Python

fireweave is the Fireweave server SDK for Python. It evaluates control points and registers targets — the two v1 capabilities. The wire protocol still uses the parameter name flagKey.

Supported versions

From pyproject.toml:

	Value
Package	`fireweave` 2.3.0
Python	`>=3.10`
Runtime dependencies	none
Extra	`dev` (`pytest>=8`) only

There is no [openfeature] extra and no [posthog] extra. Do not run those install commands.

Install

pip install fireweave

For local checkout development:

git clone https://github.com/FireWeave-HQ/fireweave-sdk && cd fireweave-sdk
python -m venv .venv
.venv/bin/pip install -e 'sdks/python[dev]'

Initialize

init_fireweave is the single entry point. mode is required and never inferred. Init raises ConfigurationError when mode is missing, remote credentials are blank, api_url fails the host allowlist, or local mode is combined with credentials.

from fireweave import EvaluationContext, init_fireweave

client = init_fireweave(mode="local", local={"control_points": {"new-checkout": True}})

enabled = client.control_points.get_boolean_value(
    "new-checkout", False, EvaluationContext(targeting_key="user_42")
)
print("new-checkout:", enabled)

client.shutdown()

Production — pass credentials explicitly. The SDK reads no environment variables:

import os
from fireweave import init_fireweave

client = init_fireweave(
    mode="remote",
    api_key=os.environ["FW_PROJECT_API_KEY"],
    api_url=os.environ["FW_API_URL"],
)

FireweaveClient is a context manager: with init_fireweave(mode="local") as client:. Lower-level construction:

from fireweave import FireweaveClient, FireweaveRuntime, InMemoryAdapter

adapter = InMemoryAdapter({
    "new-checkout": {"enabled": True, "variant": "on", "value": True},
})
runtime = FireweaveRuntime(adapter)
runtime.initialize()
client = FireweaveClient(runtime)

The async fireweave.aio / AsyncFireweaveClient surface is gone.

Configuration and authentication

Remote mode speaks POST /v1/flags/evaluate and POST /v1/targets/register. Auth is Authorization: Bearer <key>.

Option	Mode	Description
`api_url`	`remote`	fw-server base URL (required)
`api_key`	`remote`	Fireweave project key (required)
`allowed_hosts`	`remote`	SSRF allowlist override
`local.control_points`	`local`	Seeded boolean map
`local.log`	`local`	Sink for the `[fireweave:local]` register_target trace

https off-loopback; http on loopback only. A literal "*" disables host pinning. See Configuration and auth.

Targets

register_target lives on the client.

from fireweave import RegisterTargetOptions

result = client.register_target(
    "user_42",
    RegisterTargetOptions(kind="user", properties={"plan": "pro", "region": "eu-west"}),
)
print(result.ok, result.error)

RegisterTargetOptions: kind ("user" or "device"), properties, environment. Returns ok=False rather than raising. In local mode the adapter records the target in-process and traces the call. InMemoryAdapter does not implement registration. See Targeting and targets.

Control points

client.control_points is the product API. client.flags is the same object. The alias shares identity. On first access Python emits one DeprecationWarning per process. FlagType: BOOLEAN, STRING, NUMBER, OBJECT. There is no separate integer/float type in v1.

from fireweave import EvaluationContext, FlagType

ctx = EvaluationContext(targeting_key="user_42", attributes={"tier": "gold"})

on = client.control_points.get_boolean_value("new-checkout", False, ctx)
theme = client.control_points.get_string_value("checkout-theme", "classic", ctx)
ratio = client.control_points.get_number_value("discount", 0.0, ctx)

decision = client.control_points.get_boolean_details("new-checkout", False, ctx)
print(decision.value, decision.reason)

general = client.control_points.evaluate(
    "new-checkout", FlagType.BOOLEAN, False, ctx,
)

Nine methods: get_boolean_value, get_string_value, get_number_value, get_object_value, get_boolean_details, get_string_details, get_number_details, get_object_details, evaluate. Evaluation never raises. get_integer_value is a deprecated alias of get_number_value. It still works and logs one DeprecationWarning per process. Use get_number_value. See Control points.

Adapters

Adapter	Import	Use
`FireweaveRemoteAdapter`	`from fireweave import FireweaveRemoteAdapter`	Production fw-server
`FireweaveLocalAdapter`	`from fireweave import FireweaveLocalAdapter`	Dev `control_points` boolean map
`InMemoryAdapter`	`from fireweave import InMemoryAdapter`	Tests / fixtures

See Adapters.

Errors

ErrorKind has the same 15 PascalCase kinds. Concrete subclasses include NotReadyError, FlagNotFoundError, TypeMismatchError, InvalidContextError, TargetingKeyMissingError, AuthenticationError, AuthorizationError, RateLimitedError, TimeoutError_, NetworkError, BackendUnavailableError, MalformedResponseError, UnsupportedCapabilityError, ConfigurationError, AlreadyClosedError, InternalError. Evaluation never raises. Init can raise ConfigurationError. See Errors.

Testing

InMemoryAdapter fixture fields used in tests: type, enabled, value, variant, optional matchAttribute. Local mode is enough for an offline boolean seed. The repo test-server does not implement POST /v1/targets/register. See Testing.

Shutdown

client.shutdown()  # never raises; idempotent

See Initialize, ready, shutdown.

Not in this SDK

fireweave[openfeature] or fireweave[posthog]
FireweaveProvider / make_fireweave_local_provider
releases, exposures, signals, capabilities, guardrails
Environment-variable auto-read
AsyncFireweaveClient / fireweave.aio
A camelCase controlPoints namespace (Python is control_points)

Quickstart

Offline evaluate in every language.

Compatibility

Seven-language surface and the 65×7 aggregate.

Get Started

SDKs

Concepts

Production

CLI

Terraform

Testing

Troubleshooting

Migration

Reference

Supported versions

Install

Initialize

Configuration and authentication

Targets

Control points

Adapters

Errors

Testing

Shutdown

Not in this SDK

Next

Quickstart

Compatibility

​Supported versions

​Install

​Initialize

​Configuration and authentication

​Targets

​Control points

​Adapters

​Errors

​Testing

​Shutdown

​Not in this SDK

​Next

Quickstart

Compatibility

Supported versions

Install

Initialize

Configuration and authentication

Targets

Control points

Adapters

Errors

Testing

Shutdown

Not in this SDK

Next