feat(threads): paginate full history via summaries endpoint (#1022)

* feat(threads): add paginated summaries API and load full history

* fix(threads): address summaries review feedback

- validate summaries sort params and log gateway failures
- page frontend thread summaries without stale query keys or silent truncation
- export router modules and tighten thread list typing

Refs: 2901804166, 2901804176, 2901804179, 2901804180, 2901804183, 2901804187, 2901804191

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/src/gateway/app.py

@@ -15,6 +15,7 @@ from src.gateway.routers import (
     models,
     skills,
     suggestions,
+    threads,
     uploads,
 )
 
@@ -139,6 +140,10 @@ This gateway provides custom endpoints for models, MCP configuration, skills, an
                 "name": "channels",
                 "description": "Manage IM channel integrations (Feishu, Slack, Telegram)",
             },
+            {
+                "name": "threads",
+                "description": "Thread summary and list endpoints for lightweight UI loading",
+            },
             {
                 "name": "health",
                 "description": "Health check and system status endpoints",
@@ -176,6 +181,9 @@ This gateway provides custom endpoints for models, MCP configuration, skills, an
     # Channels API is mounted at /api/channels
     app.include_router(channels.router)
 
+    # Threads API is mounted at /api/threads
+    app.include_router(threads.router)
+
     @app.get("/health", tags=["health"])
     async def health_check() -> dict:
         """Health check endpoint.

backend/src/gateway/routers/__init__.py

@@ -1,3 +1,14 @@
-from . import artifacts, mcp, models, skills, suggestions, uploads
+from . import agents, artifacts, channels, mcp, memory, models, skills, suggestions, threads, uploads
 
-__all__ = ["artifacts", "mcp", "models", "skills", "suggestions", "uploads"]
+__all__ = [
+    "agents",
+    "artifacts",
+    "channels",
+    "mcp",
+    "memory",
+    "models",
+    "skills",
+    "suggestions",
+    "threads",
+    "uploads",
+]

backend/src/gateway/routers/threads.py

@@ -0,0 +1,123 @@
+from __future__ import annotations
+
+import logging
+from collections.abc import Mapping
+from typing import Any, Literal
+
+from fastapi import APIRouter, HTTPException, Query
+from pydantic import BaseModel, Field
+
+from src.config.app_config import get_app_config
+
+router = APIRouter(prefix="/api/threads", tags=["threads"])
+logger = logging.getLogger(__name__)
+
+SortBy = Literal["updated_at", "created_at"]
+SortOrder = Literal["desc", "asc"]
+
+
+class ThreadSummary(BaseModel):
+    """Lean thread payload for list UIs."""
+
+    thread_id: str
+    updated_at: str | None = None
+    values: dict[str, str] = Field(default_factory=dict)
+
+
+class ThreadSummariesResponse(BaseModel):
+    """Paginated summaries response."""
+
+    threads: list[ThreadSummary]
+    next_offset: int | None = None
+
+
+ThreadSummary.model_rebuild()
+ThreadSummariesResponse.model_rebuild()
+
+
+def _resolve_langgraph_url() -> str:
+    config = get_app_config()
+    extra = config.model_extra or {}
+    channels_cfg = extra.get("channels")
+    if isinstance(channels_cfg, Mapping):
+        langgraph_url = channels_cfg.get("langgraph_url")
+        if isinstance(langgraph_url, str) and langgraph_url.strip():
+            return langgraph_url
+    return "http://localhost:2024"
+
+
+def _pick_title(values: Any) -> str:
+    if isinstance(values, Mapping):
+        title = values.get("title")
+        if isinstance(title, str) and title.strip():
+            return title
+    return "Untitled"
+
+
+def _to_thread_summary(raw: Any) -> ThreadSummary | None:
+    if not isinstance(raw, Mapping):
+        return None
+    thread_id = raw.get("thread_id")
+    if not isinstance(thread_id, str) or not thread_id.strip():
+        return None
+    updated_at = raw.get("updated_at")
+    return ThreadSummary(
+        thread_id=thread_id,
+        updated_at=updated_at if isinstance(updated_at, str) else None,
+        values={"title": _pick_title(raw.get("values"))},
+    )
+
+
+@router.get(
+    "/summaries",
+    response_model=ThreadSummariesResponse,
+    summary="List Thread Summaries",
+    description="Return paginated thread summaries for list UIs with minimal payload.",
+)
+async def list_thread_summaries(
+    limit: int = Query(default=50, ge=1, le=200),
+    offset: int = Query(default=0, ge=0),
+    sort_by: SortBy = Query(default="updated_at"),
+    sort_order: SortOrder = Query(default="desc"),
+) -> ThreadSummariesResponse:
+    """Fetch thread list from LangGraph and return compact title-only summaries."""
+
+    try:
+        from langgraph_sdk import get_client
+
+        client = get_client(url=_resolve_langgraph_url())
+        rows = await client.threads.search(
+            {
+                "limit": limit,
+                "offset": offset,
+                "sortBy": sort_by,
+                "sortOrder": sort_order,
+                "select": ["thread_id", "updated_at", "values"],
+            }
+        )
+    except Exception as e:
+        logger.exception("Failed to query LangGraph thread summaries")
+        raise HTTPException(status_code=502, detail=f"Failed to query LangGraph threads: {e}") from e
+
+    summaries: list[ThreadSummary] = []
+    row_count = 0
+    if isinstance(rows, list):
+        row_count = len(rows)
+        for row in rows:
+            summary = _to_thread_summary(row)
+            if summary is not None:
+                summaries.append(summary)
+
+    next_offset = offset + row_count if row_count >= limit else None
+    return ThreadSummariesResponse(threads=summaries, next_offset=next_offset)
+
+
+__all__ = [
+    "ThreadSummary",
+    "ThreadSummariesResponse",
+    "list_thread_summaries",
+    "_pick_title",
+    "_resolve_langgraph_url",
+    "_to_thread_summary",
+    "router",
+]

