bug: better-auth session remains null despite valid cookies in React Native/Expo

[Lyons800]

Provide environment information

System: OS: macOS 15.5 CPU: (14) arm64 Apple M4 Pro Memory: 116.08 MB / 24.00 GB Shell: 5.9 - /bin/zsh Binaries: Node: 22.14.0 - ~/.nvm/versions/node/v22.14.0/bin/node npm: 10.9.2 - ~/.nvm/versions/node/v22.14.0/bin/npm pnpm: 9.6.0 - ~/.nvm/versions/node/v22.14.0/bin/pnpm

Describe the bug

When using better-auth with Discord OAuth in the React Native/Expo app, cookies are being set and returned correctly, but the session object remains null. The authentication flow appears to work (user gets redirected back, cookies are present), but useSession(), getSession(), and listSessions() all return null/empty results.

Link to reproduction

https://github.com/t3-oss/create-t3-turbo

To reproduce

1. Fresh install of create-t3-turbo template
2. Configure better-auth with Discord OAuth provider
3. Run Expo development server
4. Attempt to sign in with Discord
5. Observe that cookies are set but session is null

Additional information

Expected behavior
After successful Discord OAuth flow, the session should be populated with user data.

Actual behavior
`LOG session null
LOG getSession result {"_h": 0, "_i": 0, "_j": null, "_k": null}
LOG listSessions result {"_h": 0, "_i": 0, "_j": null, "_k": null}
LOG cookies ; __Secure-better-auth.session_token=PVuP6dAgjwv......

[tonychandesign]

I can reproduce the same bug. Auth login is working from web urls, localhost, and deployed vercel url, but not via ios expo simulator

[MendyLanda]

same here

[AlexErrant]

As a counterpoint, Discord auth works just fine for me on Android+WSL+Windows. However, I am using ngrok, which might be bypassing some HTTPS issues.

[MendyLanda]

It's an issue still. (As of v1.3.5)

For me I found that I happens only when using the expo plugin in conjunction with oauth proxy plugin.

A reproduction repo can be found here
https://github.com/t3-oss/create-t3-turbo

Requirements:
Expo go / development build
Android device / emulator
Deployed oauth proxy app

[Robert2598]

There is a plug in that fixes this issue.

The plug in must be added in the plugins array inside the better auth init config.

https://www.better-auth.com/docs/integrations/next#server-action-cookies

[MendyLanda]

There is a plug in that fixes this issue.

The plug in must be added in the plugins array inside the better auth init config.

better-auth.com/docs/integrations/next#server-action-cookies

I tested with the nextCookies plugin and the issue still exists.