diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87aa8e4..1438131 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -494,6 +494,14 @@ because it turns other people's test suites red.
   again for each one. Both are now done once, and the window uses less memory
   while you type.
 
+- **Typing on the `Presets` screen no longer lags.** With `upload-validation`
+  chosen, every key typed into a box held the window for about 0.3 seconds,
+  and about 0.07 seconds with `tabular-import`, because the preset was worked
+  out twice for each key. Typing the seed or the output folder now takes no
+  noticeable time, and changing a setting of the preset itself takes half as
+  long as before. On the `Several batches` screen with a preset switched on,
+  a key typed into a box now works the preset out once rather than twice.
+
 - **A preview or a run refused while it was being planned no longer leaves
   "Working out what this would cost..." standing over the refusal.**
 
diff --git a/internal/guard/settleonce_test.go b/internal/guard/settleonce_test.go
new file mode 100644
index 0000000..c12a3d3
--- /dev/null
+++ b/internal/guard/settleonce_test.go
@@ -0,0 +1,174 @@
+package guard
+
+import (
+	"testing"
+
+	"github.com/donislawdev/TestingFilesGenerator/internal/engine"
+	"github.com/donislawdev/TestingFilesGenerator/internal/format"
+	"github.com/donislawdev/TestingFilesGenerator/internal/gui/parts"
+	"github.com/donislawdev/TestingFilesGenerator/internal/gui/window"
+	"github.com/donislawdev/TestingFilesGenerator/internal/recipe"
+)
+
+// One change of a box reads the form once, on every screen.
+//
+// Reading the form is settle, and on the preset screen settle expands the
+// preset. Until 2026-09-23 every change read it twice - once for the line under
+// the buttons and once to mark the box - and with upload-validation chosen that
+// was 271-295 ms of the window's thread for every key typed, half of it working
+// out an answer the line had just been given (docs/GUI-MEMORY-2026-09-23.md
+// section 4h).
+//
+// Counted rather than timed, because a time says how fast this machine is and
+// the count is the defect. Asked as exactly one rather than at most one: a
+// screen whose readings stopped reaching the host would count nought and pass
+// a ceiling, so nought is this guard not being in the state it asks about.
+//
+// An emptied box is asked about as well, because it takes the other way out of
+// the live check - the line is said and the box is left alone - and that early
+// return is where a second reading was sitting.
+func TestOneChangeOfABoxReadsTheFormOnce(t *testing.T) {
+	host := newFakeHost(t)
+	gen, pre, rec := window.NewGenerate(host), window.NewPreset(host), window.NewRecipe(host)
+	chooserIn(t, pre.Fields(), settingPresetBox).SetSelected("size-boundaries")
+
+	for _, b := range []struct {
+		screen string
+		fields *parts.Fields
+		at     string
+		values []string
+	}{
+		{"single batch", gen.Fields(), engine.SettingSeed, []string{"7", "", "42"}},
+		{"single batch", gen.Fields(), format.SettingSize, []string{"3kb", "", "5kb"}},
+		{"presets", pre.Fields(), engine.SettingSeed, []string{"7", "", "42"}},
+		{"presets", pre.Fields(), "limit", []string{"20mb", "", "30mb"}},
