SealStack

Signed, hash-chained action records for AI agents, with a server receipt for every record and a verifier that runs offline.

Download the 60-second demonstration (MP4, silent, 1920x1080, 2.8 MB).

Agent action → signed event → hash chain → SealStack service receipt → offline verification → optional AERF / Agent Receipts / noa export

SealStack turns what an AI agent did into evidence that someone outside your infrastructure can check. Each action is signed on your own host, by the agent's own key, before it runs. The actions of one agent run are hash-chained, so the record is tamper-evident: a change, a reordering or a deletion breaks the chain. The SealStack service counter-signs every record it accepts and hands back a cryptographic agent receipt. A receipt verifies offline, from the bundle and a trust file alone, with no network call and no access to your systems. That is an AI agent audit trail you can hand to an auditor, a customer or a reviewer, and it is the kind of evidence you can keep for EU AI Act record-keeping obligations. Receipts also export to AERF, to the Agent Receipt Protocol and to the noa SCITT agent receipt profile.

Read this caveat before anything else: agent key rotation is disabled in V1, sealstack rotate-key exits 2 with a message pointing at v0.2, and there is no dashboard rotation action.

Install

pip install sealstack

The package is published to PyPI with the v0.1.3 release, and that line becomes valid at release; until then, run pip install . from a checkout.

Before 0.1.3 the package imported as product; that name still works as an alias, so from product import AuditClient and the product command keep working. New code should use sealstack.

Quickstart

Set AUDIT_API_KEY to an API key and SEALSTACK_API_URL to the origin you are uploading to. That is either the hosted service or the reference server in this repository, which you can run on your own machine. For a first run, use the reference server (see Reference server).

export SEALSTACK_API_URL=http://127.0.0.1:8000
export AUDIT_API_KEY=pick-a-long-random-string

import os
from sealstack.client import AuditClient

audit = AuditClient(api_key=os.environ["AUDIT_API_KEY"], agent_name="billing-agent")


@audit.track(action="invoice.create", resource_type="invoice", resource_id="INV-2026-0042")
def create_invoice(customer_id, amount_cents):
    return {"invoice_id": "INV-2026-0042", "total": amount_cents}


create_invoice("cust-118", 24900)
audit.close()

Quickstart detail explains what those lines do and how the client is configured.

What problem SealStack solves

An application log is a record your own system writes and your own system can change. AI agent logging of that kind answers what you can still read in your own database; nothing inside the file shows whether a row was edited, reordered or removed afterwards, and a reader outside the system that produced it has no way to tell.

SealStack records the same actions as a cryptographic audit trail for AI agents, which differs in three ways:

• Signed before the fact. The agent signs the record with an Ed25519 key held on its own host, before the action runs. Forging a record for a registered agent means holding that private key.
• Chained. Records of one runtime carry the previous record's hash, so removing, reordering or editing one of them is detectable from the records themselves. That is what makes them tamper-evident agent logs rather than rows in a table.
• Counter-signed. The service signs what it accepted, with the acceptance context it resolved at that moment. This is a counter-signature by the receiving service, not an attestation by an independent third party.

The result is AI agent accountability and AI agent compliance evidence that survives leaving the database it was stored in: the person checking it needs the exported bundle and a list of service verification keys, and nothing else.

See it working

The 60-second film above is the fastest version: download it. Then three real captures.

The activity page of the dashboard. Ten rows for one agent named billing-agent, under the columns TIME, AGENT, ACTION, RESOURCE, STATUS, SPONSOR and VERIFICATION. The action names are invoice.create, customer.email.send, customer.update and ledger.reconcile. The STATUS column carries the event type, so the ten rows are five actions, each one an action.started row plus its outcome row: four action.completed and one action.failed. Every row names the same sponsor, resolved by the service at ingestion, and every row reads VALID in the VERIFICATION column.

One event page. The heading reads VERIFICATION STATUS: VALID, directly above the sentence "This status describes cryptographic signature and hash validity only. It is not evidence that the external real-world action occurred, nor that logged inputs and outputs were truthful." Below that: the action invoice.create, the event type action.completed, the agent billing-agent, the agent key id marked (active), the agent key fingerprint as a sha256: hash, the runtime id, sequence 2, the occurred-at and received-at times, the resource invoice / INV-2026-0042, the sponsor, the capability grant id with the three capabilities it lists, the error type none, the event hash as a sha256: hash, and the agent signature.

