Sentry: events rejected for invalid DSN or project

TL;DR

Enable SDK debug output (debug: true in init) and watch for transport errors on startup. Set the exact DSN from the project settings, redeploy, trigger one error, and confirm it appears in that project's issue stream within a minute.

Steps

1. Enable SDK debug output (debug: true in init) and watch for transport errors on startup. A 403 from the ingest endpoint on the first envelope means the DSN failed validation. Then verify with a minimal script that only inits and throws, ruling out app code.
2. Set the exact DSN from the project settings, redeploy, trigger one error, and confirm it appears in that project's issue stream within a minute. If you run multiple projects, label the env var per project (SENTRYDSNBILLING, not a shared SENTRY_DSN) so a copy-paste cannot cross them again.

When to use

You are seeing this: No error in your app, nothing in the issue stream. Use this skill when you run into "Sentry: events rejected for invalid DSN or project".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Researched against live Sentry docs 2026-09-26. The quotas page (docs.sentry.io/pricing/quotas/) states: Before completing any of these evaluations, Sentry confirms that each event includes a valid DSN and project as well as whether the event can be parsed. If any of these items are missing or incorrect, the event is rejected. The Node.js and Python setup pages show the DSN as the __PUBLICDSN___ placeholder in init. The Next.js guide documents withSentryConfig org/project for build-time uploads, a separate credential path from the runtime DSN.