How decisions are made

Every payment goes through the same steps. A wrong match is worse than no match, so anything uncertain ends with a person.

The steps

Bank statementPayer, variable symbol (VS) and message are written by the payer: untrusted text, never instructions.
RulesPorted from the legacy system. They settle exact matches and say why when they cannot (the codes below).
AI modelOnly for payments the rules could not settle. It reads the text and proposes invoices from a list code prepared; a small model first, a larger one only when that can change the outcome.
Validation by codeThe invoice exists and is open, it belongs to one customer, the amount fits, the payment names it, nothing else fits as well, no instructions in the text.
YouConfirm, reject or match by hand what is uncertain, and undo an AI match that is wrong.

rule FIELD/EXACT: A rule matched it (the code says which, see below).
haiku-5-5: The AI model decided it, after the rules could not; code checked its answer.
policy: Decided by policy without a model, e.g. instructions to an AI in the text, or no invoice of the customer at all.
you: You decided it.
agent:mcp: An AI agent proposed it through the MCP server; only a person can confirm it.

Confidence is the model's own estimate from 0 to 1. Only answers of at least 0.90 that pass every check are matched without you.

The first part says where the reference was found: FIELD = the VS field, MSG = the message, - = nowhere. The second says what happened.

Code	Meaning
`FIELD/EXACT`	Exact match: the variable symbol in the VS field names the invoice and the amount fits.
`MSG/EXACT`	Exact match: the invoice number or VS was found in the message and the amount fits.
`FIELD/PARTIAL`	Partial payment: the VS names the invoice, but less was paid than invoiced.
`FIELD/ADV_OVERPAY`	Advance invoice paid with more than invoiced.
`FIELD/OVERPAID`	More was paid than invoiced (not an advance invoice).
`MSG/OVERPAID`	Invoice found in the message, but more was paid than invoiced.
`MSG/ADV_OVERPAY`	Advance invoice found in the message, paid with more than invoiced.
`MSG/AMOUNT`	Invoice found in the message, but less was paid than invoiced (a partial payment counts only with the VS in the VS field).
`FIELD/NOT_FOUND`	The VS field names no existing invoice.
`MSG/NOT_FOUND`	The message names an invoice that does not exist.
`FIELD/DUPLICATE`	The invoice named in the VS field is already paid.
`MSG/DUPLICATE`	The invoice named in the message is already paid.
`-/NO_VS`	No variable symbol and no invoice number: the rules cannot tell which invoice.
`-/CURRENCY`	A currency the rules do not handle.
`-/INVALID_AMOUNT`	The amount is missing or not valid.
`-/BANK_OWN`	The bank's own entry (fees, interest): not a customer payment.