diff --git a/cloud/server.py b/cloud/server.py
index 0f4f4e3..e9ca411 100644
--- a/cloud/server.py
+++ b/cloud/server.py
@@ -482,12 +482,15 @@ def _extract_thread(result):
     return None
 
 
-def _pick_latest_thread(threads):
+def _pick_latest_thread(threads, include_archived=False):
     """cwd 过滤返回多个 thread 时的取用规则：取最新一个非
     archived。协议说明：Thread 对象本身没有 archived 字段，
     非归档由 thread/list 的 archived 过滤保证（不传 archived
     时只回非归档 thread）；这里只防御性地跳过显式带
     archived 真值的条目（CLI 形状若补了该字段时仍正确）。
+    include_archived 为真时不跳过（unarchive 解析专用的
+    已归档列表；实测 archived 列表里条目的 archived 字段
+    为 None，不跳过也能命中，但显式放行更稳）。
     最新 = updatedAt 最大，缺失时退 createdAt，再缺失时按
     列表原顺序取后者（同秒时后到的更新）。"""
     best = None
@@ -495,7 +498,7 @@ def _pick_latest_thread(threads):
     for idx, item in enumerate(threads):
         if not isinstance(item, dict):
             continue
-        if item.get("archived"):
+        if item.get("archived") and not include_archived:
             continue
         ts = item.get("updatedAt")
         if ts is None:
@@ -4242,10 +4245,12 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                     " thread ops must run there" % worktree_host)
         return None
 
-    def _list_task_threads(self, task):
+    def _list_task_threads(self, task, archived=False):
         """对任务调 thread-list：返回 (threads, codex_home, cwd,
         err, provider)，err 为 (status, msg) 或 None。cwd 过滤
         用任务 worktree（见 _thread_worktree_for_task）。
+        archived 为真时传 --archived，只列已归档 thread
+        （unarchive 解析专用；不传时只列非归档）。
 
         候选按序穷尽，首个非空即停（thread 操作不是热路径，
         多次 CLI 调用可接受）：
@@ -4275,10 +4280,13 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
             providers.append("sub2api")
         first_error = None
         any_success = False
+        list_argv = ["thread-list", "--cwd", cwd]
+        if archived:
+            list_argv.append("--archived")
         for home in homes:
             for provider in providers:
                 ok, result = _run_host_cli(
-                    ["thread-list", "--cwd", cwd], home,
+                    list_argv, home,
                     model_provider=provider)
                 if not ok:
                     if first_error is None:
@@ -4297,18 +4305,21 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
             return None, None, None, (502, first_error), None
         return [], codex_home, cwd, None, None
 
-    def _resolve_task_thread(self, task):
+    def _resolve_task_thread(self, task, archived=False):
         """单线程端点的解析：thread-list 后按 _pick_latest_thread
-        取最新一个非 archived。返回 (thread, codex_home, cwd,
-        err, provider)；零个 thread 时 err 为 (404, "thread not
-        found")。provider 必须原样带给后续的 thread-read /
-        rename / archive CLI——同一 thread 在另一 provider
-        进程里同样看不到，丢了它改操作会 502。"""
+        取最新一个非 archived（archived 为真时取最新一个已归档，
+        unarchive 专用——不传时只列非归档，刚归档的 thread
+        永远解析不到，unarchive 也就永远 404）。返回 (thread,
+        codex_home, cwd, err, provider)；零个 thread 时 err 为
+        (404, "thread not found")。provider 必须原样带给后续的
+        thread-read / rename / archive CLI——同一 thread 在另一
+        provider 进程里同样看不到，丢了它改操作会 502。"""
         threads, codex_home, cwd, err, provider = \
-            self._list_task_threads(task)
+            self._list_task_threads(task, archived=archived)
         if err is not None:
             return None, None, None, err, None
-        thread = _pick_latest_thread(threads)
+        thread = _pick_latest_thread(threads,
+                                     include_archived=archived)
         if thread is None:
             return None, None, None, (404, "thread not found"), None
         return thread, codex_home, cwd, None, provider
@@ -4370,10 +4381,13 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                               "thread": full})
 
