mesh-issues: hand out decision and research numbers, so sessions stop taking them by reading hq (hq issue 424)

A new verb, issue-tracker.reserve {kind, for} -> {kind, number}: one counter
per sequence beside the issue counter, advanced the same way, started above
what hq's record holds, a floor setting for open branches and the
reservations kept, and raised when hq holds a higher number. A reserved
number is spent forever, kept with who, when and for what, and said as the
event reserved (hq ADR 0275 rule 8, ADR 0290 rule 5).

modules/mesh-issues/cmd/mesh-issues/bus_test.go

@@ -203,6 +203,20 @@ func (i *instance) answer(m rpc) {
 			i.evMu.Unlock()
 			return map[string]any{}, nil
 		}
+		if m.Method == "mesh/ask" {
+			// The records module, as a reservation asks it what numbers hq holds (issue 424).
+			var a struct {
+				Key  string `json:"key"`
+				Body struct {
+					Folder string `json:"folder"`
+				} `json:"body"`
+			}
+			if err := json.Unmarshal(m.Params, &a); err != nil || a.Key != "records.records_list" {
+				return nil, fmt.Errorf("the runtime answers no ask %s in this test", a.Key)
+			}
+			listing := hqToday()
+			return map[string]any{"folders": listing.folders[a.Body.Folder], "documents": listing.docs[a.Body.Folder]}, nil
+		}
 		kv := i.b.kvs[p.State]
 		if kv == nil {
 			return nil, fmt.Errorf("the state %q is not declared", p.State)
@@ -380,6 +394,87 @@ func TestFiftyOpensAtOnceFromTwoInstancesGetFiftyDistinctConsecutiveNumbers(t *t
 	}
 }
 
+// Two instances on one bus, forty decision numbers reserved at the same moment: forty numbers, each once,
+// consecutive from one above the highest decision hq holds, a reservation and an event for each (issue 424).
+func TestFortyReservationsAtOnceFromTwoInstancesGetFortyDistinctConsecutiveNumbers(t *testing.T) {
+	b := newBus(t)
+	settings := writeSettings(t, 365)
+	var events []event
+	var evMu sync.Mutex
+	instances := []*instance{b.start(t, settings, &events, &evMu), b.start(t, settings, &events, &evMu)}
+	const reserves = 40
+	numbers := make([]uint64, reserves)
+	var wg sync.WaitGroup
+	start := make(chan struct{})
+	for k := 0; k < reserves; k++ {
+		wg.Add(1)
+		go func(k int) {
+			defer wg.Done()
+			<-start
+			raw, err := instances[k%2].call("reserve", map[string]any{"kind": "decision", "for": fmt.Sprintf("record %d", k)})
+			if err != nil {
+				t.Errorf("reserve %d: %v", k, err)
+				return
+			}
+			var r struct {
+				Kind   string `json:"kind"`
+				Number uint64 `json:"number"`
+			}
+			_ = json.Unmarshal(raw, &r)
+			if r.Kind != "decision" {
+				t.Errorf("reserve %d answered %s", k, raw)
+			}
+			numbers[k] = r.Number
+		}(k)
+	}
+	close(start)
+	wg.Wait()
+	if t.Failed() {
+		return
+	}
+	sorted := append([]uint64(nil), numbers...)
+	sort.Slice(sorted, func(i, j int) bool { return sorted[i] < sorted[j] })
+	for k, n := range sorted {
+		if n != uint64(292+k) {
+			t.Fatalf("the numbers handed out are %v: not forty distinct numbers from 292 in a row", sorted)
+		}
+	}
+	t.Logf("%d writes lost to another caller and tried again, %d of them the counters' updates", b.lost.Load(), b.counterLost.Load())
+	if b.counterLost.Load() == 0 {
+		t.Fatal("no counter update was lost to another caller: the test did not make the reservations contend")
+	}
+	ctx := context.Background()
+	if e, err := b.kvs[CountersState].Get(ctx, KindDecision); err != nil || string(e.Value()) != "331" {
+		t.Fatalf("the decision counter holds %v (%v), want 331", e, err)
+	}
+	if _, err := b.kvs[CountersState].Get(ctx, IssueCounter); !errors.Is(err, jetstream.ErrKeyNotFound) {
+		t.Fatalf("a reservation touched the issue counter: %v", err)
+	}
+	for k, n := range numbers {
+		e, err := b.kvs[ReservationsState].Get(ctx, ReservationKey(KindDecision, n))
+		if err != nil {
+			t.Fatal(err)
+		}
+		var r Reservation
+		_ = json.Unmarshal(e.Value(), &r)
+		if r.Number != n || r.For != fmt.Sprintf("record %d", k) || r.By != Unproven {
+			t.Fatalf("reservation %d holds %+v, not reserve %d's", n, r, k)
+		}
+	}
+	evMu.Lock()
+	defer evMu.Unlock()
+	said := map[float64]bool{}
+	for _, ev := range events {
+		if ev.Key != EventReserved || ev.Headers["x-source"] != "mesh-issues" {
+			t.Fatalf("event %+v", ev)
+		}
+		said[ev.Body["number"].(float64)] = true
+	}
+	if len(said) != reserves {
+		t.Fatalf("%d reserved events for distinct numbers, want %d", len(said), reserves)
+	}
+}
+
 // One instance, every verb over the bus: what an agent does with an issue from opening to resolving.
 func TestAnIssueIsOpenedNotedLinkedMovedAndListedOverTheBus(t *testing.T) {
 	b := newBus(t)

modules/mesh-issues/cmd/mesh-issues/main.go

@@ -22,7 +22,7 @@ import (
 const Seat = "issue-tracker"
 
