> ## 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. # Build pinned unsigned on-chain transactions for self-signing (step 1 of 2) > The on-chain counterpart to `POST /v2/orders/intent`, for the operations an order cannot do off-chain: one-time approvals, redemptions of resolved positions, CTF split/merge, and unwrapping wrapped collateral. Kairos builds the exact calldata, pins it under a single-use `payload_id` (300 s TTL), and hands you the EIP-155 signing digest for each transaction. **You** sign with your own EOA and **you** pay the gas; Kairos only broadcasts what you signed via `POST /v2/onchain/submit`. **Polygon / Polymarket only.** `chain_id` is pinned to `137`; there is no `provider` field. **No RPC at build time.** You supply `nonce` and `gas_price_wei`; the server does not fetch a nonce, quote gas, or preflight your balance. A stale nonce or an under-priced transaction surfaces at broadcast, not here. **Multi-leg.** `op=approvals` returns several transactions; sign each `signing_digest_hex` raw (no EIP-191 prefix) and submit the signatures in the same order. **Auth & scope.** Requires `trade:execute` for `polymarket` AND the `User.executionFastlaneEnabled` allowlist — the same gate as the order lane. `owner_address` must be a wallet registered to the authenticated caller. There is no service-token, admission, circuit-breaker or rate-limit gate on this route. ## OpenAPI ````yaml /openapi/execution.yaml post /v2/onchain/intent 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: /v2/onchain/intent: post: tags: - Orders summary: >- Build pinned unsigned on-chain transactions for self-signing (step 1 of 2) description: >- The on-chain counterpart to `POST /v2/orders/intent`, for the operations an order cannot do off-chain: one-time approvals, redemptions of resolved positions, CTF split/merge, and unwrapping wrapped collateral. Kairos builds the exact calldata, pins it under a single-use `payload_id` (300 s TTL), and hands you the EIP-155 signing digest for each transaction. **You** sign with your own EOA and **you** pay the gas; Kairos only broadcasts what you signed via `POST /v2/onchain/submit`. **Polygon / Polymarket only.** `chain_id` is pinned to `137`; there is no `provider` field. **No RPC at build time.** You supply `nonce` and `gas_price_wei`; the server does not fetch a nonce, quote gas, or preflight your balance. A stale nonce or an under-priced transaction surfaces at broadcast, not here. **Multi-leg.** `op=approvals` returns several transactions; sign each `signing_digest_hex` raw (no EIP-191 prefix) and submit the signatures in the same order. **Auth & scope.** Requires `trade:execute` for `polymarket` AND the `User.executionFastlaneEnabled` allowlist — the same gate as the order lane. `owner_address` must be a wallet registered to the authenticated caller. There is no service-token, admission, circuit-breaker or rate-limit gate on this route. operationId: createOnchainIntent requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/OrderOnchainIntentRequest' responses: '200': description: Pinned unsigned transactions plus the digests to sign. content: application/json: schema: $ref: '#/components/schemas/OrderOnchainIntentResponse' '400': description: >- Exact `error` strings: `invalid owner_address`; `owner_address is not a registered wallet for this user`; `invalid gas_price_wei (expected a wei decimal string)`; `gas_price_wei must be > 0`; `condition_id is required for op=redeem`; `condition_id is required for op=`; `amount (wei) is required for op=`; `invalid amount (expected a wei decimal string)`; `amount must be > 0`; `wcol_amount (wei) is required for op=unwrap_wcol`; `invalid wcol_amount (expected a wei decimal string)`; `wcol_amount must be > 0`; `unsupported op: `; or the calldata builder's own message. content: application/json: schema: $ref: '#/components/schemas/OrderSimpleErrorResponse' '401': $ref: '#/components/responses/ExecUnauthorized' '403': description: >- `API key missing trade:execute scope`; `API-key access to polymarket is disabled`; `external-signing execution is not enabled for this account`; `external-signing authorization check failed`. content: application/json: schema: $ref: '#/components/schemas/OrderSimpleErrorResponse' '500': description: >- `internal server error` — failed to serialize or store the intent, or a `payload_id` collision. content: application/json: schema: $ref: '#/components/schemas/OrderSimpleErrorResponse' '503': description: >- `API-key