Most product teams track "signed up → logged in" as activation.
It's useless. Logging in isn't retention — it's curiosity.
Here's what separated the onboarding flows that work from the ones that don't, from auditing dozens of B2B SaaS products this year:
The teams that retained users all did one thing:
They wrote down — in user-language, not product-language — the exact behavior that predicts retention for their product.
Not "used feature X." Not "invited a teammate." Something specific: "imported their first customer list," "connected their Stripe account," "sent their first automated email."
Then they built the onboarding flow backwards from that moment.
What's the one behavior you'd bet your retention on?