 // Verbs are the seat's verbs, as the manifest declares and claims them.
-var Verbs = []string{"open", "get", "list", "move", "note", "link", "import", "groom", "set", "tracking"}
+var Verbs = []string{"open", "get", "list", "move", "note", "link", "import", "groom", "set", "tracking", "reserve"}
 
 func logf(format string, a ...any) { fmt.Fprintf(os.Stderr, format+"\n", a...) }
 
@@ -47,6 +47,12 @@ type Settings struct {
 	// WorkerStaleAfter is how long an issue's worker stays current with nothing done on it (ADR 0283 §2), as a
 	// duration such as 24h; DefaultWorkerStaleAfter when empty.
 	WorkerStaleAfter string `json:"worker-stale-after,omitempty"`
+	// DecisionFloor and ResearchFloor are the highest decision and research numbers taken where the tracker
+	// cannot read, such as an open branch of hq on the forge (issue 424). Read once, when the sequence's
+	// counter starts: its first number is one above the highest of this floor, the numbers hq's record holds
+	// and the reservations kept. Raised by the operator before the first reserve when a branch holds more.
+	DecisionFloor uint64 `json:"decision-floor,omitempty"`
+	ResearchFloor uint64 `json:"research-floor,omitempty"`
 }
 
 func readSettings(path string) (Settings, error) {
@@ -623,5 +629,32 @@ func Tools(t *Tracker) []stdio.Tool {
 				}
 				return t.Tracking(keys)
 			}},
+		{Name: Seat + ".reserve",
+			Description: "Reserve the next decision or research number, before the record is written, and get it: never " +
+				"one another caller got, and always above every number hq already holds. The answer is the kind and the " +
+				"number, and the number as a record's name starts with it (0292 for a decision, 046 for research). " +
+				"Optionally for: what the record is about, in one line. A reserved number is spent forever, whether or " +
+				"not its record lands, and is never handed out again; who reserved it, when and for what are kept. " +
+				"Refused, taking no number: a kind that is not decision or research (an issue's number comes from " +
+				"open), a for that is not one line of plain text or carries a secret, an unknown argument, and the " +
+				"first number of a kind while what hq holds cannot be read.",
+			Input: schema([]string{"kind"}, map[string]any{
+				"kind": map[string]any{"type": "string", "enum": ReserveKinds, "description": "which number: decision or research"},
+				"for":  text("what the record is about, in one line, such as: the knowledge base holds decisions"),
+			}),
+			Run: func(m map[string]any) (any, error) {
+				a, err := readArgs("reserve", m, "kind", "for")
+				if err != nil {
+					return nil, err
+				}
+				var ask ReserveAsk
+				if ask.Kind, err = a.str("kind"); err != nil {
+					return nil, err
+				}
+				if ask.For, err = a.str("for"); err != nil {
+					return nil, err
+				}
+				return t.Reserve(ask)
+			}},
 	}
 }

