Flutter Birmingham - 15 September, 2026

## George Ikwegbu

### One Login, Many Apps: A Flutter Deep-Dive into Ecosystem Authentication

You open the Amazon Shopping app, signed in as usual. Then you download Alexa for the first time, and before you type a single character, it asks: "Continue as George?" No shared login screen. No password. Two independently-shipped apps, and one already trusts the other. This talk pulls that pattern apart and rebuilds it in Flutter, using the real native mechanisms behind ecosystem-level SSO rather than a shortcut. We'll cover how iOS Shared Keychain Access Groups and App Group containers let signed-together apps share session state, how Android's AccountManager and signature-level ContentProviders achieve the same thing without the now-deprecated shared UID trick, and why backend OAuth 2.0 token verification still has the final word regardless of what's shared on-device. Then I'll demo it live with two working Flutter apps, Shopfront and Companion, sharing one NestJS backend. Shopfront broadcasts a lightweight, non-sensitive session signal (never real tokens) via native platform channels. Companion checks for it on every launch and offers a "Continue as George?" prompt the user can accept, or firmly decline in favour of logging in manually, because ambient trust should never be forced trust. You'll leave with a working mental model of Keychain groups vs. App Groups, when signature-level Android permissions beat a deep link, and the production gotchas (signing mismatches, same-device testing, token-scope discipline) that trip people up the first time they try this for real. Architecture: Flutter · Provider · GetIt · Clean Architecture · NestJS

### About George

George Ikwegbu is a Senior Flutter Engineer and Team Lead with 5+ years of experience shipping production mobile apps across fintech, mobility, and IoT. He most recently led mobile engineering at Reisty Inc, and holds an MSc in Computer Science (AI & IoT) from York St. John University. George is the founder of Spiralync Ltd, writes on Flutter architecture for LinkedIn and dev.to, and is active in the Bristol and London Flutter communities.