Send global stamps as a verae-meta-git/1 history.

Optional metadata or restamp builds the same commit history as node-red. A call that omits both stays digest-only with restamp false. Local and shared stamps reject metadata.

internal/metadatahist/history.go

@@ -0,0 +1,341 @@
+// Package metadatahist builds verae-meta-git/1 documents the same way as
+// node-red-contrib-verae lib/metadata-history.js. Blank values do not delete
+// fields. A document that already uses the schema is stored as sent.
+package metadatahist
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"sort"
+	"time"
+)
+
+const Schema = "verae-meta-git/1"
+
+func IsBlank(value any) bool {
+	if value == nil {
+		return true
+	}
+	switch v := value.(type) {
+	case string:
+		for _, r := range v {
+			if r != ' ' && r != '\t' && r != '\n' && r != '\r' {
+				return false
+			}
+		}
+		return true
+	case []any:
+		return len(v) == 0
+	case map[string]any:
+		return len(v) == 0
+	default:
+		return false
+	}
+}
+
+func isObject(value any) (map[string]any, bool) {
+	m, ok := value.(map[string]any)
+	return m, ok
+}
+
+func clone(value any) any {
+	switch v := value.(type) {
+	case []any:
+		out := make([]any, len(v))
+		for i := range v {
+			out[i] = clone(v[i])
+		}
+		return out
+	case map[string]any:
+		out := make(map[string]any, len(v))
+		for k, item := range v {
+			out[k] = clone(item)
+		}
+		return out
+	default:
+		return v
+	}
+}
+
+func jsonScalar(value any) string {
+	var buf bytes.Buffer
+	enc := json.NewEncoder(&buf)
+	enc.SetEscapeHTML(false)
+	_ = enc.Encode(value)
+	b := bytes.TrimRight(buf.Bytes(), "\n")
+	return string(b)
+}
+
+func canonical(value any) string {
+	switch v := value.(type) {
+	case []any:
+		parts := make([]string, len(v))
+		for i := range v {
+			parts[i] = canonical(v[i])
+		}
+		return "[" + join(parts) + "]"
+	case map[string]any:
+		keys := make([]string, 0, len(v))
+		for k := range v {
+			keys = append(keys, k)
+		}
+		sort.Strings(keys)
+		parts := make([]string, len(keys))
+		for i, k := range keys {
+			parts[i] = jsonScalar(k) + ":" + canonical(v[k])
+		}
+		return "{" + join(parts) + "}"
+	default:
+		return jsonScalar(value)
+	}
+}
+
+func join(parts []string) string {
+	out := ""
+	for i, p := range parts {
+		if i > 0 {
+			out += ","
+		}
+		out += p
+	}
+	return out
+}
+
+func same(a, b any) bool { return canonical(a) == canonical(b) }
+
+func ExtendSnapshot(base, patch map[string]any) map[string]any {
+	out := map[string]any{}
+	if base != nil {
+		if cloned, ok := clone(base).(map[string]any); ok {
+			out = cloned
+		}
+	}
+	if patch == nil {
+		return out
+	}
+	for key, next := range patch {
+		if IsBlank(next) {
+			continue
+		}
+		prev, has := out[key]
+		prevObj, prevIsObj := isObject(prev)
+		nextObj, nextIsObj := isObject(next)
+		prevArr, prevIsArr := prev.([]any)
+		nextArr, nextIsArr := next.([]any)
+		switch {
+		case has && prevIsObj && nextIsObj:
+			out[key] = ExtendSnapshot(prevObj, nextObj)
+		case prevIsArr && nextIsArr:
+			extra := nonBlank(nextArr)
+			if len(extra) > 0 {
+				out[key] = append(append([]any{}, prevArr...), extra...)
+			}
+		case nextIsArr:
+			extra := nonBlank(nextArr)
+			if len(extra) == 0 {
+				continue
+			}
+			if prevIsArr {
+				out[key] = append(append([]any{}, prevArr...), extra...)
+			} else {
+				out[key] = extra
+			}
+		case nextIsObj:
+			nestedBase := map[string]any{}
+			if prevIsObj {
+				nestedBase = prevObj
+			}
+			nested := ExtendSnapshot(nestedBase, nextObj)
+			if !IsBlank(nested) {
+				out[key] = nested
+			}
+		default:
+			out[key] = clone(next)
+		}
+	}
+	return out
+}
+
+func nonBlank(items []any) []any {
+	out := make([]any, 0, len(items))
+	for _, item := range items {
+		if !IsBlank(item) {
+			out = append(out, clone(item))
+		}
+	}
+	return out
+}
+
+func ChangesBetween(before, after map[string]any) map[string]any {
+	added := map[string]any{}
+	extended := map[string]any{}
+	updated := map[string]any{}
+	if before == nil {
+		before = map[string]any{}
+	}
+	if after == nil {
+		after = map[string]any{}
+	}
+	keys := map[string]struct{}{}
+	for k := range before {
+		keys[k] = struct{}{}
+	}