Offline verification of an exported receipt, captured from a terminal after the server had been stopped:

$ sealstack verify receipt.json --trusted-service-keys keys.json
Event hash:              VALID
Agent signature:         VALID
Agent key fingerprint:   VALID
Service receipt:         VALID
Runtime chain link: VALID
$ echo $?
0

How it works

flowchart LR
  subgraph customer["Your infrastructure"]
    direction TB
    agent["Agent process<br/>@audit.track / audit.action"]
    key["identity.json, mode 0600<br/>Ed25519 private seed<br/>never leaves this host"]
    sign["Sign the event<br/>RFC 8785 bytes, SHA-256, Ed25519<br/>previous_event_hash links the chain"]
    queue["audit_queue.db<br/>local SQLite durable queue"]
    agent --> sign
    key --> sign
    sign --> queue
  end

  subgraph service["SealStack service"]
    direction TB
    auth["API key, Bearer token"]
    accept["Acceptance checks<br/>schema, canonical hash,<br/>agent signature, sequence,<br/>previous hash"]
    receipt["Service receipt<br/>signed with the service key"]
    auth --> accept
    accept --> receipt
  end

  subgraph verifier["Verifier, offline"]
    direction TB
    trust["Trust file<br/>/v1/verification-keys,<br/>fetched out of band"]
    check["sealstack verify<br/>makes no network calls"]
    trust --> check
  end

  queue -->|"POST /v1/events/batch"| auth
  receipt -->|"evidence bundle: event, signature,<br/>agent public key, receipt,<br/>service key metadata"| check

Two properties of that picture are worth stating plainly:

• The agent private key never crosses the boundary. It is generated on the customer host, kept in identity.json at mode 0600 in the state directory, and only its public half is registered. The service never receives it, and sealstack export reads it on the customer machine too.
• The service cannot forge an agent signature. It holds only the agent's public key, so it can check a signature and it can counter-sign what it accepted, but it cannot produce a record that verifies as the agent's. Symmetrically, the agent cannot forge a service receipt: the verifier resolves the service key only in the trust file it was given, never from the bundle it is checking.

What gets verified

V1 proves three things about every record the service accepts: that a registered agent key signed it before the action ran, that it sits where it claims inside its runtime chain, and that the service signed what it accepted.

The exact verification procedure, step by step with its statuses and exit codes, is Section 10.3 of SPEC-RECEIPT.md.

What it does not prove is carried byte for byte in every exported receipt. The verifier rejects a bundle whose copy of it differs.

This receipt verifies cryptographic relationships between the
included data, registered keys and service receipt.

It does not independently prove:

• that an external real-world action occurred;
• that logged inputs or outputs were truthful;
• that the agent host was uncompromised;
• that the private key was never stolen;
• that uninstrumented actions did not occur;
• the legal identity of a human sponsor;
• that the sponsor personally authorised this individual action;
• legal liability;
• regulatory compliance.

Interoperability

sealstack export rewrites one evidence bundle into an external receipt format, signing the result with the agent key on your machine. The server never sees that key and takes no part in the export.

sealstack export --format aerf receipt.json --state-dir ~/.sealstack/billing-agent
sealstack export --format agent-receipts receipt.json --state-dir ~/.sealstack/billing-agent
sealstack export --format scitt receipt.json --state-dir ~/.sealstack/billing-agent

Format	Target version	Modes	Signing location	External verification	Known limitation
AERF, Agent Evidence Receipt Format	v0.1.0-draft.1 (tag v0.1.0-draft.1 of github.com/aerf-spec/aerf)	subset (default) and full (--mapping)	Customer side: the SDK reads the agent key from the local identity directory or a seed file	The AERF Go reference verifier built from the v0.1.0-draft.1 tag and from the repository main branch (v0.2.0-draft.1); full-mode artifact exits 0, a tampered copy exits 1	An artifact whose evidence contains non-ASCII text verifies under the v0.1.0-draft.1 verifier and fails under the main-branch verifier; the golden fixture is ASCII and passes both
Agent Receipt Protocol	0.5.0 (agentreceipts.ai, @context https://agentreceipts.ai/context/v2)	subset (default) and full (--mapping)	Customer side, same key and same lock	The obsigna Python package (its build on this machine reports protocol 0.6.0 and context v3; its verify_raw and verify_receipt accepted the 0.5.0 artifact and rejected a tampered copy)	The schema declares no extension point for foreign evidence, so the native bundle travels beside the artifact as <artifact>.sealstack.json
noa profile, draft-noa-scitt-ai-agent-receipt-01	noa.receipt/0.1, bare receipt form	subset (default) and full (--mapping)	Customer side, same key and same lock	Internal specification-derived test only. No external or reference verifier was run	The receipt is a closed object, so the native bundle travels beside it as <artifact>.sealstack.json; no COSE_Sign1 envelope, SCITT Signed Statement or transparency registration is produced

The default subset mode omits fields whose semantics SealStack does not record, writes no placeholder in their place, and labels the artifact non-conformant with the exact list of missing fields. Full mode takes an operator mapping file and refuses to write anything when an action is missing from it.

Four limitations apply to all three exports: subset artifacts are not conformant to their target specification; full-mode conformance depends on the operator's mapping being truthful, because SealStack does not evaluate policy, classify actions or assess risk; the AERF and Agent Receipts production profiles expect RFC 3161 trusted timestamps and none is produced; and chain fields are set only when predecessor evidence is in the bundle. SealStack does not consume any of these formats, and sealstack verify reads only the native bundle.

