## TL;DR

When building on Fivetran-synced tables, always filter WHERE _fivetran_deleted = FALSE (or _fivetran_active = TRUE in history mode) in every downstream query, or deleted rows will pollute aggregates. For GDPR-style hard deletes, add a post-load transformation step.

## Steps

1. When building on Fivetran-synced tables, always filter WHERE _fivetran_deleted = FALSE (or _fivetran_active = TRUE in history mode) in every downstream query, or deleted rows will pollute aggregates. For GDPR-style hard deletes, add a post-load transformation step. Agents that count rows or join Fivetran tables without the deleted filter will produce silently wrong numbers.

## When to use

Use this skill when you run into "Fivetran never hard-deletes: filter _fivetran_deleted in every query".

## When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

## Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

## Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.