feat(ui): add in-game debug console with tilde toggle and command dispatch (#581)

- debug_console.gd: new ModalLayer Control — tilde key toggles bottom-40% panel,
  command history (up/down), SimBridge dispatch for all DebugCommandKind variants:
  ticks, contaminate, tp, activate, triangle, npc, triangles, pop, status, help
- debug_console.tscn: minimal scene node; UI built programmatically in _ready()
- input_mapper.gd: DEBUG_COMMAND action added to Action enum
- sim_bridge.gd: DEBUG_COMMAND → "DebugCommand" wire mapping
- protocol.gd: v18 debug_response decode (command, text, success fields)
- game_state.gd: debug_response field + apply_snapshot one-shot handling
- main.gd: @onready ref, router registration, _consume_debug_response(), settings signal
- settings_dialog.gd: debug_console_toggled signal + CheckButton toggle row (+36px height),
  reads initial state from user://settings.cfg; CheckButton state loaded from PREFS_PATH
- main.tscn: DebugConsole node on ModalLayer, load_steps 27→28

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/scenes/main.tscn

@@ -1,4 +1,4 @@
-[gd_scene load_steps=27 format=3 uid="uid://bswrmh7w8dbgm"]
+[gd_scene load_steps=28 format=3 uid="uid://bswrmh7w8dbgm"]
 
 [ext_resource type="Script" path="res://scripts/main.gd" id="1_main"]
 [ext_resource type="Script" path="res://scripts/rendering/world_renderer.gd" id="2_world"]
@@ -26,6 +26,7 @@
 [ext_resource type="PackedScene" path="res://ui/examine_display.tscn" id="24_examine"]
 [ext_resource type="PackedScene" path="res://ui/journal_panel.tscn" id="25_journal"]
 [ext_resource type="PackedScene" path="res://ui/loading_screen.tscn" id="26_loading"]
+[ext_resource type="PackedScene" uid="uid://b2ndm9rvx8cqp" path="res://ui/debug_console.tscn" id="27_debug_console"]
 
 [node name="Game" type="Node2D"]
 script = ExtResource("1_main")
@@ -194,3 +195,6 @@ layer = 30
 
 ; #257: Loading screen — full-screen overlay during save/load round-trip
 [node name="LoadingScreen" parent="ModalLayer" instance=ExtResource("26_loading")]
+
+; #581: Debug console — tilde key toggles, bottom 40% of screen
+[node name="DebugConsole" parent="ModalLayer" instance=ExtResource("27_debug_console")]

client/scripts/autoloads/game_state.gd

@@ -81,6 +81,11 @@ var rng_seed: Variant = null
 # One-shot: consumed by main.gd after display, then set back to null.
 var save_result: Variant = null
 
+# v18 fields (#580): debug console response from server.
+# {command: String, text: String, success: bool} or null.
+# One-shot: consumed by main.gd and forwarded to DebugConsole, then set to null.
+var debug_response: Variant = null
+
 # #257: Pending load path — set by main menu "Load Game" selection.
 # main.gd sends LOAD_GAME on startup if non-empty, then clears this field.
 # Format: user://saves/<game-id>/<filename>.sav or "" if no pending load.
@@ -311,6 +316,12 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 	else:
 		save_result = null
 
+	# v18: debug_response (#580) — debug console command result.
+	if snapshot.has("debug_response") and snapshot.debug_response is Dictionary:
+		debug_response = snapshot.debug_response
+	else:
+		debug_response = null
+
 	# v14: player_knowledge (#264, D-041) — partial KG dump for journal panel.
 	# Only update when field is present (null means no change, server sends when KG changes).
 	if snapshot.has("player_knowledge") and snapshot.player_knowledge is Dictionary:

client/scripts/autoloads/input_mapper.gd

@@ -24,6 +24,7 @@ enum Action {
 	TELEPORT_HUB,  # #501: Home key — Gauntlet dev teleport (not production fast-travel)
 	SAVE_GAME,  # #554: F5 quicksave — sends SaveGame to server with save path
 	LOAD_GAME,  # #554: F6 quickload — sends LoadGame to server with save path
+	DEBUG_COMMAND,  # #581: debug console command dispatch — sends DebugCommandKind to server
 }
 
 var input_queue: Array[Dictionary] = []

