2026-10-14 21:30:10 +00:00
6 changed files with 585 additions and 18 deletions
@@ -298,6 +298,9 @@ func (h *Holder) orphanLines(now time.Time) []StalledLine {
 			Says: fmt.Sprintf("the walk %s of %s at %s waits for this owner's word, and no delivery that has not ended "+
 				"follows it or is answered by it: `mesh-delivery.show` for the deliveries of %s, and `plans go %s --why …` "+
 				"starts it by hand", w.ID, w.Repository, shortOf(w.Commit, 8), w.Repository, w.ID)})
+		if hold := h.coverHeld(id); hold != "" {
+			out[len(out)-1].Says += "; it is held back meanwhile: " + hold
+		}
 	}
 	return out
 }
@@ -388,6 +391,9 @@ func (h *Holder) words() []func() {
 		if stopped, _ := h.carriesStopped(walk); len(stopped) > 0 {
 			h.waitsWhy[walk] = "it carries " + strings.Join(stopped, ", ") + ", whose delivery was stopped: it is " +
 				"asked to leave that merge out first"
+			if hold := h.coverHeld(walk); hold != "" {
+				h.waitsWhy[walk] = hold
+			}
 			h.Logf("[mesh-delivery] the walk %s is not let go: it carries %s, whose delivery was stopped", walk,
 				strings.Join(stopped, ", "))
 			continue
@@ -479,6 +485,10 @@ func (h *Holder) WalksWaiting() []StalledLine {
 		switch {
 		case len(held) > 0:
 			out = append(out, held...)
+		case h.coverHeld(id) != "":
+			out = append(out, StalledLine{ID: IDOf(w.Repository, w.Commit), State: Published, Walk: id, For: waited,
+				Bound: coverAskBound.String(), H2: "none: it is asked to leave the merge out past the bound",
+				Says: "held back: " + h.coverHeld(id)})
 		case h.waitsWhy[id] != "":
 			out = append(out, StalledLine{ID: IDOf(w.Repository, w.Commit), State: Published, Walk: id, For: waited,
 				Bound: "0s", H2: "none: it goes at its turn", Says: "not let go yet: " + h.waitsWhy[id]})
@@ -150,6 +150,9 @@ func statusOf(d *Delivery) (string, string) {
 	case Delivered:
 		return "success", "delivered"
 	case Failed:
+		if d.coveredStop() {
+			return "success", clip(d.coveredStopSaid(), 140) // its change reached the machines (novox/hq issue 747)
+		}
 		return "failure", clip("failed: "+why, 140)
 	case Superseded:
 		return "warning", clip("superseded: "+why, 140)
@@ -178,7 +181,7 @@ func ViewBody(d *Delivery, g *Group) string {
 	var b strings.Builder
 	fmt.Fprintf(&b, "%s\n**Delivery** `%s` — **%s** since %s\n\n", viewMarker, d.ID, d.State, d.Since.UTC().Format(time.RFC3339))
 	if d.coveredStop() {
-		fmt.Fprintf(&b, "**Covered** after its stop: a later merge that contains it was delivered: %s\n\n", d.CoveredBy)
+		fmt.Fprintf(&b, "**Covered**: %s\n\n", d.coveredStopSaid())
 	}
 	if d.HeldWhy != "" && d.State == Held {
 		fmt.Fprintf(&b, "Held for a person: %s — `mesh-delivery.release` with why lets it go on.\n\n", d.HeldWhy)
@@ -67,6 +67,13 @@ type Holder struct {
 	// leaveRefused is, by walk, what the controller answered when it refused both to leave a stopped merge out and
 	// to stop the walk whole.
 	leaveRefused map[string]string
+	// coverAsked are the deliveries that failed or were stopped whose cover by a later finished walk waits for the
+	// forge's word on containment, worked out each pass (novox/hq issue 747): a walk carrying a merge stopped for one of
+	// them is held back meanwhile, never asked to leave it out before the answer.
+	coverAsked map[string]bool
+	// coverAskedSince is, by delivery, when the forge was first asked about its cover and has not answered: past
+	// coverAskBound the walk is no longer held back for it, and is asked to leave the merge out (review of issue 747).
+	coverAskedSince map[string]time.Time
 	// tried counts the owed effects Flush tried since this owner started, by how each ended (novox/hq issue 407).
 	tried owedTries
 	// marks are the open pull requests read with a ready mark, by owner/repo#number (novox/hq issue 722, ready.go).
@@ -1112,6 +1119,48 @@ func (h *Holder) plan() []func() {
 	// A published delivery whose walk ended done before its word is read the same way (novox/hq issue 474): what
 	// that walk did not build, a later delivered merge may have; and when the cover test says none did, past the
 	// grace, it is stopped saying so — never left waiting for a start that cannot come.
+	// A delivery that failed or was stopped is read for a later finished walk of its repository that delivered its
+	// change after all: a walk that failed in an outage and was resumed, or the walk of a later merge that contains it
+	// (novox/hq issue 747). Read each tick, from what the walks and the kept deliveries say, so one stuck before this
+	// was built clears by itself after a restart.
+	h.coverAsked = map[string]bool{}
+	if h.coverAskedSince == nil {
+		h.coverAskedSince = map[string]time.Time{}
+	}
+	pending := map[string]bool{}
+	for _, d := range h.deliveries {
+		if d.State != Failed && d.State != Stopped || d.coveredStop() {
+			continue
+		}
+		by, ask := h.walkCover(d)
+		if len(ask) > 0 && by == "" {
+			pending[d.ID] = true
+			since, asked := h.coverAskedSince[d.ID]
+			if !asked {
+				since = now
+				h.coverAskedSince[d.ID] = now
+			}
+			// Held back only within the bound: a forge that keeps erroring never holds a walk for good.
