Merge pull request 'Gate: merge turns, a merge waits for a running check of its repository, merges on a carried verdict with no second ask (ADR 0548, issue 568)' (#493) from feat/548-one-check into main

modules/gitea/test/trunk.test.ts

@@ -34,6 +34,9 @@ test("both statuses say the head and the trunk commit the verdict judged, first,
   const [old] = statusesFor({ ...c, trunk: undefined, gate: { verdict: "pass", summary: "every machine composes" } });
   assert.equal(old.description, "pass: every machine composes");
   assert.equal(trunkNamed(old.description), undefined);
+  // ADR 0548 §8: a carried verdict's line names the head on the new trunk first, so the merge tool merges it on that trunk.
+  assert.equal(trunkNamed(`pass ${HEAD.slice(0, 12)} on ${MOVED.slice(0, 12)} | carried from ${TRUNK.slice(0, 12)}, mesh-catalog 0123456789ab | unit 0 run, 4 kept`),
+    MOVED.slice(0, 12));
 });
 
 test("a trunk's move puts an open head's merge check out of date, naming both commits, unless a check is on its way", () => {

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/adr548_test.go

@@ -0,0 +1,246 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	sdk "git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// One check per delivery (novox/hq ADR 0548), the gate's part: nothing merges into a repository while a check of other heads
+// judges it (§2); an approved merge holds a turn on its repositories (§3); a held merge past its bound is a stalled line, read
+// and handed by two tools (§4); an approved delivery whose trunk moved merges on its carried verdict with no second ask (§8).
+
+const otherHead = "c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3"
+
+// approvedLone is a lone delivery into oneRepo whose check passed, approved by the operator (the world approves at once).
+func approvedLone(w *world) string {
+	w.t.Helper()
+	p := pr(oneRepo, 1, oneHead, "feat/one")
+	requiresCheck(w, p)
+	w.h.PullUpdated(p)
+	putCheckerVerdict(w, "pass", headOf(oneRepo, 1, oneHead))
+	w.h.CommitStatus(checkStatus(oneRepo, oneHead, "success", oneTrunk))
+	return IDOf(oneRepo, oneHead)
+}
+
+// memTurns is the bucket turns in memory; it logs each write with the merges the fake bridge had made by then.
+type memTurns struct {
+	mu     sync.Mutex
+	m      map[string]sdk.Turn
+	log    []string
+	merges func() int
+}
+
+func newMemTurns(w *world) *memTurns {
+	return &memTurns{m: map[string]sdk.Turn{}, merges: func() int { return len(w.forge.merges) }}
+}
+
+func (f *memTurns) All() (map[string]sdk.Turn, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	out := map[string]sdk.Turn{}
+	for k, v := range f.m {
+		out[k] = v
+	}
+	return out, nil
+}
+
+func (f *memTurns) Put(t sdk.Turn) error {
+	if _, err := sdk.EncodeTurn(t); err != nil {
+		return err
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.m[t.Repository] = t
+	f.log = append(f.log, fmt.Sprintf("put %s after %d merges", t.Repository, f.merges()))
+	return nil
+}
+
+func (f *memTurns) Delete(repository string) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	delete(f.m, repository)
+	f.log = append(f.log, fmt.Sprintf("delete %s after %d merges", repository, f.merges()))
+	return nil
+}
+
+func (f *memTurns) said() string { f.mu.Lock(); defer f.mu.Unlock(); return strings.Join(f.log, "; ") }
+
+func TestOneCheckPerDeliveryAtTheGate(t *testing.T) {
+	for name, run := range map[string]func(t *testing.T){
+		// §2: a merge into a repository a running verdict names is not written to merges, and is written on that verdict's pass.
+		"an approved merge waits for a running check on its repository and merges on its end": func(t *testing.T) {
+			w := newWorld(t)
+			putCheckerVerdict(w, "running", headOf(oneRepo, 9, otherHead))
+			id := approvedLone(w)
+			w.settleAll()
+			if w.op.count() != 1 || len(w.forge.merges) != 0 {
+				t.Fatalf("asked %d times, merges %v: want the Approve asked and the merge held", w.op.count(), w.forge.merges)
+			}
+			d := w.delivery(id)
+			if d.Ready == nil || !strings.Contains(d.Ready.Waits, "waits for the check of g") || !strings.Contains(d.Ready.Waits, oneRepo) ||
+				d.Ready.HeldSince == nil {
+				t.Fatalf("the merge does not say what it waits for: %+v", d.Ready)
+			}
+			// §9: deliveries says what it waits for.
+			for _, l := range w.h.Deliveries("", "", "", false) {
+				if l.ID == id && !strings.Contains(l.Waits, "approved; waits for the check of g") {
+					t.Errorf("deliveries says it waits for %q", l.Waits)
+				}
+			}
+			// §4: past 30 minutes the held merge is a stalled line naming the check it waits for and since when.
+			for _, l := range w.h.Stalled() {
+				if l.ID == id {
+					t.Fatalf("a stalled line within the bound: %+v", l)
+				}
+			}
+			w.later(turnBound + time.Minute)
+			w.settleAll()
+			var line *StalledLine
+			for _, l := range w.h.Stalled() {
+				if l.ID == id {
+					line = &l
+				}
+			}
+			if line == nil || line.Bound != "30m0s" || !strings.Contains(line.Says, "waits for the check of g") || !strings.Contains(line.Says, "held since") ||
+				!strings.Contains(line.Says, "checker_status") || !strings.Contains(line.H2, "delivery_hand_now") {
+				t.Fatalf("the stalled line of the held merge = %+v", line)
+			}
+			putCheckerVerdict(w, "pass", headOf(oneRepo, 9, otherHead))
+			w.settleAll()
+			if len(w.forge.merges) != 1 || w.op.count() != 1 {
+				t.Fatalf("after the check's end: merges %v, asked %d times; want merged with no second ask", w.forge.merges, w.op.count())
+			}
+		},
+		"a running check on another repository holds nothing": func(t *testing.T) {
+			w := newWorld(t)
+			putCheckerVerdict(w, "running", headOf(oneRepo2, 9, otherHead))
+			approvedLone(w)
+			w.settleAll()
+			if len(w.forge.merges) != 1 {
+				t.Fatalf("merges %v: a check of another repository held the merge (%s)", w.forge.merges, w.logs())
