diff --git a/go/catalogue/kept_form.go b/go/catalogue/kept_form.go
index a07f315a..6ab5ccc4 100644
--- a/go/catalogue/kept_form.go
+++ b/go/catalogue/kept_form.go
@@ -1,6 +1,8 @@
 package catalogue
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 	"sort"
 )
@@ -17,9 +19,39 @@ import (
 type KeptLayout struct {
 	// Form is the form of the kept data's layout, 0 where none is said.
 	Form int `json:"form,omitempty"`
-	// CatchUp is the module's own tool a restore of this kept data is followed by, named by the manifest that raised its
-	// form; empty where none is.
-	CatchUp string `json:"catch-up,omitempty"`
+	// CatchUp is the module's own tool a restore of this kept data is followed by, with its arguments, named by the
+	// manifest that raised its form; nil where none is (design 47 G §631).
+	CatchUp *CatchUp `json:"catch-up,omitempty"`
+}
+
+// CatchUp is a manifest's `catch-up`: the tool and the arguments it is called with (design 47 G §631).
+type CatchUp struct {
+	Tool      string         `json:"tool"`
+	Arguments map[string]any `json:"arguments,omitempty"`
+}
+
+// UnmarshalJSON reads the object {tool, arguments} whole, and a string of before G as {tool, arguments: {}}.
+func (c *CatchUp) UnmarshalJSON(raw []byte) error {
+	trimmed := bytes.TrimSpace(raw)
+	if len(trimmed) > 0 && trimmed[0] == '"' {
+		var tool string
+		if err := json.Unmarshal(trimmed, &tool); err != nil {
+			return err
+		}
+		*c = CatchUp{Tool: tool}
+		return nil
+	}
+	var full struct {
+		Tool      string         `json:"tool"`
+		Arguments map[string]any `json:"arguments"`
+	}
+	dec := json.NewDecoder(bytes.NewReader(trimmed))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&full); err != nil {
+		return fmt.Errorf("a catch-up is {tool, arguments}: %w", typedUnknown(err))
+	}
+	*c = CatchUp{Tool: full.Tool, Arguments: full.Arguments}
+	return nil
 }
 
 // refuse is the one reading of a layout's form every kept kind's decoder calls: a form is a whole number from 0, and one
diff --git a/go/catalogue/kept_form_test.go b/go/catalogue/kept_form_test.go
index 88a29602..0787b165 100644
--- a/go/catalogue/kept_form_test.go
+++ b/go/catalogue/kept_form_test.go
@@ -13,8 +13,8 @@ func TestAKeptDataSaysItsFormAndItsCatchUp(t *testing.T) {
 	m, err := decodeForTest([]byte(`{"module":"x","version":"1","tools":["x_take_in"],
 		"state": ["seen", {"name":"modules","history":20,"form":1,"catch-up":"x_take_in"}],
 		"logs": [{"name":"acts","form":2}],
-		"streams": [{"name":"forge","events":["merged"],"form":1,"catch-up":"x_take_in"}],
-		"objects": [{"name":"revisions","max-mib":64,"form":1,"catch-up":"x_take_in"}],
+		"streams": [{"name":"forge","events":["merged"],"form":1,"catch-up":{"tool":"x_take_in","arguments":{"all":true}}}],
+		"objects": [{"name":"revisions","max-mib":64,"form":1,"catch-up":{"tool":"x_take_in","arguments":{"all":true}}}],
 		"requires": [
 			{"name":"records","storage":"ledger","template":"ledger","form":3,"catch-up":"x_take_in"},
 			{"name":"holds","storage":"key-value","template":"state"},
@@ -27,13 +27,13 @@ func TestAKeptDataSaysItsFormAndItsCatchUp(t *testing.T) {
 	want := []KeptDeclared{
 		{"acts", KeptKindLog, KeptLayout{Form: 2}},
 		{"blobs", KeptKindObjects, KeptLayout{Form: 4}},
-		{"forge", KeptKindStream, KeptLayout{1, "x_take_in"}},
+		{"forge", KeptKindStream, KeptLayout{1, &CatchUp{Tool: "x_take_in", Arguments: map[string]any{"all": true}}}},
 		{"history", KeptKindLog, KeptLayout{Form: 1}},
 		{"holds", KeptKindState, KeptLayout{}},
 		{"marks", KeptKindStream, KeptLayout{}},
-		{"modules", KeptKindState, KeptLayout{1, "x_take_in"}},
-		{"records", KeptKindLedger, KeptLayout{3, "x_take_in"}},
-		{"revisions", KeptKindObjects, KeptLayout{1, "x_take_in"}},
+		{"modules", KeptKindState, KeptLayout{1, &CatchUp{Tool: "x_take_in"}}},
+		{"records", KeptKindLedger, KeptLayout{3, &CatchUp{Tool: "x_take_in"}}},
+		{"revisions", KeptKindObjects, KeptLayout{1, &CatchUp{Tool: "x_take_in", Arguments: map[string]any{"all": true}}}},
 		{"seen", KeptKindState, KeptLayout{}},
 	}
 	if got := KeptDeclarations(m); !reflect.DeepEqual(got, want) {
@@ -60,7 +60,7 @@ func TestAKeptDataSaysItsFormAndItsCatchUp(t *testing.T) {
 	}
 	changes := FormChanges(running, applied)
 	wantChanges := []FormChange{
-		{Name: "acts", Kind: KeptKindLog, Running: &KeptLayout{}, Applied: &KeptLayout{1, "x_take_in"}},
+		{Name: "acts", Kind: KeptKindLog, Running: &KeptLayout{}, Applied: &KeptLayout{1, &CatchUp{Tool: "x_take_in"}}},
 		{Name: "fresh", Kind: KeptKindState, Applied: &KeptLayout{}},
 		{Name: "modules", Kind: KeptKindState, Running: &KeptLayout{}},
 	}