+		{"several batches", rec.Fields(), recipe.KeySeed, []string{"7", "", "42"}},
+		{"several batches", rec.Fields(), recipe.TargetAddress(1, recipe.KeySize), []string{"3kb", "", "5kb"}},
+	} {
+		for _, v := range b.values {
+			box := entryIn(t, b.fields, b.at)
+			if box.Text == v {
+				t.Fatalf("%q already holds %q on the %s screen, so typing it would change nothing and this guard would ask about no change",
+					b.at, v, b.screen)
+			}
+			host.settles = 0
+			box.SetText(v)
+			switch {
+			case host.settles == 0:
+				t.Fatalf("typing %q into %q on the %s screen told the host of no reading of the form - "+
+					"either the box reports no change or the screen reads its form without countedSettle, and this guard sees nothing either way",
+					v, b.at, b.screen)
+			case host.settles > 1:
+				t.Errorf("typing %q into %q on the %s screen read the form %d times, expected once - "+
+					"on the preset screen every reading expands the preset",
+					v, b.at, b.screen, host.settles)
+			}
+		}
+	}
+}
+
+// Typing into a box a preset is not given does not expand the preset again.
+//
+// The seed and the output directory are read with the preset's values but are
+// not among them, so what the preset expands to cannot depend on either. The
+// screen expanded it on every key anyway until 2026-09-23 - 157-180 ms and
+// 60 MB each time for upload-validation, which encodes images to find its
+// sizes. The screen remembers its last expansion now (lastExpansion in
+// internal/gui/window/preset.go).
+//
+// upload-validation because it is the one that cost the most, though the
+// count does not depend on which preset is chosen.
+func TestTypingWhatAPresetIsNotGivenDoesNotExpandItAgain(t *testing.T) {
+	host := newFakeHost(t)
+	pre := window.NewPreset(host)
+	chooserIn(t, pre.Fields(), settingPresetBox).SetSelected("upload-validation")
+	if host.expansions == 0 {
+		t.Fatal("building the screen and choosing a preset expanded nothing, so either the preset screen no longer expands through lastExpansion or this guard is not in the state it asks about")
+	}
+
+	host.settles, host.expansions = 0, 0
+	seed := entryIn(t, pre.Fields(), engine.SettingSeed)
+	for _, v := range []string{"1", "12", "123"} {
+		seed.SetText(v)
+	}
+	dir := entryIn(t, pre.Fields(), engine.SettingOutDir)
+	dir.SetText(dir.Text + "-x")
+
+	// The half that shows the keys were heard at all. Without it, a screen that
+	// stopped reading its form would expand nothing and pass.
+	if host.settles != 4 {
+		t.Fatalf("four keys read the form %d time(s), so this guard is not counting what it thinks it is", host.settles)
+	}
+	if host.expansions != 0 {
+		t.Errorf("typing into the seed and the output directory expanded the preset %d time(s), and neither is something a preset is given",
+			host.expansions)
+	}
+}
+
+// A changed preset value, or another preset chosen, is expanded again.
+//
+// The other half of the one above, and the half without which a screen that
+// remembers one expansion forever would pass it. Asked twice: through the
+// count, and through what the line under the buttons says - an expansion
+// worked out again and then not used is the same defect with the count right.
+func TestAChangedPresetValueIsExpandedAgain(t *testing.T) {
+	host := newFakeHost(t)
