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lucairn — Python SDK

Client for Lucairn — privacy-preserving AI gateway.

Status

1.1.1. Ships alongside the TypeScript SDK and behaves identically at the observable level. See the monorepo README for the full SDK index.

Migration from the previous release: the package was previously published under a different name (pre-1.0). For one minor-version cycle, an in-tree compatibility shim re-exports every public symbol under its previous name and emits a DeprecationWarning on import. To migrate, change your imports to the new top-level names — the rename map and an example are below.

# old (still works for one minor cycle, with DeprecationWarning):
from theveil import TheVeil, TheVeilConfig

# new:
from lucairn import Lucairn, LucairnConfig

Install

pip install lucairn

Requires Python 3.10+.

Quickstart

from lucairn import Lucairn, LucairnConfig

client = Lucairn(LucairnConfig(api_key="lcr_live_..."))

# Proxy a prompt through the Lucairn gateway (split-knowledge routing).
response = client.messages({
    "prompt_template": "Summarize the following in one sentence: {text}",
    "context": {"text": "Long input..."},
    "model": "claude-sonnet-4-6",
    "max_tokens": 256,
})

Privacy receipts: free vs Pro tier paths

Every messages() call generates a privacy receipt witnessed by the gateway. Two surfaces exist for that receipt, and which one your code should consume depends on your tier:

  • get_certificate_summary(request_id) — returns a human-readable HTML summary (DPO-friendly). Available on every tier including Developer (free).
  • get_certificate(request_id) + verify_certificate(cert, keys) — fetches the raw JSON certificate and verifies the witness's Ed25519 signature over its canonical signed subset. Pro tier and above.

If a Developer-tier key calls get_certificate(), the gateway returns HTTP 403 with {"error":"tier_insufficient","hint":"Contact sales to upgrade."}, surfaced by the SDK as LucairnHttpError with err.status == 403.

Developer tier (free) — render the HTML summary

from lucairn import Lucairn, LucairnConfig, LucairnHttpError

client = Lucairn(LucairnConfig(api_key="lcr_live_..."))

response = client.messages({
    "prompt_template": "Hello {name}",
    "context": {"name": "Example Person"},
    "model": "claude-sonnet-4-6",
    "max_tokens": 1024,
})

# `response.request_id` is populated on every tier (Developer / Pro / Enterprise).
# Pro/Enterprise responses additionally expose `response.veil.summary_url` if you
# want the summary URL directly without an extra fetch.
request_id = response.request_id

try:
    summary_html = client.get_certificate_summary(request_id)
except LucairnHttpError as err:
    if err.status == 503:
        # Veil Witness temporarily unavailable; retry later.
        return
    raise
# Display summary_html in a sandboxed iframe or save for the DPO.

Pro tier and above — fetch + verify the JSON certificate

On Pro and Enterprise tier responses the gateway adds a veil block (accessible as response.veil.summary_url and response.veil.certificate_url). Pro and Enterprise keys can also fetch the raw certificate and verify the witness Ed25519 signature locally for a programmatic audit trail.

from lucairn import Lucairn, LucairnConfig, VerifyCertificateKeys, LucairnHttpError

client = Lucairn(LucairnConfig(api_key="lcr_live_..."))

try:
    cert = client.get_certificate(request_id)  # 200 on Pro/Enterprise; 403 on Developer (free)
except LucairnHttpError as err:
    if err.status == 202:
        # Certificate not yet assembled; retry after err.body["retry_after_seconds"].
        return
    if err.status == 403:
        # Developer (free) tier — use get_certificate_summary() instead.
        return
    raise

keys = VerifyCertificateKeys(
    witness_key_id="witness_v1",
    witness_public_key="<base64 of raw 32-byte Ed25519 public key>",
)
result = client.verify_certificate(cert, keys)
print(result.overall_verdict, result.anchor_status)

Public API

Lucairn(config: LucairnConfig)

Constructor validates every input up front:

  • api_key must be a Lucairn key (lcr_live_...) or a legacy dsa_... key.
  • base_url must be http:// or https://; defaults to https://gateway.lucairn.eu.
  • timeout must be a positive finite number of seconds (default 30.0). TS SDK equivalent is timeoutMs (milliseconds) — Python uses seconds to match httpx / requests / openai-python / anthropic-python.

client.messages(params, options=None)

POST to /api/v1/proxy/messages. Returns a discriminated union:

  • ProxySyncResponse — terminal result (gateway returned 200).
  • ProxyAcceptedResponse — async processing receipt (gateway returned 202, body status: "processing"). Poll the status_url until completion.

client.get_certificate(request_id, options=None)

GET /api/v1/veil/certificate/{request_id}. Pro tier or above — Developer (free) tier returns HTTP 403 tier_insufficient, surfaced as LucairnHttpError with err.status == 403.

Happy-path returns a VeilCertificate. Gateway-side pending (certificate not yet assembled, or unknown request_id — the gateway does not distinguish) surfaces as LucairnHttpError with status=202 and a body {"status": "pending", "retry_after_seconds": 30, ...} so the happy-path return stays narrow. Inspect err.body["retry_after_seconds"] for the retry signal.

