sernixa 0.2.0

Sernixa Python SDK — governed tool and agent execution with MCP call-gate support

Sernixa Python SDK

Sernixa gates Python function execution through a deterministic approval engine. The backend decides whether an action is allowed, auto-approved, blocked, or pending human review; the SDK executes the wrapped business function locally only after an approved-style decision.

The SDK is intentionally small: it does not execute business logic in the Sernixa backend, and it does not pretend to be a full agent framework. It gives you low-friction interception points for plain Python, LangChain, CrewAI, and MCP-style tool boundaries.

Quickstart

# From the repository root (not yet published to PyPI):
pip install -e packages/sernixa
export SERNIXA_BASE_URL=http://localhost:8000
export SERNIXA_API_KEY="$YOUR_LOCAL_DEV_TOKEN"

import sernixa

@sernixa.intercept(
    intent_id="customer-notes",
    risk_level="LOW",
    operation_class="read",
    data_sensitivity="internal",
    systems_touched=["postgres"],
    metadata={"ticket": "DEMO-1"},
)
def summarize_customer(customer_id: str) -> str:
    return f"summary for {customer_id}"

print(summarize_customer("cus_123"))

If Sernixa returns approved, auto_approved, or executed, the function runs locally. If it returns pending_review, the SDK polls until a terminal decision or timeout.

Configuration

• SERNIXA_BASE_URL: Sernixa API URL. Defaults to http://localhost:8000.
• SERNIXA_API_KEY: bearer token for the API.
• SERNIXA_POLL_INTERVAL_SECONDS: approval poll interval. Defaults to 2.
• SERNIXA_POLL_TIMEOUT_SECONDS: approval wait timeout. Defaults to 600.
• SERNIXA_TIMEOUT_SECONDS: per-request HTTP timeout. Defaults to 10.
• SERNIXA_MAX_RETRIES: retries for transient network errors, 429, and 5xx. Defaults to 2.
• SERNIXA_MAX_ASYNC_IN_FLIGHT: maximum concurrent async SDK HTTP requests per event loop. Defaults to 20.
• SERNIXA_SDK_DLP_MODE: metadata DLP mode. Defaults to mask; use warn, block, or off intentionally.
• SERNIXA_CAPTURE_ARGUMENTS: set to true to include function argument values in submitted metadata. Defaults to false.
• SERNIXA_LOG_LEVEL: optional SDK logger level such as INFO or DEBUG.
• SERNIXA_DEBUG: set to true for verbose SDK request/decision logging.

You can also configure a client directly:

import os
from sernixa import Client

client = Client(
    base_url="http://localhost:8000",
    api_key=os.environ["SERNIXA_API_KEY"],
    poll_interval=1,
    poll_timeout=120,
    timeout_seconds=10,
    max_retries=2,
    max_async_in_flight=20,
)

Intercepting Functions

@client.intercept(
    intent_id="billing-adjustment",
    risk_level="HIGH",
    operation_class="financial",
    data_sensitivity="financial",
    systems_touched=["stripe", "postgres"],
)
def adjust_invoice(invoice_id: str, amount_cents: int) -> None:
    ...

High and critical risk actions are never auto-approved by Sernixa. They remain pending review even when similar low-risk actions have a strong approval history.

Async Functions

The same decorator works on coroutines:

@client.intercept(
    intent_id="agent-read",
    risk_level="LOW",
    operation_class="read",
    data_sensitivity="internal",
    systems_touched=["vectordb"],
)
async def run_agent(query: str) -> str:
    return await agent.ainvoke(query)

Async clients reuse one httpx.AsyncClient per event loop and cap concurrent SDK requests with SERNIXA_MAX_ASYNC_IN_FLIGHT. Long-running async services should close reusable sessions during shutdown:

async with Client() as client:
    await protected_tool()

# or
client = Client()
...
await client.aclose()

Decision Handling

from sernixa import is_approved_status, is_terminal_status

assert is_approved_status("auto_approved")
assert is_terminal_status("rejected")

The SDK raises explicit exceptions for reviewer and policy outcomes:

from sernixa.exceptions import (
    SernixaBlockedError,
    SernixaConfigurationError,
    SernixaExpiredError,
    SernixaRateLimitError,
    SernixaRejectedError,
    SernixaTimeoutError,
    SernixaValidationError,
)

try:
    adjust_invoice("inv_123", 1000)
except SernixaBlockedError as exc:
    print(f"Blocked by policy: {exc.reason}")
except SernixaRejectedError as exc:
    print(f"Rejected by reviewer: {exc.reason}")
except SernixaExpiredError:
    print("Approval expired before a reviewer decided.")
except SernixaTimeoutError:
    print("SDK timed out waiting for a decision.")

