diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass_test.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass_test.go
index 431eea94..da114536 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass_test.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass_test.go
@@ -365,9 +365,14 @@ func putOfTheBus(t *testing.T) {
 
 	buildKV := mem()
 	buildKV.values[bkey] = built
-	modules := mem()
-	modules.values["nats"] = mod
-	s := newPutTools(memStore{putsState: putsKV, builds.BuilderModule + ".builds": buildKV, buckets.IndexerModule + ".modules": modules})
+	// Issue 1966: newest is asked of the indexer's first view of modules, never read from its bus state.
+	indexer := &fakeIndexer{views: map[string]map[string][]byte{"mesh-delivery-indexer.modules": {"mesh-catalog": mod, "nats": mod}}}
+	s := newPutTools(memStore{putsState: putsKV, builds.BuilderModule + ".builds": buildKV}, func(key string, body any) (json.RawMessage, error) {
+		if raw, ok, err := indexer.answer(key, body); ok {
+			return raw, err
+		}
+		return nil, fmt.Errorf("%s is not served here", key)
+	})
 	s.now = func() time.Time { return now }
 	was := answerWithin
 	answerWithin = 0
@@ -378,8 +383,11 @@ func putOfTheBus(t *testing.T) {
 	if got, err := s.version("nats", "fd497ab80000"); err != nil || got != fp {
 		t.Errorf("the prefix of the fingerprint built reads %q, %v", got, err)
 	}
-	if got, err := s.version("nats", "newest"); err != nil || got != fp {
-		t.Errorf("newest reads %q, %v", got, err)
+	if got, err := s.version("nats", "newest"); err != nil || got != fp || indexer.asks["mesh-delivery-indexer.modules"] != 2 {
+		t.Errorf("newest reads %q, %v, asking %d pages of the indexer's first view (want its 2)", got, err, indexer.asks["mesh-delivery-indexer.modules"])
+	}
+	if _, err := s.version("ghost", "newest"); err == nil || !strings.Contains(err.Error(), "holds no module ghost") {
+		t.Errorf("newest of a module the indexer does not hold: %v", err)
 	}
 	ans, err := s.doPut(map[string]any{"node": "novox", "module": "nats", "version": fp, "hold": "true", "why": "the bus's user list"}, "shanks.node-tools")
 	if err != nil {
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/tools.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/tools.go
index 62f94dbd..1d2a8313 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/tools.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/tools.go
@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"mesh-delivery-assigner/internal/buckets"
 	"mesh-delivery-assigner/internal/puts"
 	"os"
 	"regexp"
@@ -45,7 +44,9 @@ type store interface {
 
 // putTools serves the tools over a store, and keeps the newest value of every put it heard, to wait on.
 type putTools struct {
-	st  store
+	st store
+	// ask asks a module's tool (stdio.Ask, or a test's): the indexer's first view of modules for newest.
+	ask func(key string, body any) (json.RawMessage, error)
 	now func() time.Time
 	mu  sync.Mutex
 	// heard is every put the watch handed, by key; changed is closed and replaced at each.
@@ -53,8 +54,8 @@ type putTools struct {
 	changed chan struct{}
 }
 
-func newPutTools(st store) *putTools {
-	return &putTools{st: st, now: time.Now, heard: map[string][]byte{}, changed: make(chan struct{})}
+func newPutTools(st store, ask func(string, any) (json.RawMessage, error)) *putTools {
+	return &putTools{st: st, ask: ask, now: time.Now, heard: map[string][]byte{}, changed: make(chan struct{})}
 }
 
 // hear takes a put's change in from the watch.
@@ -78,10 +79,12 @@ func (s *putTools) version(module, version string) (string, error) {
 	v := strings.ToLower(strings.TrimSpace(version))
 	switch {
 	case v == "newest":
-		raw, _, found, err := s.st.get(buckets.ModulesRead, module)
+		// Asked of the indexer's first view of modules, never read from its bus state (ADR 0596, ADR 0621; issue 1966).
+		mods, err := indexerView(s.ask, indexerModules)
 		if err != nil {
 			return "", fmt.Errorf("the indexer's modules cannot be read: %w", err)
 		}
+		raw, found := mods[module]
 		if !found {
 			return "", fmt.Errorf("the indexer holds no module %s at the trunk", module)
 		}
@@ -345,7 +348,7 @@ func (runtimeStore) keys(state string) ([]string, error) { return stdio.State(st
 