client/scripts/autoloads/sim_bridge.gd

@@ -416,6 +416,8 @@ static func action_enum_to_wire(action: int) -> String:
 			return "SaveGame"  # #554: F5 quicksave (D-085)
 		InputMapper.Action.LOAD_GAME:
 			return "LoadGame"  # #554: F6 quickload (D-085)
+		InputMapper.Action.DEBUG_COMMAND:
+			return "DebugCommand"  # #581: debug console command dispatch
 		_:
 			push_warning("SimBridge: unknown action enum %s" % action)
 			return ""

client/scripts/main.gd

@@ -22,6 +22,7 @@ extends Node2D
 @onready var bug_report_dialog = $ModalLayer/BugReportDialog  # #495: F12 WRONG button
 @onready var settings_dialog = $ModalLayer/SettingsDialog     # #528: audio settings (ESC/OPEN_MENU)
 @onready var loading_screen = $ModalLayer/LoadingScreen       # #257: blocking overlay during load
+@onready var debug_console = $ModalLayer/DebugConsole         # #581: tilde debug console
 
 var _last_dialogue_npc_id: int = -1  # D-064: NPC entity_id for WalkAway input
 var _last_dialogue_npc_name: String = ""  # #535: NPC name for dialogue_response attribution
@@ -122,6 +123,11 @@ func _ready() -> void:
 	_router.register("conversation_ended", _consume_conversation_ended)
 	_router.register("dialogue_response", _consume_dialogue_response)
 	_router.register("save_result", _consume_save_result)
+	_router.register("debug_response", _consume_debug_response)
+
+	# #581: Wire settings_dialog debug console toggle → debug_console.set_enabled
+	if settings_dialog and debug_console:
+		settings_dialog.debug_console_toggled.connect(debug_console.set_enabled)
 
 
 func _process(delta: float) -> void:
@@ -382,6 +388,8 @@ func _consume_dialogue_response() -> void:
 	if GameState.dialogue_response == null or not dialogue_box:
 		return
 	var dr: Dictionary = GameState.dialogue_response
+	# v0.1: falls back to _last_dialogue_npc_id if wire omits speaker_entity_id.
+	# Edge case: fast re-engagement with a different NPC could misattribute — low probability.
 	var speaker_entity_id: int = dr.get("speaker_entity_id", _last_dialogue_npc_id)
 	var speaker_color_index: int = dr.get("speaker_color_index", -1)
 	var speaker_name: String = dr.get("speaker_name", _last_dialogue_npc_name)
@@ -414,6 +422,14 @@ func _consume_save_result() -> void:
 		monologue_display.show_notification(msg)
 
 
+# #581: Forward debug_response from server to the debug console.
+func _consume_debug_response() -> void:
+	if GameState.debug_response == null or not debug_console:
+		return
+	debug_console.append_response(GameState.debug_response)
+	GameState.debug_response = null
+
+
 # D-061: Handle dialogue option selection → send to server
 func _on_dialogue_option_selected(response_id: String, text: String) -> void:
 	SimBridge.send_input({

client/scripts/protocol/protocol.gd

@@ -244,6 +244,17 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 			"error": raw_save.get("error"),
 		}
 
+	# v18: debug_response (#580) — debug console command result.
+	# {command: String, text: String, success: bool}
+	var debug_response: Variant = null
+	var raw_debug: Variant = raw.get("debug_response")
+	if raw_debug is Dictionary:
+		debug_response = {
+			"command": str(raw_debug.get("command", "")),
+			"text": str(raw_debug.get("text", "")),
+			"success": bool(raw_debug.get("success", false)),
+		}
+
 	# TODO(server): Send stationary_ticks in ObserverSnapshot (D-071, D-020).
 	# Server already tracks this in ListeningFocus component (server/src/simulation/listening.rs).
 	# When server populates this field, client-side accumulation fallback in game_state.gd
@@ -320,6 +331,7 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 		"examine_result": examine_result,
 		"player_knowledge": player_knowledge,
 		"save_result": save_result,
+		"debug_response": debug_response,
 		"stationary_ticks": stationary_ticks,
 		"zone_id": zone_id,
 	}

