Composition & selection

A run rarely wants "any invoice." Composition constrains what a slice may draw from — a locale, a company, a template, a capture condition — and the invoice pack resolves and validates that up front so a nonsensical corpus fails at config time, not 40 minutes into a run.

The vocabulary is the kernel's Selection; composition.py resolves it against the roster (resolve), raising UnsupportedConstraint for anything the pack can't honour.

The axes

Axis	Constrains
locales	Issuer jurisdiction (currency, tax model, language follow it).
companies	A pinned company id, or "use N" (seeded from the run id).
archetypes	Which of the 7 templates.
business_types	e.g. retail, telecom, b2b_saas, ai_platform (enums.py).
conditions	clean / light_scan / heavy_scan / handwritten.
wear	Crisp ↔ worn (a value or a range).
goods_receipt	Delivery notes with a receiver's signature.
date_range	The issue-date window.

"Use N of them" is seeded from the run id, so a resumed unit draws the same pool rather than quietly changing the corpus mid-run. Currency, tax model, and address are not separate knobs — they follow the issuer's jurisdiction, so locales: [en-GB] is how a slice asks for GBP and UK addresses.

Realism rules (validated, not silently ignored)

A slice named french that emits English is a wasted run nobody notices, so the pack refuses impossible combinations rather than dropping them:

• Handwritten always renders as the handwritten pad (handwritten-form-01) — there is no typeset handwritten archetype.
• Handwritten ≠ telecom — a 50-page hand-filled itemised bill is nonsense.
• Goods-receipt is physical goods only — a receiver's signature only makes sense for a delivery.
• Born-digital issuers are CLEAN-only. A software/AI business (b2b_saas, ai_platform) is dropped from any non-clean condition (scan or handwritten) — too new to have a hand-filled or aged-paper original. Pinning such a type and a scan/handwritten condition is a hard UnsupportedConstraint.
• Era floor (soft, opt-out). An issue date is floored up to the issuer type's era (e.g. ai_platform → 2025) — but this never blocks a run: it caps within the window, and --no-date-era-floor / enforce_date_era: false turns it off so a run can deliberately produce anachronistic dates.

See Design decisions → Selection for the why behind each.

Two surfaces, one parser

Composition is expressed twice — as docsynth generate flags (--locale/--company/--archetype/--business-type/--condition/--wear/ --goods-receipt) and as a --selection-file YAML block (the same block a deploy.sh slice uses) — behind one parser, so they cannot drift. The studio prompts a single inline slice or points at a run.yaml for a full multi-slice composition.