diff --git a/pkg/machine/machine.go b/pkg/machine/machine.go
index 8bcaf88..ba0952e 100644
--- a/pkg/machine/machine.go
+++ b/pkg/machine/machine.go
@@ -16,6 +16,7 @@ import (
 	"slices"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -53,7 +54,7 @@ type Machine struct {
 	// Tracers are optional tracers for telemetry integrations.
 	Tracers []Tracer
 	// If true, the machine has been Disposed and is no-op. Read-only.
-	Disposed bool
+	Disposed atomic.Bool
 	// ParentID is the ID of the parent machine (if any).
 	ParentID string
 	// Tags are optional tags for telemetry integrations etc.
@@ -285,7 +286,7 @@ func (m *Machine) Dispose() {
 	// handler
 
 	go func() {
-		if m.Disposed {
+		if m.Disposed.Load() {
 			return
 		}
 		m.queueProcessing.Lock()
@@ -301,7 +302,10 @@ func (m *Machine) DisposeForce() {
 }
 
 func (m *Machine) dispose(force bool) {
-	m.Disposed = true
+	if !m.Disposed.CompareAndSwap(false, true) {
+		// already disposed
+		return
+	}
 
 	for i := range m.Tracers {
 		m.Tracers[i].MachineDispose(m.ID)
@@ -359,8 +363,12 @@ func (m *Machine) dispose(force bool) {
 	closeSafe(m.handlerEnd)
 	closeSafe(m.handlerPanic)
 	closeSafe(m.handlerStart)
-	m.handlerTimer.Stop()
-	m.handlerTimer = nil
+
+	if m.handlerTimer != nil {
+		m.handlerTimer.Stop()
+		m.handlerTimer = nil
+	}
+
 	m.clock = nil
 
 	// release the queue lock
@@ -377,7 +385,7 @@ func (m *Machine) dispose(force bool) {
 	m.disposeHandlers = nil
 
 	// the end
-	close(m.whenDisposed)
+	closeSafe(m.whenDisposed)
 }
 
 // disposeEmitter detaches the emitter from the machine and disposes it.
@@ -404,7 +412,7 @@ func (m *Machine) WhenErr(ctx context.Context) <-chan struct{} {
 // TODO re-use channels with the same state set and context
 func (m *Machine) When(states S, ctx context.Context) <-chan struct{} {
 	ch := make(chan struct{})
-	if m.Disposed {
+	if m.Disposed.Load() {
 		close(ch)
 		return ch
 	}
@@ -464,7 +472,7 @@ func (m *Machine) When1(state string, ctx context.Context) <-chan struct{} {
 // listening on 2 WhenNot() channels within the same `select` to GC the 2nd one.
 func (m *Machine) WhenNot(states S, ctx context.Context) <-chan struct{} {
 	ch := make(chan struct{})
-	if m.Disposed {
+	if m.Disposed.Load() {
 		close(ch)
 		return ch
 	}
@@ -527,7 +535,7 @@ func (m *Machine) WhenArgs(
 ) <-chan struct{} {
 	ch := make(chan struct{})
 
-	if m.Disposed {
+	if m.Disposed.Load() {
 		close(ch)
 
 		return ch
@@ -578,7 +586,7 @@ func (m *Machine) WhenTime(
 ) <-chan struct{} {
 	ch := make(chan struct{})
 	valid := len(states) == len(times)
-	if m.Disposed || !valid {
+	if m.Disposed.Load() || !valid {
 		if !valid {
 			m.log(LogDecisions, "[when:time] times for all passed stated required")
 		}
@@ -660,7 +668,7 @@ func (m *Machine) WhenTicksEq(
 func (m *Machine) WhenQueueEnds(ctx context.Context) <-chan struct{} {
 	ch := make(chan struct{})
 
-	if m.Disposed {
+	if m.Disposed.Load() {
 		close(ch)
 
 		return ch
@@ -697,7 +705,7 @@ func (m *Machine) WhenQueueEnds(ctx context.Context) <-chan struct{} {
 			case <-ctx.Done():
 			}
 			// GC only if needed
-			if m.Disposed {
+			if m.Disposed.Load() {
 				return
 			}
 
@@ -769,7 +777,7 @@ func (m *Machine) TimeSum(states S) uint64 {
 // transition (Executed, Queued, Canceled).
 // Like every mutation method, it will resolve relations and trigger handlers.
 func (m *Machine) Add(states S, args A) Result {
-	if m.Disposed || m.queueLen >= m.QueueLimit {
+	if m.Disposed.Load() || m.queueLen >= m.QueueLimit {
 		return Canceled
 	}
 	m.queueMutation(MutationAdd, states, args)
@@ -786,7 +794,7 @@ func (m *Machine) Add1(state string, args A) Result {
 // error.
 // Like every mutation method, it will resolve relations and trigger handlers.
 func (m *Machine) AddErr(err error) Result {
-	if m.Disposed {
+	if m.Disposed.Load() {
 		return Canceled
 	}
 	// TODO test .Err
@@ -811,7 +819,7 @@ func (m *Machine) IsErr() bool {
 // the transition (Executed, Queued, Canceled).
 // Like every mutation method, it will resolve relations and trigger handlers.
 func (m *Machine) Remove(states S, args A) Result {
-	if m.Disposed || m.queueLen >= m.QueueLimit {
+	if m.Disposed.Load() || m.queueLen >= m.QueueLimit {
 		return Canceled
 	}
 
