fix(web): Working threads can be dragged into chat as references again (#19697)

Co-authored-by: Nikita Maximilian Grimm <github@nikitagrimm.de>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: 3 people

apps/web/src/components/Sidebar.logic.test.ts

@@ -2242,6 +2242,33 @@ describe("Working shelf (beta)", () => {
       expect(resolveSidebarDropVerb("active", "working")).toBeNull();
     });
 
+    it.each([
+      ["pinned", "p1"],
+      ["active", "a2"],
+      ["settled", "s1"],
+    ] as const)(
+      "does not move a Working thread into %s when its reference drag ends in the sidebar",
+      (section, overKey) => {
+        const target = resolveSidebarDropTarget(items, "w1", overKey);
+        expect(target?.section).toBe(section);
+        expect(
+          planSidebarThreadDrop({
+            activeKey: "w1",
+            activeSection: "working",
+            target: target!,
+            pinnedOrder: ["p1"],
+            pinnedKeysById: new Map([["p1", "m"]]),
+            activeOrder: ["a1", "a2"],
+            activeKeysById: new Map([
+              ["a1", "f"],
+              ["a2", "t"],
+            ]),
+            activeTimeOrdered: true,
+          }),
+        ).toEqual({ kind: "none" });
+      },
+    );
+
     it("arranges the rows it can write when another row's server cannot store an order", () => {
       const plan = planSidebarThreadDrop({
         activeKey: "a2",

apps/web/src/components/Sidebar.logic.ts

@@ -115,7 +115,8 @@ export const animateSidebarLayoutChanges: AnimateLayoutChanges = (args) =>
 
 // Snoozed rows can leave the shelf, but dropping into it is not supported
 // because snoozing requires a wake time. The Working shelf (beta) follows live
-// status, so it is neither a drag source nor a destination.
+// status, so its rows only drag out as chat context, never between sidebar
+// sections.
 
 export type SidebarSection = "pinned" | "active" | "working" | "snoozed" | "settled";
 
@@ -290,6 +291,7 @@ export function planSidebarThreadDrop(input: {
     activeKeysById,
     activeReorderableKeys,
   } = input;
+  if (activeSection === "working") return { kind: "none" };
   if (input.supportsSettlement === false && (target.section === "settled" || activeSettled)) {
     return { kind: "none" };
   }

apps/web/src/components/Sidebar.tsx

@@ -3314,7 +3314,8 @@ export default function Sidebar() {
     listMotionRef.current?.update(false);
   };
 
-  const isContextDrag = dragState?.contextDrag === true;
+  // Working rows can supply chat context, but never preview sidebar movement.
+  const isContextDrag = dragState?.contextDrag === true || dragState?.activeSection === "working";
   const dragTargetSection = isContextDrag ? null : (dragState?.targetSection ?? null);
   const finishThreadDrag = (started: boolean) => {
     dragSensorRef.current = null;
@@ -4799,7 +4800,6 @@ export default function Sidebar() {
                             contextDrag={isContextDrag}
                             sortableDisabled={
                               renamingThreadKey === threadKey ||
-                              section === "working" ||
                               !draggableThreadKeys.has(threadKey) ||
                               optimisticDrop !== null
                             }