chore(main): release 10.0.0

[flagsmithdev]

🤖 I have created a release beep boop

10.0.0 (2025-12-10)

⚠ BREAKING CHANGES

• onError callback behavior change: onError is now properly called when cacheFlags is enabled and the API is unreachable with no existing cache (#365)

  • Previous behavior: init() would resolve successfully even when the API failed, silently swallowing the error
  • New behavior: init() now rejects and triggers onError, matching the behavior when cacheFlags: false
  • Migration: Ensure your code handles errors from init() or provide defaultFlags as a fallback

• SDK User-Agent header: The SDK now sends a Flagsmith-SDK-User-Agent header with requests (#344)

  • Self-hosted users: Requires Flagsmith v2.196.0 or higher
  • Alternative: If you cannot upgrade, add this environment variable to your Flagsmith server:

    FLAGSMITH_CORS_EXTRA_ALLOW_HEADERS: Flagsmith-SDK-User-Agent
    

Features

• re-add sdk version headers (#344) (47b610f)

Bug Fixes

• onError not called if cacheFlags is true and api is not reachable (#365) (1411b85)

Other

• deps: bump js-yaml from 3.14.1 to 3.14.2 (#361) (e15a0dc)

[flagsmithdev]

🤖 Created releases:

• v10.0.0

🌻

[matthewelwell]

The release notes in the PR description look perfect, can we update them here in changelog.md too?