diff --git a/.changeset/fix-lru-ios18.md b/.changeset/fix-lru-ios18.md
new file mode 100644
index 0000000000..c07ee58c5b
--- /dev/null
+++ b/.changeset/fix-lru-ios18.md
@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Fixed unbounded LRU cache growth on iOS 18+.
diff --git a/src/utils/lru.test.ts b/src/utils/lru.test.ts
index 2449644863..d0311df0b9 100644
--- a/src/utils/lru.test.ts
+++ b/src/utils/lru.test.ts
@@ -20,6 +20,42 @@ test('default', () => {
   expect(cache.get('g')).toBe(7)
 })
 
+test('eviction does not exceed maxSize under heavy load', () => {
+  const cache = new LruMap<boolean>(100)
+  for (let i = 0; i < 10_000; i++) {
+    cache.set(`key${i}`, true)
+  }
+  expect(cache.size).toBe(100)
+  expect(cache.has('key0')).toBe(false)
+  expect(cache.has('key9999')).toBe(true)
+  expect(cache.has('key9900')).toBe(true)
+  expect(cache.has('key9899')).toBe(false)
+})
+
+test('set existing key refreshes its position', () => {
+  const cache = new LruMap(3)
+  cache.set('a', 1)
+  cache.set('b', 2)
+  cache.set('c', 3)
+  // Refresh 'a' by re-setting it
+  cache.set('a', 10)
+  // Now 'b' is the oldest
+  cache.set('d', 4)
+  expect(cache.has('a')).toBe(true)
+  expect(cache.get('a')).toBe(10)
+  expect(cache.has('b')).toBe(false)
+  expect(cache.has('c')).toBe(true)
+  expect(cache.has('d')).toBe(true)
+})
+
+test('evicts empty-string key correctly', () => {
+  const cache = new LruMap<number>(1)
+  cache.set('', 1)
+  cache.set('x', 2)
+  expect(cache.has('')).toBe(false)
+  expect(cache.has('x')).toBe(true)
+})
+
 test('update touched keys', () => {
   const cache = new LruMap(5)
   cache.set('a', 1)
diff --git a/src/utils/lru.ts b/src/utils/lru.ts
index bc52c0de47..4d884e6b08 100644
--- a/src/utils/lru.ts
+++ b/src/utils/lru.ts
@@ -14,19 +14,20 @@ export class LruMap<value = unknown> extends Map<string, value> {
   override get(key: string) {
     const value = super.get(key)
 
-    if (super.has(key) && value !== undefined) {
-      this.delete(key)
-      super.set(key, value)
+    if (super.has(key)) {
+      super.delete(key)
+      super.set(key, value as value)
     }
 
     return value
   }
 
   override set(key: string, value: value) {
+    if (super.has(key)) super.delete(key)
     super.set(key, value)
     if (this.maxSize && this.size > this.maxSize) {
-      const firstKey = this.keys().next().value
-      if (firstKey) this.delete(firstKey)
+      const firstKey = super.keys().next().value
+      if (firstKey !== undefined) super.delete(firstKey)
     }
     return this
   }