title is populated, so show the header but
+    // hide every action button (no profile to act on).
+    if (header) header.style.display = 'flex';
+    [actBtn, delBtn, cancelBtn, saveBtn].forEach(hide);
   } else {
     if (header) header.style.display = 'none';
     [actBtn, delBtn, cancelBtn, saveBtn].forEach(hide);
diff --git a/tests/test_issue4891_detail_header_visibility.py b/tests/test_issue4891_detail_header_visibility.py
new file mode 100644
index 00000000..7b65fcfa
--- /dev/null
+++ b/tests/test_issue4891_detail_header_visibility.py
@@ -0,0 +1,92 @@
+"""Regression guard for #4891: detail-panel headers must stay visible in read
+modes that have a populated title.
+
+#4891 fixed task-detail action buttons being invisible on mobile PWA (the
+`:has(.main-view-title:empty)` pseudo-class didn't re-evaluate after dynamic
+textContent on some WebViews) by explicitly toggling `header.style.display` in
+the per-panel header-button setters. The first cut of that fix introduced two
+SILENT regressions (caught by the gate): read-only Memory sections (Project
+Context / External Notes) and the Profiles "Profiles vs workspaces" help view
+both have a populated title but fell into an `else`/`empty` branch that set the
+header to `display:none`, hiding their header+title.
+
+This guards the invariant: any setter branch that corresponds to a populated
+read/help view must show the header (flex), never hide it.
+"""
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+PANELS = (Path(__file__).resolve().parent.parent / "static" / "panels.js").read_text(encoding="utf-8")
+
+
+def _fn_body(name: str) -> str:
+    i = PANELS.find(f"function {name}(")
+    assert i != -1, f"{name} not found in panels.js"
+    # crude brace matcher from the first '{' after the signature
+    start = PANELS.index("{", i)
+    depth = 0
+    for j in range(start, len(PANELS)):
+        if PANELS[j] == "{":
+            depth += 1
+        elif PANELS[j] == "}":
+            depth -= 1
+            if depth == 0:
+                return PANELS[start : j + 1]
+    raise AssertionError(f"unbalanced braces in {name}")
+
+
+def test_memory_read_mode_shows_header_even_for_readonly_sections():
+    """_setMemoryHeaderButtons('read') must show the header for ALL read views
+    (incl. read-only Project Context / External Notes), only gating the Edit
+    button on editability — not hide the whole header (#4891)."""
+    body = _fn_body("_setMemoryHeaderButtons")
+    # The 'read' branch must set the header to flex unconditionally (the title
+    # is populated in every read view).
+    m = re.search(r"if\s*\(\s*mode\s*===\s*'read'\s*\)\s*\{", body)
+    assert m, "_setMemoryHeaderButtons must have a dedicated mode==='read' branch"
+    read_branch = body[m.end(): m.end() + 400]
+    assert "header.style.display = 'flex'" in read_branch, (
+        "memory 'read' branch must show the header (flex) so read-only sections "
+        "keep their header/title (#4891 regression)"
+    )
+    # The read-only gating must apply to the Edit button, not the whole header.
+    assert "external_notes" in read_branch and "readOnly" in read_branch, (
+        "memory 'read' branch must gate only the Edit button on read-only/"
+        "external_notes, not the header visibility (#4891)"
+    )
+
+
+def test_profile_help_view_keeps_header_visible():
+    """The 'Profiles vs workspaces' help view sets a title, so it must use a
+    header mode that shows the header — not the 'empty' mode that hides it."""
+    help_body = _fn_body("_renderProfileConceptHelp")
+    assert "_setProfileHeaderButtons('empty')" not in help_body, (
+        "profile help view must NOT call _setProfileHeaderButtons('empty') — "
+        "that hides the populated help title (#4891 regression)"
+    )
+    assert "_setProfileHeaderButtons('help')" in help_body, (
+        "profile help view must use the 'help' header mode (shows header, hides "
+        "action buttons) (#4891)"
+    )
+    setter = _fn_body("_setProfileHeaderButtons")
+    m = re.search(r"mode\s*===\s*'help'\s*\)\s*\{", setter)
+    assert m, "_setProfileHeaderButtons must handle a 'help' mode"
+    help_branch = setter[m.end(): m.end() + 240]
+    assert "header.style.display = 'flex'" in help_branch, (
+        "'help' header mode must show the header (flex) (#4891)"
+    )
+
+
+def test_task_detail_header_shown_in_read_and_edit():
+    """The original #4891 fix: task-detail header is explicitly shown in read/
+    create/edit and hidden only in the closed/empty state."""
+    body = _fn_body("_setCronHeaderButtons")
+    assert body.count("header.style.display = 'flex'") >= 2, (
+        "_setCronHeaderButtons must explicitly show the header in read and "
+        "create/edit modes (#4891)"
+    )
+    assert "header.style.display = 'none'" in body, (
+        "_setCronHeaderButtons must hide the header in the closed/empty state (#4891)"
+    )