Generate X12 EDI transactions

The @cosyte/synth/x12 subpath builds HIPAA 005010 transactions through @cosyte/x12's domain builders (build837P/I/D, build835, build271), so the ISA/GS/ST…SE/GE/IEA envelope, the computed HL spine, the control numbers, and every segment are the builder's own - each transaction is spec-clean by construction and round-trips through @cosyte/x12 with zero warnings. @cosyte/x12 is an optional peer dependency, needed only for this subpath.

The X12 surface emits:

• 837 claims - Professional (generate837P), Institutional (generate837I), and Dental (generate837D);
• the 835 remittance (generate835) - balance-checked by construction (the line, claim, and remit balance identities are satisfied before the builder is called, so build835 never refuses it);
• the 271 eligibility response (generate271).

A claim, spec-clean by construction

The round-trip harness proves spec-cleanliness by @cosyte/x12's own judgment - a spec-clean interchange re-parses with zero warnings and re-serializes byte-identically:

import { generate837P, roundTrip } from "@cosyte/synth/x12";

// Same seed → byte-identical EDI, on any machine, any run.
const result = roundTrip(generate837P({ seed: 12345 }));
result.warnings; // => []
result.byteStable; // => true
result.specClean; // => true

A reproducible corpus

x12Corpus builds a self-describing, deterministic corpus - one of each of 837P/I/D + 835 + 271 by default:

import { x12Corpus } from "@cosyte/synth/x12";

const corpus = x12Corpus({ seed: 42 });
corpus.artifacts.map((a) => a.kind); // => ["837P", "837I", "837D", "835", "271"]
corpus.artifacts.every((a) => a.warnings.length === 0); // => true

Synthetic-by-construction, hardest-attacked here

An 837/271 is identity-dense - it carries subscriber and patient names, member ids, provider NPIs, a provider tax id, dates of birth, and addresses across two HL loops. Every value has a construction-level guarantee, not a heuristic:

• NPI (NM1*XX) - a 10-digit National Provider Identifier with a deliberately-invalid Luhn check digit. A real NPI must satisfy the CMS 80840-prefixed Luhn check, so a synth NPI can never be a NPPES-issued provider. (safe.npi, isSyntheticNpi.)
• Provider tax id (REF*SY) - an SSA never-issued (900-range) SSN, so it can never be a real SSN or a sole-proprietor's real tax id.
• Member id (NM1*MI) - scoped to a synthetic assigning authority (there is no reserved member-id range, so the namespace is the guarantee).
• Names - the shipped clearly-fake pool; DOBs / dates - the seeded generator (no real event implied); addresses - a synthetic street + reserved ZIP.

The repository's phi-scan gate runs X12-aware structured detection over every generated corpus: a Luhn-valid NM1*XX NPI, a real-area REF*SY SSN, or an NM1*34 raw-SSN qualifier is a hard failure.

Deferred

• The 270 eligibility request: @cosyte/x12 ships a build271 but no build270 (the 270 is only read, as the echoed trace on a 271). synth never hand-writes bytes around a missing builder, so 270 generation lands when @cosyte/x12 grows build270.
• Vendor-quirk mode (deliberately off-spec fixtures) is deferred for X12.