How this works

One rule, written once. Four real tools, rebuilt live.

The card below is not a mock-up. It is a very small Effortless project running in this page: one rulebook with one rule, Leases.LateFee. Move a slider and the rule changes, the rulebook gets a new hash, and the real effortless tools rebuild the Postgres function, the TypeScript, the Excel formula and the English sentence from it. Change a lease and nothing leaves your browser: the generated TypeScript recomputes that one row.

Leases › LateFeerulebook 4e2c…d89bstable hash

=IF({{DaysLate}} > 5, {{MonthlyRent}} * 0.08, 0)

Grace 5 daysLate fee 8%

Postgres

SELECT (CASE WHEN COALESCE(((SELECT days_late FROM leases WHERE lease_id = p_lease_id))::NUMERIC, 0) > 5 THEN ((COALESCE((SELECT CASE WHEN v::text ~ '^-?[0-9]*\.?[0-9]+$' THEN v::numeric ELSE NULL END FROM (SELECT ((SELECT monthly_rent FROM leases WHERE lease_id = p_lease_id)) AS v OFFSET 0) __safe_numeric), 0) * COALESCE(0.08, 0)))::text ELSE (0)::text END)::numeric;

TypeScript

toFloatPtr(erbIf(erbBool3(erbCmp(erbNullif(vIntPlain(tc.days_late)), ">", vI(5))), () => erbMul(vNumPlain(tc.monthly_rent), vF(0.08)), () => vI(0)))

ExcelIF(((D2 > 5)=TRUE), C2 * 0.08, 0)

EnglishDetermined by priority: the monthly rent times 0.08 if the days late is greater than 5; in all other cases, 0.

LeaseRentDays lateLate fee

Unit 2B$1,850.005$0.00

Unit 4A$2,400.009$192.00

Unit 7C$1,200.0013$96.00

Postgres, TypeScript, Excel and English agree✓ All 4 agree

The film

Drop your rulebook here

The longer version, with the whole loop from a rulebook to a running project. A film made from this widget is coming; until then, this one.

In plain language

What moves, and what does not

A slider changes the rule

Each slider points at one number in the formula: “Grace period” is number #1, “Late fee rate” is #2. On release the number is rewritten, the schema hashes differently, and every tool line goes from rebuilding… to the tool’s real output as each one finishes. rulebook-to-typescript runs first, because what it generates is what computes the fees.

A stepper changes data

The rulebook hash covers names, types, formulas and relationships, never a data row. So −/+ on a lease leaves the hash alone, calls no server, and the generated TypeScript recomputes that one lease in a Web Worker. The box stays green.

Every line is a receipt

Hover a line: the rulebook hash it was built from, the tool and its version, and the package hash of everything the tool produced. Nothing on the card is typed in by hand; what you read is what the tool wrote.

Export, edit, drop it back

Export to Excel, change the formula in the LateFee column, drop the workbook on the card. xlsx-to-rulebook patches the rulebook with Excel’s spelling of the formula, and all four lines rebuild from it, English included.

Reset

Back to the rulebook the site shipped with, rules and data, and to the outputs built when the site was published. The hash returns to the stable value 4e2c…d89b and the box turns green. No network.

Three languages

Every word on the card is a row in the rulebook’s WidgetTexts table, in English, Español, Deutsch. Switching language changes rows, not code.

Deep dive

The widget is a rulebook

The React component is a generic renderer of a contract, and the contract lives in the same rulebook as the domain. The Leases table is the data; the Widget* tables say which fields bind to which column, which numbers the sliders own, which tools run, and what every label says. Adding a tool is a row, not a release.

The tables, live

Leases5 fields · 3 rowsThe domain. Three leases, one rule: a late fee when the rent is more than a few days late.

LeaseIdraw string · key

Nameraw stringThe unit, as the tenant knows it.

MonthlyRentraw numberRent due each month, in dollars.

DaysLateraw integerHow many days past the due date the rent arrived.

LateFeecalculated numberThe rule. Nothing after the grace period costs nothing; after it, a share of the rent.=IF({{DaysLate}} > 5, {{MonthlyRent}} * 0.08, 0)

LeaseId	Name	MonthlyRent	DaysLate	LateFee
unit-2b	Unit 2B	1850	5	—
unit-4a	Unit 4A	2400	9	—
unit-7c	Unit 7C	1200	13	—

WidgetFields12 fields · 4 rowsWhich domain fields the widget binds to, and how. A row here is a column in the data table.

