Carry a channel's capabilities on its claim and tell the router every kind, so an answer is judged by the controller's record and not the channel's word

internal/catalogue/kinded_test.go

@@ -93,3 +93,24 @@ func TestEachKindIsItsOwnHolderWhenResolved(t *testing.T) {
 		t.Fatal("one kind held on two machines was not refused")
 	}
 }
+
+// A channel's capabilities come from the fixed vocabulary, and only a kinded claim carries any.
+func TestCapabilitiesAreTheVocabularysAndOnlyOnAKindedClaim(t *testing.T) {
+	good := aChannel("telegram", "telegram")
+	good.Claims[0].Capabilities = []string{"deliver", "choice", "verified-sender", "max-length:4096"}
+	if got := problemsFor(t, Shelf{"messenger": router(), "telegram": good}); got != "" {
+		t.Fatalf("the vocabulary was refused: %s", got)
+	}
+	bad := aChannel("telegram", "telegram")
+	bad.Claims[0].Capabilities = []string{"trusted", "max-length:lots"}
+	got := problemsFor(t, Shelf{"messenger": router(), "telegram": bad})
+	for _, w := range []string{`"trusted"`, `"max-length:lots"`} {
+		if !strings.Contains(got, w+", which channel-capabilities/1 does not have") {
+			t.Errorf("%s was not refused: %s", w, got)
+		}
+	}
+	odd := Manifest{Module: "odd", Claims: []Claim{{Name: "operator-channel", Scope: ScopeMesh, Capabilities: []string{"deliver"}}}}
+	if got := problemsFor(t, Shelf{"messenger": router(), "odd": odd}); !strings.Contains(got, "only a kinded bench's claim carries them") {
+		t.Errorf("capabilities on a seat that is not kinded stood: %s", got)
+	}
+}

internal/catalogue/manifest.go

@@ -67,6 +67,10 @@ type Claim struct {
 	// Kind is the kind this module holds a kinded bench as (novox/hq ADR 0234 §2, ADR 0259): `telegram`,
 	// `desktop`. Refused on any other seat, and a second claim of one kind is refused.
 	Kind string `json:"kind,omitempty"`
+	// Capabilities are what a channel of this kind promises, from the fixed vocabulary
+	// channel-capabilities/1 (novox/hq ADR 0234 §2): the router judges an answer by these, read from the
+	// controller's record of this claim and never from the channel.
+	Capabilities []string `json:"capabilities,omitempty"`
 }
 
 // ServesFor is what this claim offers a seat's protocol: the verbs it names, else the module's

internal/catalogue/seats_declared.go

@@ -2,6 +2,7 @@ package catalogue
 
 import (
 	"fmt"
+	"regexp"
 	"sort"
 	"strings"
 )
@@ -331,9 +332,43 @@ func CatalogueProblems(shelf Shelf) []string {
 	return problems
 }
 
+// ChannelCapabilities is the fixed vocabulary `channel-capabilities/1` (novox/hq ADR 0234 §2): a word
+// outside it is refused. `max-length:<N>` takes a number.
+var ChannelCapabilities = map[string]bool{
+	"deliver": true, "reaches-away": true, "loud": true, "silent": true, "edit": true,
+	"reaches-when-mesh-down": true, "private": true,
+	"choice": true, "reply": true, "threads": true, "operator-first": true,
+	"verified-sender": true, "exact-render": true, "code-factor": true, "key-factor": true,
+}
+
+var maxLength = regexp.MustCompile(`^max-length:[1-9][0-9]{0,6}$`)
+
+// capabilityProblems are the words of a claim outside the vocabulary, and capabilities on a claim of a
+// seat that is not kinded.
+func capabilityProblems(module string, c Claim, kinded bool) []string {
+	if len(c.Capabilities) == 0 {
+		return nil
+	}
+	if !kinded {
+		return []string{fmt.Sprintf("%s claims %s with capabilities, and only a kinded bench's claim carries them",
+			module, c.Name)}
+	}
+	var problems []string
+	for _, w := range c.Capabilities {
+		if !ChannelCapabilities[w] && !maxLength.MatchString(w) {
+			problems = append(problems, fmt.Sprintf(
+				"%s claims %s with the capability %q, which channel-capabilities/1 does not have", module, c.Name, w))
+		}
+	}
+	return problems
+}
+
 // kindProblems is a claim judged against a declared seat's kind: a kinded bench takes one claim per kind,
 // a usable name; any other seat takes none.
 func kindProblems(module string, c Claim, s SeatDeclaration, taken map[string]string) []string {
+	if problems := capabilityProblems(module, c, s.Kinded); len(problems) > 0 {
+		return problems
+	}
 	switch {
 	case !s.Kinded && c.Kind != "":
 		return []string{fmt.Sprintf("%s claims %s of kind %q, and only a kinded bench takes a kind",