diff --git a/src/backend/api/routes/topics.py b/src/backend/api/routes/topics.py
index 1985e67..12034b5 100644
--- a/src/backend/api/routes/topics.py
+++ b/src/backend/api/routes/topics.py
@@ -9,8 +9,10 @@ from src.backend.db.database import (
     get_topic,
     update_topic,
     delete_topic,
+    list_requests,
 )
 from src.backend.models.api import TopicCreate, TopicUpdate, ok, fail
+from src.backend.services.worker_client import WorkerClient
 
 router = APIRouter(
     prefix="/topics",
@@ -91,3 +93,38 @@ async def delete(topic_id: str, db=Depends(_get_db)):
             content=fail("NOT_FOUND", "Topic not found or has active requests"),
         )
     return ok({"deleted": True})
+
+
+@router.post("/{topic_id}/summarize", summary="Regenerate topic summary")
+async def summarize_topic(topic_id: str, db=Depends(_get_db)):
+    topic = await get_topic(db, topic_id)
+    if not topic:
+        return JSONResponse(
+            status_code=404,
+            content=fail("NOT_FOUND", "Topic not found"),
+        )
+
+    completed = await list_requests(db, status="completed", topic_id=topic_id)
+    if not completed:
+        return JSONResponse(
+            status_code=400,
+            content=fail("NO_DATA", "No completed requests to summarize"),
+        )
+
+    exchanges = [
+        {"prompt": r["prompt"], "result": r["result"]}
+        for r in completed
+        if r["result"]
+    ]
+
+    worker = WorkerClient()
+    result = await worker.summarize(exchanges=exchanges, mode="complete")
+
+    if not result.get("success"):
+        return JSONResponse(
+            status_code=502,
+            content=fail("WORKER_ERROR", "Worker failed to generate summary"),
+        )
+
+    updated = await update_topic(db, topic_id, summary=result["summary"])
+    return ok(updated)
diff --git a/tests/test_api_topics.py b/tests/test_api_topics.py
index 2d4a87e..f80d580 100644
--- a/tests/test_api_topics.py
+++ b/tests/test_api_topics.py
@@ -148,3 +148,58 @@ async def test_delete_topic(client):
 
     resp = await client.get(f"/api/topics/{topic_id}")
     assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_summarize_topic(client):
+    create_resp = await client.post(
+        "/api/topics",
+        json={"name": "summarize-test", "system_prompt": "You help."},
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    from src.backend.db.database import get_db, create_request, complete_request
+
+    db = await get_db()
+    try:
+        req1 = await create_request(db, "Question 1", topic_id)
+        await complete_request(db, req1["id"], "Answer 1")
+        req2 = await create_request(db, "Question 2", topic_id)
+        await complete_request(db, req2["id"], "Answer 2")
+    finally:
+        await db.close()
+
+    from unittest.mock import patch, AsyncMock, MagicMock
+
+    mock_worker = MagicMock()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {
+        "success": True,
+        "summary": "Comprehensive summary of all exchanges.",
+    }
+
+    mock_client = AsyncMock()
+    mock_client.post.return_value = mock_response
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with patch("src.backend.services.worker_client.httpx.AsyncClient", return_value=mock_client):
+        resp = await client.post(f"/api/topics/{topic_id}/summarize")
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["success"] is True
+    assert "summary" in data["data"]
+
+
+@pytest.mark.asyncio
+async def test_summarize_topic_no_requests(client):
+    create_resp = await client.post(
+        "/api/topics",
+        json={"name": "empty-topic", "system_prompt": "Empty."},
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    resp = await client.post(f"/api/topics/{topic_id}/summarize")
+    assert resp.status_code == 400