No auto-verification — chain client.verify_certificate() explicitly.

client.get_certificate_summary(request_id, options=None)

GET /api/v1/veil/certificate/{request_id}/summary. Available on every tier including Developer (free). Returns the DPO-friendly HTML summary as a UTF-8 str. Per the gateway source the pending case renders an HTML body at HTTP 200 (not a 202 wrapper), so the SDK passes the rendered HTML straight back to the caller.

client.list_audit_events(opts=None)

GET /api/v1/audit/export. Returns an AuditExportResponse with the customer's audit events for the requested lookback window:

from lucairn import AuditExportOptions

resp = client.list_audit_events(AuditExportOptions(days=7, type="proxy.completed"))
print(resp.tier, resp.total_events)
for e in resp.events:
    print(e.timestamp, e.event_type, e.request_id)
  • days: int 1..90 (gateway default 30, max 90).
  • type: optional event-type filter.
  • 503 audit_export_unavailable (tier-gated; not enabled for the calling customer) raises LucairnHttpError with err.status == 503 and err.body["code"] == "audit_export_unavailable".

client.verify_certificate(cert, keys)

Verify a certificate's witness Ed25519 signature against the certificate's canonical-JSON signed subset. Returns VerifyCertificateResult on success. Raises LucairnCertificateError with one of five reasons on failure:

reason condition
malformed cert shape invalid, gateway invariant broken, or unknown verdict
unsupported_protocol_version protocol_version != 2
witness_mismatch keys.witness_key_id != cert.witness_key_id
witness_signature_missing empty or whitespace-only witness_signature
invalid_signature Ed25519 verify failed, or key input malformed

External RFC 3161 timestamp + Sigstore Rekor transparency-log verification are out of scope for this release (pending upstream gateway fixes).

lucairn.get_client_id(cert)

Module-level helper returning cert.client_id (the org-scoped correlation field added by W2A-B1) or None if the certificate predates the change. The field is unsigned metadata at the witness signable layer — tamper evidence flows indirectly through the bridge claim's bridge-signed canonical_payload.

Error hierarchy

All SDK errors inherit from LucairnError:

  • LucairnConfigError — bad constructor input or per-call option.
  • LucairnHttpError — gateway returned non-2xx (or 202 from get_certificate); exposes .status and .body.
  • LucairnResponseValidationError — gateway returned 2xx but the body doesn't fit the declared response type (typically a gateway bug or version skew); exposes .body (raw response). The underlying pydantic.ValidationError or ValueError is preserved on __cause__ for field-level inspection.
  • LucairnTimeoutError — request exceeded timeout.
  • LucairnCertificateError — verify_certificate failed; exposes .reason and (when available) .certificate_id.

Catch LucairnError to handle all SDK errors uniformly.

Behavioural parity with TS

This SDK is cross-language byte-equivalent to the TS SDK for canonical_json and verify_certificate. The Go-assembler-signed cert fixture (cert-go-signed-reference.json) verifies identically in both.

Intentional divergences where TS semantics don't port cleanly to Python:

  • Timeout: seconds (Python) vs. milliseconds (TS). Validator shape identical (positive finite).
  • Abort/cancel: v1 sync Python has timeout only; no signal analogue. Cancellation arrives with the async client in a later arc.
  • Malformed 2xx body: TS passes through as raw text typed as VeilCertificate (thin transport); Python calls VeilCertificate.model_validate and, on a shape mismatch, raises the dedicated LucairnResponseValidationError — NOT LucairnHttpError. The Python class follows the established Python-SDK precedent (openai.APIResponseValidationError, anthropic.APIResponseValidationError): an HTTP 200 is not an HTTP error, and callers benefit from being able to catch "transport failed" separately from "body doesn't fit the declared type." TS's pass-through model remains the authoritative behaviour for the TS surface; Python fails earlier (at fetch) because Pydantic validates at deserialize-time, and the failure class names the reason precisely instead of lying via status=200.
  • Error .body type on over-cap: Python stores the preserved prefix as str (UTF-8-decoded with errors='replace') — idiomatic for Python SDK callers used to httpx.Response.text / .json(). The Go SDK stores .Body as []byte for the same case — idiomatic for Go callers used to resp.Body-style byte-slice access. Behaviour parity holds at the "the prefix is preserved, bounded, and diagnostic-readable" level; the representation is intentionally language-idiomatic, not byte-identical.
  • Literal JSON null body: when the gateway returns a 2xx with the literal null payload, the parsed body is Python None; the SDK falls back to the raw pre-parse text ("null") for LucairnResponseValidationError.body so callers can distinguish "gateway sent null" from "SDK forgot to populate the error body."

Development

cd python
pip install -e ".[dev]"
pytest

Tests include a byte-for-byte cross-check of Python canonical-JSON output against the Go assembler's reference hex, and end-to-end verification of a real Go-assembler-signed certificate. If either fails, the SDK's Ed25519 verify will silently produce invalid_signature on valid certs — do not skip or soft-fail those tests.

License

MIT — see LICENSE.