Troubleshooting

webDeveloper

What to check when data is not arriving, the built-in diagnostics helpers, and the init behaviors that most often surprise people.

Updated August 12, 2026Reviewed August 5, 2026

Nothing is arriving#

Work down this list:

Check the console. init() never throws — on a bad config it logs [scalebun] init failed: … and leaves the SDK inert. That warning is your first clue.
Confirm both required fields. clientKey and apiBaseUrl are mandatory; a missing one leaves the SDK silently inert.
Call init() on the client. It must run in the browser, not during SSR, and as early as possible.
Check consent. With requireConsent: true, nothing is captured until setConsent(true) is called.
Check CSP. If the ingestion API is blocked by connect-src, requests never leave the browser. See Privacy & consent.

Diagnostics#

The SDK exposes live counters and a manual flush you can call from the console:

TypeScript

ScaleBun.sessionId;         // the current session id — quote this in a support ticketScaleBun.egressStats();     // { pending, dropped } across both lanesScaleBun.errorStats();      // captured, dropped-by-reason, by type, breadcrumb countScaleBun.networkStats();    // captured, by protocol, by failure, dropped, bodiesScaleBun.perfStats();       // transactions, dropped, resources, jank, sample rateScaleBun.analyticsStats();  // pending, dropped, sampledOut, flushes, sampleRateScaleBun.replay.stats();    // null when this session isn't being recordedScaleBun.watchdog.stats();  // null unless the watchdog is enabled
await ScaleBun.flush(); // force-send both lanes nowawait ScaleBun.close(); // flush and shut down

pending climbing while dropped stays at zero means egress is blocked, not that capture is broken — check the network tab and connect-src. dropped climbing means the queue is overflowing, which is a volume or connectivity problem rather than a configuration one.

A feature does nothing and reports no error#

Most "it silently does nothing" reports are one of these.

Symptom	Cause
A controller's methods do nothing, forever	It was read before `init()` resolved. Accessors return a no-op object rather than throwing. `await ScaleBun.whenReady()` first.
The inbox is always empty	`features.inbox` is off by default, and the disabled controller is a no-op.
In-app messages never render	Same, for `features.inapp2` — or an inline campaign with no registered slot, which falls back to a modal.
Push does nothing after `enablePush()`	`/scalebun-push-sw.js` is not served from your origin, or the call was not made from a user gesture.
`profiler.start()` returns `false`	The document is not served with `Document-Policy: js-profiling`.
No replay for a session	It was not sampled. `ScaleBun.replay.stats()` returns `null` — that is the answer, not a bug.
A segment-targeted campaign never shows	The visitor is still anonymous. Call `identify()` — segments cannot resolve without a user.
An inline message renders nowhere	The slot element unmounted without being unregistered, so it points at a detached node.

Things that surprise people#

Next#

Install & initialize — required fields and delivery.
Privacy & consent — consent and CSP.