diff --git a/src/nostr/runtime.rs b/src/nostr/runtime.rs
index 355b6f8..11b1800 100644
--- a/src/nostr/runtime.rs
+++ b/src/nostr/runtime.rs
@@ -1223,6 +1223,16 @@ impl NostrRendezvous {
             }
         }
 
+        // Resolve the answer's relays before binding a socket and running STUN.
+        // Nothing in the relay choice depends on what STUN observes, and an offer
+        // from a peer we share no relay with cannot be answered at all — doing it
+        // in this order spends a STUN round trip, and holds an offer slot for its
+        // duration, only to discard the result.
+        let relays = self.preferred_signal_relays(sender, None).await?;
+        if relays.is_empty() {
+            return Err(BootstrapError::MissingRelays(offer.sender_npub.clone()));
+        }
+
         let base_socket = std::net::UdpSocket::bind(("0.0.0.0", 0))?;
         base_socket.set_nonblocking(true)?;
         let (reflexive_address, local_addresses, stun_server) = observe_traversal_addresses(
@@ -1257,7 +1267,6 @@ impl NostrRendezvous {
             (!accepted).then_some("no-usable-addresses".to_string()),
             Some(offer_received_at),
         );
-        let relays = self.preferred_signal_relays(sender, None).await?;
         let answer_event = self.send_signal(&relays, sender, &answer).await?;
         debug!(
             peer = %peer_short,
@@ -1384,22 +1393,21 @@ impl NostrRendezvous {
         target_pubkey: PublicKey,
         advert: Option<&OverlayAdvert>,
     ) -> Result<Vec<String>, BootstrapError> {
-        let mut merged = self.find_recipient_inbox_relays(target_pubkey).await?;
-        if let Some(advert) = advert
-            && let Some(relays) = advert.signal_relays.as_ref()
-        {
-            for relay in relays {
-                if !merged.contains(relay) {
-                    merged.push(relay.clone());
-                }
-            }
-        }
-        for relay in &self.config.dm_relays {
-            if !merged.contains(relay) {
-                merged.push(relay.clone());
-            }
-        }
-        Ok(merged)
+        let inbox = self.find_recipient_inbox_relays(target_pubkey).await?;
+        let pool: HashSet<RelayUrl> = self.client.pool().all_relays().await.into_keys().collect();
+        let usable = signal_relays(
+            &inbox,
+            advert.and_then(|advert| advert.signal_relays.as_deref()),
+            &self.config.dm_relays,
+            &pool,
+        );
+        debug!(
+            peer = %target_pubkey.to_bech32().map(|npub| short_npub(&npub)).unwrap_or_default(),
+            inbox = inbox.len(),
+            usable = usable.len(),
+            "traversal: signal relays resolved against the client pool"
+        );
+        Ok(usable)
     }
 
     async fn find_recipient_inbox_relays(
@@ -1599,6 +1607,56 @@ impl NostrRendezvous {
     }
 }
 
+/// Retain only the candidates the client pool actually holds.
+///
+/// `send_event_to` rejects the whole send with `RelayNotFound` if any single URL
+/// is outside the pool, so a signal addressed to a peer's advertised relays fails
+/// entirely on one relay we are not configured with. Filtering first turns that
+/// into a send to the relays we share.
+///
+/// Comparison is on the normalized `RelayUrl` rather than the raw string, because
+/// the pool is keyed that way: a candidate spelled `wss://relay.example/` matches
+/// a configured `wss://relay.example`. Order is preserved, candidates that fail
+/// to parse are dropped, and duplicates that normalize alike are collapsed.
+fn retain_pooled_relays(candidates: &[String], pool: &HashSet<RelayUrl>) -> Vec<String> {
+    let mut seen: HashSet<RelayUrl> = HashSet::new();
+    let mut usable = Vec::with_capacity(candidates.len());
+    for candidate in candidates {
+        let Ok(url) = RelayUrl::parse(candidate) else {
+            continue;
+        };
+        if pool.contains(&url) && seen.insert(url.clone()) {
+            usable.push(url.to_string());
+        }
+    }
+    usable
+}
+
+/// Choose the relays a traversal signal for one peer should be sent to.
+///
+/// The candidates are the peer's NIP-17 inbox relays, then the relays its advert
+/// nominates for signaling, then our own DM relays — remote-supplied first, ours
+/// last, so a peer's preference is honored where we can act on it. The result is
+/// whatever survives [`retain_pooled_relays`].
+///
+/// This is the whole decision, kept synchronous so it can be exercised without a
+/// relay client: the caller's only job is to supply the fetched inbox list and
+/// the pool.
+pub(super) fn signal_relays(
+    inbox: &[String],
+    advert_signal: Option<&[String]>,
+    dm_relays: &[String],
+    pool: &HashSet<RelayUrl>,
+) -> Vec<String> {
+    let mut merged: Vec<String> = inbox.to_vec();
+    for relay in advert_signal.unwrap_or_default().iter().chain(dm_relays) {
+        if !merged.contains(relay) {
+            merged.push(relay.clone());
+        }
+    }
+    retain_pooled_relays(&merged, pool)
+}
+
 #[cfg(test)]
 impl NostrRendezvous {
     /// Build a minimal `NostrRendezvous` for unit tests. No relay client is
diff --git a/src/nostr/tests.rs b/src/nostr/tests.rs
index 82609c5..29b4cab 100644
--- a/src/nostr/tests.rs
+++ b/src/nostr/tests.rs
@@ -1,6 +1,8 @@
-use nostr::prelude::{EventBuilder, Kind, Tag, Timestamp};
+use std::collections::HashSet;
 
