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cyclone/docs/superpowers/specs/2026-06-21-cyclone-npi-validation-design.md
T
Tyler 1942a22629 feat(sp20): NPI Luhn checksum + Tax ID (EIN) format validation
Adds pure local validators for the 10-digit NPI Luhn checksum (CMS-
published algorithm with the '80840' NPPES prefix) and 9-digit EIN
format (rejects reserved prefixes 00/07/80-89). No NPPES round-trip,
no IRS e-file lookup — catches the 99% typo case at parse time.

Surface:
- cyclone.npi.is_valid_npi / is_valid_tax_id / normalize_tax_id
- CLI: 'cyclone validate-npi <npi>' and 'cyclone validate-tax-id <ein>'
- API: GET /api/admin/validate-provider?npi=&tax_id=
- Parser validator: new R021_npi_checksum rule (warning, not error,
  to keep test fixtures with placeholder NPIs ingestible)
- minimal_837p.txt fixture NPI updated from '1234567890' to the
  Luhn-valid '1993999998' so strict-mode CLI parses still pass

Tests:
- test_npi.py — 27 cases (Luhn math, valid/invalid NPIs, EIN cases,
  normalize_tax_id edge cases)
- test_api_validate_provider.py — 4 cases (both valid, both invalid,
  omitted NPI, omitted tax_id)
- test_cli_validate.py — 8 cases (valid/invalid for both subcommands,
  exit codes, malformed inputs)
- test_validator.py — 4 new R021 cases (valid Luhn silent, bad Luhn
  warning, skipped when format bad, skipped when NPI missing)

Total: 923 tests pass.
2026-06-21 10:46:10 -06:00

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Markdown

# SP20 — NPI Checksum + Tax ID Format Validation
**Date:** 2026-06-21
**Branch:** `sp20-npi-validation`
**Status:** Shipped
**Scope:** Backend only. No frontend changes.
---
## 1. Why this exists
Cyclone's completeness review (`docs/reviews/2026-06-20-cyclone-completeness-review.md`
§3.1.10) flags this gap:
> **No NPI validation.** NPIs are captured (`claim.party.npi`) and
> used in matching, but never validated against the NPPES registry.
> Bad NPIs (typos, deactivated) silently propagate.
A real NPI is 10 digits where the last digit is a **Luhn checksum**
over the 9 preceding digits prefixed with the constant `80840`
(NPPES's "healthcare provider identifier" prefix).
**Tax ID** format: 9 digits, optionally formatted `XX-XXXXXXX`. We
don't validate against the IRS (that requires their published
e-file schema), but we *do* catch obvious typos — non-numeric chars,
wrong length, EIN prefix `00`/`07`/`8X` (reserved / never assigned).
This SP adds both checks as pure local validators — no network, no
NPPES call. Operators who want real NPPES verification can wire it
in later; this SP catches the 99% case (a typo) at parse time.
## 2. Operator surface
| Surface | Usage |
|---------|-------|
| Python | `from cyclone.npi import is_valid_npi, is_valid_tax_id` |
| CLI | `cyclone validate-npi 1881068062` |
| CLI | `cyclone validate-tax-id 72-1587149` |
| API | `GET /api/admin/validate-provider?npi=1881068062&tax_id=72-1587149` |
The parser's claim-level validator (cyclone.parsers.validator) gains
a new R-rule that flags bad NPIs as a `validation.warning` (not an
error — the operator might be intentionally ingesting test files with
placeholder NPIs).
## 3. Files
* `cyclone/npi.py` — new module (~120 LOC). `is_valid_npi()`,
`is_valid_tax_id()`, `npi_checksum()`, plus the NPPES constant.
* `cyclone.parsers.validator` — new rule that flags bad NPIs in the
billing / rendering / referring / service-facility loops.
* `cyclone.api` — new admin endpoint.
* `cyclone.cli``validate-npi` + `validate-tax-id` subcommands.
* Tests: `test_npi.py` (12), `test_api_validate_provider.py` (4),
`test_cli_validate.py` (4) — 20 new tests.
## 4. Threat model
NPIs and tax IDs are sensitive (PHI under HIPAA). The validators run
locally; nothing leaves the process. The CLI's `validate-npi`
subcommand doesn't log the value (operators shouldn't paste real
NPIs into shared logs).