modules/mesh-issues/cmd/mesh-issues/manifest_test.go

@@ -84,20 +84,23 @@ func TestItDeclaresAndHoldsTheIssueTrackerSeatOnceForTheMesh(t *testing.T) {
 		t.Fatalf("module %q, seats %+v, claims %+v", m.Module, m.Seats, m.Claims)
 	}
 	if !reflect.DeepEqual(m.Emits, []string{EventOpened, EventMoved, EventNoted, EventLinked, EventImported, EventSet,
-		EventTriaged, EventReady, EventReadyToVerify}) {
+		EventTriaged, EventReady, EventReadyToVerify, EventReserved}) {
 		t.Fatalf("emits %v", m.Emits)
 	}
-	// Three states, none expiring: issues keep a short history per key, the counter one value, the backlog's
-	// pass of the duplicate check one value (ADR 0278 §6).
+	// Four states, none expiring: issues keep a short history per key, the counters one value each, the
+	// backlog's pass of the duplicate check one value (ADR 0278 §6), each reserved number one value (issue 424).
 	d := m.stateDeclarations(t)
-	if len(d) != 3 || d[0].Name != IssuesState || d[0].History < 2 || d[0].TTLSeconds != 0 ||
+	if len(d) != 4 || d[0].Name != IssuesState || d[0].History < 2 || d[0].TTLSeconds != 0 ||
 		d[1].Name != CountersState || d[1].History > 1 || d[1].TTLSeconds != 0 ||
-		d[2].Name != GroomingState || d[2].History > 1 || d[2].TTLSeconds != 0 {
+		d[2].Name != GroomingState || d[2].History > 1 || d[2].TTLSeconds != 0 ||
+		d[3].Name != ReservationsState || d[3].History > 1 || d[3].TTLSeconds != 0 {
 		t.Fatalf("state %+v", d)
 	}
-	// The duplicate check hears the tracker's own opens and asks the agent module on its node (ADR 0278 §1, §5).
+	// The duplicate check hears the tracker's own opens and asks the agent module on its node (ADR 0278 §1, §5);
+	// a reservation reads what numbers the record holds through the records module (issue 424).
 	if !reflect.DeepEqual(m.Consumes, []string{"mesh-issues." + EventOpened, "mesh-issues." + EventMoved, "mesh-delivery.transition"}) ||
-		!reflect.DeepEqual(m.Invokes, []string{"claude-code.claude_code_judge", "seat:mesh-delivery.checks", "seat:operator-channel.notify"}) {
+		!reflect.DeepEqual(m.Invokes, []string{"claude-code.claude_code_judge", "seat:mesh-delivery.checks", "seat:operator-channel.notify",
+			"records.records_list"}) {
 		t.Fatalf("consumes %v, invokes %v", m.Consumes, m.Invokes)
 	}
 	if len(m.Build.Artifacts) != 1 || m.Build.Artifacts[0].From != "cmd/mesh-issues" ||

modules/mesh-issues/cmd/mesh-issues/memory_test.go

@@ -25,7 +25,7 @@ type memory struct {
 }
 
 func newMemory() *memory {
-	return &memory{data: map[string]map[string]Entry{IssuesState: {}, CountersState: {}, GroomingState: {}}, fail: map[string]error{}}
+	return &memory{data: map[string]map[string]Entry{IssuesState: {}, CountersState: {}, GroomingState: {}, ReservationsState: {}}, fail: map[string]error{}}
 }
 