-use super::runtime::NostrRendezvous;
+use nostr::prelude::{EventBuilder, Kind, RelayUrl, Tag, Timestamp};
+
+use super::runtime::{NostrRendezvous, signal_relays};
 use super::signal::{
     FreshnessOutcome, build_signal_event, create_traversal_answer, create_traversal_offer,
     estimate_clock_skew, validate_offer_freshness, validate_traversal_answer_for_offer,
@@ -708,3 +710,150 @@ fn now_ms_tracks_the_wall_clock() {
         "now_ms() is ahead of the wall clock: {sampled} > {after}"
     );
 }
+
+fn pool(urls: &[&str]) -> HashSet<RelayUrl> {
+    urls.iter()
+        .map(|url| RelayUrl::parse(url).expect("test pool url parses"))
+        .collect()
+}
+
+fn candidates(urls: &[&str]) -> Vec<String> {
+    urls.iter().map(|url| url.to_string()).collect()
+}
+
+#[test]
+fn out_of_pool_relay_does_not_suppress_the_shared_ones() {
+    let usable = signal_relays(
+        &candidates(&[
+            "wss://relay.damus.io",
+            "wss://temp.iris.to",
+            "wss://nos.lol",
+        ]),
+        None,
+        &[],
+        &pool(&[
+            "wss://relay.damus.io",
+            "wss://nos.lol",
+            "wss://offchain.pub",
+        ]),
+    );
+    assert_eq!(
+        usable,
+        vec![
+            "wss://relay.damus.io".to_string(),
+            "wss://nos.lol".to_string()
+        ],
+        "the unknown relay must be dropped without taking the shared ones with it"
+    );
+}
+
+#[test]
+fn trailing_slash_and_host_case_variants_are_retained() {
+    let usable = signal_relays(
+        &candidates(&["wss://Relay.Damus.io/", "wss://nos.lol"]),
+        None,
+        &[],
+        &pool(&["wss://relay.damus.io", "wss://nos.lol"]),
+    );
+    assert_eq!(
+        usable.len(),
+        2,
+        "normalized spellings of a configured relay are the same relay: {usable:?}"
+    );
+}
+
+#[test]
+fn duplicates_that_normalize_alike_are_collapsed() {
+    let usable = signal_relays(
+        &candidates(&["wss://nos.lol", "wss://nos.lol/", "wss://NOS.LOL"]),
+        None,
+        &[],
+        &pool(&["wss://nos.lol"]),
+    );
+    assert_eq!(usable, vec!["wss://nos.lol".to_string()]);
+}
+
+#[test]
+fn unparseable_candidates_are_dropped_rather_than_failing_the_set() {
+    let usable = signal_relays(
+        &candidates(&["not a url", "wss://nos.lol"]),
+        None,
+        &[],
+        &pool(&["wss://nos.lol"]),
+    );
+    assert_eq!(usable, vec!["wss://nos.lol".to_string()]);
+}
+
+#[test]
+fn no_shared_relay_yields_an_empty_set_for_the_caller_to_reject() {
+    let usable = signal_relays(
+        &candidates(&["wss://temp.iris.to"]),
+        None,
+        &[],
+        &pool(&["wss://nos.lol"]),
+    );
+    assert!(
+        usable.is_empty(),
+        "with no overlap the caller must see nothing to send to, not a doomed send"
+    );
+}
+
+#[test]
+fn signal_relays_merges_all_three_sources_then_filters() {
+    let usable = signal_relays(
+        &candidates(&["wss://temp.iris.to", "wss://nos.lol"]),
+        Some(&candidates(&[
+            "wss://relay.damus.io",
+            "wss://unknown.example",
+        ])),
+        &candidates(&["wss://offchain.pub"]),
+        &pool(&[
+            "wss://nos.lol",
+            "wss://relay.damus.io",
+            "wss://offchain.pub",
+        ]),
+    );
+    assert_eq!(
+        usable,
+        vec![
+            "wss://nos.lol".to_string(),
+            "wss://relay.damus.io".to_string(),
+            "wss://offchain.pub".to_string(),
+        ],
+        "every source must contribute, and only the out-of-pool entries drop out"
+    );
+}
+
+#[test]
+fn signal_relays_keeps_our_dm_relays_when_the_peer_shares_nothing() {
+    let usable = signal_relays(
+        &candidates(&["wss://temp.iris.to"]),
+        Some(&candidates(&["wss://also.unknown"])),
+        &candidates(&["wss://nos.lol"]),
+        &pool(&["wss://nos.lol"]),
+    );
+    assert_eq!(
+        usable,
+        vec!["wss://nos.lol".to_string()],
+        "our own DM relays are always in the pool, so the result is never empty \
+         while any are configured"
+    );
+}
+
+#[test]
+fn signal_relays_without_an_advert_still_resolves() {
+    let usable = signal_relays(
+        &candidates(&["wss://nos.lol", "wss://temp.iris.to"]),
+        None,
+        &candidates(&["wss://offchain.pub"]),
+        &pool(&["wss://nos.lol", "wss://offchain.pub"]),
+    );
+    assert_eq!(
+        usable,
+        vec![
+            "wss://nos.lol".to_string(),
+            "wss://offchain.pub".to_string()
+        ],
+        "the responder path passes no advert and must still produce a target set"
+    );
+}