+			h.coverAsked[d.ID] = now.Sub(since) < coverAskBound
+		}
+		if by != "" {
+			d.DeliveredBy = by
+			h.tellCovered(d, now)
+			continue
+		}
+		for _, in := range ask {
+			if a := h.askContains(d, in, now); a != nil {
+				asks = append(asks, a)
+			}
+		}
+	}
+
+	for id := range h.coverAskedSince {
+		if !pending[id] {
+			delete(h.coverAskedSince, id)
+		}
+	}
+
 	for _, d := range h.deliveries {
 		ended := d.endedUnstarted()
 		if d.coveredStop() && !d.CoverTold {
@@ -1273,7 +1322,7 @@ func (h *Holder) laterOnItsWay(d *Delivery) string {
 // stays final, and the bus's transition event is not said again.
 func (h *Holder) tellCovered(d *Delivery, now time.Time) {
 	d.CoverTold = true
-	line := oneLine(fmt.Sprintf("%s delivery %s: stopped, %s", now.UTC().Format(time.RFC3339), d.ID, d.coveredStopSaid()))
+	line := oneLine(fmt.Sprintf("%s delivery %s: %s, %s", now.UTC().Format(time.RFC3339), d.ID, d.State, d.coveredStopSaid()))
 	d.Owed = append(d.Owed, Effect{Kind: EffectNote, Commit: d.Commit, Line: line, Since: now})
 	if d.MergedAs != "" && !sameCommit(d.MergedAs, d.Commit) {
 		d.Owed = append(d.Owed, Effect{Kind: EffectNote, Commit: d.MergedAs, Line: line, Since: now})
@@ -1283,7 +1332,7 @@ func (h *Holder) tellCovered(d *Delivery, now time.Time) {
 		state, desc := statusOf(d)
 		d.owe(Effect{Kind: EffectStatus, Commit: d.Commit, Context: "mesh/delivery", State: state, Line: desc, Since: now})
 	}
-	h.Logf("[mesh-delivery] %s: stopped, %s", d.ID, d.coveredStopSaid())
+	h.Logf("[mesh-delivery] %s: %s, %s", d.ID, d.State, d.coveredStopSaid())
 	h.keep(d)
 }

@@ -1294,6 +1343,104 @@ func strandedUncovered(d *Delivery) bool {
 	return d.State == Stopped && d.Stranded != "" && d.CoveredBy == ""
 }

+// walkCover says which later finished walk delivered the change of a delivery that failed or was stopped, or
+// nothing, and which walk commits the forge must still be asked about (novox/hq issue 747). A walk covers it when it
+// is of its repository and trunk, done, made after its merge, its commit containing its merge — the merge itself, or
+// a later one the forge says contains it — and it built every module the delivery's plan moves, each it did not
+// build being one the delivery's own walk said unchanged (issue 611). This is the containment "one walk answers every
+// merge it contains" uses (issue 362, ADR 0276), read after the fact: a failed walk resumed to done answers its own
+// merge, and a later merge's walk answers every merge it contains. A walk that only said a module unchanged for its
+// own merges says nothing of this one's, so it covers no module that way. Walks are read from the controller's records
+// this owner holds and from every delivery's kept walk, so a walk long ended still counts after a restart.
+func (h *Holder) walkCover(d *Delivery) (string, []string) {
+	if d.State != Failed && d.State != Stopped || d.MergedAs == "" || d.Plan == nil || len(d.Plan.Moved) == 0 {
+		return "", nil
+	}
+	var ask []string
+	for _, c := range h.doneWalksOf(d.Repository) {
+		w := c.walk
+		if !sameBranch(w.Branch, d.Base) || !w.Created.IsZero() && w.Created.Before(d.MergedAt.Add(-time.Minute)) {
+			continue
+		}
+		var missing []string
+		for _, m := range d.Plan.Moved {
+			unchanged := false
+			if d.Walk != nil {
+				_, unchanged = d.Walk.Unchanged[m]
+			}
+			if !containsString(w.Moved, m) && !unchanged {
+				missing = append(missing, m)
+			}
+		}
+		if len(missing) > 0 {
+			continue
+		}
+		if !sameCommit(c.commit, d.MergedAs) {
+			yes, known := d.ContainedIn[c.commit]
+			if !known && !containsString(ask, c.commit) {
+				ask = append(ask, c.commit)
+			}
+			if !yes {
+				continue
+			}
+		}
+		return fmt.Sprintf("%s (%s at %s into %s, done, contains its merge %s)", w.ID, d.Repository, shortOf(c.commit, 8),
+			orNone(d.Base), shortOf(d.MergedAs, 8)), nil
+	}
+	return "", ask
+}
+
+// doneWalk is a finished walk and the commit of its repository it carried.
+type doneWalk struct {
+	walk   *WalkSeen
+	commit string
+}
+
+// doneWalksOf are the finished walks of a repository this owner knows, oldest first: the controller's records it
+// holds, and each delivery's kept walk with the commit of its repository that walk carried for it.
