Error codes

The web app, the wat CLI, and the skills plugin all hit the same API, so they all surface the same errors. With --json, a CLI failure is always the envelope { "success": false, "error": { "code": "...", "message": "..." } } plus the HTTP status.

Naming convention: lower_snake codes come from the server (the API rejected the request). UPPER_CASE codes are synthesized by the CLI itself, before or instead of an API call.

Booking validation and conflicts (server)

Code	HTTP	Meaning	What to do next
`invalid_range`	422	The end time is not strictly after the start time, or a date failed to parse.	Fix the times: end must come after start, in a parseable format such as `2026-06-10T10:00`.
`below_min`	422	The booking is shorter than the 15-minute minimum.	Lengthen the booking to at least 15 minutes.
`in_past`	400	The booking starts in the past.	Pick a start time in the future.
`beyond_horizon`	400	The booking starts more than 30 days ahead.	Pick a date within the 30-day booking horizon.
`outside_hours`	400	The booking falls outside the opening hours (06:00 to 22:00 Europe/Brussels), or crosses midnight.	Move the booking inside opening hours, on a single Brussels day.
`title_too_long`	422	The title exceeds 200 characters.	Shorten the title (it is optional, you can drop it).
`invalid_guests`	422	A guest entry is not a valid email address (the message names it), or guests were passed on a maintenance block.	Fix or remove the flagged address and retry.
`too_many_guests`	422	More than 10 guests on one booking.	Trim the guest list to 10 or fewer.
`overlap`	409	The slot was taken between your availability check and the booking.	Re-check availability and pick another free slot.
`budget`	409	The booking would push you past the 2-hour daily budget on some Brussels day.	Shorten the booking, move it to another day, or cancel one of your other bookings that day.
`check`	422	The database’s own constraints rejected the times (the backstop behind `invalid_range`).	Treat like `invalid_range`: fix the start and end times.

Authentication and permissions

HTTP	CLI code	Meaning	What to do next
401	`unauthenticated`	No API key, or the key is invalid or revoked.	Run `wat login`, or pass a valid key via `--api-key` / `WAT_CLI_API_KEY`.
403	`permission-denied`	The key is valid but the action is not allowed: editing or cancelling someone else’s booking, an admin-only action (maintenance blocks, `rooms list --all`), or no active member behind the key.	Stop and tell the user; only the booking’s owner or an admin can do this.
401	`INVALID_OTP`	The 6-digit login code is wrong or expired (`wat login`).	Request a fresh code with `--request-code` and retry.
403	`NOT_AUTHORIZED`	Login completed the email code, but the email may not enroll: it is not on WAT’s resident list (or the account is deactivated).	A resident-list miss automatically files an access request with the WAT admins. Tell the user to watch for the approval email, then log in again. Retrying does not speed up the review.

When the server returns an error without a code of its own, the CLI derives one from the HTTP status: unauthenticated (401), permission-denied (403), not-found (404), conflict (409), validation (422), internal (5xx), and network-error when no response arrived at all.

CLI-side codes

These never reach the server: the CLI fails fast locally and exits non-zero.

Code	Meaning	What to do next
`ROOM_NOT_FOUND`	No active room matches the `--room` name or id.	Run `wat rooms list` and use an exact name or the room id.
`AMBIGUOUS_ROOM`	More than one room shares that name.	Pass the room id instead of the name.
`INVALID_TIME`	A `--start`, `--end`, `--from`, or `--to` value failed to parse.	Use an ISO-style value such as `2026-06-10T10:00`, optionally with `--tz` or an explicit offset.
`MISSING_FLAG`	`wat login --json` needs a flag it did not get (it never prompts in JSON mode).	Pass the missing flag: `--email`, or `--code` after a `--request-code` send.

Guides

Reference

Booking validation and conflicts (server)

Authentication and permissions

CLI-side codes

​Booking validation and conflicts (server)

​Authentication and permissions

​CLI-side codes

Booking validation and conflicts (server)

Authentication and permissions

CLI-side codes