Configuration

Settings — which backend to build — comes from SYSTEM_ONE_* environment variables or a .env file in the working directory. Everything the backend itself needs lives in a config object, read from the same environment when you do not pass one:

SystemOne(model="jev-latest")  # the model override
SystemOne(HTTPConfig(base_url="https://my-host", model="mine", timeout=30))

Unknown keys in the environment are ignored, so SYSTEM_ONE_* can live alongside everything else in your .env.

Variable	Default	Notes
SYSTEM_ONE_BACKEND	http	http or onnx
SYSTEM_ONE_MODEL	the config's default_model	required by plain http; an explicit model= wins
SYSTEM_ONE_BASE_URL	—	required by plain http; the presets set their own
SYSTEM_ONE_PATH	/v1/systemone
SYSTEM_ONE_API_KEY	—	required by TypesafeConfig / OpenRouterConfig
SYSTEM_ONE_TIMEOUT	10.0	seconds
SYSTEM_ONE_MAX_RETRIES	2	408, 429, 5xx only
SYSTEM_ONE_ONNX_DIR	onnx	holds <model>.onnx, <model>.json, tokenizer/

The resolved settings are on the agent:

agent.settings.backend
agent.backend.base_url

Three providers, one script

Vendor choice is a config class — the request body is identical, so moving between providers is one constructor argument.

from system_one import (
    HTTPConfig,
    ONNXConfig,
    OpenRouterConfig,
    SystemOne,
    TypesafeConfig,
)

SystemOne(TypesafeConfig())  # hosted jev, $SYSTEM_ONE_API_KEY
SystemOne(OpenRouterConfig())  # same body, different endpoint
SystemOne(HTTPConfig(base_url="https://my-host", model="mine"))
SystemOne(ONNXConfig())  # local graph, no network, no key

Fastino's hosted GLiDE is a plain HTTPConfig too — see Fastino GLiDE.

SYSTEM_ONE_BACKEND=onnx picks the local backend without naming a config, and keyword arguments patch the config: SystemOne(model="x") or SystemOne(ONNXConfig(), onnx_dir="elsewhere"). SystemOne(using=...) skips config entirely and takes a backend instance — see Backends.

Lifecycle

Agents and backends have no close. An HTTP backend builds its own httpx2 client unless you pass one with client=; a client you pass stays yours to close — see Bringing your own client.

A long-lived agent is the intended shape — build one per process, not one per request.