diff --git a/.changeset/brave-roots-count.md b/.changeset/brave-roots-count.md
new file mode 100644
index 0000000..7322a13
--- /dev/null
+++ b/.changeset/brave-roots-count.md
@@ -0,0 +1,5 @@
+---
+'@bomb.sh/tab': patch
+---
+
+fix: stop completing a root command argument again after it has been given
diff --git a/src/t.ts b/src/t.ts
index b22cd9c..5126abd 100644
--- a/src/t.ts
+++ b/src/t.ts
@@ -351,8 +351,8 @@ export class RootCommand extends Command {
   private handlePositionalCompletion(command: Command, previousArgs: string[]) {
     // Strip options so flags don't inflate the positional index
     const strippedArgs = this.stripOptions(previousArgs);
-    // current argument position (subtract command name)
-    const commandParts = command.value.split(' ').length;
+    // current argument position (subtract command name; the root has none)
+    const commandParts = command === this ? 0 : command.value.split(' ').length;
     const currentArgIndex = Math.max(0, strippedArgs.length - commandParts);
     const argumentEntries = Array.from(command.arguments.entries());
 
diff --git a/tests/cli.test.ts b/tests/cli.test.ts
index 742a509..e46c43b 100644
--- a/tests/cli.test.ts
+++ b/tests/cli.test.ts
@@ -251,6 +251,12 @@ describe.each(cliTools)('cli completion tests for %s', (cliTool) => {
       const output = await runCommand(command);
       expect(output).toMatchSnapshot();
     });
+
+    it('should not complete root command project argument again after it is given', async () => {
+      const command = `${commandPrefix} my-app ""`;
+      const output = await runCommand(command);
+      expect(output).toBe(':4\n');
+    });
   });
 
   describe('root command option tests', () => {