> ## Documentation Index > Fetch the complete documentation index at: https://docs.kairos.trade/llms.txt > Use this file to discover all available pages before exploring further. # Cancel a single order > Cancels one order by internal id. Polymarket cancellation is an L2 API-key (HMAC) operation on the venue side, so no EOA/wallet signature is required — this works identically for custodial and external-signing orders. **This endpoint almost always returns `200`, even on failure to cancel.** `success: false` with a `message` covers: the order is already terminal (filled/cancelled/expired/failed), or the venue currently refuses the cancel (still live — retry). Non-2xx status codes are reserved for auth/ownership/not-found/infrastructure failures, not "the cancel didn't happen." **Cancel-before-submit race.** If the order hasn't reached the exchange yet (still `pending`/`queued`), it is cancelled locally via an atomic conditional update that races safely against the in-flight submission. If the submission wins that race (order mid-submission), the response is `success: false` asking the caller to retry shortly. **Fill-during-cancel.** A venue acknowledgement is followed by terminal fill verification. Until the response carries `terminal_fill_verification.state: complete`, it returns `success: false` and consumers must keep protection active. The completed receipt's `final_filled_quantity` is the authoritative venue cumulative (never the latest fill delta), including explicit zero, and is published only after the corresponding Trade/Position fold. Kalshi may complete this barrier synchronously; other venues normally complete through the polling worker and expose the retained receipt on retry or `GET /orders/{order_id}`. **Auth & scope.** Requires `trade:execute` and ownership of the order (`403` otherwise). ## OpenAPI ````yaml /openapi/execution.yaml post /orders/{order_id}/cancel openapi: 3.1.0 info: title: Kairos Order Execution API version: 1.0.0 summary: >- Order entry, cancellation, fee quotes, and live position exposure across venues. description: > The Order Execution API at `execution.kairos.trade` places and manages orders across every venue Kairos integrates. Two lanes: - **Custodial** (`POST /orders`) — Kairos signs and routes on your behalf (custodial signing). Async ack: a 200 means validated + enqueued; track via `GET /orders/{order_id}` or the WebSocket order/fill stream. - **Self-custody / external signing** (`POST /v2/orders/intent` + `POST /v2/orders/submit`) — for allow-listed institutional accounts on Polymarket and Predict.fun: Kairos builds the EIP-712 payload, you sign with your own key, submission is synchronous with the venue's verbatim result. `POST /v2/onchain/intent` + `POST /v2/onchain/submit` are the same pattern for on-chain operations (approvals, redeem, split/merge, unwrap) on Polygon, where you also pay the gas. ## Authentication All endpoints require a Kairos API key (`X-Client-Id` + `X-Api-Key` + `X-Api-Secret`) or a first-party session JWT, plus the per-operation scope (`trade:execute`, `trade:read`, `position:read`) where the operation documents one. Synthetic Books accepts any otherwise-valid account credential without an extra scope or allowlist. There is no anonymous tier. Scope checks apply to API-key credentials only; a session JWT carries no scope list and is treated as holding every scope. The custodial mutation endpoints (`POST /orders`, the three cancel endpoints) and Synthetic Books create/refresh/release carry an additional `RequireServiceToken` gate satisfied by **any** of: the full API-key triple, an internal `X-Service-Token`, or a valid `X-Csrf-Token`. API-key consumers need no extra header — but a bare `Authorization: Bearer ` alone is NOT sufficient on those routes. The `/v2/orders/*` and `/v2/onchain/*` external-signing routes have no such gate: a session JWT alone works there. ## Rate limits Order submission is capped per user (default 5 orders per **second**, sliding window, `ORDER_RATE_LIMIT_PER_SEC`); some credentials carry an `orders` override, which is enforced on its own per-credential window of the same duration *in addition to* the per-user window — either one denying is a `429`. Idempotent replays (same `client_order_id`) return the existing order before the limiter runs and never consume a slot. The limiter is Redis-backed and **fails closed**: if Redis is unreachable the submission is denied with `429`. Separately, repeated *authentication failures* from one client IP are throttled at 10 failures per 60 s (also fail-closed). That limiter returns the minimal `{"error": "Too many authentication attempts"}` body. **No rate-limit headers.