diff --git a/cmd/mcp/build.go b/cmd/mcp/build.go
index 4060c24..e8b47aa 100644
--- a/cmd/mcp/build.go
+++ b/cmd/mcp/build.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"git.wntrmute.dev/mc/mcp/internal/auth"
 	"git.wntrmute.dev/mc/mcp/internal/config"
 	"git.wntrmute.dev/mc/mcp/internal/runtime"
 	"git.wntrmute.dev/mc/mcp/internal/servicedef"
@@ -52,6 +53,17 @@ func buildServiceImages(ctx context.Context, cfg *config.CLIConfig, def *service
 
 	sourceDir := filepath.Join(cfg.Build.Workspace, def.Path)
 
+	// Auto-login to the registry using the CLI's stored MCIAS token.
+	// MCR accepts JWTs as passwords, so this works for both human and
+	// service account tokens. Failures are non-fatal — existing podman
+	// auth may suffice.
+	if token, err := auth.LoadToken(cfg.Auth.TokenPath); err == nil && token != "" {
+		registry := extractRegistry(def)
+		if registry != "" {
+			_ = rt.Login(ctx, registry, "mcp", token)
+		}
+	}
+
 	for imageName, dockerfile := range def.Build.Images {
 		if imageFilter != "" && imageName != imageFilter {
 			continue
@@ -96,6 +108,19 @@ func findImageRef(def *servicedef.ServiceDef, imageName string) string {
 	return ""
 }
 
+// extractRegistry returns the registry host from the first component's
+// image reference (e.g., "mcr.svc.mcp.metacircular.net:8443" from
+// "mcr.svc.mcp.metacircular.net:8443/mcq:v0.1.1"). Returns empty
+// string if no slash is found.
+func extractRegistry(def *servicedef.ServiceDef) string {
+	for _, c := range def.Components {
+		if i := strings.LastIndex(c.Image, "/"); i > 0 {
+			return c.Image[:i]
+		}
+	}
+	return ""
+}
+
 // extractRepoName returns the repository name from an image reference.
 // Examples:
 //
@@ -124,6 +149,8 @@ func ensureImages(ctx context.Context, cfg *config.CLIConfig, def *servicedef.Se
 		return nil // no build config, skip auto-build
 	}
 
+	registryLoginDone := false
+
 	for _, c := range def.Components {
 		if component != "" && c.Name != component {
 			continue
@@ -153,6 +180,17 @@ func ensureImages(ctx context.Context, cfg *config.CLIConfig, def *servicedef.Se
 
 		sourceDir := filepath.Join(cfg.Build.Workspace, def.Path)
 
+		// Auto-login to registry before first push.
+		if !registryLoginDone {
+			if token, err := auth.LoadToken(cfg.Auth.TokenPath); err == nil && token != "" {
+				registry := extractRegistry(def)
+				if registry != "" {
+					_ = rt.Login(ctx, registry, "mcp", token)
+				}
+			}
+			registryLoginDone = true
+		}
+
 		fmt.Printf("image %s not found, building from %s\n", c.Image, dockerfile)
 		if err := rt.Build(ctx, c.Image, sourceDir, dockerfile); err != nil {
 			return fmt.Errorf("auto-build %s: %w", c.Image, err)
diff --git a/internal/runtime/podman.go b/internal/runtime/podman.go
index 846a5b4..9f41cec 100644
--- a/internal/runtime/podman.go
+++ b/internal/runtime/podman.go
@@ -178,6 +178,18 @@ func (p *Podman) Inspect(ctx context.Context, name string) (ContainerInfo, error
 	return info, nil
 }
 
+// Login authenticates to a container registry using the given token as
+// the password. This enables non-interactive push with service account
+// tokens (MCR accepts MCIAS JWTs as passwords).
+func (p *Podman) Login(ctx context.Context, registry, username, token string) error {
+	cmd := exec.CommandContext(ctx, p.command(), "login", "--username", username, "--password-stdin", registry) //nolint:gosec // args built programmatically
+	cmd.Stdin = strings.NewReader(token)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("podman login %q: %w: %s", registry, err, out)
+	}
+	return nil
+}
+
 // Build builds a container image from a Dockerfile.
 func (p *Podman) Build(ctx context.Context, image, contextDir, dockerfile string) error {
 	args := []string{"build", "-t", image, "-f", dockerfile, contextDir}