access to polymarket is unavailable` — the API-key access cache read failed. content: application/json: schema: $ref: '#/components/schemas/OrderSimpleErrorResponse' components: schemas: OrderOnchainIntentRequest: type: object description: >- Body for `POST /v2/onchain/intent`. You supply the nonce and gas price yourself — the server makes no RPC call while building the intent (no nonce fetch, no gas quote, no balance preflight). required: - op - owner_address - nonce - gas_price_wei properties: op: type: string description: >- Which on-chain operation to build. `approvals` builds the one-time collateral + CTF approvals; `redeem` claims a resolved position; `split`/`merge` convert between collateral and a complete outcome-token set; `unwrap_wcol` unwraps wrapped collateral. enum: - approvals - redeem - split - merge - unwrap_wcol example: redeem owner_address: type: string description: >- The EOA that will sign and broadcast. Must be a wallet registered to the authenticated caller. condition_id: type: string nullable: true description: CTF conditionId. Required for `redeem`, `split` and `merge`. neg_risk: type: boolean nullable: true description: >- Whether the market is a neg-risk market (selects the adapter contract). collateral_address: type: string nullable: true amount: type: string nullable: true description: >- Amount in wei, decimal string. Required for `split` and `merge`; must be > 0. nonce: type: integer format: int64 description: >- The signing EOA's next transaction nonce. Caller-supplied — the server never queries the chain for it. gas_price_wei: type: string description: Gas price in wei, decimal string. Must be > 0. Caller-supplied. gas_limit: type: integer format: int64 nullable: true wcol_amount: type: string nullable: true description: >- Amount in wei, decimal string. Required for `unwrap_wcol`; must be > 0. OrderOnchainIntentResponse: type: object description: Response for `POST /v2/onchain/intent`. required: - payload_id - transactions - expires_at_us properties: payload_id: type: string format: uuid description: Single-use handle. Pass back to `POST /v2/onchain/submit`. transactions: type: array description: >- The transactions to sign, in the order they must be broadcast (ascending nonce). items: $ref: '#/components/schemas/OrderUnsignedTx' expires_at_us: type: integer format: int64 description: >- Wall-clock expiry, UNIX microseconds. TTL is 300 s here (longer than the 60 s order-intent TTL, because signing several transactions on a hardware wallet takes longer). requires_followup: type: string nullable: true description: Reserved. Always absent on a newly-created intent. OrderSimpleErrorResponse: type: object description: >- Minimal error body (`{"error": "..."}`, optionally `{"code": "..."}`) used by the auth middleware (401/403/429 on any endpoint), the external-signing `/v2/orders/*` lane, and the Kalshi-offchain balance endpoint. Distinct from `OrderErrorResponse` — these endpoints do not emit the full structured `error_details` shape. required: - error properties: error: type: string description: Human-readable error message. example: Insufficient scope code: type: string nullable: true description: >- Present only on the Kalshi-offchain endpoints (omitted entirely, not null, when absent). Observed values: `PLATFORM_API_ACCESS_DENIED`, `PLATFORM_API_ACCESS_DISABLED`, `INSUFFICIENT_SCOPE`, `NOT_CONFIGURED`, `NO_CREDENTIALS`, `INVALID_USER_ID`, `MISSING_API_KEY_ID`, `INVALID_PRIVATE_KEY`, `INVALID_CREDENTIALS`, `CONFIG_ERROR`, `ENCRYPTION_ERROR`, `DB_ERROR`, `INTERNAL_ERROR`, `KALSHI_API_ERROR`. OrderUnsignedTx: type: object description: >- One pinned unsigned transaction to sign and hand back to `POST /v2/onchain/submit`. required: - description - to - data_hex - value - nonce - gas - gas_price - chain_id - signing_digest_hex - unsigned_rlp_hex properties: description: type: string description: Human-readable label for this leg (e.g. which approval it grants). to: type: string data_hex: type: string value: type: string nonce: type: integer format: int64 gas: type: string gas_price: type: string chain_id: type: integer description: Always `137` — this lane is Polygon/Polymarket-only. example: 137 signing_digest_hex: type: string description: >- The legacy EIP-155 sighash (`keccak256` of the unsigned RLP). Sign these raw 32 bytes — no EIP-191 prefix. The server normalizes `v` to `35 + 2·chain_id + parity` itself. unsigned_rlp_hex: type: string 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.