diff --git a/filter/bench_test.go b/filter/bench_test.go
index 9e8659e..88da7f1 100644
--- a/filter/bench_test.go
+++ b/filter/bench_test.go
@@ -111,3 +111,33 @@ func BenchmarkRegexpFilterMultiCycle(b *testing.B) {
 		}
 	}
 }
+
+// BenchmarkRegexpFilterOverlapping benchmarks the regexp filter with a query
+// that produces overlapping match ranges, exercising the mergeMatches path.
+// Each line contains repeating "aabb" patterns; the query terms "aab" and "abb"
+// produce match ranges that overlap (e.g. [0,3] and [1,4]), forcing mergeMatches
+// to be called on every line. With 10k lines the aggregate allocation difference
+// from in-place vs make([]int,2) becomes measurable.
+func BenchmarkRegexpFilterOverlapping(b *testing.B) {
+	// Build a line with many "aabb" repeats so that "aab" and "abb" each match
+	// many times with overlapping ranges between the two terms.
+	base := strings.Repeat("aabb", 20) // 80 chars
+	lines := make([]line.Line, 10_000)
+	for i := range lines {
+		lines[i] = line.NewRaw(uint64(i), base, false, false)
+	}
+
+	f := NewIgnoreCase()
+	// "aab" and "abb" share the middle "ab" in each "aabb" group, so their
+	// match ranges overlap after sorting by start position.
+	query := "aab abb"
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		ctx, cancel := context.WithTimeout(f.NewContext(context.Background(), query), 10*time.Second)
+		ch := make(chan line.Line, len(lines))
+		_ = f.Apply(ctx, lines, pipeline.ChanOutput(ch))
+		cancel()
+	}
+}
diff --git a/filter/filter.go b/filter/filter.go
index 46adc9f..f51aa7b 100644
--- a/filter/filter.go
+++ b/filter/filter.go
@@ -93,15 +93,9 @@ func matchOverlaps(a []int, b []int) bool {
 }
 
 // mergeMatches combines two overlapping match ranges into a single range
-// spanning both.
+// spanning both. It mutates and returns a to avoid a heap allocation.
 func mergeMatches(a []int, b []int) []int {
-	ret := make([]int, 2)
-
-	// Note: In practice this should never happen
-	// because we're sorting by N[0] before calling
-	// this routine, but for completeness' sake...
-	ret[0] = min(a[0], b[0])
-
-	ret[1] = max(a[1], b[1])
-	return ret
+	a[0] = min(a[0], b[0])
+	a[1] = max(a[1], b[1])
+	return a
 }
diff --git a/filter/filter_test.go b/filter/filter_test.go
index 5886bfd..2cae457 100644
--- a/filter/filter_test.go
+++ b/filter/filter_test.go
@@ -634,6 +634,31 @@ func testFuzzyMatch(octx context.Context, t *testing.T, filter Filter) {
 	}
 }
 
+func TestMergeMatches(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name string
+		a    []int
+		b    []int
+		want []int
+	}{
+		{"a before b overlapping", []int{1, 5}, []int{3, 7}, []int{1, 7}},
+		{"b before a overlapping", []int{3, 7}, []int{1, 5}, []int{1, 7}},
+		{"identical ranges", []int{2, 4}, []int{2, 4}, []int{2, 4}},
+		{"a contains b", []int{0, 10}, []int{3, 7}, []int{0, 10}},
+		{"adjacent ranges", []int{0, 3}, []int{3, 6}, []int{0, 6}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := mergeMatches(tt.a, tt.b)
+			require.Equal(t, tt.want, got)
+			// Verify in-place mutation: got should be the same slice as a
+			require.Same(t, &tt.a[0], &got[0], "mergeMatches should mutate a in place")
+		})
+	}
+}
+
 // TestMatchAcrossANSIColorBoundary verifies that filter queries match
 // against the ANSI-stripped text, so a pattern spanning characters
 // rendered in different colors still produces a match.
diff --git a/internal/util/bench_test.go b/internal/util/bench_test.go
new file mode 100644
index 0000000..bf621a6
--- /dev/null
+++ b/internal/util/bench_test.go
@@ -0,0 +1,40 @@
+package util
+
+import (
+	"fmt"
+	"testing"
+)
+
+func BenchmarkStripANSISequenceBulk(b *testing.B) {
+	b.Run("10k_plain_lines", func(b *testing.B) {
+		lines := make([]string, 10_000)
+		for i := range lines {
+			lines[i] = fmt.Sprintf("line %d: this is a typical line without any ansi codes at all padding", i)
+		}
+		b.ResetTimer()
+		b.ReportAllocs()
+		for b.Loop() {
+			for _, l := range lines {
+				StripANSISequence(l)
+			}
+		}
+	})
+
+	b.Run("10k_mixed_95pct_plain", func(b *testing.B) {
+		lines := make([]string, 10_000)
+		for i := range lines {
+			if i%20 == 0 {
+				lines[i] = fmt.Sprintf("\x1b[31mline %d\x1b[0m: this has ansi codes in it for color", i)
+			} else {
+				lines[i] = fmt.Sprintf("line %d: this is a typical line without any ansi codes at all padding", i)
+			}
+		}
+		b.ResetTimer()
+		b.ReportAllocs()
+		for b.Loop() {
+			for _, l := range lines {
+				StripANSISequence(l)
+			}
+		}
+	})
+}
diff --git a/internal/util/util.go b/internal/util/util.go
index 61e34da..3576e18 100644
--- a/internal/util/util.go
+++ b/internal/util/util.go
@@ -3,6 +3,7 @@ package util
 import (
 	"errors"
 	"regexp"
+	"strings"
 	"unicode"
 )
 