 func (m *memory) bucket(state string) (map[string]Entry, error) {

modules/mesh-issues/cmd/mesh-issues/reserve.go

@@ -0,0 +1,300 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// The tracker hands out decision and research numbers too (novox/hq ADR 0275 rule 8, ADR 0290 rule 5, issue
+// 424): one counter per sequence in the state `counters`, beside `issue`, advanced the same way, so two
+// sessions writing a record at the same moment never take one number. A reserved number is spent forever,
+// whether or not its record ever lands; each reservation is kept in the state `reservations` and said as the
+// event `reserved`.
+
+const (
+	// ReservationsState keeps one key per reserved number, named by ReservationKey.
+	ReservationsState = "reservations"
+	// EventReserved is said for every number reserved.
+	EventReserved = "reserved"
+
+	KindDecision = "decision"
+	KindResearch = "research"
+
+	// DecisionsFolder and ResearchFolder are where hq keeps the records whose numbers a counter starts above.
+	DecisionsFolder = "02-DECISIONS"
+	ResearchFolder  = "01-RESEARCH"
+
+	// raiseAttempts is how many times a counter behind the record is read and raised again.
+	raiseAttempts = 16
+)
+
+// ReserveKinds are the sequences reserve hands numbers from; each is also its counter's key in `counters`.
+var ReserveKinds = []string{KindDecision, KindResearch}
+
+// sequence is one kind of record numbered by the tracker: where the record keeps it, how many digits its
+// number is written with, and the operator's floor for it.
+type sequence struct {
+	kind   string
+	folder string
+	digits int
+	floor  func(Settings) uint64
+}
+
+var sequences = map[string]sequence{
+	KindDecision: {KindDecision, DecisionsFolder, 4, func(s Settings) uint64 { return s.DecisionFloor }},
+	KindResearch: {KindResearch, ResearchFolder, 3, func(s Settings) uint64 { return s.ResearchFloor }},
+}
+
+// recordNumber is a record's name that starts with its number: 0291-some-words.md, 045-some-words.
+var recordNumber = regexp.MustCompile(`^([0-9]{1,9})-`)
+
+// ReservationKey is a reservation's key: the kind and the number as the record writes it, such as
+// decision-0292 or research-046.
+func ReservationKey(kind string, n uint64) string {
+	return kind + "-" + prefixOf(kind, n)
+}
+
+func prefixOf(kind string, n uint64) string {
+	return fmt.Sprintf("%0*d", sequences[kind].digits, n)
+}
+
+// ReserveAsk is what a reserve carries.
+type ReserveAsk struct {
+	Kind string
+	For  string
+}
+
+// Reservation is one reserved number as it is kept.
+type Reservation struct {
+	Kind   string    `json:"kind"`
+	Number uint64    `json:"number"`
+	For    string    `json:"for,omitempty"`
+	By     string    `json:"by"`
+	At     time.Time `json:"at"`
+	// ID is the call's own id, so a write whose answer was lost is known as its own.
+	ID string `json:"id"`
+}
+
+// Reserved is the answer to a reserve: kind and number are the contract; the rest says what was kept.
+type Reserved struct {
+	Kind   string `json:"kind"`
+	Number uint64 `json:"number"`
+	// Prefix is the number as the record's name starts with it, such as 0292.
+	Prefix    string    `json:"prefix"`
+	For       string    `json:"for,omitempty"`
+	By        string    `json:"by"`
+	At        time.Time `json:"at"`
+	Said      string    `json:"said"`
+	Announced bool      `json:"announced"`
+	Warning   string    `json:"warning,omitempty"`
+}
+
+// Reserve hands out the next number of a sequence and keeps who reserved it, when and for what. A refused
+// reserve spends no number; a number handed out is spent forever.
+func (t *Tracker) Reserve(a ReserveAsk) (*Reserved, error) {
+	kind := a.Kind
+	seq, ok := sequences[kind]
+	if !ok {
+		return nil, fmt.Errorf("kind %q is not a kind of number the tracker hands out: one of %s (an issue's number "+
+			"comes from open). No number was taken", a.Kind, strings.Join(ReserveKinds, ", "))
+	}
+	purpose := ""
+	if strings.TrimSpace(a.For) != "" {
+		var err error
+		if purpose, err = singleLine("for", a.For, MostTitle); err != nil {
+			return nil, fmt.Errorf("%v. No number was taken", err)
+		}
+	}
+	records := t.Records
+	if records == nil {
+		records = busRecords{}
+	}
+	highest, rerr := highestIn(records, seq)
+	n, err := t.nextOf(seq, highest, rerr)
+	if err != nil {
+		return nil, err
+	}
+	r := Reservation{Kind: kind, Number: n, For: purpose, By: t.by(), At: t.now(), ID: newID()}
+	if err := t.keep(&r); err != nil {
+		return nil, err
+	}
+	out := &Reserved{Kind: kind, Number: n, Prefix: prefixOf(kind, n), For: purpose, By: r.By, At: r.At,
+		Said: fmt.Sprintf("Reserved %s number %s; it is spent, whether or not its record lands.", kind, prefixOf(kind, n))}
+	body := map[string]any{"kind": kind, "number": n, "prefix": out.Prefix, "by": r.By, "at": r.At}
+	if purpose != "" {
+		body["for"] = purpose
+	}
+	if err := t.Emit(EventReserved, body); err != nil {
+		t.Logf("[mesh-issues] %s %s was reserved and its reserved event could not be said: %v", kind, out.Prefix, err)
+		out.Warning = fmt.Sprintf("the reservation is kept, and its reserved event could not be said on the bus (%v): "+
+			"what watches the events did not hear of it", err)
+	} else {
+		out.Announced = true
+	}
+	return out, nil
+}
+
+// highestIn is the highest number the record holds in a sequence's folder, sub-folders and documents alike.
+func highestIn(records Records, seq sequence) (uint64, error) {
+	folders, docs, err := records.List(seq.folder)
+	if err != nil {
+		return 0, err
+	}
+	var highest uint64
+	for _, name := range append(folders, docs...) {
+		if m := recordNumber.FindStringSubmatch(name); m != nil {
+			if n, err := strconv.ParseUint(m[1], 10, 64); err == nil && n > highest {
+				highest = n
+			}
+		}
+	}
+	return highest, nil
+}
+
+// nextOf takes a sequence's next number. A counter not yet started is started once, above the highest the
+// record holds, the operator's floor and every reservation kept; it is never started without the record
+// read. A started counter behind the record (a number taken by hand) is raised to it first; a record that