+	pre := window.NewPreset(host)
+	chooserIn(t, pre.Fields(), settingPresetBox).SetSelected("size-boundaries")
+	before := statusLine(t, pre.Object())
+	if before == "" {
+		t.Fatal("the line under the buttons says nothing with size-boundaries chosen, so there is nothing to compare a change against")
+	}
+
+	host.expansions = 0
+	entryIn(t, pre.Fields(), "limit").SetText("20mb")
+	if host.expansions != 1 {
+		t.Errorf("a new limit was typed and the preset was expanded %d time(s), expected once", host.expansions)
+	}
+	if after := statusLine(t, pre.Object()); after == before {
+		t.Errorf("a new limit was typed and the line still says what the old one came to:\n  %q", after)
+	}
+
+	// Another preset, with nothing given to either, so only the name tells the
+	// two apart. Asked of the screen rather than assumed: size-boundaries was
+	// the first choice here, and its format menu arrives with a value chosen,
+	// so the two differed by what they were given and a screen that ignored
+	// the name passed - measured by mutation on 2026-09-23.
+	fresh := newFakeHost(t)
+	other := window.NewPreset(fresh)
+	chooserIn(t, other.Fields(), settingPresetBox).SetSelected("empty-and-minimal")
+	nothingGiven(t, other.Fields(), "empty-and-minimal")
+	first := statusLine(t, other.Object())
+	fresh.expansions = 0
+	chooserIn(t, other.Fields(), settingPresetBox).SetSelected("text-encoding")
+	nothingGiven(t, other.Fields(), "text-encoding")
+	if fresh.expansions != 1 {
+		t.Errorf("another preset was chosen and it was expanded %d time(s), expected once", fresh.expansions)
+	}
+	if second := statusLine(t, other.Object()); second == first {
+		t.Errorf("another preset was chosen and the line still says what the first came to:\n  %q", second)
+	}
+}
+
+// nothingGiven stops a guard whose preset is given a value: every box and menu
+// the preset screen draws for the chosen preset has to be empty.
+func nothingGiven(t *testing.T, fields *parts.Fields, id string) {
+	t.Helper()
+	for _, f := range fields.All() {
+		switch f.Setting {
+		case settingPresetBox, engine.SettingSeed, engine.SettingOutDir:
+			continue
+		}
+		if e := firstEntryIn(f.Control); e != nil && e.Text != "" {
+			t.Fatalf("%s is given %s=%q, so it is not only the name that tells it from another preset", id, f.Setting, e.Text)
+		}
+		if c, is := f.Control.(*parts.Chooser); is && c.Selected != "" {
+			t.Fatalf("%s is given %s=%q, so it is not only the name that tells it from another preset", id, f.Setting, c.Selected)
+		}
+	}
+}
+
+// settingPresetBox is the address the preset screen registers its menu of
+// presets under - a key of that screen rather than of a recipe, see
+// settingPreset in internal/gui/window/preset.go.
+const settingPresetBox = "preset"
diff --git a/internal/guard/window_test.go b/internal/guard/window_test.go
index 96e50a5..e673b11 100644
--- a/internal/guard/window_test.go
+++ b/internal/guard/window_test.go
@@ -94,6 +94,10 @@ type fakeHost struct {
 	// held is what the window asked to run later and has not run yet, when a
 	// guard is holding the clock - see Later. Nil means the clock runs at once.
 	held *heldClock
+
+	// settles and expansions count what Settling and ExpandingPreset were told.
+	settles    int
+	expansions int
 }
 
