Answer architecture round 1: share a step down's draw per draw group and pick, own descend's pins, name the spelling to write, and record the .. decision

AGENTS.md

@@ -80,6 +80,7 @@ In [docs/decisions.md](docs/decisions.md):
 - `parent` names the link column and the table alike
 - After a row, a path names a column or a linked table
 - A selected row is fixed, not drawn, and an unnamed read beside it is refused
+- `..` steps up to the parent row, and a step down after it draws once per draw group or pick
 - A table selects by one key column, a code, never a free-form name
 - A parent row with no child row is a load error
 - The choice-of-rows fence guards a data file's root, and requires string fields

README.md

@@ -585,11 +585,17 @@ fejkdata -d ./mydata '{/city as c}{c}, {c..country.name}'  # Oslo, Norway
 ```
 
 It steps up from a selected row, a drawn row or a [name](#names) bound to a row, one level
-per `..`: `{l..municipality..region.name}`. After it, `.` steps down again, drawing
+per `..`: `{l..municipality..region.name}`. `.country` after a row still reads the link
-inside the row stepped up to. `.country` after a row still reads the link column's cell,
+column's cell, `NO`.
-`NO`. A `..` that names anything but the parent table is an error naming the parent, and
+
-so is a selector after a `..`, which could name a row outside the one stepped up to:
+After a `..`, `.` steps down again, drawing afresh inside the row stepped up to, apart from
-select rows before the `..`. `--list` advertises no path with a `..`. At the start of a
+the row the path stepped up from. Paths stepping down from one `..` read one draw, as one
+reference path does: `{/city..country.city.name}` and `{/city..country.city.population}`
+describe one city, within a render and [draw group](#draw-group), or within a name's pick.
+
+A `..` that names anything but the parent table is an error naming the parent. A selector
+after a `..` is an error naming the table to select from, since it could name a row outside
+the one stepped up to. `--list` advertises no path with a `..`. At the start of a
 reference, `..` is the folder above ([References](#references)).
 
 ### Options and fields

docs/decisions.md

@@ -511,6 +511,22 @@ case but the last, where two expected a render and all three accepted the refusa
 
 Goal 5.2 overrides its shared draw beneath a selection and its refusal of an unnamed read; `todo.md` item 4 replaces them.
 
+## `..` steps up to the parent row, and a step down after it draws once per draw group or pick
+
+2026-10-05, larv-review on `todo.md` item 2. Goal 5.4 has `..` go up one level, and goal 5.2
+has each `{…}` make a new pick, which `todo.md` item 4 brings to every path.
+
+- `..` names the parent table next, `city..country`, as a folder path names the folder it
+  enters. `.country` after a row stays the link column's cell.
+- A step down after a `..` draws afresh inside the row stepped up to (`drawSteps`), and the
+  draw fences leave it out (`tableReadOf`), since it pins none of the render's rows. Paths
+  stepping down from one `..` share that draw through their memo (`drawMemo.stepDownPins`),
+  as reference paths share a draw today, so two reads of one step down describe one row.
+- A route through another row is another path to the same data, not a second spelling:
+  `city[Oslo]..country.name` and `country[NO].name` both load.
+
+Valid until item 4 makes every `{…}` draw afresh, which revises the shared step down.
+
 ## A table selects by one key column, a code, never a free-form name
 
 Decided 2026-09-27 by the maintainer, for goal 5's one spelling per result; valid while

draws.go

@@ -4,12 +4,30 @@ import "strings"
 
 // drawMemo is what a hold, a draw group or a named pick has drawn: the variant each level was
 // drawn as, so every path under it reads one variant; the value each read produced, by its path,
-// so the same read written twice reads one value; and the frames a read opens for the name
+// so the same read written twice reads one value; the frames a read opens for the name
-// scopes around where it lands (enter).