@@ -44,8 +45,13 @@ func ContainsUpper(query string) bool {
 // Global var used to strips ansi sequences
 var reANSIEscapeChars = regexp.MustCompile("\x1B\\[(?:[0-9]{1,2}(?:;[0-9]{1,2})?)*[a-zA-Z]")
 
-// StripANSISequence strips ANSI escape sequences from the given string
+// StripANSISequence strips ANSI escape sequences from the given string.
+// Fast-path: if the string contains no ESC byte, return it unchanged
+// to avoid a regexp allocation.
 func StripANSISequence(s string) string {
+	if !strings.Contains(s, "\x1b") {
+		return s
+	}
 	return reANSIEscapeChars.ReplaceAllString(s, "")
 }
 
diff --git a/line/bench_test.go b/line/bench_test.go
index 8b86738..ceabf2c 100644
--- a/line/bench_test.go
+++ b/line/bench_test.go
@@ -45,3 +45,32 @@ func BenchmarkMatchedLifecycle(b *testing.B) {
 		}
 	})
 }
+
+// BenchmarkNewRawAndDisplay benchmarks creating Raw lines and calling
+// DisplayString(), simulating peco's startup + render path for 10k lines.
+func BenchmarkNewRawAndDisplay(b *testing.B) {
+	texts := make([]string, 10_000)
+	for i := range texts {
+		texts[i] = fmt.Sprintf("line %d: this is a typical plain text line without any ansi codes", i)
+	}
+
+	b.Run("enableANSI_true_plain_text", func(b *testing.B) {
+		b.ReportAllocs()
+		for b.Loop() {
+			for i, t := range texts {
+				r := NewRaw(uint64(i), t, false, true)
+				_ = r.DisplayString()
+			}
+		}
+	})
+
+	b.Run("enableANSI_false_plain_text", func(b *testing.B) {
+		b.ReportAllocs()
+		for b.Loop() {
+			for i, t := range texts {
+				r := NewRaw(uint64(i), t, false, false)
+				_ = r.DisplayString()
+			}
+		}
+	})
+}
diff --git a/line/raw.go b/line/raw.go
index 5124bc9..74ad146 100644
--- a/line/raw.go
+++ b/line/raw.go
@@ -77,8 +77,12 @@ func NewRaw(id uint64, v string, enableSep bool, enableANSI bool) *Raw {
 			src = rl.buf[:rl.sepLoc]
 		}
 		r := ansi.Parse(src)
-		rl.displayString = r.Stripped
 		rl.ansiAttrs = r.Attrs
+		// Only store displayString when it actually differs from buf
+		// (i.e. when there's a separator or ANSI attributes)
+		if rl.sepLoc > -1 || r.Attrs != nil {
+			rl.displayString = r.Stripped
+		}
 	}
 
 	return rl
@@ -121,10 +125,10 @@ func (rl *Raw) DisplayString() string {
 
 	if i := rl.sepLoc; i > -1 {
 		rl.displayString = util.StripANSISequence(rl.buf[:i])
-	} else {
-		rl.displayString = util.StripANSISequence(rl.buf)
+		return rl.displayString
 	}
-	return rl.displayString
+	// No separator: strip ANSI (fast-path returns buf unchanged when no ESC present)
+	return util.StripANSISequence(rl.buf)
 }
 
 // ANSIAttrs returns the run-length encoded ANSI attributes for this line.