+func (h *Holder) doneWalksOf(repository string) []doneWalk {
+	byID := map[string]doneWalk{}
+	for id, s := range h.walks {
+		w := s.walk
+		if w.Release != nil || w.IsBatch() || w.State != walkDone || !strings.EqualFold(w.Repository, repository) {
+			continue
+		}
+		byID[id] = doneWalk{walk: w.Seen(), commit: w.Commit}
+	}
+	for _, o := range h.deliveries {
+		if o.Walk == nil || o.Walk.State != walkDone || !strings.EqualFold(o.Repository, repository) {
+			continue
+		}
+		if _, known := byID[o.Walk.ID]; known {
+			continue
+		}
+		commit := o.AnsweredBy
+		if commit == "" && o.MergedAs != "" && sameCommit(o.Walk.Commit, o.MergedAs) {
+			commit = o.MergedAs
+		}
+		if commit == "" {
+			continue
+		}
+		byID[o.Walk.ID] = doneWalk{walk: o.Walk, commit: commit}
+	}
+	out := make([]doneWalk, 0, len(byID))
+	for _, c := range byID {
+		out = append(out, c)
+	}
+	sort.Slice(out, func(i, j int) bool {
+		if !out[i].walk.Created.Equal(out[j].walk.Created) {
+			return out[i].walk.Created.Before(out[j].walk.Created)
+		}
+		return out[i].walk.ID < out[j].walk.ID
+	})
+	return out
+}
+
+// stopLapsed is whether a member its group stopped for another is stopped for nothing any more (see stopLapsed).
+func (h *Holder) stopLapsed(d *Delivery) bool {
+	return stopLapsed(d, func(id string) *Delivery { return h.deliveries[id] })
+}
+
 // unwalkedPast is whether a merged delivery has gone without a walk past the bound one opens within, read
 // again after it: what holds it for a person, unless something already ends it.
 func (h *Holder) unwalkedPast(d *Delivery, now time.Time) bool {
@@ -1736,7 +1883,8 @@ func (h *Holder) turnsOf(g *Group, members []*Delivery, waits map[string]carryWa
 		// A superseded member a later delivered walk carried counts as reached, as in GroupState: a group counts a
 		// covered member as delivered, so the member after it gets its turn (ADR 0270 decision 2, novox/hq
 		// issues 442 and 445).
-		if d.State.Reached() || d.State == Superseded && d.CoveredBy != "" {
+		// A stop or failure a later walk delivered since counts as reached too (novox/hq issues 480 and 747).
+		if memberReached(d) {
 			continue
 		}
 		if sharing != "" && (d.Walk == nil || d.Walk.ID != sharing) {
@@ -1761,7 +1909,7 @@ func (h *Holder) turnsOf(g *Group, members []*Delivery, waits map[string]carryWa
 			}
 			if w.why != "" {
 				for _, later := range ordered[i+1:] {
-					if a := h.stopInGroup(byID[later.ID], fmt.Sprintf("its group %s stopped: %s superseded, and %s", g.ID,
+					if a := h.stopInGroup(byID[later.ID], d.ID, fmt.Sprintf("its group %s stopped: %s superseded, and %s", g.ID,
 						d.ID, w.why)); a != nil {
 						asks = append(asks, a)
 					}
@@ -1788,9 +1936,13 @@ func (h *Holder) turnsOf(g *Group, members []*Delivery, waits map[string]carryWa
 				continue
 			}
 			return asks
+		case h.stopLapsed(d):
+			// Stopped for a member whose change reached the machines since: it stops nothing more. Its own change is
+			// delivered by a later walk of its repository that contains it, which then covers it (novox/hq issue 747).
+			continue
 		case d.State == Failed || d.State == Stopped:
 			for _, later := range ordered[i+1:] {
-				if a := h.stopInGroup(byID[later.ID], fmt.Sprintf("its group %s stopped: %s %s", g.ID, d.ID, d.State)); a != nil {
+				if a := h.stopInGroup(byID[later.ID], d.ID, fmt.Sprintf("its group %s stopped: %s %s", g.ID, d.ID, d.State)); a != nil {
 					asks = append(asks, a)
 				}
 			}
@@ -2028,7 +2180,7 @@ func mayCarry(c, d *Delivery, module string) bool {
 // controller ends the walk and walks the other merges again without it, and without each later merge of its
 // repository, which contains it. Every member a pass stops on one walk is gathered first, and the walk is asked
 // once, by the first member's ask, after the pass: a member is never walked again because its stop came second.
-func (h *Holder) stopInGroup(d *Delivery, why string) func() {
+func (h *Holder) stopInGroup(d *Delivery, cause, why string) func() {
 	if d == nil || d.State.Final() {
 		return nil
 	}
@@ -2037,6 +2189,7 @@ func (h *Holder) stopInGroup(d *Delivery, why string) func() {
 		h.refuse(err)
 		return nil
 	}
+	d.StoppedFor = cause // the member it was stopped for: once that one is delivered, the stop lapses (novox/hq issue 747)
 	h.moved(d, []Transition{t})
 	// Its open walk; or, its walk stopped for another merge, the batch or walk that walks its merge again (review
 	// of #221): a merge walked again and then stopped by its group is left out there too.
@@ -2118,6 +2271,12 @@ func (h *Holder) carriesStopped(walk string) ([]string, string) {
 		if last := d.Transitions[len(d.Transitions)-1]; last.Event != EvStop || last.By == "" {
 			continue
 		}
+		// A stop whose change a later walk delivered since, or one its group made for a member delivered since,
+		// holds nothing back: the group stops a walk only for a member whose change is still undelivered (novox/hq
+		// issue 747).
+		if d.coveredStop() || h.stopLapsed(d) {
+			continue
+		}
 		// By the merges it names alone: its own commit may be another's merge it no longer answers.
 		if !slices.ContainsFunc(s.walk.Delivery.Merges, func(m WalkMerge) bool {
 			return strings.EqualFold(m.Repository, d.Repository) && sameCommit(m.Commit, d.MergedAs)
@@ -2135,6 +2294,51 @@ func (h *Holder) carriesStopped(walk string) ([]string, string) {
 	return out, why
 }

+// coverAwaited is whether a stopped merge a walk carries, given as `<repository>@<commit>`, waits for the forge's
+// word on whether a later finished walk delivered it or the member its group stopped it for (novox/hq issue 747).
+// It says since when the forge was first asked, the earliest of them. Held only within coverAskBound of the first
+// ask: past it the forge's silence or error lets the walk be asked to leave the merge out. Under the lock.
+func (h *Holder) coverAwaited(merges []string) (time.Time, bool) {
+	var since time.Time
+	awaited := false
+	for _, d := range h.deliveries {
+		if d.State != Stopped || d.MergedAs == "" || !containsString(merges, d.Repository+"@"+d.MergedAs) {
+			continue
+		}
+		for _, id := range []string{d.ID, d.stoppedFor()} {
+			if id == "" || !h.coverAsked[id] {
+				continue
+			}
+			if at := h.coverAskedSince[id]; !awaited || at.Before(since) {
+				since = at
+			}
+			awaited = true
+		}
+	}
+	return since, awaited
+}
+
+// coverHeld says why a walk is held back while the forge is asked whether a later finished walk delivered a stopped
+// merge it carries (novox/hq issue 747), or nothing when it is not. Said by `waits`, `stalled` and `stalled walks`, so
+// a forge that cannot answer is loud. Under the lock.
+func (h *Holder) coverHeld(walk string) string {
+	without, _ := h.carriesStopped(walk)
+	if len(without) == 0 {
+		return ""
+	}
+	since, awaited := h.coverAwaited(without)
+	if !awaited {
+		return ""
+	}
+	return fmt.Sprintf("it carries %s, whose delivery was stopped, and the forge is asked since %s whether a later "+
+		"finished walk delivered it; it is asked to leave the merge out if no answer comes by %s (novox/hq issue 747)",
+		strings.Join(without, ", "), since.Local().Format("15:04:05"), since.Add(coverAskBound).Local().Format("15:04:05"))
+}
+
+// coverAskBound is how long a walk carrying a stopped merge is held back while the forge is asked whether a later
+// finished walk delivered it (novox/hq issue 747); past it, the walk is asked to leave the merge out.
+const coverAskBound = 10 * time.Minute
+
 // lastWhyOf is the reason of a delivery's last transition.
 func lastWhyOf(d *Delivery) string {
 	if len(d.Transitions) == 0 {
@@ -2170,6 +2374,9 @@ func (h *Holder) leaveStopped() []func() {
 		if without, _ := h.carriesStopped(id); len(without) > 0 {
 			said := fmt.Sprintf("its walk %s is not let go: it carries %s, whose delivery was stopped, and is asked to "+
 				"leave it out (novox/hq ADR 0299)", id, strings.Join(without, ", "))
+			if hold := h.coverHeld(id); hold != "" {
+				said = "its walk " + id + " is held back: " + hold
+			}
 			if r := h.leaveRefused[id]; r != "" {
 				said += "; the controller refused: " + r
 			}
@@ -2193,6 +2400,9 @@ func (h *Holder) leaveStopped() []func() {
 			delete(h.leaveRefused, id)
 			continue
 		}
+		if _, awaited := h.coverAwaited(without); awaited {
+			continue // held back, not stopped, until the forge says whether a later walk delivered it (issue 747)
+		}
 		// Once per record of it: the record that answers an ask is newer. Asked again after five minutes, should
 		// the ask have gone nowhere.
 		if a, asked := h.leaveAsked[id]; asked && seen.walk.Revision <= a.revision && now.Sub(a.at) < 5*time.Minute {
@@ -2314,18 +2524,28 @@ func againWords(a StopAnswer) string {
 func GroupState(g *Group, members []*Delivery) (string, string) {
 	count := map[State]int{}
 	reached, ended := 0, 0
-	var uncovered []string
+	var uncovered, lapsed []string
+	byID := map[string]*Delivery{}
+	for _, d := range members {
+		byID[d.ID] = d
+	}
 	for _, d := range members {
-		count[d.State]++
 		if d.State.Final() {
 			ended++
 		}
 		switch {
-		case d.State.Reached(), d.State == Superseded && d.CoveredBy != "":
+		case memberReached(d):
+			// Reached, whatever its final state: a failure or stop a later walk delivered since is no failure of the
+			// group (novox/hq issue 747).
 			reached++
+			continue
+		case stopLapsed(d, func(id string) *Delivery { return byID[id] }):
+			lapsed = append(lapsed, d.ID)
+			continue
 		case d.State == Superseded:
 			uncovered = append(uncovered, d.ID)
 		}
+		count[d.State]++
 	}
 	n := len(members)
 	switch {
@@ -2335,6 +2555,11 @@ func GroupState(g *Group, members []*Delivery) (string, string) {
 		return "stopped", "a member was stopped"
 	case n > 0 && reached == n:
 		return "delivered", "every member is delivered"
+	case g.Closed && len(lapsed) > 0 && reached+len(lapsed) == n:
+		// Stopped for a member delivered since: its own change waits for a later walk of its repository, which then
+		// covers it (novox/hq issue 747).
+		return "delivering", fmt.Sprintf("%d of %d delivered; %s, stopped for a member delivered since, waits for a "+
+			"later walk of its repository", reached, n, strings.Join(lapsed, ", "))
 	case g.Closed && n > 0 && ended == n:
 		return "stopped", supersededWhy + strings.Join(uncovered, ", ")
 	case g.Closed && g.Check != nil && (g.Check.OutOfDate != "" || g.Check.Verdict == "" ||
@@ -0,0 +1,258 @@
+package main
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+// novox/hq issue 747: in the group fix/a-module-moves-only-when-its-program-changes, the controller's member #336
+// (merged as 5d22d7df) failed at 22:32 during an outage of the forge's tools. The walk of the controller's next merge,
+// #339 at 60cc9ec3, which contains 5d22d7df, failed with it and was resumed to done by a rebuild. mesh-delivery still
+// held #336 failed, so its group stopped every later walk of the catalogue that carried the catalogue member's merge
+// 2edef5a0: the catalogue could deliver nothing. A failed or stopped delivery is covered once a later finished walk of
+// its repository that contains its merge built its modules, and a group stops a walk only for a member whose change is
+// still undelivered.
+//
+// The shape is the live state of 2026-10-14 23:07, as mesh-delivery.show gave it, read back after a restart: the
+// controller holds none of the walks of the night any more, only the walk of the catalogue's next merge.
+
+const (
+	g747              = "fix/a-module-moves-only-when-its-program-changes"
+	ctl747, cat747    = "novox/mesh-controller", "novox/mesh-catalog"
+	head336, merge336 = "b34055f580d4e2a4", "5d22d7df86c73452"
+	head339, merge339 = "e4acab32d6a20ade", "60cc9ec363dfa7c6"
+	head301, merge301 = "d94764f00168471f", "2edef5a00ae05605"
+	merge307          = "0f76b6e2aaaaaaaa"
+)
+
+var (
+	at747                  = time.Date(2026, 10, 14, 20, 21, 6, 0, time.UTC)
+	id336, id339, id301    = IDOf(ctl747, head336), IDOf(ctl747, head339), IDOf(cat747, head301)
+	unchangedRouteProxy747 = map[string]string{"route-proxy": "its build source holds none of the changed files"}
+)
+
+// night747 is the stuck state, with the forge saying, or not, that 60cc9ec3 contains 5d22d7df.
+func night747(t *testing.T, contained bool) *world { return night747With(t, contained, nil) }
+
+// night747With is night747 with #339's walk having built only the modules given, saying the others unchanged.
+func night747With(t *testing.T, contained bool, built []string) *world {
+	t.Helper()
+	return night747Over(t, func(f *fakeForge) { f.contains[merge336+" in "+merge339] = contained }, built)
+}
+
+// night747Over is night747With with the forge set as given: one that is not told the pair cannot say.
+func night747Over(t *testing.T, set func(*fakeForge), built []string) *world {
+	t.Helper()
+	at := at747
+	failedAt := at.Add(11 * time.Minute)
+	store := newMemStore()
+	moved339, unchanged339 := []string{"build-agent", "mesh-controller"}, unchangedRouteProxy747
+	if built != nil {
+		moved339, unchanged339 = built, map[string]string{}
+		for _, m := range []string{"build-agent", "mesh-controller", "route-proxy"} {
+			if !containsString(built, m) {
+				unchanged339[m] = "its build source holds none of the files #339 changed"
+			}
+		}
+	}
+	m336 := &Delivery{ID: id336, Repository: ctl747, Commit: head336, Number: 336, Base: "main", Branch: g747, Group: g747,
+		State: Failed, Since: failedAt, Created: at.Add(-time.Hour), MergedAs: merge336, MergedAt: at,
+		AnsweredBy: merge336, Check: &Verdict{Gate: "pass"},
+		Plan: planMoving(ctl747, "build-agent", "mesh-controller", "route-proxy"),
+		Walk: &WalkSeen{ID: "plan-336", Commit: merge336, State: walkFailed, Branch: "main", MovedSaid: true,
+			Note: "mesh-controller failed to build in tier 0", Created: at.Add(7 * time.Minute), Tiers: 2,
+			Unchanged: unchangedRouteProxy747},
+		Transitions: []Transition{{At: failedAt, From: Delivering, To: Failed, Event: EvFailed,
+			Why: "its walk failed, carrying its own commit"}}}
+	m339 := &Delivery{ID: id339, Repository: ctl747, Commit: head339, Number: 339, Base: "main", Branch: "fix/726",
+		State: Failed, Since: failedAt, Created: at.Add(-10 * time.Minute), MergedAs: merge339, MergedAt: at.Add(7 * time.Minute),
+		AnsweredBy: merge339, Check: &Verdict{Gate: "pass"}, Plan: planMoving(ctl747, "mesh-controller"),
+		// Its walk failed with #336's, and a rebuild resumed it to done: the record it keeps says so.
+		Walk: &WalkSeen{ID: "plan-339", Commit: merge339, State: walkDone, Branch: "main", MovedSaid: true,
+			Moved: moved339, Unchanged: unchanged339,
+			Created: at.Add(11 * time.Minute), Tiers: 2, Tier: 2},
+		Transitions: []Transition{{At: failedAt, From: Delivering, To: Failed, Event: EvFailed,
+			Why: "its walk failed, carrying its own commit"}}}
+	m301 := &Delivery{ID: id301, Repository: cat747, Commit: head301, Number: 301, Base: "main", Branch: g747, Group: g747,
+		State: Stopped, Since: failedAt, Created: at.Add(-2 * time.Hour), MergedAs: merge301, MergedAt: at.Add(7 * time.Second),
+		Check: &Verdict{Gate: "pass"}, Plan: planMoving(cat747, "build-agent", "route-proxy"),
+		Transitions: []Transition{{At: failedAt, From: Ready, To: Stopped, Event: EvStop, By: byOwner,
+			Why: "its group " + g747 + " stopped: " + id336 + " failed"}}}
+	for _, d := range []*Delivery{m336, m339, m301} {
+		if err := store.PutDelivery(d); err != nil {
+			t.Fatal(err)
+		}
+	}
+	g := &Group{ID: g747, Members: []string{id301, id336}, Closed: true, Order: []string{id336, id301}, Said: "failed",
+		OrderOf: commitsOf([]*Delivery{m301, m336}), Check: &GroupCheck{Asked: "check-1", At: at.Add(-time.Minute),
+			Verdict: "pass", Summary: "both compose", Commits: commitsOf([]*Delivery{m301, m336})}}
+	if err := store.PutGroup(g); err != nil {
+		t.Fatal(err)
+	}
+	ctlr := newFakeController()
+	// The catalogue's next merge: its walk carries 2edef5a0, merged before it and never walked, and waits for its word.
+	ctlr.put(Walk{ID: "plan-cat", Repository: cat747, Branch: "main", Commit: merge307, Created: at.Add(46 * time.Minute),
+		State: walkBuilding, Tiers: [][]string{{"gitea"}}, Modules: map[string]*WalkModule{"gitea": {}},
+		Delivery: &WalkDelivery{Awaits: "mesh-delivery", Merges: []WalkMerge{
+			{Repository: cat747, Commit: merge301, Carried: merge307}, {Repository: cat747, Commit: merge307}}}})
+	ctlr.mergedAt[merge301], ctlr.mergedAt[merge307] = m301.MergedAt, at.Add(46*time.Minute)
+	forge := newFakeForge()
+	set(forge)
+	w := newWorldOver(t, store, ctlr, forge, at.Add(47*time.Minute))
+	if err := w.h.Reconcile(); err != nil {
+		t.Fatal(err)
+	}
+	w.settleAll()
+	return w
+}
+
+func groupState747(w *world) (string, string) {
+	g := w.h.groups[g747]
+	return GroupState(g, w.h.membersOf(g))
+}
+
+// **A failed member is covered by a later finished walk that contains it**: #339's walk, done at 60cc9ec3, which the
+// forge says contains 5d22d7df, built build-agent and mesh-controller, and #336's own walk said route-proxy unchanged.
+// #336 stays failed, reads covered by that walk on its pull request, and its group no longer reads failed. #339, whose
+// own walk was resumed to done, is covered by it too.
+func TestAFailedMemberIsCoveredByALaterDoneWalkThatContainsIt(t *testing.T) {
+	w := night747(t, true)
+	d := w.delivery(id336)
+	if state, desc := statusOf(d); d.State != Failed || state != "success" || !strings.Contains(desc, "covered after its failure") ||
+		!strings.Contains(desc, "plan-339") {
+		t.Fatalf("#336's status reads %s %q", state, desc)
+	}
+	if s := statusOn(w, ctl747, head336); !strings.HasPrefix(s, "success") {
+		t.Fatalf("the forge was told %q of #336", s)
+	}
+	if state, desc := statusOf(w.delivery(id339)); state != "success" || !strings.Contains(desc, "plan-339") {
+		t.Fatalf("#339 reads %s %q; want it covered by its own walk, resumed to done", state, desc)
+	}
+	if state, why := groupState747(w); state == "failed" || state == "stopped" {
+		t.Fatalf("the group reads %s: %s", state, why)
+	}
+	// Told once, and kept: a restart tells nothing again.
+	notes := len(w.forge.notesOn(merge336))
+	again := newWorldOver(t, w.store, w.ctl, w.forge, w.now.Add(time.Minute))
+	again.settleAll()
+	if state, _ := statusOf(again.delivery(id336)); len(w.forge.notesOn(merge336)) != notes || state != "success" {
+		t.Fatalf("a restart told it again or forgot it: %d notes, was %d", len(w.forge.notesOn(merge336)), notes)
+	}
+}
+
+// **The group then no longer stops the other repository's walk**: the catalogue member was stopped for #336 alone,
+// so the walk of the catalogue's next merge, which carries its merge, is neither stopped nor held back, and the
+// group waits for that walk to deliver the catalogue member's change.
+func TestACoveredMemberNoLongerStopsTheOtherRepositorysWalk(t *testing.T) {
+	w := night747(t, true)
+	if len(w.ctl.withouts) > 0 || containsString(w.ctl.stops, "plan-cat") {
+		t.Fatalf("the catalogue's walk was stopped: without %v, stops %v", w.ctl.withouts, w.ctl.stops)
+	}
+	if stopped, _ := w.h.carriesStopped("plan-cat"); len(stopped) > 0 {
+		t.Fatalf("the catalogue's walk is held back for %v", stopped)
+	}
+	if state, why := groupState747(w); state != "delivering" || !strings.Contains(why, id301) {
+		t.Fatalf("the group reads %s: %s; want delivering, the catalogue member waiting for a later walk", state, why)
+	}
+	// Once a later walk of the catalogue that contains its merge built its modules, it is covered, and the group is
+	// delivered.
+	w.forge.contains[merge301+" in "+merge307] = true
+	r := w.ctl.walk("plan-cat")
+	sent := w.now
+	r.Modules = map[string]*WalkModule{}
+	for _, m := range []string{"build-agent", "route-proxy", "gitea"} {
+		r.Modules[m] = &WalkModule{State: "built", SentAt: &sent}
+	}
+	r.State = walkDone
+	w.h.WalkMoved(w.ctl.put(r))
+	w.later(time.Minute)
+	w.settleAll()
+	if state, desc := statusOf(w.delivery(id301)); state != "success" || !strings.Contains(desc, "plan-cat") {
+		t.Fatalf("the catalogue member reads %s %q", state, desc)
+	}
+	if state, why := groupState747(w); state != "delivered" {
+		t.Fatalf("the group reads %s: %s", state, why)
+	}
+}
+
+// **A failed member not contained still stops it**: the forge says 60cc9ec3 does not contain 5d22d7df, so #336's change
+// never reached the machines; it stays failed and uncovered, its group failed, and the catalogue's walk that carries
+// the stopped member's merge is asked to leave it out.
+func TestAFailedMemberNotContainedStillStopsTheOtherRepositorysWalk(t *testing.T) {
+	w := night747(t, false)
+	d := w.delivery(id336)
+	if state, desc := statusOf(d); d.State != Failed || state != "failure" {
+		t.Fatalf("#336 is %s and reads %s %q", d.State, state, desc)
+	}
+	if state, _ := groupState747(w); state != "failed" {
+		t.Fatalf("the group reads %s", state)
+	}
+	if len(w.ctl.withouts) == 0 || !strings.HasPrefix(w.ctl.withouts[0], "plan-cat without "+cat747+"@"+merge301) {
+		t.Fatalf("the catalogue's walk was not asked to leave the stopped merge out: %v", w.ctl.withouts)
+	}
+}
+
+// **A later walk that only said a module unchanged covers nothing of an earlier merge that moves it**: #339's walk
+// built mesh-controller alone and said build-agent unchanged for #339's own files, which says nothing of #336's; only
+// #336's own walk says that of its change (route-proxy). #336 stays failed and its group still stops the catalogue.
+func TestALaterWalksUnchangedCoversNoModuleOfAnEarlierMerge(t *testing.T) {
+	w := night747With(t, true, []string{"mesh-controller"})
+	if state, desc := statusOf(w.delivery(id336)); state != "failure" {
+		t.Fatalf("#336 reads %s %q, though no walk built build-agent for it", state, desc)
+	}
+	if state, _ := groupState747(w); state != "failed" {
+		t.Fatalf("the group reads %s", state)
+	}
+	if len(w.ctl.withouts) == 0 {
+		t.Fatal("the catalogue's walk was not asked to leave the stopped merge out")
+	}
+}
+
+// **A forge that cannot say holds the walk only within the bound** (review of issue 747): while the forge errors on
+// whether 60cc9ec3 contains 5d22d7df, the catalogue's walk is held back, loudly, neither stopped nor asked to leave the
+// merge out, and #336 still reads failed. Past the bound the forge's silence holds nothing back any more: the walk
+// is asked to leave the stopped merge out, as with no later walk at all.
+func TestAForgeThatCannotSayHoldsTheWalkOnlyWithinTheBound(t *testing.T) {
+	for _, c := range []struct {
+		name string
+		set  func(*fakeForge)
+	}{
+		{"erroring", func(f *fakeForge) { f.containsDown = true }},
+		{"not answering for the pair", func(*fakeForge) {}},
+	} {
+		t.Run(c.name, func(t *testing.T) {
+			w := night747Over(t, c.set, nil)
+			if len(w.ctl.withouts) > 0 || len(w.ctl.stops) > 0 {
+				t.Fatalf("within the bound the walk was not held: without %v, stops %v", w.ctl.withouts, w.ctl.stops)
+			}
+			if state, desc := statusOf(w.delivery(id336)); state != "failure" {
+				t.Fatalf("#336 reads %s %q while the forge cannot say", state, desc)
+			}
+			said := ""
+			for _, l := range w.h.WalksWaiting() {
+				if l.Walk == "plan-cat" {
+					said += l.Says
+				}
+			}
+			w.later(3 * time.Minute) // past the grace an unheld walk is given, so `stalled` lists it
+			w.settleAll()
+			for _, l := range w.h.Stalled() {
+				if l.Walk == "plan-cat" {
+					said += " | " + l.Says
+				}
+			}
+			if strings.Count(said, "the forge is asked since") != 2 {
+				t.Fatalf("the hold is not said by `stalled walks` and `stalled`: %q", said)
+			}
+			if len(w.ctl.withouts) > 0 || len(w.ctl.stops) > 0 {
+				t.Fatalf("within the bound the walk was not held: without %v, stops %v", w.ctl.withouts, w.ctl.stops)
+			}
+			w.later(coverAskBound + time.Minute)
+			w.settleAll()
+			if len(w.ctl.withouts) == 0 || !strings.HasPrefix(w.ctl.withouts[0], "plan-cat without "+cat747+"@"+merge301) {
+				t.Fatalf("past the bound the walk was not asked to leave the stopped merge out: %v", w.ctl.withouts)
+			}
+		})
+	}
+}
@@ -83,6 +83,14 @@ type Delivery struct {
 	// CoverTold is whether the forge was told that such a stop was covered since: its status, its view and its note
 	// (novox/hq issue 480). Kept, so a restart tells it once, and a stop covered before this was built is told too.
 	CoverTold bool `json:"cover_told,omitempty"`
+	// DeliveredBy says, for a delivery that failed or was stopped, the later finished walk of its repository whose
+	// commit contains its merge and which built every module it moves — each it did not build, its own walk said
+	// unchanged: its change reached the machines after all (novox/hq issue 747). Its state stays final, as a covered
+	// stop's does (issue 480), and it reads covered: its group counts it as delivered.