+// scopes around where it lands (enter); and the rows drawn below each step up stepped down from.
 type drawMemo struct {
 	variant       map[string]node
 	value         map[string]readValue
 	enteredFrames map[*nameScope]*pickFrame
+	steppedDown   map[string]*pinSet
+}
+
+// stepDownPins is the pins a path steps down into after stepping up to t, at the level at: kept
+// in m where there is one, so every path stepping down there reads one draw.
+func (m *drawMemo) stepDownPins(pins *pinSet, t *table, levels []string, at int) *pinSet {
+	if m == nil {
+		return pins.above(t)
+	}
+	p, ok := m.steppedDown[levels[at]]
+	if !ok {
+		p = pins.above(t)
+		if m.steppedDown == nil {
+			m.steppedDown = map[string]*pinSet{}
+		}
+		m.steppedDown[levels[at]] = p
+	}
+	return p
 }
 
 // groupDraws is what one render's draw group has drawn for its reference paths: a memo, and the

path.go

@@ -155,9 +155,9 @@ func stepInto(n node, seg string) (node, error) {
 		return nil, fmt.Errorf("%s is not a table, so it has no row to select", selectorOf(seg))
 	case seg == "..":
 		if c, ok := n.(*tableColumn); ok {
-			return nil, fmt.Errorf(`".." steps up from a table's row, and %q is a column`, c.t.header[c.i])
+			return nil, fmt.Errorf(`".." steps up from a table's row, and %q is a column; put the ".." right after the row`, c.t.header[c.i])
 		}
-		return nil, fmt.Errorf(`".." steps up from a table's row to the row it links to, and what it follows is not a table`)
+		return nil, fmt.Errorf(`".." steps up from a table's row to the row it links to, and what it follows is not a table; step up only from a table`)
 	}
 	switch n := n.(type) {
 	case *folder:
@@ -233,7 +233,7 @@ func (t *table) stepUp(rest []string) error {
 	case len(rest) == 0 || rest[0] != t.parentT.segment:
 		return fmt.Errorf(`".." steps up from %s to its parent table, so name that next: ..%s`, t.segment, t.parentT.segment)
 	case hasSelector(rest):
-		return fmt.Errorf(`a path selects its rows before a "..", since a row selected after it could lie outside the row it steps up to; start a path at the table to select from it`)
+		return fmt.Errorf(`a path selects its rows before a "..", since a row selected after it could lie outside the row it steps up to; select from the table instead: %s`, joinSegments(append([]string{t.parentT.path}, rest[1:]...)))
 	}
 	return nil
 }
@@ -423,7 +423,7 @@ func probePath(n node, tail []string, steps []pathStep) ([]pathStep, error) {
 // pins is nil for a sibling path, which never crosses a table, since a table is only a category.
 // For a memoized read, memo keeps the variant drawn at each of levels, so paths sharing a prefix
 // share it. It returns the leaf and the pins its row is in: a step down after a step up draws
-// afresh, into pins of its own.
+// afresh, into pins of its own, which memo shares with every path stepping down there.