+	for k := range after {
+		keys[k] = struct{}{}
+	}
+	ordered := make([]string, 0, len(keys))
+	for k := range keys {
+		ordered = append(ordered, k)
+	}
+	sort.Strings(ordered)
+	for _, key := range ordered {
+		next, hasNext := after[key]
+		if !hasNext {
+			continue
+		}
+		prev, hasPrev := before[key]
+		if !hasPrev {
+			added[key] = clone(next)
+			continue
+		}
+		if same(prev, next) {
+			continue
+		}
+		prevObj, prevIsObj := isObject(prev)
+		nextObj, nextIsObj := isObject(next)
+		prevArr, prevIsArr := prev.([]any)
+		nextArr, nextIsArr := next.([]any)
+		switch {
+		case prevIsObj && nextIsObj:
+			nested := ChangesBetween(prevObj, nextObj)
+			if !IsBlank(nested["added"]) || !IsBlank(nested["extended"]) || !IsBlank(nested["updated"]) {
+				extended[key] = nested
+			}
+		case prevIsArr && nextIsArr && len(nextArr) >= len(prevArr):
+			appended := nextArr[len(prevArr):]
+			if len(appended) > 0 {
+				extended[key] = map[string]any{"appended": clone(appended)}
+			}
+		default:
+			updated[key] = map[string]any{"from": clone(prev), "to": clone(next)}
+		}
+	}
+	return map[string]any{"added": added, "extended": extended, "updated": updated}
+}
+
+func commitID(commit map[string]any) string {
+	material := canonical(map[string]any{
+		"parent":   commit["parent"],
+		"at":       commit["at"],
+		"message":  commit["message"],
+		"snapshot": commit["snapshot"],
+	})
+	sum := sha256.Sum256([]byte(material))
+	return hex.EncodeToString(sum[:])
+}
+
+func IsHistory(value any) bool {
+	m, ok := isObject(value)
+	if !ok || m["schema"] != Schema {
+		return false
+	}
+	if _, ok := m["commits"].([]any); !ok {
+		return false
+	}
+	_, ok = isObject(m["snapshot"])
+	return ok
+}
+
+func historyFromSnapshot(snapshot map[string]any, at string) map[string]any {
+	stored, _ := clone(snapshot).(map[string]any)
+	commit := map[string]any{
+		"parent":   nil,
+		"at":       at,
+		"message":  "stamp",
+		"snapshot": stored,
+		"changes":  ChangesBetween(map[string]any{}, stored),
+	}
+	commit["id"] = commitID(commit)
+	return map[string]any{
+		"schema":   Schema,
+		"head":     commit["id"],
+		"snapshot": clone(stored),
+		"commits":  []any{commit},
+	}
+}
+
+func coerceHistory(existing any, at string) map[string]any {
+	if IsHistory(existing) {
+		cloned, _ := clone(existing).(map[string]any)
+		return cloned
+	}
+	if m, ok := isObject(existing); ok && !IsBlank(m) {
+		return historyFromSnapshot(m, at)
+	}
+	return map[string]any{
+		"schema":   Schema,
+		"head":     nil,
+		"snapshot": map[string]any{},
+		"commits":  []any{},
+	}
+}
+
+func hasChanges(changes map[string]any) bool {
+	return !IsBlank(changes["added"]) || !IsBlank(changes["extended"]) || !IsBlank(changes["updated"])
+}
+
+// Append builds the next history document. A nil result means the caller
+// should omit metadata. restamp with a blank patch still appends one commit.
+func Append(existing any, patch map[string]any, restamp bool, at, priorAt, message string) map[string]any {
+	if at == "" {
+		at = time.Now().UTC().Format(time.RFC3339Nano)
+	}
+	blankPatch := patch == nil || IsBlank(patch) || IsBlank(ExtendSnapshot(map[string]any{}, patch))
+	if !restamp && blankPatch && !IsHistory(existing) && (existing == nil || IsBlank(existing)) {
+		return nil
+	}
+	if priorAt == "" {
+		priorAt = at
+	}
+	doc := coerceHistory(existing, priorAt)
+	head, _ := doc["head"].(string)
+	if !restamp && blankPatch {
+		if head != "" {
+			return doc
+		}
+		return nil
+	}
+	base, _ := doc["snapshot"].(map[string]any)
+	snapshot := ExtendSnapshot(base, patch)
+	changes := ChangesBetween(base, snapshot)
+	if !restamp && !hasChanges(changes) && head != "" {
+		return doc
+	}
+	msg := message
+	if msg == "" {
+		if head != "" {
+			msg = "restamp"
+		} else {
+			msg = "stamp"
+		}
+	}
+	var parent any
+	if head != "" {
+		parent = head
+	}
+	commit := map[string]any{
+		"parent":   parent,
+		"at":       at,
+		"message":  msg,
+		"snapshot": snapshot,
+		"changes":  changes,
+	}
+	commit["id"] = commitID(commit)
+	commits, _ := doc["commits"].([]any)
+	doc["commits"] = append(commits, commit)
+	doc["head"] = commit["id"]
+	doc["snapshot"] = snapshot
+	return doc
+}

