fix(browser): Defer sending session envelope until browser is idle#21844
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logaretm
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Jun 29, 2026
When using the default `lifecycle: 'route'`, a navigation that happens before the deferred initial `whenIdleOrHidden` callback fires already starts and sends a new session. The deferred callback then re-sent that same (current) session, producing a duplicate envelope. Guard the deferred capture so it skips once a session has been sent, and mark the session as sent in the navigation handler. Co-Authored-By: Cursor Agent <cursoragent@cursor.com> Co-authored-by: Cursor <cursoragent@cursor.com>
Replace the inline `import()` type annotation in the browserSession unit test with a top-level type import to satisfy `consistent-type-imports`. Reorder the expected logs in the debug integration test: now that the initial session capture is deferred, the "Discarded session" warning is emitted after the `BrowserSession` integration is installed rather than before it. Co-Authored-By: Cursor Agent <cursoragent@cursor.com> Co-authored-by: Cursor <cursoragent@cursor.com>
The deferred browser session capture schedules a `whenIdleOrHidden` timer that calls `WINDOW.removeEventListener` when it fires. These nextjs tests stub a fake window with `addEventListener` but not `removeEventListener`, so the deferred timer threw an unhandled `TypeError` after the test. Stub and restore `removeEventListener` alongside `addEventListener`. Co-Authored-By: Cursor Agent <cursoragent@cursor.com> Co-authored-by: Cursor <cursoragent@cursor.com>
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mydea
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Jun 30, 2026
| let originalDocument: unknown; | ||
| let originalLocation: unknown; | ||
| let originalAddEventListener: unknown; | ||
| let originalRemoveEventListener: unknown; |
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yes, it needs to be pulled in because whenIdleOrHidden registers and removes event listeners
mydea
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Jun 30, 2026
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Uses the
whenIdleOrHiddencallback to send the initial session envelope when the browser has some idle time or at the latest, when the page is hidden. For old Safari versions, we fall back tosetTimeoutbut otherwise we userequestIdleCallback(both withinwhenIdleOrHidden).This should improve initial SDK initialization performance as well as reduce implicitly caused overhead (like increased LCP), due to the eagerly sent network request.
This should be a fairly safe change to make. I don't think we risk loosing a lot of sessions with it, given RIC should fire relatively soon. At the same time, I'm curious how much it improves lighthouse scores (which we can check easiest after merging).
closes #21817