diff --git a/src/mutator/base.ts b/src/mutator/base.ts
new file mode 100644
index 0000000..5cd6e11
--- /dev/null
+++ b/src/mutator/base.ts
@@ -0,0 +1,11 @@
+export abstract class Mutator {
+  /**
+   * Override to add guard conditions.  Called before {@link execute}.
+   * Defaults to `true` — the mutator always runs.
+   */
+  async shouldExecute(): Promise<boolean> {
+    return true;
+  }
+
+  abstract execute(): Promise<Boolean>;
+}
diff --git a/src/mutator/types.ts b/src/mutator/types.ts
new file mode 100644
index 0000000..7e0e74f
--- /dev/null
+++ b/src/mutator/types.ts
@@ -0,0 +1,8 @@
+export type MutatorName =
+  | "npm"
+  | "claude"
+  | "locker"
+  | "branch"
+  | "repository"
+  | "ssh"
+  | "ssm";