 // heldClock keeps what the window asked for later, so a guard can look at the
@@ -193,6 +197,13 @@ func (h *fakeHost) holdTheClock() *heldClock {
 func (h *fakeHost) SetWaitForWork(fn func()) { h.waitForWork = fn }
 func (h *fakeHost) Close()                   { h.closed++ }
 
+// Settling and ExpandingPreset are two more optional interfaces a real window
+// does not implement: a screen reading its form, and the preset screen
+// expanding a preset rather than taking what it remembers. Counted for
+// settleonce_test.go, and every other guard runs through them unaware.
+func (h *fakeHost) Settling()        { h.settles++ }
+func (h *fakeHost) ExpandingPreset() { h.expansions++ }
+
 // HoldDuringRun is the other optional interface, and the other direction: the
 // window asks the host for this one rather than handing it over.
 //
diff --git a/internal/gui/window/generate.go b/internal/gui/window/generate.go
index f0d14b5..2d22ce2 100644
--- a/internal/gui/window/generate.go
+++ b/internal/gui/window/generate.go
@@ -202,7 +202,7 @@ type Generate struct {
 // NewGenerate builds the screen. links are the buttons to the other screens.
 func NewGenerate(host Host, links ...fyne.CanvasObject) *Generate {
 	g := &Generate{runner: newRunner(host.Later), host: host, tips: parts.NewTips(), settingsFolded: true}
-	g.runner.settle = g.settle
+	g.runner.settle = countedSettle(host, g.settle)
 	g.runner.offer.through(host)
 	// This screen is one target and draws its boxes under the bare key, so a
 	// refusal that arrives carrying a position belongs to the box of that name.
diff --git a/internal/gui/window/open.go b/internal/gui/window/open.go
index 66a3224..b6d0ec0 100644
--- a/internal/gui/window/open.go
+++ b/internal/gui/window/open.go
@@ -7,6 +7,7 @@ import (
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/container"
 	"fyne.io/fyne/v2/driver/desktop"
+	"github.com/donislawdev/TestingFilesGenerator/internal/engine"
 	"github.com/donislawdev/TestingFilesGenerator/internal/gui/parts"
 	"github.com/donislawdev/TestingFilesGenerator/internal/gui/text"
 )
@@ -448,3 +449,34 @@ func offerHolding(h Host, screens []interface{ HoldBeforeFinishing(func()) }) {
 		screen.HoldBeforeFinishing(hold)
 	}
 }
+
+// countedSettle is a screen's reading of its form, told to a host that counts
+// the readings and handed back untouched to any other.
+//
+// The same shape as the two above - an optional interface, checked rather than
+// required, and nothing in the shipped program implements it. It is here for a
+// number a guard cannot read off the screen: how many times one change of a
+// box read the form. It was two until 2026-09-23, once for the line and once
+// for the box, and on the preset screen every reading expanded the preset -
+// 271-295 ms of the window's thread per key for upload-validation, measured
+// in docs/GUI-MEMORY-2026-09-23.md section 4h.
+func countedSettle(h Host, settle settler) settler {
+	c, ok := h.(interface{ Settling() })
+	if !ok {
+		return settle
+	}
+	return func() ([]engine.Target, engine.Options, error) {
+		c.Settling()
+		return settle()
+	}
+}
+
+// tellExpanding says to a host that counts them that a preset is being
+// expanded rather than taken from what the screen remembers - see
+// lastExpansion. The same kind of seam as countedSettle, for the other half
+// of the same question.
+func tellExpanding(h Host) {
+	if c, ok := h.(interface{ ExpandingPreset() }); ok {
+		c.ExpandingPreset()
+	}
+}
diff --git a/internal/gui/window/preset.go b/internal/gui/window/preset.go
index 035b656..d1395f2 100644
--- a/internal/gui/window/preset.go
+++ b/internal/gui/window/preset.go
@@ -2,6 +2,8 @@ package window
 
 import (
 	"errors"
+	"maps"
+	"slices"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/container"
@@ -47,6 +49,10 @@ type Preset struct {
 	// fixed is how many fields this screen has before a preset declares any.
 	fixed int
 
+	// last is the preset expanded last and what it came to, so that typing in
+	// a box the preset is not given does not expand it again.
+	last lastExpansion
+
 	body fyne.CanvasObject
 }
 
@@ -54,7 +60,7 @@ type Preset struct {
 func NewPreset(host Host, links ...fyne.CanvasObject) *Preset {
 	p := &Preset{runner: newRunner(host.Later), host: host, tips: parts.NewTips()}
 	p.runner.offer.through(host)
-	p.runner.settle = p.settle
+	p.runner.settle = countedSettle(host, p.settle)
 	// No readdress here, and that is the boundary of this screen rather than an
 	// omission. The other two screens draw boxes for the settings of a target,
 	// so a refusal carrying a position has a box to be moved onto. This one
@@ -252,7 +258,8 @@ func (p *Preset) given() preset.Args {
 // Source rather than a structure, and the same parser a handwritten file goes
 // through - PR5. So what this screen runs is what "tfg preset eject" prints and
 // what "tfg generate --preset" consumes, down to the bytes, because there is
-// only one expansion and all three call it.
+// only one expansion and all three call it. Called once per set of values
+// rather than once per reading of the form - see lastExpansion.
 func (p *Preset) settle() ([]engine.Target, engine.Options, error) {
 	var none engine.Options
 
@@ -278,7 +285,7 @@ func (p *Preset) settle() ([]engine.Target, engine.Options, error) {
 		bad = append(bad, err)
 	}
 
-	expanded, err := preset.Expand(p.pick.Selected, p.given())
+	expanded, notes, err := p.last.of(p.host, p.pick.Selected, p.given())
 	if err != nil {
 		bad = append(bad, err)
 	}
@@ -296,7 +303,7 @@ func (p *Preset) settle() ([]engine.Target, engine.Options, error) {
 	}
 