 // serveTools serves the tools to the runtime until it stops, hearing every put to answer assigner_put with its first steps.
 func serveTools() error {
-	s := newPutTools(runtimeStore{})
+	s := newPutTools(runtimeStore{}, stdio.Ask)
 	go func() {
 		<-stdio.Served()
 		for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
diff --git a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main.go b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main.go
index 72953a5e..84a9c770 100644
--- a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main.go
+++ b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main.go
@@ -1,6 +1,6 @@
 // Command mesh-delivery-checker-tools serves the checker's read tools (novox/hq ADR 0484 clause 13, issue 1686): the runtime
-// launches it for a call, it reads the checker's verdicts and kept states and the indexer's candidates through the checker's
-// state and reads. It writes only the tries (the try's tools) and, asking a check again by hand, one verdict. The checker is the other program: it serves no tool (ADR 0437 §4).
+// launches it for a call, it reads the checker's verdicts and kept states through the checker's state and reads, and the
+// indexer's candidates and modules through the indexer's read tools. It writes only the tries (the try's tools) and, asking a check again by hand, one verdict. The checker is the other program: it serves no tool (ADR 0437 §4).
 package main
 
 import (
@@ -18,6 +18,7 @@ import (
 	"git.novox.be/novox/mesh-delivery/contracts/go/seats/meshdeliverychecker"
 	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
 	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/buscalls"
 	"git.novox.be/novox/mesh-sdk/go/views"
 )
 
@@ -58,6 +59,52 @@ func read(s stdio.KeptState) check.StateRead {
 	}}
 }
 
+// ownerRead is a state of another module read through that module's ordinary read tool (views.ReadTool), asked through ask
+// (stdio.Ask, or a test's): its keys with no argument, one key's value with key. Another module's data is asked through its
+// tools, never read from its bus state (novox/hq ADR 0596); the manifest invokes the tool, and the owner answers every reader
+// that invokes it. Each read is asked when it is read: the owner's state is the truth, and the tools keep no copy.
+func ownerRead(ask func(string, any) (json.RawMessage, error), tool string) check.StateRead {
+	call := func(args map[string]any, into any) error {
+		reads.Add(1)
+		raw, err := ask(tool, args)
+		if err != nil {
+			return fmt.Errorf("%s does not answer: %w", tool, err)
+		}
+		answer, said, ok := buscalls.Unwrap(raw)
+		if !ok {
+			return fmt.Errorf("%s answered: %s", tool, said)
+		}
+		if err := json.Unmarshal(answer, into); err != nil {
+			return fmt.Errorf("%s answered what does not decode: %w", tool, err)
+		}
+		return nil
+	}
+	return check.StateRead{
+		Keys: func() ([]string, error) {
+			var a views.ReadAnswer
+			if err := call(map[string]any{}, &a); err != nil {
+				return nil, err
+			}
+			return a.Keys, nil
+		},
+		Get: func(key string) (json.RawMessage, error) {
+			var a views.KeyAnswer
+			if err := call(map[string]any{"key": key}, &a); err != nil {
+				return nil, err
+			}
+			if !a.Found {
+				return nil, nil
+			}
+			return a.Value, nil
+		}}
+}
+
+// The indexer's read tools the tools ask for its candidates and modules (the manifest's invokes).
+const (
+	indexerCandidatesTool = check.IndexerModule + ".indexer_read_candidates"
+	indexerModulesTool    = check.IndexerModule + ".indexer_read_modules"
+)
+
 // runsOf says which commit the mesh runs of a module from the indexer's modules state, as the checker's own record of it does
 // (the commit the module's record was computed at); "" when the record is not readable.
 type runsOf struct{ modules check.StateRead }
@@ -371,13 +418,13 @@ func stepBound() time.Duration {
 }
 