internal/metadatahist/history_test.go

@@ -0,0 +1,52 @@
+package metadatahist
+
+import "testing"
+
+func TestAppendMatchesNodeReference(t *testing.T) {
+	first := Append(nil, map[string]any{"title": "deed", "tags": []any{"a"}}, false, "2026-10-11T01:00:00.000Z", "", "stamp")
+	if first["head"] != "161ff3344ba776ae7201b73914c0e7500116ac9dde02e1967a761b7089c41fa7" {
+		t.Fatalf("head1=%v", first["head"])
+	}
+	second := Append(first, map[string]any{"title": "deed-2", "tags": []any{"b"}, "place": "office"}, true, "2026-10-11T02:00:00.000Z", "", "correct the title")
+	if second["head"] != "c606e41ccbf4c0f9f653b21759df83ecda25262621075db3a153b592270fd918" {
+		t.Fatalf("head2=%v", second["head"])
+	}
+	snap := second["snapshot"].(map[string]any)
+	if snap["title"] != "deed-2" || snap["place"] != "office" {
+		t.Fatalf("snapshot=%v", snap)
+	}
+	tags := snap["tags"].([]any)
+	if len(tags) != 2 || tags[0] != "a" || tags[1] != "b" {
+		t.Fatalf("tags=%v", tags)
+	}
+	commits := second["commits"].([]any)
+	tip := commits[1].(map[string]any)
+	if tip["parent"] != first["head"] {
+		t.Fatalf("parent=%v", tip["parent"])
+	}
+	if _, ok := tip["changes"].(map[string]any)["removed"]; ok {
+		t.Fatal("removed key")
+	}
+}
+
+func TestBlankRestampKeepsSnapshot(t *testing.T) {
+	base := map[string]any{"title": "deed", "note": "keep", "tags": []any{"a"}}
+	next := Append(base, map[string]any{"title": "", "note": nil, "tags": []any{}}, true, "2026-10-11T01:47:00.000Z", "2026-10-11T01:00:00.000Z", "")
+	snap := next["snapshot"].(map[string]any)
+	if snap["title"] != "deed" || snap["note"] != "keep" {
+		t.Fatalf("snapshot=%v", snap)
+	}
+	commits := next["commits"].([]any)
+	if len(commits) != 2 {
+		t.Fatalf("commits=%d", len(commits))
+	}
+}
+
+func TestOmitWhenEmpty(t *testing.T) {
+	if Append(nil, nil, false, "2026-10-11T01:00:00.000Z", "", "") != nil {
+		t.Fatal("expected omit")
+	}
+	if Append(nil, map[string]any{}, false, "2026-10-11T01:00:00.000Z", "", "") != nil {
+		t.Fatal("expected omit")
+	}
+}

