metis(ui): split build and flash workflows

2026-04-24 12:09:53 -03:00 · 2026-04-24 12:09:53 -03:00 · 56d31fa613
commit 56d31fa613
parent bf9c514fd0
17 changed files with 1021 additions and 144 deletions
--- a/cmd/metis/remote_cmd.go
+++ b/cmd/metis/remote_cmd.go
@ -163,76 +163,6 @@ func remoteBuildCmd(args []string) {
 	writeStructuredResult(summary)
 }

-func remoteFlashCmd(args []string) {
-	fs := flag.NewFlagSet("remote-flash", flag.ExitOnError)
-	node := fs.String("node", "", "target node")
-	device := fs.String("device", "", "target device path or test sink")
-	artifactRef := fs.String("artifact-ref", "", "harbor artifact ref without tag")
-	workDir := fs.String("work-dir", filepath.Join(os.TempDir(), "metis-flash"), "working directory")
-	harborRegistry := fs.String("harbor-registry", getenvOr("METIS_HARBOR_REGISTRY", "registry.bstein.dev"), "harbor registry host")
-	harborUsername := fs.String("harbor-username", getenvOr("METIS_HARBOR_USERNAME", ""), "harbor username")
-	harborPassword := fs.String("harbor-password", getenvOr("METIS_HARBOR_PASSWORD", ""), "harbor password")
-	hostTmpDir := fs.String("host-tmp-dir", "/host-tmp", "mounted host tmp dir for test writes")
-	fs.Parse(args)
-	if *node == "" || *device == "" || *artifactRef == "" {
-		fatalf("--node, --device, and --artifact-ref are required")
-	}
-
-	if err := os.MkdirAll(*workDir, 0o755); err != nil {
-		fatalf("mkdir workdir: %v", err)
-	}
-	emitStageProgress("flash", 84, fmt.Sprintf("Pulling the latest Harbor artifact for %s", *node))
-	if err := orasLogin(*harborRegistry, *harborUsername, *harborPassword); err != nil {
-		fatalf("oras login: %v", err)
-	}
-	if err := orasPull(fmt.Sprintf("%s:latest", *artifactRef), *workDir); err != nil {
-		fatalf("oras pull: %v", err)
-	}
-	emitStageProgress("flash", 88, fmt.Sprintf("Preparing the downloaded image for %s", *node))
-	imagePath, compressed, err := resolvePulledArtifact(*workDir)
-	if err != nil {
-		fatalf("resolve artifact: %v", err)
-	}
-	rawImage := imagePath
-	if compressed {
-		emitStageProgress("flash", 90, fmt.Sprintf("Decompressing the image for %s before writing", *node))
-		rawImage = filepath.Join(*workDir, fmt.Sprintf("%s.img", *node))
-		cmd := exec.Command("sh", "-lc", fmt.Sprintf("xz -dc '%s' > '%s'", imagePath, rawImage))
-		if out, err := cmd.CombinedOutput(); err != nil {
-			fatalf("xz stream decompress: %v: %s", err, strings.TrimSpace(string(out)))
-		}
-	}
-
-	destPath := *device
-	if strings.HasPrefix(destPath, "hosttmp://") {
-		if err := os.MkdirAll(*hostTmpDir, 0o755); err != nil {
-			fatalf("mkdir host tmp dir: %v", err)
-		}
-		destPath = filepath.Join(*hostTmpDir, fmt.Sprintf("%s.img", *node))
-	}
-	emitStageProgress("flash", 92, fmt.Sprintf("Writing the latest image for %s to %s", *node, destPath))
-	writeEmitter := newProgressEmitter("flash", 92, 98, fmt.Sprintf("Writing the latest image for %s", *node), true)
-	if err := writer.WriteImageWithProgress(context.Background(), rawImage, destPath, writeEmitter); err != nil {
-		fatalf("write image: %v", err)
-	}
-	emitStageProgress("flash", 99, fmt.Sprintf("Flushing the finished image for %s", *node))
-	_ = exec.Command("sync").Run()
-	if strings.HasPrefix(destPath, "/dev/") {
-		_ = exec.Command("blockdev", "--flushbufs", destPath).Run()
-	}
-
-	info, err := os.Stat(destPath)
-	if err != nil {
-		fatalf("stat destination: %v", err)
-	}
-	writeStructuredResult(map[string]any{
-		"node":       *node,
-		"device":     *device,
-		"dest_path":  destPath,
-		"size_bytes": info.Size(),
-	})
-}
-
 func writeStructuredResult(payload any) {
 	data, err := json.Marshal(payload)
 	if err != nil {
--- a/cmd/metis/remote_flash.go
+++ b/cmd/metis/remote_flash.go
@ -0,0 +1,304 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"metis/pkg/service"
+	"metis/pkg/writer"
+)
+
+type flashPartitionTable struct {
+	PartitionTable struct {
+		Partitions []flashTablePartition `json:"partitions"`
+	} `json:"partitiontable"`
+}
+
+type flashTablePartition struct {
+	Type string `json:"type"`
+}
+
+type flashBlockDevicePayload struct {
+	Blockdevices []flashBlockDevice `json:"blockdevices"`
+}
+
+type flashBlockDevice struct {
+	Path     string             `json:"path"`
+	Type     string             `json:"type"`
+	FSType   string             `json:"fstype"`
+	Label    string             `json:"label"`
+	Children []flashBlockDevice `json:"children"`
+}
+
+var requiredBootFiles = []string{"config.txt", "cmdline.txt", "boot.scr"}
+
+func remoteFlashCmd(args []string) {
+	fs := flag.NewFlagSet("remote-flash", flag.ExitOnError)
+	node := fs.String("node", "", "target node")
+	device := fs.String("device", "", "target device path or test sink")
+	artifactRef := fs.String("artifact-ref", "", "harbor artifact ref without tag")
+	workDir := fs.String("work-dir", filepath.Join(os.TempDir(), "metis-flash"), "working directory")
+	harborRegistry := fs.String("harbor-registry", getenvOr("METIS_HARBOR_REGISTRY", "registry.bstein.dev"), "harbor registry host")
+	harborUsername := fs.String("harbor-username", getenvOr("METIS_HARBOR_USERNAME", ""), "harbor username")
+	harborPassword := fs.String("harbor-password", getenvOr("METIS_HARBOR_PASSWORD", ""), "harbor password")
+	hostTmpDir := fs.String("host-tmp-dir", "/host-tmp", "mounted host tmp dir for test writes")
+	fs.Parse(args)
+	if *node == "" || *device == "" || *artifactRef == "" {
+		fatalf("--node, --device, and --artifact-ref are required")
+	}
+
+	if err := os.MkdirAll(*workDir, 0o755); err != nil {
+		fatalf("mkdir workdir: %v", err)
+	}
+	emitStageProgress("flash_pull", 84, fmt.Sprintf("Pulling the latest Harbor artifact for %s", *node))
+	if err := orasLogin(*harborRegistry, *harborUsername, *harborPassword); err != nil {
+		fatalf("oras login: %v", err)
+	}
+	if err := orasPull(fmt.Sprintf("%s:latest", *artifactRef), *workDir); err != nil {
+		fatalf("oras pull: %v", err)
+	}
+	emitStageProgress("flash_prepare", 88, fmt.Sprintf("Preparing the downloaded image for %s", *node))
+	imagePath, compressed, err := resolvePulledArtifact(*workDir)
+	if err != nil {
+		fatalf("resolve artifact: %v", err)
+	}
+	rawImage := imagePath
+	if compressed {
+		emitStageProgress("flash_unpack", 90, fmt.Sprintf("Decompressing the image for %s before writing", *node))
+		rawImage = filepath.Join(*workDir, fmt.Sprintf("%s.img", *node))
+		cmd := exec.Command("sh", "-lc", fmt.Sprintf("xz -dc '%s' > '%s'", imagePath, rawImage))
+		if out, err := cmd.CombinedOutput(); err != nil {
+			fatalf("xz stream decompress: %v: %s", err, strings.TrimSpace(string(out)))
+		}
+	}
+
+	destPath := *device
+	if strings.HasPrefix(destPath, "hosttmp://") {
+		if err := os.MkdirAll(*hostTmpDir, 0o755); err != nil {
+			fatalf("mkdir host tmp dir: %v", err)
+		}
+		destPath = filepath.Join(*hostTmpDir, fmt.Sprintf("%s.img", *node))
+	}
+	info, err := os.Stat(rawImage)
+	if err != nil {
+		fatalf("stat raw image: %v", err)
+	}
+	imageSize := info.Size()
+	emitStageProgress("flash_write", 92, fmt.Sprintf("Writing the latest image for %s to %s", *node, destPath))
+	writeEmitter := newProgressEmitter("flash_write", 92, 98, fmt.Sprintf("Writing the latest image for %s", *node), true)
+	if err := writer.WriteImageWithProgress(context.Background(), rawImage, destPath, writeEmitter); err != nil {
+		fatalf("write image: %v", err)
+	}
+	flushFlashTarget(destPath, *node)
+	result, err := verifyFlashDestination(destPath)
+	if err != nil {
+		fatalf("verify flash output: %v", err)
+	}
+	result.Node = *node
+	result.Device = *device
+	result.DestPath = destPath
+	result.SizeBytes = imageSize
+	writeStructuredResult(result)
+}
+
+func flushFlashTarget(destPath, node string) {
+	emitStageProgress("flash_flush", 98.5, fmt.Sprintf("Flushing the finished image for %s", node))
+	_ = exec.Command("sync").Run()
+	if !strings.HasPrefix(destPath, "/dev/") {
+		return
+	}
+	_ = exec.Command("blockdev", "--flushbufs", destPath).Run()
+	_ = exec.Command("blockdev", "--rereadpt", destPath).Run()
+	_ = exec.Command("partprobe", destPath).Run()
+	_ = exec.Command("udevadm", "settle", "--timeout=10").Run()
+}
+
+func verifyFlashDestination(destPath string) (service.RemoteFlashResult, error) {
