diff --git a/backend/app/api/routes/edges.py b/backend/app/api/routes/edges.py
index ba49256..4d63530 100644
--- a/backend/app/api/routes/edges.py
+++ b/backend/app/api/routes/edges.py
@@ -4,7 +4,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.deps import get_current_user
 from app.db.database import get_db
-from app.db.models import Edge
+from app.db.models import Design, Edge
 from app.schemas.edges import EdgeCreate, EdgeResponse, EdgeUpdate
 
 router = APIRouter()
@@ -18,7 +18,14 @@ async def list_edges(db: AsyncSession = Depends(get_db), _: str = Depends(get_cu
 
 @router.post("", response_model=EdgeResponse, status_code=status.HTTP_201_CREATED)
 async def create_edge(body: EdgeCreate, db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)) -> Edge:
-    edge = Edge(**body.model_dump())
+    data = body.model_dump()
+    # Same reconciliation as nodes: clients omitting design_id (MCP write tools)
+    # would create design_id=null edges that never render until a restart.
+    # Fall back to the first design so the edge attaches to a canvas.
+    if data.get("design_id") is None:
+        first_design = (await db.execute(select(Design).order_by(Design.created_at).limit(1))).scalar()
+        data["design_id"] = first_design.id if first_design else None
+    edge = Edge(**data)
     db.add(edge)
     await db.commit()
     await db.refresh(edge)
diff --git a/backend/app/api/routes/nodes.py b/backend/app/api/routes/nodes.py
index a773995..30d3f28 100644
--- a/backend/app/api/routes/nodes.py
+++ b/backend/app/api/routes/nodes.py
@@ -4,7 +4,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.deps import get_current_user
 from app.db.database import get_db
-from app.db.models import Node
+from app.db.models import Design, Node
 from app.schemas.nodes import NodeCreate, NodeResponse, NodeUpdate
 
 router = APIRouter()
@@ -18,7 +18,15 @@ async def list_nodes(db: AsyncSession = Depends(get_db), _: str = Depends(get_cu
 
 @router.post("", response_model=NodeResponse, status_code=status.HTTP_201_CREATED)
 async def create_node(body: NodeCreate, db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)) -> Node:
-    node = Node(**body.model_dump())
+    data = body.model_dump()
+    # Attach to a design so the node lands on a canvas. Clients that don't send a
+    # design_id (e.g. the MCP write tools) would otherwise create design_id=null
+    # nodes that exist in the DB but never render in the UI until a container
+    # restart reconciles them. Fall back to the first design, matching bulk-approve.
+    if data.get("design_id") is None:
+        first_design = (await db.execute(select(Design).order_by(Design.created_at).limit(1))).scalar()
+        data["design_id"] = first_design.id if first_design else None
+    node = Node(**data)
     db.add(node)
     await db.commit()
     await db.refresh(node)
diff --git a/backend/app/schemas/edges.py b/backend/app/schemas/edges.py
index 05db453..85964d8 100644
--- a/backend/app/schemas/edges.py
+++ b/backend/app/schemas/edges.py
@@ -51,6 +51,7 @@ class EdgeUpdate(BaseModel):
 
 class EdgeResponse(EdgeBase):
     id: str
+    design_id: str | None = None
     created_at: datetime
 
     model_config = {"from_attributes": True}
diff --git a/backend/tests/test_edges.py b/backend/tests/test_edges.py
index 3665650..e9a560d 100644
--- a/backend/tests/test_edges.py
+++ b/backend/tests/test_edges.py
@@ -97,6 +97,37 @@ async def test_create_edge_requires_auth(client: AsyncClient, two_nodes):
     assert res.status_code == 401
 
 
+async def test_create_edge_without_design_id_falls_back_to_first_design(client: AsyncClient, headers: dict, two_nodes):
+    # Regression for #225: MCP create_edge sent no design_id, so edges were
+    # persisted with design_id=null and never rendered until a restart.
+    src, tgt = two_nodes
+    design = await client.post("/api/v1/designs", json={"name": "Primary"}, headers=headers)
+    design_id = design.json()["id"]
+
+    res = await client.post(
+        "/api/v1/edges",
+        json={"source": src, "target": tgt, "type": "ethernet"},
+        headers=headers,
+    )
+    assert res.status_code == 201
+    assert res.json()["design_id"] == design_id
+
+
+async def test_create_edge_respects_explicit_design_id(client: AsyncClient, headers: dict, two_nodes):
+    src, tgt = two_nodes
+    await client.post("/api/v1/designs", json={"name": "First"}, headers=headers)
+    second = await client.post("/api/v1/designs", json={"name": "Second"}, headers=headers)
+    second_id = second.json()["id"]
+
+    res = await client.post(
+        "/api/v1/edges",
+        json={"source": src, "target": tgt, "type": "ethernet", "design_id": second_id},
+        headers=headers,
+    )
+    assert res.status_code == 201
+    assert res.json()["design_id"] == second_id
+
+
 async def test_create_cluster_edge_with_handles(client: AsyncClient, headers: dict, two_nodes):
     src, tgt = two_nodes
     res = await client.post(
diff --git a/backend/tests/test_nodes.py b/backend/tests/test_nodes.py
index 048e5c3..fafe670 100644
--- a/backend/tests/test_nodes.py
+++ b/backend/tests/test_nodes.py
@@ -67,6 +67,50 @@ async def test_update_node_not_found(client: AsyncClient, headers: dict):
     assert res.status_code == 404
 
