diff --git a/client/README.md b/client/README.md
index 03bad5d..ba64eb3 100644
--- a/client/README.md
+++ b/client/README.md
@@ -143,6 +143,7 @@ Full checklist: [`docs/manual-qa/NEO-31.md`](../docs/manual-qa/NEO-31.md) · cas
   - **`UICanvas/CastFeedbackLabel`** — on accept: **`Cast: {damage} dmg → {remaining} HP`** or **`… — defeated!`** when **`targetDefeated`**; denies unchanged from NEO-28.
   - **`UICanvas/CombatTargetHpLabel`** — locked target **`currentHp/maxHp`** (+ **` (defeated)`**); **`Target HP: — (no lock)`** when unlocked.
 - **Refresh (event-driven):** combat-target GET after successful cast accept and when **`lockedTargetId`** changes (Tab lock / Esc clear / server correction). No periodic HP poll.
+- **Dev hotbar bootstrap (NEO-85):** on first hotbar sync, if slot **0** is empty the client POSTs a bind for **`prototype_pulse`** once (same preset as Bruno `Post hotbar bind slot0 pulse`) so digit **1** works without a manual bind step when the server is up.
 - **Dev fixture reset:** when the server exposes **`POST /game/__dev/combat-targets-fixture`** (Development/Testing), reset dummy HP between manual QA runs — see [server README](../server/README.md#combat-entity-health-store-neo-80).
 
 Full checklist: [`docs/manual-qa/NEO-85.md`](../docs/manual-qa/NEO-85.md).
diff --git a/client/scripts/main.gd b/client/scripts/main.gd
index 2b1994f..10bb98e 100644
--- a/client/scripts/main.gd
+++ b/client/scripts/main.gd
@@ -43,6 +43,7 @@ const PrototypeInteractablePicker := preload("res://scripts/prototype_interactab
 const HotbarCastSlotResolver := preload("res://scripts/hotbar_cast_slot_resolver.gd")
 const CooldownStateScript := preload("res://scripts/cooldown_state.gd")
 const COOLDOWN_REASON_ON_CD := "on_cooldown"
+const DEV_BOOTSTRAP_CAST_ABILITY_ID := "prototype_pulse"
 const SCRAP_METAL_BULK_ID := "scrap_metal_bulk"
 const SALVAGE_SKILL_ID := "salvage"
 const REFINE_SKILL_ID := "refine"
@@ -90,6 +91,7 @@ var _gather_pending_interactable_id: String = ""
 var _gather_awaiting_inventory_finalize: bool = false
 var _cached_recipe_rows: Array = []
 var _recipe_defs_error: String = ""
+var _dev_pulse_bootstrap_attempted: bool = false
 
 @onready var _camera: Camera3D = $World/IsometricFollowCamera/Camera3D
 @onready var _world: Node3D = $World
@@ -341,7 +343,7 @@ func _setup_cooldown_sync() -> void:
 		)
 	if _hotbar_client.has_signal("loadout_changed"):
 		_hotbar_client.connect(
-			"loadout_changed", Callable(self, "_on_hotbar_loadout_changed_sync_cooldown")
+			"loadout_changed", Callable(self, "_on_hotbar_loadout_changed")
 		)
 	_ensure_cooldown_poll_timer()
 
@@ -749,6 +751,27 @@ func _finalize_pending_gather_feedback() -> void:
 	_render_gather_feedback_label("Gather: +%d %s" % [delta, label])
 
 
+func _on_hotbar_loadout_changed(loadout: Dictionary) -> void:
+	_on_hotbar_loadout_changed_sync_cooldown(loadout)
+	_maybe_dev_bind_pulse_slot0()
+
+
+func _maybe_dev_bind_pulse_slot0() -> void:
+	if _dev_pulse_bootstrap_attempted:
+		return
+	if not is_instance_valid(_hotbar_state) or not is_instance_valid(_hotbar_client):
+		return
+	var slots: Array = _hotbar_state.call("slots_snapshot") as Array
+	if slots.is_empty():
+		return
+	var slot0: Variant = slots[0]
+	if slot0 is String and not (slot0 as String).strip_edges().is_empty():
+		return
+	_dev_pulse_bootstrap_attempted = true
+	if _hotbar_client.has_method("request_bind_slot"):
+		_hotbar_client.call("request_bind_slot", 0, DEV_BOOTSTRAP_CAST_ABILITY_ID)
+
+
 func _on_hotbar_loadout_changed_sync_cooldown(_loadout: Dictionary) -> void:
 	if (
 		is_instance_valid(_cooldown_client)
@@ -983,6 +1006,9 @@ func _try_inventory_refresh_input(event: InputEvent) -> bool:
 
 func _request_hotbar_cast_slot(slot_index: int) -> void:
 	if not is_instance_valid(_hotbar_state) or not _hotbar_state.has_method("slots_snapshot"):
+		if is_instance_valid(_cast_feedback_label):
+			_cast_feedback_label.text = "Hotbar: not ready"
+		push_warning("Hotbar cast ignored: hotbar_state unavailable")
 		return
 	var slots: Array = _hotbar_state.call("slots_snapshot") as Array
 	var target_state: Dictionary = {}
@@ -995,8 +1021,15 @@ func _request_hotbar_cast_slot(slot_index: int) -> void:
 		var reason: String = str(outcome.get(HotbarCastSlotResolver.KEY_REASON, ""))
 		if reason == HotbarCastSlotResolver.REASON_INVALID_SLOT:
 			push_warning("Hotbar cast ignored: slot %d invalid_slot_index" % slot_index)
+			if is_instance_valid(_cast_feedback_label):
+				_cast_feedback_label.text = "Hotbar: slot %d invalid" % (slot_index + 1)
 		elif reason == HotbarCastSlotResolver.REASON_EMPTY_SLOT:
 			push_warning("Hotbar cast ignored: slot %d empty_slot" % slot_index)
+			if is_instance_valid(_cast_feedback_label):
+				_cast_feedback_label.text = (
+					"Hotbar: slot %d empty (bind ability or wait for sync)"
+					% (slot_index + 1)
+				)
 		return
 	var ability_id: String = outcome[HotbarCastSlotResolver.KEY_ABILITY_ID] as String
 	var resolved_slot: int = int(outcome.get(HotbarCastSlotResolver.KEY_SLOT_INDEX, slot_index))
@@ -1024,6 +1057,8 @@ func _request_hotbar_cast_slot(slot_index: int) -> void:
 				% [resolved_slot, ability_id, target_label]
 			)
 		)
+	elif is_instance_valid(_cast_feedback_label):
+		_cast_feedback_label.text = "Cast: failed to send (busy or server offline?)"
 
