From a9d177ee91d624c99a308eaf31ce488441c18eec Mon Sep 17 00:00:00 2001
From: pax <paxxe@protonmail.com>
Date: Sun, 5 Apr 2026 00:28:35 -0500
Subject: [PATCH] Throttle prefetch: only next+prev, 1s stagger, sequential

Reduced from 3 concurrent prefetches to 2 sequential with 1s
delay between them. Avoids hitting Danbooru's 10 req/s rate limit.
---
 booru_viewer/gui/app.py | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/booru_viewer/gui/app.py b/booru_viewer/gui/app.py
index c4d676f..81b4930 100644
--- a/booru_viewer/gui/app.py
+++ b/booru_viewer/gui/app.py
@@ -765,18 +765,18 @@ class BooruApp(QMainWindow):
             self._prefetch_adjacent(index)
 
     def _prefetch_adjacent(self, index: int) -> None:
-        """Silently download the next and previous posts in the background."""
-        for offset in (1, -1, 2):
-            adj = index + offset
-            if 0 <= adj < len(self._posts):
-                url = self._posts[adj].file_url
-                if url:
-                    async def _prefetch(u=url):
-                        try:
-                            await download_image(u)
-                        except Exception:
-                            pass
-                    self._run_async(_prefetch)
+        """Silently download adjacent posts with staggered delays."""
+        async def _prefetch_batch():
+            for i, offset in enumerate((1, -1)):
+                adj = index + offset
+                if 0 <= adj < len(self._posts) and self._posts[adj].file_url:
+                    if i > 0:
+                        await asyncio.sleep(1)
+                    try:
+                        await download_image(self._posts[adj].file_url)
+                    except Exception:
+                        pass
+        self._run_async(_prefetch_batch)
 
     def _on_download_progress(self, downloaded: int, total: int) -> None:
         if total > 0: