fix(image): guard against downgrade suggestions on fly image show/update

internal/command/image/show.go

@@ -165,8 +165,11 @@ func showMachineImage(ctx context.Context, app *fly.AppCompact) error {
 			}
 		}
 
-		// Exclude machines that are already running the latest version
-		if machine.ImageRef.Digest == latest.Digest {
+		// Exclude machines that are already running the latest version, and
+		// skip cases where the resolver returned an older or non-newer build
+		// (e.g. a stale pinned minor tag at a lower fly.version than the
+		// machine's current rolling tag) to avoid suggesting downgrades.
+		if !IsUpdateCandidate(machine, latest) {
 			continue
 		}
 		updatable = append(updatable, machine)

internal/command/image/update_check.go

@@ -0,0 +1,43 @@
+package image
+
+import (
+	"strings"
+
+	"github.com/hashicorp/go-version"
+	fly "github.com/superfly/fly-go"
+)
+
+// IsUpdateCandidate reports whether latest is a strictly newer build than the
+// machine's current image. It guards against a backend resolver bug where
+// asking for the latest details of a rolling tag (e.g. "flyio/postgres-flex:16")
+// returns an older fly.version than the rolling tag's current one, which would
+// otherwise surface as a spurious "update available" — actually a downgrade.
+//
+// When either fly.version label is missing or unparseable (e.g. custom images),
+// falls back to a digest-inequality check so we preserve the prior behavior for
+// cases that don't use semver-tagged builds.
+func IsUpdateCandidate(machine *fly.Machine, latest *fly.ImageVersion) bool {
+	if machine == nil || latest == nil {
+		return false
+	}
+	if machine.ImageRef.Digest == latest.Digest {
+		return false
+	}
+
+	current := strings.TrimPrefix(machine.ImageVersion(), "v")
+	candidate := strings.TrimPrefix(latest.Version, "v")
+	if current == "" || candidate == "" {
+		return true
+	}
+
+	curV, err := version.NewVersion(current)
+	if err != nil {
+		return true
+	}
+	latV, err := version.NewVersion(candidate)
+	if err != nil {
+		return true
+	}
+
+	return latV.GreaterThan(curV)
+}

internal/command/image/update_machines.go

@@ -288,7 +288,7 @@ func resolveImage(ctx context.Context, machine fly.Machine) (string, error) {
 			return "", err
 		}
 
-		if latestImage != nil {
+		if latestImage != nil && IsUpdateCandidate(&machine, latestImage) {
 			image = latestImage.FullImageRef()
 		}
 

internal/command/status/machines.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	fly "github.com/superfly/fly-go"
+	imagecmd "github.com/superfly/flyctl/internal/command/image"
 	"github.com/superfly/flyctl/internal/command/postgres"
 	"github.com/superfly/flyctl/internal/config"
 	"github.com/superfly/flyctl/internal/flapsutil"
@@ -125,8 +126,10 @@ func RenderMachineStatus(ctx context.Context, app *fly.AppCompact, out io.Writer
 			latest = latestImage
 		}
 
-		// Exclude machines that are already running the latest version
-		if machine.ImageRef.Digest == latest.Digest {
+		// Exclude machines that are already running the latest version, and
+		// skip cases where the resolver returned an older or non-newer build
+		// to avoid suggesting downgrades.
+		if !imagecmd.IsUpdateCandidate(machine, latest) {
 			continue
 		}
 		updatable = append(updatable, machine)
@@ -319,8 +322,10 @@ func renderPGStatus(ctx context.Context, app *fly.AppCompact, machines []*fly.Ma
 			return fmt.Errorf("major version mismatch detected")
 		}
 
-		// Exclude machines that are already running the latest version
-		if machine.ImageRef.Digest == latest.Digest {
+		// Exclude machines that are already running the latest version, and
+		// skip cases where the resolver returned an older or non-newer build
+		// to avoid suggesting downgrades.
+		if !imagecmd.IsUpdateCandidate(machine, latest) {
 			continue
 		}
 		updatable = append(updatable, machine)