diff --git a/app/src/main/java/com/bitchat/android/nostr/NostrCrypto.kt b/app/src/main/java/com/bitchat/android/nostr/NostrCrypto.kt
index 972b90fa..cab41ad0 100644
--- a/app/src/main/java/com/bitchat/android/nostr/NostrCrypto.kt
+++ b/app/src/main/java/com/bitchat/android/nostr/NostrCrypto.kt
@@ -21,7 +21,9 @@ import java.math.BigInteger
  * Includes secp256k1 operations, ECDH, and NIP-44 encryption
  */
 object NostrCrypto {
-    
+
+    internal const val NIP17_DEFAULT_MAX_PAST_SECONDS = 85_500
+
     private val secureRandom = SecureRandom()
     // NIP-44 v2 only
     
@@ -317,9 +319,9 @@ object NostrCrypto {
     }
     
     /**
-     * Random timestamp up to maxPastSeconds in the past (default 24 hours for iOS compatibility)
+     * Random timestamp in the past, defaulting to 23h45m to leave slack inside iOS's 24h lookback.
      */
-    fun randomizeTimestampUpToPast(maxPastSeconds: Int = 86400): Int {
+    fun randomizeTimestampUpToPast(maxPastSeconds: Int = NIP17_DEFAULT_MAX_PAST_SECONDS): Int {
         val now = (System.currentTimeMillis() / 1000).toInt()
         val offset = if (maxPastSeconds > 0) secureRandom.nextInt(maxPastSeconds + 1) else 0
         return now - offset
diff --git a/app/src/main/java/com/bitchat/android/nostr/NostrProtocol.kt b/app/src/main/java/com/bitchat/android/nostr/NostrProtocol.kt
index 926ea493..42caefec 100644
--- a/app/src/main/java/com/bitchat/android/nostr/NostrProtocol.kt
+++ b/app/src/main/java/com/bitchat/android/nostr/NostrProtocol.kt
@@ -37,7 +37,7 @@ object NostrProtocol {
         val rumorId = rumorBase.computeEventIdHex()
         val rumor = rumorBase.copy(id = rumorId)
         
-        // 2. Seal the rumor (kind 13) signed by sender, timestamp randomized within iOS's 24h lookback
+        // 2. Seal the rumor with 15 minutes of slack inside iOS's 24-hour lookback.
         val sealedEvent = createSeal(
             rumor = rumor,
             recipientPubkey = recipientPubkey,
diff --git a/app/src/test/kotlin/com/bitchat/android/nostr/NostrProtocolTest.kt b/app/src/test/kotlin/com/bitchat/android/nostr/NostrProtocolTest.kt
index 3ef73733..29a41f6e 100644
--- a/app/src/test/kotlin/com/bitchat/android/nostr/NostrProtocolTest.kt
+++ b/app/src/test/kotlin/com/bitchat/android/nostr/NostrProtocolTest.kt
@@ -43,10 +43,15 @@ class NostrProtocolTest {
     }
 
     @Test
-    fun createPrivateMessage_limitsEnvelopeTimestampsToIosLookback() {
+    fun createPrivateMessage_reservesSlackInsideIosLookback() {
         val sender = NostrIdentity.generate()
         val recipient = NostrIdentity.generate()
 
+        assertEquals(
+            IOS_DM_LOOKBACK_SECONDS - TIMESTAMP_SAFETY_SLACK_SECONDS,
+            NostrCrypto.NIP17_DEFAULT_MAX_PAST_SECONDS
+        )
+
         repeat(20) {
             val beforeCreation = (System.currentTimeMillis() / 1000).toInt()
             val giftWrap = NostrProtocol.createPrivateMessage(
@@ -74,8 +79,8 @@ class NostrProtocolTest {
         afterCreation: Int
     ) {
         assertTrue(
-            "$envelope timestamp must be no more than 24 hours old",
-            createdAt >= beforeCreation - IOS_DM_LOOKBACK_SECONDS
+            "$envelope timestamp must leave 15 minutes inside the iOS lookback",
+            createdAt >= beforeCreation - MAX_OUTBOUND_BACKDATE_SECONDS
         )
         assertTrue(
             "$envelope timestamp must not be in the future",
@@ -126,6 +131,9 @@ class NostrProtocolTest {
     }
 
     private companion object {
-        const val IOS_DM_LOOKBACK_SECONDS = 86400
+        const val IOS_DM_LOOKBACK_SECONDS = 86_400
+        const val TIMESTAMP_SAFETY_SLACK_SECONDS = 900
+        const val MAX_OUTBOUND_BACKDATE_SECONDS =
+            IOS_DM_LOOKBACK_SECONDS - TIMESTAMP_SAFETY_SLACK_SECONDS
     }
 }
diff --git a/docs/client-rewrite-contracts.md b/docs/client-rewrite-contracts.md
index 1da0e33a..ed92ab79 100644
--- a/docs/client-rewrite-contracts.md
+++ b/docs/client-rewrite-contracts.md
@@ -17,7 +17,7 @@ The remaining implementation work and milestone progress are tracked in
 | Inner payloads | Noise type bytes, private-message TLVs, peer-state TLVs, file-transfer TLVs, live-voice bursts, fragment header, sync request TLVs | `ClientRewriteWireContractTest`, `AuthenticatedPeerStateTest`, `PrivateMediaTransferPreparerTest`, `VoiceBurstPacketTest`, `FragmentManagerTest` |
 | Identity/security | Announcement extensions, capability bitfield endianness, Noise static-key binding, handshake identity binding, signatures | `IdentityAnnouncementTest`, `NoiseSessionManagerIdentityBindingTest`, `ClientRewritePrimitiveContractTest` |
 | Sync/routing | Stable packet IDs, GCS bitstream, replay collapse, TTL handling, relay choice, confirmed graph edges | `ClientRewritePrimitiveContractTest`, `GCSFilterTest`, `PacketRelayManagerTest`, `MeshGraphServiceTest`, `TransportBridgeServiceTest` |
-| Nostr | Bech32, secp256k1 key derivation, NIP-01 event IDs/signatures, NIP-44 authenticated encryption, NIP-13 PoW, authenticated NIP-17 seals, 24-hour outbound envelope randomization | `ClientRewriteNostrContractTest`, `NostrProtocolTest` |
+| Nostr | Bech32, secp256k1 key derivation, NIP-01 event IDs/signatures, NIP-44 authenticated encryption, NIP-13 PoW, authenticated NIP-17 seals, 23h45m outbound envelope randomization | `ClientRewriteNostrContractTest`, `NostrProtocolTest` |
 | Application state | Peer unions, canonical private conversations, chronological history, delivery/read behavior, media migration policy | `AppStateStoreTest`, `PrivateChatManagerTest`, `MediaSendingManagerMigrationTest` |
 
 ## Golden-vector policy
@@ -33,8 +33,8 @@ at least one literal vector.
 
 NIP-17 receivers must use a lookback at least as long as the maximum timestamp
 randomization used by senders. Android caps outbound seal and gift-wrap
-randomization at 24 hours for iOS interoperability while retaining its 48-hour
-receive lookback.
+randomization at 23h45m, leaving 15 minutes of slack inside iOS's 24-hour
+subscription window, while retaining its 48-hour receive lookback.
 
 ## Rewrite acceptance gate