** This service does not emit `Retry-After`, `X-RateLimit-*`, or any other backoff hint on a `429` — back off on your own schedule. ## Error responses **Six different error body shapes are in use across this service and they are not interchangeable.** Check the shape documented on the specific operation before writing a parser; a client that assumes one shape will read `undefined` for the reason on the others. 1. `OrderErrorResponse` — the structured envelope (`error`, `code`, `error_details{code,message,details?,metadata?,actions}`) returned by every handler that surfaces an `ExecutionError`/`ApiError`: order submission, cancel-all, the CTF endpoints, the Polymarket/Opinion onboarding endpoints, Hyperliquid withdraw/transfer, and most of the deposit-wallet family. Note the two `code` fields differ in case: top-level `code` is PascalCase (`"AuthInsufficientScope"`), while `error_details.code` is the SCREAMING_SNAKE_CASE wire code (`"AUTH_INSUFFICIENT_SCOPE"`). Match on `error_details.code`. 2. `OrderSimpleErrorResponse` — the minimal `{"error": "..."}` (sometimes with `code`) used by the auth middleware (any endpoint's `401`/`403`/`429`), the whole `/v2/*` external-signing and on-chain lane, the Kalshi and Predict.fun endpoints. 3. `OrderMarketLinkErrorResponse` — `{"message": "..."}`, with no `error` and no `code`. Used by `POST /orders/market-links` **only**. 4. **Empty or plain-text, not JSON at all.** Several deposit-wallet endpoints — most importantly the RPC signed-batch submission and `POST /exchanges/polymarket/imported/relay-info` — return most 4xx/5xx responses with a **completely empty body** and `content-type: text/plain`. A handful of cases carry a bare plain-text sentence (`batch is not an allowed withdrawal or collateral conversion`, `relayer rejected batch: …`). Do not attempt to JSON-parse these. 5. Handlers whose Rust signature returns a bare `StatusCode` likewise send **no body at all**; those responses are marked "empty body (status code only)". 6. `SyntheticBookErrorResponse` — `{"error": "stable_snake_case_code", "message": "...", "details"?: {...}}` on `/v1/synthetics*`. Match the top-level `error`; upstream definition validation may be nested under `details`. A further wrinkle inside shape 1: some provider-access checks discard the specific reason and return a generic `"Request failed with status 403"` / `AUTH_CREDENTIALS_INVALID` body, while others preserve `AUTH_INSUFFICIENT_SCOPE` and the real message. Do not rely on the message text of an access denial being stable. The central `ExecutionError` → HTTP mapping (`ApiError::from`) is: | `ExecutionError` | Status | `error_details.code` | |---|---|---| | `InsufficientBalance` | 400 | `FUNDS_INSUFFICIENT_USDC` | | `CollateralLocation` | 400 | `FUNDS_COLLATERAL_LOCATION` | | `InvalidOrder` | 400 | `VALIDATION_INVALID_ORDER` | | `PositionShortfall` | 400 | `FUNDS_INSUFFICIENT_BALANCE` | | `MarketClosed` | 400 | `EXCHANGE_POLYMARKET_MARKET_CLOSED` | | `OrderAlreadyCancelled` | 400 | `VALIDATION_INVALID_ORDER` | | `UnsupportedExchange` | 400 | `EXCHANGE_UNSUPPORTED` | | `SlippageExceeded` | 400 | `MARKET_FOK_NOT_FILLED` | | `FokNotFilled` | 400 | `MARKET_FOK_NOT_FILLED` | | `AuthenticationError` | 401 | `AUTH_CREDENTIALS_INVALID` | | `CredentialError` | 401 | `AUTH_CREDENTIALS_NOT_FOUND` | | `MarketNotFound` | 404 | `VALIDATION_MARKET_NOT_FOUND` | | `OrderNotFound` | 404 | `VALIDATION_INVALID_ORDER` | | `MarketNotSettledOnChain` | 409 | `VALIDATION_MARKET_NOT_SETTLED_ON_CHAIN` | | `OrderbookUnavailable` | 422 | `ORDERBOOK_UNAVAILABLE` | | `ExchangeError` (code `429`/`RATE_LIMITED`) | 429 | `EXCHANGE_POLYMARKET_RATE_LIMITED` | | `ExchangeError` (code `401`/`UNAUTHORIZED`) | 401 | `AUTH_POLYMARKET_API_KEY_INVALID` | | `SigningError` | 500 | `SIGNATURE_ERROR` | | `DatabaseError` | 500 | `DATABASE_ERROR` | | `InternalError` / `LedgerReconciliationRequired` / `SponsoredRequestWedged` / `PreTradeError` | 500 | `INTERNAL_ERROR` | | `NetworkError`, `ExchangeError` (any other code) | 502 | `NETWORK_ERROR` / venue-classified | | `LockError` | 503 | `INTERNAL_ERROR` | | `Timeout` | 504 | `NETWORK_TIMEOUT` | A venue `ExchangeError` is further classified from the venue's own message text before it is mapped, so an "allowance is not enough" rejection becomes `ALLOWANCE_CTF_NOT_SET`, a "not enough balance" rejection becomes `FUNDS_INSUFFICIENT_BALANCE`, "post-only mode" becomes `MARKET_NOT_READY`, a "no liquidity" rejection becomes `MARKET_INSUFFICIENT_LIQUIDITY`, and so on. Match on `error_details.code`, never on `error`. ## Server-level guards Every request is subject to a 120 s timeout (`OE_REQUEST_TIMEOUT_SECS`), a 2 MiB request-body cap (`OE_MAX_BODY_BYTES`, over-size bodies get `413`), and a 1024-request global concurrency ceiling (`OE_MAX_CONCURRENT_REQUESTS`). Every response carries `X-Content-Type-Options: nosniff`, `X-Frame-Options: DENY`, HSTS, and a `default-src 'none'` CSP. ## Conventions - Prices are decimal strings on the 0–1 scale; `*_bps` fields are the same value in basis points (× 10000). - Quantities/sizes are decimal strings. - Structured errors carry `error_details.code` (SCREAMING_SNAKE_CASE) plus actionable recovery `actions`. ## Changelog **2026-09-14 — collateral routing fields on `POST /orders`.