diff --git a/client/scenes/shell/MainWindowShell.tscn b/client/scenes/shell/MainWindowShell.tscn
new file mode 100644
index 0000000..5ff2349
--- /dev/null
+++ b/client/scenes/shell/MainWindowShell.tscn
@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://scripts/ui/shell/main_window_shell.gd" id="1"]
+
+[node name="MainWindowShell" type="Control"]
+script = ExtResource("1")
diff --git a/client/scripts/ui/shell/main_window_shell.gd b/client/scripts/ui/shell/main_window_shell.gd
new file mode 100644
index 0000000..ebacf2c
--- /dev/null
+++ b/client/scripts/ui/shell/main_window_shell.gd
@@ -0,0 +1,212 @@
+class_name MainWindowShell
+extends Control
+## The exploration HUD — the frame every screen lives in (mock 2a). Two-panel
+## tabletop split: a dark isometric world slot (turn rail, minimap, system dock,
+## command bar) + the permanent DM narration book. §2: the shell owns HUD state
+## (ShellState) and consumes DM text (never owns narrative truth). It reuses the
+## proven Theme (M3-a) and DM loop (M2) — nothing here is reinvented.
+
+const GAME_THEME := "res://assets/theme/game_theme.tres"
+const DARK_BAY := "res://scenes/theme/surfaces/DarkBay.tscn"
+const SYSTEM_DOCK := "res://scenes/shell/SystemDock.tscn"
+const NARRATION_BOOK := "res://scenes/shell/NarrationBook.tscn"
+const WORLD_WIDTH := 1180.0
+const BOOK_WIDTH := 740.0
+
+# HttpTransport carries no class_name (unlike DmService/FallbackLibrary) — every
+# other call site (narrate_harness.gd, test_net_primitives.gd) reaches it via
+# preload, so this mirrors the existing pattern rather than inventing a new one.
+const HttpTransport = preload("res://scripts/net/http_transport.gd")
+
+var service: DmService = null  # injection seam; real HttpTransport built if null
+
+var book: NarrationBook
+var dock: SystemDock
+var _state: ShellState
+var _log: CanonLog
+var _http: HTTPRequest
+
+
+func _ready() -> void:
+	theme = load(GAME_THEME)
+	# Root Control is not sized by full-rect anchors under F6 — size explicitly,
+	# and no anchors_preset on the .tscn root (M3-a collapse bug).
+	_fit_to_viewport()
+	get_viewport().size_changed.connect(_fit_to_viewport)
+
+	_state = ShellState.seed()
+	_log = _build_seed_log()
+	_build_layout()
+
+	if service == null:
+		_http = HTTPRequest.new()
+		add_child(_http)
+		service = DmService.new(HttpTransport.new(_http), FallbackLibrary.new())
+
+	book.setup(service, _log, _state)
+	dock.setup(_state)
+	dock.screen_requested.connect(_on_screen_requested)
+	book.narrate()  # initial narration; async, fire-and-forget
+
+
+func _fit_to_viewport() -> void:
+	size = get_viewport_rect().size
+
+
+func _build_layout() -> void:
+	var split := HBoxContainer.new()
+	split.set_anchors_preset(Control.PRESET_FULL_RECT)
+	split.add_theme_constant_override("separation", 0)
+	add_child(split)
+
+	var world := _build_world()
+	world.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	split.add_child(world)
+
+	book = load(NARRATION_BOOK).instantiate()
+	book.custom_minimum_size = Vector2(BOOK_WIDTH, 0)
+	var book_panel := PanelContainer.new()
+	book_panel.theme_type_variation = ThemeKeys.PARCHMENT_CARD
+	book_panel.custom_minimum_size = Vector2(BOOK_WIDTH, 0)
+	book_panel.add_child(book)
+	split.add_child(book_panel)
+
+
+func _build_world() -> Control:
+	var world := Control.new()
+	world.custom_minimum_size = Vector2(WORLD_WIDTH, 0)
+	world.clip_contents = true
+
+	var bay = load(DARK_BAY).instantiate()
+	bay.set_anchors_preset(Control.PRESET_FULL_RECT)
+	world.add_child(bay)
+
+	var caption := Label.new()
+	caption.theme_type_variation = ThemeKeys.MONO
+	caption.text = "ISOMETRIC WORLD VIEW"
+	caption.set_anchors_preset(Control.PRESET_CENTER)
+	world.add_child(caption)