 	// What the run has to say out loud about a value nobody gave it.
-	p.notes = expanded.Notes()
+	p.notes = notes
 
 	targets := make([]engine.Target, 0, len(rec.Targets))
 	for _, t := range rec.Targets {
@@ -313,14 +320,65 @@ func (p *Preset) settle() ([]engine.Target, engine.Options, error) {
 		Command:      "tfg-gui",
 		ManifestName: engine.DefaultManifestName,
 		RecipeHash:   hash,
+		// Copies, because the expansion stays behind for the next reading of
+		// the form while these go to a worker and into a manifest. Nothing
+		// writes to either today - checked 2026-09-23 - and no guard would
+		// notice the day something did, so the copy is the whole defence.
 		Preset: &manifest.Preset{
 			ID:         expanded.Preset.ID,
-			Parameters: map[string]string(expanded.Settled),
-			Defaulted:  expanded.Defaulted,
+			Parameters: maps.Clone(map[string]string(expanded.Settled)),
+			Defaulted:  slices.Clone(expanded.Defaulted),
 		},
 	}, nil
 }
 
+// lastExpansion is the preset this screen expanded last, what it was given and
+// what that came to.
+//
+// The form is read on every key, and reading it on this screen expanded the
+// preset every time: 157-180 ms and 60 MB for upload-validation, which encodes
+// images to find its sizes, and 48-50 ms and 87 MB for tabular-import - while
+// the seed or the output directory was what was being typed, and neither is
+// something a preset is given (measured 2026-09-23,
+// docs/GUI-MEMORY-2026-09-23.md section 4h).
+//
+// Keyed by what Expand reads and nothing else: the preset and the values given
+// to it. The package holding it reads no clock, no randomness, no environment
+// and no disk (checked 2026-09-23), so the same preset given the same values
+// expands to the same bytes - the property eject and D11 already rest on. A
+// refusal is kept as well as an expansion, for the same reason.
+//
+// One entry, because what is typed changes one thing at a time, and a second
+// preset chosen is a new expansion whichever way it is remembered. No lock,
+// because every reading of the form happens on the window's thread - the
+// line, the live check and both presses, which read the form before a worker
+// is handed the result.
+type lastExpansion struct {
+	held  bool
+	id    string
+	given preset.Args
+	got   *preset.Expansion
+	notes []string
+	err   error
+}
+
+// of is the expansion of a preset given these values, worked out only when it
+// is not the one worked out last. The notes come with it, because working
+// them out reads the same values.
+func (l *lastExpansion) of(h Host, id string, given preset.Args) (*preset.Expansion, []string, error) {
+	if l.held && l.id == id && maps.Equal(l.given, given) {
+		return l.got, l.notes, l.err
+	}
+	tellExpanding(h)
+	got, err := preset.Expand(id, given)
+	var notes []string
+	if err == nil {
+		notes = got.Notes()
+	}
+	*l = lastExpansion{held: true, id: id, given: maps.Clone(given), got: got, notes: notes, err: err}
+	return got, notes, err
+}
+
 // engineTarget turns one recipe target into one engine target.
 //
 // The command line has the same conversion and the two cannot be shared - they
diff --git a/internal/gui/window/recipe.go b/internal/gui/window/recipe.go
index 22c409e..4d4c013 100644
--- a/internal/gui/window/recipe.go
+++ b/internal/gui/window/recipe.go
@@ -162,7 +162,7 @@ type content struct {
 // also what the single batch screen shows, so the two read as one tool.
 func NewRecipe(host Host, links ...fyne.CanvasObject) *Recipe {
 	r := &Recipe{runner: newRunner(host.Later), host: host, tips: parts.NewTips()}
-	r.runner.settle = r.settle
+	r.runner.settle = countedSettle(host, r.settle)
 	r.runner.offer.through(host)
 	// A refusal about a size belongs on the box the switch is showing.
 	r.runner.readdress = r.readdressSizeWay
diff --git a/internal/gui/window/run.go b/internal/gui/window/run.go
index 136431c..8a5e24a 100644
--- a/internal/gui/window/run.go
+++ b/internal/gui/window/run.go
@@ -291,11 +291,16 @@ func (r *runner) toneOfOutcome(res *engine.Result, runErr error) {
 