+	emitStageProgress("flash_verify", 99.2, fmt.Sprintf("Verifying the flashed recovery media at %s", destPath))
+	if strings.HasPrefix(destPath, "/dev/") {
+		return verifyBlockDeviceFlash(destPath)
+	}
+	return verifyImageFileFlash(destPath)
+}
+
+func verifyImageFileFlash(destPath string) (service.RemoteFlashResult, error) {
+	table, err := readFlashPartitionTable(destPath)
+	if err != nil {
+		return service.RemoteFlashResult{}, err
+	}
+	hasBoot := false
+	hasRoot := false
+	for _, part := range table.PartitionTable.Partitions {
+		if isBootPartitionType(part.Type) {
+			hasBoot = true
+		}
+		if isLinuxPartitionType(part.Type) {
+			hasRoot = true
+		}
+	}
+	if !hasBoot || !hasRoot {
+		return service.RemoteFlashResult{}, fmt.Errorf("image %s does not expose the expected boot and writable partitions", destPath)
+	}
+	return service.RemoteFlashResult{
+		Verified:            true,
+		VerificationKind:    "image-file",
+		VerificationSummary: fmt.Sprintf("Verified image layout at %s; boot and writable partitions are present.", destPath),
+	}, nil
+}
+
+func verifyBlockDeviceFlash(destPath string) (service.RemoteFlashResult, error) {
+	deadline := time.Now().Add(15 * time.Second)
+	var lastErr error
+	for time.Now().Before(deadline) {
+		parts, err := readBlockDevicePartitions(destPath)
+		if err == nil {
+			boot, root, classifyErr := classifyFlashPartitions(parts)
+			if classifyErr == nil {
+				checkedFiles, verifyErr := verifyBootPartitionFiles(boot.Path)
+				if verifyErr == nil {
+					bootLabel := firstNonEmpty(boot.Label, filepath.Base(boot.Path))
+					rootLabel := firstNonEmpty(root.Label, filepath.Base(root.Path))
+					return service.RemoteFlashResult{
+						Verified:            true,
+						VerificationKind:    "block-device",
+						VerificationSummary: fmt.Sprintf("Verified %s; %s and %s are present and the boot files look correct.", destPath, bootLabel, rootLabel),
+						BootPartition:       boot.Path,
+						RootPartition:       root.Path,
+						BootLabel:           boot.Label,
+						RootLabel:           root.Label,
+						BootFSType:          boot.FSType,
+						RootFSType:          root.FSType,
+						CheckedFiles:        checkedFiles,
+					}, nil
+				}
+				lastErr = verifyErr
+			} else {
+				lastErr = classifyErr
+			}
+		} else {
+			lastErr = err
+		}
+		_ = exec.Command("blockdev", "--rereadpt", destPath).Run()
+		_ = exec.Command("partprobe", destPath).Run()
+		_ = exec.Command("udevadm", "settle", "--timeout=10").Run()
+		time.Sleep(time.Second)
+	}
+	if lastErr == nil {
+		lastErr = fmt.Errorf("timed out waiting for the flashed partitions on %s", destPath)
+	}
+	return service.RemoteFlashResult{}, lastErr
+}
+
+func readFlashPartitionTable(destPath string) (flashPartitionTable, error) {
+	out, err := exec.Command("sfdisk", "-J", destPath).CombinedOutput()
+	if err != nil {
+		return flashPartitionTable{}, fmt.Errorf("sfdisk -J %s: %v: %s", destPath, err, strings.TrimSpace(string(out)))
+	}
+	var table flashPartitionTable
+	if err := json.Unmarshal(out, &table); err != nil {
+		return flashPartitionTable{}, fmt.Errorf("decode partition table for %s: %w", destPath, err)
+	}
+	return table, nil
+}
+
+func readBlockDevicePartitions(destPath string) ([]flashBlockDevice, error) {
+	out, err := exec.Command("lsblk", "-J", "-o", "PATH,TYPE,FSTYPE,LABEL", destPath).CombinedOutput()
+	if err != nil {
+		return nil, fmt.Errorf("lsblk %s: %v: %s", destPath, err, strings.TrimSpace(string(out)))
+	}
+	var payload flashBlockDevicePayload
+	if err := json.Unmarshal(out, &payload); err != nil {
+		return nil, fmt.Errorf("decode lsblk output for %s: %w", destPath, err)
+	}
+	for _, device := range payload.Blockdevices {
+		if device.Path == destPath {
+			return device.Children, nil
+		}
+	}
+	if len(payload.Blockdevices) == 1 {
+		return payload.Blockdevices[0].Children, nil
+	}
+	return nil, fmt.Errorf("lsblk did not report partitions for %s", destPath)
+}
+
+func classifyFlashPartitions(parts []flashBlockDevice) (flashBlockDevice, flashBlockDevice, error) {
+	var boot flashBlockDevice
+	var root flashBlockDevice
+	for _, part := range parts {
+		if part.Type != "part" {
+			continue
+		}
+		normalizedLabel := strings.ToLower(strings.TrimSpace(part.Label))
+		normalizedFS := strings.ToLower(strings.TrimSpace(part.FSType))
+		if boot.Path == "" && (normalizedLabel == "system-boot" || normalizedFS == "vfat" || normalizedFS == "fat" || normalizedFS == "fat32") {
+			boot = part
+			continue
+		}
+		if root.Path == "" && (normalizedLabel == "writable" || normalizedFS == "ext4") {
+			root = part
+		}
+	}
+	if boot.Path == "" {
+		return flashBlockDevice{}, flashBlockDevice{}, fmt.Errorf("could not find a boot partition with a FAT filesystem")
+	}
+	if root.Path == "" {
+		return flashBlockDevice{}, flashBlockDevice{}, fmt.Errorf("could not find a writable ext4 partition")
+	}
+	return boot, root, nil
+}
+
+func verifyBootPartitionFiles(partitionPath string) ([]string, error) {
+	mountDir, err := os.MkdirTemp("", "metis-boot-")
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(mountDir)
+	cmd := exec.Command("mount", "-o", "ro", partitionPath, mountDir)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return nil, fmt.Errorf("mount %s read-only: %v: %s", partitionPath, err, strings.TrimSpace(string(out)))
+	}
+	defer exec.Command("umount", mountDir).Run()
+
+	checked := make([]string, 0, len(requiredBootFiles))
+	for _, name := range requiredBootFiles {
+		if _, err := os.Stat(filepath.Join(mountDir, name)); err != nil {
+			return nil, fmt.Errorf("boot partition %s is missing %s", partitionPath, name)
+		}
+		checked = append(checked, name)
+	}
+	return checked, nil
+}
+
+func isBootPartitionType(partType string) bool {
+	normalized := strings.ToLower(strings.TrimSpace(partType))
+	switch normalized {
+	case "b", "c", "0b", "0c", "ef", "ef00":
+		return true
+	}
+	return normalized == "c12a7328-f81f-11d2-ba4b-00a0c93ec93b"
+}
+
+func isLinuxPartitionType(partType string) bool {
+	normalized := strings.ToLower(strings.TrimSpace(partType))
+	switch normalized {
+	case "83", "8300":
+		return true
+	}
+	return normalized == "0fc63daf-8483-4772-8e79-3d69d8477de4"
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, value := range values {
+		if trimmed := strings.TrimSpace(value); trimmed != "" {
+			return trimmed
+		}
+	}
+	return ""
+}
--- a/cmd/metis/remote_flash_test.go
+++ b/cmd/metis/remote_flash_test.go
@ -0,0 +1,246 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestVerifyFlashDestinationForImageFilesAndBlockDevices(t *testing.T) {
+	t.Run("image file success and helpers", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"sfdisk": `cat <<'JSON'
+{"partitiontable":{"partitions":[{"type":"ef00"},{"type":"8300"}]}}
+JSON`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+		result, err := verifyFlashDestination(filepath.Join(t.TempDir(), "titan-15.img"))
+		if err != nil {
+			t.Fatalf("verifyFlashDestination(image): %v", err)
+		}
+		if !result.Verified || result.VerificationKind != "image-file" {
+			t.Fatalf("unexpected image verification result: %#v", result)
+		}
+		if !isBootPartitionType("ef00") || !isLinuxPartitionType("8300") {
+			t.Fatal("expected helper partition type recognizers to accept GPT aliases")
+		}
+		if got := firstNonEmpty("", " writable ", "ignored"); got != "writable" {
+			t.Fatalf("firstNonEmpty = %q", got)
+		}
+	})
+
+	t.Run("image file missing writable partition", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"sfdisk": `cat <<'JSON'
+{"partitiontable":{"partitions":[{"type":"ef00"}]}}
+JSON`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+		if _, err := verifyImageFileFlash(filepath.Join(t.TempDir(), "broken.img")); err == nil || !strings.Contains(err.Error(), "boot and writable partitions") {
+			t.Fatalf("expected missing partition error, got %v", err)
+		}
+	})
+
+	t.Run("image file missing boot partition", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"sfdisk": `cat <<'JSON'
+{"partitiontable":{"partitions":[{"type":"8300"}]}}