internal/tools/handlers.go

@@ -49,7 +49,11 @@ func (d *Deps) stamp(ctx context.Context, req *mcp.CallToolRequest, in StampArgs
 		if err != nil {
 			return nil, ReceiptsOut{}, err
 		}
-		rec, err := d.Global.Stamp(ctx, in.SHA256, tok)
+		rec, err := d.Global.StampWithMeta(ctx, in.SHA256, tok, veraetime.StampMeta{
+			Metadata: in.Metadata,
+			Restamp:  in.Restamp,
+			Message:  in.Message,
+		})
 		if err != nil {
 			return nil, ReceiptsOut{}, err
 		}
@@ -61,6 +65,9 @@ func (d *Deps) stamp(ctx context.Context, req *mcp.CallToolRequest, in StampArgs
 		}
 		return nil, ReceiptsOut{Receipts: []ReceiptDTO{fromGlobal(rec)}}, nil
 	case "local", "shared":
+		if len(in.Metadata) > 0 || in.Restamp {
+			return nil, ReceiptsOut{}, fmt.Errorf("metadata history is stored on global stamps")
+		}
 		if d.Ledger == nil {
 			return nil, ReceiptsOut{}, fmt.Errorf("ledger not configured")
 		}
@@ -98,7 +105,21 @@ func (d *Deps) stampBatch(ctx context.Context, req *mcp.CallToolRequest, in Stam
 		if err != nil {
 			return nil, StampBatchOut{}, err
 		}
-		br, err := d.Global.StampBatch(ctx, in.SHA256s, tok)
+		var metas []veraetime.StampMeta
+		if len(in.Metadata) > 0 || in.Restamp {
+			if len(in.Metadata) > 0 && len(in.Metadata) != len(in.SHA256s) {
+				return nil, StampBatchOut{}, fmt.Errorf("metadata must have one entry per digest")
+			}
+			metas = make([]veraetime.StampMeta, len(in.SHA256s))
+			for i := range in.SHA256s {
+				metas[i].Restamp = in.Restamp
+				metas[i].Message = in.Message
+				if i < len(in.Metadata) {
+					metas[i].Metadata = in.Metadata[i]
+				}
+			}
+		}
+		br, err := d.Global.StampBatchWithMeta(ctx, in.SHA256s, tok, metas)
 		if err != nil {
 			return nil, StampBatchOut{}, err
 		}
@@ -108,6 +129,9 @@ func (d *Deps) stampBatch(ctx context.Context, req *mcp.CallToolRequest, in Stam
 		}
 		return nil, out, nil
 	case "local", "shared":
+		if len(in.Metadata) > 0 || in.Restamp {
+			return nil, StampBatchOut{}, fmt.Errorf("metadata history is stored on global stamps")
+		}
 		if d.Ledger == nil {
 			return nil, StampBatchOut{}, fmt.Errorf("ledger not configured")
 		}

internal/tools/register.go

@@ -27,7 +27,7 @@ func Register(s *mcp.Server, d *Deps) {
 	}
 	mcp.AddTool(s, &mcp.Tool{
 		Name:        "stamp",
-		Description: "Commit a SHA-256. scope=local is the leaf file ledger; scope=global posts digest and restamp=false to api.veraetime.net and reuses the first CID.",
+		Description: "Commit a SHA-256. scope=local is the leaf file ledger. scope=global posts the digest to api.veraetime.net and reuses the first CID unless restamp is true. Optional metadata is sent as a verae-meta-git/1 history; blank values do not delete fields.",
 	}, d.stamp)
 	mcp.AddTool(s, &mcp.Tool{
 		Name:        "stamp_batch",

