> For the complete documentation index, see [llms.txt](https://docs.zenfinder.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zenfinder.ai/reference/the-service-window-6.7.md).

# The service window (§6.7)

Free-form messages (`text`, `image`, `document`, `location`, `interactive`) can only be sent inside a 24-hour window that opens when a user messages the business first (or reaches it via a ZenFinder ad or click-to-chat link, which opens a 72-hour *free* window covering every message category). Outside that window, sending free-form fails with `400 (#131047)` — send an approved `template` message instead, which is allowed at any time.


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