# colitur — working context for Claude

Read this first, then skim the two authoritative docs it points to. This file
orients a fresh session; the specs hold the exhaustive detail.

## What colitur is

*computus liturgicus* + Latin `colitur` ("He is worshipped"). A **safe,
highly-tested, deterministic OCaml engine** that computes and validates
**liturgical calendars** for multiple rites and emits universal, template-driven
output. It computes the **day identity** (season, week, cycle, observed
celebration with rank/colour/flags, commemorations, transfers) and the day's
**reading citations** (references like `Jn 3:16`, never Bible text), correct all
the way to year **9999**.

Starts with the Roman **EF (1962)** and **OF** forms; the architecture generalizes
to any deterministic rite (Byzantine, Ambrosian, pre-Trent) as future modules.

**Sibling projects** (same author, `~/git/projects/`): **lectio** (Go; the shipped
OF+EF readings engine, 0-error vs references 2005–2050 — colitur bootstraps its
data from lectio and uses lectio as a differential oracle), **dlectio** (offline
Android app over lectio), **clectio** (tiny C build). colitur is a **standalone**
tool, not part of lectio.

## The authoritative docs (read these)

- **Design:** `docs/superpowers/specs/2026-07-30-colitur-design.md` — the full,
  approved design (scope, kernel+rites+overlays architecture, data model, output,
  the 5 validation layers, phasing, success criteria). **This is the contract.**
- **Rules register:** `docs/research/rules-register.md` — every temporal/precedence
  rule the engine computes against, each citing its normative paragraph. The **EF
  rubrics are primary-source-verified** against the 1962 Missal (RG 91 Table of
  Precedence full 28 entries, occurrence RG 92–95, commemorations RG 108–111,
  vigils/octaves/Rogations/Sunday-classes, seasons RG 71–77). OF side cites UNLYC.
- **Plans:** `docs/superpowers/plans/` — `…-plan1-computus-skeleton.md` (done).
- **Primary scans:** `docs/research/*.pdf` — the 1962 Missale Romanum (Latin) and
  the *Rubricarum instructum* motu proprio. `docs/` is **gitignored** (research +
  copyrighted scans stay off the public repo).

## Binding decisions (do not relitigate)

1. **Source of truth = the 1962 Missale Romanum + its Rubricae Generales.**
   Divinum Officium, missalemeum, gcatholic are **comparison oracles only** — any
   **divergence from a reference is flagged LOUDLY** in validation, never silently
   swallowed.
2. **Scope is strictly the 1962 Missal** (1960 rubrics + 1955 Holy Week). Every
   addition (2020 *Quo Magis*/*Cum Sanctissima*, any community's proper) is an
   **overlay**, never core.
3. **Data is bootstrapped from lectio** (0-error vs missalemeum), then validated by
   **rigorous property + differential testing over a large RANDOM sample across the
   whole 1583–9999 range** — not only 2005–2050.
4. **EF and OF are peer rite modules** — a form is never an overlay of another form.
   Each has its own `temporal` + `precedence` **code** and its own **data**; they
   share only the kernel.
5. **Build EF end-to-end first** as the pilot vertical slice (it is the harder,
   more idiosyncratic form, and its rules are already fully researched), learn from
   it, *then* add OF as the second module to prove the `RITE` abstraction generalizes.

## Architecture (one screen)

Rite-agnostic **kernel** + **rite modules** (plug in via a signature) + **data
overlays**.

- **Kernel** (`lib/kernel`, pure, total, bounded 1583–9999): `Computus` (Gregorian
  + Julian Easter + anchors), `Date` (proleptic Gregorian arithmetic), `Overlay`
  (ordered layer-merge algebra: field-level add/suppress/replace/edit, last-writer-
  wins, `empty` = identity), `Precedence` (general resolver parameterized by a
  rite's ruleset → observed day + commemorations + transfers; deterministic,
  terminating), `Calendar` (orchestrator), `Validate` (the invariant/property harness).
- **Rite module** (`lib/rites/<rite>`) satisfies:
  ```ocaml
  module type RITE = sig
    val id         : string
    val temporal   : Date.t -> Temporal.t   (* season, week, cycle, movable feasts — CODE  *)
    val precedence : Precedence.rules        (* rite ranking + resolution          — CODE  *)
    val sanctoral  : Calendar.layer          (* fixed-date base calendar           — DATA  *)
    val lectionary : Lectionary.t            (* slug/day → citations               — DATA  *)
  end
  ```
  Temporal + precedence are **code** (auditable, property-tested); sanctoral +
  lectionary are **data** (`.sexp`, bootstrapped from lectio). `Rite_ef` then `Rite_of`.
- **Result type** `LiturgicalDay` = { date; rite; season; week/cycle; observed
  (slug, names, rank, colour, flags); commemorations; transfer; citations } — the
  single stable schema for all output.
- **Output**: one schema → CSV / JSON / S-expression, rendered by a **logic-less
  Mustache-family template engine** (user supplies the target-language template;
  the engine never executes code). Unix-composable CLIs: `compute | render`, `table`.
- **Data format**: **S-expressions** (`sexplib`/`ppx_sexp_conv`) — the OCaml type
  *is* the format, parse/print auto-derived, no hand-written parser.

## Validation (the "sure bet" pillar — 5 layers)

1. **Types** — illegal states unrepresentable (closed variants for ranks/colours/
   seasons; dates validated at construction; resolution total).
2. **Property (QCheck), year-independent** — hold for every year 1583–9999: exactly
   one observed day per date; year covered once, no gaps; seasons contiguous; Easter
   a Sunday in [Mar 22, Apr 25]; movable feasts at correct Easter-offset weekday;
   overlay merge deterministic + `empty` identity; sexp round-trips. **This is how
   confidence extends past the oracle horizon (~2050).**
3. **Differential vs lectio** — every day 2005–2050 agrees (season, rank, observed,
   citations).
4. **Oracle cross-check** — vs missalemeum (EF) / litcal (OF) in lectio's `sources/`.
5. **Golden regression** — landmark + known-tricky years pinned.

## Current state (Plan 1 DONE — verify with `git log`)

Branch **`ef-pilot-plan1`**, ~6 commits. The Computus **walking skeleton** is built
and green:
- `lib/kernel/date.ml[i]` — `Date`: opaque rata-die (Howard Hinnant civil↔days, as
  in lectio); `make ~year ~month ~day : (t,string) result` (validates, 1583..9999);
  `year/month/day/weekday/to_rata/of_rata/add_days/compare`.
- `lib/kernel/computus.ml[i]` — `gregorian_easter`, `julian_easter`, and anchors
  `ash_wednesday/palm_sunday/ascension/pentecost/corpus_christi`.
- `bin/main.ml` — CLI `colitur easter <year>` (prints Easter + anchors; bad year → exit 2).
- `test/` — alcotest unit + qcheck property + a `cli.t` cram test. All green.
- Build: dune 3.0, **OCaml 5.2.0 project-local opam switch** (`./_opam` already
  present), deps `dune alcotest qcheck qcheck-alcotest`, `cram enable`,
  `generate_opam_files`. License **AGPL-3.0-or-later**.

`sexplib`/`ppx_sexp_conv` and a Mustache lib are **not yet added** — they arrive
with the data model in Plan 2/3.

### Build & test
```sh
eval $(opam env)          # activate the project-local switch (run from this dir)
dune build
dune test
dune exec colitur -- easter 2026
```

## What's next

- **Plan 2 — kernel data model & resolution.** `LiturgicalDay` schema; `Overlay`
  (the layer-merge algebra); the `Precedence` framework (rite-parameterized
  resolver); the **EF `temporal`** (seasons per RG 71–77 incl. Septuagesima + the
  cycle); the `Validate` harness. Add `sexplib`/`ppx_sexp_conv`. Each piece
  property-tested. **Brainstorm → writing-plans → execute.**
- **Plan 3 — EF end-to-end (the pilot).** The EF rite module: `temporal` +
  `precedence` **code** from the register's RG citations (RG 91 table, occurrence
  RG 92–95, commemorations RG 108–111, transfers RG 95–102); sanctoral + lectionary
  **data** bootstrapped from lectio; **plus a minimal output path** (CSV + one
  template) so it produces a real table. Differential vs lectio + oracle vs
  missalemeum green 2005–2050; deep-tail edges checked vs the Missal PDFs.
  **Capture the lessons.**
- **Then**: OF rite module (proves `RITE` generalizes) → full output/rendering →
  hardening (property sweep to 9999, golden pins, first tag).

Still-open research residuals are listed in the register §6 (EF reading-selection
rules; Christ-the-King/Holy-Family placement; data audit) — verify-while-coding,
not blockers.

## How to work here

- **Superpowers workflow**: `brainstorming` → `writing-plans` → `executing-plans`
  or `subagent-driven-development`. Present a design and get approval before coding.
  Plans live in `docs/superpowers/plans/`, specs in `docs/superpowers/specs/`.
- **TDD**, bite-sized tasks, a commit per task on the feature branch (never straight
  to `main` without consent).
- **Every temporal/precedence rule carries a source citation** (RG/UNLYC paragraph)
  in a comment — grep-able, matching the register.
- **Kernel is total & deterministic**: no wall-clock, randomness, or environment
  reads; fallible construction returns `result`/`option`, never raises on in-range
  input; years outside 1583–9999 rejected at the boundary.
- **Commits**: conventional-commit style, subject + body only. **No AI/tool trailer
  of any kind** (the author considers them noise in a public repo).
- **License header**: files may carry a short SPDX `AGPL-3.0-or-later` line.
- `docs/` is gitignored — design/research/scans stay local; only code + README +
  LICENSE + this file are tracked.