Configuration and payload mistakes fail before the business function runs:

• SernixaConfigurationError: invalid base URL, timeout, poll, or retry settings.
• SernixaValidationError: malformed action metadata such as an empty intent_id, invalid risk_level, or non-JSON metadata.
• SernixaRateLimitError: the backend kept returning 429 after retries.

Extra Review Metadata

Use metadata for non-sensitive context that helps the approver understand the action:

@sernixa.intercept(
    intent_id="support-note",
    risk_level="LOW",
    operation_class="update",
    data_sensitivity="internal",
    systems_touched=["postgres"],
    metadata={"change_ticket": "SUP-1842", "env": "local-demo"},
)
def write_support_note(...):
    ...

Core governance fields such as risk_level and idempotency_key cannot be overridden by extra metadata.

By default, the SDK does not upload function argument values. It sends argument counts and keyword names only, and masks sensitive-looking metadata before the request leaves the process. To include full argument values for a trusted local debugging session, set SERNIXA_CAPTURE_ARGUMENTS=true; keep the default for shared development and production-like runs.

V3 Delegation Context

For local multi-agent workflows, create a delegation token through Sernixa and attach it while any delegatee agent runs protected tools:

from sernixa import Client, delegation_scope, with_delegation

client = Client()
token = client.create_delegation_token(
    delegator_agent_id="orchestrator-agent",
    delegatee_agent_id="worker-agent",
    scope=delegation_scope(
        max_risk_level="low",
        allowed_operation_classes=["read"],
        allowed_data_sensitivities=["internal"],
        resources={"repo": ["sernixa"]},
    ),
    tool_subset=["view-details"],
)

with with_delegation(
    agent_id="worker-agent",
    token_id=token["token_id"],
    signing_secret=os.environ["SERNIXA_REQUEST_SIGNING_SECRET"],
    chain_id=token["chain_id"],
    runtime_id="local-worker-runtime",
    service_identity="spiffe://local/agent/worker-agent",
):
    view_details()

The SDK signs each delegated request with a canonical envelope, timestamp, nonce, request body hash, key ID, and runtime identity metadata. Sernixa verifies the request signature, replay status, token signature, hash chain, expiry, delegatee identity, and scope before the existing approval logic runs.

LangChain Adapter

Use the decorator when you control the tool function:

from langchain.tools import tool
from sernixa.adapters import langchain_tool

@tool
@langchain_tool(
    intent_id="finance-tool",
    risk_level="HIGH",
    operation_class="financial",
    data_sensitivity="financial",
    systems_touched=["stripe"],
)
def transfer_funds_tool(amount_cents: int, destination_account: str) -> str:
    """Transfer funds after Sernixa approval."""
    ...

Use the object proxy when a tool object already exists:

from sernixa.adapters import secure_langchain_tool

protected_tool = secure_langchain_tool(
    existing_tool,
    intent_id="customer-lookup",
    risk_level="LOW",
    operation_class="read",
    data_sensitivity="internal",
    systems_touched=["crm"],
)

result = protected_tool.invoke({"customer_id": "cus_123"})

Install LangChain separately if you use the adapter:

pip install "sernixa[langchain]"

The proxy guards invoke, ainvoke, run, arun, and direct calls where the underlying tool exposes them. It forwards unknown attributes to the wrapped tool.

CrewAI Adapter

Use the decorator for plain functions that become CrewAI tools:

from sernixa.adapters import crewai_tool

@crewai_tool(
    intent_id="ticket-update",
    risk_level="HIGH",
    operation_class="update",
    data_sensitivity="internal",
    systems_touched=["ticketing"],
)
def update_ticket(ticket_id: str, note: str) -> str:
    return "updated"

Use the object proxy for existing CrewAI-style tool objects:

from sernixa.adapters import secure_crewai_tool

protected_tool = secure_crewai_tool(
    existing_tool,
    intent_id="crew-ticket-update",
    risk_level="HIGH",
    operation_class="update",
    data_sensitivity="internal",
    systems_touched=["ticketing"],
)

protected_tool.run("SEC-1842")

Install CrewAI separately if you use CrewAI itself:

pip install "sernixa[crewai]"

The SDK proxy supports the common run, _run, and direct-call execution shapes without requiring CrewAI as a hard dependency.