backend/tests/test_threads_router.py

@@ -0,0 +1,120 @@
+import asyncio
+import importlib.util
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+
+_MODULE_PATH = Path(__file__).resolve().parents[1] / "src" / "gateway" / "routers" / "threads.py"
+_SPEC = importlib.util.spec_from_file_location("deerflow_threads_router", _MODULE_PATH)
+assert _SPEC and _SPEC.loader
+threads = importlib.util.module_from_spec(_SPEC)
+_SPEC.loader.exec_module(threads)
+
+
+def test_pick_title_prefers_values_title():
+    assert threads._pick_title({"title": "  Hello Title  "}) == "  Hello Title  "
+
+
+def test_pick_title_falls_back_to_untitled():
+    assert threads._pick_title({}) == "Untitled"
+    assert threads._pick_title({"title": ""}) == "Untitled"
+    assert threads._pick_title(None) == "Untitled"
+
+
+def test_to_thread_summary_returns_compact_payload():
+    row = {
+        "thread_id": "t-1",
+        "updated_at": "2026-03-08T00:00:00Z",
+        "values": {
+            "title": "Roadmap",
+            "messages": ["very", "large", "content"],
+        },
+        "other": "ignored",
+    }
+    summary = threads._to_thread_summary(row)
+    assert summary is not None
+    assert summary.thread_id == "t-1"
+    assert summary.updated_at == "2026-03-08T00:00:00Z"
+    assert summary.values == {"title": "Roadmap"}
+
+
+def test_to_thread_summary_rejects_missing_thread_id():
+    assert threads._to_thread_summary({"updated_at": "x"}) is None
+    assert threads._to_thread_summary({"thread_id": ""}) is None
+
+
+def test_resolve_langgraph_url_prefers_channels_config(monkeypatch):
+    fake_cfg = SimpleNamespace(model_extra={"channels": {"langgraph_url": "http://langgraph.internal:2024"}})
+    monkeypatch.setattr(threads, "get_app_config", lambda: fake_cfg)
+    assert threads._resolve_langgraph_url() == "http://langgraph.internal:2024"
+
+
+def test_resolve_langgraph_url_falls_back_default(monkeypatch):
+    fake_cfg = SimpleNamespace(model_extra={})
+    monkeypatch.setattr(threads, "get_app_config", lambda: fake_cfg)
+    assert threads._resolve_langgraph_url() == "http://localhost:2024"
+
+
+def test_list_thread_summaries_uses_row_count_for_next_offset(monkeypatch):
+    fake_cfg = SimpleNamespace(model_extra={})
+    monkeypatch.setattr(threads, "get_app_config", lambda: fake_cfg)
+
+    rows = [
+        {
+            "thread_id": "t-1",
+            "updated_at": "2026-03-08T00:00:00Z",
+            "values": {"title": "Roadmap"},
+        },
+        {
+            "thread_id": "",
+            "updated_at": "2026-03-08T00:01:00Z",
+            "values": {"title": "Broken row"},
+        },
+    ]
+
+    class FakeThreadsClient:
+        async def search(self, payload):
+            assert payload["limit"] == 2
+            assert payload["offset"] == 4
+            assert payload["sortBy"] == "updated_at"
+            assert payload["sortOrder"] == "desc"
+            return rows
+
+    class FakeClient:
+        threads = FakeThreadsClient()
+
+    fake_module = SimpleNamespace(get_client=lambda url: FakeClient())
+    monkeypatch.setitem(sys.modules, "langgraph_sdk", fake_module)
+
+    response = asyncio.run(threads.list_thread_summaries(limit=2, offset=4, sort_by="updated_at", sort_order="desc"))
+
+    assert [summary.thread_id for summary in response.threads] == ["t-1"]
+    assert response.next_offset == 6
+
+
+def test_list_thread_summaries_returns_none_when_last_page(monkeypatch):
+    fake_cfg = SimpleNamespace(model_extra={})
+    monkeypatch.setattr(threads, "get_app_config", lambda: fake_cfg)
+
+    rows = [
+        {
+            "thread_id": "t-1",
+            "updated_at": "2026-03-08T00:00:00Z",
+            "values": {"title": "Roadmap"},
+        }
+    ]
+
+    class FakeThreadsClient:
+        async def search(self, payload):
+            assert payload["limit"] == 2
+            return rows
+
+    class FakeClient:
+        threads = FakeThreadsClient()
+
+    fake_module = SimpleNamespace(get_client=lambda url: FakeClient())
+    monkeypatch.setitem(sys.modules, "langgraph_sdk", fake_module)
+
+    response = asyncio.run(threads.list_thread_summaries(limit=2, offset=0, sort_by="updated_at", sort_order="desc"))
+
+    assert response.next_offset is None

