From 9681761cdf93e2a95848440279a8ad861160c88d Mon Sep 17 00:00:00 2001
From: Frank Song <franksong2702@gmail.com>
Date: Thu, 14 May 2026 08:47:04 +0800
Subject: [PATCH] fix: cap _summary_cache with OrderedDict LRU

Refs #2215 Fix A: replace plain dict _summary_cache with OrderedDict-based LRU capped at 16 entries to prevent unbounded memory growth from long-running update summary generations.

Add regression coverage for the bounded LRU behavior: cache hits refresh recency, a new entry at capacity evicts the least-recently used key, and cache size never exceeds the cap.
---
 api/updates.py                    |  8 +++++-
 tests/test_update_banner_fixes.py | 46 ++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/api/updates.py b/api/updates.py
index 0bbca829..b91fafe1 100644
--- a/api/updates.py
+++ b/api/updates.py
@@ -14,6 +14,7 @@ import re
 import subprocess
 import threading
 import time
+from collections import OrderedDict
 from pathlib import Path
 from urllib.parse import urlparse
 
@@ -26,7 +27,8 @@ except ImportError:
     _AGENT_DIR = None
 
 _update_cache = {'webui': None, 'agent': None, 'checked_at': 0}
-_summary_cache = {}
+_SUMMARY_CACHE_MAX = 16
+_summary_cache: OrderedDict = OrderedDict()
 _cache_lock = threading.Lock()
 _check_in_progress = False
 _apply_lock = threading.Lock()   # prevents concurrent stash/pull/pop on same repo
@@ -498,6 +500,8 @@ def summarize_update_payload(updates: dict, llm_callback=None, *, target: str |
     if use_cache:
         with _cache_lock:
             cached = _summary_cache.get(cache_key)
+            if cached:
+                _summary_cache.move_to_end(cache_key)
         if cached:
             result = dict(cached)
             result['cached'] = True
@@ -526,6 +530,8 @@ def summarize_update_payload(updates: dict, llm_callback=None, *, target: str |
     }
     if use_cache:
         with _cache_lock:
+            if len(_summary_cache) >= _SUMMARY_CACHE_MAX and cache_key not in _summary_cache:
+                _summary_cache.popitem(last=False)
             _summary_cache[cache_key] = dict(result)
     return result
 
diff --git a/tests/test_update_banner_fixes.py b/tests/test_update_banner_fixes.py
index de46a892..c5f541be 100644
--- a/tests/test_update_banner_fixes.py
+++ b/tests/test_update_banner_fixes.py
@@ -839,6 +839,51 @@ class TestWhatsNewSummaryToggle:
         assert second['summary'] == first['summary']
         assert second['cached'] is True
         assert changed['summary'] != first['summary']
+
+    def test_update_summary_cache_is_bounded_lru(self):
+        import api.updates as upd
+
+        upd._summary_cache.clear()
+        calls = []
+
+        def payload(n):
+            return {
+                'webui': {
+                    'behind': n + 1,
+                    'current_sha': f'old-{n}',
+                    'latest_sha': f'new-{n}',
+                    'compare_url': f'https://example.test/webui/{n}',
+                },
+            }
+
+        def fake_llm(_system, prompt):
+            calls.append(prompt)
+            return f'- Generated summary #{len(calls)}'
+
+        try:
+            for i in range(upd._SUMMARY_CACHE_MAX):
+                upd.summarize_update_payload(payload(i), llm_callback=fake_llm)
+
+            assert len(upd._summary_cache) == upd._SUMMARY_CACHE_MAX
+            assert len(calls) == upd._SUMMARY_CACHE_MAX
+
+            first_again = upd.summarize_update_payload(payload(0), llm_callback=fake_llm)
+            assert first_again['cached'] is True
+            assert len(calls) == upd._SUMMARY_CACHE_MAX
+
+            upd.summarize_update_payload(payload(upd._SUMMARY_CACHE_MAX), llm_callback=fake_llm)
+            assert len(upd._summary_cache) == upd._SUMMARY_CACHE_MAX
+
+            still_cached = upd.summarize_update_payload(payload(0), llm_callback=fake_llm)
+            assert still_cached['cached'] is True
+            assert len(calls) == upd._SUMMARY_CACHE_MAX + 1
+
+            evicted = upd.summarize_update_payload(payload(1), llm_callback=fake_llm)
+            assert evicted['cached'] is False
+            assert len(calls) == upd._SUMMARY_CACHE_MAX + 2
+        finally:
+            upd._summary_cache.clear()
+
     def test_update_summary_can_be_generated_per_target_and_cached_separately(self):
         import api.updates as upd
 
@@ -932,4 +977,3 @@ class TestCheckForUpdatesButton:
         assert count >= 5, (
             f"settings_check_now found in only {count} locale blocks (expected ≥5: en, ru, es, zh, zh-Hant)"
         )
-