+// cannot be read then leaves the counter as it is.
+func (t *Tracker) nextOf(seq sequence, highest uint64, recordErr error) (uint64, error) {
+	e, err := t.Store.Get(CountersState, seq.kind)
+	if err != nil {
+		return 0, fmt.Errorf("the %s counter cannot be read (%v); no number was taken", seq.kind, err)
+	}
+	if e == nil {
+		if recordErr != nil {
+			return 0, fmt.Errorf("the %s counter has not started, and what numbers hq's %s holds cannot be read through "+
+				"the records module (%v): it starts above them, so no number was taken. Ask again when the records "+
+				"module answers", seq.kind, seq.folder, recordErr)
+		}
+		if err := t.startSequence(seq, highest); err != nil {
+			return 0, err
+		}
+	} else if recordErr != nil {
+		t.Logf("[mesh-issues] the record's %s could not be read (%v); the %s counter is used as it stands", seq.folder, recordErr, seq.kind)
+	} else if err := t.raise(seq.kind, highest); err != nil {
+		return 0, err
+	}
+	for round := 0; round < counterRounds; round++ {
+		n, err := t.Store.Increment(CountersState, seq.kind, counterAttempts)
+		if err == nil {
+			return n, nil
+		}
+		if !errors.Is(err, stdio.ErrChanged) {
+			t.Logf("[mesh-issues] the %s counter could not be advanced: %v", seq.kind, err)
+			return 0, fmt.Errorf("the %s counter could not be advanced (%v); nothing was reserved. If the bus took the "+
+				"write before it failed, one number stays unused", seq.kind, err)
+		}
+		t.Sleep(jitter(time.Duration(round+1) * 10 * time.Millisecond))
+	}
+	return 0, fmt.Errorf("so many %s numbers are being reserved at this moment that the counter was taken by another "+
+		"caller %d times; no number was taken. Reserve again", seq.kind, counterRounds*counterAttempts)
+}
+
+// startSequence makes a sequence's counter, only when there is none, at the highest of the record, the
+// floor and the reservations kept: the first number handed out is one above all three.
+func (t *Tracker) startSequence(seq sequence, highest uint64) error {
+	s, err := t.Settings()
+	if err != nil {
+		return fmt.Errorf("the %s counter has not started and the settings cannot be read (%v); no number was taken", seq.kind, err)
+	}
+	start := max(highest, seq.floor(s))
+	keys, err := t.Store.Keys(ReservationsState)
+	if err != nil {
+		return fmt.Errorf("the %s counter has not started and the reservations kept cannot be listed (%v); no number "+
+			"was taken", seq.kind, err)
+	}
+	for _, k := range keys {
+		if rest, ok := strings.CutPrefix(k, seq.kind+"-"); ok {
+			if n, err := strconv.ParseUint(rest, 10, 64); err == nil && n > start {
+				start = n
+			}
+		}
+	}
+	if _, err := t.Store.Create(CountersState, seq.kind, start); err != nil && !errors.Is(err, stdio.ErrChanged) {
+		return fmt.Errorf("the %s counter could not be started (%v); no number was taken", seq.kind, err)
+	}
+	// ErrChanged: another caller started it first; the raise on the next reserve covers any difference.
+	return nil
+}
+
+// raise sets a counter to the highest number the record holds when it stands below it, written only at the
+// revision read: it only ever goes up.
+func (t *Tracker) raise(key string, highest uint64) error {
+	for i := 0; i < raiseAttempts; i++ {
+		e, err := t.Store.Get(CountersState, key)
+		if err != nil {
+			return fmt.Errorf("the %s counter cannot be read (%v); no number was taken", key, err)
+		}
+		var n uint64
+		if e != nil {
+			if err := json.Unmarshal(e.Value, &n); err != nil {
+				return fmt.Errorf("the %s counter holds %s, not a number; no number was taken", key, e.Value)
+			}
+		}
+		if e == nil || n >= highest {
+			return nil
+		}
+		_, err = t.Store.Update(CountersState, key, highest, e.Revision)
+		if err == nil {
+			t.Logf("[mesh-issues] the %s counter stood at %d below %d in the record; raised to it", key, n, highest)
+			return nil
+		}
+		if !errors.Is(err, stdio.ErrChanged) {
+			return fmt.Errorf("the %s counter stands below the record's %d and could not be raised (%v); no number was "+
+				"taken", key, highest, err)
+		}
+		t.Sleep(jitter(time.Duration(i+1) * 5 * time.Millisecond))
+	}
+	return fmt.Errorf("the %s counter was changed by other callers %d times while it was raised to the record's %d; "+
+		"no number was taken. Reserve again", key, raiseAttempts, highest)
+}
+
+// keep writes a reservation under its key, never over one. A write that cannot be confirmed is refused, and
+// the number stays spent: it is never handed out again.
+func (t *Tracker) keep(r *Reservation) error {
+	key := ReservationKey(r.Kind, r.Number)
+	var err error
+	for i := 0; i < createAttempts; i++ {
+		if i > 0 {
+			t.Sleep(jitter(time.Duration(i) * 50 * time.Millisecond))
+		}
+		_, err = t.Store.Create(ReservationsState, key, r)
+		if err == nil {
+			return nil
+		}
+		if errors.Is(err, stdio.ErrChanged) {
+			if mine, rerr := t.isKept(key, r.ID); rerr == nil && mine {
+				return nil
+			}
+			t.Logf("[mesh-issues] the %s counter handed out %d and a reservation %s is already kept: not overwritten", r.Kind, r.Number, key)
+			return fmt.Errorf("a fault, not your mistake: the %s counter handed out %d, and %s is already reserved. "+
+				"Nothing was overwritten; %d stays spent. Reserve again for the next number, and tell the operator "+
+				"the counter is behind the reservations kept", r.Kind, r.Number, key, r.Number)
+		}
+	}
+	if mine, rerr := t.isKept(key, r.ID); rerr == nil && mine {
+		return nil
+	}
+	t.Logf("[mesh-issues] %s was taken and its reservation's write was not confirmed: %v", key, err)
+	return fmt.Errorf("%s number %d was taken and its reservation could not be kept (%v): the number is spent and "+
+		"is not yours to use. Reserve again for the next one", r.Kind, r.Number, err)
+}
+
+func (t *Tracker) isKept(key, id string) (bool, error) {
+	e, err := t.Store.Get(ReservationsState, key)
+	if err != nil || e == nil {
+		return false, err
+	}
+	var there Reservation
+	if err := json.Unmarshal(e.Value, &there); err != nil {
+		return false, err
+	}
+	return there.ID == id, nil
+}

