> ## Documentation Index > Fetch the complete documentation index at: https://docs.0xmonaco.com/llms.txt > Use this file to discover all available pages before exploring further. # Replace existing order > Replace existing order. Replaces an existing order with new parameters by canceling the original order and creating a new one with the updated price/quantity. Priority is lost in the order book. ## OpenAPI ````yaml /proto-openapi/api/openapi.yaml put /api/v1/orders/{orderId} openapi: 3.0.3 info: title: Monaco Protocol API description: REST API for the Monaco Protocol hybrid CLOB exchange. version: 1.0.0 servers: - url: https://staging.apimonaco.xyz description: Staging server (Testnet) security: [] tags: - name: AccountsService - name: ApplicationsService - name: AuthService - name: BuildercodeRewardsService - name: CopyTradingService - name: DelegatedAgentsService - name: FaucetService - name: FeesService - name: HealthService - name: ManagedMarketsService description: |- Wallet-authenticated maker assignments. The signed session must match both configured maker user and application. Owner IDs are process fences, never auth. Only wallet sessions are supported; delegated-agent sessions receive 403. - name: MarginAccountsService description: |- Current public isolated-margin semantics: - a user has one parent margin account per application scope - opening orders create or reuse isolated position buckets under that parent - parent account creation is handled internally by margin workflows - name: MarketService - name: OrderbookService - name: OrdersService - name: PositionsService description: |- Current public isolated-margin semantics: - positions link to a parent margin account and, when applicable, a bucket id - opening orders create or reuse isolated position buckets under the parent - users can open another isolated position by reusing the parent account with a different market bucket - name: PulseService - name: SweeperService - name: TraderCodeService - name: TradesService - name: WhitelistService - name: WithdrawalsService paths: /api/v1/orders/{orderId}: put: tags: - OrdersService - Orders summary: Replace existing order description: |- Replace existing order. Replaces an existing order with new parameters by canceling the original order and creating a new one with the updated price/quantity. Priority is lost in the order book. operationId: replace_order parameters: - name: orderId in: path required: true schema: type: string default: 2b1a5f9c-0000-4000-8000-000000000003 example: 2b1a5f9c-0000-4000-8000-000000000003 requestBody: content: application/json: schema: $ref: '#/components/schemas/ReplaceOrderRequest' required: true responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/ReplaceOrderResponse' '400': description: Invalid order ID, order cannot be replaced, or insufficient balance '401': description: Authentication required or order doesn't belong to user '404': description: Order not found '429': description: >- Order rate limit exceeded — the per-account item-weighted budget, or the budget the account family (master and sub-accounts) shares, is spent; retry after the interval in details.retryAfter '500': description: Internal server error security: - monacoSignature: [] - monacoHttpSignature: [] components: schemas: ReplaceOrderRequest: type: object properties: selfTradePreventionMode: example: CANCEL_TAKER enum: - CANCEL_MAKER - CANCEL_TAKER - CANCEL_BOTH - SKIP type: string description: >- Per-order self-trade-prevention override for the replacement: CANCEL_MAKER, CANCEL_TAKER, CANCEL_BOTH, or SKIP (see the create-order field for the full semantics). A replacement is a new order with a new id, so it carries its own value and inherits nothing from the original — restate it to keep the override. Omitted, your wallet's configured default applies, else the platform default CANCEL_MAKER. The requested value is echoed back as selfTradePreventionMode on order reads, absent when omitted here. nullable: true price: example: '35500.00' type: string description: New limit price (if changing) nullable: true quantity: example: '0.7' type: string description: >- New TOTAL quantity (if changing). On a partially filled order the replacement rests total minus filled, and collateral is locked for that remainder only (FIX cancel/replace convention: LeavesQty = OrderQty - CumQty). Must exceed the filled amount. Omitted, the replacement keeps the unfilled remainder. Margin reduce-only orders follow the same rule: the quantity is the order's total, and what the replacement rests (total minus filled) must not exceed the live position it reduces. nullable: true useMasterBalance: example: false type: boolean description: Use master account balance for sub-account orders nullable: true postOnly: example: false type: boolean description: >- Post-only: reject instead of matching if this limit order would cross the book — rejected with HTTP 400 / gRPC INVALID_ARGUMENT carrying the structured error code POST_ONLY_WOULD_CROSS (REST error-envelope 'code' field; gRPC google.rpc.ErrorInfo reason; batch per-item error.code). Matching the 'post-only order would cross' message substring is a legacy fallback. LIMIT orders with GTC only; rejected on MARKET orders and IOC/FOK. nullable: true clientOrderId: example: quote-btc-1130-a type: string description: >- Client-assigned correlation handle, echoed back on order reads (detail and list) and on order WebSocket events. At most 64 characters from [A-Za-z0-9._:-]; surrounding whitespace is trimmed before storage, and a blank or whitespace-only value is treated as absent. Uniqueness is enforced only among your orders that are RESTING on the book: a create or replace reusing a value another of your resting orders still holds is rejected with HTTP 409 / gRPC ALREADY_EXISTS and the code CLIENT_ORDER_ID_CONFLICT. An order that never rests — MARKET, IOC/FOK, or a LIMIT that fills completely on arrival — does not take the handle, and the value is released the moment any order reaches a terminal state. It is therefore NOT an idempotency key, though