From 1eba8d5a78fb0557a151e4565f14842202d5f104 Mon Sep 17 00:00:00 2001
From: peterkogo <peter@xyflow.com>
Date: Tue, 19 Aug 2025 15:14:39 +0200
Subject: [PATCH 1/3] extend onBeforeConnect type to allow void & null & false

---
 packages/svelte/src/lib/components/Handle/Handle.svelte | 2 +-
 packages/svelte/src/lib/types/general.ts                | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/svelte/src/lib/components/Handle/Handle.svelte b/packages/svelte/src/lib/components/Handle/Handle.svelte
index 48946d41..b04a20fc 100644
--- a/packages/svelte/src/lib/components/Handle/Handle.svelte
+++ b/packages/svelte/src/lib/components/Handle/Handle.svelte
@@ -98,7 +98,7 @@
     });
 
   function onConnectExtended(connection: Connection) {
-    const edge = store.onbeforeconnect?.(connection) ?? connection;
+    const edge = store.onbeforeconnect ? store.onbeforeconnect(connection) : connection;
 
     if (!edge) {
       return;
diff --git a/packages/svelte/src/lib/types/general.ts b/packages/svelte/src/lib/types/general.ts
index 701496e9..77ab58b7 100644
--- a/packages/svelte/src/lib/types/general.ts
+++ b/packages/svelte/src/lib/types/general.ts
@@ -38,11 +38,11 @@ export type OnDelete<NodeType extends Node = Node, EdgeType extends Edge = Edge>
 
 export type OnBeforeConnect<EdgeType extends Edge = Edge> = (
   connection: Connection
-) => EdgeType | Connection | void;
+) => EdgeType | Connection | void | false | null;
 export type OnBeforeReconnect<EdgeType extends Edge = Edge> = (
   newEdge: EdgeType,
   oldEdge: EdgeType
-) => EdgeType | void;
+) => EdgeType | void | false | null;
 export type OnBeforeDelete<
   NodeType extends Node = Node,
   EdgeType extends Edge = Edge

From 100c95fd5ab40191bfce1251bf321f770080679b Mon Sep 17 00:00:00 2001
From: peterkogo <peter@xyflow.com>
Date: Tue, 19 Aug 2025 15:15:56 +0200
Subject: [PATCH 2/3] add changeset

---
 .changeset/quick-radios-yell.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/quick-radios-yell.md

diff --git a/.changeset/quick-radios-yell.md b/.changeset/quick-radios-yell.md
new file mode 100644
index 00000000..084405a4
--- /dev/null
+++ b/.changeset/quick-radios-yell.md
@@ -0,0 +1,5 @@
+---
+'@xyflow/svelte': patch
+---
+
+Allow returning void, false and null from onbeforeconnect

From a00a6385b7ae93c54a68b398a399c87a8bf5bc2e Mon Sep 17 00:00:00 2001
From: peterkogo <peter@xyflow.com>
Date: Tue, 19 Aug 2025 15:31:22 +0200
Subject: [PATCH 3/3] fix edge reconnection

---
 .../EdgeReconnectAnchor/EdgeReconnectAnchor.svelte   | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/packages/svelte/src/lib/components/EdgeReconnectAnchor/EdgeReconnectAnchor.svelte b/packages/svelte/src/lib/components/EdgeReconnectAnchor/EdgeReconnectAnchor.svelte
index d18bc2e8..81f0ab2d 100644
--- a/packages/svelte/src/lib/components/EdgeReconnectAnchor/EdgeReconnectAnchor.svelte
+++ b/packages/svelte/src/lib/components/EdgeReconnectAnchor/EdgeReconnectAnchor.svelte
@@ -50,7 +50,6 @@
       edgeLookup
     } = store;
 
-    let newEdge: Edge | undefined;
     let edge = edgeLookup.get(edgeId)!;
 
     const _onConnectStart: OnConnectStart = (evt, params) => {
@@ -86,13 +85,16 @@
       onConnectStart: _onConnectStart,
       onConnectEnd: onconnectend,
       onConnect: (connection) => {
-        newEdge = { ...edge, ...connection };
-        newEdge = onbeforereconnect ? (onbeforereconnect(newEdge, edge) ?? undefined) : newEdge;
+        const reconnectedEdge = { ...edge, ...connection };
+        const newEdge = onbeforereconnect
+          ? onbeforereconnect(reconnectedEdge, edge)
+          : reconnectedEdge;
 
-        if (newEdge) {
-          store.edges = store.edges.map((e) => (e.id === edge.id ? (newEdge as Edge) : e));
+        if (!newEdge) {
+          return;
         }
 
+        store.edges = store.edges.map((e) => (e.id === edge.id ? (newEdge as Edge) : e));
         onreconnect?.(edge, connection);
       },
       onReconnectEnd: (event, connectionState) => {