+			}
+		},
+		"the delivery's own running verdict does not hold it": func(t *testing.T) {
+			w := newWorld(t)
+			w.op.auto = false
+			id := approvedLone(w)
+			w.settleAll()
+			putCheckerVerdict(w, "running", headOf(oneRepo, 1, oneHead)) // its own heads judged again (a carry)
+			for _, k := range w.op.open() {
+				w.op.answer(k, OptionApprove)
+			}
+			w.settleAll()
+			if d := w.delivery(id); len(w.forge.merges) != 1 || d.Ready == nil || d.Ready.HeldSince != nil {
+				t.Fatalf("merges %v, run %+v: its own check held it", w.forge.merges, d.Ready)
+			}
+		},
+		// §3: the turn is written before the verdicts are read for the merge, and deleted after the last merge.
+		"a lone merge's turn is written before it is handed and deleted once it merged": func(t *testing.T) {
+			w := newWorld(t)
+			turns := newMemTurns(w)
+			w.h.Turns = turns
+			approvedLone(w)
+			w.settleAll()
+			if len(w.forge.merges) != 1 || turns.said() != "put "+oneRepo+" after 0 merges; delete "+oneRepo+" after 1 merges" {
+				t.Fatalf("merges %v; the turns were %q", w.forge.merges, turns.said())
+			}
+		},
+		"a group's turns stand on every member's repository until its last member merged": func(t *testing.T) {
+			w := newWorld(t)
+			turns := newMemTurns(w)
+			w.h.Turns = turns
+			a, b := pr(oneRepo, 1, oneHead, "feat/two"), pr(oneRepo2, 2, oneHead2, "feat/two")
+			requiresCheck(w, a, b)
+			w.h.PullUpdated(a)
+			w.h.PullUpdated(b)
+			w.h.wantForge()
+			putCheckerVerdict(w, "pass", headOf(oneRepo, 1, oneHead), headOf(oneRepo2, 2, oneHead2))
+			w.h.CommitStatus(checkStatus(oneRepo, oneHead, "success", oneTrunk))
+			w.h.CommitStatus(checkStatus(oneRepo2, oneHead2, "success", oneTrunk))
+			for range 3 {
+				w.settleAll()
+			}
+			want := "put " + oneRepo2 + " after 0 merges; put " + oneRepo + " after 0 merges; delete " + oneRepo2 + " after 2 merges; delete " + oneRepo + " after 2 merges"
+			if len(w.forge.merges) != 2 || turns.said() != want {
+				t.Fatalf("merges %v; the turns were %q, want %q", w.forge.merges, turns.said(), want)
+			}
+		},
+		// §8: an approved delivery whose trunk moved goes back to proposed, waits for its carried verdict rather than being
+		// handed on the old one, and merges on it with no second ask.
+		"an approved merge whose trunk moved merges on its carried verdict with no second ask": func(t *testing.T) {
+			w := newWorld(t)
+			putCheckerVerdict(w, "running", headOf(oneRepo, 9, otherHead)) // holds the approved merge (§2)
+			id := approvedLone(w)
+			w.settleAll()
+			if w.op.count() != 1 || len(w.forge.merges) != 0 {
+				t.Fatalf("asked %d times, merges %v; want approved and held", w.op.count(), w.forge.merges)
+			}
+			w.h.PullMerged(merged(oneRepo, 5, otherHead, oneTrunk2)) // a merge at the forge moves the trunk
+			putCheckerVerdict(w, "pass", headOf(oneRepo, 9, otherHead))
+			w.settleAll()
+			if len(w.forge.merges) != 0 {
+				t.Fatalf("merges %v: handed on a verdict judged on the old trunk", w.forge.merges)
+			}
+			d := w.delivery(id)
+			if d.Ready == nil || !strings.Contains(d.Ready.Waits, "being carried") {
+				t.Fatalf("after the trunk moved it waits for %q, want its verdict carried", d.Ready.Waits)
+			}
+			// The checker's carried line: the head on the new trunk, carried from the old one.
+			carried := checkStatus(oneRepo, oneHead, "success", oneTrunk2)
+			carried.Description = "pass " + oneHead[:12] + " on " + oneTrunk2[:12] + " | carried from " + oneTrunk[:12] + " | unit 0 run, 4 kept"
+			if head, trunk := checkLine(carried.Description); head != oneHead[:12] || trunk != oneTrunk2[:12] {
+				t.Fatalf("the carried line reads as %s on %s", head, trunk)
+			}
+			if head, trunk := checkLine("failed: a test"); head != "" || trunk != "" {
+				t.Fatalf("a line that names no commits gave %q %q", head, trunk)
+			}
+			putCheckerVerdict(w, "pass", headOf(oneRepo, 1, oneHead))
+			w.h.CommitStatus(carried)
+			w.settleAll()
+			if w.op.count() != 1 {
+				t.Errorf("the Approve was asked %d times, want once: it stands through the carry", w.op.count())
+			}
+			if d := w.delivery(id); d.Check == nil || d.Check.Trunk != oneTrunk2[:12] || len(w.forge.merges) != 1 {
+				t.Errorf("after the carry: verdict %+v, merges %v; want merged on the carried verdict", d.Check, w.forge.merges)
+			}
+		},
+		// §4: delivery_turns reads every turn with the check it waits for; delivery_hand_now hands a held merge at once on the
+		// operator's word, and refuses one no check holds.
+		"the turns are read, and a held merge is handed now on the operator's word": func(t *testing.T) {
+			w := newWorld(t)
+			w.h.Turns = newMemTurns(w)
+			putCheckerVerdict(w, "running", headOf(oneRepo, 9, otherHead))
+			id := approvedLone(w)
+			w.settleAll()
+			read := w.h.TurnsRead()
+			lines := read["turns"].([]TurnLine)
+			if len(lines) != 1 || lines[0].Repository != oneRepo || len(lines[0].Turn.Waiting) != 1 || lines[0].Turn.Waiting[0].WaitsFor == "" ||
+				!strings.Contains(lines[0].Waits["feat/one"].(string), "the check g.") || read["written"] != true {
+				t.Fatalf("delivery_turns = %+v", read)
+			}
+			if _, err := w.h.HandNow(id, ""); err == nil || !strings.Contains(err.Error(), "why") {
+				t.Errorf("a hand without the operator's why: %v", err)
+			}
+			if _, err := w.h.HandNow(IDOf(oneRepo2, oneHead2), "x"); err == nil {
+				t.Error("an unknown delivery was handed")
+			}
+			if _, err := w.h.HandNow(id, "the operator, on telegram: merge it now"); err != nil {
+				t.Fatal(err)
+			}
+			w.settleAll()
+			if len(w.forge.merges) != 1 || w.delivery(id).Ready.HandNow == "" {
+				t.Fatalf("merges %v after the hand", w.forge.merges)
+			}
+			if _, err := w.h.HandNow(id, "again"); err == nil {
+				t.Error("a merged delivery was handed again")
+			}
+		},
+	} {
+		t.Run(name, run)
+	}
+}

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/conditions.go

@@ -224,6 +224,9 @@ func (h *Holder) nextStall(now time.Time) time.Time {
 			consider(r.RefusedSince.Add(h.answeredRefusalBound(d.Repository)))
 			consider(r.RefusedSince.Add(outOfDateFor))
 		}
+		if r.HeldSince != nil {
+			consider(r.HeldSince.Add(turnBound))
+		}
 	}
 	return next
 }

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/holder.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"git.novox.be/novox/mesh-sdk/go/asks"
+	sdk "git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
 // The holder of the mesh-delivery seat (novox/hq ADR 0239, to-be 47): the one writer of deliveries and
@@ -75,8 +76,14 @@ type Holder struct {
 	// unchecked are the open pull requests' heads seen without a merge check (unchecked.go).
 	unchecked map[string]unchecked
 	// checker are the checker's verdicts by the hash of the heads they judged, as its verdicts bucket holds them
-	// (onestatus.go, issue 1302).
+	// (onestatus.go, issue 1302); runningSince when this owner first saw each running (ADR 0548 §2, turns.go).
-	checker map[string]checkerVerdict
+	checker      map[string]checkerVerdict
+	runningSince map[string]time.Time
+	// Turns is the gate's bucket turns (turns.go, ADR 0548 §3); nil keeps none. turnsHeld are the turns as written there,
+	// by repository, read once at the first look (turnsLoaded).
+	Turns       TurnStore
+	turnsHeld   map[string]sdk.Turn
+	turnsLoaded bool
 	// tried counts the owed effects Flush tried since this owner started, by how each ended (novox/hq issue 407).
 	tried owedTries
 	// forgeWanted is whether the forge's open pull requests are to be read at the next React: a check may have
@@ -126,6 +133,7 @@ func (h *Holder) init() {
 	h.lostRead = map[string]time.Time{}
 	h.unchecked = map[string]unchecked{}
 	h.checker = map[string]checkerVerdict{}
+	h.runningSince, h.turnsHeld = map[string]time.Time{}, map[string]sdk.Turn{}
 	h.started = h.Now()
 }
 

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/keeps.go

@@ -6,7 +6,7 @@ import "git.novox.be/novox/mesh-sdk/go/announce"
 // issue 1790): the module says it itself, from its code, before it serves, and a reader is granted what it said
 // (clause 3). A state is readable when another module's manifest reads it (keeps_test.go names the readers). keeps_test.go holds the list to the
 // manifest's `state`, and keeps_integration_test.go that the module announces it on a bus.
-var Kept = []announce.State{{Name: "asks", Readable: true}, {Name: "conditions"}, {Name: "deliveries"}, {Name: "groups"}, {Name: "merges", Readable: true}, {Name: "owed", Readable: true}, {Name: "pulls", Readable: true}, {Name: "source", Readable: true}}
+var Kept = []announce.State{{Name: "asks", Readable: true}, {Name: "conditions"}, {Name: "deliveries"}, {Name: "groups"}, {Name: "merges", Readable: true}, {Name: "owed", Readable: true}, {Name: "pulls", Readable: true}, {Name: "source", Readable: true}, {Name: "turns", Readable: true}}
 
 // announceKept says Kept through keeps, which is stdio.Keeps.
 func announceKept(keeps func(...announce.State) error) error { return keeps(Kept...) }

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/keeps_test.go

@@ -17,6 +17,9 @@ var readers = map[string][]string{
 	"pulls":  {"build-agent"}, // in mesh-controller
 	"owed":   {"mesh-delivery-forge-bridge"},
 	"source": {"mesh-delivery-indexer", "mesh-delivery-checker"},
+	// ADR 0548 §3, §4: the checker reads the merge turns and claims no check of a repository one names; the gate alone writes
+	// them (a state is written by its owner's account alone, ADR 0495 §3: announcing it readable grants a read, never a write).
+	"turns": {"mesh-delivery-checker"},
 }
 
