Architecture

Pipeline

1. 1

   Intake & file validation

   Deterministic code

   Type, size, and magic-byte checks. No active content ever reaches a browser context.

2. 2

   OCR & structured extraction

   AI model

   Document rendered and read; header fields and line items extracted into a strict schema (tool-forced JSON).

3. 3

   Evidence alignment

   Deterministic code

   Every extracted value is aligned against the OCR/text-layer token positions. A value that can't be found in the document drops to 'uncertain' — the model never emits its own bounding boxes.

4. 4

   Instruction screening

   Deterministic code

   Notes and free-text fields are scanned for instruction-shaped content before anything downstream reads them.

5. 5

   Arithmetic validation

   Deterministic code

   Line totals, subtotal, tax, and grand total are recomputed from scratch using decimal-safe code — never trusted from the printed figure.

6. 6

   Supplier identity match

   Deterministic code

   Tax ID first, name as a supporting signal only. Multiple credible matches or a new supplier never auto-resolve.

7. 7

   Duplicate detection

   Deterministic code

   File hash, normalized identity (supplier + invoice number + date + amount), and line-item fingerprint — runs before any approval routing.

8. 8

   PO & receipt matching

   Deterministic code

   Supplier, currency, status, and remaining balance compared; SKU takes precedence over description similarity.

9. 9

   Tolerance & exception rules

   Deterministic code

   Configured, versioned tolerances decide pass/fail — not a confidence score.

10. 10

    Exception summary drafting

    AI model

    Plain-language explanation generated only from already-verified control results — the model never sees or drafts from unscreened invoice text.

11. 11

    Decision & routing

    Deterministic code

    Ready / Exception / Duplicate Hold / Blocked, with an approval route and required actions.

12. 12

    Accounting draft

    Deterministic code

    Idempotent draft-bill creation only. No workflow can execute a payment.

13. 13

    Human review

    Human

    AP and approvers act on exceptions, holds, and blocks — every decision recorded to the audit trail.

Tolerance policy

Fictional v1 values — all versioned as configuration (current: policy_2026.3).

Security & privacy

• Invoice text and QR codes are treated as untrusted data — embedded instructions directed at the model or operator are ignored, never executed.
• File type, size, and magic bytes are validated at intake. A real AV engine is not practical on serverless infrastructure — this is documented as a production deployment requirement, not simulated.
• All tables are RLS-locked to service-role access only, from the first migration.
• Remittance/bank details from an invoice never overwrite the supplier master, ever.
• Bank and tax identifiers are masked in ordinary logs; full document text is kept out of model-provider logs.
• Invoice submitters cannot approve their own invoices.
• No real supplier or financial data appears anywhere in the public portfolio.