A decision links the milestone that builds it: link kind built-in (milestone 47/G, W15.2)

ADR 0493 section 4 names the links; the knowledge base took no milestone as a target.

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

(Joined from 5f4e4d29.)
Builds: design 47 G §318 (KB1)

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

modules/mesh-knowledge/cmd/mesh-knowledge/record.go

@@ -75,10 +75,12 @@ const (
 	LinkCites      = "cites"
 	LinkRestsOn    = "rests-on"
 	LinkTouches    = "touches"
+	// LinkBuiltIn is from a decision the milestone that builds it, design/id such as 47/G (ADR 0493 §4, design 47).
+	LinkBuiltIn = "built-in"
 )
 
 // LinkKinds are the kinds a link may be.
-var LinkKinds = []string{LinkSupersedes, LinkChanges, LinkExtends, LinkBecame, LinkCites, LinkRestsOn, LinkTouches}
+var LinkKinds = []string{LinkSupersedes, LinkChanges, LinkExtends, LinkBecame, LinkCites, LinkRestsOn, LinkTouches, LinkBuiltIn}
 
 // LinkMeanings says what each kind of link means, as the knowledge base's own review is told (hq issue 492): the
 // rules it sees list LinkKinds, which propose holds a link to, so the two cannot drift.
@@ -90,12 +92,15 @@ var LinkMeanings = map[string]string{
 	LinkCites:      "any record, issue or design it names",
 	LinkRestsOn:    "from a decision, a decision it stands on, which may not be superseded under it",
 	LinkTouches:    "from a research effort, a record, issue or design its effort bears on",
+	LinkBuiltIn:    "from a decision, the milestone that builds it, named as milestone 47/G",
 }
 
 // What a link may point at besides a record of this knowledge base: an issue in the tracker, a design in hq.
 const (
 	TargetIssue  = "issue"
 	TargetDesign = "design"
+	// TargetMilestone is a milestone of the issue tracker, design/id; its Path holds that.
+	TargetMilestone = "milestone"
 )
 
 // Key is a record's key: its kind and number together.
@@ -166,6 +171,8 @@ func (r Ref) String() string {
 		return fmt.Sprintf("issue %d", r.Number)
 	case TargetDesign:
 		return "design " + r.Path
+	case TargetMilestone:
+		return "milestone " + r.Path
 	}
 	return r.Kind
 }
@@ -174,6 +181,8 @@ var (
 	refRecord = regexp.MustCompile(`^(?i)(?:(adr|decision|research)\s*)?(\d{1,4})(?:\s*§\s*(\d{1,3}))?$`)
 	refIssue  = regexp.MustCompile(`^(?i)issue\s*(\d{1,5})$`)
 	refDesign = regexp.MustCompile(`^(?i)(?:design\s+)?(03-DESIGN/[0-9a-z/-]+\.md)$`)
+	// refMilestone is the tracker's name for a milestone: design/id, such as 47/G.
+	refMilestone = regexp.MustCompile(`^(?i)milestone\s+([0-9]{1,3}/[A-Za-z0-9][A-Za-z0-9_-]{0,31})$`)
 )
 
 // ParseRef reads a link's target as an agent writes it: "0276", "ADR 0276 §4", "research 045", "issue 365",
@@ -187,6 +196,9 @@ func ParseRef(s string) (Ref, error) {
 	if m := refDesign.FindStringSubmatch(s); m != nil {
 		return Ref{Kind: TargetDesign, Path: m[1]}, nil
 	}
+	if m := refMilestone.FindStringSubmatch(s); m != nil {
+		return Ref{Kind: TargetMilestone, Path: m[1]}, nil
+	}
 	if m := refRecord.FindStringSubmatch(s); m != nil {
 		kind := KindDecision
 		if strings.EqualFold(m[1], "research") {
@@ -202,8 +214,8 @@ func ParseRef(s string) (Ref, error) {
 		}
 		return Ref{Kind: kind, Number: n, Clause: c}, nil
 	}
-	return Ref{}, fmt.Errorf("%q is not a record (0276, ADR 0276 §4, research 045), an issue (issue 365) or a design "+
-		"(03-DESIGN/01-to-be/55-the-knowledge-base.md)", s)
+	return Ref{}, fmt.Errorf("%q is not a record (0276, ADR 0276 §4, research 045), an issue (issue 365), a design "+
+		"(03-DESIGN/01-to-be/55-the-knowledge-base.md) or a milestone (milestone 47/G)", s)
 }
 
 // Link is one typed link, held on the record it goes out from and read from both ends. From is the clause it

modules/mesh-knowledge/cmd/mesh-knowledge/rules.go

@@ -248,6 +248,10 @@ func JudgeRecordOn(r *Record, held *Entry, lookup Lookup, ref *Reference, day st
 			if !decision || l.To.Kind != KindDecision || l.To.Clause > 0 {
 				refuse("link-fits", "rests-on goes from a decision to a decision it stands on: not %s", l)
 			}
+		case l.Kind == LinkBuiltIn:
+			if !decision || l.To.Kind != TargetMilestone {
+				refuse("link-fits", "built-in goes from a decision to the milestone that builds it, named as milestone 47/G: not %s", l)
+			}
 		case l.Kind == LinkTouches:
 			if r.Kind != KindResearch || l.To.Clause > 0 {
 				refuse("link-fits", "touches goes from a research effort to a record, an issue or a design: not %s", l)

modules/mesh-knowledge/cmd/mesh-knowledge/rules_test.go

@@ -54,6 +54,9 @@ func TestEveryPerRecordRuleRefusesAProposal(t *testing.T) {
 		{"link-fits", func(p *ProposeAsk, w *world, t *testing.T) {
 			p.Links = append(p.Links, LinkAsk{Kind: LinkBecame, To: "0276"})
 		}},
+		{"link-fits", func(p *ProposeAsk, w *world, t *testing.T) {
+			p.Links = append(p.Links, LinkAsk{Kind: LinkBuiltIn, To: "0276"}) // built-in names a milestone, not a record
+		}},
 		{"self-link", func(p *ProposeAsk, w *world, t *testing.T) {
 			p.Links = append(p.Links, LinkAsk{Kind: LinkCites, To: itoa4(p.Number)})
 		}},
@@ -165,11 +168,16 @@ func TestTheValidProposalIsTaken(t *testing.T) {
 	eachStore(t, func(t *testing.T, s Store) {
 		w := imported(t, s)
 		n := w.reserved(t, "author@test")
-		got, err := w.k.Propose("author@test", valid(n))
+		p := valid(n)
+		p.Links = append(p.Links, LinkAsk{Kind: LinkBuiltIn, To: "milestone 47/G"}) // a decision links its milestone
+		got, err := w.k.Propose("author@test", p)
 		if err != nil {
 			t.Fatal(err)
 		}
 		e := mustGet(t, s, Key{KindDecision, n})
+		if l := e.Current.Links[len(e.Current.Links)-1]; l.Kind != LinkBuiltIn || l.To != (Ref{Kind: TargetMilestone, Path: "47/G"}) {
+			t.Fatalf("the milestone link was kept as %+v", l)
+		}
 		if got.Status != StatusProposed || e.Current.Status != StatusProposed || len(e.Current.Clauses) != 2 ||
 			e.Current.Clauses[0].Status != ClauseProposed || e.Current.Author != "author@test" {
 			t.Fatalf("%+v / %+v", got, e.Current)