Phantom Connect: browser verification matrix (Safari / iOS / Brave) — gates the flag

[Potolski]

Part of #983. Gates enabling the feature flag.

Verify the embedded wallet works on the browsers our learners actually use before turning it on for anyone.

Why this is a real risk

Embedded wallet SDKs that lean on third-party iframe storage break under Safari's Intelligent Tracking Prevention and Brave's shields.

Two signals suggest Phantom Connect avoids that: its dependency tree includes @phantom/indexed-db-stamper (IndexedDB, not third-party cookies) and @phantom/auth2, and Portal setup requires configured redirect URLs — i.e. a redirect-based OAuth flow rather than a cross-site iframe. That is an inference from packaging, not a tested result.

Note also that Safari ITP evicts script-writable storage after ~7 days without interaction, and Phantom's session is 7 days regardless — so the worst realistic case is a re-login, not a lost wallet. Confirm that.

Matrix

• Chrome desktop
• Safari desktop
• iOS Safari — highest risk and a large share of our Brazilian learners
• Android Chrome
• Brave with shields up
• Firefox

Per browser, record

• Connect completes and returns an address
• Session survives a page reload
• Session survives a browser restart
• Behaviour after the 7-day session expiry

Acceptance

Flag stays off until Chrome, iOS Safari and Brave all pass. If iOS Safari fails, that is a launch blocker — document the failure mode before deciding whether to ship for a subset of browsers.