# AFD (Portaria MTP 671/2021) conventions

- Layout version 004, ISO-8859-1 text, `\r\n` line separators. Each line: 9-digit NSR + 1-digit record type.
- Only decode fields with an exactly-documented byte position; anything undocumented goes into a raw-tail capture — never guessed.
- CRC-16/KERMIT (poly 0x1021 reflected as 0x8408, init 0x0000, no final XOR) validates record types 2/3/4. Type 7 uses its own hash chain (never recomputed). Types 1/5/6/9 have no validatable CRC.
- CPF normalization: take the last 11 numeric digits of the raw field (never assume exact formatting) — same rule used to match against `timeclock_employees.cpf` and to relink orphaned records.
- Idempotency: whole-file (SHA-256) at import time, per-record (`device_id + nsr` unique) at insert time.
- `afd_records` is immutable — invalid/unsupported-layout rows are still inserted (never discarded), just excluded from the apuração calculation (`validation_status IN ('VALID','WARNING')` filter).
- Apuração timezone is always fixed `America/Sao_Paulo`, independent of server timezone (Brazil has had no DST since 2019).
- Tolerance (Art. 58 §1º CLT): per-event tolerance capped by a daily aggregate budget, both configurable per work schedule, not hardcoded.