diff --git a/packages/opencode/src/cli/cmd/run/stream.transport.ts b/packages/opencode/src/cli/cmd/run/stream.transport.ts
index 4c3f2a589a1b..ad8db111c6f1 100644
--- a/packages/opencode/src/cli/cmd/run/stream.transport.ts
+++ b/packages/opencode/src/cli/cmd/run/stream.transport.ts
@@ -400,8 +400,12 @@ const collectDescendantSessions = Effect.fn("RunStreamTransport.collectDescendan
     const levels = yield* Effect.all(
       frontier.map((sessionID) =>
         Effect.promise(() => sdk.session.children({ sessionID })).pipe(
-          Effect.map((item) => item.data ?? []),
-          Effect.orElseSucceed(() => []),
+          Effect.flatMap((item) => {
+            if (item.error) {
+              return Effect.fail(new Error(`failed to list child sessions for ${sessionID}`, { cause: item.error }))
+            }
+            return Effect.succeed(item.data ?? [])
+          }),
         ),
       ),
       { concurrency: "unbounded" },
diff --git a/packages/opencode/test/cli/run/stream.transport.test.ts b/packages/opencode/test/cli/run/stream.transport.test.ts
index 320e72ccf9b4..98dd8f4ba093 100644
--- a/packages/opencode/test/cli/run/stream.transport.test.ts
+++ b/packages/opencode/test/cli/run/stream.transport.test.ts
@@ -1525,6 +1525,40 @@ describe("run stream transport", () => {
     }
   })
 
+  test("fails bootstrap when descendant discovery fails", async () => {
+    const src = eventFeed()
+    const ui = footer()
+    const children = (async ({ sessionID }: { sessionID: string }) => {
+      if (sessionID === "session-1") return ok([child("child-1")])
+      return {
+        data: undefined,
+        error: {
+          name: "NotFoundError",
+          data: { message: "child lookup failed" },
+        },
+        request: new Request("https://opencode.test"),
+        response: new Response(undefined, { status: 404 }),
+      }
+    }) as OpencodeClient["session"]["children"]
+    const result = createSessionTransport({
+      sdk: sdk({
+        stream: src.stream,
+        children,
+      }),
+      sessionID: "session-1",
+      thinking: true,
+      limits: () => ({}),
+      footer: ui.api,
+    })
+
+    try {
+      await expect(result).rejects.toThrow("failed to list child sessions for child-1")
+    } finally {
+      src.close()
+      await result.then((transport) => transport.close()).catch(() => undefined)
+    }
+  })
+
   test("bootstraps child session output before selection", async () => {
     const ui = footer()
     const transport = await createSessionTransport({
diff --git a/packages/tui/src/routes/session/index.tsx b/packages/tui/src/routes/session/index.tsx
index 22a4e25b231b..8f2d7838863c 100644
--- a/packages/tui/src/routes/session/index.tsx
+++ b/packages/tui/src/routes/session/index.tsx
@@ -232,7 +232,7 @@ export function Session() {
       : [],
   )
   const subtree = createMemo(() => {
-    // NOTE: 仅根会话收集整棵子树的权限/问题；子会话自身不重复收集（避免与父视图双重展示）
+    // Only root sessions collect subtree requests; child views do not duplicate them.
     const s = session()
     if (!s || s.parentID) return []
     return collectSubtree(sync.data.session, s.id)
diff --git a/packages/tui/test/routes/session/collect-subtree.test.ts b/packages/tui/test/routes/session/collect-subtree.test.ts
index 20a9af7e7f2a..0b6e6b595d83 100644
--- a/packages/tui/test/routes/session/collect-subtree.test.ts
+++ b/packages/tui/test/routes/session/collect-subtree.test.ts
@@ -41,10 +41,25 @@ describe("collectSubtree", () => {
       s({ id: "child-2", parentID: "root" }),
       s({ id: "grandchild-2", parentID: "child-2" }),
     ]
-    expect(collectSubtree(sessions, "root").map((x) => x.id).sort()).toEqual(
-      ["child-1", "child-2", "grandchild-1", "grandchild-2", "root"],
-    )
-    expect(collectSubtree(sessions, "child-1").map((x) => x.id).sort()).toEqual(["child-1", "grandchild-1"])
+    expect(
+      collectSubtree(sessions, "root")
+        .map((x) => x.id)
+        .sort(),
+    ).toEqual(["child-1", "child-2", "grandchild-1", "grandchild-2", "root"])
+    expect(
+      collectSubtree(sessions, "child-1")
+        .map((x) => x.id)
+        .sort(),
+    ).toEqual(["child-1", "grandchild-1"])
+  })
+
+  test("preserves breadth-first order and session identity", () => {
+    const root = s({ id: "root" })
+    const first = s({ id: "first", parentID: "root" })
+    const grandchild = s({ id: "grandchild", parentID: "first" })
+    const second = s({ id: "second", parentID: "root" })
+
+    expect(collectSubtree([root, first, grandchild, second], "root")).toEqual([root, first, second, grandchild])
   })
 
   test("includes root itself in the result", () => {
@@ -58,10 +73,7 @@ describe("collectSubtree", () => {
   })
 
   test("does not loop forever on a parentID cycle", () => {
-    const sessions = [
-      s({ id: "root", parentID: "child" }),
-      s({ id: "child", parentID: "root" }),
-    ]
+    const sessions = [s({ id: "root", parentID: "child" }), s({ id: "child", parentID: "root" })]
     const ids = collectSubtree(sessions, "root").map((x) => x.id)
     expect(ids).toContain("root")
     expect(ids).toContain("child")