Dexter adapter

Dexter is the second facilitator AgentTrust supports. It exists to prove that the FacilitatorAdapter contract is portable: every adapter must implement the same five methods, expose the same Zod-validated wire schemas, and use the same SDK factories for on-chain validation and feedback emission. If wiring a second adapter forces route edits, policy edits, or registry-read changes, the adapter boundary failed and gets fixed before the integration ships.

Status: in flight. The current repo carries a stub at trustgate/server/src/facilitators/dexter/ that satisfies the type contract; full implementation lands once Dexter publishes its x402 wire format. Current adapter status: agenttrust_list_facilitators → { name: "dexter", status: "in-flight" }.

What the adapter has to land

The five methods every adapter implements, with Dexter-specific notes:

Implementation pattern: read facilitators/pay-sh/ end to end. Adapt the schemas + signature semantics to Dexter's wire format. Keep the proof-validator's defense list 1:1.

Why Dexter exists in the catalog

Pay.sh proves the adapter pattern handles the canonical x402 case. Dexter exists to prove the pattern handles a different x402 facilitator's quirks without forcing route layer changes. The same FacilitatorRegistry registers it; the same /verify, /settle, /dispute routes dispatch to it; the same SDK factories build its on-chain calls.

import { FacilitatorRegistry, PaySh } from "./facilitators";
import { Dexter } from "./facilitators/dexter";

const registry = new FacilitatorRegistry();
registry.register(new PaySh(payShDeps));
registry.register(new Dexter(dexterDeps));
registry.setDefault("pay-sh");

The route layer never branches on the facilitator name — selection happens via the X-Facilitator request header or the registry's default. Dexter requests use X-Facilitator: dexter; everything else routes to Pay.sh.

What lands when Dexter ships

Each file mirrors the Pay.sh shape. The adapter test suite asserts the FacilitatorAdapter contract conformance — every method's input is type-safe and every method's output matches the documented schema.

Adapter contract conformance

CI runs an adapter-contract conformance workflow (.github/workflows/adapter-contract-conformance.yml) on every PR. It walks every registered adapter and asserts:

• parseRequest accepts the verify-shape and rejects malformed inputs with 400.
• formatChallenge emits the right headers per decision arm.
• validatePaymentProof rejects every member of the standard hostile-input matrix (replay, self-pay, mismatch, expired).
• emitFeedback is idempotent against the same payment_id_hash.

Dexter (when shipped) and any future adapter (atxp, MCPay) hook into the same conformance check. The Pay.sh adapter is the conformance reference — its 50+ test cases cover every branch of the contract.

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