+JSON`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+		if _, err := verifyImageFileFlash(filepath.Join(t.TempDir(), "broken-boot.img")); err == nil || !strings.Contains(err.Error(), "boot and writable partitions") {
+			t.Fatalf("expected missing boot partition error, got %v", err)
+		}
+	})
+
+	t.Run("block device success", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"lsblk": `cat <<'JSON'
+{"blockdevices":[{"path":"/dev/sdk","children":[{"path":"/dev/sdk1","type":"part","fstype":"vfat","label":"system-boot"},{"path":"/dev/sdk2","type":"part","fstype":"ext4","label":"writable"}]}]}
+JSON`,
+			"mount": `mount_dir="${4:-}"
+mkdir -p "${mount_dir}"
+printf 'ok' > "${mount_dir}/config.txt"
+printf 'console=ttyAMA0' > "${mount_dir}/cmdline.txt"
+printf 'boot script' > "${mount_dir}/boot.scr"`,
+			"umount":    `exit 0`,
+			"blockdev":  `exit 0`,
+			"partprobe": `exit 0`,
+			"udevadm":   `exit 0`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+		result, err := verifyFlashDestination("/dev/sdk")
+		if err != nil {
+			t.Fatalf("verifyFlashDestination(block): %v", err)
+		}
+		if !result.Verified || result.VerificationKind != "block-device" {
+			t.Fatalf("unexpected block-device verification result: %#v", result)
+		}
+		if result.BootPartition != "/dev/sdk1" || result.RootPartition != "/dev/sdk2" {
+			t.Fatalf("unexpected partition details: %#v", result)
+		}
+		if len(result.CheckedFiles) != 3 {
+			t.Fatalf("expected checked boot files, got %#v", result.CheckedFiles)
+		}
+	})
+
+	t.Run("block device missing boot file", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"lsblk": `cat <<'JSON'
+{"blockdevices":[{"path":"/dev/sdk","children":[{"path":"/dev/sdk1","type":"part","fstype":"vfat","label":"system-boot"},{"path":"/dev/sdk2","type":"part","fstype":"ext4","label":"writable"}]}]}
+JSON`,
+			"mount": `mount_dir="${4:-}"
+mkdir -p "${mount_dir}"
+printf 'ok' > "${mount_dir}/config.txt"
+printf 'console=ttyAMA0' > "${mount_dir}/cmdline.txt"`,
+			"umount":    `exit 0`,
+			"blockdev":  `exit 0`,
+			"partprobe": `exit 0`,
+			"udevadm":   `exit 0`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+		if _, err := verifyBlockDeviceFlash("/dev/sdk"); err == nil || !strings.Contains(err.Error(), "missing boot.scr") {
+			t.Fatalf("expected missing boot file error, got %v", err)
+		}
+	})
+}
+
+func TestFlushFlashTargetAndClassifyHelpers(t *testing.T) {
+	logPath := filepath.Join(t.TempDir(), "commands.log")
+	tools := fakeCommandDir(t, map[string]string{
+		"sync":      `printf 'sync %s\n' "$*" >> "` + logPath + `"`,
+		"blockdev":  `printf 'blockdev %s\n' "$*" >> "` + logPath + `"`,
+		"partprobe": `printf 'partprobe %s\n' "$*" >> "` + logPath + `"`,
+		"udevadm":   `printf 'udevadm %s\n' "$*" >> "` + logPath + `"`,
+	})
+	t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+	flushFlashTarget("/tmp/test.img", "titan-15")
+	flushFlashTarget("/dev/sdk", "titan-15")
+
+	logged, err := os.ReadFile(logPath)
+	if err != nil {
+		t.Fatalf("read flush log: %v", err)
+	}
+	text := string(logged)
+	if strings.Count(text, "sync ") != 2 {
+		t.Fatalf("expected sync for file and block targets, got %q", text)
+	}
+	for _, want := range []string{"blockdev --flushbufs /dev/sdk", "blockdev --rereadpt /dev/sdk", "partprobe /dev/sdk", "udevadm settle --timeout=10"} {
+		if !strings.Contains(text, want) {
+			t.Fatalf("expected %q in %q", want, text)
+		}
+	}
+
+	if _, _, err := classifyFlashPartitions([]flashBlockDevice{{Path: "/dev/sdk1", Type: "part", FSType: "vfat", Label: "system-boot"}}); err == nil || !strings.Contains(err.Error(), "writable ext4") {
+		t.Fatalf("expected classify failure, got %v", err)
+	}
+}
+
+func TestReadFlashPartitionTableAndBlockPartitionErrors(t *testing.T) {
+	t.Run("partition table decode error", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{"sfdisk": `printf '{'`})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		if _, err := readFlashPartitionTable(filepath.Join(t.TempDir(), "broken.img")); err == nil || !strings.Contains(err.Error(), "decode partition table") {
+			t.Fatalf("expected partition table decode error, got %v", err)
+		}
+	})
+
+	t.Run("lsblk decode error", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{"lsblk": `printf '{'`})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		if _, err := readBlockDevicePartitions("/dev/sdk"); err == nil || !strings.Contains(err.Error(), "decode lsblk output") {
+			t.Fatalf("expected lsblk decode error, got %v", err)
+		}
+	})
+
+	t.Run("lsblk finds explicit device match", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"lsblk": `cat <<'JSON'
+{"blockdevices":[{"path":"/dev/other","children":[{"path":"/dev/other1","type":"part"}]},{"path":"/dev/sdk","children":[{"path":"/dev/sdk1","type":"part","fstype":"vfat","label":"system-boot"}]}]}
+JSON`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		parts, err := readBlockDevicePartitions("/dev/sdk")
+		if err != nil {
+			t.Fatalf("readBlockDevicePartitions match: %v", err)
+		}
+		if len(parts) != 1 || parts[0].Path != "/dev/sdk1" {
+			t.Fatalf("unexpected matching partitions: %#v", parts)
+		}
+	})
+
+	t.Run("lsblk missing device match", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{
+			"lsblk": `cat <<'JSON'
+{"blockdevices":[{"path":"/dev/other","children":[]},{"path":"/dev/another","children":[]}]}
+JSON`,
+		})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		if _, err := readBlockDevicePartitions("/dev/sdk"); err == nil || !strings.Contains(err.Error(), "did not report partitions") {
+			t.Fatalf("expected missing block-device match error, got %v", err)
+		}
+	})
+}
+
+func TestVerifyBootPartitionFilesMountFailure(t *testing.T) {
+	tools := fakeCommandDir(t, map[string]string{
+		"mount": `printf 'mount failed' >&2; exit 9`,
+	})
+	t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+	if _, err := verifyBootPartitionFiles("/dev/sdk1"); err == nil || !strings.Contains(err.Error(), "mount /dev/sdk1 read-only") {
+		t.Fatalf("expected mount failure, got %v", err)
+	}
+}
+
+func TestRemoteFlashHelperAdditionalFailureBranches(t *testing.T) {
+	t.Run("partition table command failure", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{"sfdisk": `printf 'bad disk' >&2; exit 7`})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		if _, err := readFlashPartitionTable(filepath.Join(t.TempDir(), "broken.img")); err == nil || !strings.Contains(err.Error(), "sfdisk -J") {
+			t.Fatalf("expected sfdisk failure, got %v", err)
+		}
+	})
+
+	t.Run("lsblk command failure", func(t *testing.T) {
+		tools := fakeCommandDir(t, map[string]string{"lsblk": `printf 'lsblk failed' >&2; exit 4`})
+		t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+		if _, err := readBlockDevicePartitions("/dev/sdk"); err == nil || !strings.Contains(err.Error(), "lsblk /dev/sdk") {
+			t.Fatalf("expected lsblk command failure, got %v", err)
+		}
+	})
+
+	t.Run("boot partition classification failure", func(t *testing.T) {
+		if _, _, err := classifyFlashPartitions([]flashBlockDevice{{Path: "/dev/sdk2", Type: "part", FSType: "ext4", Label: "writable"}}); err == nil || !strings.Contains(err.Error(), "boot partition") {
+			t.Fatalf("expected missing boot partition error, got %v", err)
+		}
+	})
+
+	t.Run("firstNonEmpty returns empty when every value is blank", func(t *testing.T) {
+		if got := firstNonEmpty("", "   "); got != "" {
+			t.Fatalf("expected empty firstNonEmpty result, got %q", got)
+		}
+	})
+}
+
+func TestReadBlockDevicePartitionsFallsBackToSingleReturnedDevice(t *testing.T) {
+	tools := fakeCommandDir(t, map[string]string{
+		"lsblk": `cat <<'JSON'
+{"blockdevices":[{"path":"/dev/mmcblk0","children":[{"path":"/dev/mmcblk0p1","type":"part","fstype":"vfat","label":"system-boot"}]}]}
+JSON`,
+	})
+	t.Setenv("PATH", tools+string(os.PathListSeparator)+os.Getenv("PATH"))
+	parts, err := readBlockDevicePartitions("/dev/sdk")
+	if err != nil {
+		t.Fatalf("readBlockDevicePartitions fallback: %v", err)
+	}
+	if len(parts) != 1 || parts[0].Path != "/dev/mmcblk0p1" {
+		t.Fatalf("unexpected fallback partitions: %#v", parts)
+	}
+}
--- a/pkg/service/app.go
+++ b/pkg/service/app.go
@ -221,6 +221,31 @@ func (a *App) Build(node string) (*Job, error) {
 	return job, nil
 }