 func drawSteps(s *generatorState, n node, steps []pathStep, pins *pinSet, memo *drawMemo, levels []string) (node, *pinSet) {
 	var climbed *table
 	for _, st := range steps {
@@ -445,7 +445,7 @@ func drawSteps(s *generatorState, n node, steps []pathStep, pins *pinSet, memo *
 		case st.kind == stepParent:
 			climbed = t.parentT
 		case st.kind == stepChild && climbed != nil:
-			pins, climbed = pins.above(climbed), nil
+			pins, climbed = memo.stepDownPins(pins, climbed, levels, st.at), nil
 		}
 		n = t.drawStep(s, st, pins)
 	}

reads.go

@@ -230,7 +230,7 @@ func (r readRoute) spelled(ref string) string {
 type tableRead struct {
 	headTable *table
 	pins      pinSet
-	leafPins  *pinSet // the rows the leaf renders in: pins, short of the rows below a step up
+	leafPins  *pinSet // the rows the leaf renders in: pins, short of the rows a step down after a step up draws afresh
 	drawn     map[*table]bool
 	sels      []tableSel
 	landsRow  bool
@@ -253,27 +253,29 @@ func tableReadOf(head node, a arm, leaf node) *tableRead {
 	r := &tableRead{headTable: t}
 	r.leafPins = &r.pins
 	_, r.landsRow = leaf.(*tableRow)
-	climbed := false
+	var climbed *table
 	for _, st := range a.steps {
-		if climbed && st.kind != stepChild && st.kind != stepParent {
-			continue
-		}
 		switch st.kind {
 		case stepParent:
-			t, climbed = t.parentT, true
+			t, climbed = t.parentT, t.parentT
-			r.leafPins = r.leafPins.above(t)
+		case stepChild:
+			if climbed != nil {
+				r.leafPins, climbed = r.leafPins.above(climbed), nil
+			}
+			t = t.descendant(st.name)
 		case stepSelect:
 			r.pins.pin(t, st.row)
 			r.sels = append(r.sels, tableSel{t, joinSegments(append([]string{a.writtenHead}, a.tail[:st.at+1]...))})
 		case stepDraw:
+			if r.leafPins != &r.pins {
+				continue // a step down after a step up draws apart from the render's pins
+			}
 			if r.drawn == nil {
 				r.drawn = map[*table]bool{}
 			}
 			for d, stop := t, r.pins.nearestPinned(t); d != stop; d = d.parentT {
 				r.drawn[d] = true
 			}
-		case stepChild:
-			t = t.descendant(st.name)
 		}
 	}
 	return r

record.go

@@ -152,15 +152,17 @@ func (f *Generator) FakeRecord(path string) (*Record, error) {
 }
 
 // tableRecord walks a path's tail from a table to the table whose row is the record,
-// pinning the rows it selects or draws.
+// pinning in sc the rows it selects or draws.
 func tableRecord(s *generatorState, t *table, tail []string, sc renderScope) (node, error) {
-	n, err := descend(s, t, tail, sc)
+	n, pins, err := descend(s, t, tail)
 	if err != nil {
 		return nil, err
 	}
+	group := sc.groupDraws()
+	group.pins = pins
 	switch n := n.(type) {
 	case *table:
-		n.drawIn(s, &sc.groupDraws().pins)
+		n.drawIn(s, &group.pins)
 		return n, nil
 	case *tableRow:
 		return n.t, nil

render.go

@@ -27,7 +27,7 @@ func (f *Generator) Fake(path string) (string, error) {
 	f.loadShippedAt(segments)
 	var draws renderDraws
 	sc := renderScope{draws: &draws}
-	n, err := descend(f.rand, &f.root, segments, sc)
+	n, pins, err := descend(f.rand, &f.root, segments)
 	if err != nil {
 		return "", fmt.Errorf("fejkdata: %s: %w", path, err)
 	}
@@ -35,25 +35,22 @@ func (f *Generator) Fake(path string) (string, error) {
 		return "", fmt.Errorf("fejkdata: %s names a folder, not a value", path)
 	}
 	group := sc.groupDraws()
+	group.pins = pins
 	sc, _ = sc.at(n, &group.pins).enter(n, &group.memo)
 	return render(f.rand, n, sc), nil
 }
 
-// descend walks a caller's path to the node it names, pinning in sc the rows it
+// descend walks a caller's path to the node it names, returning the rows its leaf renders in.
-// selects or draws.
+func descend(s *generatorState, root node, segments []string) (node, pinSet, error) {
-func descend(s *generatorState, root node, segments []string, sc renderScope) (node, error) {
 	// docs/decisions.md#a-path-is-walked-once-without-drawing-before-it-is-walked-for-real
 	var buf [16]pathStep
 	steps, err := probePath(root, segments, buf[:0])
 	if err != nil {
-		return nil, err
+		return nil, pinSet{}, err
 	}
-	group := sc.groupDraws()
+	var pins pinSet
-	n, pins := drawSteps(s, root, steps, &group.pins, nil, nil)
+	n, leafPins := drawSteps(s, root, steps, &pins, nil, nil)
-	// A caller's path is its render's first draw, so the rows a step down after a step up drew
+	return n, *leafPins, nil
-	// are all the render pins.
