diff --git a/Makefile b/Makefile
index 9666920..d311783 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 build: clean
 	@echo "======================== Building Binary ======================="
 	minify wfa.js > dist/wfa.js
-	GOOS=js GOARCH=wasm CGO_ENABLED=0 tinygo build -no-debug -opt=2 -target=wasm -o dist/wfa.wasm .
+	GOOS=js GOARCH=wasm CGO_ENABLED=0 tinygo build -panic=trap -no-debug -opt=2 -target=wasm -o dist/wfa.wasm .
 
 clean:
 	@echo "======================== Cleaning Project ======================"
diff --git a/main.go b/main.go
index 35cd236..a552e0f 100644
--- a/main.go
+++ b/main.go
@@ -9,6 +9,7 @@ import (
 func main() {
 	c := make(chan bool)
 	js.Global().Set("wfAlign", js.FuncOf(wfAlign))
+	js.Global().Set("DecodeCIGAR", js.FuncOf(DecodeCIGAR))
 	<-c
 }
 
@@ -70,3 +71,21 @@ func wfAlign(this js.Value, args []js.Value) interface{} {
 
 	return js.ValueOf(resultMap)
 }
+
+func DecodeCIGAR(this js.Value, args []js.Value) interface{} {
+	if len(args) != 1 {
+		fmt.Println("invalid number of args, requires 1: CIGAR")
+		return nil
+	}
+
+	if args[0].Type() != js.TypeString {
+		fmt.Println("s1 should be a string")
+		return nil
+	}
+
+	CIGAR := args[0].String()
+
+	decoded := wfa.RunLengthDecode(CIGAR)
+
+	return js.ValueOf(decoded)
+}
diff --git a/pkg/types.go b/pkg/types.go
index e7733b5..431c152 100644
--- a/pkg/types.go
+++ b/pkg/types.go
@@ -39,10 +39,10 @@ func PackWavefrontValue(value uint32, traceback Traceback) WavefrontValue {
 }
 
 // UnpackWavefrontValue: opens a WavefrontValue into a valid bool, diag value and traceback
-func UnpackWavefrontValue(wf WavefrontValue) (bool, uint32, Traceback) {
-	valueBM := uint32(wf & 0x0FFF_FFFF)
-	tracebackBM := uint8(wf & 0x7000_0000 >> 28)
-	validBM := wf&0x8000_0000 != 0
+func UnpackWavefrontValue(wfv WavefrontValue) (bool, uint32, Traceback) {
+	valueBM := uint32(wfv & 0x0FFF_FFFF)
+	tracebackBM := uint8(wfv & 0x7000_0000 >> 28)
+	validBM := wfv&0x8000_0000 != 0
 	return validBM, valueBM, Traceback(tracebackBM)
 }
 
diff --git a/pkg/utils.go b/pkg/utils.go
index a806159..2971f0a 100644
--- a/pkg/utils.go
+++ b/pkg/utils.go
@@ -2,11 +2,55 @@ package wfa
 
 import (
 	"math"
-	"unicode/utf8"
+	"strings"
 
 	"golang.org/x/exp/constraints"
 )
 
+func UIntToString(num uint) string { // num assumed to be positive
+	var builder strings.Builder
+
+	for num > 0 {
+		digit := num % 10
+		builder.WriteRune(rune('0' + digit))
+		num /= 10
+	}
+
+	// Reverse the string as we built it in reverse order
+	str := []rune(builder.String())
+	for i, j := 0, len(str)-1; i < j; i, j = i+1, j-1 {
+		str[i], str[j] = str[j], str[i]
+	}
+
+	return string(str)
+}
+
+func RunLengthDecode(encoded string) string {
+	decoded := strings.Builder{}
+	length := len(encoded)
+	i := 0
+
+	for i < length {
+		// If the current character is a digit, we need to extract the run length
+		runLength := 0
+		for i < length && encoded[i] >= '0' && encoded[i] <= '9' {
+			runLength = runLength*10 + int(encoded[i]-'0')
+			i++
+		}
+
+		// The next character will be the character to repeat
+		if i < length {
+			char := encoded[i]
+			for j := 0; j < runLength; j++ {
+				decoded.WriteByte(char)
+			}
+			i++ // Move past the character
+		}
+	}
+
+	return decoded.String()
+}
+
 func SafeMin[T constraints.Integer](values []T, idx int) T {
 	return values[idx]
 }
@@ -51,21 +95,6 @@ func SafeArgMin[T constraints.Integer](valids []bool, values []T) (bool, int) {
 	}
 }
 