@@ -846,7 +854,7 @@ func (m *Machine) Remove1(state string, args A) Result {
 // the transition (Executed, Queued, Canceled).
 // Like every mutation method, it will resolve relations and trigger handlers.
 func (m *Machine) Set(states S, args A) Result {
-	if m.Disposed || m.queueLen >= m.QueueLimit {
+	if m.Disposed.Load() || m.queueLen >= m.QueueLimit {
 		return Canceled
 	}
 	m.queueMutation(MutationSet, states, args)
@@ -1125,7 +1133,7 @@ func (m *Machine) BindHandlers(handlers any) error {
 // The Tracer API is a better way to event feeds.
 func (m *Machine) OnEvent(events []string, ctx context.Context) chan *Event {
 	ch := make(chan *Event, 50)
-	if m.Disposed {
+	if m.Disposed.Load() {
 		ch := make(chan *Event)
 		close(ch)
 		return ch
@@ -1154,7 +1162,7 @@ func (m *Machine) OnEvent(events []string, ctx context.Context) chan *Event {
 			}
 
 			// GC only if needed
-			if m.Disposed {
+			if m.Disposed.Load() {
 				return
 			}
 
@@ -1384,7 +1392,7 @@ func (m *Machine) setActiveStates(calledStates S, targetStates S,
 // machine.
 func (m *Machine) processQueue() Result {
 	// empty queue
-	if len(m.queue) == 0 || m.Disposed {
+	if len(m.queue) == 0 || m.Disposed.Load() {
 		return Canceled
 	}
 
@@ -1412,7 +1420,7 @@ func (m *Machine) processQueue() Result {
 	for len(m.queue) > 0 {
 		m.queueRunning = true
 
-		if m.Disposed {
+		if m.Disposed.Load() {
 			return Canceled
 		}
 		if len(m.queue) == 0 {
@@ -1706,6 +1714,8 @@ func (m *Machine) log(level LogLevel, msg string, args ...any) {
 		// transition
 		m.logEntriesLock.Lock()
 		defer m.logEntriesLock.Unlock()
+
+		// TODO include log level for am-dbg filtering
 		m.logEntries = append(m.logEntries, out)
 	}
 }
@@ -1784,7 +1794,7 @@ func (m *Machine) processEmitters(e *Event) (Result, bool) {
 	handlerCalled := false
 	for _, emitter = range m.emitters {
 		// disposed
-		if m.Disposed {
+		if m.Disposed.Load() {
 			break
 		}
 		// internal event
@@ -1880,7 +1890,7 @@ func (m *Machine) handlerLoop() {
 		// catch panics and fwd
 		defer func() {
 			r := recover()
-			if r != nil && !m.Disposed {
+			if r != nil && !m.Disposed.Load() {
 				m.handlerPanic <- r
 			}
 		}()
@@ -1907,7 +1917,7 @@ func (m *Machine) handlerLoop() {
 				ret = callRet[0].Interface().(bool)
 			}
 
-			if call.timeout || m.Disposed {
+			if call.timeout || m.Disposed.Load() {
 				continue
 			}
 
diff --git a/pkg/machine/misc.go b/pkg/machine/misc.go
index 65e8fe0..5dd9253 100644
--- a/pkg/machine/misc.go
+++ b/pkg/machine/misc.go
@@ -812,7 +812,7 @@ func diposeWithCtx[T comparable](
 		case <-ctx.Done():
 		}
 		// GC only if needed
-		if mach.Disposed {
+		if mach.Disposed.Load() {
 			return
 		}
 
diff --git a/tools/cmd/am-dbg/main.go b/tools/cmd/am-dbg/main.go
index bcaf749..4b32982 100644
--- a/tools/cmd/am-dbg/main.go
+++ b/tools/cmd/am-dbg/main.go
@@ -12,8 +12,8 @@ import (
 	am "github.com/pancsta/asyncmachine-go/pkg/machine"
 	"github.com/pancsta/asyncmachine-go/pkg/telemetry"
 	"github.com/pancsta/asyncmachine-go/tools/debugger"
-	ss "github.com/pancsta/asyncmachine-go/tools/debugger/states"
 	"github.com/pancsta/asyncmachine-go/tools/debugger/server"
+	ss "github.com/pancsta/asyncmachine-go/tools/debugger/states"
 
