Options.

endpoint, timeoutMs, retries, logger, transport, onResolution.

Every option is documented in the shipped type declarations (dist/index.d.ts). These are the ones worth knowing before you read them.

Option	Default	Notes
`endpoint`	`https://edge.splitch.dev`	override for self-hosted or preview targets
`timeoutMs`	`5000`	per-call timeout; a timeout is an ERROR, not a default
`retries`	`0`	must stay `0`; reuse `idempotencyKey` instead
`logger`	`console`	receives every fail-loud report
`transport`	built-in `fetch` adapter	injectable seam for tests
`fetch`	the global `fetch`	injectable seam for tests and custom agents
`now`	`Date.now`	injectable epoch-ms clock
`revalidateMs`	`60000`	Exposure-dedup window; a new Run is detected within it
`seenSetMaxSize`	bounded default	max entries in the local Exposure-dedup cache
`onResolution`	unset	observability hook; see below

onResolution

onResolution(flagKey, details) is called with every resolution the real user path produced, for observability sinks that want to know which Flags were active. It is never called for peekVariant or verify, because those fire no Exposure and reporting them would claim a resolution the user never received.

It is called synchronously and never awaited, and a throwing reporter is not caught: an observability sink that fails should fail where it fails rather than be swallowed into a silently degraded evaluation. Sentry ships a ready-made reporter for this hook.

Options that throw

These are validated at construction so a misconfigured client fails on the first line rather than corrupting Exposure data at request time.

SDK_RETRIES_INVALID: retries is anything but 0.
SDK_SEEN_SET_MAX_SIZE_INVALID: the dedup seen-set bound is not a positive integer.
SDK_SEEN_SET_TTL_INVALID: the dedup TTL is not a positive duration.

Every SDK topic

Install: Add @splitch/sdk, read the export surface, and get one Flag resolving.
Credentials: Client Key evaluates, API Key peeks. Pass exactly one.
The six methods: Which calls fire an Exposure, and which credential each needs.
evaluateAll and bootstrap: Resolve every Flag once, then hydrate a browser client without another fetch.
idempotencyKey: The SDK generates a key per call. Supply one when your application manages retries.
Failure behavior: Server evaluation never throws on a platform failure and never hides one. Empty or non-string explicit idempotency keys throw, as does UUID generation when the runtime cannot provide it. Peek throws, and so does a browser read before init().
Exposure dedup: Repeat evaluations replay locally. Run boundaries do not.
Options: endpoint, timeoutMs, retries, logger, transport, onResolution.
Node.js: Evaluate on the request path from a Node server, with one client for the process.
Browser client: Fetch once, read Flags synchronously, and fire Exposures on first use.
React bindings: Provide one initialized browser client and subscribe each hook to one Flag.
Convex: Local Flag evaluation inside Queries and Mutations, with transactional Exposures.
Cloudflare Workers: Deploy an integration Worker into your own account and evaluate over a service binding.
Sentry: Feed both halves of Sentry's suspect-flag detection: change tracking and evaluations.