 // 1790/S: the states the module announces are the states its manifest declares, no more, no fewer, and the readable

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/main.go

@@ -65,6 +65,7 @@ func main() {
 		Operator: kvOperator{},
 		Merges:   kvMerges{},
 		Source:   kvSource{},
+		Turns:    kvTurns{},
 		Owed:     kvOwed{},
 		Pulls:    kvPulls{},
 		// The gate says what stalled to the operator itself (issue 1275, ADR 0437 §9).
@@ -357,6 +358,24 @@ func tools(h *Holder, l *listening) []stdio.Tool {
 				}
 				return h.Close(strArg(a, "id"), strArg(a, "why"))
 			}},
+		{Name: "delivery_turns",
+			Description: "Every merge turn (novox/hq ADR 0548 §3): per repository, the approved merges that wait to merge into it in the order of " +
+				"their Approve, the check of another delivery each waits for and since when, whether the gate wrote the turn to its bucket " +
+				"turns yet (the checker claims no check of a repository a turn names), and the bound past which a held merge is a stalled " +
+				"line. Read-only.",
+			Run: func(map[string]any) (any, error) { return h.TurnsRead(), nil }},
+		{Name: "delivery_hand_now",
+			Description: "On the operator's word, hand an approved merge held for another delivery's running check to the merge at once " +
+				"(novox/hq ADR 0548 §4): the check it waited for runs on and is carried to the new trunk after the merge. Refused for a " +
+				"delivery that is not an approved merge held by a check, naming why. The why is kept on the delivery.",
+			Input: map[string]any{"type": "object", "properties": map[string]any{"id": str("the delivery's id (owner/repository@commit)"),
+				"why": str("the operator's word, kept on the delivery")}, "required": []string{"id", "why"}},
+			Run: func(a map[string]any) (any, error) {
+				if err := need(a, "id", "why"); err != nil {
+					return nil, err
+				}
+				return h.HandNow(strArg(a, "id"), strArg(a, "why"))
+			}},
 		{Name: "delivery_status",
 			Description: "Whether this owner works: how many deliveries in each state, the groups, what is owed to " +
 				"the forge and the bus and not yet done, how many owed effects were tried since it started (done, failed " +

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/manifest_test.go

@@ -91,9 +91,10 @@ func TestItClaimsTheDeliverySeatAndFollowsWhatItHandles(t *testing.T) {
 	if !reflect.DeepEqual(m.Emits, []string{"transition", "group", "merged"}) {
 		t.Fatalf("emits %v", m.Emits)
 	}
-	// Eight buckets, and no `asked` (the teller asks, ADR 0437 §6): ADR 0450 §3, and the conditions it raised (issue 1275).
+	// Nine buckets, and no `asked` (the teller asks, ADR 0437 §6): ADR 0450 §3, the conditions it raised (issue 1275) and the
+	// merge turns (ADR 0548 §3).
 	buckets := m.buckets()
-	if !reflect.DeepEqual(buckets, []string{"deliveries", "groups", "pulls", "asks", "merges", "owed", "source", "conditions"}) {
+	if !reflect.DeepEqual(buckets, []string{"deliveries", "groups", "pulls", "asks", "merges", "owed", "source", "conditions", "turns"}) {
 		t.Fatalf("state %v", buckets)
 	}
 	// What it reads: the teller's answers and the checker's verdicts (issue 1302). The carry from today's module's buckets, the

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/onestatus.go

@@ -72,8 +72,12 @@ func (h *Holder) CheckerVerdictChanged(key string, value []byte) {
 	if i := strings.LastIndex(key, "."); i >= 0 {
 		hash = key[i+1:]
 	}
+	if h.runningSince == nil {
+		h.runningSince = map[string]time.Time{}
+	}
 	if len(value) == 0 || string(value) == "null" {
 		delete(h.checker, hash)
+		delete(h.runningSince, hash)
 		h.Poke()
 		return
 	}
@@ -85,6 +89,11 @@ func (h *Holder) CheckerVerdictChanged(key string, value []byte) {
 	if v.Heads == "" {
 		v.Heads = hash
 	}
+	if prev, ok := h.checker[v.Heads]; v.State == checkerRunning && (!ok || prev.State != checkerRunning) {
+		h.runningSince[v.Heads] = h.Now() // a check starts: a merge it holds says since when (ADR 0548 §2)
+	} else if v.State != checkerRunning {
+		delete(h.runningSince, v.Heads)
+	}
 	h.checker[v.Heads] = v
 	h.Poke()
 }

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/onestatus_test.go

@@ -199,14 +199,3 @@ func TestAClosedPullRequestAsksNoForgetChecks(t *testing.T) {
 	w.h.PullUpdated(p)
 	w.h.PullClosed(p)
 }
-
-// 1302: the mesh/check line gives the head and the trunk it judged.
-func TestTheCheckLineGivesHeadAndTrunk(t *testing.T) {
-	head, trunk := checkLine("pass " + oneHead[:12] + " on " + oneTrunk[:12] + " | unit 4 run, 0 kept | group g of 2 pull requests")
-	if head != oneHead[:12] || trunk != oneTrunk[:12] {
-		t.Fatalf("head %q trunk %q", head, trunk)
-	}
-	if head, trunk = checkLine("failed: a test"); head != "" || trunk != "" {
-		t.Fatalf("a line that names no commits gave %q %q", head, trunk)
-	}
-}

