sanning-anchor

Produce verifiable evidence from your Python agents: hash locally, anchor a signed commitment, and hand an auditor a pack they verify offline. Nothing in this package needs a wallet, a chain identity, or a Sanning account to check.

Node is not required at any point. The bundle command that assembles a hand-over pack is a Python console script, and so is everything before it.

• The path from signup to a verified event is at docs.sanning.io.
• The wire format, the envelope profile and the pack body type are specified in documents that ship inside sanning-proof, beside the kernel that implements them.

Install

pip install sanning-anchor

An API key comes from console.sanning.io/signup: email, password, organisation name, no card. Give the key producer:enroll and anchor:write to anchor, and anchor:read as well if the same key will later build a hand-over pack. The console pre-checks the first two. A key holding only anchor:write anchors nothing, because the plane refuses an envelope whose signing key the organisation has not enrolled; a key holding no anchor:read anchors correctly and then fails at hand-over.

Anchor an event

import json
import os

from nacl.signing import SigningKey
from sanning_anchor import Anchorer, FsLogStore

anchorer = Anchorer(
    # Writes to a permanent public record. Use "dev" until you mean it.
    environment="production",
    # Your Ed25519 identity key. Keep the seed: a different seed is a different agent.
    signing_key=SigningKey(bytes.fromhex(os.environ["SANNING_SIGNING_SEED"])),
    subject={"type": "producer", "producer_id": "claims-triage"},
    api_key=os.environ["SANNING_API_KEY"],
    log_store=FsLogStore("./logstore"),
)

result = anchorer.anchor(
    event_type="claims.decision",
    # Hashed in this process. These bytes are never sent to Sanning.
    content=json.dumps(decision).encode(),
    metadata={"reviewer": "queue-3"},
)

anchorer.close()

result.event_id  # the id this process minted
result.record_bytes  # retain these: the bytes payload_hash commits to

Replace the following:

• SANNING_SIGNING_SEED with a 32-byte Ed25519 seed, 64 hex characters, that your service keeps across restarts. An agent's identity is this key, not its name. bytes.fromhex accepts either case; the TypeScript SDK's fromSeedHex takes lowercase only.
• SANNING_API_KEY with the key from the console.
• claims-triage with the identity you want the evidence attributed to.

@sanning/anchor takes the same arguments under TypeScript naming and writes the same bytes, so a mixed fleet hands over one pack.

Enrolment is automatic

The example writes no enrolment step, and that is the whole of it: on the first anchor(), the SDK proves possession of your signing key to the control plane, and your agent appears on Fleet under producer_id. One organisation key covers the whole fleet: no per-agent credential, no enrol script. It is not optional politeness, because the plane refuses an envelope signed by a key your organisation has not enrolled (SIGNING_KEY_NOT_ENROLLED, HTTP 403).

Three properties are load-bearing:

• The challenge is shape-checked before it is signed. Enrolment is the one moment your identity key signs bytes the server chose, and that key also seals your envelopes, so the SDK refuses anything that is not a nonce rather than trusting Sanning not to send an envelope pre-image. Sanning is never in the trust path, including here.
• A different key for a producer_id your organisation has enrolled is a rotation, and it needs the retiring key's counter-signature (previous_signing_key=). It is never inferred from a refusal: that is what stops a leaked organisation key silently taking over an identity that is already producing evidence.
• Verification never depends on the roster. Enrolment is the plane's door policy, not the trust path. Every signed record verifies offline against sanning-proof, enrolled or not.

Enrolling out of band at deploy time instead? auto_register=False turns the call off, and ensure_registered() is exported for you to drive:

from sanning_anchor import ensure_registered

ensure_registered(
    api_key=os.environ["SANNING_API_KEY"],
    producer_id="claims-triage",
    signing_key=key,
)

Behaviour is identical to the TypeScript SDK, pinned by a shared conformance oracle that calls neither of them.

What never leaves your process

Your content does not. It is hashed locally and only the hash goes into the signed envelope. The control plane is content-blind by construction rather than by policy: it never receives the bytes, so it cannot disclose them.

record_bytes is your retention obligation. It is what payload_hash commits to. Sanning never holds it, so losing it leaves you holding a commitment to something you can no longer produce.

No Arweave wallet, no chain identity, no data item. Placement is Sanning's act, which is why this package holds no blockchain code at all, and why it is a few hundred lines rather than a chain client.

Retain what you anchored

Pass log_store= and the SDK writes both halves an auditor needs before the event is anchored: the content you handed it, and the canonical event record the envelope commits to. If the store write fails, nothing is anchored. There is deliberately no best-effort mode, because under this write path nothing else holds those bytes.

FsLogStore is the development destination. For production, sanning_anchor.s3 supplies an S3-compatible object store behind the same seam, and the on-disk shape is a versioned contract, specs/log-store.md in the sanning-proof package, so an auditor holding nothing but the directory can resolve it without a connector and without Sanning.

