Errors

Error envelope, full code matrix, and per-code troubleshooting.

Error response shape

All non-2xx responses share this envelope:

{
  "error": {
    "code": "past_order_cutoff",
    "message": "The order window for this auction closed at 2026-04-19T00:00:00+09:00.",
    "request_id": "req_8829374",
    "details": {
      "cutoff_at": "2026-04-19T00:00:00+09:00",
      "now": "2026-04-19T02:30:00+09:00"
    }
  }
}

Branch on error.code only. error.message is human-readable English and may evolve. details is structured supplementary info — fields vary per code.

request_id is also returned as the X-Request-Id response header. Include it in any support request.

HTTP → code matrix

HTTP	error.code values
400	validation_error, missing_idempotency_key, missing_max_bid, invalid_cursor
401	missing_api_key, invalid_api_key
403	ip_not_allowed, invalid_status_transition (partner attempting LMN-owned transition)
404	vehicle_not_found, order_not_found
409	invalid_status_transition, past_order_cutoff, duplicate_order
410	vehicle_unavailable
422	idempotency_key_reused
429	rate_limited
500	internal_error

Per-code troubleshooting

Code	HTTP	Meaning	When	What to do
validation_error	400	Request shape failed validation.	Bad enum, missing field, model without make, ids > 100, from without to.	Inspect error.details.issues[].path. Fix the request; do not retry as-is.
missing_idempotency_key	400	Idempotency-Key header absent on POST.	Any POST or DELETE without header.	Add UUID v4 header, retry.
invalid_cursor	400	Cursor invalid, expired, or sort-mismatched.	Resending a cursor after changing sort=.	Restart pagination from page 1 with the desired sort.
missing_max_bid	400	Auction vehicle requires max_bid_amount_usd.	POST with null/omitted/below-listing bid.	Add max_bid_amount_usd (integer > 0, ≥ listing). Not required for buy-now.
missing_api_key	401	x-api-key header absent.	Any request without header.	Add the header.
invalid_api_key	401	Key not recognized, revoked, or wrong env.	Sandbox key against production URL, or revoked key.	Verify env (sandbox vs production); rotate if compromised.
ip_not_allowed	403	Source IP not in allowlist.	Egress IP missing from per-env allowlist.	Email [e-mail] to add IP. Check egress NAT stability.
invalid_status_transition	403 / 409	Requested transition not permitted.	403: partner attempting LMN-owned fulfillment_detail. 409: delivered from non-shipping, or DELETE from non-proceed.	Re-fetch GET /v1/orders/{id} to see current state. Only use partner-permitted transitions.
vehicle_not_found	404	Unknown vehicle ID.	Stale or wrong-env ID.	Refresh the listing; confirm correct base URL.
order_not_found	404	Unknown order ID for this key.	Wrong env, cross-key ID, or deleted.	Confirm correct base URL; the ID belongs to your account.
past_order_cutoff	409	POST after the auction’s cutoff.	auction_date - 1 day, midnight KST already passed.	Inform dealer that the order window is closed.
duplicate_order	409	Active order already exists for this vehicle.	Repeat POST while a prior order is not terminal. details.existing_order_id references it.	Redirect user to existing order page. Do not auto-retry.
idempotency_key_reused	422	Same Idempotency-Key with a different vehicle_id.	Client-library bug reusing keys across logical requests.	Inspect details.original_vehicle_id. Generate a fresh key per new order.
vehicle_unavailable	410	Vehicle no longer available.	Dealer or buy-now listing disappeared.	Move order to cancelled in UI; notify dealer.
rate_limited	429	Per-key rate limit exceeded.	Burst exceeded sliding-window bucket.	Respect Retry-After header; client-side exponential backoff.
internal_error	500	Server-side failure.	Rare; LMN on-call is paged automatically. Body carries only a generic message — no stack traces.	Retry with exponential backoff (3 tries). If persistent, share request_id with support.