+	DeliveredBy string `json:"delivered_by,omitempty"`
+	// StoppedFor is, for a member its group stopped, the member whose end stopped it (novox/hq issue 747): once that
+	// member's change reached the machines, the stop has lapsed, and holds no walk of its repository back.
+	StoppedFor string `json:"stopped_for,omitempty"`
 	// TurnAwaits says, for a group member whose turn waits for a later merge to carry a superseded member before it,
 	// which merges and until when; TurnAwaitsUntil is that moment, which bounds the wait (ADR 0276 decision 9,
 	// novox/hq issue 445). `show` shows both, and `stalled` says them past that moment.
@@ -303,18 +311,77 @@ func (d *Delivery) FromForgesWord() bool {

 // shownOnItsPullRequest is whether its view and status are kept on its pull request: not for history, whose
 // pull request the forge may no longer hold — or holds under its number another one.
-// coveredStop is whether a delivery stopped because its walk ended done before its word without building its modules
-// (novox/hq issue 474) was covered since: a later merge into its trunk that contains it was delivered, carrying every
-// module it moves to every machine running it (ADR 0270's cover test, kept as CoveredBy). Its state stays stopped —
-// final, as a covered superseded member stays superseded (issue 442) — and it reads covered, by that merge (novox/hq
-// issue 480). A stop for any other reason never reads covered.
+// coveredStop is whether a delivery that ended stopped or failed was covered since, and reads covered. A stop
+// because its walk ended done before its word without building its modules (novox/hq issue 474) is covered when a
+// later merge into its trunk that contains it was delivered, carrying every module it moves to every machine running
+// it (ADR 0270's cover test, kept as CoveredBy; issue 480). Any stop or failure is covered when a later finished walk
+// of its repository whose commit contains its merge built its modules (DeliveredBy, novox/hq issue 747). Its state
+// stays final, as a covered superseded member stays superseded (issue 442), and it reads covered, by that merge or
+// walk. A person's stop with a cover found only while it was held keeps its error.
 func (d *Delivery) coveredStop() bool {
-	return d.State == Stopped && d.Stranded != "" && d.CoveredBy != ""
+	switch d.State {
+	case Stopped:
+		return d.Stranded != "" && d.CoveredBy != "" || d.DeliveredBy != ""
+	case Failed:
+		return d.DeliveredBy != ""
+	}
+	return false
 }

-// coveredStopSaid is how a covered stop reads: on the forge's status, in its view and note, and in `show`.
+// coveredStopSaid is how a covered stop or failure reads: on the forge's status, in its view and note, and in `show`.
 func (d *Delivery) coveredStopSaid() string {
-	return "covered after its stop: a later merge that contains it was delivered: " + d.CoveredBy
+	ended := "its stop"
+	if d.State == Failed {
+		ended = "its failure"
+	}
+	if d.Stranded != "" && d.CoveredBy != "" {
+		return "covered after " + ended + ": a later merge that contains it was delivered: " + d.CoveredBy
+	}
+	return "covered after " + ended + ": a later walk that contains it was delivered: " + d.DeliveredBy
+}
+
+// memberReached is whether a group counts a member as delivered: its change reached the machines, or had nothing to
+// reach them with — delivered, history or covered, a superseded member a later delivered walk carried (issue 442),
+// or a stop or failure covered since (issues 480 and 747).
+func memberReached(d *Delivery) bool {
+	return d.State.Reached() || d.State == Superseded && d.CoveredBy != "" || d.coveredStop()
+}
+
+// stoppedFor is the member whose end stopped this one in its group: kept since novox/hq issue 747, and read from the
+// stop's reason for a stop made before ("its group <id> stopped: <member> …").
+func (d *Delivery) stoppedFor() string {
+	if d.StoppedFor != "" || d.State != Stopped || d.Group == "" {
+		return d.StoppedFor
+	}
+	prefix := "its group " + d.Group + " stopped: "
+	for i := len(d.Transitions) - 1; i >= 0; i-- {
+		t := d.Transitions[i]
+		if t.Event != EvStop {
+			continue
+		}
+		if t.By != byOwner || !strings.HasPrefix(t.Why, prefix) {
+			return ""
+		}
+		member, _, _ := strings.Cut(strings.TrimPrefix(t.Why, prefix), " ")
+		return strings.TrimRight(member, ",;:")
+	}
+	return ""
+}
+
+// stopLapsed is whether a member its group stopped for another member is stopped for nothing any more: that member's
+// change reached the machines since — delivered, or its failure covered by a later walk (novox/hq issue 747). Its own
+// change is still to deliver, by a later walk of its repository that contains it; its stop holds none back. find
+// gives a delivery by its id.
+func stopLapsed(d *Delivery, find func(string) *Delivery) bool {
+	if d.State != Stopped || d.coveredStop() {
+		return false
+	}
+	by := d.stoppedFor()
+	if by == "" || by == d.ID {
+		return false
+	}
+	o := find(by)
+	return o != nil && memberReached(o)
 }

 func (d *Delivery) shownOnItsPullRequest() bool {
@@ -72,6 +72,10 @@ func (h *Holder) waitsFor(d *Delivery) string {
 			return "its walk: " + clip(d.Walk.Note, 120)
 		}
 	case Stopped:
+		if h.stopLapsed(d) {
+			return "a later walk of its repository that contains its merge: its group stopped it for " + d.stoppedFor() +
+				", whose change was delivered since (novox/hq issue 747)"
+		}
 		if strandedUncovered(d) {
 			return "a later delivered merge to carry " + strings.Join(d.notMovedBy(), ", ") + ": it is stopped, and " +
 				"listed by stalled until one does (novox/hq issue 480)"