modules/mesh-issues/cmd/mesh-issues/reserve_test.go

@@ -0,0 +1,342 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"sort"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// The tracker hands out decision and research numbers too (novox/hq ADR 0275 rule 8, ADR 0290 rule 5, issue
+// 424): one counter per sequence, advanced like the issue counter, started above every number the record
+// holds and the operator's floor, and a reserved number is spent forever.
+
+// listedRecords is the record as a folder listing: what records_list answers per folder, or an error.
+type listedRecords struct {
+	mu      sync.Mutex
+	folders map[string][]string
+	docs    map[string][]string
+	err     error
+	lists   int
+}
+
+func (l *listedRecords) Standing() (string, error)           { return "1ea678c", nil }
+func (l *listedRecords) Read(string) (string, string, error) { return "", "", errors.New("not read") }
+func (l *listedRecords) List(folder string) ([]string, []string, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.lists++
+	if l.err != nil {
+		return nil, nil, l.err
+	}
+	return l.folders[folder], l.docs[folder], nil
+}
+
+// hqToday is hq as the records module holds it: decisions as documents, research as folders.
+func hqToday() *listedRecords {
+	return &listedRecords{
+		docs: map[string][]string{DecisionsFolder: {"README.md", "0001-the-first.md", "0290-no-copy-in-hq.md",
+			"0291-an-issue-lives-whole-in-the-issue-tracker.md"}},
+		folders: map[string][]string{ResearchFolder: {"001-the-first", "044-what-leaves-the-controller-next",
+			"045-a-knowledge-base-the-mesh-writes", "_template"}},
+	}
+}
+
+func reserveHarness(t *testing.T) (*harness, *listedRecords) {
+	t.Helper()
+	h := newHarness(t)
+	r := hqToday()
+	h.Records = r
+	return h, r
+}
+
+func (h *harness) reserve(t *testing.T, kind string) uint64 {
+	t.Helper()
+	out, err := h.Reserve(ReserveAsk{Kind: kind})
+	if err != nil {
+		t.Fatalf("reserve %s: %v", kind, err)
+	}
+	return out.Number
+}
+
+func (m *memory) counterOf(t *testing.T, key string) uint64 {
+	t.Helper()
+	e, _ := m.Get(CountersState, key)
+	if e == nil {
+		return 0
+	}
+	var n uint64
+	if err := json.Unmarshal(e.Value, &n); err != nil {
+		t.Fatalf("the counter %s holds %s", key, e.Value)
+	}
+	return n
+}
+
+func TestTheFirstReservedNumberIsAboveTheHighestTheRecordHolds(t *testing.T) {
+	h, _ := reserveHarness(t)
+	if got := h.reserve(t, KindDecision); got != 292 {
+		t.Fatalf("the first decision number is %d, want 292: one above 0291", got)
+	}
+	if got := h.reserve(t, KindResearch); got != 46 {
+		t.Fatalf("the first research number is %d, want 46: one above 045", got)
+	}
+	if got := h.reserve(t, KindDecision); got != 293 {
+		t.Fatalf("the second decision number is %d, want 293", got)
+	}
+	if h.mem.counter(t) != 0 {
+		t.Fatal("a reservation moved the issue counter")
+	}
+}
+
+// An open branch the tracker cannot read holds a higher number: the operator's floor says it.
+func TestTheCounterStartsAboveTheFloorWhenItIsHigher(t *testing.T) {
+	h, _ := reserveHarness(t)
+	h.settings.DecisionFloor = 293
+	h.settings.ResearchFloor = 40 // below what the record holds: the record wins
+	if got := h.reserve(t, KindDecision); got != 294 {
+		t.Fatalf("got %d, want 294: one above the floor 293", got)
+	}
+	if got := h.reserve(t, KindResearch); got != 46 {
+		t.Fatalf("got %d, want 46: the floor 40 is below 045", got)
+	}
+}
+
+func TestTheCounterNeverStartsBelowAReservationAlreadyKept(t *testing.T) {
+	h, _ := reserveHarness(t)
+	h.mem.put(ReservationsState, ReservationKey(KindDecision, 310), Reservation{Kind: KindDecision, Number: 310})
+	if got := h.reserve(t, KindDecision); got != 311 {
+		t.Fatalf("got %d, want 311: the counter started below a reservation kept", got)
+	}
+}
+
+// A number the record holds above the counter — taken by hand while sessions still did — raises it: no
+// number at or below one that exists is handed out.
