README.md

@@ -163,7 +163,8 @@ it to a name and read the name
 The shipped data comes in modules, each a Go package under [`data/`](data) that embeds
 its files, so nothing is read from disk: one per locale (`en_US`, `sv_SE`), one per
 country's tree of places (`geo/SE`, `geo/US`), and the locale-neutral `misc`. The CLI
-carries every module, and a library loads those it imports ([Library](#library)). A
+carries every module, and a library loads those it passes to `WithDataFS`
+([Library](#library)). A
 directory is a namespace: each JSON file is a category named after the file, each
 subdirectory a dot-path segment, so `mydata/sv_SE/person.json` is `sv_SE.person` and
 replaces the shipped one. A module's tree spells its namespace the same way, so

data.go

@@ -8,30 +8,36 @@ import (
 
 // loadSources merges sources in order, the last winning a clash. A source whose manifest
 // carries an index leaves its categories unloaded; every other source loads here, with
-// the unloaded categories it needs.
+// the unloaded categories it needs: docs/decisions.md#a-source-whose-manifest-carries-an-index-loads-each-category-on-first-reach-any-other-loads-in-new-with-what-it-reads
 func loadSources(sources []datafiles.Source) (folder, error) {
 	root := folder{children: map[string]node{}}
+	defaultModules := map[string][]string{}
 	for _, src := range sources {
-		if err := addSource(&root, src); err != nil {
+		if err := addSource(&root, src, defaultModules); err != nil {
 			return folder{}, err
 		}
 	}
-	return root, loadReached(&root, categorySites(&root), nil)
+	return root, loadReached(&root, categorySites(&root), nil, defaultModules)
 }
 
-func addSource(root *folder, src datafiles.Source) error {
+// addSource places src's categories in root, and sets in defaultModules, for each category
+// it loads, the modules src reads by default.
+func addSource(root *folder, src datafiles.Source, defaultModules map[string][]string) error {
 	m, err := src.Manifest()
 	if err != nil {
 		return err
 	}
 	if m.Index != nil {
-		placeIndex(root, src, m.Index)
+		placeIndex(root, src, m)
 		return nil
 	}
 	g := &folder{children: map[string]node{}}
 	if err := src.Walk(compileInto(func(dir []string) *folder { return madeFolder(g, dir) })); err != nil {
 		return err
 	}
+	for _, s := range categorySites(g) {
+		defaultModules[s.path] = m.Reads
+	}
 	mergeFolder(root, g)
 	return nil
 }

data/modules.go

@@ -1,4 +1,5 @@
-// Package data lists every module fejkdata ships.
+// Package data lists every module fejkdata ships. A module's tree spells its namespace:
+// data/geo/SE embeds geo/SE/…, whose categories are geo.SE.*.
 package data
 
 import (

data_test.go

@@ -63,7 +63,7 @@ func TestShippedDataCategories(t *testing.T) {
 	}
 }
 
-// TestShippedMiscCategories covers the locale-neutral data/misc folder: a proper
+// TestShippedMiscCategories covers the locale-neutral misc module: a proper
 // v4 UUID (version/variant nibbles fixed), a MAC address, and credit-card numbers
 // whose trailing {luhn()} check passes.
 func TestShippedMiscCategories(t *testing.T) {
@@ -467,8 +467,8 @@ func TestShippedTableCellsAreTrimmed(t *testing.T) {
 	}
 }
 
-// TestShippedNamespacedTree loads the whole data/ tree (not a single locale) and
-// reaches each locale through its folder segment: data/sv_SE/person -> sv_SE.person.
+// TestShippedNamespacedTree loads every shipped module and reaches each locale through its
+// folder segment: data/sv_SE/sv_SE/person.json -> sv_SE.person.
 func TestShippedNamespacedTree(t *testing.T) {
 	f := shipped(t, WithSeed(1))
 	for _, path := range []string{"sv_SE.person", "en_US.person", "sv_SE.address.locality"} {