     def _task_thread_mutate(self, user_id, task_id, argv, audit_action,
-                            audit_detail, timeout=60):
+                            audit_detail, timeout=60,
+                            resolve_archived=False):
         """线程改操作的公共流程：权限用项目 create_task；只允许
         终态任务（completed/failed/interrupted），running/queued
-        一律 409；解析 thread 后调对应 CLI，成功记审计。"""
+        一律 409；解析 thread 后调对应 CLI，成功记审计。
+        resolve_archived 只供 unarchive：已归档 thread 只能在
+        --archived 列表里找到，走普通解析永远 404。"""
         task, err = self._thread_task(user_id, task_id, "create_task")
         if err is not None:
             self._send_json(err[0], {"error": err[1]})
@@ -4388,7 +4402,7 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                 "status": task["status"]})
             return
         thread, codex_home, _cwd, err, provider = \
-            self._resolve_task_thread(task)
+            self._resolve_task_thread(task, archived=resolve_archived)
         if err is not None:
             self._send_json(err[0], {"error": err[1]})
             return
@@ -4432,9 +4446,13 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
 
     def _task_thread_unarchive(self, user_id, task_id):
         """POST /tasks/{id}/thread/unarchive：thread/unarchive。
-        记 thread_unarchived 审计。"""
+        记 thread_unarchived 审计。注意：必须走已归档解析
+        （resolve_archived）——刚归档的 thread 只在
+        --archived 列表里，普通解析永远 404，unarchive 也就
+        永远跑不通；这是 #103 时代的逻辑 bug，本批修。"""
         self._task_thread_mutate(user_id, task_id, ["thread-unarchive"],
-                                 "thread_unarchived", "%s unarchived")
+                                 "thread_unarchived", "%s unarchived",
+                                 resolve_archived=True)
 