frontend/src/core/threads/hooks.ts

@@ -1,5 +1,4 @@
 import type { AIMessage, Message } from "@langchain/langgraph-sdk";
-import type { ThreadsClient } from "@langchain/langgraph-sdk/client";
 import { useStream } from "@langchain/langgraph-sdk/react";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { useCallback, useEffect, useRef, useState } from "react";
@@ -8,6 +7,7 @@ import { toast } from "sonner";
 import type { PromptInputMessage } from "@/components/ai-elements/prompt-input";
 
 import { getAPIClient } from "../api";
+import { getBackendBaseURL } from "../config";
 import { useI18n } from "../i18n/hooks";
 import type { FileInMessage } from "../messages/utils";
 import type { LocalSettings } from "../settings";
@@ -15,7 +15,9 @@ import { useUpdateSubtask } from "../tasks/context";
 import type { UploadedFileInfo } from "../uploads";
 import { uploadFiles } from "../uploads";
 
-import type { AgentThread, AgentThreadState } from "./types";
+import type { AgentThreadState, ThreadListItem } from "./types";
+
+const THREADS_LIST_QUERY_KEY = ["threads", "search"] as const;
 
 export type ToolEndEvent = {
   name: string;
@@ -110,10 +112,10 @@ export function useThreadStream({
         if (update && "title" in update && update.title) {
           void queryClient.setQueriesData(
             {
-              queryKey: ["threads", "search"],
+              queryKey: THREADS_LIST_QUERY_KEY,
               exact: false,
             },
-            (oldData: Array<AgentThread> | undefined) => {
+            (oldData: Array<ThreadListItem> | undefined) => {
               return oldData?.map((t) => {
                 if (t.thread_id === threadIdRef.current) {
                   return {
@@ -148,7 +150,7 @@ export function useThreadStream({
     },
     onFinish(state) {
       listeners.current.onFinish?.(state.values);
-      void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
+      void queryClient.invalidateQueries({ queryKey: THREADS_LIST_QUERY_KEY });
     },
   });
 
@@ -338,7 +340,7 @@ export function useThreadStream({
             },
           },
         );
-        void queryClient.invalidateQueries({ queryKey: ["threads", "search"] });
+        void queryClient.invalidateQueries({ queryKey: THREADS_LIST_QUERY_KEY });
       } catch (error) {
         setOptimisticMessages([]);
         throw error;
@@ -359,20 +361,90 @@ export function useThreadStream({
   return [mergedThread, sendMessage] as const;
 }
 