 func main() {
-	r := check.Reader{VerdictState: read(stdio.State("verdicts")), KeptState: read(stdio.State("kept")), CandidateState: read(stdio.State("mesh-delivery-indexer.candidates")),
+	r := check.Reader{VerdictState: read(stdio.State("verdicts")), KeptState: read(stdio.State("kept")), CandidateState: ownerRead(stdio.Ask, indexerCandidatesTool),
 		PreviewState: read(stdio.State("previews")), InputState: read(stdio.State(check.InputsStateName)),
 		StepStates: map[string]check.StateRead{"mesh-build-go": read(stdio.State("mesh-build-go.steps")), "mesh-build-node": read(stdio.State("mesh-build-node.steps"))},
 		HaveState:  read(stdio.State("node-engine.have")), StepBound: stepBound(),
 		TurnState: read(stdio.State("mesh-delivery-gate.turns")), HearingState: read(stdio.State(buildrun.HearingState)),
 		AskState: read(stdio.State(check.AsksState)), BuildState: read(stdio.State("mesh-delivery-builder.builds"))}
-	r.Runs = runsOf{read(stdio.State("mesh-delivery-indexer.modules"))} // the node-engine at the commit the mesh runs, as the checker reads it
+	r.Runs = runsOf{ownerRead(stdio.Ask, indexerModulesTool)} // the node-engine at the commit the mesh runs, as the checker reads it
 	tries := stdio.State(check.TriesState)
 	source := stdio.State("mesh-delivery-gate.source")
 	trunks := func() (map[string]string, error) {
diff --git a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main_test.go b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main_test.go
index 01b9bef8..96f73db1 100644
--- a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main_test.go
+++ b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker-tools/main_test.go
@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"os"
+	"regexp"
 	"slices"
 	"strings"
 	"testing"
@@ -67,6 +68,73 @@ func TestTheToolsServedAreTheFiveReadTools(t *testing.T) {
 	if _, err := RequestTools(check.StateRead{})[0].Run(map[string]any{}); err == nil {
 		t.Errorf("answered with no state to read")
 	}
+	// Issue 1966: another module's state is asked of its read tool, never read from its bus state (ADR 0596). Every
+	// stdio.State this program names of another module is one its manifest declares under reads, which the runtime grants;
+	// the indexer's candidates and modules are asked of indexer_read_candidates and indexer_read_modules, which it invokes.
+	t.Run("1966: another module's state is read only where the manifest declares it", func(t *testing.T) {
+		raw, err := os.ReadFile("../../module.json")
+		if err != nil {
+			t.Fatal(err)
+		}
+		var man struct {
+			Reads   []string `json:"reads"`
+			Invokes []string `json:"invokes"`
+		}
+		if err := json.Unmarshal(raw, &man); err != nil {
+			t.Fatal(err)
+		}
+		src, err := os.ReadFile("main.go")
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, m := range regexp.MustCompile(`stdio\.State\("([^"]+\.[^"]+)"\)`).FindAllStringSubmatch(string(src), -1) {
+			if !slices.Contains(man.Reads, m[1]) {
+				t.Errorf("main.go reads %s, which the manifest does not declare under reads: the runtime refuses it", m[1])
+			}
+		}
+		for _, tool := range []string{indexerCandidatesTool, indexerModulesTool} {
+			if !slices.Contains(man.Invokes, tool) {
+				t.Errorf("the manifest does not invoke %s", tool)
+			}
+		}
+	})
+	for _, c := range []struct {
+		name, key, answer, want string
+		failed                  bool
+	}{
+		{name: "the keys", answer: `{"owner":"mesh-delivery-indexer","state":"candidates","keys":["a","b"]}`, want: "[a b]"},
+		{name: "one key, wrapped as the tool runner hands it", key: "a",
+			answer: `{"content":[{"type":"text","text":"{\"key\":\"a\",\"found\":true,\"value\":{\"commit\":\"c\"}}"}]}`, want: `{"commit":"c"}`},
+		{name: "a key the indexer does not hold", key: "gone", answer: `{"key":"gone","found":false}`, want: ""},
+		{name: "the tool refused", key: "a", answer: `{"content":[{"type":"text","text":"refused"}],"isError":true}`, failed: true},
+	} {
+		t.Run("1966: the indexer's read tool, "+c.name, func(t *testing.T) {
+			var asked []string
+			r := ownerRead(func(key string, body any) (json.RawMessage, error) {
+				b, _ := json.Marshal(body)
+				asked = append(asked, key+" "+string(b))
+				return json.RawMessage(c.answer), nil
+			}, indexerCandidatesTool)
+			var got string
+			var err error
+			if c.key == "" {
+				var keys []string
+				keys, err = r.Keys()
+				got = strings.Trim(strings.Join([]string{"[", strings.Join(keys, " "), "]"}, ""), " ")
+			} else {
+				var raw json.RawMessage
+				raw, err = r.Get(c.key)
+				got = string(raw)
+			}
+			want := []string{indexerCandidatesTool + " {}"}
+			if c.key != "" {
+				want = []string{indexerCandidatesTool + ` {"key":"` + c.key + `"}`}
+			}
+			if (err != nil) != c.failed || (!c.failed && got != c.want) || !slices.Equal(asked, want) {
+				t.Errorf("read %q, %v, asking %v; want %q, failed %v, asking %v", got, err, asked, c.want, c.failed, want)
+			}
+		})
+	}
 	// With nothing to read from a tool says so and changes nothing.
 	for _, tl := range Tools(check.Reader{}) {
 		if tl.Name == check.StatusReadTool {