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/ready.go

@@ -121,6 +121,13 @@ type ReadyRun struct {
 	Declined *time.Time `json:"declined,omitempty"`
 	Warrant  string     `json:"warrant,omitempty"`
 	Refused  string     `json:"refused,omitempty"`
+
+	// One check per delivery (novox/hq ADR 0548 §2, §4, turns.go): HeldSince is when the approved merge began to wait for the
+	// check of other heads HeldFor names (its verdict key), running on a repository it goes into; HandNow the operator's word
+	// that handed it at once past that check.
+	HeldSince *time.Time `json:"held_since,omitempty"`
+	HeldFor   string     `json:"held_for,omitempty"`
+	HandNow   string     `json:"hand_now,omitempty"`
 }
 
 // MergeBranch is the one branch this owner merges into (novox/hq ADR 0398 §4): a merge into any other is its author's.
@@ -244,6 +251,9 @@ func (h *Holder) readyAsks(now time.Time) []func() {
 		if waits == "" {
 			waits, approvalAsk = h.approval(d, now)
 		}
+		if waits == "" && gates {
+			waits = h.turnWaits(d, now) // nothing merges into a repository while a check of other heads judges it (ADR 0548 §2)
+		}
 		if waits != r.Waits {
 			r.Waits = waits
 			h.keep(d)
@@ -267,6 +277,7 @@ func (h *Holder) readyAsks(now time.Time) []func() {
 			asks = append(asks, a)
 		}
 	}
+	asks = append(asks, h.turnWrites()...) // the merge turns, after the holds of this look (ADR 0548 §3)
 	asks = append(asks, h.settleMerges()...)
 	asks = append(asks, h.settleForgeMerges()...)
 	asks = append(asks, h.withdrawnKeys()...)
@@ -376,6 +387,9 @@ func (h *Holder) readyWaits(d *Delivery) string {
 	case d.State == Proposed && d.outOfDate() != "" && d.AskedAgain != nil:
 		return "its check against the trunk's head is asked and has not answered"
 	case d.State == Proposed && d.outOfDate() != "" && d.Check.Passes() && h.covering(d) != nil:
+		// Approved, and its trunk moved: the checker carries its verdict to the trunk's head by its package digests (ADR 0548
+		// §5, §8). The Approve stands and is not asked again; the merge waits for the carried verdict, not a fresh check.
+		return "approved; its verdict is being carried to the trunk's head " + shortOf(d.TrunkNow, 12) + " (" + d.outOfDate() + ")"
 	case d.State == Proposed && d.outOfDate() != "":
 		return "its verdict is out of date: its check against the trunk's head is asked before the operator is"
 	case d.State == Proposed && d.AskedAgain != nil:

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/turns.go

@@ -0,0 +1,454 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	sdk "git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **One check per delivery** (novox/hq ADR 0548 §2 to §4, issue 568). While a check runs, nothing merges into a repository it
+// judges, and an approved merge holds a turn on its repositories so no new check starts there:
+//
+//   - the hold (§2): an approved merge is handed to the forge bridge only when no verdict of the checker's verdicts bucket in
+//     the state running names, among its trunk heads, a repository the merge goes into; the verdict of the merge's own heads
+//     excepted. The gate watches that bucket already (onestatus.go), so the verdict leaving running gives the waiting merge its
+//     turn at once, with no timer. Siblings a check reads beside are not held (§2). Only while mesh/check gates the merge;
+//   - the turn (§3): before it reads the verdicts for a merge, the gate writes one key per repository the merge goes into in its
+//     bucket turns (`<owner>.<name>`, sdk.TurnsKey): the deliveries that wait there in the order of their Approve, the check
+//     each waits for and since when; for a group on every member's repository until its last member merged. The checker reads
+//     the bucket and claims no check of a repository a turn names. The key goes when the last delivery in it merged or left;
+//   - the bound and the tools (§4): a merge held past turnBound is a stalled line; delivery_turns reads every turn and
+//     delivery_hand_now hands a waiting merge at once on the operator's word, the check it waited for then carried.
+
+// turnBound is how long an approved merge may wait for another delivery's check before it is a stalled line (ADR 0548 §4).
+const turnBound = 30 * time.Minute
+
+// TurnStore is the gate's bucket turns: one key per repository, written by the gate alone.
+type TurnStore interface {
+	// All reads every turn, by repository (lowercase).
+	All() (map[string]sdk.Turn, error)
+	Put(t sdk.Turn) error
+	Delete(repository string) error
+}
+
+// kvTurns is the bucket turns over the runtime.
+type kvTurns struct{}
+
+func (kvTurns) All() (map[string]sdk.Turn, error) {
+	keys, err := stdio.State("turns").Keys()
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]sdk.Turn{}
+	for _, k := range keys {
+		e, err := stdio.State("turns").Get(k)
+		if err != nil {
+			return nil, err
+		}
+		if e == nil {
+			continue
+		}
+		repository, err := sdk.ParseTurnsKey(k)
+		if err != nil {
+			continue // not a turn's key: never the gate's, left
+		}
+		t, err := sdk.DecodeTurn(e.Value)
+		if err != nil {
+			t = sdk.Turn{Repository: repository} // unreadable: rewritten or deleted at the next look
+		}
+		out[repository] = t
+	}
+	return out, nil
+}
+
+func (kvTurns) Put(t sdk.Turn) error {
+	key, err := sdk.TurnsKey(t.Repository)
+	if err != nil {
+		return err
+	}
+	raw, err := sdk.EncodeTurn(t)
+	if err != nil {
+		return err
+	}
+	_, err = stdio.State("turns").Put(key, json.RawMessage(raw))
+	return err
+}
+
+func (kvTurns) Delete(repository string) error {
+	key, err := sdk.TurnsKey(repository)
+	if err != nil {
+		return err
+	}
+	return stdio.State("turns").Delete(key)
+}
+
+// approvedMerge is an approved merge not yet done: the run holding its Approve, the deliveries it covers, the hash of their
+// heads as the checker keys their verdict (lowercase, onestatus.go headsOf), and the repositories it goes into (lowercase).
+type approvedMerge struct {
+	owner *Delivery
+	run   *ReadyRun
+	group string
+	heads string
+	repos []string
+}
+
+// approvedMerges are the merges the operator approved that are not done, in the order of their Approve: each ask once, its
+// run on the delivery that asked it. A declined, refused, merged, rejected or final one has left. Under the lock.
+func (h *Holder) approvedMerges() []approvedMerge {
+	var out []approvedMerge
+	seen := map[string]bool{}
+	ids := make([]string, 0, len(h.deliveries))
+	for id := range h.deliveries {
+		ids = append(ids, id)
+	}
+	sort.Strings(ids) // the same owner of an ask at every look, whichever member's run holds it
+	for _, id := range ids {
+		d := h.deliveries[id]
+		r := d.Ready
+		if r == nil || r.Approved == nil || r.Declined != nil || r.AskID == "" || len(r.Heads) == 0 || seen[r.AskID] ||
+			d.State.Final() || d.State == Rejected || d.Base != MergeBranch || r.RefusedSince != nil || h.allMerged(r.Heads) {
+			continue
+		}
+		seen[r.AskID] = true
+		var heads []sdk.Head
+		repos := map[string]bool{}
+		for id, sha := range r.Heads {
+			m := h.deliveries[id]
+			if m == nil {
+				continue
+			}
+			heads = append(heads, sdk.Head{Repository: strings.ToLower(m.Repository), Number: m.Number, Head: strings.ToLower(sha)})
+			repos[strings.ToLower(m.Repository)] = true
+		}
+		hash, err := sdk.HeadsHash(heads)
+		if err != nil {
+			continue
+		}
+		am := approvedMerge{owner: d, run: r, group: askGroup(d), heads: hash}
+		for repo := range repos {
+			am.repos = append(am.repos, repo)
+		}
+		sort.Strings(am.repos)
+		out = append(out, am)
+	}
+	sort.SliceStable(out, func(i, j int) bool {
+		if !out[i].run.Approved.Equal(*out[j].run.Approved) {
+			return out[i].run.Approved.Before(*out[j].run.Approved)
+		}
+		return out[i].heads < out[j].heads
+	})
+	return out
+}
+
+// mergeOfDelivery is the approved merge covering d, if one is approved.
+func (h *Holder) mergeOfDelivery(d *Delivery) (approvedMerge, bool) {
+	c := h.covering(d)
+	if c == nil || c.Approved == nil {
+		return approvedMerge{}, false
+	}
+	for _, am := range h.approvedMerges() {
+		// By the ask, not the run: a group's members may each hold a run of the same ask, and the merge is the ask's.
+		if am.run.AskID == c.AskID {
+			return am, true
+		}
+	}
+	return approvedMerge{}, false
+}
+
+// runningCheck is a check of the checker in the state running that names repo among its trunk heads, its heads not own: its
+// verdict key and since when the gate has seen it run. False when none runs there. Under the lock.
+func (h *Holder) runningCheck(repo, own string) (key string, v checkerVerdict, since time.Time, ok bool) {
+	hashes := make([]string, 0, len(h.checker))
+	for hash := range h.checker {
+		hashes = append(hashes, hash)
+	}
+	sort.Strings(hashes)
+	for _, hash := range hashes {
+		v := h.checker[hash]
+		if v.State != checkerRunning || v.Heads == own {
+			continue
+		}
+		for r := range v.Trunk {
+			if strings.EqualFold(r, repo) {
+				key, err := sdk.CheckerVerdictKey(v.Group, v.Heads)
+				if err != nil {
+					key = v.Group + "." + v.Heads
+				}
+				return key, v, h.runningSince[v.Heads], true
+			}
+		}
+	}
+	return "", checkerVerdict{}, time.Time{}, false
+}
+
+// turnWaits is what an approved merge waits for before it is handed (ADR 0548 §2, §3): its turns written, then the end of
+// every check of other heads running on a repository it goes into. Empty when it may be handed. It keeps on the run since
+// when it is held and for which check, for the stalled line and the tools. Under the lock.
+func (h *Holder) turnWaits(d *Delivery, now time.Time) string {
+	am, ok := h.mergeOfDelivery(d)
+	if !ok {
+		return ""
+	}
+	r := am.run
+	if h.Turns != nil {
+		if !h.turnsLoaded {
+			return "approved; its merge turn waits for the turns the gate wrote before to be read"
+		}
+		for _, repo := range am.repos {
+			if !turnNames(h.turnsHeld[repo], am.heads) {
+				return "approved; its merge turn on " + repo + " is being written, so no check starts there before it merges"
+			}
+		}
+	}
+	if r.HandNow != "" {
+		if r.HeldSince != nil {
+			r.HeldSince, r.HeldFor = nil, ""
+			h.keep(am.owner)
+		}
+		return "" // handed now on the operator's word: the check it waited for is carried after the merge
+	}
+	for _, repo := range am.repos {
+		key, v, since, running := h.runningCheck(repo, am.heads)
+		if !running {
+			continue
+		}
+		if r.HeldSince == nil || r.HeldFor != key {
+			at := now
+			r.HeldSince, r.HeldFor = &at, key
+			h.keep(am.owner)
+			h.Logf("[mesh-delivery] %s is approved and held: the check %s runs on %s, and nothing merges there while it does (ADR 0548 §2)", am.owner.ID, key, repo)