+// Flash starts a background flash-only workflow for the latest published node image.
+func (a *App) Flash(node, host, device string) (*Job, error) {
+	if host == "" {
+		host = a.settings.DefaultFlashHost
+	}
+	if err := a.ensureReplacementReady(node); err != nil {
+		return nil, err
+	}
+	if active := a.activeJobForNode(node); active != nil {
+		return nil, &activeNodeJobError{Node: node, Kind: active.Kind, JobID: active.ID}
+	}
+	if summary, ok := a.artifacts()[node]; !ok || strings.TrimSpace(summary.Ref) == "" {
+		return nil, fmt.Errorf("no published image recorded for %s yet; run a build first", node)
+	}
+	if _, err := a.ensureDevice(host, device); err != nil {
+		return nil, err
+	}
+	job, err := a.reserveJob("flash", node, host, device)
+	if err != nil {
+		return nil, err
+	}
+	go a.runFlash(job)
+	return job, nil
+}
+
 // Replace starts a background build+flash workflow for a node.
 func (a *App) Replace(node, host, device string) (*Job, error) {
 	if host == "" {
--- a/pkg/service/app_helpers.go
+++ b/pkg/service/app_helpers.go
@ -68,7 +68,7 @@ func (a *App) activeJobForNodeLocked(node string) *Job {
 			continue
 		}
 		switch job.Kind {
-		case "build", "replace":
+		case "build", "flash", "replace":
 		default:
 			continue
 		}
--- a/pkg/service/coverage_more_test.go
+++ b/pkg/service/coverage_more_test.go
@ -407,7 +407,7 @@ func TestServiceClusterAndRemotePodBranches(t *testing.T) {
 				"metadata": map[string]any{"name": filepath.Base(r.URL.Path)},
 				"status": map[string]any{
 					"phase":   "Succeeded",
-					"message": `{"dest_path":"/tmp/out.img"}`,
+					"message": `{"dest_path":"/tmp/out.img","verified":true,"verification_kind":"image-file","verification_summary":"Verified image layout at /tmp/out.img; boot and writable partitions are present."}`,
 					"reason":  "Completed",
 				},
 			})
--- a/pkg/service/flash_workflow_test.go
+++ b/pkg/service/flash_workflow_test.go
@ -0,0 +1,182 @@
+package service
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestFlashOnlyWorkflowRequiresPublishedArtifact(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+
+	if _, err := app.Flash("titan-15", "titan-22", "/dev/sdz"); err == nil || !strings.Contains(err.Error(), "run a build first") {
+		t.Fatalf("expected missing artifact error, got %v", err)
+	}
+}
+
+func TestFlashOnlyWorkflowCompletesAndRecordsVerification(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{flashMessage: `{"dest_path":"/dev/sdz","verified":true,"verification_kind":"block-device","verification_summary":"Verified /dev/sdz; system-boot and writable are present and the boot files look correct.","boot_partition":"/dev/sdz1","root_partition":"/dev/sdz2","boot_label":"system-boot","root_label":"writable","boot_fstype":"vfat","root_fstype":"ext4","checked_files":["config.txt","cmdline.txt","boot.scr"]}`})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+
+	job, err := app.Flash("titan-15", "titan-22", "/dev/sdz")
+	if err != nil {
+		t.Fatalf("Flash: %v", err)
+	}
+	waitForJobState(t, app, job.ID, JobDone)
+
+	got := app.job(job.ID)
+	if got == nil || got.Kind != "flash" || got.Status != JobDone {
+		t.Fatalf("unexpected flash job: %#v", got)
+	}
+	if !strings.Contains(got.Message, "Move the card into titan-15") {
+		t.Fatalf("unexpected completion message: %#v", got)
+	}
+	if got.ProgressPct != 100 {
+		t.Fatalf("expected complete flash progress, got %#v", got)
+	}
+
+	events := app.recentEvents(5)
+	if len(events) == 0 || events[0].Kind != "image.flash" {
+		t.Fatalf("expected flash event, got %#v", events)
+	}
+	if verified, ok := events[0].Details["verified"].(bool); !ok || !verified {
+		t.Fatalf("expected verified flash details, got %#v", events[0].Details)
+	}
+	if kind, ok := events[0].Details["verification_kind"].(string); !ok || kind != "block-device" {
+		t.Fatalf("expected block-device verification, got %#v", events[0].Details)
+	}
+	if bootPartition, ok := events[0].Details["boot_partition"].(string); !ok || bootPartition != "/dev/sdz1" {
+		t.Fatalf("expected boot partition details, got %#v", events[0].Details)
+	}
+}
+
+func TestHandleFlashRouteStartsFlashOnlyJob(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+	handler := app.Handler()
+
+	req := httptest.NewRequest(http.MethodPost, "/api/jobs/flash", strings.NewReader(`{"node":"titan-15","host":"titan-22","device":"/dev/sdz"}`))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-Auth-Request-User", "brad")
+	req.Header.Set("X-Auth-Request-Groups", "admin")
+	resp := httptest.NewRecorder()
+	handler.ServeHTTP(resp, req)
+	if resp.Code != http.StatusAccepted {
+		t.Fatalf("flash route response: %d %s", resp.Code, resp.Body.String())
+	}
+
+	var job Job
+	if err := json.Unmarshal(resp.Body.Bytes(), &job); err != nil {
+		t.Fatalf("decode flash job: %v", err)
+	}
+	waitForJobState(t, app, job.ID, JobDone)
+	if got := app.job(job.ID); got == nil || got.Kind != "flash" {
+		t.Fatalf("expected flash job, got %#v", got)
+	}
+}
+
+func TestFlashAndReplaceDefaultHostBranches(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{})
+	harbor := fakeHarborServer(t, true)
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, harbor)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+
+	flashJob, err := app.Flash("titan-15", "", hostTmpDevicePath)
+	if err != nil {
+		t.Fatalf("Flash default host: %v", err)
+	}
+	waitForJobState(t, app, flashJob.ID, JobDone)
+	if got := app.job(flashJob.ID); got == nil || got.Host != "titan-22" || !strings.Contains(got.Message, "host /tmp") {
+		t.Fatalf("unexpected flash default host job: %#v", got)
+	}
+
+	replaceJob, err := app.Replace("titan-15", "", hostTmpDevicePath)
+	if err != nil {
+		t.Fatalf("Replace default host: %v", err)
+	}
+	waitForJobState(t, app, replaceJob.ID, JobDone)
+	if got := app.job(replaceJob.ID); got == nil || got.Host != "titan-22" {
+		t.Fatalf("unexpected replace default host job: %#v", got)
+	}
+}
+
+func TestFlashRejectsDuplicateActiveNodeJob(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+	app.newJob("flash", "titan-15", "titan-22", "/dev/sdz")
+
+	if _, err := app.Flash("titan-15", "titan-22", "/dev/sdz"); err == nil || !strings.Contains(err.Error(), "already has an active") {
+		t.Fatalf("expected flash conflict, got %v", err)
+	}
+}
+
+func TestFlashArtifactUpdatesProgressWhenVerificationSummaryIsMissing(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{flashMessage: `{"dest_path":"/dev/sdz","size_bytes":4096,"verified":true}`})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	job := app.newJob("flash", "titan-15", "titan-22", "/dev/sdz")
+
+	result, err := app.flashArtifact(job.ID, "registry.example/metis/titan-15")
+	if err != nil {
+		t.Fatalf("flashArtifact: %v", err)
+	}
+	if result.SizeBytes != 4096 {
+		t.Fatalf("unexpected flash result: %#v", result)
+	}
+	got := app.job(job.ID)
+	if got == nil || got.Written != 4096 || got.Total != 4096 || !strings.Contains(got.Message, "Verified the latest image write") {
+		t.Fatalf("unexpected flash artifact state: %#v", got)
+	}
+}
+
+func TestFlashOnlyWorkflowFailsVerification(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{flashMessage: `{"dest_path":"/dev/sdz","verified":false}`})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+
+	job, err := app.Flash("titan-15", "titan-22", "/dev/sdz")
+	if err != nil {
+		t.Fatalf("Flash: %v", err)
+	}
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		if got := app.job(job.ID); got != nil && got.Status == JobError {
+			if !strings.Contains(got.Error, "verification did not succeed") {
+				t.Fatalf("unexpected flash verification error: %#v", got)
+			}
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatalf("flash job %s never failed verification: %#v", job.ID, app.job(job.ID))
+}
+
+func TestBuildFlashAndReplaceRejectInvalidInputs(t *testing.T) {
+	kube := remoteWorkflowKubeServer(t, remoteKubeOptions{})
+	installKubeFactory(t, kube)
+	app := remoteTestApp(t, nil)
+	app.artifactStore["titan-15"] = ArtifactSummary{Node: "titan-15", Ref: "registry.example/metis/titan-15:latest"}
+
+	if _, err := app.Build("missing-node"); err == nil || !strings.Contains(err.Error(), "missing-node") {
+		t.Fatalf("expected build inventory error, got %v", err)
+	}
+	if _, err := app.Flash("titan-15", "titan-22", "/dev/sda"); err == nil || !strings.Contains(err.Error(), "not a current flash candidate") {
+		t.Fatalf("expected flash device validation error, got %v", err)
+	}
+	if _, err := app.Replace("titan-15", "titan-22", "/dev/sda"); err == nil || !strings.Contains(err.Error(), "not a current flash candidate") {
+		t.Fatalf("expected replace device validation error, got %v", err)
+	}
+}
--- a/pkg/service/remote.go
+++ b/pkg/service/remote.go
@ -74,7 +74,7 @@ func (a *App) RefreshDevices(host string) ([]Device, error) {
 }