-func Reverse(s string) string {
-	size := len(s)
-	buf := make([]byte, size)
-	for start := 0; start < size; {
-		r, n := utf8.DecodeRuneInString(s[start:])
-		start += n
-		utf8.EncodeRune(buf[size-start:], r)
-	}
-	return string(buf)
-}
-
-func Splice(s string, c rune, idx int) string {
-	return s[:idx] + string(c) + s[idx:]
-}
-
 func NextLoHi(M WavefrontComponent, I WavefrontComponent, D WavefrontComponent, score int, penalties Penalty) (int, int) {
 	x := penalties.X
 	o := penalties.O
@@ -117,11 +146,8 @@ func NextD(M WavefrontComponent, D WavefrontComponent, score int, k int, penalti
 	a_ok, a, _ := M.GetVal(score-o-e, k+1)
 	b_ok, b, _ := D.GetVal(score-e, k+1)
 
-	ok, nextDTraceback := SafeArgMax(
-		[]bool{a_ok, b_ok},
-		[]uint32{a, b},
-	)
-	nextDVal := SafeMax([]uint32{a, b}, nextDTraceback) // nothing special
+	ok, nextDTraceback := SafeArgMax([]bool{a_ok, b_ok}, []uint32{a, b})
+	nextDVal := SafeMax([]uint32{a, b}, nextDTraceback)
 	if ok {
 		D.SetVal(score, k, nextDVal, []Traceback{OpenDel, ExtdDel}[nextDTraceback])
 	}
@@ -137,7 +163,6 @@ func NextM(M WavefrontComponent, I WavefrontComponent, D WavefrontComponent, sco
 
 	ok, nextMTraceback := SafeArgMax([]bool{a_ok, b_ok, c_ok}, []uint32{a, b, c})
 	nextMVal := SafeMax([]uint32{a, b, c}, nextMTraceback)
-
 	if ok {
 		M.SetVal(score, k, nextMVal, []Traceback{Sub, Ins, Del}[nextMTraceback])
 	}
diff --git a/pkg/wfa.go b/pkg/wfa.go
index 1bc52d5..b716cbb 100644
--- a/pkg/wfa.go
+++ b/pkg/wfa.go
@@ -1,5 +1,9 @@
 package wfa
 
+import (
+	"strings"
+)
+
 func WFAlign(s1 string, s2 string, penalties Penalty, doCIGAR bool) Result {
 	n := len(s1)
 	m := len(s2)
@@ -25,7 +29,7 @@ func WFAlign(s1 string, s2 string, penalties Penalty, doCIGAR bool) Result {
 
 	CIGAR := ""
 	if doCIGAR {
-		CIGAR = WFBacktrace(M, I, D, score, penalties, A_k, s1, s2)
+		CIGAR = WFBacktrace(M, I, D, score, penalties, A_k, A_offset, s1, s2)
 	}
 
 	return Result{
@@ -67,76 +71,128 @@ func WFNext(M WavefrontComponent, I WavefrontComponent, D WavefrontComponent, sc
 	}
 }
 
-func WFBacktrace(M WavefrontComponent, I WavefrontComponent, D WavefrontComponent, score int, penalties Penalty, A_k int, s1 string, s2 string) string {
-	traceback_CIGAR := []string{"I", "I", "D", "D", "X", "", "", ""}
+func WFBacktrace(M WavefrontComponent, I WavefrontComponent, D WavefrontComponent, score int, penalties Penalty, A_k int, A_offset uint32, s1 string, s2 string) string {
 	x := penalties.X
 	o := penalties.O
 	e := penalties.E
-	CIGAR_rev := ""
+
 	tb_s := score
 	tb_k := A_k
-	_, _, current_traceback := M.GetVal(tb_s, tb_k)
 	done := false
 