** Four optional request fields and one optional response field. `collateral` (`skip` | `check` | `fund`) **defaults to** `skip`, which is exactly today's path: no affordability check, no hold, no funding, zero added latency — so no existing caller changes behaviour without opting in. `shard_funding` **defaults to** `true`, which is also exactly today's behaviour: the Kalshi shard move is same-venue, zero-fee and already runs for every account; send `false` to opt out. `collateral=fund` requires both `max_bridge_fee_usdc` and `max_funding_wait_ms` and is rejected `400` naming the missing cap; either cap without `fund` is likewise a `400`. The response gains `funding`, `null` whenever no funding work ran. FIX sessions carry the same fields on `NewOrderSingle(D)` as optional tags `5701`–`5704`; a session that sends none of them is unchanged. contact: name: Kairos url: https://app.kairos.trade/docs/api-reference termsOfService: https://kairos.trade/terms servers: - url: https://execution.kairos.trade description: Production (central primary, us-east-1) - url: https://eu-west-1-polymarket.executor.kairos.trade description: >- Production regional execution node — Ireland, colocated with Polymarket. Same API surface; assigned at onboarding. - url: https://ap-northeast-1-predictfun.executor.kairos.trade description: >- Production regional execution node — Tokyo, colocated with Predict.fun. Same API surface; assigned at onboarding. - url: https://staging-execution.kairos.trade description: Staging security: - apiKeyClientId: [] apiKeyKey: [] apiKeySecret: [] paths: /orders/{order_id}/cancel: post: tags: - Orders summary: Cancel a single order description: >- Cancels one order by internal id. Polymarket cancellation is an L2 API-key (HMAC) operation on the venue side, so no EOA/wallet signature is required — this works identically for custodial and external-signing orders. **This endpoint almost always returns `200`, even on failure to cancel.** `success: false` with a `message` covers: the order is already terminal (filled/cancelled/expired/failed), or the venue currently refuses the cancel (still live — retry). Non-2xx status codes are reserved for auth/ownership/not-found/infrastructure failures, not "the cancel didn't happen." **Cancel-before-submit race.** If the order hasn't reached the exchange yet (still `pending`/`queued`), it is cancelled locally via an atomic conditional update that races safely against the in-flight submission. If the submission wins that race (order mid-submission), the response is `success: false` asking the caller to retry shortly. **Fill-during-cancel.** A venue acknowledgement is followed by terminal fill verification. Until the response carries `terminal_fill_verification.state: complete`, it returns `success: false` and consumers must keep protection active. The completed receipt's `final_filled_quantity` is the authoritative venue cumulative (never the latest fill delta), including explicit zero, and is published only after the corresponding Trade/Position fold. Kalshi may complete this barrier synchronously; other venues normally complete through the polling worker and expose the retained receipt on retry or `GET /orders/{order_id}`. **Auth & scope.** Requires `trade:execute` and ownership of the order (`403` otherwise). operationId: cancelOrder parameters: - name: order_id in: path required: true description: Internal Kairos order id. schema: type: string format: uuid responses: '200': description: >- Cancel outcome. Check `success` — a `200` does not guarantee the order was actually cancelled (see description). content: application/json: schema: $ref: '#/components/schemas/OrderCancelResponse' '400': description: >- No executor is registered for the order's exchange. Empty body (status code only). '401': $ref: '#/components/responses/ExecUnauthorized' '403': description: >- Order belongs to another user, missing `trade:execute` scope, or API-key access to the order's provider is disabled. Note this endpoint is behind the service-token/CSRF/API-key mutation gate, whose own rejections are `403` with a minimal `error` body. Otherwise empty body (status