@postcept/relay

Read your system of record where it already lives and send Postcept a signed observation instead of your credentials.

The relay runs in your environment. It reads the system of record (Stripe today, or a mock ledger for trying it out) with a key you control, normalises what it saw, signs it, and sends that signed observation to Postcept. Postcept checks the signature against a public key you registered, rejects replays and stale or tampered submissions, and verifies the agent's claim against what your relay reported. The receipt names the relay as the source.

Your provider key and the relay's signing seed never leave your environment.

Quick start (mock ledger, no provider account)

npx @postcept/relay keygen

Register the printed public key with POST /v1/relay-keys to get a relay id, then:

export POSTCEPT_API_KEY=pcpt_sk_...
export POSTCEPT_ORG_ID=org_...
export POSTCEPT_RELAY_ID=rly_...
export POSTCEPT_RELAY_SEED=...        # from keygen, keep it secret

npx @postcept/relay observe refund --operation op_1 --refund-id re_4md82k

Then verify against the observation:

curl -X POST https://api.postcept.com/v1/verifications \
  -H "Authorization: Bearer $POSTCEPT_API_KEY" -H "Content-Type: application/json" \
  -d '{"operation_id":"op_1","agent_id":"my-agent","connector":"relay",
       "claim":{"refund_id":"re_4md82k","amount_cents":12000,"currency":"usd",
                "customer":"[email protected]"}}'

The receipt's connectors_checked reads relay:rly_..., so the evidence shows the source was your observation and not a Postcept-held credential.

Stripe (read-only)

Create a restricted Stripe key with read access to Refunds and Charges. That is everything this connector calls. Then:

export CONNECTOR=stripe
export STRIPE_API_KEY=rk_live_...     # restricted, read-only
export EVIDENCE_MODE=minimal          # optional, omit the customer identity

With EVIDENCE_MODE=minimal the customer field is left out and Postcept skips the customer check rather than passing it, so sending less evidence never raises confidence.

Durability

Signed observations are written to a local queue (POSTCEPT_RELAY_DATA, JSONL) before any network call, so a crash or an unreachable control plane loses nothing. flush (or the run loop, every 15 seconds) retries transient failures and moves permanently rejected observations to dead.jsonl for inspection. run serves GET :8477/healthz with the queue depth.

Docker

npm run build
docker build -t postcept-relay packages/relay
docker run -e POSTCEPT_API_KEY=... -e POSTCEPT_ORG_ID=... \
  -e POSTCEPT_RELAY_ID=... -e POSTCEPT_RELAY_SEED=... \
  -v relay-data:/relay/data postcept-relay

Deploying

deploy/helm is a Helm chart. It creates no Service or Ingress, uses a PVC for the queue, and reads secrets from a Secret you manage. deploy/cloud-run covers a serverless worker, with a note on queue durability on ephemeral filesystems.

What a signed observation proves

An accepted observation shows it came from your registered relay, unchanged, recently, and once. It does not show that the provider's answer was itself correct, which is why the receipt names the relay and why revoking a relay key (DELETE /v1/relay-keys/{id}) takes effect right away.