 func (a *App) runBuild(job *Job, flash bool) {
-	nodeSpec, class, err := a.inventory.FindNode(job.Node)
+	_, class, err := a.inventory.FindNode(job.Node)
 	if err != nil {
 		a.failJob(job.ID, err)
 		a.metrics.RecordBuild(job.Node, "error")
@ -158,18 +158,42 @@ func (a *App) runBuild(job *Job, flash bool) {
 		return
 	}

-	a.setJob(job.ID, func(j *Job) {
-		j.Stage = "preflight"
-		j.StageStartedAt = time.Now().UTC()
-		j.Message = fmt.Sprintf("Validating %s and preparing the latest Harbor artifact for %s", prettyDeviceTarget(j.Device), j.Host)
-		j.ProgressPct = 78
-		j.Artifact = artifactRef + ":latest"
-	})
-	if _, err := a.ensureDevice(job.Host, job.Device); err != nil {
+	result, err := a.runFlashSequence(job, artifactRef)
+	if err != nil {
 		a.failJob(job.ID, err)
 		a.metrics.RecordFlash(job.Node, job.Host, "error")
 		return
 	}
+	a.metrics.RecordFlash(job.Node, job.Host, "ok")
+	a.appendFlashEvent(job, artifactRef, result)
+	a.completeFlashJob(job.ID, artifactRef, result)
+}
+
+func (a *App) runFlash(job *Job) {
+	artifactRef := a.artifactRepo(job.Node)
+	result, err := a.runFlashSequence(job, artifactRef)
+	if err != nil {
+		a.failJob(job.ID, err)
+		a.metrics.RecordFlash(job.Node, job.Host, "error")
+		return
+	}
+	a.metrics.RecordFlash(job.Node, job.Host, "ok")
+	a.appendFlashEvent(job, artifactRef, result)
+	a.completeFlashJob(job.ID, artifactRef, result)
+}
+
+func (a *App) runFlashSequence(job *Job, artifactRef string) (RemoteFlashResult, error) {
+	a.setJob(job.ID, func(j *Job) {
+		j.Status = JobRunning
+		j.Stage = "preflight"
+		j.StageStartedAt = time.Now().UTC()
+		j.Message = fmt.Sprintf("Validating %s and preparing the latest Harbor artifact for %s", prettyDeviceTarget(j.Device), j.Host)
+		j.ProgressPct = 80
+		j.Artifact = artifactRef + ":latest"
+	})
+	if _, err := a.ensureDevice(job.Host, job.Device); err != nil {
+		return RemoteFlashResult{}, err
+	}
 	if !strings.HasPrefix(job.Device, "hosttmp://") {
 		if err := deleteNodeObject(job.Node); err != nil {
 			a.appendEvent(Event{
@ -180,66 +204,111 @@ func (a *App) runBuild(job *Job, flash bool) {
 			})
 		}
 	}
-	if err := a.flashArtifact(job.ID, artifactRef); err != nil {
-		a.failJob(job.ID, err)
-		a.metrics.RecordFlash(job.Node, job.Host, "error")
-		return
+	return a.flashArtifact(job.ID, artifactRef)
+}
+
+func (a *App) appendFlashEvent(job *Job, artifactRef string, result RemoteFlashResult) {
+	summary := fmt.Sprintf("Flashed and verified %s latest image on %s", job.Node, job.Host)
+	if strings.HasPrefix(job.Device, "hosttmp://") {
+		summary = fmt.Sprintf("Verified %s latest image on %s host scratch", job.Node, job.Host)
+	}
+	details := map[string]any{
+		"node":              job.Node,
+		"device":            job.Device,
+		"host":              job.Host,
+		"artifact":          artifactRef + ":latest",
+		"dest_path":         result.DestPath,
+		"verified":          result.Verified,
+		"verification_kind": result.VerificationKind,
+	}
+	if strings.TrimSpace(result.BootPartition) != "" {
+		details["boot_partition"] = result.BootPartition
+	}
+	if strings.TrimSpace(result.RootPartition) != "" {
+		details["root_partition"] = result.RootPartition
+	}
+	if len(result.CheckedFiles) > 0 {
+		details["checked_files"] = append([]string{}, result.CheckedFiles...)
 	}
-	a.metrics.RecordFlash(job.Node, job.Host, "ok")
 	a.appendEvent(Event{
 		Time:    time.Now().UTC(),
 		Kind:    "image.flash",
-		Summary: fmt.Sprintf("Flashed %s latest image on %s", job.Node, job.Host),
-		Details: map[string]any{"node": job.Node, "device": job.Device, "host": job.Host, "artifact": artifactRef + ":latest"},
+		Summary: summary,
+		Details: details,
 	})
-	a.completeJob(job.ID, func(j *Job) {
-		j.Stage = "complete"
-		if strings.HasPrefix(j.Device, "hosttmp://") {
-			j.Message = fmt.Sprintf("Test flash complete on %s host /tmp.", j.Host)
-		} else {
-			j.Message = fmt.Sprintf("Flash complete on %s. Move the card into %s and power-cycle it.", j.Host, j.Node)
 }
+
+func (a *App) completeFlashJob(jobID, artifactRef string, result RemoteFlashResult) {
+	a.completeJob(jobID, func(j *Job) {
+		j.Stage = "complete"
 		j.ProgressPct = 100
 		j.Artifact = artifactRef + ":latest"
+		if strings.HasPrefix(j.Device, "hosttmp://") {
+			if strings.TrimSpace(result.VerificationSummary) != "" {
+				j.Message = fmt.Sprintf("%s Test flash complete on %s host /tmp.", strings.TrimRight(result.VerificationSummary, "."), j.Host)
+				return
+			}
+			j.Message = fmt.Sprintf("Verified test flash on %s host /tmp.", j.Host)
+			return
+		}
+		if strings.TrimSpace(result.VerificationSummary) != "" {
+			j.Message = fmt.Sprintf("%s Move the card into %s and power-cycle it.", strings.TrimRight(result.VerificationSummary, "."), j.Node)
+			return
+		}
+		j.Message = fmt.Sprintf("Flash verified on %s. Move the card into %s and power-cycle it.", j.Host, j.Node)
 	})
-
-	_ = nodeSpec
 }

