diff --git a/build.go b/build.go
index 7fe899f..e6602d8 100644
--- a/build.go
+++ b/build.go
@@ -8,6 +8,7 @@ import (
 
 func buildCommand() *cobra.Command {
 	var imageFlag string
+	var strict bool
 
 	cmd := &cobra.Command{
 		Use:   "build <service>",
@@ -26,9 +27,9 @@ func buildCommand() *cobra.Command {
 
 			svcPath := cfg.ServicePath(svc)
 
-			version, err := runOutput(svcPath, "git", "describe", "--tags", "--always", "--dirty")
+			version, err := serviceVersion(svcPath, strict)
 			if err != nil {
-				return fmt.Errorf("git describe in %s: %w", svcPath, err)
+				return err
 			}
 			fmt.Printf("Version: %s\n", version)
 
@@ -69,5 +70,6 @@ func buildCommand() *cobra.Command {
 	}
 
 	cmd.Flags().StringVar(&imageFlag, "image", "", "build only this image")
+	cmd.Flags().BoolVar(&strict, "strict", false, "require clean git tag (no dirty tree, no commit offset)")
 	return cmd
 }
diff --git a/push.go b/push.go
index 611d0cb..dd1b262 100644
--- a/push.go
+++ b/push.go
@@ -8,6 +8,7 @@ import (
 
 func pushCommand() *cobra.Command {
 	var imageFlag string
+	var strict bool
 
 	cmd := &cobra.Command{
 		Use:   "push <service>",
@@ -26,9 +27,9 @@ func pushCommand() *cobra.Command {
 
 			svcPath := cfg.ServicePath(svc)
 
-			version, err := runOutput(svcPath, "git", "describe", "--tags", "--always", "--dirty")
+			version, err := serviceVersion(svcPath, strict)
 			if err != nil {
-				return fmt.Errorf("git describe in %s: %w", svcPath, err)
+				return err
 			}
 			fmt.Printf("Version: %s\n", version)
 
@@ -63,5 +64,6 @@ func pushCommand() *cobra.Command {
 	}
 
 	cmd.Flags().StringVar(&imageFlag, "image", "", "push only this image")
+	cmd.Flags().BoolVar(&strict, "strict", false, "require clean git tag (no dirty tree, no commit offset)")
 	return cmd
 }
diff --git a/version.go b/version.go
new file mode 100644
index 0000000..121da9c
--- /dev/null
+++ b/version.go
@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+// serviceVersion runs git describe in the service directory and returns
+// the version string. If strict is true, it rejects versions that are
+// dirty or not exactly on a tag.
+func serviceVersion(svcPath string, strict bool) (string, error) {
+	version, err := runOutput(svcPath, "git", "describe", "--tags", "--always", "--dirty")
+	if err != nil {
+		return "", fmt.Errorf("git describe in %s: %w", svcPath, err)
+	}
+
+	if strict {
+		if strings.HasSuffix(version, "-dirty") {
+			return "", fmt.Errorf("--strict: working tree is dirty (%s); commit or stash changes before building", version)
+		}
+		// git describe produces "v1.0.0-3-gabcdef" when HEAD is 3 commits past a tag.
+		// A clean tag has no hyphen after the version (except pre-release like v1.0.0-rc1,
+		// which we allow). Detect the "-N-gHASH" suffix.
+		if parts := strings.Split(version, "-"); len(parts) >= 3 {
+			// Check if second-to-last part is a number (commit count).
+			secondToLast := parts[len(parts)-2]
+			if len(secondToLast) > 0 && secondToLast[0] >= '0' && secondToLast[0] <= '9' {
+				last := parts[len(parts)-1]
+				if strings.HasPrefix(last, "g") {
+					return "", fmt.Errorf("--strict: HEAD is not on a tag (%s); create a tag before building", version)
+				}
+			}
+		}
+	}
+
+	return version, nil
+}