docs/comprehension-history.md

@@ -304,3 +304,29 @@ Junior A, decided by:
 - Locality, Shape: `node.go:23` `folder`: `put` and `putUnloaded` keep a name in one map, where `compileInto` and `unloadedCategory.load` kept it as a pair
 - Locality, Shape: `data.go:12` `loadSources`: one load path, where `config.load` forked and `loadShipped` was a second, panic-only pipeline
 - Shape: `data.go:81` `categorySite`: embeds `categoryAt`, where `unloadedCategory` repeated its fields
+
+## 2026-10-10T11:11:16Z, PR #203 at 421bb49, against bf1becb
+
+Ruling: worse
+
+| Seat | Navigation | Locality | Shape | Self-sufficiency | Overall |
+|---|---|---|---|---|---|
+| Mid A | same | worse | worse | same | worse |
+| Inherited architect | same | worse | worse | same | worse |
+
+Mid A, decided by:
+
+- Locality, Overall: `node.go:28` `folder.reads`: a third per-name map beside children and unloaded with no invariant tying it to them; every placement site must remember a separate setReads call (`data.go:36` addSource, `data.go:76` mergeFolder, `index.go:27` placeIndex)
+- Locality, Shape: `resolve.go:96` `withReads`: the manifest's reads travels through folder, categorySite.reads and templateSite.category to feed one error clause, four files to hold for one sentence of error text
+- Shape: `internal/datafiles/manifest.go:22` `Manifest.Reads`: reads as a load dependency the loader acts on, though it only feeds error text, and "reads" already means a template reading a name or column
+- Shape: `data/geo/SE/fs.go:2` `SE`: package names SE, US, en_US, sv_SE; in Modules SE.FS sits beside sv_SE.FS with nothing saying which is geography
+- Locality: `fejkdata.go:94` `New`: loads exactly what the options name, easier than the hidden config{shipped: true} default, though config.given brings back a smaller flag
+
+Inherited architect, decided by:
+
+- Locality, Shape, Overall: `node.go:27` `folder.reads`: a third per-name map that put and putUnloaded leave alone, so addSource, mergeFolder and placeIndex must each call setReads, and batch.load relies on placeIndex having done it; action at a distance for one error suffix
+- Locality: `resolve.go:94` `templateSite.withReads`: reads travels folder, categorySite.reads, a *categorySite per template, then withReads, four hops across three files
+- Shape: `data/geo/SE/fs.go:2` `SE`: bare package names SE and US do not say geography at WithDataFS(sv_SE.FS, SE.FS); the namespace-doubling rule lives only in README and test code
+- Shape, Self-sufficiency: `internal/datafiles/manifest.go:22` `Manifest.Reads`: suggests it drives loading though it only feeds withReads; "by default" needs README goal 9.2
+- Locality, Navigation: `data/modules.go:17` `Modules`: the hidden shippedFS default is gone; Modules lists the modules, errNoData names the fix, and the CLI loads data.Modules() in plain sight
+- Locality: `fejkdata.go:40` `config.given`: WithDataFS() with no arguments differs from no option, learnt only from its comment

docs/decisions.md

@@ -143,7 +143,7 @@ package under `data/` embeds its own files, and a library imports the packages i
 
 - One Go package per locale, one per country's `geo/` tree, and one for `misc`, all in the core's Go module. A package registers nothing when imported.
 - A bare `New()` loads no data and fails, naming the option to add. `WithoutShippedData` goes.
-- A data package's `FS` is an `fs.FS` passed to `WithDataFS`, as anyone's data is, and `New` takes several. A module carrying functions loads through an option of its own, so a data module that starts carrying functions breaks its users. Such a function reaches the randomness through an interface the root declares; `internal/drawstate`'s type stays internal.
+- A data package's `FS` is an `fs.FS` passed to `WithDataFS`, as anyone's data is, and `New` takes several. It is an exported `var FS embed.FS`, the shape `//go:embed` gives; a function returning it would guard only against a program reassigning a dependency of its own. A module carrying functions loads through an option of its own, so a data module that starts carrying functions breaks its users. Such a function reaches the randomness through an interface the root declares; `internal/drawstate`'s type stays internal.
 - A module names, in a manifest, every module it reads by default, directly or through another, so the first error names the whole set to import. A manifest is optional: a `--data-path` folder without one is a module. Nothing loads a default on its own.
 - A manifest names no fejkdata version, and `New` checks none: the shipped packages ship in the core's Go module, and a module from anyone else keeps loading across a minor or a patch, as the README's Versioning promises. The maintainer chose so on 2026-10-09.
 - In the CLI, a flag of its own says a `--data-path` replaces what it clashes with, so flags still go anywhere on the line. Data authors and hand fixture authors bench it.
@@ -582,7 +582,9 @@ when a source carries it.
 