client/ui/debug_console.gd

@@ -0,0 +1,314 @@
+class_name DebugConsole
+extends Control
+
+## In-game debug console (#581). Tilde key (`) toggles open/closed.
+## Semi-transparent panel anchored to bottom ~40% of screen.
+## Dispatches DebugCommandKind variants to server via SimBridge.
+## Settings-toggled; enabled state persisted in user://settings.cfg.
+
+const PREFS_PATH := "user://settings.cfg"
+const PREFS_SECTION := "debug"
+const PREFS_KEY_ENABLED := "console_enabled"
+const MAX_LOG_LINES := 50
+
+const BG_COLOR := Color(0.04, 0.04, 0.06, 0.92)
+const BORDER_COLOR := Color("#4a9ebb")
+const TEXT_COLOR := Color("#c8d0e0")
+const SUCCESS_COLOR := Color("#6bc9a6")
+const ERROR_COLOR := Color("#d45d5d")
+const INPUT_COLOR := Color("#e8c547")
+
+var _enabled: bool = true
+var _open: bool = false
+var _log_lines: Array[String] = []
+var _panel: PanelContainer = null
+var _output_log: RichTextLabel = null
+var _input_line: LineEdit = null
+var _history: Array[String] = []
+var _history_idx: int = -1
+
+
+func _ready() -> void:
+	_load_prefs()
+	visible = false
+	mouse_filter = Control.MOUSE_FILTER_IGNORE
+	set_anchors_preset(Control.PRESET_FULL_RECT)
+	_build_ui()
+	get_viewport().size_changed.connect(_update_panel_layout)
+
+
+func _build_ui() -> void:
+	_panel = PanelContainer.new()
+	_panel.mouse_filter = Control.MOUSE_FILTER_STOP
+	_panel.anchor_left = 0.0
+	_panel.anchor_top = 0.6
+	_panel.anchor_right = 1.0
+	_panel.anchor_bottom = 1.0
+	_panel.offset_left = 0.0
+	_panel.offset_top = 0.0
+	_panel.offset_right = 0.0
+	_panel.offset_bottom = 0.0
+
+	var bg_style := StyleBoxFlat.new()
+	bg_style.bg_color = BG_COLOR
+	bg_style.border_color = BORDER_COLOR
+	bg_style.border_width_top = 1
+	bg_style.content_margin_left = 8.0
+	bg_style.content_margin_right = 8.0
+	bg_style.content_margin_top = 6.0
+	bg_style.content_margin_bottom = 6.0
+	_panel.add_theme_stylebox_override("panel", bg_style)
+	add_child(_panel)
+
+	var vbox := VBoxContainer.new()
+	vbox.add_theme_constant_override("separation", 4)
+	_panel.add_child(vbox)
+
+	_output_log = RichTextLabel.new()
+	_output_log.bbcode_enabled = true
+	_output_log.size_flags_vertical = Control.SIZE_EXPAND_FILL
+	_output_log.scroll_following = true
+	_output_log.selection_enabled = true
+	_output_log.add_theme_color_override("default_color", TEXT_COLOR)
+	_output_log.add_theme_font_size_override("normal_font_size", 13)
+	vbox.add_child(_output_log)
+
+	var sep := HSeparator.new()
+	vbox.add_child(sep)
+
+	_input_line = LineEdit.new()
+	_input_line.placeholder_text = "enter command  (help for list)"
+	_input_line.clear_button_enabled = false
+	_input_line.add_theme_font_size_override("font_size", 13)
+	_input_line.add_theme_color_override("font_color", INPUT_COLOR)
+	_input_line.text_submitted.connect(_on_input_submitted)
+	_input_line.gui_input.connect(_on_input_key)
+	vbox.add_child(_input_line)
+
+
+func _update_panel_layout() -> void:
+	# Anchors handle resize automatically; no manual size calc needed.
+	pass
+
+
+# -- Input handling --
+
+func _unhandled_input(event: InputEvent) -> void:
+	if not _enabled:
+		return
+	if not event is InputEventKey or not event.pressed or event.echo:
+		return
+	if event.keycode == KEY_QUOTELEFT:
+		get_viewport().set_input_as_handled()
+		_toggle()
+		return
+	if _open:
+		# Consume all keyboard events — prevent movement/action leaking through
+		get_viewport().set_input_as_handled()
+		if event.keycode == KEY_ESCAPE:
+			_close()
+
+
+func _on_input_key(event: InputEvent) -> void:
+	if not event is InputEventKey or not event.pressed or event.echo:
+		return
+	if event.keycode == KEY_UP:
+		_history_up()
+		get_viewport().set_input_as_handled()
+	elif event.keycode == KEY_DOWN:
+		_history_down()
+		get_viewport().set_input_as_handled()
+
+
+func _toggle() -> void:
+	if _open:
+		_close()
+	else:
+		_open_console()
+
+
+func _open_console() -> void:
+	_open = true
+	visible = true
+	mouse_filter = Control.MOUSE_FILTER_STOP
+	_input_line.clear()
+	_input_line.grab_focus()
+	_history_idx = -1
+
+
+func _close() -> void:
+	_open = false
+	visible = false
+	mouse_filter = Control.MOUSE_FILTER_IGNORE
+	_input_line.release_focus()
+
+
+func is_open() -> bool:
+	return _open
+
+
+# -- Command input --
+
+func _on_input_submitted(text: String) -> void:
+	var trimmed := text.strip_edges()
+	_input_line.clear()
+	_history_idx = -1
+	if trimmed.is_empty():
+		return
+	if _history.is_empty() or _history[0] != trimmed:
+		_history.push_front(trimmed)
+	if _history.size() > 20:
+		_history.pop_back()
+	_append_text("> " + trimmed, TEXT_COLOR)