-func (a *App) flashArtifact(jobID, artifactRef string) error {
+func (a *App) flashArtifact(jobID, artifactRef string) (RemoteFlashResult, error) {
+	job := a.job(jobID)
+	if job == nil {
+		return RemoteFlashResult{}, fmt.Errorf("job %s no longer exists", jobID)
+	}
 	nodes := clusterNodes()
 	nodeMap := map[string]clusterNode{}
 	for _, node := range nodes {
 		nodeMap[node.Name] = node
 	}
-	target, ok := nodeMap[a.job(jobID).Host]
+	target, ok := nodeMap[job.Host]
 	if !ok {
-		return fmt.Errorf("flash host %s is not a current cluster node", a.job(jobID).Host)
+		return RemoteFlashResult{}, fmt.Errorf("flash host %s is not a current cluster node", job.Host)
 	}
 	image := a.podImageForArch(target.Arch)
 	if image == "" {
-		return fmt.Errorf("no runner image configured for arch %s", target.Arch)
+		return RemoteFlashResult{}, fmt.Errorf("no runner image configured for arch %s", target.Arch)
 	}
 	a.setJob(jobID, func(j *Job) {
-		j.Stage = "flash"
+		j.Stage = "flash_pull"
 		j.StageStartedAt = time.Now().UTC()
-		j.Message = fmt.Sprintf("Pulling %s and writing it on %s", artifactRef+":latest", j.Host)
+		j.Message = fmt.Sprintf("Pulling %s and preparing it for %s", artifactRef+":latest", prettyDeviceTarget(j.Device))
 		j.ProgressPct = 84
 	})
 	podName := fmt.Sprintf("metis-flash-%d", time.Now().UTC().UnixNano())
-	logs, err := a.runRemotePod(jobID, podName, a.remoteFlashPodSpec(podName, target.Name, image, a.job(jobID).Node, a.job(jobID).Device, artifactRef))
+	logs, err := a.runRemotePod(jobID, podName, a.remoteFlashPodSpec(podName, target.Name, image, job.Node, job.Device, artifactRef))
 	if err != nil {
-		return err
+		return RemoteFlashResult{}, err
+	}
+	var result RemoteFlashResult
+	if err := json.Unmarshal([]byte(strings.TrimSpace(logs)), &result); err != nil {
+		return RemoteFlashResult{}, fmt.Errorf("decode remote flash output: %w: %s", err, strings.TrimSpace(logs))
+	}
+	if !result.Verified {
+		return RemoteFlashResult{}, fmt.Errorf("flash verification did not succeed for %s on %s", prettyDeviceTarget(job.Device), job.Host)
 	}
-	var payload map[string]any
-	if err := json.Unmarshal([]byte(strings.TrimSpace(logs)), &payload); err == nil {
 	a.setJob(jobID, func(j *Job) {
-			if dest, ok := payload["dest_path"].(string); ok && dest != "" {
-				j.Message = fmt.Sprintf("Wrote latest artifact to %s", dest)
+		if result.SizeBytes > 0 {
+			j.Written = result.SizeBytes
+			j.Total = result.SizeBytes
+		}
+		if strings.TrimSpace(result.VerificationSummary) != "" {
+			j.Message = result.VerificationSummary
+			return
+		}
+		if strings.TrimSpace(result.DestPath) != "" {
+			j.Message = fmt.Sprintf("Verified the latest image write at %s", result.DestPath)
 		}
 	})
-	}
-	return nil
+	return result, nil
 }

 func (a *App) heartbeatRemoteJob(jobID string) {
@ -255,8 +324,8 @@ func (a *App) heartbeatRemoteJob(jobID string) {
 			stageStart = j.StartedAt
 		}
 		elapsed := time.Since(stageStart)
-		switch j.Stage {
-		case "build":
+		switch {
+		case j.Stage == "build":
 			progress, message := buildStageHeartbeat(j.Node, j.Builder, elapsed)
 			if progress > j.ProgressPct {
 				j.ProgressPct = progress
@ -264,14 +333,14 @@ func (a *App) heartbeatRemoteJob(jobID string) {
 			if strings.TrimSpace(message) != "" {
 				j.Message = message
 			}
-		case "preflight":
+		case j.Stage == "preflight":
 			if j.ProgressPct < 80 {
 				j.ProgressPct = 80
 			}
 			j.Message = fmt.Sprintf("Validating %s on %s and resolving the latest Harbor artifact", prettyDeviceTarget(j.Device), j.Host)
-		case "flash":
-			if j.Total > 0 && j.Written > 0 {
-				actual := 88 + (float64(j.Written)/float64(j.Total))*10
+		case isFlashStage(j.Stage):
+			if j.Stage == "flash_write" && j.Total > 0 && j.Written > 0 {
+				actual := 92 + (float64(j.Written)/float64(j.Total))*6
 				if actual > 98 {
 					actual = 98
 				}
@ -281,7 +350,7 @@ func (a *App) heartbeatRemoteJob(jobID string) {
 				j.Message = fmt.Sprintf("Writing %s of %s on %s", humanBytes(j.Written), humanBytes(j.Total), j.Host)
 				return
 			}
-			progress, message := flashStageHeartbeat(j.Host, j.Artifact, elapsed)
+			progress, message := flashStagePhaseHeartbeat(j.Stage, j.Host, j.Artifact, elapsed)
 			if progress > j.ProgressPct {
 				j.ProgressPct = progress
 			}
--- a/pkg/service/remote_error_test.go
+++ b/pkg/service/remote_error_test.go
@ -29,7 +29,7 @@ func TestRemoteWorkflowErrorBranches(t *testing.T) {
 	}

 	job = app.newJob("flash", "titan-15", "titan-22", "/dev/sdz")
-	if err := app.flashArtifact(job.ID, "registry.example/metis/titan-15"); err == nil {
+	if _, err := app.flashArtifact(job.ID, "registry.example/metis/titan-15"); err == nil {
 		t.Fatal("expected flashArtifact error")
 	}

