diff --git a/internal/ws/protocol.go b/internal/ws/protocol.go
index dbbef09..12674dc 100644
--- a/internal/ws/protocol.go
+++ b/internal/ws/protocol.go
@@ -8,15 +8,22 @@ import "encoding/json"
 type MsgType string
 
 const (
-	MsgStart MsgType = "start" // Begin recording session
-	MsgStop  MsgType = "stop"  // End recording session
-	MsgPaste MsgType = "paste" // Re-paste a history item
+	MsgHello MsgType = "hello"
+	MsgStart MsgType = "start"
+	MsgStop  MsgType = "stop"
+	MsgPaste MsgType = "paste"
+	MsgPing  MsgType = "ping"
+	MsgPong  MsgType = "pong"
 )
 
 // ClientMsg is a JSON control message from the phone.
 type ClientMsg struct {
-	Type MsgType `json:"type"`
-	Text string  `json:"text,omitempty"` // Only for "paste"
+	Type      MsgType `json:"type"`
+	SessionID string  `json:"sessionId,omitempty"`
+	Seq       int64   `json:"seq,omitempty"`
+	Text      string  `json:"text,omitempty"` // Only for "paste"
+	Version   int     `json:"version,omitempty"`
+	TS        int64   `json:"ts,omitempty"`
 	// Future extension: dynamic hotwords (Phase 2)
 	// Hotwords []string `json:"hotwords,omitempty"`
 }
@@ -24,17 +31,33 @@ type ClientMsg struct {
 // ── Server → Client messages ──
 
 const (
-	MsgPartial MsgType = "partial" // Interim ASR result
-	MsgFinal   MsgType = "final"   // Final ASR result
-	MsgPasted  MsgType = "pasted"  // Paste confirmed
-	MsgError   MsgType = "error"   // Error notification
+	MsgReady    MsgType = "ready"
+	MsgState    MsgType = "state"
+	MsgStartAck MsgType = "start_ack"
+	MsgStopAck  MsgType = "stop_ack"
+	MsgPartial  MsgType = "partial"
+	MsgFinal    MsgType = "final"
+	MsgPasted   MsgType = "pasted"
+	MsgError    MsgType = "error"
+)
+
+const (
+	StateIdle      = "idle"
+	StateRecording = "recording"
+	StateStopping  = "stopping"
 )
 
 // ServerMsg is a JSON message sent to the phone.
 type ServerMsg struct {
-	Type    MsgType `json:"type"`
-	Text    string  `json:"text,omitempty"`
-	Message string  `json:"message,omitempty"` // For errors
+	Type      MsgType `json:"type"`
+	State     string  `json:"state,omitempty"`
+	SessionID string  `json:"sessionId,omitempty"`
+	Seq       int64   `json:"seq,omitempty"`
+	Text      string  `json:"text,omitempty"`
+	Message   string  `json:"message,omitempty"` // For errors
+	Code      string  `json:"code,omitempty"`
+	Retryable bool    `json:"retryable,omitempty"`
+	TS        int64   `json:"ts,omitempty"`
 }
 
 func (m ServerMsg) Bytes() []byte {
diff --git a/web/src/protocol.ts b/web/src/protocol.ts
new file mode 100644
index 0000000..5dd90b0
--- /dev/null
+++ b/web/src/protocol.ts
@@ -0,0 +1,35 @@
+export type ClientMsgType = "hello" | "start" | "stop" | "paste" | "ping";
+
+export type ServerMsgType =
+	| "ready"
+	| "state"
+	| "start_ack"
+	| "stop_ack"
+	| "partial"
+	| "final"
+	| "pasted"
+	| "error"
+	| "pong";
+
+export type SessionState = "idle" | "recording" | "stopping";
+
+export interface ClientMsg {
+	type: ClientMsgType;
+	sessionId?: string;
+	seq?: number;
+	text?: string;
+	version?: number;
+	ts?: number;
+}
+
+export interface ServerMsg {
+	type: ServerMsgType;
+	state?: SessionState;
+	sessionId?: string;
+	seq?: number;
+	text?: string;
+	message?: string;
+	code?: string;
+	retryable?: boolean;
+	ts?: number;
+}
diff --git a/web/src/stores/app-store.ts b/web/src/stores/app-store.ts
index b381520..d782f1a 100644
--- a/web/src/stores/app-store.ts
+++ b/web/src/stores/app-store.ts
@@ -13,9 +13,13 @@ type ConnectionStatus = "connected" | "disconnected" | "connecting";
 interface AppState {
 	// Connection
 	connectionStatus: ConnectionStatus;
+	weakNetwork: boolean;
 	// Recording
 	recording: boolean;
 	pendingStart: boolean;
+	stopping: boolean;
+	micReady: boolean;
+	activeSessionId: string | null;
 	// Preview
 	previewText: string;
 	previewActive: boolean;
@@ -24,8 +28,12 @@ interface AppState {
 
 	// Actions
 	setConnectionStatus: (status: ConnectionStatus) => void;
+	setWeakNetwork: (weak: boolean) => void;
 	setRecording: (recording: boolean) => void;
 	setPendingStart: (pending: boolean) => void;
+	setStopping: (stopping: boolean) => void;
+	setMicReady: (ready: boolean) => void;
+	setActiveSessionId: (sessionId: string | null) => void;
 	setPreview: (text: string, isFinal: boolean) => void;
 	clearPreview: () => void;
 	addHistory: (text: string) => void;
@@ -36,15 +44,23 @@ export const useAppStore = create<AppState>()(
 	persist(
 		(set, get) => ({
 			connectionStatus: "connecting",
+			weakNetwork: false,
 			recording: false,
 			pendingStart: false,
+			stopping: false,
+			micReady: false,
+			activeSessionId: null,
 			previewText: "",
 			previewActive: false,
 			history: [],
 
 			setConnectionStatus: (connectionStatus) => set({ connectionStatus }),
+			setWeakNetwork: (weakNetwork) => set({ weakNetwork }),
 			setRecording: (recording) => set({ recording }),
 			setPendingStart: (pendingStart) => set({ pendingStart }),
+			setStopping: (stopping) => set({ stopping }),
+			setMicReady: (micReady) => set({ micReady }),
+			setActiveSessionId: (activeSessionId) => set({ activeSessionId }),
 
 			setPreview: (text, isFinal) =>
 				set({