diff --git a/include/cli.h b/include/cli.h
index 663f432..e54ae0b 100644
--- a/include/cli.h
+++ b/include/cli.h
@@ -3,7 +3,20 @@
 #include "pch.h"
 
 namespace crib::cli {
+struct Command {
+  void (*run)(std::vector<std::string>);
+  std::string (*summary)();
+  void (*help)();
+};
+
+struct cli_error : std::runtime_error {
+  int exit_code;
+  cli_error(std::string msg, int code)
+      : std::runtime_error(std::move(msg)), exit_code(code) {}
+};
+
 extern bool use_colors;
 void help();
+int execute(const std::string &name, const Command &cmd, int argc, char *argv[]);
 int run(int argc, char *argv[]);
 } // namespace crib::cli
diff --git a/include/commands/ed/ed.h b/include/commands/ed/ed.h
index 47d0f90..03ba39f 100644
--- a/include/commands/ed/ed.h
+++ b/include/commands/ed/ed.h
@@ -6,5 +6,5 @@
 namespace crib::commands::ed {
 std::string summary();
 void help();
-void run(int argc, char *argv[]);
+void run(std::vector<std::string>);
 } // namespace crib::commands::ed
diff --git a/include/internal/vase/iterators/line.h b/include/internal/vase/iterators/line.h
index efb848a..4e703a4 100644
--- a/include/internal/vase/iterators/line.h
+++ b/include/internal/vase/iterators/line.h
@@ -19,4 +19,56 @@ struct LineIterator {
   bool next(std::string *line);
   uint64_t byte_offset();
 };
+
+struct Iterator {
+  Shard *root;
+  std::string line;
+
+  Iterator(Shard *root, uint64_t line_num)
+      : root(root), it(root, line_num, Direction::Forward) {
+    Shard::retain(root);
+  }
+
+  ~Iterator() {
+    Shard::release(root);
+  }
+
+  Iterator(const Iterator &other)
+      : root(other.root), it(other.it) {
+    Shard::retain(root);
+  }
+
+  Iterator &operator=(const Iterator &other) {
+    if (this != &other) {
+      Shard::retain(other.root);
+      Shard::release(root);
+      root = other.root;
+      it = other.it;
+    }
+    return *this;
+  }
+
+  Iterator(Iterator &&other) noexcept
+      : root(other.root), it(std::move(other.it)) {
+    other.root = nullptr;
+  }
+
+  Iterator &operator=(Iterator &&other) noexcept {
+    if (this != &other) {
+      Shard::release(root);
+      root = other.root;
+      it = std::move(other.it);
+      other.root = nullptr;
+    }
+    return *this;
+  }
+
+  std::string &next() {
+    it.next(&line);
+    return line;
+  }
+
+private:
+  LineIterator it;
+};
 } // namespace crib::internal::vase
diff --git a/include/internal/vase/vase.h b/include/internal/vase/vase.h
index 7fe03bc..6a6f116 100644
--- a/include/internal/vase/vase.h
+++ b/include/internal/vase/vase.h
@@ -53,9 +53,7 @@ struct Vase {
   std::string to_string();
   std::string to_string(Range range);
 
-  Point resolve_column(uint64_t line, uint64_t column);
-
-  LineIterator iterate(uint64_t line);
+  Iterator iterate(uint64_t line);
 
   void insert(Point *point, char key);
   void insert(Point *point, const char *data, uint64_t len);
diff --git a/src/cli/cli.cc b/src/cli/cli.cc
index 82649ff..5bcb045 100644
--- a/src/cli/cli.cc
+++ b/src/cli/cli.cc
@@ -2,18 +2,6 @@
 #include "commands/ed/ed.h"
 
 namespace crib::cli {
-struct Command {
-  void (*run)(int, char **);
-  std::string (*summary)();
-  void (*help)();
-};
-
-struct cli_error : std::runtime_error {
-  int exit_code;
-  cli_error(std::string msg, int code)
-      : std::runtime_error(std::move(msg)), exit_code(code) {}
-};
-
 static const std::unordered_map<std::string, Command> commands = {
   {"ed",
    {crib::commands::ed::run,
@@ -45,9 +33,10 @@ void help() {
     std::cout << "  " << name << " - " << cmd.summary() << "\n";
 }
 
-int execute(const std::string &name, const Command &cmd, int argc, char **argv) {
+int execute(const std::string &name, const Command &cmd, int argc, char *argv[]) {
   try {
-    cmd.run(argc - 1, argv + 1);
+    std::vector<std::string> args(argv, argv + argc);
+    cmd.run(args);
     return 0;
   } catch (const cli_error &e) {
     std::cerr << "Error running " << name << ": " << e.what() << '\n';
@@ -69,7 +58,7 @@ int run(int argc, char *argv[]) {
 
   if (argc > 1)
     if (auto it = commands.find(argv[1]); it != commands.end())
-      return execute(it->first, it->second, argc, argv);
+      return execute(it->first, it->second, argc - 1, argv + 1);
 
   if (argc > 1 && std::string(argv[1]) == "--help") {
     help();
diff --git a/src/commands/ed/ed.cc b/src/commands/ed/ed.cc
index 32b983c..2376dba 100644
--- a/src/commands/ed/ed.cc
+++ b/src/commands/ed/ed.cc
@@ -5,7 +5,7 @@ std::string summary() {
   return "A POSIX-compliant line editor.";
 }
 void help() {}
-void run(int, char *[]) {
+void run(std::vector<std::string> args) {
   return;
 }
 } // namespace crib::commands::ed
diff --git a/src/internal/vase/vase.cc b/src/internal/vase/vase.cc
index de19143..1eafa63 100644
--- a/src/internal/vase/vase.cc
+++ b/src/internal/vase/vase.cc
@@ -55,8 +55,8 @@ std::string Vase::to_string(Range range) {
   return out;
 }
 
-LineIterator Vase::iterate(uint64_t line) {
-  return LineIterator(root, line, Direction::Forward);
+Iterator Vase::iterate(uint64_t line) {
+  return Iterator(root, line);
 }
 
 bool Vase::undo() {