+
+	var rail := _build_turn_rail()
+	rail.position = Vector2(28, 28)
+	world.add_child(rail)
+
+	var minimap := PanelContainer.new()
+	minimap.theme_type_variation = ThemeKeys.DARK_PANEL
+	minimap.custom_minimum_size = Vector2(200, 200)
+	minimap.set_anchors_preset(Control.PRESET_TOP_RIGHT)
+	minimap.position = Vector2(-228, 28)
+	var minimap_label := Label.new()
+	minimap_label.theme_type_variation = ThemeKeys.MONO
+	minimap_label.text = "MINIMAP"
+	minimap.add_child(minimap_label)
+	world.add_child(minimap)
+
+	dock = load(SYSTEM_DOCK).instantiate()
+	dock.set_anchors_preset(Control.PRESET_CENTER_RIGHT)
+	dock.position = Vector2(-260, 0)
+	world.add_child(dock)
+
+	var command_bar := _build_command_bar()
+	command_bar.set_anchors_preset(Control.PRESET_BOTTOM_WIDE)
+	command_bar.position = Vector2(0, -150)
+	world.add_child(command_bar)
+
+	return world
+
+
+func _build_turn_rail() -> Control:
+	var panel := PanelContainer.new()
+	panel.theme_type_variation = ThemeKeys.DARK_PANEL
+	var col := VBoxContainer.new()
+	col.add_theme_constant_override("separation", 8)
+	panel.add_child(col)
+	var title := Label.new()
+	title.theme_type_variation = ThemeKeys.MONO
+	title.text = "TURN ORDER"
+	col.add_child(title)
+	var row := HBoxContainer.new()
+	row.add_theme_constant_override("separation", 12)
+	col.add_child(row)
+	for e in _state.turn_order:
+		var token := Label.new()
+		token.theme_type_variation = ThemeKeys.ACCENT
+		token.text = "✕" if e.is_downed else e.initials
+		token.add_theme_color_override("font_color", _side_color(e))
+		row.add_child(token)
+	return panel
+
+
+func _side_color(e: TurnEntry) -> Color:
+	if e.is_downed:
+		return Palette.BLOOD
+	if e.is_active:
+		return Palette.GOLD
+	match e.side:
+		&"enemy": return Palette.BLOOD_BRIGHT
+		&"ally": return Palette.STEEL
+		_: return Palette.CREAM
+
+
+func _build_command_bar() -> Control:
+	var bar := HBoxContainer.new()
+	bar.add_theme_constant_override("separation", 24)
+	bar.custom_minimum_size = Vector2(0, 150)
+
+	var vitals := VBoxContainer.new()
+	var hp := Label.new()
+	hp.theme_type_variation = ThemeKeys.MONO
+	hp.text = "HP %d / %d" % [_state.vitals["hp"], _state.vitals["hp_max"]]
+	var mp := Label.new()
+	mp.theme_type_variation = ThemeKeys.MONO
+	mp.text = "MP %d / %d" % [_state.vitals["mp"], _state.vitals["mp_max"]]
+	var gold := Label.new()
+	gold.theme_type_variation = ThemeKeys.MONO
+	gold.add_theme_color_override("font_color", Palette.GOLD_BRIGHT)
+	gold.text = "◈ %d gp" % _state.vitals["gold"]
+	for l in [hp, mp, gold]:
+		vitals.add_child(l)
+	bar.add_child(vitals)
+
+	var slots := HBoxContainer.new()
+	slots.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	slots.add_theme_constant_override("separation", 9)
+	for c in _state.consumables:
+		var slot := PanelContainer.new()
+		slot.theme_type_variation = ThemeKeys.ITEM_TILE if c["label"] != "" else ThemeKeys.ITEM_TILE_EMPTY
+		slot.custom_minimum_size = Vector2(62, 62)
+		var name_label := Label.new()
+		name_label.theme_type_variation = ThemeKeys.MONO
+		name_label.text = c["label"]
+		slot.add_child(name_label)
+		slots.add_child(slot)
+	bar.add_child(slots)
+
+	var end_turn := Button.new()
+	end_turn.theme_type_variation = ThemeKeys.PRIMARY_CTA
+	end_turn.text = "END TURN"
+	bar.add_child(end_turn)
+
+	return bar
+
+
+func _on_screen_requested(_id: StringName) -> void:
+	pass  # routing seam — the dock's screens land in later milestones (§17)
+
+
+func _build_seed_log() -> CanonLog:
+	# Code owns the canon log (§11). Hand-built until character creation (M4) and
+	# save/load (M9) construct the real one — mirrors narrate_harness. No Luck
+	# number is rendered anywhere (§7); the descriptor is prose-only.