+	_dispatch(trimmed)
+
+
+func _dispatch(line: String) -> void:
+	var parts := line.split(" ", false)
+	if parts.is_empty():
+		return
+	var cmd := parts[0].to_lower()
+	match cmd:
+		"help":
+			_print_help()
+		"ticks":
+			if parts.size() < 2 or not parts[1].is_valid_int():
+				_append_text("usage: ticks <n>", ERROR_COLOR)
+				return
+			var n := int(parts[1])
+			if n <= 0:
+				_append_text("ticks: n must be > 0", ERROR_COLOR)
+				return
+			_send_debug({"AdvanceTicks": n})
+		"contaminate":
+			_send_debug("SkipToContamination")
+		"tp":
+			if parts.size() < 2:
+				_append_text("usage: tp <x> <y> [z]  or  tp <location_name>", ERROR_COLOR)
+				return
+			if parts.size() >= 3 and parts[1].is_valid_int() and parts[2].is_valid_int():
+				var z := int(parts[3]) if parts.size() >= 4 and parts[3].is_valid_int() else 0
+				_send_debug({"TeleportToPosition": {"x": int(parts[1]), "y": int(parts[2]), "z": z}})
+			else:
+				var loc := " ".join(PackedStringArray(parts.slice(1)))
+				_send_debug({"TeleportToLocation": loc})
+		"activate":
+			_send_debug("ForceContaminationActivate")
+		"triangle":
+			if parts.size() < 2:
+				_append_text("usage: triangle <id>", ERROR_COLOR)
+				return
+			_send_debug({"ForceTriangleActivation": parts[1]})
+		"npc":
+			if parts.size() < 2 or not parts[1].is_valid_int():
+				_append_text("usage: npc <entity_id>", ERROR_COLOR)
+				return
+			_send_debug({"InspectNpc": int(parts[1])})
+		"triangles":
+			_send_debug("ListTriangles")
+		"pop":
+			_send_debug("ListPopulation")
+		"status":
+			_send_debug("GetContaminationStatus")
+		_:
+			_append_text("unknown command: '%s'  (type 'help')" % cmd, ERROR_COLOR)
+
+
+func _send_debug(kind: Variant) -> void:
+	var err := SimBridge.send_input({
+		"action": InputMapper.Action.DEBUG_COMMAND,
+		"action_data": kind,
+		"timestamp_msec": Time.get_ticks_msec(),
+	})
+	if err != OK:
+		_append_text("send error: %s" % error_string(err), ERROR_COLOR)
+
+
+# -- Response display --
+
+## Append a server debug response to the output log. Auto-opens console if closed.
+func append_response(response: Dictionary) -> void:
+	var success: bool = response.get("success", false)
+	var text: String = response.get("text", "")
+	var color := SUCCESS_COLOR if success else ERROR_COLOR
+	_append_text(text, color)
+	if not _open:
+		_open_console()
+
+
+# -- Log rendering --
+
+func _append_text(text: String, color: Color) -> void:
+	var escaped := text.replace("[", "[lb]").replace("]", "[rb]")
+	_log_lines.append("[color=%s]%s[/color]" % [color.to_html(false), escaped])
+	if _log_lines.size() > MAX_LOG_LINES:
+		_log_lines = _log_lines.slice(_log_lines.size() - MAX_LOG_LINES)
+	if _output_log:
+		_output_log.text = "\n".join(_log_lines)
+
+
+func _print_help() -> void:
+	_append_text(
+		"Commands:\n"
+		+ "  ticks <n>          — fast-forward N ticks\n"
+		+ "  contaminate        — skip to contamination phase\n"
+		+ "  tp <x> <y> [z]    — teleport to tile position\n"
+		+ "  tp <location>      — teleport to named location\n"
+		+ "  activate           — force contamination activate\n"
+		+ "  triangle <id>      — force triangle activation\n"
+		+ "  npc <entity_id>    — inspect NPC state\n"
+		+ "  triangles          — list all triangles\n"
+		+ "  pop                — list active NPCs\n"
+		+ "  status             — contamination status\n"
+		+ "  help               — this list",
+		TEXT_COLOR
+	)
+
+
+# -- Command history --
+
+func _history_up() -> void:
+	if _history.is_empty():
+		return
+	_history_idx = mini(_history_idx + 1, _history.size() - 1)
+	_input_line.text = _history[_history_idx]
+	_input_line.caret_column = _input_line.text.length()
+
+
+func _history_down() -> void:
+	if _history_idx <= 0:
+		_history_idx = -1
+		_input_line.clear()
+		return
+	_history_idx -= 1
+	_input_line.text = _history[_history_idx]
+	_input_line.caret_column = _input_line.text.length()
+
+
+# -- Settings --
+
+func set_enabled(enabled: bool) -> void:
+	_enabled = enabled
+	if not _enabled and _open:
+		_close()
+	_save_prefs()
+
+
+func is_enabled() -> bool:
+	return _enabled
+
+
+func _load_prefs() -> void:
+	var cfg := ConfigFile.new()
+	if cfg.load(PREFS_PATH) != OK:
+		return
+	_enabled = cfg.get_value(PREFS_SECTION, PREFS_KEY_ENABLED, true)
+
+
+func _save_prefs() -> void:
+	var cfg := ConfigFile.new()
+	cfg.load(PREFS_PATH)  # load existing (may have other sections like "audio")
+	cfg.set_value(PREFS_SECTION, PREFS_KEY_ENABLED, _enabled)
+	var err := cfg.save(PREFS_PATH)
+	if err != OK:
+		push_warning("DebugConsole: failed to save prefs (%d)" % err)

