feat(flags): Enjoy the benefits of /decide?v=4. $feature_flag_called events contain more details such as flag version

[haacked]

This is a follow-up to #1837 where we added support for /decide?v=4 in a backwards compatible fashion, but still made requests to /decide?v=3

With this change, we should get more useful debug information in $feature_flag_called events.

Changes

Changes the library to request /decide?v=4 instead of /decide?v=3. All the substantial changes were made in #1837.

Checklist

• Tests for new code (see advice on the tests we use)
• Accounted for the impact of any changes across different browsers
• Accounted for backwards compatibility of any changes (no breaking changes in posthog-js!)

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Name	Status	Preview	Updated (UTC)
posthog-js	✅ Ready (Inspect)	Visit Preview	Mar 20, 2025 4:01pm

[greptile-apps]

PR Summary

This PR updates the PostHog JS library to use /decide?v=4 endpoint instead of /decide?v=3, enabling enhanced debugging capabilities for feature flag events.

• Updates test assertions in src/__tests__/posthog-core.loaded.test.ts to expect /decide/?v=4 endpoint calls
• Modifies network recording tests in playwright/session-recording/session-recording-network-recorder.spec.ts to validate v4 endpoint patterns
• Adds support for additional metadata in feature flag events including flag versions, IDs, and evaluation reasons
• Maintains backwards compatibility while providing more detailed debugging information in $feature_flag_called events
• Follows up on PR feat(flags): Support /decide?v=4 and include version info flag called events #1837 which added initial v4 support but kept using v3 endpoint

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[github-actions]

Size Change: +22.5 kB (+0.62%)

Total Size: 3.63 MB

Filename	Size	Change
dist/array.full.es5.js	301 kB	+22.6 kB (+8.1%)	🔍
dist/customizations.full.js	14 kB	-88 B (-0.63%)

ℹ️ View Unchanged

Filename	Size
dist/all-external-dependencies.js	220 kB
dist/array.full.js	381 kB
dist/array.full.no-external.js	380 kB
dist/array.js	188 kB
dist/array.no-external.js	187 kB
dist/dead-clicks-autocapture.js	14.5 kB
dist/exception-autocapture.js	9.94 kB
dist/external-scripts-loader.js	2.75 kB
dist/main.js	189 kB
dist/module.full.js	381 kB
dist/module.full.no-external.js	380 kB
dist/module.js	189 kB
dist/module.no-external.js	187 kB
dist/posthog-recorder.js	211 kB
dist/recorder-v2.js	115 kB
dist/recorder.js	115 kB
dist/surveys-preview.js	71.3 kB
dist/surveys.js	76.6 kB
dist/tracing-headers.js	1.76 kB
dist/web-vitals.js	10.4 kB

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[dmarticus]

changes look good; CI looks annoyed. LMK if you want to untangle CI together!

[haacked]

changes look good; CI looks annoyed. LMK if you want to untangle CI together!

I think this might be a case of: