Decline codes

A decline carries three things: a haltClass, a code, and a detail sentence written to be forwarded to the counterparty.

import type { GateDecision } from "@integraledger/agent-guard";

declare const decision: GateDecision;

if (decision.kind === "decline") {
  console.error(`[${decision.haltClass}] ${decision.code}: ${decision.detail}`);
}

Verification failures

The guard cannot say the document is the one that was advertised. The seller can act on all of these.

Code	Raised when	What the seller should do
`gate/terms-unfetchable`	the advertised terms URL did not serve — a non-2xx status, a TLS failure, a redirect, a body over the cap, or a host that failed the public-unicast check	serve the document at the URL advertised, over HTTPS, without a redirect
`gate/fingerprint-mismatch`	the recomputed SHA-256 over the served bytes ≠ the advertised `atrHash`	re-advertise the hash of the bytes actually being served, or serve the bytes the hash was taken over

gate/terms-unfetchable carries the fetcher's own message verbatim, so the detail names which failure it was — the status, the cap, or the resolved address that was refused. That precision is the point: a buyer that cannot say which failure occurred cannot report it.

A redirect is a fetch failure here, deliberately. The fetcher sets redirect: "error", so a seller whose terms URL 301s to the real document sees gate/terms-unfetchable rather than a silent follow to wherever the redirect pointed.

Policy rejections

The document was established. Your stated policy refused it — the seller may be operating entirely correctly.

Code	Raised when
`gate/below-required-level`	the proposal's level is below your `requiredLevel`
`gate/assurance`	the seller's assurance is below your `requiredAssurance`
`gate/unparseable-terms`	the terms are not machine-readable legal-context JSON, and your `onNotAttempted` is `decline`
`policy/jurisdiction`	the declared dispute jurisdiction is not in your `acceptableJurisdictions`
`policy/dispute-method`	the declared dispute method is not in your `acceptableDisputeMethods`
`policy/unit`	you declared no cap for the offer's unit
`policy/over-cap`	the offer amount exceeds your cap for that unit
`policy/forbidden-clause`	the record declares a clause category you forbid

The seller's own defects

Also policy-rejection, but distinct in what they say: the field is present and malformed. These are named as the seller's defect rather than read as absence, because a refusal that misdescribes the defect cannot be acted on.

Code	Raised when
`policy/malformed-dispute-resolution`	`disputeResolution` is not an object, or one of `jurisdiction` / `method` is present and not a string
`policy/malformed-clause-categories`	`clauseCategories` is present and not an array

A seller publishing "disputeResolution": "arbitration" gets "your disputeResolution is a string, not an object" — not "jurisdiction (none) not acceptable", which would tell it to fix a jurisdiction that was never the problem.

Parser refusals

These are thrown, not returned, because they happen before a proposal exists — there is nothing yet to decide about. Fail-fast at the trust boundary.

Thrown when	Message names
the challenge does not match the protocol's shape	the Zod validation failure
both x402 carriers advertise, and they disagree	the field, and both advertised values
neither x402 carrier advertises the field	which field, and both carriers that were checked
the advertised hash is not `0x` + 64 hex	the value received
the terms URL is not HTTPS	the URL
the offer amount is not a base-unit integer	the value received
a document matches more than one protocol's discriminant	every protocol that matched
the protocol is identified but this build cannot read its offer	which protocols are parseable

Ambiguity refusing rather than guessing is covered in protocols.

Codes that are not declines

Two more codes exist, and neither is ever returned as a decision. gate/proceed and gate/escalate are what the record carries for the other two outcomes, so a log reader can tell the three apart by one field. A switch over decision codes never sees them.