diff --git a/include/ircd/m/acquire.h b/include/ircd/m/acquire.h
index ed5bd5877..5bfe4cefc 100644
--- a/include/ircd/m/acquire.h
+++ b/include/ircd/m/acquire.h
@@ -50,11 +50,23 @@ struct ircd::m::acquire::opts
 	size_t viewport_size {0};
 
 	/// The number of rounds the algorithm runs for.
-	size_t rounds {1};
+	size_t rounds {-1UL};
 
 	/// Total event limit over all operations.
 	size_t fetch_max {-1UL};
 
 	/// Limit the number of requests in flight at any given time.
 	size_t fetch_width {128};
+
+	/// Avoids filling gaps with a depth sounding lte this value
+	size_t gap_min {0};
+
+	/// Avoids filling gaps with a depth sounding greater than this value
+	size_t gap_max {-1UL};
+
+	/// Won't fetch missing unless ref gt (newer) than this idx.
+	event::idx ref_min {0};
+
+	/// Won't fetch missing unless ref lt (older) than this idx.
+	event::idx ref_max {-1UL};
 };
diff --git a/matrix/acquire.cc b/matrix/acquire.cc
index 69963e1fa..14316de86 100644
--- a/matrix/acquire.cc
+++ b/matrix/acquire.cc
@@ -17,7 +17,7 @@ namespace ircd::m::acquire
 	static bool handle(const opts &, ctx::future<m::fetch::result> &);
 	static bool handle(const opts &, list &);
 	static void fetch_head(const opts &, list &);
-	static bool fetch_missing(const opts &, list &);
+	static event::idx fetch_missing(const opts &, list &);
 	static void submit(const opts &, list &);
 };
 
@@ -42,8 +42,9 @@ ircd::m::acquire::log
 // execute::execute
 //
 
-ircd::m::acquire::execute::execute(const opts &opts)
+ircd::m::acquire::execute::execute(const opts &opts_)
 {
+	auto opts(opts_);
 	list fetching;
 
 	// Branch to acquire head
@@ -53,36 +54,61 @@ ircd::m::acquire::execute::execute(const opts &opts)
 	// Branch to acquire missing
 	if(opts.missing)
 		for(size_t i(0); i < opts.rounds; ++i)
-			if(!fetch_missing(opts, fetching))
+		{
+			event::idx last;
+			if(!(last = fetch_missing(opts, fetching)))
 				break;
 
+			// After each round, set the floor for the next round.
+			opts.ref_min = opts_.ref_min?: last + 1;
+			if(opts.ref_min > opts.ref_max)
+				break;
+		}
+
 	// Complete all work before returning, otherwise everything
 	// will be cancelled on unwind.
-	while(handle(opts, fetching));
+	while(!fetching.empty())
+		while(handle(opts, fetching));
 }
 
-bool
-ircd::m::acquire::fetch_missing(const opts &opts,
+ircd::m::event::idx
+ircd::m::acquire::fetch_missing(const opts &opts_,
                                 list &fetching)
 {
+	auto opts(opts_);
 	const auto top
 	{
 		m::top(opts.room.room_id)
 	};
 
+	const auto &[top_id, top_depth, top_idx]
+	{
+		top
+	};
+
+	// When the viewport will be counted we seek to a depth near the room head
+	// by default unless the caller forced another depth floor.
+	if(!opts.depth.first && opts.viewport_size)
+		opts.depth.first = top_depth - std::clamp(long(opts.viewport_size), 1024L, top_depth);
+
 	m::room::events::missing missing
 	{
 		opts.room
 	};
 
-	bool ret(false);
-	missing.for_each(opts.depth, [&opts, &fetching, &top, &ret]
+	event::idx last(0);
+	missing.for_each(opts.depth, [&opts, &fetching, &top, &last]
 	(const event::id &event_id, const int64_t &ref_depth, const event::idx &ref_idx)
 	{
-		// Bail if interrupted
 		if(ctx::interruption_requested())
 			return false;
 
+		if(ref_idx < opts.ref_min)
+			return true;
+
+		if(ref_idx > opts.ref_max)
+			return true;
+
 		// Branch if we have to measure the viewportion
 		if(opts.viewport_size)
 		{
@@ -94,7 +120,7 @@ ircd::m::acquire::fetch_missing(const opts &opts,
 
 			// Bail if this event sits above the viewport.
 			if(m::room::events::count(opts.room, range) > opts.viewport_size)
-				return false;
+				return true;
 		}
 
 		const auto ref_id
@@ -119,15 +145,22 @@ ircd::m::acquire::fetch_missing(const opts &opts,
 				std::make_pair(0L, 0UL)
 		};
 