+
+type ThreadSummaryApiResponse = {
+  threads: ThreadListItem[];
+  next_offset: number | null;
+};
+
+type ThreadListQueryParams = {
+  limit?: number;
+  offset?: number;
+  sortBy?: "updated_at" | "created_at";
+  sortOrder?: "asc" | "desc";
+};
+
+async function fetchThreadSummariesPage(
+  params: Required<ThreadListQueryParams>,
+): Promise<ThreadSummaryApiResponse> {
+  const baseURL = getBackendBaseURL();
+  const url = new URL(`${baseURL}/api/threads/summaries`,
+    typeof window !== "undefined" ? window.location.origin : "http://localhost:2026",
+  );
+  url.searchParams.set("limit", String(params.limit));
+  url.searchParams.set("offset", String(params.offset));
+  url.searchParams.set("sort_by", params.sortBy);
+  url.searchParams.set("sort_order", params.sortOrder);
+
+  const response = await fetch(url.toString());
+  if (!response.ok) {
+    throw new Error(`Failed to fetch thread summaries: ${response.status}`);
+  }
+  return (await response.json()) as ThreadSummaryApiResponse;
+}
+
 export function useThreads(
-  params: Parameters<ThreadsClient["search"]>[0] = {
+  params: ThreadListQueryParams = {
     limit: 50,
     sortBy: "updated_at",
     sortOrder: "desc",
-    select: ["thread_id", "updated_at", "values"],
   },
 ) {
-  const apiClient = getAPIClient();
+  const pageSize = params.limit ?? 50;
-  return useQuery<AgentThread[]>({
+  const initialOffset = params.offset ?? 0;
-    queryKey: ["threads", "search", params],
+  const sortBy = params.sortBy ?? "updated_at";
+  const sortOrder = params.sortOrder ?? "desc";
+
+  return useQuery<ThreadListItem[]>({
+    queryKey: [...THREADS_LIST_QUERY_KEY, pageSize, initialOffset, sortBy, sortOrder],
     queryFn: async () => {
-      const response = await apiClient.threads.search<AgentThreadState>(params);
+      const allThreads: ThreadListItem[] = [];
-      return response as AgentThread[];
+      let offset = initialOffset;
+      const seenOffsets = new Set<number>();
+
+      while (true) {
+        if (seenOffsets.has(offset)) {
+          throw new Error(`Detected repeated thread summaries offset: ${offset}`);
+        }
+        seenOffsets.add(offset);
+
+        const page = await fetchThreadSummariesPage({
+          limit: pageSize,
+          offset,
+          sortBy,
+          sortOrder,
+        });
+
+        if (!Array.isArray(page.threads) || page.threads.length === 0) {
+          break;
+        }
+
+        allThreads.push(...page.threads);
+
+        if (page.next_offset == null) {
+          break;
+        }
+
+        if (page.next_offset <= offset) {
+          throw new Error(
+            `Thread summaries pagination did not advance: ${page.next_offset}`,
+          );
+        }
+
+        offset = page.next_offset;
+      }
+
+      return allThreads;
     },
     refetchOnWindowFocus: false,
   });
@@ -388,11 +460,11 @@ export function useDeleteThread() {
     onSuccess(_, { threadId }) {
       queryClient.setQueriesData(
         {
-          queryKey: ["threads", "search"],
+          queryKey: THREADS_LIST_QUERY_KEY,
           exact: false,
         },
-        (oldData: Array<AgentThread>) => {
+        (oldData: Array<ThreadListItem> | undefined) => {
-          return oldData.filter((t) => t.thread_id !== threadId);
+          return oldData?.filter((t) => t.thread_id !== threadId) ?? oldData;
         },
       );
     },
@@ -417,11 +489,11 @@ export function useRenameThread() {
     onSuccess(_, { threadId, title }) {
       queryClient.setQueriesData(
         {
-          queryKey: ["threads", "search"],
+          queryKey: THREADS_LIST_QUERY_KEY,
           exact: false,
         },
-        (oldData: Array<AgentThread>) => {
+        (oldData: Array<ThreadListItem> | undefined) => {
-          return oldData.map((t) => {
+          return oldData?.map((t) => {
             if (t.thread_id === threadId) {
               return {
                 ...t,
@@ -432,7 +504,7 @@ export function useRenameThread() {
               };
             }
             return t;
-          });
+          }) ?? oldData;
         },
       );
     },

frontend/src/core/threads/types.ts

@@ -11,6 +11,10 @@ export interface AgentThreadState extends Record<string, unknown> {
 
 export interface AgentThread extends Thread<AgentThreadState> {}
 
+export type ThreadListItem = Pick<AgentThread, "thread_id" | "updated_at"> & {
+  values: Pick<AgentThreadState, "title">;
+};
+
 export interface AgentThreadContext extends Record<string, unknown> {
   thread_id: string;
   model_name: string | undefined;

frontend/src/core/threads/utils.ts

@@ -1,6 +1,5 @@
 import type { Message } from "@langchain/langgraph-sdk";
 
-import type { AgentThread } from "./types";
 
 export function pathOfThread(threadId: string) {
   return `/workspace/chats/${threadId}`;
@@ -19,6 +18,6 @@ export function textOfMessage(message: Message) {
   return null;
 }
 
-export function titleOfThread(thread: AgentThread) {
+export function titleOfThread(thread: { values?: { title?: string | null } | null }) {
   return thread.values?.title ?? "Untitled";
 }