 2026-09-24, Lilleman auf Larv; revised 2026-10-10, when the shipped data became Go packages.
 Serves goal 6.2. `sv_SE.FS` loads alone, and `sv_SE.address` then fails at first reach,
-naming `github.com/larvit/fejkdata/data/geo/SE`, which `sv_SE`'s manifest reads.
+naming `github.com/larvit/fejkdata/data/geo/SE`, which `sv_SE`'s manifest reads. `New`
+checks no `reads`: a stand-in providing the same paths under another name would fail it
+(goal 9.2).
 `--no-shipped-data -d` takes a locale's folder with its country's, or a set of one's own.
 
 ## The default embed holds every Swedish postort the import can place and give a street-delivery code and a street, and the US places of 25,000 or more

fejkdata.go

@@ -65,7 +65,7 @@ func WithDataPath(dir string) Option {
 func WithDataFS(modules ...fs.FS) Option {
 	return func(c *config) {
 		for _, fsys := range modules {
-			c.sources = append(c.sources, datafiles.FS(fsys, ""))
+			c.sources = append(c.sources, datafiles.FS(fsys))
 		}
 		c.given = true
 	}

index.go

@@ -11,10 +11,12 @@ import (
 	"github.com/larvit/fejkdata/internal/grammar"
 )
 
-// indexed is a category an index names and no call has reached yet, and the source holding it.
+// indexed is a category an index names and no call has reached yet, the source holding it,
+// and the modules that source reads by default.
 type indexed struct {
-	entry datafiles.IndexEntry
-	src   datafiles.Source
+	entry          datafiles.IndexEntry
+	src            datafiles.Source
+	defaultModules []string
 }
 
 // placeIndex sets every category m's index names as unloaded in root, in place of what
@@ -22,9 +24,7 @@ type indexed struct {
 func placeIndex(root *folder, src datafiles.Source, m datafiles.Manifest) {
 	for _, p := range sortedNames(m.Index) {
 		segs := strings.Split(p, ".")
-		g, name := madeFolder(root, segs[:len(segs)-1]), segs[len(segs)-1]
-		g.putUnloaded(name, &indexed{entry: m.Index[p], src: src})
-		g.setReads(name, m.Reads)
+		madeFolder(root, segs[:len(segs)-1]).putUnloaded(segs[len(segs)-1], &indexed{entry: m.Index[p], src: src, defaultModules: m.Reads})
 	}
 }
 
@@ -60,7 +60,7 @@ func (f *Generator) loadCallerPath(path string) (string, []string, error) {
 		return "", nil, fmt.Errorf("fejkdata: %w", err)
 	}
 	if c, ok := categoryOn(&f.root, segs); ok && c.unloaded() {
-		if err := loadReached(&f.root, nil, []categoryAt{c}); err != nil {
+		if err := loadReached(&f.root, nil, []categoryAt{c}, nil); err != nil {
 			return "", nil, fmt.Errorf("fejkdata: %w", loadError{err})
 		}
 	}
@@ -107,8 +107,9 @@ func needs(root *folder, s categorySite) []categoryAt {
 
