# Parallel source policy: exclude_domains is ignored when include_domains is set

From Parallel's official Source Policy docs, the interaction rules that break filtering:

- `include_domains` is an allow list. Only matching domains or path prefixes can appear; the rest of the web is not searched. Never use it as a soft preference.
- `exclude_domains` is applied ONLY when `include_domains` is empty. Send both and your block list is silently ignored.
- `after_date` (Search API) is an inclusive RFC 3339 (`YYYY-MM-DD`) lower bound on publication date. Publish metadata is imperfect, so treat it as approximate.
- Apex domain `example.com` automatically includes all subdomains (www, blog, api). A path prefix like `example.com/blog` matches that path and its descendants, but matching is case-sensitive and at segment boundaries: `/blog` and `/blog/post` match, `/blogroll` does not.
- Combined filter limit is 200 entries.

The practical rule: one domain-list type per request. Need a hard corpus boundary for compliance? Use include_domains. Need to block a few bad sites while searching the open web? Use exclude_domains alone. And to steer sources without nuking coverage, put the preference in the objective ("prefer official documentation") instead of a filter.