+	_, current_dist, current_traceback := M.GetVal(tb_s, tb_k)
+
+	Ops := []rune{'~'}
+	Counts := []uint{0}
+	idx := 0
+
 	for !done {
-		CIGAR_rev = CIGAR_rev + traceback_CIGAR[current_traceback]
 		switch current_traceback {
 		case OpenIns:
+			if Ops[idx] == 'I' {
+				Counts[idx]++
+			} else {
+				Ops = append(Ops, 'I')
+				Counts = append(Counts, 1)
+				idx++
+			}
+
 			tb_s = tb_s - o - e
 			tb_k = tb_k - 1
-			_, _, current_traceback = M.GetVal(tb_s, tb_k)
+			_, current_dist, current_traceback = M.GetVal(tb_s, tb_k)
 		case ExtdIns:
+			if Ops[idx] == 'I' {
+				Counts[idx]++
+			} else {
+				Ops = append(Ops, 'I')
+				Counts = append(Counts, 1)
+				idx++
+			}
+
 			tb_s = tb_s - e
 			tb_k = tb_k - 1
-			_, _, current_traceback = I.GetVal(tb_s, tb_k)
+			_, current_dist, current_traceback = I.GetVal(tb_s, tb_k)
 		case OpenDel:
+			if Ops[idx] == 'D' {
+				Counts[idx]++
+			} else {
+				Ops = append(Ops, 'D')
+				Counts = append(Counts, 1)
+				idx++
+			}
+
 			tb_s = tb_s - o - e
 			tb_k = tb_k + 1
-			_, _, current_traceback = M.GetVal(tb_s, tb_k)
+			_, current_dist, current_traceback = M.GetVal(tb_s, tb_k)
 		case ExtdDel:
+			if Ops[idx] == 'D' {
+				Counts[idx]++
+			} else {
+				Ops = append(Ops, 'D')
+				Counts = append(Counts, 1)
+				idx++
+			}
+
 			tb_s = tb_s - e
 			tb_k = tb_k + 1
-			_, _, current_traceback = D.GetVal(tb_s, tb_k)
+			_, current_dist, current_traceback = D.GetVal(tb_s, tb_k)
 		case Sub:
 			tb_s = tb_s - x
 			// tb_k = tb_k;
-			_, _, current_traceback = M.GetVal(tb_s, tb_k)
+			_, next_dist, next_traceback := M.GetVal(tb_s, tb_k)
+
+			if int(current_dist-next_dist)-1 > 0 {
+				Ops = append(Ops, 'M')
+				Counts = append(Counts, uint(current_dist-next_dist)-1)
+				idx++
+			}
+
+			if Ops[idx] == 'X' {
+				Counts[idx]++
+			} else {
+				Ops = append(Ops, 'X')
+				Counts = append(Counts, 1)
+				idx++
+			}
+
+			current_dist = next_dist
+			current_traceback = next_traceback
 		case Ins:
 			// tb_s = tb_s;
 			// tb_k = tb_k;
-			_, _, current_traceback = I.GetVal(tb_s, tb_k)
+			_, next_dist, next_traceback := I.GetVal(tb_s, tb_k)
+
+			Ops = append(Ops, 'M')
+			Counts = append(Counts, uint(current_dist-next_dist))
+			idx++
+
+			current_dist = next_dist
+			current_traceback = next_traceback
 		case Del:
 			// tb_s = tb_s;
 			// tb_k = tb_k;
-			_, _, current_traceback = D.GetVal(tb_s, tb_k)
+			_, next_dist, next_traceback := D.GetVal(tb_s, tb_k)
+
+			Ops = append(Ops, 'M')
+			Counts = append(Counts, uint(current_dist-next_dist))
+			idx++
+
+			current_dist = next_dist
+			current_traceback = next_traceback
 		case End:
+			Ops = append(Ops, 'M')
+			Counts = append(Counts, uint(current_dist))
+			idx++
+
 			done = true
 		}
 	}
 
-	CIGAR_part := Reverse(CIGAR_rev)
-	c := 0
-	i := 0
-	j := 0
-	for i < len(s1) && j < len(s2) {
-		if s1[i] == s2[j] {
-			//CIGAR_part.splice(c, 0, "M")
-			CIGAR_part = Splice(CIGAR_part, 'M', c)
-			c++
-			i++
-			j++
-		} else if CIGAR_part[c] == 'X' {
-			c++
-			i++
-			j++
-		} else if CIGAR_part[c] == 'I' {
-			c++
-			j++
-		} else if CIGAR_part[c] == 'D' {
-			c++
-			i++
-		}
+	CIGAR := strings.Builder{}
+	for i := len(Ops) - 1; i > 0; i-- {
+		CIGAR.WriteString(UIntToString(Counts[i]))
+		CIGAR.WriteRune(Ops[i])
 	}
 
-	return CIGAR_part
+	return CIGAR.String()
 }
diff --git a/test/wfa_test.go b/test/wfa_test.go
index 5107b66..7fdee7d 100644
--- a/test/wfa_test.go
+++ b/test/wfa_test.go
@@ -3,6 +3,7 @@ package tests
 import (
 	"bufio"
 	"encoding/json"
+	"log"
 	"math/rand/v2"
 	"os"
 	"strconv"
@@ -46,6 +47,71 @@ func TestWavefrontPacking(t *testing.T) {
 	}
 }
 