WidgetFieldIdraw string · key

Nameraw string

TableNameraw string

FieldNameraw string

Roleraw stringrow-label · money · stepper · result

RequiredTyperaw stringraw or calculated: what the contract check demands of the field.

RequiredDatatyperaw string

Minraw number

Maxraw number

Stepraw number

HeaderTextKeyraw string

SortOrderraw integer

WidgetFieldId	Name	TableName	FieldName	Role	RequiredType	RequiredDatatype	Min	Max	Step	HeaderTextKey	SortOrder
lease	Lease	Leases	Name	row-label	raw	string	—	—	—	col.lease	1
rent	Rent	Leases	MonthlyRent	money	raw	number	—	—	—	col.rent	2
days	Days late	Leases	DaysLate	stepper	raw	integer	0	30	1	col.days	3
fee	Late fee	Leases	LateFee	result	calculated	number	—	—	—	col.fee	4

WidgetSliders13 fields · 2 rowsThe rule sliders. Each points at one number inside one formula and rewrites it.

WidgetSliderIdraw string · key

Nameraw string

TableNameraw string

FieldNameraw string

LiteralIndexraw integerWhich numeric literal in the formula, counting from 1, outside {{refs}} and quotes.

Minraw number

Maxraw number

Stepraw number

DisplayScaleraw number100 shows 0.08 as 8.

LabelTextKeyraw string

UnitTextKeyraw string

DefaultValueraw number

SortOrderraw integer

WidgetSliderId	Name	TableName	FieldName	LiteralIndex	Min	Max	Step	DisplayScale	LabelTextKey	UnitTextKey	DefaultValue	SortOrder
grace	Grace period	Leases	LateFee	1	0	15	1	1	slider.grace	unit.days	5	1
rate	Late fee rate	Leases	LateFee	2	0.01	0.15	0.01	100	slider.rate	unit.percent	0.08	2

WidgetTools15 fields · 11 rowsEvery tool or converter the widget runs. A row here is a line in the widget, an export button, or a drop-box format. No code change needed.

WidgetToolIdraw string · key

Nameraw stringrunner/tool-name, unique.

ToolNameraw string

Runnerraw stringserver = the effortless CLI through /api/live-rulebook · browser = a converter registered in converters/

InverseToolNameraw stringThe tool that turns this format back into a rulebook, if any.

Priorityraw integerLower runs first. rulebook-to-typescript is 1: it computes the numbers.

Roleraw stringComma list of compile · compute · show · export · provenance

Extractorraw stringts-calc-function · sql-calc-function · xlsx-formula · rulespeak-definition · files

Languageraw stringHow the shown line is coloured: sql · ts · excel · prose

LabelTextKeyraw string

ExportTextKeyraw string

ExportFilePatternraw string

AcceptsExtensionsraw string

IsEnabledraw boolean

SortOrderraw integer

WidgetToolId	Name	ToolName	Runner	InverseToolName	Priority	Role	Extractor	Language	LabelTextKey	ExportTextKey	ExportFilePattern	AcceptsExtensions	IsEnabled	SortOrder
compile	server/compile-rulebook	compile-rulebook	server	—	0	compile	files	—	—	—	—	—	true	0
postgres	server/rulebook-to-postgres	rulebook-to-postgres	server	—	2	show	sql-calc-function	sql	tool.postgres	—	—	—	true	1
typescript	server/rulebook-to-typescript	rulebook-to-typescript	server	—	1	compute,show,export	ts-calc-function	ts	tool.typescript	export.typescript	{name}-typescript.zip	—	true	2
excel	server/rulebook-to-xlsx	rulebook-to-xlsx	server	xlsx-to-rulebook	2	show,export	xlsx-formula	excel	tool.excel	export.excel	{name}.xlsx	.xlsx	true	3
english	server/rulebook-to-rulespeak	rulebook-to-rulespeak	server	—	2	show	rulespeak-definition	prose	tool.english	—	—	—	true	4
explainer	server/rulebook-to-explainer-dag	rulebook-to-explainer-dag	server	—	3	provenance	files	—	—	—	—	—	true	5
markdown	server/rulebook-to-markdown	rulebook-to-markdown	server	—	3	export	files	—	—	export.markdown	{name}.md	—	true	6
yaml	browser/rulebook-to-yaml	rulebook-to-yaml	browser	yaml-to-rulebook	3	export	files	—	—	export.yaml	{name}.rulebook.yaml	.yaml,.yml	true	7
xml	browser/rulebook-to-xml	rulebook-to-xml	browser	xml-to-rulebook	3	export	files	—	—	export.xml	{name}.rulebook.xml	.xml	true	8
toml	browser/rulebook-to-toml	rulebook-to-toml	browser	toml-to-rulebook	3	export	files	—	—	export.toml	{name}.rulebook.toml	.toml	true	9
csv	browser/rulebook-to-csv	rulebook-to-csv	browser	—	3	export	files	—	—	export.csv	{name}-csv.zip	—	true	10

WidgetTexts5 fields · 288 rowsEvery word the widget shows, in every language it offers. Placeholders look like {this}.

WidgetTextIdraw string · key

Nameraw string

TextKeyraw string

Localeraw string

Textraw string

WidgetTextId	Name	TextKey	Locale	Text
hash.label:en	hash.label:en	hash.label	en	rulebook
hash.label:es	hash.label:es	hash.label	es	rulebook
hash.label:de	hash.label:de	hash.label	de	Rulebook
hash.stable:en	hash.stable:en	hash.stable	en	stable hash
hash.stable:es	hash.stable:es	hash.stable	es	hash estable
hash.stable:de	hash.stable:de	hash.stable	de	stabiler Hash
hash.changed:en	hash.changed:en	hash.changed	en	new hash
hash.changed:es	hash.changed:es	hash.changed	es	hash nuevo
hash.changed:de	hash.changed:de	hash.changed	de	neuer Hash
slider.grace:en	slider.grace:en	slider.grace	en	Grace
slider.grace:es	slider.grace:es	slider.grace	es	Gracia
slider.grace:de	slider.grace:de	slider.grace	de	Karenz
slider.rate:en	slider.rate:en	slider.rate	en	Late fee
slider.rate:es	slider.rate:es	slider.rate	es	Recargo
slider.rate:de	slider.rate:de	slider.rate	de	Säumnisgebühr
unit.days:en	unit.days:en	unit.days	en	{v} days
unit.days:es	unit.days:es	unit.days	es	{v} días
unit.days:de	unit.days:de	unit.days	de	{v} Tage
unit.percent:en	unit.percent:en	unit.percent	en	{v}%
unit.percent:es	unit.percent:es	unit.percent	es	{v} %
unit.percent:de	unit.percent:de	unit.percent	de	{v} %
tool.postgres:en	tool.postgres:en	tool.postgres	en	Postgres
tool.postgres:es	tool.postgres:es	tool.postgres	es	Postgres
tool.postgres:de	tool.postgres:de	tool.postgres	de	Postgres
tool.typescript:en	tool.typescript:en	tool.typescript	en	TypeScript
tool.typescript:es	tool.typescript:es	tool.typescript	es	TypeScript
tool.typescript:de	tool.typescript:de	tool.typescript	de	TypeScript
tool.excel:en	tool.excel:en	tool.excel	en	Excel
tool.excel:es	tool.excel:es	tool.excel	es	Excel
tool.excel:de	tool.excel:de	tool.excel	de	Excel
tool.english:en	tool.english:en	tool.english	en	English
tool.english:es	tool.english:es	tool.english	es	Inglés
tool.english:de	tool.english:de	tool.english	de	Englisch
col.lease:en	col.lease:en	col.lease	en	Lease
col.lease:es	col.lease:es	col.lease	es	Contrato
col.lease:de	col.lease:de	col.lease	de	Mietvertrag
col.rent:en	col.rent:en	col.rent	en	Rent
col.rent:es	col.rent:es	col.rent	es	Renta
col.rent:de	col.rent:de	col.rent	de	Miete
col.days:en	col.days:en	col.days	en	Days late

… and 248 more rows

WidgetLocales5 fields · 3 rowsThe languages the widget offers.

WidgetLocaleIdraw string · key

Nameraw string

Coderaw string

IsDefaultraw boolean

SortOrderraw integer

WidgetLocaleId	Name	Code	IsDefault	SortOrder
en	English	en	true	1
es	Español	es	false	2
de	Deutsch	de	false	3

WidgetSettings6 fields · 1 rowsSingle values. The stable hash is a row, so recording it does not move the hash.

