diff --git a/include/bitcoin/node/protocols/protocol_observer.hpp b/include/bitcoin/node/protocols/protocol_observer.hpp
index c1e145c8..fd414b19 100644
--- a/include/bitcoin/node/protocols/protocol_observer.hpp
+++ b/include/bitcoin/node/protocols/protocol_observer.hpp
@@ -44,6 +44,7 @@ class BCN_API protocol_observer
                 is_negotiated(network::messages::peer::level::bip37) &&
             !session->network_settings().enable_relay
         ),
+        group_(to_group<std::decay_t<decltype(*session)>>()),
         network::tracker<protocol_observer>(session->log)
     {
     }
@@ -63,9 +64,33 @@ class BCN_API protocol_observer
     virtual bool handle_receive_inventory(const code& ec,
         const network::messages::peer::inventory::cptr& message) NOEXCEPT;
 
+    /// Add the channel row to a capture of which it is a member.
+    virtual bool handle_broadcast_diagnostics(const code& ec,
+        const network::diagnostics::cptr& message, uint64_t sender) NOEXCEPT;
+
+    /// The capture group of the channel (the session determines the group).
+    virtual network::diagnostics::target group() const NOEXCEPT;
+
 private:
+    // The session configuration type identifies its capture group.
+    template <typename Session>
+    static constexpr network::diagnostics::target to_group() NOEXCEPT
+    {
+        using options = typename Session::options_t;
+        using inbound = network::settings::peer_inbound;
+        using manual = network::settings::peer_manual;
+
+        if constexpr (is_same_type<options, inbound>)
+            return network::diagnostics::target::inbound;
+        else if constexpr (is_same_type<options, manual>)
+            return network::diagnostics::target::manual;
+        else
+            return network::diagnostics::target::outbound;
+    }
+
     // These are thread safe.
     const bool relay_disallowed_;
+    const network::diagnostics::target group_;
 };
 
 } // namespace node
diff --git a/src/protocols/protocol_observer.cpp b/src/protocols/protocol_observer.cpp
index 85cc95a3..ac36bccf 100644
--- a/src/protocols/protocol_observer.cpp
+++ b/src/protocols/protocol_observer.cpp
@@ -50,6 +50,9 @@ void protocol_observer::start() NOEXCEPT
         SUBSCRIBE_CHANNEL(inventory, handle_receive_inventory, _1, _2);
     }
 
+    SUBSCRIBE_BROADCAST(network::diagnostics, handle_broadcast_diagnostics,
+        _1, _2, _3);
+
     ////SUBSCRIBE_CHANNEL(get_data, handle_receive_get_data, _1, _2);
     protocol_peer::start();
 }
@@ -117,6 +120,43 @@ bool protocol_observer::handle_receive_inventory(const code& ec,
     return true;
 }
 
+// Diagnostics (capture).
+// ----------------------------------------------------------------------------
+
+network::diagnostics::target protocol_observer::group() const NOEXCEPT
+{
+    return group_;
+}
+
+bool protocol_observer::handle_broadcast_diagnostics(const code& ec,
+    const network::diagnostics::cptr& message, uint64_t) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    if (stopped(ec))
+        return false;
+
+    if (!message->member(identifier()) && !message->member(group()))
+        return true;
+
+    const auto peer = peer_version();
+
+    message->add(
+    {
+        identifier(),
+        outbound(),
+        group(),
+        negotiated_version(),
+        peer ? peer->services : service::node_none,
+        sent(),
+        start_height(),
+        encrypted(),
+        peer ? peer->user_agent : std::string{}
+    });
+
+    return true;
+}
+
 BC_POP_WARNING()
 BC_POP_WARNING()