Idempotency

Send an Idempotency-Key on a write so retrying it after a timeout can't create a duplicate.

A network can fail after the server has done the work but before you get the answer. Retrying then risks doing the work twice: two tasks, two scans, two runs started. An Idempotency-Key header makes the retry safe.

curl -X POST https://app.xplantpro.com/api/v1/tasks \
  -H "Authorization: Bearer $XPLANT_API_KEY" \
  -H "Idempotency-Key: bench-3-0f2a7c91" \
  -H "Content-Type: application/json" \
  -d '{"title": "Check jar 47"}'

A repeat with the same key returns the first response, with the same status and body, and the response header Idempotent-Replay: true. The write happens once.

Which endpoints honour it

The header is honoured on these endpoints, and only these:

POST /assets: Attach a media file
POST /comments: Add a comment
POST /contaminations: Record a contamination
POST /devices: Register a device
POST /equipment/{id}/events: Record an equipment event
POST /explants: Create an explant
POST /label-scans: Record a label scan
POST /media-recipes: Create a media recipe
POST /plants: Create a plant
POST /sop-runs: Start an SOP run
POST /sop-runs/{id}/steps/{stepId}/events: Record step evidence
POST /sop-runs/{id}/steps/{stepId}/measurements: Record a step measurement
POST /stages: Advance a stage
POST /tasks: Create a task
POST /tasks/demand: Record a demand signal
POST /transfers: Record a transfer

Everywhere else the header is ignored. For sensor readings, make retries safe with an external_id and recorded_at on every reading instead: readings are de-duplicated on the device, the external_id and the time.

The rules


Format	8–255 characters from `A–Z a–z 0–9 . _ : ~ -`. A malformed key answers `422 VALIDATION_ERROR` rather than being silently ignored.
Scope	Your key plus the endpoint. The same string on two endpoints is two different writes, and two keys never collide.
How long	24 hours. After that, the same key starts a fresh write.
Still running	If the first request hasn't finished, a repeat answers `409 IDEMPOTENCY_IN_FLIGHT` with `Retry-After: 1`. Wait and send it again; don't assume it failed.
Failed writes	Aren't replayed. If the first attempt failed, the next attempt runs for real, so a passing glitch isn't pinned to your key for a day.
No header	The write runs unprotected. Idempotency is opt-in.

Choosing keys

Make one key per intent, not per attempt. Every retry of the same logical write sends the same value; a new write sends a new one.

Good keys come from your own data: station-3-run-wk38-start, scanner-3-<scan uuid>, nightly-sync-2026-09-25-task-8812. A random UUID generated once, stored with the pending write and reused on each retry, also works.

The JavaScript SDK takes { idempotencyKey } as the last argument of any write, and with retry: true it generates a key for you and reuses it across its own retries.

Which endpoints honour itCopy Anchor Link

The rulesCopy Anchor Link

Choosing keysCopy Anchor Link

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Which endpoints honour it

The rules

Choosing keys