WidgetSettingIdraw string · key

Nameraw string

StableRulebookHashraw stringSHA-256 of the schema of the 5-day / 8% rulebook. Green when the live hash equals it.

DefaultLocaleraw string

PrimaryResultFieldraw stringTable.Field the widget is about.

WorkerTimeoutSecondsraw integerHow long generated code may run before the worker is killed.

WidgetSettingId	Name	StableRulebookHash	DefaultLocale	PrimaryResultField	WorkerTimeoutSeconds
default	default	4e2ce86326020cda2706f5f7b3fe199968a8f9ace6dbefdc2d55b656923cd89b	en	Leases.LateFee	5

7 tables · 61 fields · 312 rows, read from the bundled late-fee.rulebook.json.

Three hashes, three proofs

Rulebook hash

SHA-256 of the canonical JSON of every table with data removed: sorted keys, no whitespace. It proves the rule is the same. The stable value is a row in WidgetSettings, so recording it cannot move it.

4e2ce86326020cda2706f5f7b3fe199968a8f9ace6dbefdc2d55b656923cd89b

Content hash

The same hash with the rows kept. It proves the data is the same too, and is only used as the cache key for exports, which carry the rows.

9ef8a01bf201712c01a446114f9b89f1b46ffacf9e09a550e19c902ef0e8c813

Package hash

SHA-256 over the sorted list of (path, sha256 of contents) for everything a tool produced. It proves the output is the same, whichever runner made it. A browser converter computes the identical shape over its bytes.

3e5655c5abf56c484ccbf531f5a761ea9f8ef522c84b5d489da20ce2f2ed657b

What shipped with this page

Line	Tool	Version	Package hash	Extractor
Postgres	rulebook-to-postgres	v2026.10.05.0056	3e56…657b	sql-calc-function
TypeScript	rulebook-to-typescript	v2026.09.14.2224	ba8b…475e	ts-calc-function
Excel	rulebook-to-xlsx	v2026.09.17.1646	c5f2…8517	xlsx-formula
English	rulebook-to-rulespeak	v2026.10.05.1648	6d92…20af	rulespeak-definition

Built 2026-10-05 from rulebook 4e2c…d89b by the same extractors the server runs, so the first paint needs no server and Reset is instant.

Two jobs

The server runs real transpiles. Nothing else.

POST /api/live-rulebook/transpile takes a tool name and a rulebook, runs the effortless CLI in a temp project (anonymously; the server holds no account key), computes the package hash, pulls out the one line the widget shows, and deletes the temp project. POST /api/live-rulebook/import does the same for a dropped workbook. A cold tool takes half a minute to wake; the card says so.

The browser does everything else.

Hashing with crypto.subtle, caching by tool@hash in memory and localStorage, one request in flight per tool with the newest replacing a queued one, latest-wins when results arrive out of order, running generated code in a Web Worker, and the converters: rulebook-to-yaml, rulebook-to-xml, rulebook-to-toml, rulebook-to-csv run here, with no server call. The explainer DAG from rulebook-to-explainer-dag drives the derivation panel.

A dropped rulebook, one stage at a time

1
Read
JSON, YAML, XML or TOML is parsed in the browser. A parse error names the line and column.
2
Import
An .xlsx goes to the server once, where xlsx-to-rulebook patches the current rulebook with the workbook's formulas and reports what changed.
3
Contract
Does this rulebook fit the widget? Every missing table, wrong type, short formula and missing text is listed. You can cancel or use it anyway.
4
Compile
compile-rulebook recomputes every calculated value as a set. A formula that does not compile is reported by field and formula.
5
TypeScript build
rulebook-to-typescript runs; the generated files are transformed in a Web Worker. A transform error names the file and line.
6
Run
The generated code computes every row in the worker, under a timeout. Per-field errors come back on the row; an infinite loop is killed.

Each stage reports its own failure, in the words of the tool that failed. Only after all six does the new rulebook replace the current one and the other lines rebuild from it. Exports today: TypeScript, Excel, Markdown, YAML, XML, TOML, CSV, plus the rulebook itself.

Why a new tool is a row

A WidgetTools row names a tool, a runner, an extractor and a text key. Add one for any rulebook-to-xyz in the catalog and the widget grows a line, an export button, or a drop-box format, with no change to the component. The contract-in-the-rulebook is the point of the whole method, shown on the method’s own home page. Back to the widget →