+func TestARecordAboveTheCounterRaisesIt(t *testing.T) {
+	h, r := reserveHarness(t)
+	h.reserve(t, KindDecision) // 292, the counter started
+	r.mu.Lock()
+	r.docs[DecisionsFolder] = append(r.docs[DecisionsFolder], "0300-taken-by-hand.md")
+	r.mu.Unlock()
+	if got := h.reserve(t, KindDecision); got != 301 {
+		t.Fatalf("got %d, want 301: one above 0300", got)
+	}
+}
+
+func TestTheCounterStartsOnlyOnceAndTheFloorIsThenNotRead(t *testing.T) {
+	h, _ := reserveHarness(t)
+	h.reserve(t, KindDecision) // 292
+	h.settings.DecisionFloor = 1
+	if got := h.reserve(t, KindDecision); got != 293 {
+		t.Fatalf("got %d, want 293", got)
+	}
+}
+
+func TestManyConcurrentReservationsGetDistinctConsecutiveNumbers(t *testing.T) {
+	h, _ := reserveHarness(t)
+	const each = 40
+	var mu sync.Mutex
+	got := map[string][]uint64{}
+	var wg sync.WaitGroup
+	for i := 0; i < 2*each; i++ {
+		kind := KindDecision
+		if i%2 == 1 {
+			kind = KindResearch
+		}
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			out, err := h.Reserve(ReserveAsk{Kind: kind, For: "concurrent"})
+			if err != nil {
+				t.Errorf("reserve %s: %v", kind, err)
+				return
+			}
+			mu.Lock()
+			got[kind] = append(got[kind], out.Number)
+			mu.Unlock()
+		}()
+	}
+	wg.Wait()
+	for kind, first := range map[string]uint64{KindDecision: 292, KindResearch: 46} {
+		ns := got[kind]
+		sort.Slice(ns, func(i, j int) bool { return ns[i] < ns[j] })
+		if len(ns) != each {
+			t.Fatalf("%s: %d numbers, want %d", kind, len(ns), each)
+		}
+		for i, n := range ns {
+			if n != first+uint64(i) {
+				t.Fatalf("%s: numbers %v are not %d.. distinct and consecutive", kind, ns, first)
+			}
+			if _, err := h.mem.Get(ReservationsState, ReservationKey(kind, n)); err != nil {
+				t.Fatal(err)
+			}
+		}
+		if c := h.mem.counterOf(t, kind); c != first+each-1 {
+			t.Fatalf("%s counter at %d, want %d", kind, c, first+each-1)
+		}
+	}
+	if keys, _ := h.mem.Keys(ReservationsState); len(keys) != 2*each {
+		t.Fatalf("%d reservations kept, want %d", len(keys), 2*each)
+	}
+}
+
+func TestARefusedReservationSpendsNothing(t *testing.T) {
+	h, r := reserveHarness(t)
+	refused := []ReserveAsk{
+		{Kind: ""},
+		{Kind: "issue"},
+		{Kind: "Decision"},
+		{Kind: "design"},
+		{Kind: KindDecision, For: "two\nlines"},
+		{Kind: KindDecision, For: strings.Repeat("x", MostTitle+1)},
+		{Kind: KindResearch, For: "the key is sk-ant-api03-abcdefghijklmnopqrstuvwxyz"},
+		{Kind: KindResearch, For: "t\x1b[31m"},
+	}
+	for i, a := range refused {
+		if out, err := h.Reserve(a); err == nil {
+			t.Errorf("case %d (%+v) was reserved: %+v", i, a, out)
+		}
+	}
+	keys, _ := h.mem.Keys(CountersState)
+	kept, _ := h.mem.Keys(ReservationsState)
+	if len(keys) != 0 || len(kept) != 0 || len(h.said()) != 0 || r.lists != 0 {
+		t.Fatalf("a refused reservation left counters %v, reservations %v, events %v, record reads %d", keys, kept, h.said(), r.lists)
+	}
+	if got := h.reserve(t, KindDecision); got != 292 {
+		t.Fatalf("the first valid reservation got %d, want 292", got)
+	}
+}
+
+// Before its counter starts, a sequence must know what the record holds: unreadable, nothing is handed out.
+// Once started, the counter alone is enough.
+func TestAnUnreadableRecordRefusesTheFirstNumberAndNotTheNext(t *testing.T) {
+	h, r := reserveHarness(t)
+	r.err = errors.New("records did not answer")
+	if _, err := h.Reserve(ReserveAsk{Kind: KindDecision}); err == nil || !strings.Contains(err.Error(), "records did not answer") {
+		t.Fatalf("a first reservation with the record unreadable: %v", err)
+	}
+	if h.mem.counterOf(t, KindDecision) != 0 || len(h.said()) != 0 {
+		t.Fatal("a refused first reservation started the counter or said something")
+	}
+	r.err = nil
+	h.reserve(t, KindDecision) // 292
+	r.err = errors.New("records did not answer")
+	if got := h.reserve(t, KindDecision); got != 293 {
+		t.Fatalf("got %d, want 293 from the started counter", got)
+	}
+}
+
+func TestAReservationIsKeptWithWhoWhenAndWhatFor(t *testing.T) {
