PHION Python client

Budget-safe synchronous x402 v2 client. It gets a non-paying quote, validates the origin, Base network, official USDC contract, PHION recipient and maximum amount, then delegates local signing and retry to the official x402 SDK.

Installing this package never authorizes a payment. A paid call requires an explicit PhionBuyer.call(...), a locally supplied wallet key and a SpendingPolicy. Use a dedicated low-balance wallet and set cumulative, call, expiry and service-path limits through SpendingMandate.

python -m venv .venv
. .venv/bin/activate
pip install -e .
export EVM_PRIVATE_KEY=0x... # dedicated agent wallet; never commit this value
python example.py

The example has a hard limit of 0.001 USDC and verifies the signed result.

The shortest verified workflow resolves first, then carries the resolution ID through the bounded paid call:

resolution = buyer.resolve(
    capability="inference",
    task="Return a one-sentence classification.",
)
candidate = next(
    (
        item for item in resolution["candidates"]
        if item.get("eligible") is True and item.get("serviceId") == "phion-inference"
    ),
    None,
)
if candidate is None:
    raise RuntimeError("no authorized candidate selected")
result = buyer.call(
    candidate["endpoint"],
    {"prompt": "Return a one-sentence classification."},
    mandate,
    trace={"resolution_id": resolution["resolutionId"]},
)
assert result["receipt_verified"] is True

resolve() is advisory: it never signs, pays or executes, and may honestly return ABSTAIN when evidence is incomplete. call() preserves the spending policy and quote checks and automatically verifies a signed receipt when a commercial result is returned. Receipt verification proves integrity and origin, not that arbitrary external source content is necessarily true.

The public MCP decision surface remains available without this package at https://phion.systems/mcp/decision; start with phion_resolve in PREFLIGHT mode when payment is not yet authorized.