MCP Boundary Helpers

Sernixa does not implement the full MCP protocol in this SDK. The real support in this pass is an honest boundary wrapper for MCP-style tool dispatch:

from sernixa.adapters import McpToolBoundary

boundary = McpToolBoundary(server_name="workspace-mcp", toolset_id="toolset-prod")

def read_file(path: str) -> str:
    return open(path).read()

result = boundary.invoke(
    tool_name="read_file",
    arguments={"path": "/workspace/report.md"},
    handler=read_file,
    intent_id="mcp-read-file",
    risk_level="LOW",
    operation_class="read",
    data_sensitivity="internal",
    client_name="local-agent-host",
)

Place this at the host/router boundary before dispatching a tool call to the underlying MCP server/tool implementation. Planned next work is first-class MCP server middleware and protocol-aware request/response adapters.

Gateway Run Wrapper

SernixaGateway is the target high-level developer surface for governing an existing agent or MCP/tool run call without rewriting the agent. It wraps the current approval oracle and records gateway metadata on the action request.

from sernixa import SernixaGateway

gateway = SernixaGateway(
    api_key=os.environ["SERNIXA_API_KEY"],
    mcp_profile="prod-tools",
    enforce_ebpf=True,
)

result = gateway.run(agent.run, input=user_task)

enforce_ebpf=True does not start a collector by itself. Before execution, the SDK checks /ready and requires Flight Recorder runtime support outside local_demo. In local_demo, the action is still marked as requiring runtime evidence, but unsigned local-demo evidence must not be represented as production proof. Native protocol-aware MCP middleware remains a target design until implemented. The TypeScript package now exists in the monorepo for Node action gating and gateway readiness, but npm publication is not verified here.

State Model

• executed: Sernixa allowed the action and the SDK executed the local function.
• auto_approved: Sernixa policy allowed execution without human review.
• pending_review: the SDK is waiting for a reviewer and polling the approval.
• rejected: a reviewer denied the action; the SDK raises SernixaRejectedError.
• blocked: policy/security denied the action; the SDK raises SernixaBlockedError.
• expired: approval TTL elapsed; the SDK raises SernixaExpiredError.
• failed: backend replay/execution evidence failed; the SDK raises SernixaError.

Troubleshooting

• Action blocked: inspect exc.reason and the approval/audit page. Dangerous primitives and invalid signatures fail closed.
• SernixaValidationError: fix empty IDs, invalid risk levels, empty systems_touched, or non-JSON metadata.
• SernixaConfigurationError: check SERNIXA_BASE_URL, timeout, poll, and retry values.
• SernixaRateLimitError: reduce agent concurrency or increase backend limits for the environment.
• SernixaTimeoutError: the approval is still pending after SERNIXA_POLL_TIMEOUT_SECONDS.
• Browser works but SDK fails: verify SERNIXA_API_KEY and that the backend URL is reachable from the Python process.

Local And Hosted Configuration

Local demo:

export SERNIXA_BASE_URL=http://localhost:8000
export SERNIXA_API_KEY=e2e-admin
export SERNIXA_POLL_INTERVAL_SECONDS=1

Hosted or shared environment:

export SERNIXA_BASE_URL=https://sernixa.example.com
export SERNIXA_API_KEY="$SERNIXA_SERVICE_TOKEN"
export SERNIXA_TIMEOUT_SECONDS=10
export SERNIXA_MAX_RETRIES=2

Use real bearer tokens, HTTPS, shared nonce/rate-limit storage, and production KMS/HSM signing before treating a hosted environment as production.

Current backend handoff note: local SDK examples target a configured API. A production-like Sernixa backend must run behind the Auth.js/Google web session boundary, accept only the short-lived API JWT minted by the web app, and use Convex plus shared Redis for production runtime state.

TypeScript handoff note: the monorepo now includes packages/sdk as a real Node client for action gating, approval polling, typed errors, and gateway readiness checks. Python remains the fuller SDK for delegation request-envelope signing and framework adapters.

Release

Not yet published to PyPI. The package is build-validated and publication-ready. Use local editable install from this repository until the first PyPI release.

For local repository development, use editable install from the repo root:

pip install -e packages/sernixa

Local Examples

• examples/basic_auto_approval/: local walkthrough showing low-risk, repeated approval memory, and high-risk pending behavior.
• examples/multi_agent_delegation/: generic orchestrator/worker delegation token flow.
• examples/sernixa-sdk/: lower-level sync, async, LangChain, CrewAI, MCP boundary, Node gateway, and compose smoke examples.