internal/tools/types.go

@@ -2,10 +2,13 @@ package tools
 
 // StampArgs is the stamp tool input.
 type StampArgs struct {
-	SHA256 string `json:"sha256" jsonschema:"SHA-256 digest (64 hex; optional sha256: prefix)"`
-	Scope  string `json:"scope,omitempty" jsonschema:"local, shared, or global (default local)"`
-	CubeID string `json:"cube_id,omitempty" jsonschema:"optional cube id"`
-	OrgID  string `json:"org_id,omitempty" jsonschema:"optional org id"`
+	SHA256   string         `json:"sha256" jsonschema:"SHA-256 digest (64 hex; optional sha256: prefix)"`
+	Scope    string         `json:"scope,omitempty" jsonschema:"local, shared, or global (default local)"`
+	CubeID   string         `json:"cube_id,omitempty" jsonschema:"optional cube id"`
+	OrgID    string         `json:"org_id,omitempty" jsonschema:"optional org id"`
+	Metadata map[string]any `json:"metadata,omitempty" jsonschema:"optional plain object or a verae-meta-git/1 history. Blank values do not delete fields. Global scope only."`
+	Restamp  bool           `json:"restamp,omitempty" jsonschema:"when true, append metadata onto the previous global stamp for this digest"`
+	Message  string         `json:"message,omitempty" jsonschema:"optional history commit message"`
 }
 
 // VerifyArgs is the verify tool input.
@@ -85,8 +88,11 @@ type CreateUserOut struct {
 
 // StampBatchArgs is the stamp_batch tool input (DEC-659).
 type StampBatchArgs struct {
-	SHA256s []string `json:"sha256s" jsonschema:"SHA-256 digests (64 hex each), 1..500"`
-	Scope   string   `json:"scope,omitempty" jsonschema:"global (default; charged per new digest to your Verae account) or local"`
+	SHA256s  []string         `json:"sha256s" jsonschema:"SHA-256 digests (64 hex each), 1..500"`
+	Scope    string           `json:"scope,omitempty" jsonschema:"global (default; charged per new digest to your Verae account) or local"`
+	Metadata []map[string]any `json:"metadata,omitempty" jsonschema:"optional history patch per digest, same length as sha256s. Global scope only."`
+	Restamp  bool             `json:"restamp,omitempty" jsonschema:"when true, append each metadata patch onto the previous global stamp"`
+	Message  string           `json:"message,omitempty" jsonschema:"optional history commit message for every item"`
 }
 
 // BatchItemDTO is one item of a stamp_batch answer.

internal/veraetime/client.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"git.georgelambert.org/marchon/verae-mcp-timestamping-server-go/internal/metadatahist"
 	"git.georgelambert.org/marchon/verae-mcp-timestamping-server-go/pkg/digest"
 )
 
@@ -155,8 +156,24 @@ func (c *Client) AuthPath() string { return c.authPath }
 // BaseURL returns the API base URL.
 func (c *Client) BaseURL() string { return c.baseURL }
 
-// Stamp posts a SHA-256 digest with restamp=false.
+// StampMeta is optional history for one stamp. The zero value keeps the
+// digest-only body: restamp false and no metadata field.
+type StampMeta struct {
+	Metadata map[string]any
+	Restamp  bool
+	Message  string
+	At       string
+}
+
+// Stamp posts a SHA-256 digest with restamp=false and no metadata.
 func (c *Client) Stamp(ctx context.Context, dig, bearer string) (*Receipt, error) {
+	return c.StampWithMeta(ctx, dig, bearer, StampMeta{})
+}
+
+// StampWithMeta posts a digest. Metadata or Restamp sends a verae-meta-git/1
+// document. A second submit of an existing digest without Restamp, when
+// metadata was sent, returns an error so the first history is left unchanged.
+func (c *Client) StampWithMeta(ctx context.Context, dig, bearer string, meta StampMeta) (*Receipt, error) {
 	h, err := digest.NormalizeSHA256(dig)
 	if err != nil {
 		return nil, err
@@ -167,6 +184,9 @@ func (c *Client) Stamp(ctx context.Context, dig, bearer string) (*Receipt, error
 		"hashAlg": "SHA256",
 		"restamp": false,
 	}
+	if err := c.attachHistory(ctx, h, bearer, meta, payload); err != nil {
+		return nil, err
+	}
 	status, body, err := c.doJSON(ctx, http.MethodPost, c.baseURL+"/api/timestamp", payload, bearer)
 	if err != nil {
 		return nil, err
@@ -175,6 +195,9 @@ func (c *Client) Stamp(ctx context.Context, dig, bearer string) (*Receipt, error
 		return nil, authErr(status, body)
 	}
 	if status == http.StatusOK && (str(body, "certificate") != "" || truthy(body["existing"])) {
+		if payload["metadata"] != nil && !truthy(payload["restamp"]) {
+			return nil, fmt.Errorf("veraetime: digest already stamped; set restamp to append metadata")
+		}
 		cid := str(body, "certificate")
 		if cid != "" {
 			return &Receipt{
@@ -641,15 +664,105 @@ type BatchResult struct {
 	Results        []BatchItem `json:"results"`
 }
 
