diff --git a/vna_system/core/processors/base_processor.py b/vna_system/core/processors/base_processor.py
index d35c5a1..a1cf1a6 100644
--- a/vna_system/core/processors/base_processor.py
+++ b/vna_system/core/processors/base_processor.py
@@ -678,6 +678,24 @@ class BaseProcessor:
     def _get_metadata(self) -> dict[str, Any]:
         """
         Return diagnostic metadata bundled with each `ProcessedResult`.
+
+        Note: This is sent with every websocket broadcast, so it should be lightweight.
+        For full state including sweep_history, use get_full_state().
+        """
+        with self._lock:
+            return {
+                "processor_id": self.processor_id,
+                "config": self._config.copy(),
+                "history_count": len(self._sweep_history),
+                "max_history": self._max_history,
+            }
+
+    def get_full_state(self) -> dict[str, Any]:
+        """
+        Return complete processor state including sweep history.
+
+        This should be called explicitly when needed (e.g., for export/download),
+        not on every broadcast.
         """
         with self._lock:
             return {
diff --git a/vna_system/core/processors/websocket_handler.py b/vna_system/core/processors/websocket_handler.py
index 5f3aa32..dca98f5 100644
--- a/vna_system/core/processors/websocket_handler.py
+++ b/vna_system/core/processors/websocket_handler.py
@@ -102,6 +102,8 @@ class ProcessorWebSocketHandler:
                 await self._handle_get_history(websocket, message)
             elif mtype == "load_history":
                 await self._handle_load_history(websocket, message)
+            elif mtype == "get_processor_state":
+                await self._handle_get_processor_state(websocket, message)
             else:
                 await self._send_error(websocket, f"Unknown message type: {mtype!r}")
         except json.JSONDecodeError as json_error:
@@ -197,6 +199,46 @@ class ProcessorWebSocketHandler:
             logger.error("History load failed", processor_id=processor_id, error=repr(exc))
             await self._send_error(websocket, f"History load failed: {exc}")
 
+    async def _handle_get_processor_state(self, websocket: WebSocket, message: dict[str, Any]) -> None:
+        """
+        Fetch complete processor state including sweep history and current data.
+
+        This should be called explicitly by the UI (e.g., via a download/export button)
+        rather than being sent automatically with every result.
+        """
+        processor_id = message.get("processor_id")
+
+        if not processor_id:
+            await self._send_error(websocket, "processor_id is required")
+            return
+
+        try:
+            processor = self.processor_manager.get_processor(processor_id)
+            if processor is None:
+                await self._send_error(websocket, f"Processor {processor_id} not found")
+                return
+
+            # Get full state with sweep history
+            full_state = processor.get_full_state()
+
+            # Get current result to include data and plotly_config
+            current_result = processor.recalculate()
+
+            response = {
+                "type": "processor_state",
+                "processor_id": processor_id,
+                "state": full_state,
+                "current_data": {
+                    "data": current_result.data if current_result else {},
+                    "plotly_config": current_result.plotly_config if current_result else {},
+                    "timestamp": current_result.timestamp if current_result else datetime.now().timestamp(),
+                } if current_result else None,
+            }
+            await websocket.send_text(json.dumps(response))
+        except Exception as exc:  # noqa: BLE001
+            logger.error("Error getting processor state", processor_id=processor_id, error=repr(exc))
+            await self._send_error(websocket, f"Error getting processor state: {exc}")
+
     # --------------------------------------------------------------------- #
     # Outbound helpers
     # --------------------------------------------------------------------- #
@@ -224,13 +266,17 @@ class ProcessorWebSocketHandler:
             return obj
 
     def _result_to_message(self, processor_id: str, result: ProcessedResult) -> dict[str, Any]:
-        """Convert a `ProcessedResult` into a JSON-serializable message."""
+        """
+        Convert a `ProcessedResult` into a lightweight JSON-serializable message for broadcasting.
+
+        Note: This excludes heavy data fields like 'data' to minimize websocket traffic.
+        Use get_processor_state command to retrieve full data including sweep history.
+        """
         return {
             "type": "processor_result",
             "processor_id": processor_id,
             "timestamp": result.timestamp,
-            "data": self._make_json_serializable(result.data),
-            "plotly_config": self._make_json_serializable(result.plotly_config),
+            "plotly_config": result.plotly_config,
             "ui_parameters": [asdict(param) for param in result.ui_parameters],
             "metadata": self._make_json_serializable(result.metadata),
         }
diff --git a/vna_system/web_ui/static/js/modules/websocket.js b/vna_system/web_ui/static/js/modules/websocket.js
index 931a3a4..be62fcc 100644
--- a/vna_system/web_ui/static/js/modules/websocket.js
+++ b/vna_system/web_ui/static/js/modules/websocket.js
@@ -164,6 +164,9 @@ export class WebSocketManager {
                 case 'processor_history':
                     this.emit('processor_history', payload);
                     break;
+                case 'processor_state':
+                    this.emit('processor_state', payload);
+                    break;
                 case 'error':
                     console.error('Server error:', payload);
                     console.error('Error details:', {
@@ -322,6 +325,14 @@ export class WebSocketManager {
         });
     }
 
+    /** Get full processor state including sweep history (EXISTS ON BACKEND) */
+    getProcessorState(processorId) {
+        return this.send({
+            type: 'get_processor_state',
+            processor_id: processorId
+        });
+    }
+
     // === Events ===
     on(event, callback) {
         if (!this.eventListeners.has(event)) this.eventListeners.set(event, []);