 // loadReached loads the unloaded categories among wanted and every unloaded category they
 // or sites need, then runs sites and all it loaded through a whole load's pipeline. On an
-// error it puts back what it loaded, so the next call fails the same way.
-func loadReached(root *folder, sites []categorySite, wanted []categoryAt) error {
+// error it puts back what it loaded, so the next call fails the same way. defaultModules
+// holds, by path, the modules the source of each of sites reads by default.
+func loadReached(root *folder, sites []categorySite, wanted []categoryAt, defaultModules map[string][]string) error {
 	queue := wanted
 	for _, s := range sites {
 		queue = append(queue, needs(root, s)...)
@@ -119,6 +120,14 @@ func loadReached(root *folder, sites []categorySite, wanted []categoryAt) error
 		err = b.run(root, sites)
 	}
 	if err != nil {
+		err = withDefaultModules(err, func(category string) []string {
+			for _, l := range b {
+				if l.site.path == category {
+					return l.was.defaultModules
+				}
+			}
+			return defaultModules[category]
+		})
 		b.putBack()
 	}
 	return err
@@ -169,6 +178,19 @@ func (b batch) run(root *folder, sites []categorySite) error {
 	return categoryPipeline(sites, root.children).run()
 }
 
+// withDefaultModules adds to err, where a reference of a category names nothing, the modules
+// the category's source reads by default, or that it names none.
+func withDefaultModules(err error, of func(category string) []string) error {
+	var u unresolvedRead
+	if !errors.As(err, &u) {
+		return err
+	}
+	if modules := of(u.category); len(modules) > 0 {
+		return fmt.Errorf("%w; the module holding %s reads by default %s", err, u.category, strings.Join(modules, ", "))
+	}
+	return fmt.Errorf("%w, and the module holding %s names no module it reads by default", err, u.category)
+}
+
 func (b batch) putBack() {
 	for _, l := range b {
 		l.site.in.putUnloaded(l.site.name, l.was)

inline.go

@@ -90,7 +90,7 @@ func loadInline(root *folder, n node, label string, typedByGo bool) error {
 	if err := refuseFolderRefs(nodes); err != nil {
 		return err
 	}
-	if err := loadReached(root, nil, referenced(root, nil, nodes)); err != nil {
+	if err := loadReached(root, nil, referenced(root, nil, nodes), nil); err != nil {
 		return loadError{err}
 	}
 	return pipeline{

internal/datafiles/datafiles.go

@@ -12,13 +12,12 @@ import (
 	"github.com/larvit/fejkdata/internal/jsonvalue"
 )
 
-// Source is one tree to load: an fs.FS and the directory in it to start from. label
-// prefixes file names in errors; onDisk marks label as a directory that must exist.
+// Source is one tree to load, from the root of an fs.FS. label prefixes file names in
+// errors; onDisk marks label as a directory that must exist.
 type Source struct {
 	fsys   fs.FS
 	label  string
 	onDisk bool
-	base   string
 }
 
 // Dir is the tree in the directory path, its errors labelled with it.
@@ -26,10 +25,10 @@ func Dir(path string) Source {
 	return Source{fsys: os.DirFS(path), label: path, onDisk: true}
 }
 
-// FS is the tree in fsys below base, "" for its root.
-func FS(fsys fs.FS, base string) Source { return Source{fsys: fsys, base: base} }
+// FS is the tree in fsys.
+func FS(fsys fs.FS) Source { return Source{fsys: fsys} }
 
-// Category is one category file: the folders above it from the source's base, its name,
+// Category is one category file: the folders above it from the source's root, its name,
 // and its parsed JSON.
 type Category struct {
 	Folders []string
@@ -50,7 +49,7 @@ func (s Source) labelled(p string) string {
 
 // dirPath is the folder that dir names, as fsys spells it.
 func (s Source) dirPath(dir []string) string {
-	if p := path.Join(append([]string{s.base}, dir...)...); p != "" {
+	if p := path.Join(dir...); p != "" {
 		return p
 	}
 	return "."

internal/datafiles/manifest.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
-	"path"
 	"sort"
 	"strings"
 
