diff --git a/main.go b/main.go
index d9ee8873a467b99fbafdbe2e56db8035e0b5ec79..30e4975fdd84e0e6f097b5b081710edfa49a3162 100644
--- a/main.go
+++ b/main.go
@@ -6,8 +6,10 @@ package main
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"runtime/debug"
+	"strings"
 
 	"github.com/charmbracelet/fang"
 	"github.com/spf13/cobra"
@@ -47,11 +49,12 @@ formatted-commit -t refactor -s "web/git-bug" -m "fancy shmancy" \
   -b "Had to do a weird thing because..."
 `,
 	RunE: func(cmd *cobra.Command, args []string) error {
-		// TODO: Implement commit formatting logic here
-		// 1. Validate subject length (type(scope): message <= 50 chars)
-		// 2. Format body as Markdown wrapped to 72 columns
-		// 3. Validate and format trailers
-		// 4. Pipe result to `git commit -F -`
+		subject, err := buildAndValidateSubject(commitType, scope, message, breakingChange)
+		if err != nil {
+			return err
+		}
+
+		_ = subject
 
 		return nil
 	},
@@ -73,6 +76,36 @@ func init() {
 	}
 }
 
+func buildAndValidateSubject(commitType, scope, message string, breaking bool) (string, error) {
+	var subject strings.Builder
+
+	subject.WriteString(commitType)
+
+	if scope != "" {
+		subject.WriteString("(")
+		subject.WriteString(scope)
+		subject.WriteString(")")
+	}
+
+	if breaking {
+		subject.WriteString("!")
+	}
+
+	subject.WriteString(": ")
+	subject.WriteString(message)
+
+	result := subject.String()
+	length := len(result)
+
+	if length > 50 {
+		exceededBy := length - 50
+		truncated := result[:50] + "…"
+		return "", fmt.Errorf("subject exceeds 50 character limit by %d:\n%s", exceededBy, truncated)
+	}
+
+	return result, nil
+}
+
 func main() {
 	ctx := context.Background()