on this replace path a retry cannot double-execute: the request names the original order id, and the sequencer revalidates that original in memory and on the book at sequence time, so once the first replacement succeeds the original is gone and a retry is rejected with ORDER_NOT_FOUND rather than placing a second order. That code is itself ambiguous — the original may instead have filled or been cancelled — so the risk here is acting on a stale view, not duplicate execution. Reconcile a lost response against the order WebSocket stream, which carries this value on the submit acknowledgement and on fills, including for orders that never rest; order history is replica-backed and can omit an order that did land. The stream is not replayable and has no sequence number to backfill from, and its fan-out is non-persistent Core NATS: the service can re-establish an ended upstream subscription without closing your socket, so events can be missed while your connection still looks healthy. A matching event is therefore positive proof the order was accepted, but silence is NEVER evidence it was not, and no client-observable condition makes it so. Absent positive evidence the outcome is unresolved: hold and escalate rather than resubmitting. A replacement carries no order type or time-in-force and its original must still be RESTING, so the post-acceptance rejection shapes are unreachable here: the reachable failures are all pre-acceptance — malformed, post-only would cross, handle conflict, or the original no longer resting (ORDER_NOT_FOUND) — and each fails the request, emits no event and is never written to order history (an order rejected AFTER acceptance is persisted with status REJECTED, so only the pre-acceptance class is absent). Where no surface is conclusive, do not resubmit. A replacement is a new order with a new id, so it carries its own value and inherits nothing from the original — restate it to keep the handle. nullable: true additionalProperties: false ReplaceOrderResponse: type: object properties: orderId: example: 987e6543-e21b-12d3-a456-426614174000 type: string description: New replacement order UUID format: uuid nullable: true status: example: SUCCESS type: string description: 'Result status: SUCCESS or FAILED' nullable: true message: example: Order replaced successfully type: string description: Human-readable status message nullable: true originalOrderId: example: 123e4567-e89b-12d3-a456-426614174000 type: string description: UUID of the original cancelled order format: uuid nullable: true updatedFields: $ref: '#/components/schemas/UpdatedFields' matchResult: $ref: '#/components/schemas/MatchResult' UpdatedFields: type: object properties: price: example: '35500.00' type: string description: >- The replacement's limit price: the requested price, or the original order's price when price was omitted. nullable: true quantity: example: '0.7' type: string description: >- The replacement's total quantity: the requested quantity, or the original order's total when quantity was omitted. It is not the resting size: the replacement rests this total minus the already-filled amount, so a 100-lot with 60 filled reports 100 here and rests 40. Read the order's remainingQuantity for the resting size. Margin reduce-only replacements report their total the same way. nullable: true MatchResult: type: object properties: tradesCount: example: 2 type: integer description: Number of trades generated by this order format: int32 nullable: true totalFilled: example: '0.2' type: string description: Total quantity filled nullable: true remainingQuantity: example: '0.3' type: string description: Remaining unfilled quantity nullable: true averageFillPrice: example: '35100.00' type: string description: Volume-weighted average fill price nullable: true status: example: PARTIALLY_FILLED type: string description: Resulting order status after matching nullable: true actualSlippageBps: example: 15 type: integer description: Actual slippage incurred in basis points format: int32 nullable: true maxSlippageBps: example: 50 type: integer description: Maximum slippage tolerance that was set format: int32 nullable: true executionPriceRange: $ref: '#/components/schemas/ExecutionPriceRange' ExecutionPriceRange: type: object properties: bestPrice: example: '2045.00' type: string description: Best execution price achieved nullable: true worstPrice: example: '2052.00' type: string description: Worst execution price in the fill nullable: true securitySchemes: monacoSignature: type: apiKey description: >- Ed25519 session-key request signing. Every authenticated request carries three headers: `X-Monaco-PublicKey` (64-char lowercase-hex session public key), `X-Monaco-Timestamp` (Unix milliseconds, within 30s of server time), and `X-Monaco-Signature` (hex ed25519 signature). The signature is over `METHOD\npath?query\ntimestamp_ms\nSHA256_hex(body)`, where the body hash is the SHA-256 of the empty byte string when there is no body. Obtain the session keypair from `POST /api/v1/auth/challenge` followed by `POST /api/v1/auth/verify`. name: X-Monaco-Signature in: header monacoHttpSignature: type: apiKey description: >- RFC 9421 Ed25519 session-key request signatures. Send Signature-Input, Signature, and Content-Digest together; never combine them with X-Monaco-* credentials. The monaco signature covers @method, @path, @query, and content-digest in that order, with created (Unix seconds within 30s of server time), keyid (registered lowercase-hex session public key), and alg=ed25519 parameters. Content-Digest uses RFC 9530 sha-256 over the exact body bytes, including the empty body. Query coverage retains ordering and percent encoding. Timestamp freshness does not reject repeated identical requests; use endpoint idempotency where supported. Existing legacy signing remains supported during server-first migration; SDK RFC 9421 signing is opt-in. See https://docs.0xmonaco.com/reference/http-message-signatures for the complete profile and trust model. name: Signature in: header ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.