Three lines to
your first flag.
Install the SDK, wrap the change, turn the dial. Everything else — targeting, rollouts, rollbacks — happens at runtime.
import { Rheostat } from "@rheostat/node"const rh = new Rheostat(process.env.RH_KEY)const useNewCheckout = await rh.flag("new-checkout", user)if (useNewCheckout) // 5% today, 100% on Fridayreturn renderCheckoutV2(cart)return renderCheckout(cart)
from rheostat import Rheostatrh = Rheostat(os.environ["RH_KEY"])use_new_checkout = rh.flag("new-checkout", user)if use_new_checkout: # 5% today, 100% on Fridayreturn render_checkout_v2(cart)return render_checkout(cart)
import "github.com/rheostat/go"rh := rheostat.New(os.Getenv("RH_KEY"))useNew, _ := rh.Flag(ctx, "new-checkout", user)if useNew { // 5% today, 100% on Fridayreturn RenderCheckoutV2(cart)}return RenderCheckout(cart)
import dev.rheostat.Rheostat;var rh = new Rheostat(System.getenv("RH_KEY"));boolean useNew = rh.flag("new-checkout", user);if (useNew) // 5% today, 100% on Fridayreturn renderCheckoutV2(cart);return renderCheckout(cart);
Terminal
$ npm i @rheostat/nodeadded 1 package in 1.2s$ rh flag create new-checkout✓ created new-checkout (off)$ rh rollout new-checkout 5%✓ 5% of users · 12 rules · live$ rh watch new-checkoutp95 212 ms · errors 0.02% · okNode
Python
Go
Java
Ruby
Rust
REST APIAn API that reads
An API that reads
like a sentence.
Every action in the dashboard is one call away. Versioned, idempotent and documented with runnable examples.
- GET
/v1/flagsList every flag in a project - POST
/v1/flagsCreate a flag with default rules - PATCH
/v1/flags/{key}/rolloutMove a flag to a new percentage - POST
/v1/flags/{key}/rollbackDial a flag back to 0% now - GET
/v1/runs/{id}/traceFetch an agent run with every span - DELETE
/v1/flags/{key}Archive a flag and its history
PricingPay for evaluations,
Pay for evaluations,
not seats.
Your first million evaluations every month are free. After that you pay for what the SDK actually asks — invite the whole team.
Estimated$240/ month
Start free Shipped this month.
Rollback rules now accept agent judge scores
Trigger a rollback when any judge in a run scores below your threshold.
Go SDK: zero-allocation flag evaluation
Hot paths evaluate a flag in 40 ns with no heap allocation.
MCP server for coding agents
Let your coding agent create, flip and clean up flags with your permissions.
Warehouse export to Parquet
Every evaluation and trace, partitioned by day, in your own bucket.
Built in the open,
with 18k developers.
- 18.4k
- GitHub stars
- 412
- contributors
- 2.1M
- weekly SDK downloads