fix: load paginated run history messages (#3305)

backend/app/gateway/pagination.py

@@ -0,0 +1,15 @@
+"""Shared pagination helpers for gateway routers."""
+
+from __future__ import annotations
+
+
+def trim_run_message_page(rows: list[dict], *, limit: int, after_seq: int | None) -> tuple[list[dict], bool]:
+    """Trim a ``limit + 1`` run-message page while preserving page boundaries."""
+    has_more = len(rows) > limit
+    if not has_more:
+        return rows, False
+
+    if after_seq is not None:
+        return rows[:limit], True
+
+    return rows[-limit:], True

backend/app/gateway/routers/runs.py

@@ -15,6 +15,7 @@ from fastapi.responses import StreamingResponse
 
 from app.gateway.authz import require_permission
 from app.gateway.deps import get_checkpointer, get_feedback_repo, get_run_event_store, get_run_manager, get_run_store, get_stream_bridge
+from app.gateway.pagination import trim_run_message_page
 from app.gateway.routers.thread_runs import RunCreateRequest
 from app.gateway.services import sse_consumer, start_run, wait_for_run_completion
 from deerflow.runtime import serialize_channel_values
@@ -129,8 +130,7 @@ async def run_messages(
         before_seq=before_seq,
         after_seq=after_seq,
     )
-    has_more = len(rows) > limit
-    data = rows[:limit] if has_more else rows
+    data, has_more = trim_run_message_page(rows, limit=limit, after_seq=after_seq)
     return {"data": data, "has_more": has_more}
 
 

backend/app/gateway/routers/thread_runs.py

@@ -21,6 +21,7 @@ from pydantic import BaseModel, Field
 
 from app.gateway.authz import require_permission
 from app.gateway.deps import get_checkpointer, get_current_user, get_feedback_repo, get_run_event_store, get_run_manager, get_run_store, get_stream_bridge
+from app.gateway.pagination import trim_run_message_page
 from app.gateway.services import sse_consumer, start_run, wait_for_run_completion
 from deerflow.runtime import RunRecord, RunStatus, serialize_channel_values
 
@@ -402,8 +403,7 @@ async def list_run_messages(
         before_seq=before_seq,
         after_seq=after_seq,
     )
-    has_more = len(rows) > limit
-    data = rows[:limit] if has_more else rows
+    data, has_more = trim_run_message_page(rows, limit=limit, after_seq=after_seq)
     return {"data": data, "has_more": has_more}