+	h, _ := reserveHarness(t)
+	out, err := h.Reserve(ReserveAsk{Kind: KindDecision, For: "  the knowledge base holds decisions  "})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.Kind != KindDecision || out.Number != 292 || out.Prefix != "0292" || out.By != Unproven ||
+		out.For != "the knowledge base holds decisions" || !out.Announced {
+		t.Fatalf("answered %+v", out)
+	}
+	e, err := h.mem.Get(ReservationsState, "decision-0292")
+	if err != nil || e == nil {
+		t.Fatalf("the reservation is not kept: %v", err)
+	}
+	var kept Reservation
+	if err := json.Unmarshal(e.Value, &kept); err != nil {
+		t.Fatal(err)
+	}
+	if kept.Kind != KindDecision || kept.Number != 292 || kept.By != Unproven || kept.At.IsZero() ||
+		kept.For != "the knowledge base holds decisions" {
+		t.Fatalf("kept %+v", kept)
+	}
+	ev := h.said()
+	if len(ev) != 1 || ev[0].Event != EventReserved || ev[0].Body["kind"] != KindDecision ||
+		ev[0].Body["number"] != float64(292) || ev[0].Body["by"] != Unproven || ev[0].Body["for"] != kept.For {
+		t.Fatalf("said %+v", ev)
+	}
+	r, err := h.Reserve(ReserveAsk{Kind: KindResearch})
+	if err != nil || r.Prefix != "046" {
+		t.Fatalf("a research number's prefix: %+v, %v", r, err)
+	}
+}
+
+func TestAReservationWhoseEventCannotBeSaidIsKeptAndSaysSo(t *testing.T) {
+	h, _ := reserveHarness(t)
+	h.emitErr = errors.New("the bus is away")
+	out, err := h.Reserve(ReserveAsk{Kind: KindResearch})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.Announced || out.Warning == "" || out.Number != 46 {
+		t.Fatalf("answered %+v", out)
+	}
+}
+
+// A reservation whose write cannot be confirmed is refused, and the number stays spent.
+func TestANumberWhoseReservationIsNotKeptIsSaidAndNeverHandedOutAgain(t *testing.T) {
+	h, _ := reserveHarness(t)
+	h.mem.fail[ReservationsState] = errors.New("the bus did not answer")
+	if got := h.reserve(t, KindDecision); got != 292 {
+		t.Fatalf("one failure is tried again: got %d", got)
+	}
+	failing := &failingReservations{memory: h.mem, fail: 1000}
+	h.Store = failing
+	_, err := h.Reserve(ReserveAsk{Kind: KindDecision})
+	if err == nil || !strings.Contains(err.Error(), "293") || !strings.Contains(err.Error(), "spent") {
+		t.Fatalf("a reservation never kept: %v", err)
+	}
+	h.Store = h.mem
+	if got := h.reserve(t, KindDecision); got != 294 {
+		t.Fatalf("got %d, want 294: a number is never handed out twice", got)
+	}
+}
+
+type failingReservations struct {
+	*memory
+	fail int
+}
+
+func (f *failingReservations) Create(state, key string, value any) (uint64, error) {
+	if state == ReservationsState && f.fail > 0 {
+		f.fail--
+		return 0, errors.New("the bus did not answer")
+	}
+	return f.memory.Create(state, key, value)
+}
+
+func TestTheReserveVerbReadsItsArgumentsStrictlyAndAnswersTheContract(t *testing.T) {
+	h, _ := reserveHarness(t)
+	for _, args := range []map[string]any{
+		{},
+		{"kind": 5},
+		{"kind": KindDecision, "for": 7},
+		{"kind": KindDecision, "by": "operator"},
+		{"kind": KindDecision, "number": 400},
+	} {
+		if out, err := h.call(t, "reserve", args); err == nil {
+			t.Errorf("reserve %v was taken: %+v", args, out)
+		}
+	}
+	out, err := h.call(t, "reserve", map[string]any{"kind": "research", "for": "a spike"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, _ := json.Marshal(out)
+	var answer map[string]any
+	_ = json.Unmarshal(raw, &answer)
+	if answer["kind"] != "research" || answer["number"] != float64(46) || strings.Contains(string(raw), "operator") {
+		t.Fatalf("answered %s", raw)
+	}
+}
+
+func TestAReservationKeyNamesTheKindAndTheRecordsPrefix(t *testing.T) {
+	for _, c := range []struct {
+		kind string
+		n    uint64
+		want string
+	}{{KindDecision, 292, "decision-0292"}, {KindResearch, 46, "research-046"}, {KindDecision, 10000, "decision-10000"}} {
+		if got := ReservationKey(c.kind, c.n); got != c.want {
+			t.Errorf("%s %d: %s, want %s", c.kind, c.n, got, c.want)
+		}
+	}
+}