     def _task_thread_compact(self, user_id, task_id):
         """POST /tasks/{id}/thread/compact：thread/compact/start。
diff --git a/cloud/tests/test_thread_unarchive.py b/cloud/tests/test_thread_unarchive.py
new file mode 100644
index 0000000..35de5cc
--- /dev/null
+++ b/cloud/tests/test_thread_unarchive.py
@@ -0,0 +1,151 @@
+"""unarchive 解析单测：已归档 thread 只能在 --archived 列表里。
+
+背景（生产实测 2026-10-28，探针 probe9）：thread/archive
+200 后 thread/unarchive 稳定 404。根因是 #103 时代的
+逻辑 bug：unarchive 走普通解析，普通 thread-list 不传
+--archived 时只回非归档 thread，刚归档的 thread 永远
+解析不到。本批修法：解析加 archived 模式，unarchive
+专走该模式；其余改操作（rename/archive/compact）不动，
+仍走非归档解析。
+
+不跑真实模型、不调真实 host.py：_run_host_cli 均 stub。
+"""
+
+import os
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+from unittest import mock
+
+try:
+    import cloud.server as server_mod
+    from cloud.server import (
+        CloudControlPlaneHandler,
+        _pick_latest_thread,
+    )
+except ImportError:
+    sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+    import cloud.server as server_mod
+    from cloud.server import (
+        CloudControlPlaneHandler,
+        _pick_latest_thread,
+    )
+
+
+def _handler(tmp):
+    h = CloudControlPlaneHandler.__new__(CloudControlPlaneHandler)
+    srv = mock.Mock()
+    srv.tenants_root = os.path.join(tmp, "tenants")
+    srv.host_worktrees_dir = os.path.join(tmp, "worktrees")
+    h.server = srv
+    return h
+
+
+class ArchivedResolveTestCase(unittest.TestCase):
+    def _stub(self, calls, plain, archived):
+        def fake_cli(argv, home, model_provider=None, **kwargs):
+            calls.append(list(argv))
+            if "--archived" in argv:
+                return True, {"data": archived}
+            return True, {"data": plain}
+        return fake_cli
+
+    def test_archived_list_passes_flag(self):
+        # 生产形状：archived 列表里条目的 archived 字段为 None。
+        thread = {"id": "t-a", "updatedAt": 100, "archived": None}
+        calls = []
+        with tempfile.TemporaryDirectory() as tmp:
+            h = _handler(tmp)
+            task = {"id": "task-1", "project_id": "proj-1"}
+            with mock.patch.object(
+                    server_mod, "_run_host_cli",
+                    self._stub(calls, [], [thread])), \
+                    mock.patch.object(
+                        server_mod, "_local_worker_codex_home",
+                        return_value=None):
+                threads, _h, _c, err, _p = \
+                    h._list_task_threads(task, archived=True)
+        self.assertIsNone(err)
+        self.assertEqual(threads, [thread])
+        self.assertIn("--archived", calls[0])
+
+    def test_plain_resolve_404s_when_only_archived_exists(self):
+        # 这就是探针里 404 的原样：普通列表空、归档列表有。
+        thread = {"id": "t-a", "updatedAt": 100, "archived": None}
+        with tempfile.TemporaryDirectory() as tmp:
+            h = _handler(tmp)
+            task = {"id": "task-1", "project_id": "proj-1"}
+            with mock.patch.object(
+                    server_mod, "_run_host_cli",
+                    self._stub([], [], [thread])), \
+                    mock.patch.object(
+                        server_mod, "_local_worker_codex_home",
+                        return_value=None):
+                _t, _h, _c, err, _p = h._resolve_task_thread(task)
+                self.assertEqual(err, (404, "thread not found"))
+                got, _h, _c, err2, _p = \
+                    h._resolve_task_thread(task, archived=True)
+        self.assertIsNone(err2)
+        self.assertEqual(got["id"], "t-a")
+
+    def test_pick_latest_archived_flag(self):
+        thread = {"id": "t-a", "updatedAt": 100, "archived": True}
+        self.assertIsNone(_pick_latest_thread([thread]))
+        self.assertEqual(
+            _pick_latest_thread([thread], include_archived=True),
+            thread)
+
+
+class UnarchiveMutateTestCase(unittest.TestCase):
+    def test_unarchive_resolves_archived_and_calls_cli(self):
+        thread = {"id": "t-a"}
+        task = {"id": "task-1", "project_id": "proj-1",
+                "status": "completed"}
+        seen = {}
+        with tempfile.TemporaryDirectory() as tmp:
+            h = _handler(tmp)
+            h.server.db_path = os.path.join(tmp, "control.db")
+
+            def fake_resolve(task_arg, archived=False):
+                seen["archived"] = archived
+                return thread, "/home/tenant", "/wt", None, "sub2api"
+
+            def fake_cli(argv, home, timeout=60, model_provider=None,
+                         **kwargs):
+                seen["argv"] = argv
+                seen["provider"] = model_provider
+                return True, {}
+
+            store = mock.Mock()
+            ctx = mock.Mock()
+            ctx.__enter__ = mock.Mock(return_value=store)
+            ctx.__exit__ = mock.Mock(return_value=False)
+            sent = {}
+
+            def fake_send(status, body):
+                sent["status"] = status
+                sent["body"] = body
+
+            with mock.patch.object(h, "_thread_task",
+                                   return_value=(task, None)), \
+                    mock.patch.object(h, "_thread_task_guard",
+                                      return_value=None), \
+                    mock.patch.object(h, "_resolve_task_thread",
+                                      fake_resolve), \
+                    mock.patch.object(server_mod, "_run_host_cli",
+                                      fake_cli), \
+                    mock.patch.object(server_mod, "_auth_store",
+                                      return_value=ctx), \
+                    mock.patch.object(h, "_send_json", fake_send):
+                h._task_thread_unarchive("user-1", "task-1")
+        self.assertTrue(seen["archived"])
+        self.assertEqual(seen["argv"],
+                         ["thread-unarchive", "--thread-id", "t-a"])
+        self.assertEqual(seen["provider"], "sub2api")
+        self.assertEqual(sent["status"], 200)
+        self.assertEqual(sent["body"]["thread_id"], "t-a")
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/docs/thread-resolve-fix.md b/docs/thread-resolve-fix.md
index b97e82d..1ed5e83 100644
--- a/docs/thread-resolve-fix.md
+++ b/docs/thread-resolve-fix.md
@@ -61,3 +61,24 @@
 - 新测试 9 个：`cloud/tests/test_thread_resolve.py`
   （CLI 参数位置、共享 home 读取、回退顺序、空→404、
   host.py 失败→502）。
+
+## 后续：unarchive 归档解析
+
+探针 probe9 发现：thread/archive 200 后 thread/unarchive
+稳定 404。根因是 #103 时代的逻辑 bug：unarchive 走普通
+解析，普通 thread-list 不传 --archived 时只回非归档
+thread，刚归档的 thread 永远解析不到。修法（只改服务端）：
+
+- `_list_task_threads(task, archived=False)`：archived 为真
+  时传 `--archived`，只列已归档 thread；home×provider 穷尽
+  回退不变。生产只读验证：同一 worktree 普通列表 0 条、
+  archived 列表恰好 1 条（即 probe9 归档的 thread），且其
+  archived 字段为 None。
+- `_resolve_task_thread(task, archived=False)` 与
+  `_pick_latest_thread(threads, include_archived=False)`：
+  归档模式下不跳过显式 archived 条目。
+- `_task_thread_mutate(..., resolve_archived=False)`：只供
+  unarchive；rename/archive/compact 仍走非归档解析。
+- 新测试 4 个：`cloud/tests/test_thread_unarchive.py`
+  （--archived 透传、普通解析 404 而归档解析命中、pick
+  归档开关、unarchive 调 CLI 时解析模式与 provider 正确）。