--logs takes a local store root or an s3:// URL. Reading a bucket needs SANNING_S3_ENDPOINT, SANNING_S3_ACCESS_KEY_ID and SANNING_S3_SECRET_ACCESS_KEY in the environment, and a missing one is named individually. There is no flag for them: a credential in argv lands in shell history. The reader credential is enough, s3:GetObject and s3:ListBucket.

Trace a LangChain agent

pip install "sanning-anchor[langchain]"

from sanning_anchor import AnchorCallbackHandler

with AnchorCallbackHandler(anchorer) as handler:
    agent.invoke(inputs, config={"callbacks": [handler]})

Every chain, model, tool and retriever step is anchored, with LangChain's run_id and parent_run_id tree committed alongside a per-run seq and prev_event_id. A missing event leaves a hole in seq and a moved one breaks the chain, so the trail is deletion-evident and reorder-evident.

Four things decide whether your integration is correct, so they sit here rather than in a guide:

• The with block raises on a gap. Leaving it out anchors what it can and walks past what it cannot, and you find out when an auditor asks. Use raise_on_gap=True to stop the agent instead.
• The whole step is committed, prompts, outputs, tool input and output. It stays with you. on_event watches what is committed and cannot change it.
• A file a tool returns gets its own record, name, size and hash, with no setup. The file's bytes are never stored, not in the log store and not in the bucket. A file the SDK cannot read becomes a langchain.artifact_unreadable event with its reason, because silence is how files go unrecorded on a run that reports success.
• Transient failures are retried; a 4xx is not. The plane has said the envelope is wrong, and repeating it is a slower failure rather than a recovery.

For the event vocabulary, the promoted fields, and worked examples, see Trace a LangChain agent.

Hand over a pack

When a compliance person asks for one agent's evidence over one period, the SDK assembles it in one command, with no Node installed:

export SANNING_API_KEY=ANCHOR_READ_KEY   # the key needs the `anchor:read` scope

sanning-anchor bundle \
  --agent claims-triage \
  --from 2026-06-01 --to 2026-06-30 \
  --logs ./logstore \
  --out claims-triage-2026-06.zip

Replace ANCHOR_READ_KEY with a key from the console carrying anchor:read. There is no flag for it: a credential in argv lands in shell history, and this is a command people paste into tickets. A key missing the scope is reported as a scope to widen, never as an absence of evidence.

sanning-anchor --help prints that reference, the exit codes, and the offline command that checks what the verb produced.

That writes one zip: a signed sanning.stamp.evidence/v1 bundle.json beside logs/<event id>.json. Proofs come from the Sanning index; the raw bytes come from your log store and never left it. The verb verifies the whole pack offline before it writes anything, so a pack that would fail at the auditor is never produced (exit 1, no file).

A stamp settles after it seals. For the first minutes of its life an interval stamp has not reached the public record, and a pack resting on one cannot be verified offline by whoever receives it. The verb says so and exits 1, the same way it does for records that are not stamped yet, and the message names the interval it is waiting for: run the command again in a few minutes. Your records are anchored, retained and stamped throughout, and nothing about them is wrong.

It also refuses to assemble a short pack, in two cases, because a recipient cannot tell a short pack from a complete one:

• Records whose record object is missing from your store make subject.producer_id unknowable, and one of them may be this agent's.
• Records that are anchored but not yet stamped have no inclusion proof, so a pack built now omits them and says so nowhere inside itself. The stamper seals on an interval, and running again once it has is usually the whole fix. --allow-unstamped assembles anyway, and then the summary tells you the pack is short so you can say so in the cover note.

No signing key is required or accepted. The container is sealed with a one-time assembly key, and every event inside already carries its producer's own signature. Fulfilling an evidence request is not a key-custody event.

Verify a pack

Verification lives in sanning-proof and needs no account, no key and no network. In Python the kernel is a library and ships no console script:

import json, pathlib
from sanning_proof import verify_evidence_bundle

pack = pathlib.Path("pack")
verdict = verify_evidence_bundle(
    json.loads((pack / "bundle.json").read_bytes()),
    content={p.stem: p.read_bytes() for p in (pack / "logs").glob("*.json")},
)
verdict.status  # "verified"

Whoever receives your pack does not need this SDK. For what a verdict proves, and the four things it does not claim, see Verify.

Parity with the TypeScript SDK

sanning-anchor and @sanning/anchor produce the same signed bytes for the same event, and the same signed pack body, byte for byte, for the same pack, so a mixed fleet hands over one pack. Both are gated against the same pinned corpus for the envelope, and against an oracle that imports neither SDK for the hand-over pack, so neither language can pass by agreeing with the other.

The LangChain adapters commit JSON.stringify(payload), which json.dumps is not, so this package reimplements it against a cross-language corpus generated from the real JSON.stringify.

One case refuses rather than diverges: an integer outside ±(2⁵³−1), a set, a reference cycle. JavaScript would round the first one, and two different 64-bit trace ids can round to the same double, which is a false integrity verdict rather than a formatting difference. So it fails at anchor time, while you can still fix it, rather than at verification, when the record is already sealed. Convert the value before anchoring it.

Development

pip install -e ".[dev]"
black --check src tests
pytest -q

MIT licensed.