client/ui/debug_console.gd.uid

@@ -0,0 +1 @@
+uid://c8pvt3xr7kmd2

client/ui/debug_console.tscn

@@ -0,0 +1,15 @@
+[gd_scene load_steps=2 format=3 uid="uid://b2ndm9rvx8cqp"]
+
+[ext_resource type="Script" uid="uid://c8pvt3xr7kmd2" path="res://ui/debug_console.gd" id="1_debug_console"]
+
+; #581: In-game debug console. Tilde key toggles. ModalLayer.
+; UI built programmatically in _ready() — scene contains only root node + script.
+[node name="DebugConsole" type="Control"]
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+mouse_filter = 1
+script = ExtResource("1_debug_console")

client/ui/settings_dialog.gd

@@ -11,7 +11,7 @@ const TITLE_COLOR := Color("#4a9ebb")
 const FONT_SIZE := 14
 
 const BOX_WIDTH := 460
-const BOX_HEIGHT := 340
+const BOX_HEIGHT := 376  # +36 for Debug Console row
 const PADDING := 20
 const ROW_HEIGHT := 36
 
@@ -28,6 +28,7 @@ var _active: bool = false
 var _container: VBoxContainer = null
 
 signal closed
+signal debug_console_toggled(enabled: bool)  # #581: debug console enabled/disabled
 
 
 func _ready() -> void:
@@ -109,6 +110,29 @@ func _build_ui() -> void:
 			db_label.text = _format_db(value)
 		)
 
+	# #581: Debug Console toggle
+	var debug_hbox := HBoxContainer.new()
+	debug_hbox.custom_minimum_size = Vector2(0, ROW_HEIGHT)
+	_container.add_child(debug_hbox)
+
+	var debug_label := Label.new()
+	debug_label.text = "Debug Console"
+	debug_label.custom_minimum_size = Vector2(150, 0)
+	debug_label.vertical_alignment = VERTICAL_ALIGNMENT_CENTER
+	debug_label.add_theme_font_size_override("font_size", FONT_SIZE)
+	debug_label.add_theme_color_override("font_color", TEXT_COLOR)
+	debug_hbox.add_child(debug_label)
+
+	var debug_check := CheckButton.new()
+	var cfg := ConfigFile.new()
+	debug_check.button_pressed = true  # default: enabled
+	if cfg.load(DebugConsole.PREFS_PATH) == OK:
+		debug_check.button_pressed = cfg.get_value(DebugConsole.PREFS_SECTION, DebugConsole.PREFS_KEY_ENABLED, true)
+	debug_check.toggled.connect(func(enabled: bool) -> void:
+		debug_console_toggled.emit(enabled)
+	)
+	debug_hbox.add_child(debug_check)
+
 	# Spacer
 	var spacer := Control.new()
 	spacer.custom_minimum_size = Vector2(0, 8)