+		const auto gap
+		{
+			sound_depth >= twain_depth?
+				size_t(sound_depth - twain_depth):
+				0UL
+		};
+
+		if(gap < opts.gap_min || gap > opts.gap_max)
+			return true;
+
 		auto _opts(opts);
 		_opts.room.event_id = event_id;
 		_opts.hint = opts.hint;
-		_opts.viewport_size = twain_depth?
-			std::clamp(sound_depth - twain_depth, 1L, 48L):
-			1UL;
-
+		_opts.viewport_size = std::clamp(gap, 1UL, 48UL);
 		submit(_opts, fetching);
-		ret = true;
+
 		log::debug
 		{
 			log, "Fetch %s miss prev of %s @%lu in %s @%lu sound:%lu twain:%ld fetching:%zu",
@@ -141,17 +174,23 @@ ircd::m::acquire::fetch_missing(const opts &opts,
 			fetching.size(),
 		};
 
+		last = std::max(last, ref_idx);
 		return true;
 	});
 
-	return ret;
+	return last;
 }
 
 void
 ircd::m::acquire::fetch_head(const opts &opts,
                              list &fetching)
 {
-	const auto handle_head{[&opts, &fetching]
+	const auto top
+	{
+		m::top(opts.room.room_id)
+	};
+
+	const auto handle_head{[&opts, &fetching, &top]
 	(const m::event &result)
 	{
 		// Bail if interrupted
@@ -162,20 +201,21 @@ ircd::m::acquire::fetch_head(const opts &opts,
 		if(json::get<"depth"_>(result) < opts.depth.first)
 			return false;
 
+		const auto &[top_id, top_depth, top_idx] {top};
+		const auto gap
+		{
+			json::get<"depth"_>(result) - top_depth
+		};
+
 		auto _opts(opts);
 		_opts.room.event_id = result.event_id;
 		_opts.hint = json::get<"origin"_>(result);
 		_opts.hint_only = true;
-		_opts.viewport_size = 1; //XXX
+		_opts.viewport_size = std::clamp(gap, 1L, 48L);
 		submit(_opts, fetching);
 		return true;
 	}};
 
-	const auto top
-	{
-		m::top(opts.room.room_id)
-	};
-
 	m::room::head::fetch::opts hfopts;
 	hfopts.room_id = opts.room.room_id;
 	hfopts.top = top;
@@ -190,9 +230,7 @@ ircd::m::acquire::submit(const opts &opts,
                          list &fetching)
 {
 	start(opts, fetching);
-	while(!fetching.empty())
-		if(!handle(opts, fetching))
-			break;
+	while(handle(opts, fetching));
 }
 
 void
@@ -213,6 +251,9 @@ bool
 ircd::m::acquire::handle(const opts &opts,
                          list &fetching)
 {
+	if(fetching.empty())
+		return false;
+
 	const bool full
 	{
 		fetching.size() >= opts.fetch_width
@@ -278,7 +319,8 @@ try
 	m::vm::opts vmopts;
 	vmopts.infolog_accept = true;
 	vmopts.warnlog &= ~vm::fault::EXISTS;
-	//vmopts.phase.set(m::vm::phase::NOTIFY, false);
+	vmopts.notify_servers = false;
+	vmopts.phase.set(m::vm::phase::NOTIFY, false);
 	vmopts.phase.set(m::vm::phase::FETCH_PREV, false);
 	vmopts.phase.set(m::vm::phase::FETCH_STATE, false);
 	vmopts.wopts.appendix.set(dbs::appendix::ROOM_HEAD, false);
diff --git a/matrix/init_backfill.cc b/matrix/init_backfill.cc
index 7480e609a..b15e5f424 100644
--- a/matrix/init_backfill.cc
+++ b/matrix/init_backfill.cc
@@ -305,7 +305,6 @@ ircd::m::init::backfill::handle_room(const room::id &room_id)
 	opts.room = room_id;
 	opts.viewport_size = ssize_t(m::room::events::viewport_size);
 	opts.viewport_size *= size_t(viewports);
-	opts.rounds = opts.viewport_size / 2;
 	m::acquire::execute
 	{
 		opts
diff --git a/modules/console.cc b/modules/console.cc
index 916e10149..7aec826a1 100644
--- a/modules/console.cc
+++ b/modules/console.cc
@@ -11013,7 +11013,7 @@ console_cmd__room__acquire(opt &out, const string_view &line)
 {
 	const params param{line, " ",
 	{
-		"room_id", "depth_start", "depth_stop", "viewport_size", "rounds"
+		"room_id", "depth_start", "depth_stop", "viewport_size", "gap_min", "rounds"
 	}};
 
 	const auto &room_id
@@ -11036,9 +11036,14 @@ console_cmd__room__acquire(opt &out, const string_view &line)
 		param.at("viewport_size", 0L)
 	};
 
+	const auto gap_min
+	{
+		param.at("gap_min", 0UL)
+	};
+
 	const auto rounds
 	{
-		param.at("rounds", 1L)
+		param.at("rounds", -1UL)
 	};
 
 	const m::room room
@@ -11053,6 +11058,7 @@ console_cmd__room__acquire(opt &out, const string_view &line)
 	opts.viewport_size = viewport_size;
 	opts.rounds = rounds;
 	opts.head = depth_stop == 0;
+	opts.gap_min = gap_min;
 	m::acquire::execute
 	{
 		opts