COMPATIBILITY.md states the exact version of each target format, every field mapping, what was verified against which external verifier, and the limitations of the exports.

Offline verification

Fetch /v1/verification-keys from the service origin over authenticated HTTPS, save it as a local trust file, and pass it explicitly. The verifier makes no network calls and never reads trust from the bundle it is checking.

sealstack verify receipt.json --trusted-service-keys service-keys.json

Exit codes:

Code	Meaning
0	Cryptographically valid for the supplied evidence
1	Invalid
2	Incomplete or unverifiable

The Runtime chain link line reports the chain only for a predecessor bundle you supplied. Without one, the verifier reports the runtime chain as NOT VERIFIED instead of inferring history it has not seen.

Change one field inside the bundle and the same command prints INVALID and exits 1. This capture flips a single character of the service receipt signature:

flipped service_receipt.signature[0]: 's' -> 't'

$ sealstack verify receipt.json --trusted-service-keys keys.json
Service receipt:         INVALID — bundle: service receipt signature does not verify
Evidence bundle:         INVALID — bundle: service receipt signature does not verify
$ echo $?
1

Quickstart detail

The full form of the quickstart, with a context manager beside the decorator:

import os
from sealstack.client import AuditClient

audit = AuditClient(api_key=os.environ["AUDIT_API_KEY"], agent_name="billing-agent")


@audit.track(action="invoice.create", resource_type="invoice", resource_id="INV-2026-0042")
def create_invoice(customer_id, amount_cents):
    return {"invoice_id": "INV-2026-0042", "total": amount_cents}


create_invoice("cust-118", 24900)

with audit.action("ledger.reconcile", resource_type="ledger", resource_id="2026-09"):
    pass  # your own reconciliation work goes here

audit.close()

The first AuditClient generates an Ed25519 key pair on your host, registers the public half and keeps the private seed in the state directory. @audit.track writes an action.started record before your function runs and an action.completed or action.failed record after it returns; it decorates async functions too. audit.action(...) does the same for a block that is not a single call. The business function runs exactly once and always returns its own result or raises its own exception.

SDK configuration

AuditClient resolves two settings with the same precedence: constructor argument, then environment variable, then default.

• API base URL: base_url argument, then SEALSTACK_API_URL, then https://api.sealstack.com.
• State directory: state_dir argument, then SEALSTACK_STATE_DIR, then ~/.sealstack/<agent_name>.

Reference server

reference-server/ implements the four SDK-facing endpoints so you can run the whole loop on your own machine: register an agent, upload signed events, get counter-signed receipts and verify them offline.

The reference server is not part of the PyPI package: pip install sealstack does not install it. Clone this repository and run it from the checkout.

git clone https://github.com/unempyd/sealstack-sdk
cd sealstack-sdk
pip install -e ".[reference-server]"
SEALSTACK_REF_API_KEY=pick-a-long-random-string \
    uvicorn server:app --app-dir reference-server --host 127.0.0.1 --port 8000

It is not the hosted service and it is not a production server. One tenant, one bearer key, SQLite storage, no dashboard, no user accounts, no sponsor or capability-grant context, no key rotation, and a signing key that sits on the same machine as the agent. reference-server/README.md states exactly what it checks and what it leaves out.

Security and limitations

Key rotation

Agent key rotation is disabled in V1: sealstack rotate-key always exits 2 and prints a message pointing to v0.2. There is no dashboard rotation action. The server endpoint POST /v1/agents/{agent_id}/keys is retained as v0.2 groundwork and remains covered by the acceptance tests.

Documents

File	Contents
SPEC-RECEIPT.md	The receipt format: records, canonical encoding, hash chain, receipt, evidence bundle and the offline verification procedure.
COMPATIBILITY.md	What SealStack emits, which external formats it can produce, how each export is built and what was verified.
SECURITY.md	How to report a vulnerability, and what V1 does and does not defend against.
DEVIATIONS.md	Where this SDK differs from the specification.
LICENSE	Apache-2.0.

This repository is an export of the SDK from the SealStack source repository; it is regenerated by that repository's scripts/export-sdk.sh, so open pull requests here against the SDK files with that in mind.

Layout

Path	Contents
sdk/sealstack/	The SDK, the CLI and the offline verifier.
sdk/product/	The pre-0.1.3 import name, kept as an alias of sdk/sealstack/.
sdk/tests/	Platform and export-format tests, with their fixtures.
reference-server/	The minimal server described above, and its tests.
assets/	The mark, the 60-second film, its poster and the dashboard captures used in this README.

pip install -e ".[dev]"
pytest -q
ruff check .
mypy --strict --explicit-package-bases sdk/sealstack reference-server