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FireWeave SDKs evaluate control points, optionally register targets, drive a release lifecycle, and record exposures and signals. Your application authenticates with a FireWeave project key and talks to fw-server. OpenFeature and the wire protocol still use the parameter name flagKey; the product name is control point.
The SDK is pre-release. As of 2026-08-17, npm latest for @fireweaveai/sdk is 2.1.0, @fireweaveai/web-sdk@2.1.0 is on npm, and PyPI has fireweave 0.1.0. Pin Node @2.1.0 — 2.0.0 is still on npm and still ships a direct PostHog adapter and ./posthog. The Go module and Java ai.fireweave:* (0.1.0-SNAPSHOT) remain unpublished (checkout / mvn install only). See Quickstart.

Quickstart

Install, initialize, evaluate a control point, record an outcome, and shut down — offline first, with real APIs.

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SDKs

Five packages share one architecture: FireweaveProvider and FireweaveClient sit on FireweaveRuntime, which talks to a BackendAdapter.

Node.js, Bun, and Deno

@fireweaveai/sdk — controlPoints, registerTarget. npm latest is 2.1.0; pin it. 2.0.0 still has PostHog / ./posthog.

Python

fireweave — snake_case control_points and register_target. PyPI 0.1.0: pip install 'fireweave[openfeature]'.

Go

github.com/FireWeave-HQ/fireweave-sdk/sdks/go — Flags().Evaluate only. No registerTarget on master.

Java

ai.fireweave:* — evaluate / boolean and string helpers. No env auto-read; close() does not flush.

Browser

@fireweaveai/web-sdk — synchronous reads, identify, STALE on prefetch timeout. npm 2.1.0; no env.

Compatibility

Type split, adapter matrix, and language gaps (register, namespaces, flush).

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What you can do

These capabilities are implemented in the five packages (language differences are called out on the SDK pages):
  • Evaluate boolean, string, numeric, and object decisions. Evaluation returns a default on failure and does not throw.
  • OpenFeature providers in every language, so call sites can use getBooleanValue / language equivalents with flagKey.
  • Targets — Node registerTarget, Python register_target, Web identify. Go and Java have no registration API; pass targetingKey (and attributes) on each evaluate.
  • Releases — setContext / start / complete / fail.
  • Exposures — record / flush. Evaluate-path emission is opt-in (sendExposure defaults false).
  • Signals — health, error, metric, and outcome (recordOutcome / language equivalent).
  • Capabilities — capabilities.get() reports what this build and adapter can do. Guardrails are a typed stub (guardrails: false).
This site does not document wrap workflows, fw.isOn, working client-side guardrails, or OpenFeature Tracking (spec §6). Those are absent or unverified against the SDK.

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Architecture and concepts

How it works

Evaluate, register, capture — the runtime path without console ramp or wrap stories.

Architecture

Provider + Client → Runtime → Adapter, lifecycle states, and the three fw-server paths.

Core concepts

Control points, targeting, releases, exposures, signals, capabilities, adapters.

OpenFeature

Providers, resolvers, and the flagKey boundary. Extensions stay on FireweaveClient.

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Production, troubleshooting, reference

Configuration and auth

FW_API_URL, FW_PROJECT_API_KEY, Bearer auth. Java and Web do not read the environment.

Lifecycle

Initialize, READY / STALE, shutdown. Java close() does not flush exposures.

Errors

Fifteen error kinds and how they map onto OpenFeature codes.

Troubleshooting

Defaults that look like “off,” missing targeting keys, and Go/Java checkout installs.

Package index

Package names, peers, and what is actually published.

Node 2.0 → 2.1

Breaking changes from Node 2.0.0 (PostHog / ./posthog) to published 2.1.0.
Start with the Quickstart if you want a first evaluate in one sitting.
Last modified on August 18, 2026