internal/apply/apply.go

@@ -948,19 +948,28 @@ func applyContainer(ctx context.Context, r *declaration.Container, run Runner, c
 	out := begin(r)
 	want := containerSpec(r)
 
+	cri, err := containerRuntime(ctx, run)
+	if err != nil {
+		return out, fmt.Errorf("%w, so nothing can be said about %q", err, r.Name)
+	}
+
 	// A scheduled step is state that is present, not a container to start (novox/hq ADR 0053).
 	// Installing it records the schedule and reports the node current at once — the deliberate
 	// inversion of run-once, which gates. The recurring run is fired by the host's Scheduler off the
 	// clock, re-established from this declaration each apply, and NEVER here — so installing does not
-	// run the container and does not even need a runtime present. Checked before the runtime probe
-	// for exactly that reason.
+	// RUN the container.
+	//
+	// It does, however, ensure the pinned image is present now. A service or a run-once container
+	// gets its image as a side effect of `docker run`; a scheduled step is never run at apply, so
+	// without this its image would be absent from the node until the first scheduled fire — which
+	// would pay the whole pull latency then, and leave tooling that expects the image present after
+	// apply looking at a node that does not have it. Ensuring the image is not running it, so the
+	// no-run invariant holds.
 	if r.Schedule != "" {
-		return applySchedule(r, want, previous)
+		if err := ensureImage(ctx, cri, r.Image, run); err != nil {
+			return out, err
 		}
-
-	cri, err := containerRuntime(ctx, run)
-	if err != nil {
-		return out, fmt.Errorf("%w, so nothing can be said about %q", err, r.Name)
+		return applySchedule(r, want, previous)
 	}
 
 	if r.RunOnce {
@@ -1130,6 +1139,30 @@ func foregroundRunArgs(r *declaration.Container, want string) []string {
 	return args
 }
 
+// ensureImage makes the pinned image present on the node without running anything.
+//
+// A service or a run-once container gets its image as a side effect of `docker run` — the first run
+// pulls it. A scheduled step is installed but deliberately never run at apply (novox/hq ADR 0053), so
+// nothing would pull its image until the first scheduled fire: the image is absent from the node
+// right after a successful apply, the first run pays the whole pull latency, and tooling that expects
+// the image present after apply finds it missing. This fetches the same bytes `docker run` would, and
+// stops short of starting the container.
+//
+// Idempotent, and it reads back (novox/hq ADR 0018): an image already present is left as is, and a
+// pull that reported success but left nothing there is a failure, not a convergence.
+func ensureImage(ctx context.Context, cri, image string, run Runner) error {
+	if _, err := run(ctx, cri, "image", "inspect", image); err == nil {
+		return nil
+	}
+	if _, err := run(ctx, cri, "pull", image); err != nil {
+		return fmt.Errorf("pulling image %s: %w", image, err)
+	}
+	if _, err := run(ctx, cri, "image", "inspect", image); err != nil {
+		return fmt.Errorf("image %s is not present after pulling it: %w", image, err)
+	}
+	return nil
+}
+
 // applySchedule installs a scheduled step: it records the schedule as present and reports the node
 // current, without running anything (novox/hq ADR 0053).
 //

internal/apply/schedule.go

@@ -203,8 +203,9 @@ func (s *Scheduler) fire(ctx context.Context, j *scheduledJob) {
 	s.log(fmt.Sprintf("scheduled step %s: run completed", j.id))
 }
 
-// runtime detects the container runtime once and caches it. A scheduled step does not need one to be
-// installed (see applySchedule), only to be fired, so detection is deferred to here.
+// runtime detects the container runtime once and caches it. The Scheduler needs one only to fire a
+// run, so detection is deferred to here — separate from the apply, which does its own probe when it
+// ensures a scheduled step's image is present (see applyContainer).
 func (s *Scheduler) runtime(ctx context.Context) (string, error) {
 	s.mu.Lock()
 	cached := s.cri

internal/apply/schedule_test.go

@@ -85,11 +85,25 @@ func scheduledContainer(t *testing.T, schedule string) *declaration.Container {
 
