diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChanged.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChanged.kt
index bd038c11f3..2d1638f48a 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChanged.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChanged.kt
@@ -29,10 +29,14 @@ object FiltersChanged {
     ): Boolean {
         if (oldFilters.size != newFilters.size) return true
 
-        oldFilters.forEachIndexed { index, oldFilter ->
-            val newFilter = newFilters.getOrNull(index) ?: return true
-
-            return needsToResendRequest(oldFilter, newFilter)
+        // Every filter must be compared. This used to be a forEachIndexed whose body
+        // `return`ed on the first iteration — a non-local return from this function — so
+        // only filters[0] was ever checked and a subscription whose first filter happened
+        // to be unchanged reported "no resend needed" however much the rest had changed,
+        // leaving the relay serving a stale filter set.
+        // Indexing is safe: the sizes were just proven equal.
+        for (i in oldFilters.indices) {
+            if (needsToResendRequest(oldFilters[i], newFilters[i])) return true
         }
         return false
     }
diff --git a/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChangedTest.kt b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChangedTest.kt
new file mode 100644
index 0000000000..4d6af28c2b
--- /dev/null
+++ b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/relay/client/pool/FiltersChangedTest.kt
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip01Core.relay.client.pool
+
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class FiltersChangedTest {
+    private fun authors(vararg a: String) = Filter(authors = a.toList())
+
+    @Test
+    fun emptyListsAreUnchanged() {
+        assertFalse(FiltersChanged.needsToResendRequest(emptyList(), emptyList()))
+    }
+
+    @Test
+    fun differentSizesNeedResend() {
+        assertTrue(FiltersChanged.needsToResendRequest(listOf(authors("a")), listOf(authors("a"), authors("b"))))
+    }
+
+    @Test
+    fun identicalSingleFilterDoesNotNeedResend() {
+        assertFalse(FiltersChanged.needsToResendRequest(listOf(authors("a")), listOf(authors("a"))))
+    }
+
+    @Test
+    fun changedFirstFilterNeedsResend() {
+        assertTrue(FiltersChanged.needsToResendRequest(listOf(authors("a")), listOf(authors("b"))))
+    }
+
+    /**
+     * Regression: the loop used a non-local `return` on the first iteration, so only
+     * filters[0] was ever compared. A subscription whose first filter was unchanged
+     * reported "no resend needed" no matter what happened to the rest, and silently
+     * went stale — the relay kept serving the old filter set.
+     */
+    @Test
+    fun changedSecondFilterNeedsResend() {
+        val old = listOf(authors("a"), authors("b"))
+        val new = listOf(authors("a"), authors("CHANGED"))
+        assertTrue(FiltersChanged.needsToResendRequest(old, new))
+    }
+
+    @Test
+    fun changedLastOfManyNeedsResend() {
+        val old = listOf(authors("a"), authors("b"), authors("c"), authors("d"))
+        val new = listOf(authors("a"), authors("b"), authors("c"), authors("CHANGED"))
+        assertTrue(FiltersChanged.needsToResendRequest(old, new))
+    }
+
+    @Test
+    fun allIdenticalOfManyDoesNotNeedResend() {
+        val old = listOf(authors("a"), authors("b"), authors("c"))
+        val new = listOf(authors("a"), authors("b"), authors("c"))
+        assertFalse(FiltersChanged.needsToResendRequest(old, new))
+    }
+
+    /** `since` moving forward is deliberately NOT a resend trigger, on any index. */
+    @Test
+    fun sinceMovingForwardOnLaterFilterDoesNotNeedResend() {
+        val old = listOf(Filter(authors = listOf("a"), since = 100), Filter(authors = listOf("b"), since = 100))
+        val new = listOf(Filter(authors = listOf("a"), since = 100), Filter(authors = listOf("b"), since = 200))
+        assertFalse(FiltersChanged.needsToResendRequest(old, new))
+    }
+
+    /** ...but moving backwards in time is, including on a later filter. */
+    @Test
+    fun sinceMovingBackwardsOnLaterFilterNeedsResend() {
+        val old = listOf(Filter(authors = listOf("a"), since = 100), Filter(authors = listOf("b"), since = 200))
+        val new = listOf(Filter(authors = listOf("a"), since = 100), Filter(authors = listOf("b"), since = 100))
+        assertTrue(FiltersChanged.needsToResendRequest(old, new))
+    }
+}