+	var log := CanonLog.new()
+	log.player = LogPlayer.new("Vexcca", "sellsword", "Fortune spits on you")
+	log.set_location("lower_ward", "the Lower Ward")
+	log.party.append(PartyMember.new("brannoc_thane", "Brannoc Thane", 40))
+	log.party.append(PartyMember.new("cadwyn_vell", "Cadwyn Vell", 15))
+	log.push_event("Followed the beastfolk fence into the Lower Ward after dark")
+	log.push_event("The sewer bite on Vexcca's left arm has begun to turn")
+	log.add_fact("the fence deals out of the Lower Ward")
+	log.add_fact("Vexcca carries an infected bite on the left arm")
+	log.active_quests.append(Quest.new("the_fences_price", "The Fence's Price", "active", "Settle with the beastfolk fence"))
+	log.add_humiliation("h_0001", "haggled badly and got a wrist crushed for it", 6, 4)
+	return log
diff --git a/client/scripts/ui/shell/main_window_shell.gd.uid b/client/scripts/ui/shell/main_window_shell.gd.uid
new file mode 100644
index 0000000..32a41b2
--- /dev/null
+++ b/client/scripts/ui/shell/main_window_shell.gd.uid
@@ -0,0 +1 @@
+uid://bobihkpvsax2u
diff --git a/client/tests/unit/test_main_window_shell.gd b/client/tests/unit/test_main_window_shell.gd
new file mode 100644
index 0000000..44413ab
--- /dev/null
+++ b/client/tests/unit/test_main_window_shell.gd
@@ -0,0 +1,37 @@
+extends "res://addons/gut/test.gd"
+
+const SCENE := "res://scenes/shell/MainWindowShell.tscn"
+const FakeTransport = preload("res://tests/doubles/fake_transport.gd")
+const DmResponse = preload("res://scripts/net/dm_response.gd")
+
+
+func _shell() -> MainWindowShell:
+	# Inject a fake service BEFORE _ready (add_child) so the initial narrate does
+	# not touch the network — instantiate() does not run _ready(); add_child does.
+	var node = load(SCENE).instantiate()
+	var transport = FakeTransport.new()
+	transport.set_response(DmResponse.ok(200, {"prose": "Rain on the cobbles."}))
+	node.service = DmService.new(transport, FallbackLibrary.new())
+	add_child_autofree(node)
+	return node
+
+
+func test_shell_applies_theme_and_fits_viewport():
+	var packed = load(SCENE)
+	assert_true(packed is PackedScene)
+	var node := _shell()
+	assert_true(node is Control)
+	assert_true(node.theme is Theme, "shell applies game_theme")
+	assert_gt(node.size.x, 0.0, "viewport-fit sized the root (M3-a collapse guard)")
+
+
+func test_shell_mounts_both_panels():
+	var node := _shell()
+	assert_not_null(node.book, "narration book mounted")
+	assert_not_null(node.dock, "system dock mounted")
+
+
+func test_shell_builds_a_code_owned_seed_log():
+	var node := _shell()
+	assert_not_null(node._log, "a canon log exists to post (§11)")
+	assert_gt(node._log.established_facts.size(), 0, "seed scene facts are code-owned")
diff --git a/client/tests/unit/test_main_window_shell.gd.uid b/client/tests/unit/test_main_window_shell.gd.uid
new file mode 100644
index 0000000..9547284
--- /dev/null
+++ b/client/tests/unit/test_main_window_shell.gd.uid
@@ -0,0 +1 @@
+uid://dbd4cq1awo4su