@@ -19,7 +18,8 @@ const ManifestFile = ".fejkdata.json"
 type Manifest struct {
 	// Index is every category of the source by dot path; nil where the manifest has none.
 	Index map[string]IndexEntry `json:"index"`
-	// Reads is every module the source reads by default, directly or through another.
+	// Reads is every module the source reads by default, directly or through another; the
+	// error for a reference naming nothing names them, and nothing loads them.
 	Reads []string `json:"reads"`
 }
 
@@ -35,7 +35,7 @@ func (s Source) Manifest() (Manifest, error) {
 	if err := s.check(); err != nil {
 		return Manifest{}, err
 	}
-	b, err := fs.ReadFile(s.fsys, path.Join(s.base, ManifestFile))
+	b, err := fs.ReadFile(s.fsys, ManifestFile)
 	if errors.Is(err, fs.ErrNotExist) {
 		return Manifest{}, nil
 	}
@@ -50,7 +50,7 @@ func (s Source) Manifest() (Manifest, error) {
 }
 
 // ManifestPath is the manifest's path as errors name it.
-func (s Source) ManifestPath() string { return s.labelled(path.Join(s.base, ManifestFile)) }
+func (s Source) ManifestPath() string { return s.labelled(ManifestFile) }
 
 // decodeManifest decodes a manifest, refusing any key or shape it does not define, and
 // reports every mistake: first each entry's own, in path order, then each parent naming

pick.go

@@ -19,7 +19,7 @@ import (
 // the read's first-level key, put under the rendering template's key, is one of the name's
 // addressed keys. keptInPick decides this, and readUnder reads it.
 //
-// In data/geo/SE/address.json, {.locality as l} binds l, and {l.street.name} passes the levels
+// In geo.SE.address, {.locality as l} binds l, and {l.street.name} passes the levels
 // "", "street" and "street.name", the last of which is its key. With {l.name} and {l.postal-code.code},
 // l's addressed keys are those three, "name", "postal-code" and "postal-code.code". Where p
 // binds a category whose format reads {first}, and both {p} and {p.first} are read, the {first}
@@ -174,8 +174,8 @@ func (m *drawMemo) enteredFrame(scope *nameScope) *pickFrame {
 // When the pick renders another category, enter takes that category's frames from the pick's
 // memo, and renderFrame finds them and opens no new one.
 // So every read through one pick sees one pick of each name the other category binds:
-// {a.street} and {a.postal-code} in data/sv_SE/address.json read one pick of the name l
-// that data/geo/SE/address.json binds.
+// {a.street} and {a.postal-code} in sv_SE.address read one pick of the name l
+// that geo.SE.address binds.
 func readName(s *drawstate.State, env renderEnv, a arm) readValue {
 	f := env.frameOf(a.named.scope)
 	if f == nil {

resolve.go

@@ -3,18 +3,26 @@ package fejkdata
 import (
 	"errors"
 	"fmt"
-	"strings"
 )
 
-// templateSite is a template to resolve, with its folder and category, both empty for an inline
-// template, and eachNode's label for it.
+// templateSite is a template to resolve, with its folder and its category's path, both empty for an
+// inline template, and eachNode's label for it.
 type templateSite struct {
 	t        *template
 	folder   []string
 	label    string
-	category *categorySite
+	category string
 }
 