+func (c *Client) attachHistory(ctx context.Context, dig, bearer string, meta StampMeta, payload map[string]any) error {
+	if len(meta.Metadata) == 0 && !meta.Restamp && !metadatahist.IsHistory(meta.Metadata) {
+		return nil
+	}
+	var prior any
+	if meta.Restamp && !metadatahist.IsHistory(meta.Metadata) {
+		loaded, err := c.priorMetadata(ctx, dig, bearer)
+		if err != nil {
+			return err
+		}
+		prior = loaded
+	}
+	doc := metadatahist.Append(prior, meta.Metadata, meta.Restamp, meta.At, "", meta.Message)
+	if metadatahist.IsHistory(meta.Metadata) {
+		doc = meta.Metadata
+	}
+	if doc == nil {
+		return nil
+	}
+	payload["metadata"] = doc
+	if meta.Restamp {
+		payload["restamp"] = true
+	}
+	if commits, ok := doc["commits"].([]any); ok && len(commits) > 1 {
+		payload["restamp"] = true
+	}
+	return nil
+}
+
+func (c *Client) priorMetadata(ctx context.Context, dig, bearer string) (map[string]any, error) {
+	status, body, err := c.doJSON(ctx, http.MethodGet, c.baseURL+"/api/hash/"+dig, nil, bearer)
+	if err != nil {
+		return nil, err
+	}
+	if status == http.StatusNotFound {
+		return nil, nil
+	}
+	if status == http.StatusUnauthorized {
+		return nil, authErr(status, body)
+	}
+	if status >= 300 {
+		return nil, httpErr("hash report", status, body)
+	}
+	refs, _ := body["receipts"].([]any)
+	jobID := ""
+	for _, refAny := range refs {
+		ref, ok := refAny.(map[string]any)
+		if !ok {
+			continue
+		}
+		if id := str(ref, "jobId"); id != "" {
+			jobID = id
+		}
+	}
+	if jobID == "" {
+		return nil, nil
+	}
+	st, sb, err := c.doJSON(ctx, http.MethodGet, c.baseURL+"/api/status/"+jobID, nil, bearer)
+	if err != nil {
+		return nil, err
+	}
+	if st == http.StatusNotFound {
+		return nil, nil
+	}
+	if st == http.StatusUnauthorized {
+		return nil, authErr(st, sb)
+	}
+	if st >= 300 {
+		return nil, httpErr("status", st, sb)
+	}
+	meta, _ := sb["metadata"].(map[string]any)
+	return meta, nil
+}
+
 // StampBatch posts SHA-256 digests (restamp=false) in one batch; each new digest is charged to the key's customer.
 func (c *Client) StampBatch(ctx context.Context, digests []string, bearer string) (*BatchResult, error) {
+	return c.StampBatchWithMeta(ctx, digests, bearer, nil)
+}
+
+// StampBatchWithMeta is StampBatch with one optional history per digest.
+// A nil metas slice keeps every item digest-only. A non-nil slice must match
+// len(digests).
+func (c *Client) StampBatchWithMeta(ctx context.Context, digests []string, bearer string, metas []StampMeta) (*BatchResult, error) {
+	if metas != nil && len(metas) != len(digests) {
+		return nil, fmt.Errorf("veraetime: metadata entries (%d) must match digests (%d)", len(metas), len(digests))
+	}
 	items := make([]map[string]any, 0, len(digests))
 	for i, d := range digests {
 		h, err := digest.NormalizeSHA256(d)
 		if err != nil {
 			return nil, fmt.Errorf("sha256s[%d]: %w", i, err)
 		}
-		items = append(items, map[string]any{"data": h, "digest": h, "hashAlg": "SHA256", "restamp": false})
+		item := map[string]any{"data": h, "digest": h, "hashAlg": "SHA256", "restamp": false}
+		if metas != nil {
+			if err := c.attachHistory(ctx, h, bearer, metas[i], item); err != nil {
+				return nil, err
+			}
+		}
+		items = append(items, item)
 	}
 	status, body, err := c.doJSON(ctx, http.MethodPost, c.baseURL+"/api/batch/timestamp", map[string]any{"items": items}, bearer)
 	if err != nil {