+		}
+		words := fmt.Sprintf("approved; waits for the check of %s (heads %s) on %s", v.Group, v.Heads, repo)
+		if !since.IsZero() {
+			words += ", running since " + since.UTC().Format(time.RFC3339)
+		}
+		return words + " (novox/hq ADR 0548 §2)"
+	}
+	if r.HeldSince != nil {
+		r.HeldSince, r.HeldFor = nil, ""
+		h.keep(am.owner)
+	}
+	return ""
+}
+
+// turnNames says whether a turn names the heads.
+func turnNames(t sdk.Turn, heads string) bool {
+	for _, w := range t.Waiting {
+		if w.Heads == heads {
+			return true
+		}
+	}
+	return false
+}
+
+// wantedTurns are the turns the approved merges hold now, by repository: each merge on every repository it goes into, in
+// the order of their Approve, with the check of other heads it waits for there. Under the lock.
+func (h *Holder) wantedTurns() map[string]sdk.Turn {
+	out := map[string]sdk.Turn{}
+	for _, am := range h.approvedMerges() {
+		for _, repo := range am.repos {
+			t := out[repo]
+			t.Repository = repo
+			w := sdk.TurnWait{Group: am.group, Heads: am.heads, Ask: am.run.AskID, Approved: am.run.Approved.UTC(), Since: am.run.Approved.UTC()}
+			if key, _, since, ok := h.runningCheck(repo, am.heads); ok {
+				w.WaitsFor = key
+				if !since.IsZero() {
+					w.WaitsSince = since.UTC()
+				}
+			}
+			t.Waiting = append(t.Waiting, w)
+			out[repo] = t
+		}
+	}
+	return out
+}
+
+// turnWrites are the writes that bring the bucket turns to what the approved merges hold: a turn written where it changed,
+// a key deleted where its last delivery merged or left. The first look reads what a gate before this one wrote. Under the
+// lock; the writes run outside it, and each that lands is kept and asks for a look.
+func (h *Holder) turnWrites() []func() {
+	if h.Turns == nil {
+		return nil
+	}
+	if !h.turnsLoaded {
+		return []func(){func() {
+			held, err := h.Turns.All()
+			h.mu.Lock()
+			defer h.mu.Unlock()
+			if err != nil {
+				h.Logf("[mesh-delivery] the merge turns written before cannot be read, so no merge is handed yet: %v; asked again in %s", err, askAgainAfter)
+				h.again("the merge turns written before, read")
+				return
+			}
+			h.turnsHeld, h.turnsLoaded = held, true
+			h.Poke()
+		}}
+	}
+	want := map[string]sdk.Turn{}
+	if h.checkGates() {
+		want = h.wantedTurns() // while the check gates no merge, no merge waits for one, and no turn holds a check
+	}
+	var out []func()
+	repos := make([]string, 0, len(want)+len(h.turnsHeld))
+	for repo := range want {
+		repos = append(repos, repo)
+	}
+	for repo := range h.turnsHeld {
+		if _, ok := want[repo]; !ok {
+			repos = append(repos, repo)
+		}
+	}
+	sort.Strings(repos)
+	for _, repo := range repos {
+		t, wanted := want[repo]
+		held, had := h.turnsHeld[repo]
+		switch {
+		case wanted && had && sameTurnValue(held, t):
+		case wanted:
+			out = append(out, func() {
+				err := h.Turns.Put(t)
+				h.mu.Lock()
+				defer h.mu.Unlock()
+				if err != nil {
+					h.Logf("[mesh-delivery] the merge turn on %s cannot be written: %v; asked again in %s", repo, err, askAgainAfter)
+					h.again("a merge turn, written")
+					return
+				}
+				h.turnsHeld[repo] = t
+				h.Poke()
+			})
+		default:
+			out = append(out, func() {
+				err := h.Turns.Delete(repo)
+				h.mu.Lock()
+				defer h.mu.Unlock()
+				if err != nil {
+					h.Logf("[mesh-delivery] the merge turn on %s cannot be deleted: %v; asked again in %s", repo, err, askAgainAfter)
+					h.again("a merge turn, deleted")
+					return
+				}
+				delete(h.turnsHeld, repo)
+				h.Logf("[mesh-delivery] the merge turn on %s is deleted: no approved merge waits on it, so the checker may start a check there", repo)
+				h.Poke()
+			})
+		}
+	}
+	return out
+}
+
+// sameTurnValue says whether two turns hold the same value, the version aside.
+func sameTurnValue(a, b sdk.Turn) bool {
+	a.V, b.V = 0, 0
+	return sdk.SameTurn(a, b)
+}
+
+// turnLines are the stalled lines of approved merges held past turnBound by another delivery's check (ADR 0548 §4). Under the
+// lock.
+func (h *Holder) turnLines(now time.Time) []StalledLine {
+	var out []StalledLine
+	for _, d := range h.deliveries {
+		r := d.Ready
+		if r == nil || r.HeldSince == nil || r.Merged != nil || d.MergedAs != "" || d.State.Final() || now.Sub(*r.HeldSince) < turnBound {
+			continue
+		}
+		words := r.Waits
+		if words == "" {
+			words = "approved; waits for the check " + r.HeldFor
+		}
+		out = append(out, StalledLine{ID: d.ID, Number: d.Number, State: d.State, For: now.Sub(*r.HeldSince).Round(time.Second).String(),
+			Bound: turnBound.String(),
+			H2:    "none: the check it waits for ends, or the operator hands the merge now with delivery_hand_now — the operator's",
+			Says: fmt.Sprintf("%s#%d at %s is %s, held since %s; the step that check is at is read with the checker's checker_status",
+				d.Repository, d.Number, shortOf(r.Head, 12), words, r.HeldSince.UTC().Format(time.RFC3339))})
+	}
+	return out
+}
+
+// TurnLine is one repository's turn as delivery_turns reads it: the turn as the gate holds it and, for each delivery waiting,
+// the check it waits for in words.
+type TurnLine struct {
+	Repository string         `json:"repository"`
+	Turn       sdk.Turn       `json:"turn"`
+	Waits      map[string]any `json:"waits,omitempty"`
+}
+
+// TurnsRead is the tool delivery_turns: every turn the gate holds, with the check each waiting delivery waits for, since when,
+// and whether the merge was handed now on the operator's word.
+func (h *Holder) TurnsRead() map[string]any {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	want := h.wantedTurns()
+	repos := make([]string, 0, len(want))
+	for repo := range want {
+		repos = append(repos, repo)
+	}
+	sort.Strings(repos)
+	lines := []TurnLine{}
+	for _, repo := range repos {
+		l := TurnLine{Repository: repo, Turn: want[repo], Waits: map[string]any{}}
+		for _, w := range want[repo].Waiting {
+			says := "nothing: no check of other heads runs on " + repo
+			if w.WaitsFor != "" {
+				says = "the check " + w.WaitsFor
+				if !w.WaitsSince.IsZero() {
+					says += ", running since " + w.WaitsSince.Format(time.RFC3339)
+				}
+			}
+			l.Waits[w.Group] = says
+		}
+		lines = append(lines, l)
+	}
+	out := map[string]any{"turns": lines, "check-gates-merge": h.checkGates(), "bound": turnBound.String()}
+	if h.Turns != nil {
+		out["written"] = h.turnsLoaded
+		var unwritten []string
+		for _, repo := range repos {
+			if held, ok := h.turnsHeld[repo]; !ok || !sameTurnValue(held, want[repo]) {
+				unwritten = append(unwritten, repo)
+			}
+		}
+		for repo := range h.turnsHeld {
+			if _, ok := want[repo]; !ok {
+				unwritten = append(unwritten, repo+" (to delete)")
+			}
+		}
+		sort.Strings(unwritten)
+		if len(unwritten) > 0 {
+			out["not-yet-written"] = unwritten
+		}
+	}
+	return out
+}
+
+// HandNow is the tool delivery_hand_now (ADR 0548 §4): on the operator's word an approved merge held for another delivery's
+// check is handed at once; that check runs on and is carried to the new trunk after the merge. Refused for a delivery that is
+// not an approved merge waiting, naming why.
+func (h *Holder) HandNow(id, why string) (string, error) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	d := h.deliveries[id]
+	if d == nil {
+		return "", fmt.Errorf("no delivery %q", id)
+	}
+	if strings.TrimSpace(why) == "" {
+		return "", fmt.Errorf("say why: the hand is the operator's word, kept on the delivery")
+	}
+	am, ok := h.mergeOfDelivery(d)
+	if !ok {
+		return "", fmt.Errorf("%s is not an approved merge waiting: nothing to hand (its state is %s)", id, d.State)
+	}
+	if am.run.HeldSince == nil {
+		return "", fmt.Errorf("%s waits for no check of another delivery: %s", id, firstOf(am.run.Waits, "it is handed at its turn"))
+	}
+	am.run.HandNow = why
+	h.keep(am.owner)
+	h.mergeAgainNow(d)
+	h.Logf("[mesh-delivery] %s is handed now on the operator's word, past the check %s it waited for, which is carried after the merge: %s",
+		id, am.run.HeldFor, why)
+	return fmt.Sprintf("%s is handed to the merge at the next look; the check %s it waited for runs on and is carried to the new trunk", id, am.run.HeldFor), nil
+}

