fix(kademlia): allow clientMode without switch.mount

ServiceDiscovery.new(client=true) installs no inbound handler, so
switch.mount always failed. Skip mount for clientMode and keep the
protocol for outbound mix lookups only. Add a unit test and document
relative CHAT_UI paths in the mixnet chat-ui launcher.

logos_delivery/waku/node/waku_node.nim

@@ -391,6 +391,14 @@ proc mountKademlia*(
 
   node.wakuKademlia = wk
 
+  # ServiceDiscovery.new(client=true) intentionally installs no inbound stream
+  # handler so this node is not dialable as a DHT peer. switch.mount requires a
+  # handler, so skip mount in clientMode. Outbound lookups still work: dial +
+  # GET_ADS use the codec string without advertising it in peerInfo.protocols.
+  if config.clientMode:
+    info "Kademlia service discovery ready (clientMode, lookup-only, not mounted)"
+    return ok()
+
   let mountRes = catch:
     node.switch.mount(wk.protocol)
   mountRes.isOkOr:

simulations/mixnet/chat-ui/README.md

@@ -83,10 +83,16 @@ cd simulations/mixnet/chat-ui
 Each opens a GUI. The bottom status bar should show **`MIX 5/4`** (mix pool full)
 with the send button enabled.
 
-To iterate on a local chat-ui checkout instead of the pushed branch:
+To iterate on a local chat-ui checkout instead of the pushed branch, clone it
+**beside** `logos-delivery` and point `CHAT_UI` at it. The path is relative to
+where you run the script (`run_chat_ui.sh` resolves it to an absolute path):
 
 ```bash
-CHAT_UI="$HOME/Code/logos-chat-ui" ./run_chat_ui.sh A
+# from the same parent dir where you cloned logos-delivery:
+git clone -b feat/logos-testnetv02-mix https://github.com/logos-co/logos-chat-ui
+
+# then, back in simulations/mixnet/chat-ui:
+CHAT_UI=../../../../logos-chat-ui ./run_chat_ui.sh A
 ```
 
 ## 5. Exchange messages

simulations/mixnet/chat-ui/env.sh

@@ -21,6 +21,8 @@ export CHAT_SHARD_ID=0
 export CHAT_MIN_MIX_POOL=4
 export CHAT_MIX_REQUIRED=1   # force Required (mix) mode without the UI toggle
 
-# logos-chat-ui flake to run. Override with a local checkout to iterate, e.g.
-#   CHAT_UI="$HOME/Code/logos-chat-ui" ./run_chat_ui.sh A
+# logos-chat-ui flake to run. Override with a local checkout to iterate — a path
+# relative to where you run the script works (run_chat_ui.sh resolves it to an
+# absolute path). With logos-chat-ui cloned beside logos-delivery, e.g.:
+#   CHAT_UI=../../../../logos-chat-ui ./run_chat_ui.sh A
 export CHAT_UI="${CHAT_UI:-github:logos-co/logos-chat-ui?ref=feat/logos-testnetv02-mix}"

simulations/mixnet/chat-ui/run_chat_ui.sh

@@ -32,5 +32,14 @@ cp -f "$SIM/rln_tree.db" "$DIR/" 2>/dev/null \
   || { echo "missing rln_tree.db — run ../build_setup.sh first"; exit 1; }
 cp -f "$SIM"/rln_keystore_*.json "$DIR/"
 
+# If CHAT_UI is a local checkout (not a flake ref like github:/git+/path:),
+# resolve it to an absolute path NOW — before we cd into the per-client run dir
+# below — so it can be passed relative to where you invoke this script (e.g.
+# CHAT_UI=../../../../logos-chat-ui). Flake refs don't exist on disk, so the
+# `-e` test skips them and they're left untouched.
+if [ -e "$CHAT_UI" ]; then
+  CHAT_UI="$(cd "$CHAT_UI" && pwd)"
+fi
+
 cd "$DIR"
 exec nix run "$CHAT_UI" --accept-flake-config

tests/waku_kademlia/test_waku_kademlia.nim

@@ -36,6 +36,31 @@ suite "Waku Kademlia service discovery":
     await wk.stop()
     await switch.stop()
 
+  asyncTest "clientMode starts without mounting (lookup-only)":
+    ## ServiceDiscovery client=true omits the inbound handler; mount would raise.
+    ## Client nodes must still construct + start the protocol for outbound lookups.
+    let
+      switch = newTestSwitch()
+      wk = kad_utils.newTestKademlia(
+        switch,
+        servicesToDiscover = @["/mix/1.0.0"],
+        clientMode = true,
+        xprPublishing = false,
+      )
+    await switch.start()
+    await wk.start()
+
+    await sleepAsync(FUTURE_TIMEOUT)
+
+    check:
+      not wk.protocol.isNil()
+      wk.protocol.clientMode
+      # Codec must not be advertised — peers should not dial us for kad.
+      wk.protocol.codec notin switch.peerInfo.protocols
+
+    await wk.stop()
+    await switch.stop()
+
   suite "extractMixPubKey":
     proc validKeyBytes(): seq[byte] =
       var b = newSeq[byte](Curve25519KeySize)

tests/waku_kademlia/utils.nim

@@ -41,7 +41,9 @@ proc newTestKademlia*(
     )
     .tryGet()
 
-  switch.mount(wk.protocol)
+  # clientMode has no inbound stream handler; mount would fail (see mountKademlia).
+  if not clientMode:
+    switch.mount(wk.protocol)
   wk
 
 proc buildExtendedPeerRecord*(