internal/veraetime/client_test.go

@@ -381,6 +381,67 @@ func TestKeeper_UsesGlobalTokenEnv(t *testing.T) {
 	}
 }
 
+func TestStampWithMeta_SendsHistoryAndExtendsOnRestamp(t *testing.T) {
+	var posted []map[string]any
+	rt := roundTripFunc(func(r *http.Request) (*http.Response, error) {
+		switch {
+		case r.Method == http.MethodPost && strings.HasSuffix(r.URL.Path, "/api/timestamp"):
+			posted = append(posted, readJSON(t, r))
+			return jsonResp(202, map[string]any{"jobId": "job-new"}), nil
+		case r.Method == http.MethodGet && strings.Contains(r.URL.Path, "/api/hash/"):
+			return jsonResp(200, map[string]any{
+				"receipts": []any{map[string]any{"jobId": "job-old", "certificate": "QmOld"}},
+			}), nil
+		case r.Method == http.MethodGet && strings.HasSuffix(r.URL.Path, "/api/status/job-old"):
+			return jsonResp(200, map[string]any{
+				"status": "completed",
+				"metadata": map[string]any{
+					"title": "deed",
+					"tags":  []any{"a"},
+				},
+			}), nil
+		case r.Method == http.MethodGet && strings.HasSuffix(r.URL.Path, "/api/status/job-new"):
+			return jsonResp(200, map[string]any{
+				"status": "completed",
+				"result": "QmNew",
+				"metadata": map[string]any{
+					"schema": "verae-meta-git/1",
+				},
+			}), nil
+		default:
+			t.Fatalf("unexpected %s %s", r.Method, r.URL.Path)
+			return nil, nil
+		}
+	})
+	c := veraetime.NewClient("https://api.example", veraetime.WithRoundTripper(rt), veraetime.WithPollInterval(time.Millisecond))
+	_, err := c.StampWithMeta(context.Background(), sha256Empty, "tok", veraetime.StampMeta{
+		Metadata: map[string]any{"place": "office"},
+		Restamp:  true,
+		Message:  "add the place",
+		At:       "2026-10-11T02:00:00.000Z",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(posted) != 1 {
+		t.Fatalf("posts=%d", len(posted))
+	}
+	if posted[0]["restamp"] != true {
+		t.Fatalf("restamp=%v", posted[0]["restamp"])
+	}
+	doc, ok := posted[0]["metadata"].(map[string]any)
+	if !ok || doc["schema"] != "verae-meta-git/1" {
+		t.Fatalf("metadata=%v", posted[0]["metadata"])
+	}
+	snap := doc["snapshot"].(map[string]any)
+	if snap["title"] != "deed" || snap["place"] != "office" {
+		t.Fatalf("snapshot=%v", snap)
+	}
+	if _, ok := posted[0]["metadata"]; !ok {
+		t.Fatal("missing metadata")
+	}
+}
+
 func TestKeeper_UsesFreshStoredToken(t *testing.T) {
 	dir := t.TempDir()
 	path := dir + "/auth.properties"