 
+async def test_create_node_without_design_id_falls_back_to_first_design(client: AsyncClient, headers: dict):
+    # Regression for #225: MCP create_node sent no design_id, so nodes were
+    # persisted with design_id=null and never rendered on the canvas until a
+    # container restart reconciled them. They must attach to a design on create.
+    design = await client.post("/api/v1/designs", json={"name": "Primary"}, headers=headers)
+    design_id = design.json()["id"]
+
+    res = await client.post(
+        "/api/v1/nodes",
+        json={"type": "generic", "label": "mcp-node", "ip": "192.168.18.99"},
+        headers=headers,
+    )
+    assert res.status_code == 201
+    assert res.json()["design_id"] == design_id
+
+
+async def test_create_node_respects_explicit_design_id(client: AsyncClient, headers: dict):
+    # When a design_id is supplied it must win over the first-design fallback.
+    first = await client.post("/api/v1/designs", json={"name": "First"}, headers=headers)
+    second = await client.post("/api/v1/designs", json={"name": "Second"}, headers=headers)
+    second_id = second.json()["id"]
+    assert first.json()["id"] != second_id
+
+    res = await client.post(
+        "/api/v1/nodes",
+        json={"type": "generic", "label": "n", "design_id": second_id},
+        headers=headers,
+    )
+    assert res.status_code == 201
+    assert res.json()["design_id"] == second_id
+
+
+async def test_create_node_without_any_design_stays_null(client: AsyncClient, headers: dict):
+    # No designs exist yet: fallback can't invent one, so design_id stays null
+    # rather than erroring.
+    res = await client.post(
+        "/api/v1/nodes",
+        json={"type": "generic", "label": "orphan"},
+        headers=headers,
+    )
+    assert res.status_code == 201
+    assert res.json()["design_id"] is None
+
+
 async def test_delete_node_not_found(client: AsyncClient, headers: dict):
     res = await client.delete("/api/v1/nodes/nonexistent", headers=headers)
     assert res.status_code == 404
diff --git a/mcp/app/resources.py b/mcp/app/resources.py
index e14f1ed..386f416 100644
--- a/mcp/app/resources.py
+++ b/mcp/app/resources.py
@@ -21,6 +21,10 @@ ROUTES = {
 
 
 async def read_resource(uri: str) -> list[TextContent]:
+    # The MCP framework hands us a pydantic AnyUrl, not a plain str, so string
+    # ops like .startswith / dict lookups blow up with
+    # "'AnyUrl' object has no attribute 'startswith'". Coerce to str first.
+    uri = str(uri)
     if uri.startswith("homelable://nodes/") and uri != "homelable://nodes/":
         node_id = uri.split("/")[-1]
         data = await backend.get(f"/api/v1/nodes/{node_id}")
diff --git a/mcp/tests/test_resources.py b/mcp/tests/test_resources.py
index 36f5d7f..5bc0c2d 100644
--- a/mcp/tests/test_resources.py
+++ b/mcp/tests/test_resources.py
@@ -1,4 +1,5 @@
 import pytest
+from pydantic import AnyUrl
 from unittest.mock import AsyncMock, patch
 from app.resources import read_resource
 
@@ -45,3 +46,24 @@ async def test_read_scan_pending(mock_backend):
 async def test_read_unknown_uri(mock_backend):
     with pytest.raises(ValueError, match="Unknown resource URI"):
         await read_resource("homelable://unknown")
+
+
+@pytest.mark.anyio
+async def test_read_resource_accepts_anyurl(mock_backend):
+    # Regression for #225: the MCP framework calls the handler with a pydantic
+    # AnyUrl, not a str, which raised "'AnyUrl' object has no attribute
+    # 'startswith'". The handler must coerce to str and still route correctly.
+    await read_resource(AnyUrl("homelable://canvas"))
+    mock_backend.get.assert_called_once_with("/api/v1/canvas")
+
+
+@pytest.mark.anyio
+async def test_read_edges_anyurl(mock_backend):
+    await read_resource(AnyUrl("homelable://edges"))
+    mock_backend.get.assert_called_once_with("/api/v1/edges")
+
+
+@pytest.mark.anyio
+async def test_read_single_node_anyurl(mock_backend):
+    await read_resource(AnyUrl("homelable://nodes/abc123"))
+    mock_backend.get.assert_called_once_with("/api/v1/nodes/abc123")