Diagnose: no events arriving in Sentry at all

# Diagnose: no events arriving in Sentry at all

Work top to bottom. Stop at the first step that fails.

## 1. Did init run?

Set `debug: true` in init. If you see no SDK output at startup, init never ran or the DSN is empty. In Node, confirm the `--import ./instrument.js` flag is in the actual start command. In Python, confirm init is in the entry point, not behind an import that never executes.

## 2. Is the DSN valid?

With debug on, trigger one error and watch the transport. 403 means the DSN or project failed validation: re-copy from Client Keys (DSN). Connection failures mean the host is wrong or egress is blocked.

## 3. Is something eating the envelope in transit?

Adblockers and privacy extensions block ingest hosts in browsers. Corporate egress proxies block them on servers. Test from curl on the server and from a clean browser profile. If one works, it is the network, not the SDK.

## 4. Is the event filtered client-side?

`beforeSend` returning undefined drops the event silently. `ignoreErrors` matching too broadly, `denyUrls`, or inbound filters in project settings all discard before ingest. Temporarily remove `beforeSend` and retest.

## 5. Is it sampled out?

For transactions: no sample rate means no transactions, period. For errors: check the quota. An exhausted error quota 429s everything with no client-side error.

## 6. Are you looking in the right place?

Wrong project, wrong org, wrong environment tab. The events may be arriving exactly where the config points, which is not where you are looking.

## Verify

A minimal script (init + throw, run from a file) producing one issue in the expected project within a minute. If the minimal case works and the app does not, the difference between them is the bug; bisect the app config toward the minimal case.