fix: VSCode desktop connection (#7120)

Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>

agent/agent.go

@@ -1407,5 +1407,14 @@ func expandDirectory(dir string) (string, error) {
 		}
 		dir = filepath.Join(home, dir[1:])
 	}
-	return os.ExpandEnv(dir), nil
+	dir = os.ExpandEnv(dir)
+
+	if !filepath.IsAbs(dir) {
+		home, err := userHomeDir()
+		if err != nil {
+			return "", err
+		}
+		dir = filepath.Join(home, dir)
+	}
+	return dir, nil
 }

agent/agent_test.go

@@ -1391,6 +1391,22 @@ func TestAgent_Startup(t *testing.T) {
 		require.Equal(t, homeDir, client.getStartup().ExpandedDirectory)
 	})
 
+	t.Run("NotAbsoluteDirectory", func(t *testing.T) {
+		t.Parallel()
+
+		_, client, _, _, _ := setupAgent(t, agentsdk.Manifest{
+			StartupScript:        "true",
+			StartupScriptTimeout: 30 * time.Second,
+			Directory:            "coder/coder",
+		}, 0)
+		assert.Eventually(t, func() bool {
+			return client.getStartup().Version != ""
+		}, testutil.WaitShort, testutil.IntervalFast)
+		homeDir, err := os.UserHomeDir()
+		require.NoError(t, err)
+		require.Equal(t, filepath.Join(homeDir, "coder/coder"), client.getStartup().ExpandedDirectory)
+	})
+
 	t.Run("HomeEnvironmentVariable", func(t *testing.T) {
 		t.Parallel()