diff --git a/include/ircd/m/event.h b/include/ircd/m/event.h
index eea023505..5c45c8aab 100644
--- a/include/ircd/m/event.h
+++ b/include/ircd/m/event.h
@@ -74,4 +74,5 @@ namespace ircd::m
 #include "event/cached.h"
 #include "event/prefetch.h"
 #include "event/conforms.h"
+#include "event/append.h"
 #include "event/pretty.h"
diff --git a/include/ircd/m/event/append.h b/include/ircd/m/event/append.h
new file mode 100644
index 000000000..0f378a3cf
--- /dev/null
+++ b/include/ircd/m/event/append.h
@@ -0,0 +1,26 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_M_EVENT_APPEND
+
+namespace ircd::m
+{
+	struct event_append_opts
+	{
+		const event::idx *event_idx {nullptr};
+		const string_view *client_txnid {nullptr};
+		const id::user *user_id {nullptr};
+		const room *user_room {nullptr};
+	};
+
+	void append(json::stack::object &, const event &, const event_append_opts & = {});
+	void append(json::stack::array &, const event &, const event_append_opts & = {});
+}
diff --git a/ircd/m_event.cc b/ircd/m_event.cc
index 93b78b45e..38c57e8f4 100644
--- a/ircd/m_event.cc
+++ b/ircd/m_event.cc
@@ -143,6 +143,39 @@ ircd::m::pretty_oneline(std::ostream &s,
 	return s;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// event/append.h
+//
+
+void
+ircd::m::append(json::stack::array &array,
+                const event &event_,
+                const event_append_opts &opts)
+{
+	json::stack::object object
+	{
+		array
+	};
+
+	append(object, event_, opts);
+}
+
+void
+ircd::m::append(json::stack::object &object,
+                const event &event_,
+                const event_append_opts &opts)
+{
+	using prototype = void (json::stack::object &, const event &, const event_append_opts &);
+
+	static mods::import<prototype> call
+	{
+		"m_event", "ircd::m::append"
+	};
+
+	call(object, event_, opts);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // event/conforms.h
diff --git a/modules/m_event.cc b/modules/m_event.cc
index dabe6d33f..398935159 100644
--- a/modules/m_event.cc
+++ b/modules/m_event.cc
@@ -450,6 +450,84 @@ ircd::m::pretty_oneline(std::ostream &s,
 	return s;
 }
 
+void
+IRCD_MODULE_EXPORT
+ircd::m::append(json::stack::object &object,
+                const event &event,
+                const event_append_opts &opts)
+{
+	const bool has_event_idx
+	{
+		opts.event_idx && *opts.event_idx
+	};
+
+	const bool has_client_txnid
+	{
+		opts.client_txnid && *opts.client_txnid
+	};
+
+	const bool has_user
+	{
+		opts.user_id && opts.user_room
+	};
+
+	const bool sender_is_user
+	{
+		has_user && json::get<"sender"_>(event) == *opts.user_id
+	};
+
+	const auto txnid_idx
+	{
+		!has_client_txnid && sender_is_user?
+			opts.user_room->get(std::nothrow, "ircd.client.txnid", at<"event_id"_>(event)):
+			0UL
+	};
+
+	if(!has_client_txnid && !txnid_idx && sender_is_user)
+		log::dwarning
+		{
+			log, "Could not find transaction_id for %s from %s in %s",
+			json::get<"event_id"_>(event),
+			json::get<"sender"_>(event),
+			json::get<"room_id"_>(event)
+		};
+
+	object.append(event);
+
+	if(!has_event_idx && !txnid_idx)
+		return;
+
+	json::stack::object unsigned_
+	{
+		object, "unsigned"
+	};
+
+	if(has_client_txnid)
+		json::stack::member
+		{
+			unsigned_, "transaction_id", *opts.client_txnid
+		};
+
+	if(has_event_idx)
+		json::stack::member
+		{
+			unsigned_, "age", json::value
+			{
+				long(vm::current_sequence - *opts.event_idx)
+			}
+		};
+
+	if(txnid_idx)
+		m::get(std::nothrow, txnid_idx, "content", [&unsigned_]
+		(const json::object &content)
+		{
+			json::stack::member
+			{
+				unsigned_, "transaction_id", unquote(content.get("transaction_id"))
+			};
+		});
+}
+
 bool
 IRCD_MODULE_EXPORT
 ircd::m::event::auth::chain::for_each(const auth::chain &c,