> ## Documentation Index
> Fetch the complete documentation index at: https://docs.phala.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Receipts and Sessions

> Learn how per-response receipts and attested sessions prove what happened to a Confidential AI request.

Receipts and sessions are the two response-level artifacts you use after verifying the gateway attestation report.

* A **receipt** is the signed record for one response.
* A **session** is the immutable verified security context for a confidential upstream channel.

## Receipt Lifecycle

Every inference response includes `x-receipt-id`. Fetch it with [Get Receipt](/phala-cloud/confidential-ai/confidential-model/api-reference/receipts):

```bash theme={"system"}
curl "https://inference.phala.com/v1/aci/receipts/$RECEIPT_ID" \
  -H "Authorization: Bearer $API_KEY"
```

The receipt records ordered events with hashes and facts, not prompt text.

| Event               | What it records                                                          |
| ------------------- | ------------------------------------------------------------------------ |
| `request.received`  | Hash of the request body observed by the gateway.                        |
| `route.selected`    | Selected backend route.                                                  |
| `request.forwarded` | Hash of the provider-facing request.                                     |
| `upstream.verified` | Provider verification result, channel binding, claims, and `session_id`. |
| `response.received` | Hash of the provider response before post-processing.                    |
| `response.returned` | Hash of the final wire response.                                         |

## What a Receipt Proves

A verified receipt proves:

1. The receipt was signed by a key in the attested gateway keyset.
2. `workload_id` and `workload_keyset_digest` match the attestation report.
3. The returned response bytes match `response.returned.wire_hash`.
4. The upstream verification result for that response is recorded.

## Streaming Responses

For streaming, `x-receipt-id` can arrive before the stream ends. Fetch the receipt after the stream completes because `response.returned.wire_hash` covers the full response body.

## Attested Sessions

When the gateway verifies a confidential upstream, it records an attested session. A receipt references it from `upstream.verified.session_id`.

A session captures:

* Verified upstream identity and endpoint.
* Enforced channel binding.
* Typed claims and reasons.
* Evidence digest and evidence payload.

The `session_id` is content-addressed. If the verified material changes, the session id changes.

## Trace a Response

```text theme={"system"}
response -> x-receipt-id
receipt  -> upstream.verified.session_id
session  -> provider identity, binding, claims, evidence
```

For most applications, the receipt has enough data to decide whether a response was confidential. Fetch the session when you need deeper audit evidence.

## Related

<CardGroup cols={2}>
  <Card title="Verify a Response" icon="circle-check" href="/phala-cloud/confidential-ai/verify/verify-signature" />

  <Card title="TCB and Claims" icon="list-check" href="/phala-cloud/confidential-ai/confidential-model/tcb-and-claims" />
</CardGroup>