Merge pull request #17127 from newrelic/add-browser-agent-v1.258.0

Browser Agent v1.258.0 Release Notes

src/content/docs/release-notes/new-relic-browser-release-notes/browser-agent-release-notes/browser-agent-v1.258.0.mdx

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+---
+subject: Browser agent
+releaseDate: "2024-04-29"
+version: 1.258.0
+features: ["Restructure AJAX Aggregate","Maintain calculated NR server time for session","Add harvestId to Session Replay payloads","JSErrors timestamped per harvest"]
+bugs: ["Clean up xhrWrappable","Prevent null CLS"]
+security: []
+---
+
+## v1.258.0
+
+### Features
+
+#### Restructure AJAX Aggregate
+Re-organization of the Ajax feature as part of agent maintenance. This has no expected impact on its functionality.
+
+#### Maintain calculated NR server time for session
+This update changes the agent to store the New Relic server time calculated when session tracking is enabled. This will prevent the agent from re-calculating server time on subsequent page loads, ensuring the timeline view of events in New Relic is more accurate.
+
+#### Add harvestId to Session Replay payloads
+Adds a unique harvest ID to Session Replay payloads to support better indexing and querying on the platform.
+
+#### JSErrors timestamped per harvest
+JSErrors that happen multiple times throughout a page's life will now receive a timestamp unique to the agent harvest cycle instead of consistently reporting the timestamp of the first occurrence of that error.
+
+
+### Bug fixes
+
+#### Clean up xhrWrappable
+Remove `xhrWrappable` which is an old variable checking for `addEventListener` on XHR. It is expected to have no compatibility impact on modern standard frameworks or browsers.
+
+#### Prevent null CLS
+Add a check to prevent null and undefined web-vitals values from being reported.
+
+## Support statement
+
+New Relic recommends upgrading the agent regularly to ensure you get the latest features and performance benefits. Older releases will no longer be supported when they reach [end-of-life](https://docs.newrelic.com/docs/browser/browser-monitoring/getting-started/browser-agent-eol-policy/). Release dates are reflective of the original publish date of the agent version.
+
+New browser agent releases are rolled out to customers in small stages over a period of time. Because of this, the date the release becomes accessible to your account may not match the original publish date. Please see this [status dashboard](https://newrelic.github.io/newrelic-browser-agent-release/) for more information.
+
+Consistent with our [browser support policy](https://docs.newrelic.com/docs/browser/new-relic-browser/getting-started/compatibility-requirements-browser-monitoring/#browser-types), v1.258.0 of the Browser agent was built for and tested against these browsers and version ranges: Chrome 115-123, Edge 114-123, Safari 16-17, and Firefox 116-124. For mobile devices, v1.251.1 was built and tested for Android Chrome 100-123 and iOS Safari 15.5-16.2.