fix(opencode): retain live subagents skipped during reconnect

packages/server/src/server/agent/providers/opencode/v2/children.test.ts

@@ -68,7 +68,7 @@ function setupTree() {
       .list("parent")
       .map((child) => child.id)
       .sort();
-  return { harness, sessions, children, ids };
+  return { harness, sessions, children, ids, store };
 }
 
 describe("OpenCode v2 child presentation", () => {
@@ -145,6 +145,68 @@ describe("OpenCode v2 child presentation", () => {
     expect(ids()).toEqual(["first", "grandchild", "second"]);
   });
 
+  test("retains a live child and descendants when an update moves it ahead of the reconnect cursor", async () => {
+    const { harness, sessions, children, ids, store } = setupTree();
+    for (let i = 3; i <= 101; i++) {
+      sessions.set(`child-${i}`, {
+        ...harness.info,
+        id: `child-${i}`,
+        parentID: "session",
+        time: { created: i, updated: i },
+      });
+    }
+    sessions.get("second")!.time = { created: 2, updated: 2 };
+    await children.reconcile("session");
+    const expected = ids();
+    expect(expected).toHaveLength(102);
+    const list = harness.api.session.list;
+    harness.api.session.list = async (input) => {
+      if (input?.parentID !== "session" && !input?.cursor) return list(input);
+      const page = [...sessions.values()]
+        .filter((info) => info.parentID === "session")
+        .filter((info) => !input.cursor || info.time.updated < Number(input.cursor))
+        .sort((a, b) => b.time.updated - a.time.updated)
+        .slice(0, input.limit);
+      const next = page.length === input.limit ? String(page.at(-1)!.time.updated) : undefined;
+      if (!input.cursor) {
+        // The oldest child was not on page one. Updating it moves it ahead of that page's cursor.
+        const first = sessions.get("first")!;
+        first.time = { ...first.time, updated: 200 };
+        first.title = "Updated during reconnect";
+      }
+      return { data: page, cursor: { next } };
+    };
+    await children.reconcile("session");
+    expect(ids()).toEqual(expected);
+    await children.observe({
+      id: "queued-update",
+      created: 200,
+      type: "session.execution.started",
+      durable: { aggregateID: "first", seq: 1, version: 1 },
+      data: { sessionID: "first" },
+    });
+    expect(ids()).toEqual(expected);
+    expect(store.list("parent").find((child) => child.id === "first")).toMatchObject({
+      title: "Updated during reconnect",
+    });
+  });
+
+  test("retains an absent child's subtree when its existence cannot be confirmed", async () => {
+    const { harness, sessions, children, ids } = setupTree();
+    await children.reconcile("session");
+    sessions.delete("first");
+    sessions.delete("grandchild");
+    const get = harness.api.session.get;
+    harness.api.session.get = async () => {
+      throw new Error("Provider disconnected");
+    };
+    await children.reconcile("session");
+    expect(ids()).toEqual(["first", "grandchild", "second"]);
+    harness.api.session.get = get;
+    await children.reconcile("session");
+    expect(ids()).toEqual(["second"]);
+  });
+
   test("keeps missing children when a listing fails before its last page", async () => {
     const { harness, sessions, children, ids } = setupTree();
     await children.reconcile("session");

packages/server/src/server/agent/providers/opencode/v2/children.ts

@@ -1,6 +1,6 @@
 import { V2Timeline } from "./timeline.js";
 
-import type { SessionInfo } from "@opencode/client";
+import { isSessionNotFoundError, type SessionInfo } from "@opencode/client";
 
 import type { AgentStreamEvent } from "../../../agent-sdk-types.js";
 
@@ -62,9 +62,14 @@ export class SessionChildren {
       }
       cursor = page.cursor.next ?? undefined;
     } while (cursor);
-    // A complete parent listing is authoritative. Do not prune on a partial or failed page.
+    // Updates can move a live child ahead of the cursor. Confirm deletion before pruning.
     for (const [id] of previous) {
-      if (!seen.has(id)) this.remove(id);
+      if (seen.has(id)) continue;
+      try {
+        await this.options.client().session.get({ sessionID: id });
+      } catch (error) {
+        if (isSessionNotFoundError(error)) this.remove(id);
+      }
     }
   }
   private remove(id: string) {