+// unresolvedRead is a reference of a category's template naming nothing.
+type unresolvedRead struct {
+	category string
+	err      error
+}
+
+func (u unresolvedRead) Error() string { return u.err.Error() }
+func (u unresolvedRead) Unwrap() error { return u.err }
+
 // resolveCategoryTemplates resolves every template of the categories, once all data is merged, so a
 // reference sees the override-resolved tree.
 func resolveCategoryTemplates(sites []categorySite, root map[string]node) error {
@@ -22,7 +30,7 @@ func resolveCategoryTemplates(sites []categorySite, root map[string]node) error
 	for _, s := range sites {
 		if err := eachNode(s.n, s.path, func(label string, n node) error {
 			if t, isTemplate := n.(*template); isTemplate {
-				ts = append(ts, templateSite{t: t, folder: s.dir, label: label, category: &s})
+				ts = append(ts, templateSite{t: t, folder: s.dir, label: label, category: s.path})
 			}
 			return nil
 		}); err != nil {
@@ -58,8 +66,12 @@ type resolvedNames struct {
 func resolveTemplates(ts []templateSite, root map[string]node) error {
 	for _, s := range ts {
 		refs, err := s.t.resolveRefs(s.folder, s.label, root)
+		var ne noEntry
+		if err != nil && s.category != "" && errors.As(err, &ne) {
+			return unresolvedRead{category: s.category, err: err}
+		}
 		if err != nil {
-			return s.withReads(err)
+			return err
 		}
 		s.t.refs = refs
 	}
@@ -90,16 +102,3 @@ func resolveTemplates(ts []templateSite, root map[string]node) error {
 	}
 	return nil
 }
-
-// withReads adds to err, where a reference of a category names nothing, the modules the
-// category's manifest names it reading by default, or that it names none.
-func (s templateSite) withReads(err error) error {
-	var ne noEntry
-	if s.category == nil || !errors.As(err, &ne) {
-		return err
-	}
-	if len(s.category.reads) == 0 {
-		return fmt.Errorf("%w, and the module holding %s names no module it reads by default", err, s.category.path)
-	}
-	return fmt.Errorf("%w; the module holding %s reads by default %s", err, s.category.path, strings.Join(s.category.reads, ", "))
-}

todo.md

@@ -6,7 +6,7 @@
 
 `Bar = 9`
 
-`Next ID = 195`
+`Next ID = 196`
 
 | Goal | W |
 |---|---|
@@ -128,6 +128,7 @@
 | 168 | 0.2.0 | principle | **Test the shared steps of `data-import/` in the merge gate, starting with `geo.fence`.** | 2 | 4 | 2 | 6 | 3 | 11.8 |
 | 161 | 0.2.0 |  | **Let a field whose name starts or ends with whitespace be bound to a name, or refuse such an identifier, so `{ x as p}` means one thing.** | 2 | 2 | 2 | 6 | 5.6, 4.1 | 11.7 |
 | 175 | 0.2.0 |  | **Rewrite the comments the 2026-10-09 panel needed several reads of, and delete those it read as restating their code.** | 1 | 2 | 1 | 6 | 3.4 | 11.3 |
+| 195 | 0.2.0 | principle | **Parse each builtin argument once, in `checkArgs`, and hand `prep` and `proveNumber` the parsed value.** | 3 | 3 | 2 | 6 | 3 | 11.1 |
 | 112 | 0.2.0 |  | **Check a calc's field operands where its template resolves, beside its name operands, once item 36 reports every mistake at once.** | 2 | 2 | 1 | 6 | 3.2 | 10.3 |
 | 172 | 0.2.0 |  | **Pass `drawSteps` the kind of read it draws as an argument of its own, so no caller signals a sibling path by a nil `pins` or a fresh read by a nil `memo`.** | 2 | 2 | 1 | 6 | 3.2 | 10.3 |
 | 173 | 0.2.0 |  | **Call what a token reads its spelling, never a name, in `format.go`, `arm.go` and `reference.go`, so a name in the engine is only a bound name.** | 2 | 3 | 1 | 6 | 3.2 | 10.1 |
@@ -181,7 +182,7 @@ Pick the ten from a published ranking of languages by total speakers, such as Et
 
 ### 185. Seat a panel of the README's audience personas to pull data in through the module API and build a custom CLI, and fix what it names.
 