modules/mesh-delivery-gate/cmd/mesh-delivery-gate/verbs.go

@@ -26,6 +26,10 @@ type Line struct {
 
 // waitsFor is what a delivery waits for, in words.
 func (h *Holder) waitsFor(d *Delivery) string {
+	if r := d.Ready; r != nil && r.Merged == nil && strings.HasPrefix(r.Waits, "approved;") {
+		// Approved and waiting for another delivery's check, or for its own verdict's carry (ADR 0548 §2, §8, §9).
+		return r.Waits
+	}
 	switch d.State {
 	case Proposed:
 		return "its check"
@@ -218,6 +222,7 @@ func (h *Holder) Stalled() []StalledLine {
 	}
 	out = append(out, h.withChecks(h.uncheckedLines(now))...)
 	out = append(out, h.readyLines(now)...)
+	out = append(out, h.turnLines(now)...) // an approved merge held past its bound by another delivery's check (ADR 0548 §4)
 	out = append(out, h.groupLines(now)...)
 	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
 	return out

modules/mesh-delivery-gate/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-gate
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024210118-748c564cdf7c
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026111253-9c61918ac36f
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-gate/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024210118-748c564cdf7c h1:pY2YpHSSsfDPBrOEiWTNSIPn0zdnAayRmtmmyQ3hCHY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026111253-9c61918ac36f h1:9+TZpNq8Ifj1+qmbidE6l/7qkbua4yLdzRMrezNvf1A=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024210118-748c564cdf7c/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026111253-9c61918ac36f/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

modules/mesh-delivery-gate/module.json

@@ -61,14 +61,20 @@
       "name": "source",
       "history": 64
     },
-    "conditions"
+    "conditions",
+    {
+      "name": "turns",
+      "history": 5
+    }
   ],
   "reads": [
     "mesh-delivery-teller.answers",
     "mesh-delivery-checker.verdicts"
   ],
   "tools": [
-    "delivery_status"
+    "delivery_hand_now",
+    "delivery_status",
+    "delivery_turns"
   ],
   "config": {
     "refusal-stall-floor-minutes": {