@ -260,7 +260,7 @@ func TestFlashArtifactAndHeartbeatBranches(t *testing.T) {
 	app := remoteTestApp(t, nil)

 	job := app.newJob("replace", "titan-15", "missing-host", "/dev/sdz")
-	if err := app.flashArtifact(job.ID, "registry.example/metis/titan-15"); err == nil || !strings.Contains(err.Error(), "not a current cluster node") {
+	if _, err := app.flashArtifact(job.ID, "registry.example/metis/titan-15"); err == nil || !strings.Contains(err.Error(), "not a current cluster node") {
 		t.Fatalf("expected missing host flashArtifact error, got %v", err)
 	}

@ -283,7 +283,7 @@ func TestFlashArtifactAndHeartbeatBranches(t *testing.T) {
 	}

 	app.setJob(job.ID, func(j *Job) {
-		j.Stage = "flash"
+		j.Stage = "flash_write"
 		j.ProgressPct = 80
 		j.Written = 120
 		j.Total = 100
@ -341,7 +341,7 @@ func remoteWorkflowKubeServer(t *testing.T, opts remoteKubeOptions) *httptest.Se
 	buildPhase := defaultString(opts.buildPhase, "Succeeded")
 	buildMessage := defaultString(opts.buildMessage, `{"local_path":"/workspace/build/titan-15.img.xz","compressed":true,"size_bytes":1234,"build_tag":"build-1"}`)
 	flashPhase := defaultString(opts.flashPhase, "Succeeded")
-	flashMessage := defaultString(opts.flashMessage, `{"dest_path":"/var/tmp/metis-flash-test/titan-15.img"}`)
+	flashMessage := defaultString(opts.flashMessage, `{"dest_path":"/var/tmp/metis-flash-test/titan-15.img","verified":true,"verification_kind":"image-file","verification_summary":"Verified image layout at /var/tmp/metis-flash-test/titan-15.img; boot and writable partitions are present."}`)
 	nodes := opts.nodes
 	if nodes == nil {
 		nodes = []map[string]any{
--- a/pkg/service/remote_helpers.go
+++ b/pkg/service/remote_helpers.go
@ -28,7 +28,21 @@ func buildStageHeartbeat(node, builder string, elapsed time.Duration) (float64,
 }

 func flashStageHeartbeat(host, artifact string, elapsed time.Duration) (float64, string) {
+	return flashStagePhaseHeartbeat("flash", host, artifact, elapsed)
+}
+
+func flashStagePhaseHeartbeat(stage, host, artifact string, elapsed time.Duration) (float64, string) {
 	seconds := elapsed.Seconds()
+	switch strings.TrimSpace(stage) {
+	case "flash_pull":
+		return math.Min(88, ramp(seconds, 0, 12, 84, 88)), fmt.Sprintf("Pulling %s from Harbor on %s", artifact, host)
+	case "flash_prepare", "flash_unpack":
+		return math.Min(92, ramp(seconds, 0, 30, 88, 92)), fmt.Sprintf("Preparing the latest %s artifact for writing on %s", artifact, host)
+	case "flash_flush":
+		return math.Min(99, ramp(seconds, 0, 30, 98, 99)), fmt.Sprintf("Flushing the finished image write on %s", host)
+	case "flash_verify":
+		return math.Min(99.8, ramp(seconds, 0, 30, 99, 99.8)), fmt.Sprintf("Verifying the flashed recovery media on %s", host)
+	default:
 		switch {
 		case seconds < 10:
 			return ramp(seconds, 0, 10, 84, 88), fmt.Sprintf("Pulling %s from Harbor on %s", artifact, host)
@ -38,6 +52,11 @@ func flashStageHeartbeat(host, artifact string, elapsed time.Duration) (float64,
 			return math.Min(98, ramp(seconds, 45, 120, 96, 98)), fmt.Sprintf("Flushing buffers and finishing the write on %s", host)
 		}
 	}
+}
+
+func isFlashStage(stage string) bool {
+	return strings.HasPrefix(strings.TrimSpace(stage), "flash")
+}

 func prettyDeviceTarget(path string) string {
 	switch {
--- a/pkg/service/remote_helpers_test.go
+++ b/pkg/service/remote_helpers_test.go
@ -384,3 +384,31 @@ func TestSelectBuilderHostTieBreaksByName(t *testing.T) {
 		t.Fatalf("expected alphabetical tie-breaker, got %s", node.Name)
 	}
 }
+
+func TestFlashPhaseHeartbeatAndManagedPathHelpers(t *testing.T) {
+	cases := []struct {
+		stage   string
+		minimum float64
+		phrase  string
+	}{
+		{stage: "flash_pull", minimum: 84, phrase: "Pulling"},
+		{stage: "flash_prepare", minimum: 88, phrase: "Preparing"},
+		{stage: "flash_unpack", minimum: 90, phrase: "Preparing"},
+		{stage: "flash_flush", minimum: 98, phrase: "Flushing"},
+		{stage: "flash_verify", minimum: 99, phrase: "Verifying"},
+		{stage: "flash", minimum: 90, phrase: "Writing"},
+	}
+	for _, tc := range cases {
+		got, msg := flashStagePhaseHeartbeat(tc.stage, "titan-22", "registry.example/metis/titan-15:latest", 20*time.Second)
+		if got < tc.minimum || !strings.Contains(msg, tc.phrase) {
+			t.Fatalf("flashStagePhaseHeartbeat(%s) = %v %q", tc.stage, got, msg)
+		}
+	}
+
+	if !managedPathsContain("/var/log/pods_/var/tmp", "/var/tmp") {
+		t.Fatal("expected managedPathsContain to match child paths")
+	}
+	if managedPathsContain("/var/log/pods", "/home/atlas") {
+		t.Fatal("managedPathsContain should reject unrelated paths")
+	}
+}
--- a/pkg/service/remote_status.go
+++ b/pkg/service/remote_status.go
@ -19,6 +19,24 @@ type RemoteProgressUpdate struct {
 	TotalBytes   int64   `json:"total_bytes,omitempty"`
 }

+// RemoteFlashResult captures the verified outcome of a remote flash worker run.
+type RemoteFlashResult struct {
+	Node                string   `json:"node,omitempty"`
+	Device              string   `json:"device,omitempty"`
+	DestPath            string   `json:"dest_path,omitempty"`
+	SizeBytes           int64    `json:"size_bytes,omitempty"`
+	Verified            bool     `json:"verified,omitempty"`
+	VerificationKind    string   `json:"verification_kind,omitempty"`
+	VerificationSummary string   `json:"verification_summary,omitempty"`
+	BootPartition       string   `json:"boot_partition,omitempty"`
+	RootPartition       string   `json:"root_partition,omitempty"`
+	BootLabel           string   `json:"boot_label,omitempty"`
+	RootLabel           string   `json:"root_label,omitempty"`
+	BootFSType          string   `json:"boot_fstype,omitempty"`
+	RootFSType          string   `json:"root_fstype,omitempty"`
+	CheckedFiles        []string `json:"checked_files,omitempty"`
+}
+
 // ProgressLogLine formats a progress update for remote worker stdout.
 func ProgressLogLine(update RemoteProgressUpdate) string {
 	data, err := json.Marshal(update)
--- a/pkg/service/server.go
+++ b/pkg/service/server.go
@ -30,6 +30,7 @@ func (a *App) Handler() http.Handler {
 	mux.HandleFunc("/api/state", a.withUIAuth(a.handleState))
 	mux.HandleFunc("/api/devices", a.withUIAuth(a.handleDevices))
 	mux.HandleFunc("/api/jobs/build", a.withUIAuth(a.handleBuild))
+	mux.HandleFunc("/api/jobs/flash", a.withUIAuth(a.handleFlash))
 	mux.HandleFunc("/api/jobs/replace", a.withUIAuth(a.handleReplace))
 	mux.HandleFunc("/api/sentinel/watch", a.withUIAuth(a.handleWatch))
 	mux.HandleFunc("/", a.withUIAuth(a.handleIndex))
@ -106,6 +107,23 @@ func (a *App) handleBuild(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusAccepted, job)
 }