 
 func _forward_interact_post(method: String) -> void:
diff --git a/client/test/hotbar_dev_bootstrap_test.gd b/client/test/hotbar_dev_bootstrap_test.gd
new file mode 100644
index 0000000..7cf1618
--- /dev/null
+++ b/client/test/hotbar_dev_bootstrap_test.gd
@@ -0,0 +1,76 @@
+extends GdUnitTestSuite
+
+## NEO-85: dev hotbar bootstrap binds prototype_pulse to slot 0 when empty.
+
+const HotbarState := preload("res://scripts/hotbar_state.gd")
+const DEV_BOOTSTRAP_CAST_ABILITY_ID := "prototype_pulse"
+
+
+class SpyHotbarClient:
+	extends Node
+	var bind_calls: Array = []
+
+	func request_bind_slot(slot_index: int, ability_id: String) -> void:
+		bind_calls.append([slot_index, ability_id])
+
+
+class BootstrapHarness:
+	extends Node
+	var bootstrap_attempted: bool = false
+	var _hotbar_state: Node
+	var _hotbar_client: SpyHotbarClient
+
+	func setup(parent: Node, slot0_ability: Variant) -> void:
+		_hotbar_state = HotbarState.new()
+		_hotbar_client = SpyHotbarClient.new()
+		parent.add_child(_hotbar_state)
+		parent.add_child(_hotbar_client)
+		var rows: Array = []
+		for i in range(8):
+			var row: Dictionary = {"slotIndex": i}
+			if i == 0 and slot0_ability is String:
+				row["abilityId"] = slot0_ability
+			rows.append(row)
+		_hotbar_state.call("apply_slots", rows)
+
+	func maybe_dev_bind_pulse_slot0() -> void:
+		if bootstrap_attempted:
+			return
+		if not is_instance_valid(_hotbar_state) or not is_instance_valid(_hotbar_client):
+			return
+		var slots: Array = _hotbar_state.call("slots_snapshot") as Array
+		if slots.is_empty():
+			return
+		var slot0: Variant = slots[0]
+		if slot0 is String and not (slot0 as String).strip_edges().is_empty():
+			return
+		bootstrap_attempted = true
+		_hotbar_client.request_bind_slot(0, DEV_BOOTSTRAP_CAST_ABILITY_ID)
+
+
+func test_empty_slot0_triggers_pulse_bind_once() -> void:
+	# Arrange
+	var harness := BootstrapHarness.new()
+	auto_free(harness)
+	add_child(harness)
+	harness.setup(self, null)
+	# Act
+	harness.maybe_dev_bind_pulse_slot0()
+	harness.maybe_dev_bind_pulse_slot0()
+	# Assert
+	assert_that(harness._hotbar_client.bind_calls.size()).is_equal(1)
+	assert_that(int(harness._hotbar_client.bind_calls[0][0])).is_equal(0)
+	assert_that(str(harness._hotbar_client.bind_calls[0][1])).is_equal(DEV_BOOTSTRAP_CAST_ABILITY_ID)
+
+
+func test_slot0_already_bound_skips_bootstrap() -> void:
+	# Arrange
+	var harness := BootstrapHarness.new()
+	auto_free(harness)
+	add_child(harness)
+	harness.setup(self, "prototype_pulse")
+	# Act
+	harness.maybe_dev_bind_pulse_slot0()
+	# Assert
+	assert_that(harness._hotbar_client.bind_calls.size()).is_equal(0)
+	assert_that(harness.bootstrap_attempted).is_false()
diff --git a/docs/manual-qa/NEO-85.md b/docs/manual-qa/NEO-85.md
index d4c5e07..9d3ae44 100644
--- a/docs/manual-qa/NEO-85.md
+++ b/docs/manual-qa/NEO-85.md
@@ -15,7 +15,7 @@
 
 ## 2) Client — combat HUD
 
-- [ ] Open Godot main scene with server running; ensure hotbar slot **0** is bound to **`prototype_pulse`** (NEO-29 hydrate or bind via Bruno/API if needed).
+- [ ] Open Godot main scene with server running; after hotbar sync, slot **0** auto-binds to **`prototype_pulse`** when empty (NEO-85 dev bootstrap — same as Bruno `Post hotbar bind slot0 pulse`).
 - [ ] **Tab** to lock **`prototype_target_alpha`**; **`CombatTargetHpLabel`** shows **`Target HP: prototype_target_alpha 100/100`** (or **`…`** briefly until GET completes).
 - [ ] Press **1** (hotbar slot 1 → index 0): **`CastFeedbackLabel`** shows **`Cast: 25 dmg → 75 HP`** (not Output-only).
 - [ ] **`CombatTargetHpLabel`** updates to **`75/100`** after the cast (event-driven GET refresh).