fix(builder): use a local node-agent image when it can't be pulled

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/agentboot.go

@@ -21,6 +21,20 @@ func agentImageFromEnv() string {
 	return defaultAgentImage
 }
 
+// pullAgentImage fetches the latest node-agent image. A copy that is only local (a test build) is used as
+// it is.
+func pullAgentImage(img string) error {
+	out, err := runCmd("docker", "pull", "-q", img)
+	if err == nil {
+		return nil
+	}
+	if _, inspectErr := runCmd("docker", "image", "inspect", img); inspectErr == nil {
+		fmt.Printf("[agent] could not pull %s (%s); using the local copy\n", img, firstLine(out))
+		return nil
+	}
+	return fmt.Errorf("docker pull %s: %v: %s", img, err, out)
+}
+
 // runAgentBootTest deploys a payload with BootTest and returns its output; passed is its verdict.
 func runAgentBootTest(payload map[string]any, agentImage string) (output string, passed bool, err error) {
 	container := fmt.Sprint(payload["containerName"])

cmd/gbrgames/build.go

@@ -255,8 +255,8 @@ func firstBoot(name, image, steamApp string, steam bool, startup string) (*bootR
 // bootCheck deploys the template with the node-agent's BootTest, the same check CI runs, and when the
 // game wrote files outside its volume on the first boot, boots it once more to see that it no longer does.
 func bootCheck(gamesDir, id, agentImage string, wantOutside bool) (problems, verified []string, err error) {
-	if out, err := runCmd("docker", "pull", "-q", agentImage); err != nil {
+	if err := pullAgentImage(agentImage); err != nil {
-		return nil, nil, fmt.Errorf("docker pull %s: %v: %s", agentImage, err, out)
+		return nil, nil, err
 	}
 	output, passed, problems, err := agentBoot(gamesDir, id, agentImage, false)
 	if err != nil || problems != nil {

cmd/gbrgames/firstboot.go

@@ -146,8 +146,8 @@ func runFirstBoot(args []string) error {
 			return err
 		}
 	}
-	if out, err := runCmd("docker", "pull", "-q", b.agentImage); err != nil {
+	if err := pullAgentImage(b.agentImage); err != nil {
-		return fmt.Errorf("docker pull %s: %v: %s", b.agentImage, err, out)
+		return err
 	}
 	if !*keep {
 		defer b.cleanup()