code only). '404': description: >- No order with that id, or the order disappeared mid-cancel. Empty body (status code only). '500': description: >- Database read/write failed, credentials could not be loaded, or the cancel outcome could not be confirmed at all. Empty body (status code only). '503': description: >- API-key access to the order's provider could not be checked (fails closed). Empty body (status code only). components: schemas: OrderCancelResponse: type: object description: >- Response for `POST /orders/{order_id}/cancel`. Returned with HTTP 200 even when `success` is `false`. required: - success - order_id - venue_reconciled properties: success: type: boolean description: >- Whether cancellation and terminal fill verification are both complete. A venue DELETE acknowledgement alone still returns false while verification is pending. order_id: type: string format: uuid message: type: string description: >- Human-readable outcome detail, e.g. "Order cancelled on exchange" or "Order is being submitted to exchange. Please try again in a moment." filled_quantity: type: string nullable: true description: >- Total cumulative filled quantity, decimal string, when terminal verification is complete. Omitted while pending or unknown; do not infer omitted as zero. The durable receipt repeats this exact cumulative in `final_filled_quantity`. avg_fill_price: type: string nullable: true description: >- Average fill price (decimal, 0..1) of any portion that filled before the cancel landed. Omitted when nothing filled or unknown. venue_reconciled: type: boolean description: >- True only when a venue-final snapshot was observed and its exact cumulative fill has passed through Kairos' position fold. Currently authoritative for Kalshi. reconciled_position: allOf: - $ref: '#/components/schemas/ReconciledPositionExposure' nullable: true description: >- Exact post-fold position authority. A reconciled order may omit this object, either because nothing filled or because the durable position projection could not be proven within the cancel budget; the cancel itself is still confirmed. Omission is never proof that the portfolio is flat. terminal_fill_verification: allOf: - $ref: '#/components/schemas/TerminalFillVerification' nullable: true description: >- Pending or completed durable receipt for the exact venue-order generation. A pending response is not a confirmed cancellation even when the venue acknowledged DELETE. ReconciledPositionExposure: type: object required: - exchange_id - market_id - token_id - outcome - net_size - base_established - market_resolved properties: exchange_id: type: string description: Canonical venue identity. example: kalshi market_id: type: string token_id: type: string outcome: type: string nullable: true net_size: type: string description: >- Exact signed post-fold position size as a decimal string, including zero. base_established: type: boolean description: >- Explicit proof that the durable position base was established. A returned reconciliation authority always sets this to true; clients must fail closed when it is absent or false during rolling deployment. market_resolved: type: boolean nullable: true description: >- Tri-state resolution authority. Null means resolution was not proven and must not be interpreted as false. TerminalFillVerification: type: object required: - state - exchange_order_id - reason - target_status - started_at properties: state: type: string enum: - pending - complete exchange_order_id: type: string description: Exact venue-order generation covered by the barrier. reason: type: string enum: - explicit_cancel - venue_absent target_status: type: string enum: - cancelled - expired started_at: type: string format: date-time final_filled_quantity: type: string nullable: true description: >- Exact venue cumulative, including explicit `0`; required when state is complete. verified_at: type: string format: date-time nullable: true description: Receipt completion timestamp; required when state is complete. responses: ExecUnauthorized: description: > No valid credential presented — missing/invalid API-key headers or an invalid/expired session token. content: application/json: schema: type: object required: - error properties: error: type: string example: Unauthorized securitySchemes: apiKeyClientId: type: apiKey in: header name: X-Client-Id description: >- Credential client id (`kairos_ck_...`). Must be sent together with X-Api-Key and X-Api-Secret. apiKeyKey: type: apiKey in: header name: X-Api-Key description: 64-char hex API key. apiKeySecret: type: apiKey in: header name: X-Api-Secret description: 64-char hex API secret. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.