-	group.pins = *pins
-	return n, nil
 }
 
 // renderOnce renders n as one render, over draws of its own.

table_test.go

@@ -237,11 +237,13 @@ func TestTableDescendsToALinkedTable(t *testing.T) {
 
 func TestTableStepsUpToTheRowItLinksTo(t *testing.T) {
 	files := with(geo(), map[string]string{
-		"drawn.json":      `"{/locality.code}|{/locality..municipality.code}|{/locality..municipality..region.code}"`,
+		"drawn.json":       `"{/locality.code}|{/locality..municipality.code}|{/locality..municipality..region.code}"`,
-		"named.json":      `"{/locality as l}{l.code}|{l..municipality.code}|{l..municipality..region.code}"`,
+		"named.json":       `"{/locality as l}{l.code}|{l..municipality.code}|{l..municipality..region.code}"`,
-		"down.json":       `"{/locality.code}|{/locality..municipality.locality.code}"`,
+		"down.json":        `"{/locality.code}|{/locality..municipality.locality.code}"`,
-		"named-down.json": `"{/locality as l}{l.code}|{l..municipality.locality.code}"`,
+		"named-down.json":  `"{/locality as l}{l.code}|{l..municipality.locality.code}"`,
-		"record.json":     `{"format":"","l":"{/locality.code}","m":"{/locality..municipality.code}"}`,
+		"twice.json":       `"{/locality..municipality.locality.code}|{/locality..municipality.locality.name}"`,
+		"named-twice.json": `"{/locality as l}{l..municipality.locality.code}|{l..municipality.locality.name}"`,
+		"record.json":      `{"format":"","l":"{/locality.code}","m":"{/locality..municipality.code}"}`,
 	})
 	f := newGenerator(t, writeFiles(t, files), WithSeed(4))
 	for path, want := range map[string]string{
@@ -259,6 +261,7 @@ func TestTableStepsUpToTheRowItLinksTo(t *testing.T) {
 	if got := fakeTemplate(t, f, "{/locality[L4]..municipality.name}"); got != "Lund" {
 		t.Errorf("{/locality[L4]..municipality.name} = %q, want Lund", got)
 	}
+	names := map[string]string{"L1": "Stockholm", "L2": "Solna", "L3": "Malmö", "L4": "Lund", "L5": "Göteborg", "L6": "Hisingen", "L7": "Sandby", "L8": "Sandby"}
 	afresh := map[string]bool{}
 	for i := 0; i < 200; i++ {
 		for _, path := range []string{"drawn", "named"} {
@@ -281,6 +284,12 @@ func TestTableStepsUpToTheRowItLinksTo(t *testing.T) {
 				t.Fatalf("%s = %v, want a locality of the first one's municipality", path, parts)
 			}
 		}
+		for _, path := range []string{"twice", "named-twice"} {
+			parts := strings.Split(fake(t, f, path), "|")
+			if names[parts[0]] != parts[1] {
+				t.Fatalf("%s = %v, want both reads of one step down to read one locality", path, parts)
+			}
+		}
 		down, err := f.FakeRecord("locality[L4]..municipality.locality")
 		if err != nil {
 			t.Fatal(err)
@@ -313,7 +322,7 @@ func TestTableStepUpRefusals(t *testing.T) {
 		"locality[L4]..region.name":        "..municipality",
 		"region[12]..municipality.name":    "no parent",
 		"locality[L4]..":                   "..municipality",
-		"locality[L4]..municipality[0180]": "selects its rows before",
+		"locality[L4]..municipality[0180]": "municipality[0180]",
 		"locality[L4].name..municipality":  "column",
 		"x..y":                             "not a table",
 	} {