-Needs item 184; 0.1.0 is not cut before it. Carries out the decision "The shipped data is Go packages a library imports by choice, and the CLI carries every one, from 0.1.0". Seats: the Go test author, the bulk fixture author, a custom CLI's builder, and a data author with a `-d` folder and the replace flag, each in a scratch Go module against the checkout or a pre-release tag. Bench the geo packages' names, `data.Modules()`, the error naming the import set, and the `.fejkdata.json` manifest a data author writes by hand. Decoding the manifest is most of `New`'s cost (about 0.55 ms and 2449 allocations on 2026-10-10). An entry lists every path below its category, its linked tables' paths too, so `geo.*.region` repeats its whole family. An entry holding only its own paths, with `List` composing a family from the entries naming it as `parent`, would shrink it. Record the ruling in `docs/`.
+Needs item 184; 0.1.0 is not cut before it. Carries out the decision "The shipped data is Go packages a library imports by choice, and the CLI carries every one, from 0.1.0". Seats: the Go test author, the bulk fixture author, a custom CLI's builder, and a data author with a `-d` folder and the replace flag, each in a scratch Go module against the checkout or a pre-release tag. Bench the geo packages' names, `data.Modules()`, the error naming the import set, and the `.fejkdata.json` manifest a data author writes by hand. Decoding the manifest is most of `New`'s cost (about 0.55 ms and 2449 allocations on 2026-10-10, 2864 allocations once each module carried its own). An entry lists every path below its category, its linked tables' paths too, so `geo.*.region` repeats its whole family. An entry holding only its own paths, with `List` composing a family from the entries naming it as `parent`, would shrink it. Record the ruling in `docs/`.
 
 ### 16. Add locale categories: company, phone, finance, vehicle, words.
 
@@ -414,7 +415,7 @@ A hyphen is always subtraction in a calc, and the shipped data has hyphenated fi
 
 ### 194. Let a data author write and check their own `.fejkdata.json` index with the library or the CLI, and fail a load whose index leaves out a category file.
 
-Goal 6.3 has an author prove their module, and goal 9.1 has fejkdata's data load as anyone's; today only fejkdata's own test, `TestShippedManifestIsCurrent` over `indexEntry`, writes and checks an index. A category file the index leaves out never loads, silently.
+Goal 6.3 has an author prove their module, and goal 9.1 has fejkdata's data load as anyone's; today only fejkdata's own test, `TestShippedManifestsAreCurrent` over `indexEntry`, writes and checks an index. A category file the index leaves out never loads, silently.
 
 ### 53. Let a table column carry a `datatype`, so `--format json` writes `"safe": true` and `--format sql` a boolean.
 
@@ -488,6 +489,10 @@ Against "Most, if not all, code should have automated tests" in `technical-princ
 
 Reread: `readField`'s note on clearing the pick (`render.go`), `pickKey.under`, which three seats read backwards, `scopeAround`'s "short of the frames n renders itself", `enter` returning `env.base` as the pop mark, and add a line at `walkEvery`'s three-index slice, which three seats found unmarked. Restating: `compileCells`, `columnOrLinked`, `render`'s first line, `categorySites`, `madeFolder`, `categoryOf`, `rendersInside`, `templateSite`, `templateOptions`, `compileFrom`, `flagArg`, `drawSeed`, the `calc` parser's precedence line in `internal/grammar`, and `compileChoice`'s note that a uniform choice draws in O(1), which `choice`'s doc already says. A doc comment `go doc` shows on an exported name stays.
 
+### 195. Parse each builtin argument once, in `checkArgs`, and hand `prep` and `proveNumber` the parsed value.
+
+Applies "Validate data and build DTOs as early as possible" in `~/.claude/principles/technical-principles.md`. Today `checkArgs` (`internal/builtinfunc/builtins.go`) checks an argument, then `prep` and `proveNumber` parse it again through `atoi`/`atof`, which panic, as do `layout.go`, `transform.go` and `calc.go`; two parsers can drift, and a drift panics at compile instead of failing the load.
+
 ### 112. Check a calc's field operands where its template resolves, beside its name operands, once item 36 reports every mistake at once.
 
 Needs item 36. `checkCalcFields` runs at compile and `checkCalcNames` in `resolveTemplates`, two passes over one rule. Moving the field check there before item 36 would change which of two mistakes in two category files a load reports, since every category compiles before any resolves.