+func GetScoreFromCIGAR(CIGAR string, penalties wfa.Penalty) int {
+	unpackedCIGAR := wfa.RunLengthDecode(CIGAR)
+	previousOp := '~'
+	score := 0
+	for _, Op := range unpackedCIGAR {
+		if Op == 'M' {
+			score = score + penalties.M
+		} else if Op == 'X' {
+			score = score + penalties.X
+		} else if (Op == 'I' && previousOp != 'I') || (Op == 'D' && previousOp != 'D') {
+			score = score + penalties.O + penalties.E
+		} else if (Op == 'I' && previousOp == 'I') || (Op == 'D' && previousOp == 'D') {
+			score = score + penalties.E
+		}
+		previousOp = Op
+	}
+	return score
+}
+
+func CheckCIGARCorrectness(s1 string, s2 string, CIGAR string) bool {
+	unpackedCIGAR := wfa.RunLengthDecode(CIGAR)
+	i := 0
+	j := 0
+
+	s1Aligned := strings.Builder{}
+	alignment := strings.Builder{}
+	s2Aligned := strings.Builder{}
+
+	for c := 0; c < len(unpackedCIGAR); c++ {
+		Op := unpackedCIGAR[c]
+		if Op == 'M' {
+			s1Aligned.WriteByte(s1[i])
+			alignment.WriteRune('|')
+			s2Aligned.WriteByte(s2[j])
+			i++
+			j++
+		} else if Op == 'X' {
+			s1Aligned.WriteByte(s1[i])
+			alignment.WriteRune(' ')
+			s2Aligned.WriteByte(s2[j])
+			i++
+			j++
+		} else if Op == 'I' {
+
+			s1Aligned.WriteRune('-')
+			alignment.WriteRune(' ')
+			s2Aligned.WriteByte(s2[j])
+
+			j++
+		} else if Op == 'D' {
+			s1Aligned.WriteByte(s1[i])
+			alignment.WriteRune('|')
+			s2Aligned.WriteRune('-')
+			i++
+		}
+	}
+
+	if i == len(s1) && j == len(s2) {
+		return true
+	} else {
+		log.Printf("\n%s\n%s\n%s\n i=%d, j=%d, |s1|=%d, |s2|=%d\n", s1Aligned.String(), alignment.String(), s2Aligned.String(), i, j, len(s1), len(s2))
+		return false
+	}
+}
+
 func TestWFA(t *testing.T) {
 	content, _ := os.ReadFile(testJsonPath)
 
@@ -73,7 +139,9 @@ func TestWFA(t *testing.T) {
 
 		for solutions.Scan() {
 			solution := solutions.Text()
+
 			expectedScore, _ := strconv.Atoi(strings.Split(solution, "\t")[0])
+			expectedCIGAR := strings.Split(solution, "\t")[1]
 
 			sequences.Scan()
 			s1 := sequences.Text()
@@ -85,9 +153,25 @@ func TestWFA(t *testing.T) {
 
 			x := wfa.WFAlign(s1, s2, testPenalties, true)
 			gotScore := x.Score
+			gotCIGAR := x.CIGAR
 
 			if gotScore != -1*expectedScore {
-				t.Errorf(`test: %s#%d, s1: %s, s2: %s, got: %d, expected: %d\n`, testName, idx, s1, s2, gotScore, expectedScore)
+				t.Errorf(`test: %s#%d, s1: %s, s2: %s, got: %d, expected: %d`, testName, idx, s1, s2, gotScore, expectedScore)
+				os.Exit(1)
+			}
+
+			if gotCIGAR != expectedCIGAR {
+				checkScore := GetScoreFromCIGAR(gotCIGAR, testPenalties)
+				CIGARCorrectness := CheckCIGARCorrectness(s1, s2, gotCIGAR)
+				if checkScore != gotScore && checkScore != -1*expectedScore { // nonequivalent alignment
+					t.Errorf(`test: %s#%d, s1: %s, s2: %s, got: [%s], expected: [%s]`, testName, idx, s1, s2, gotCIGAR, expectedCIGAR)
+					t.Errorf(`test: %s#%d, recalculated score: %d`, testName, idx, checkScore)
+					os.Exit(1)
+				}
+				if !CIGARCorrectness {
+					t.Errorf(`test: %s#%d, s1: %s, s2: %s, got: [%s], expected: [%s]`, testName, idx, s1, s2, gotCIGAR, expectedCIGAR)
+					os.Exit(1)
+				}
 			}
 
 			idx++