 func TestInstallingAScheduleDoesNotRunItAndReportsCurrent(t *testing.T) {
 	// The deliberate inversion of run-once: the schedule is state that is present, so the apply is
-	// current as soon as it is recorded — nothing is run, and no runtime is even probed.
-	var calls []string
+	// current as soon as it is recorded. Installing it ensures the pinned image is present (a
+	// scheduled step is never run at apply, so nothing else pulls it), but it NEVER runs the
+	// container — no `docker run` fires it, which is the invariant that matters (novox/hq ADR 0053).
+	var fired bool  // a `docker run` — the container was started
+	var pulled bool // an image reported present was pulled anyway
 	run := func(ctx context.Context, name string, args ...string) (string, error) {
-		calls = append(calls, name+" "+strings.Join(args, " "))
-		return "", errors.New("installing a schedule must not run any command")
+		switch args[0] {
+		case "info":
+			return "27.0\n", nil // a container runtime answers the apply's probe
+		case "image":
+			return "", nil // `image inspect`: the pinned image is already present
+		case "pull":
+			pulled = true
+			return "", nil
+		case "run":
+			fired = true
+			return "", errors.New("installing a schedule must not run the container")
+		}
+		return "", nil
 	}
 	d := parseTrusted(t, `{"declaration":1,"resources":[
 	  {"id":"sync","type":"container","name":"sync","image":"`+pinned+`","schedule":"0 3 * * *"}
@@ -99,8 +113,11 @@ func TestInstallingAScheduleDoesNotRunItAndReportsCurrent(t *testing.T) {
 	if err != nil {
 		t.Fatalf("installing a schedule failed the apply: %v", err)
 	}
-	if len(calls) != 0 {
-		t.Errorf("installing a schedule ran commands, so it did more than record state: %v", calls)
+	if fired {
+		t.Error("installing a schedule ran the container — it installs state, it does not fire it")
+	}
+	if pulled {
+		t.Error("installing a schedule pulled an image it had just found present")
 	}
 	if report.Outcomes[0].Action != "created" {
 		t.Errorf("an installed schedule was not reported created: %+v", report.Outcomes[0])
@@ -114,7 +131,7 @@ func TestInstallingAScheduleDoesNotRunItAndReportsCurrent(t *testing.T) {
 		t.Error("an installed schedule recorded no marker, so a re-apply cannot tell it is unchanged")
 	}
 
-	// And a re-apply of the same declaration is unchanged and still runs nothing.
+	// And a re-apply of the same declaration is unchanged and still fires nothing.
 	report2, _, err := Apply(context.Background(), archHost(t), d, state, store.OriginCarried, run, nil, nil)
 	if err != nil {
 		t.Fatal(err)
@@ -122,6 +139,59 @@ func TestInstallingAScheduleDoesNotRunItAndReportsCurrent(t *testing.T) {
 	if report2.Changed() {
 		t.Errorf("re-installing the same schedule reported a change: %+v", report2.Outcomes)
 	}
+	if fired {
+		t.Error("re-installing a schedule ran the container")
+	}
+}
+
+func TestInstallingAScheduleEnsuresItsImageIsPresentWithoutStartingIt(t *testing.T) {
+	// A scheduled step is never run at apply, so `docker run` — which is what pulls a service's or a
+	// run-once step's image — never fetches it. Without an explicit pull the image is absent from the
+	// node until the first scheduled fire, which then pays the whole pull latency and, until it runs,
+	// leaves tooling that expects the image present after apply looking at a node without it. So the
+	// apply ensures the image present: when it is absent it is pulled, and still nothing is run.
+	imagePresent := false
+	var pulledImage string
+	var fired bool
+	run := func(ctx context.Context, name string, args ...string) (string, error) {
+		switch args[0] {
+		case "info":
+			return "27.0\n", nil
+		case "image": // `image inspect <image>`
+			if imagePresent {
+				return "", nil
+			}
+			return "", errors.New("no such image")
+		case "pull":
+			pulledImage = args[len(args)-1]
+			imagePresent = true // a real runtime leaves the image present after a pull
+			return "", nil
+		case "run":
+			fired = true
+			return "", nil
+		}
+		return "", nil
+	}
+	d := parseTrusted(t, `{"declaration":1,"resources":[
+	  {"id":"sync","type":"container","name":"sync","image":"`+pinned+`","schedule":"0 3 * * *"}
+	]}`)
+
+	report, state, err := Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
+	if err != nil {
+		t.Fatalf("installing a schedule whose image was absent failed the apply: %v", err)
+	}
+	if pulledImage != pinned {
+		t.Errorf("installing a schedule did not pull its pinned image (pulled %q, want %q)", pulledImage, pinned)
+	}
+	if fired {
+		t.Error("installing a schedule ran the container — ensuring the image is present is not running it")
+	}
+	if report.Outcomes[0].Action != "created" {
+		t.Errorf("an installed schedule was not reported created: %+v", report.Outcomes[0])
+	}
+	if _, ok := state.Find("sync"); !ok {
+		t.Fatal("an installed schedule was not recorded as applied")
+	}
 }
 
 func TestAScheduledStepDoesNotGateWhatFollows(t *testing.T) {