From e2461d0159ed9014783555458bff76c7ce52adc0 Mon Sep 17 00:00:00 2001
From: yujiteshima <yuji.teshima@gmail.com>
Date: Fri, 2 Jan 2026 23:45:11 +0900
Subject: [PATCH] Make PREFETCH_DELAY configurable via
 Turbo.config.drive.prefetchDelay

Allow developers to customize the prefetch delay (default: 100ms) to
optimize for different use cases. For example, image galleries with
many linked items may benefit from a longer delay to avoid triggering
excessive prefetch requests during rapid cursor movement.

Usage:
  Turbo.config.drive.prefetchDelay = 300 // Set to 300ms

Fixes #1481
---
 src/core/config/drive.js         |  1 +
 src/core/drive/prefetch_cache.js | 10 ++++++----
 src/tests/unit/export_tests.js   | 13 +++++++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/core/config/drive.js b/src/core/config/drive.js
index e5710d589..25492f927 100644
--- a/src/core/config/drive.js
+++ b/src/core/config/drive.js
@@ -1,6 +1,7 @@
 export const drive = {
   enabled: true,
   progressBarDelay: 500,
+  prefetchDelay: 100,
   unvisitableExtensions: new Set(
     [
       ".7z", ".aac", ".apk", ".avi", ".bmp", ".bz2", ".css", ".csv", ".deb", ".dmg", ".doc",
diff --git a/src/core/drive/prefetch_cache.js b/src/core/drive/prefetch_cache.js
index cb29aa238..b3e4aff75 100644
--- a/src/core/drive/prefetch_cache.js
+++ b/src/core/drive/prefetch_cache.js
@@ -1,15 +1,17 @@
 import { LRUCache } from "../lru_cache"
 import { toCacheKey } from "../url"
-
-const PREFETCH_DELAY = 100
+import { config } from "../config"
 
 class PrefetchCache extends LRUCache {
   #prefetchTimeout = null
   #maxAges = {}
 
-  constructor(size = 1, prefetchDelay = PREFETCH_DELAY) {
+  constructor(size = 1) {
     super(size, toCacheKey)
-    this.prefetchDelay = prefetchDelay
+  }
+
+  get prefetchDelay() {
+    return config.drive.prefetchDelay
   }
 
   putLater(url, request, ttl) {
diff --git a/src/tests/unit/export_tests.js b/src/tests/unit/export_tests.js
index cb5fcb2ac..88e1f5539 100644
--- a/src/tests/unit/export_tests.js
+++ b/src/tests/unit/export_tests.js
@@ -44,6 +44,19 @@ test("Session interface", () => {
   assert.equal("off", config.forms.mode)
 })
 
+test("config.drive.prefetchDelay is configurable", () => {
+  const { config } = Turbo
+
+  assert.equal(100, config.drive.prefetchDelay)
+
+  config.drive.prefetchDelay = 200
+
+  assert.equal(200, config.drive.prefetchDelay)
+
+  // Reset to default
+  config.drive.prefetchDelay = 100
+})
+
 test("StreamActions interface", () => {
   assert.equal(typeof StreamActions, "object")
 })