fix prerelease channel normalisation

cmd.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"runtime"
-	"strings"
 
 	"forge.lthn.ai/core/cli/pkg/cli"
 	"github.com/spf13/cobra"
@@ -46,7 +45,7 @@ Examples:
 		RunE: runUpdate,
 	}
 
-	updateCmd.PersistentFlags().StringVar(&updateChannel, "channel", "stable", "Release channel: stable, beta, alpha, or dev")
+	updateCmd.PersistentFlags().StringVar(&updateChannel, "channel", "stable", "Release channel: stable, beta, alpha, prerelease, or dev")
 	updateCmd.PersistentFlags().BoolVar(&updateForce, "force", false, "Force update even if already on latest version")
 	updateCmd.Flags().BoolVar(&updateCheck, "check", false, "Only check for updates, do not apply")
 	updateCmd.Flags().IntVar(&updateWatchPID, "watch-pid", 0, "Internal: watch for parent PID to die then restart")
@@ -73,7 +72,7 @@ func runUpdate(cmd *cobra.Command, args []string) error {
 	}
 
 	currentVersion := cli.AppVersion
-	normalizedChannel := strings.TrimSpace(strings.ToLower(updateChannel))
+	normalizedChannel := normaliseGitHubChannel(updateChannel)
 
 	cli.Print("%s %s\n", cli.DimStyle.Render("Current version:"), cli.ValueStyle.Render(currentVersion))
 	cli.Print("%s %s/%s\n", cli.DimStyle.Render("Platform:"), runtime.GOOS, runtime.GOARCH)

service.go

@@ -30,7 +30,8 @@ type UpdateServiceConfig struct {
 	// repository URL (e.g., "https://github.com/owner/repo") or a base URL
 	// for a generic HTTP update server.
 	RepoURL string
-	// Channel specifies the release channel to track (e.g., "stable", "prerelease").
+	// Channel specifies the release channel to track (e.g., "stable", "beta", or "prerelease").
+	// "prerelease" is normalised to "beta" to match the GitHub release filter.
 	// This is only used for GitHub-based updates.
 	Channel string
 	// CheckOnStartup determines the update behavior when the service starts.
@@ -134,5 +135,8 @@ func normaliseGitHubChannel(channel string) string {
 	if channel == "" {
 		return "stable"
 	}
+	if channel == "prerelease" {
+		return "beta"
+	}
 	return channel
 }

service_test.go

@@ -38,6 +38,15 @@ func TestNewUpdateService(t *testing.T) {
 			isGitHub:    true,
 			wantChannel: "beta",
 		},
+		{
+			name: "GitHub prerelease channel maps to beta",
+			config: UpdateServiceConfig{
+				RepoURL: "https://github.com/owner/repo",
+				Channel: " prerelease ",
+			},
+			isGitHub:    true,
+			wantChannel: "beta",
+		},
 		{
 			name: "Invalid GitHub URL",
 			config: UpdateServiceConfig{