+func (a *App) handleFlash(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	values := requestValues(r)
+	node := values["node"]
+	host := values["host"]
+	device := values["device"]
+	job, err := a.Flash(node, host, device)
+	if err != nil {
+		http.Error(w, err.Error(), statusForJobError(err))
+		return
+	}
+	writeJSON(w, http.StatusAccepted, job)
+}
+
 func (a *App) handleReplace(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
--- a/pkg/service/templates/metis.html
+++ b/pkg/service/templates/metis.html
@ -174,7 +174,7 @@
    }
    .actions{
      display:grid;
-      grid-template-columns:repeat(3,minmax(0,1fr));
+      grid-template-columns:repeat(2,minmax(0,1fr));
      gap:.7rem;
      margin-top:.9rem;
    }
@ -277,7 +277,7 @@
      <div class="stack">
        <article class="card">
          <h2>Replacement Run</h2>
-          <p class="hint">This UI is meant for the one-shot recovery path: build the node image, verify the card on the flash host, then write it and hand off only the physical swap.</p>
+          <p class="hint">Use the mode that matches the recovery step you are in: build a fresh image, flash the latest published image, or run the full build-and-flash path in one shot.</p>
          <div class="form-grid">
            <label>Target node
              <select id="node-select"></select>
@ -296,6 +296,7 @@
          <div class="actions">
            <button class="secondary" id="refresh-devices">Refresh media</button>
            <button class="secondary" id="build-only">Build image only</button>
+            <button class="secondary" id="flash-only">Flash latest image</button>
            <button id="replace-run">Build and flash</button>
          </div>
        </article>
@ -395,6 +396,22 @@
      return seconds + 's';
    }

+    function prettyLabel(value){
+      return String(value || '')
+        .replaceAll('_', ' ')
+        .replace(/\b\w/g, (match)=>match.toUpperCase());
+    }
+
+    function prettyJobKind(kind){
+      switch(kind){
+        case 'build': return 'Build';
+        case 'flash': return 'Flash Latest';
+        case 'replace': return 'Build + Flash';
+        case 'idle': return 'Idle';
+        default: return prettyLabel(kind);
+      }
+    }
+
    function banner(kind, title, text){
      bannerEl.className = 'banner ' + kind;
      bannerTitleEl.textContent = title;
@ -445,10 +462,10 @@
        const wrap = document.createElement('div');
        wrap.className = 'item';
        const statusClass = job.status === 'error' ? 'error' : (job.status === 'done' ? 'done' : (job.status === 'running' ? 'running' : ''));
-        const title = job.kind.toUpperCase() + (job.node ? ' · ' + job.node : '');
+        const title = prettyJobKind(job.kind) + (job.node ? ' · ' + job.node : '');
        const started = fmtTime(job.started_at) + (job.device ? ' · ' + job.device : '') + (job.host ? ' · ' + job.host : '');
        const timingBits = [];
-        if(job.stage){ timingBits.push('stage: ' + job.stage); }
+        if(job.stage){ timingBits.push('stage: ' + prettyLabel(job.stage)); }
        const stageDuration = fmtDuration(job.stage_started_at || job.started_at, job.finished_at);
        if(stageDuration){
          timingBits.push((job.status === 'running' ? 'stage elapsed ' : 'stage duration ') + stageDuration);
@ -538,7 +555,7 @@
      }

      const selectedHost = hostSelect.value || state.default_flash_host;
-      hostNoteEl.textContent = 'Metis will inspect media and run the flash writer on ' + selectedHost + ' through a short-lived in-cluster worker. ' + state.default_flash_host + ' remains the default flash host.';
+      hostNoteEl.textContent = 'Metis will inspect media and run the flash writer/verifier on ' + selectedHost + ' through a short-lived in-cluster worker. ' + state.default_flash_host + ' remains the default flash host.';

      if(state.device_error){
        deviceNoteEl.textContent = state.device_error;
@ -549,11 +566,13 @@
      }

      const artifact = (state.artifacts || {})[nodeSelect.value];
-      artifactNoteEl.textContent = artifact && artifact.ref
-        ? 'Latest published image: ' + artifact.ref + ' (Metis keeps the newest 3 builds in Harbor).'
-        : 'Successful build-only runs publish <node>:latest into Harbor and keep the newest 3 builds per node.';
+      const hasArtifact = !!(artifact && artifact.ref);
+      artifactNoteEl.textContent = hasArtifact
+        ? 'Latest published image: ' + artifact.ref + (artifact.build_tag ? ' · build ' + artifact.build_tag : '') + '. Flash latest writes this image directly; build and flash rebuilds first.'
+        : 'Build image only publishes <node>:latest into Harbor. Flash latest stays disabled until Metis has a recorded latest image.';

      document.getElementById('build-only').disabled = busy || !nodeSelect.value;
+      document.getElementById('flash-only').disabled = busy || !nodeSelect.value || !deviceSelect.value || !!state.device_error || !hasArtifact;
      document.getElementById('refresh-devices').disabled = busy;
      document.getElementById('replace-run').disabled = busy || !nodeSelect.value || !deviceSelect.value || !!state.device_error;
      document.getElementById('sentinel-watch').disabled = busy;
@ -654,6 +673,24 @@
      });
    });

+    document.getElementById('flash-only').addEventListener('click', async ()=>{
+      if(!requireValue(nodeSelect.value, 'Choose the target node whose latest published image should be flashed.')){
+        return;
+      }
+      if(!requireValue(deviceSelect.value, 'Choose removable media before starting a flash-only run.')){
+        return;
+      }
+      if(state.device_error){
+        banner('error', 'Flash host unavailable', state.device_error);
+        return;
+      }
+      await runAction('Starting flash latest', 'Queueing a flash-only run from the latest published Harbor image.', async ()=>{
+        await post('/api/jobs/flash', {node: nodeSelect.value, host: hostSelect.value, device: deviceSelect.value});
+        await refreshState({silent:true});
+        banner('success', 'Flash-only workflow queued', 'Metis is flashing the latest published image for ' + nodeSelect.value + ' onto ' + deviceSelect.value + ' and will verify it before finishing.');
+      });
+    });
+
    document.getElementById('replace-run').addEventListener('click', async ()=>{
      if(!requireValue(nodeSelect.value, 'Choose the target node whose SD card image should be built and flashed.')){
        return;
@ -668,7 +705,7 @@
      await runAction('Starting build and flash', 'Queueing the full replacement workflow now.', async ()=>{
        await post('/api/jobs/replace', {node: nodeSelect.value, host: hostSelect.value, device: deviceSelect.value});
        await refreshState({silent:true});
-        banner('success', 'Replacement workflow queued', 'Metis is building the image for ' + nodeSelect.value + ' and will flash ' + deviceSelect.value + '.');
+        banner('success', 'Replacement workflow queued', 'Metis is rebuilding the image for ' + nodeSelect.value + ', flashing ' + deviceSelect.value + ', and verifying the media before finishing.');
      });
    });

--- a/pkg/service/workflow_test.go
+++ b/pkg/service/workflow_test.go
@ -185,7 +185,7 @@ func fakeKubeServer(t *testing.T) *httptest.Server {
 			case strings.Contains(podName, "build"):
 				message = `{"local_path":"/workspace/build/titan-15.img.xz","compressed":true,"size_bytes":1234,"build_tag":"build-1"}`
 			case strings.Contains(podName, "flash"):
-				message = `{"dest_path":"/var/tmp/metis-flash-test/titan-15.img"}`
+				message = `{"dest_path":"/var/tmp/metis-flash-test/titan-15.img","verified":true,"verification_kind":"image-file","verification_summary":"Verified image layout at /var/tmp/metis-flash-test/titan-15.img; boot and writable partitions are present."}`
 			}
 			_ = json.NewEncoder(w).Encode(map[string]any{
 				"metadata": map[string]any{"name": podName},
--- a/scripts/quality_gate.sh
+++ b/scripts/quality_gate.sh
@ -57,4 +57,4 @@ if [ "${test_rc}" -ne 0 ]; then
 fi

 cd "${repo_root}/testing"
-METIS_USE_EXISTING_COVERAGE=1 go test -v ./...
+METIS_USE_EXISTING_COVERAGE=1 go test -count=1 -v ./...
--- a/testing/coverage_policy.json
+++ b/testing/coverage_policy.json
@ -8,6 +8,7 @@
    "metis/cmd/metis/inject_cmd.go": 95,
    "metis/cmd/metis/main.go": 95,
    "metis/cmd/metis/remote_cmd.go": 95,
+    "metis/cmd/metis/remote_flash.go": 95,
    "metis/cmd/metis/serve_cmd.go": 95,
    "metis/pkg/config/config.go": 95,
    "metis/pkg/facts/aggregate.go": 95,