diff --git a/spoolman/api/v1/models.py b/spoolman/api/v1/models.py
index a24d79f7c..08e5a10ea 100644
--- a/spoolman/api/v1/models.py
+++ b/spoolman/api/v1/models.py
@@ -406,6 +406,9 @@ class SpoolEvent(Event):
 
     payload: Spool = Field(description="Updated spool.")
     resource: Literal["spool"] = Field(description="Resource type.")
+    payload_extras: dict[str, float] | None = \
+        Field(default=None, 
+        description="Payload extra fields outside of core Spool model")
 
 
 class FilamentEvent(Event):
diff --git a/spoolman/database/spool.py b/spoolman/database/spool.py
index 5c190ce65..ac1b4750f 100644
--- a/spoolman/database/spool.py
+++ b/spoolman/database/spool.py
@@ -298,7 +298,7 @@ async def use_weight(db: AsyncSession, spool_id: int, weight: float) -> models.S
     spool.last_used = datetime.utcnow().replace(microsecond=0)
 
     await db.commit()
-    await spool_changed(spool, EventType.UPDATED)
+    await spool_changed(spool, EventType.UPDATED, {"weight_delta": weight})
     return spool
 
 
@@ -344,7 +344,7 @@ async def use_length(db: AsyncSession, spool_id: int, length: float) -> models.S
     spool.last_used = datetime.utcnow().replace(microsecond=0)
 
     await db.commit()
-    await spool_changed(spool, EventType.UPDATED)
+    await spool_changed(spool, EventType.UPDATED, {"weight_delta": weight})
     return spool
 
 
@@ -436,16 +436,18 @@ async def find_lot_numbers(
     return [row[0] for row in rows.all() if row[0] is not None]
 
 
-async def spool_changed(spool: models.Spool, typ: EventType) -> None:
+async def spool_changed(spool: models.Spool, typ: EventType, delta: Optional[dict] = None) -> None:
     """Notify websocket clients that a spool has changed."""
     try:
+        spool = Spool.from_db(spool)
         await websocket_manager.send(
             ("spool", str(spool.id)),
             SpoolEvent(
                 type=typ,
                 resource="spool",
                 date=datetime.utcnow(),
-                payload=Spool.from_db(spool),
+                payload=spool,
+                payload_extras=delta 
             ),
         )
     except Exception:
diff --git a/tests_integration/requirements.txt b/tests_integration/requirements.txt
index 9c84ad6b0..d23ac877c 100644
--- a/tests_integration/requirements.txt
+++ b/tests_integration/requirements.txt
@@ -1,3 +1,4 @@
 pytest==8.3.2
 pytest-asyncio==0.23.8
 httpx==0.27.0
+websockets==15.0.1
diff --git a/tests_integration/tests/spool/test_spool_event.py b/tests_integration/tests/spool/test_spool_event.py
new file mode 100644
index 000000000..c605933d0
--- /dev/null
+++ b/tests_integration/tests/spool/test_spool_event.py
@@ -0,0 +1,51 @@
+"""Integration tests for spool websocket events."""
+
+import asyncio
+import json
+from typing import Any
+
+import httpx
+import pytest
+import websockets
+
+from ..conftest import URL
+
+
+@pytest.mark.asyncio
+async def test_use_weight_websocket_has_weight_delta(random_filament: dict[str, Any]):
+    """Test websocket payload extras for spool weight usage."""
+    #Setup
+    result = httpx.post(
+        f"{URL}/api/v1/spool",
+        json={"filament_id": random_filament["id"], "remaining_weight": 1000},
+    )
+    result.raise_for_status()
+    spool = result.json()
+    spool_id = spool["id"]
+    ws_url = URL.replace("http://", "ws://").replace("https://", "wss://") + f"/api/v1/spool/{spool_id}"
+    use_weight = 6.9
+
+    try:
+        async with websockets.connect(ws_url) as ws:
+            # keep the socket loop healthy before triggering update
+            await ws.send("ping")
+            check = json.loads(await asyncio.wait_for(ws.recv(), timeout=2))
+            assert check["status"] == "healthy"
+
+            #execute
+            r = httpx.put(f"{URL}/api/v1/spool/{spool_id}/use", json={"use_weight": use_weight})
+            r.raise_for_status()
+            raw = await asyncio.wait_for(ws.recv(), timeout=5)
+            evt = json.loads(raw)
+            #verify
+            assert evt["resource"] == "spool"
+            assert evt["type"] == "updated"
+            assert evt["payload"]["id"] == spool_id
+            assert evt["payload_extras"]["weight_delta"] == pytest.approx(use_weight)
+            assert "event_delta" not in evt["payload"].get("extra", {})
+            #cleanup-ws
+            await ws.close(code=1000)
+            await asyncio.sleep(0.6)
+    finally:
+        #cleanup
+        httpx.delete(f"{URL}/api/v1/spool/{spool_id}").raise_for_status()