 // refreshLine works out what the form comes to and puts it on the line.
 //
-// From settle rather than from a plan: settle is what the form parses to and
-// costs nothing, and planning is what the engine does with it and can cost
-// seconds (see onPreview). A form that does not settle falls back to naming
-// the destination alone, which is read off its own box because it is the one
-// fact worth having whatever the other boxes say.
+// From settle rather than from a plan: settle is what the form parses to, and
+// planning is what the engine does with it and can cost seconds (see
+// onPreview).
+//
+// Settling is not free either, and this comment said it was until 2026-09-23.
+// On the preset screen it expands the preset, which for upload-validation
+// encodes images - 157-180 ms and 60 MB each time, measured that day
+// (docs/GUI-MEMORY-2026-09-23.md section 4h). That is why a change of a box
+// reads the form once for the line and for the box (recheck), and why the
+// preset screen remembers what it expanded last (lastExpansion).
 //
 // Not while a run owns the screen: its progress is not to be overwritten by
 // a summary, and the form is frozen then anyway.
@@ -303,12 +308,24 @@ func (r *runner) refreshLine() {
 	if r.settle == nil || r.busy.occupied {
 		return
 	}
-	dir := ""
-	if r.destination != nil {
-		dir = r.destination()
-	}
 	targets, opt, err := r.settle()
+	lineFrom(r, targets, opt, err)
+}
+
+// lineFrom puts on the line what one reading of the form came to. A form that
+// does not settle falls back to naming the destination alone, which is read
+// off its own box because it is the one fact worth having whatever the other
+// boxes say.
+//
+// Apart from refreshLine so that recheck can hand it the reading it has
+// already made. A function rather than a method, because the runner stands
+// one method under its ceiling.
+func lineFrom(r *runner, targets []engine.Target, opt engine.Options, err error) {
 	if err != nil {
+		dir := ""
+		if r.destination != nil {
+			dir = r.destination()
+		}
 		showOn(r.status, r.line.fallback(dir))
 		return
 	}
diff --git a/internal/gui/window/runrefuse.go b/internal/gui/window/runrefuse.go
index b146a91..021729d 100644
--- a/internal/gui/window/runrefuse.go
+++ b/internal/gui/window/runrefuse.go
@@ -215,11 +215,20 @@ func (r *runner) recheck(setting string) {
 	if r.busy.occupied {
 		return
 	}
+	// The form is read ONCE, for the line and for the box below. It was read
+	// twice until 2026-09-23 - through refreshLine here and again after the
+	// early return - and on the preset screen each reading expanded the
+	// preset: 271-295 ms of the window's thread for every key typed with
+	// upload-validation chosen, half of it spent working out an answer the
+	// line had just been given (docs/GUI-MEMORY-2026-09-23.md section 4h).
+	// Nothing settle reads is changed between the two places it was called,
+	// so the one reading is the answer both of them got.
+	targets, opt, err := r.settle()
 	// Whatever changed, the line says what the form comes to now - over an
 	// outcome or a preview, which described a form that no longer exists.
 	// Before the early return below, because a box emptied to be retyped
 	// changes the count as surely as a box filled in.
-	r.refreshLine()
+	lineFrom(r, targets, opt, err)
 	// Only this box, in both directions. What the other boxes were told is
 	// about values nobody has just changed, and it is still true - including
 	// the parts of it this cannot see, because a format minimum and a name
@@ -228,7 +237,6 @@ func (r *runner) recheck(setting string) {
 	if r.fields.Blank(setting) {
 		return
 	}
-	_, _, err := r.settle()
 	for _, one := range spread(err) {
 		var about interface{ AboutSetting() string }
 		if errors.As(one, &about) && r.placeOf(about.AboutSetting()) == setting {