 	"github.com/spf13/cobra"
 )
diff --git a/tools/debugger/debugger.go b/tools/debugger/debugger.go
index 8012777..b58ac77 100644
--- a/tools/debugger/debugger.go
+++ b/tools/debugger/debugger.go
@@ -33,7 +33,7 @@ const (
 	// TODO customize
 	playInterval = 500 * time.Millisecond
 	// TODO add param --max-clients
-	maxClients            = 150
+	maxClients            = 500
 	timeFormat            = "15:04:05.000000000"
 	fastJumpAmount        = 50
 	arrowThrottleMs       = 200
@@ -243,14 +243,17 @@ func (d *Debugger) updateFiltersBar() {
 
 	// tx filters
 	for _, item := range filters {
+
+		// checked
 		if item.active {
 			text += f(" [::b]%s[::-]", cview.Escape("[X]"))
 		} else {
 			text += f(" [ ]")
 		}
 
+		// focused
 		if d.focusedFilter == item.id && focused {
-			text += f("[%s][::b]%s[::-]", colorActive, item.label)
+			text += f("[%s][::bu]%s[::-]", colorActive, item.label)
 		} else if !focused {
 			text += f("[%s]%s", colorHighlight2, item.label)
 		} else {
@@ -483,11 +486,6 @@ func (d *Debugger) updateTimelines() {
 		d.timelineSteps.SetFilledColor(tcell.ColorRed)
 	}
 
-	// inactive steps bar when no next tx
-	if nextTx == nil {
-		d.timelineSteps.SetTitleColor(tcell.ColorGrey)
-		d.timelineSteps.SetBorderColor(tcell.ColorGrey)
-	}
 	stepsCount := 0
 	onLastTx := c.CursorTx >= txCount
 	if !onLastTx {
@@ -544,7 +542,7 @@ func (d *Debugger) updateSidebar(immediate bool) {
 
 // TODO sometimes scrolls for no reason
 func (d *Debugger) doUpdateSidebar() {
-	if d.Mach.Disposed {
+	if d.Mach.Disposed.Load() {
 		return
 	}
 
diff --git a/tools/debugger/handlers.go b/tools/debugger/handlers.go
index f096ffd..73fa36e 100644
--- a/tools/debugger/handlers.go
+++ b/tools/debugger/handlers.go
@@ -187,7 +187,7 @@ func (d *Debugger) PausedState(_ *am.Event) {
 }
 
 func (d *Debugger) TailModeState(_ *am.Event) {
-	d.C.CursorTx = d.filterTxCursor(d.C, len(d.C.MsgTxs), true)
+	d.C.CursorTx = d.filterTxCursor(d.C, len(d.C.MsgTxs), false)
 	// needed bc tail mode if carried over via SelectingClient
 	d.updateTxBars()
 	d.updateTimelines()
@@ -527,7 +527,8 @@ func (d *Debugger) ClientMsgState(e *am.Event) {
 	d.updateSidebar(false)
 	// UI updates for the selected client
 	if updateTailMode {
-		d.C.CursorTx = d.filterTxCursor(d.C, len(d.C.MsgTxs), true)
+		// force the latest tx
+		d.C.CursorTx = d.filterTxCursor(d.C, len(d.C.MsgTxs), false)
 		d.updateViews(false)
 	}
 
@@ -580,6 +581,7 @@ func (d *Debugger) RemoveClientState(e *am.Event) {
 	} else {
 		d.buildSidebar(-1)
 	}
+
 	d.draw()
 }
 
@@ -837,6 +839,7 @@ func (d *Debugger) ToggleFilterState(_ *am.Event) {
 		// TODO split the state
 		<-d.Mach.WhenQueueEnds(stateCtx)
 		if stateCtx.Err() != nil {
+			d.Mach.Remove1(ss.ToggleFilter, nil)
 			return // expired
 		}
 
@@ -844,18 +847,22 @@ func (d *Debugger) ToggleFilterState(_ *am.Event) {
 			d.filterClientTxs()
 		}
 
-		// rebuild the whole log to reflect the UI changes
-		err := d.rebuildLog(stateCtx, len(d.C.MsgTxs)-1)
-		if err != nil {
-			d.Mach.AddErr(err)
-		}
-		d.updateLog(false)
+		if d.C != nil {
 
-		if stateCtx.Err() != nil {
-			return // expired
+			// rebuild the whole log to reflect the UI changes
+			err := d.rebuildLog(stateCtx, len(d.C.MsgTxs)-1)
+			if err != nil {
+				d.Mach.AddErr(err)
+			}
+			d.updateLog(false)
+
+			if stateCtx.Err() != nil {
+				return // expired
+			}
+
+			d.C.CursorTx = d.filterTxCursor(d.C, d.C.CursorTx, false)
 		}
 
-		d.C.CursorTx = d.filterTxCursor(d.C, d.C.CursorTx, false)
 		// queue this removal after filter states, so we can depend on WhenNot
 		d.Mach.Remove1(ss.ToggleFilter, nil)