> ## Documentation Index > Fetch the complete documentation index at: https://core.vanish.trade/llms.txt > Use this file to discover all available pages before exploring further. # Open Position > Opens a lending position: advances funds from Vanish's trading accounts into the position's one-time wallet and runs your own instructions against them in the same transaction. Vanish wraps the unsigned transaction supplied in `main_tx`, signs it, and simulates it, then either returns the signed transaction for you to broadcast or - if the wrapped transaction exceeds Solana's size limit - submits a two-transaction Jito bundle itself. Follow every open with [`POST /borrow/commit`](/api-reference/lending/commit). Requires a signature valid for 10 minutes; see [Signing Requests](/guide/integration/signing#signing-requests) and the [Lending Flow](/guide/integration/lending#open-a-position). ## OpenAPI ````yaml POST /borrow/initiate openapi: 3.0.1 info: title: Vanish Core API description: API endpoints for the Vanish Core service. license: name: MIT version: 2.0.0 servers: - url: https://core-api-dev.vanish.trade security: - ApiKeyAuth: [] paths: /borrow/initiate: post: summary: Open Position description: >- Opens a lending position: advances funds from Vanish's trading accounts into the position's one-time wallet and runs your own instructions against them in the same transaction. Vanish wraps the unsigned transaction supplied in `main_tx`, signs it, and simulates it, then either returns the signed transaction for you to broadcast or - if the wrapped transaction exceeds Solana's size limit - submits a two-transaction Jito bundle itself. Follow every open with [`POST /borrow/commit`](/api-reference/lending/commit). Requires a signature valid for 10 minutes; see [Signing Requests](/guide/integration/signing#signing-requests) and the [Lending Flow](/guide/integration/lending#open-a-position). requestBody: description: Details of the request to open a position. content: application/json: schema: $ref: '#/components/schemas/BorrowInitiateRequest' required: true responses: '200': description: Successful lending action response. content: application/json: schema: $ref: '#/components/schemas/BorrowActionResponse' '400': description: >- Bad request. The amount is not greater than 0, the one-time wallet was not found or does not belong to this user, the balance available for the token is insufficient, the transaction failed simulation, or an action was already initiated with this signature. content: application/json: schema: $ref: '#/components/schemas/BorrowError' '401': description: >- Unauthorized. The request is missing a valid API key or the signature is invalid. content: application/json: schema: $ref: '#/components/schemas/BorrowError' '429': description: >- Rate limit exceeded. Contact the Vanish team to raise your team's requests-per-second cap. content: application/json: schema: $ref: '#/components/schemas/BorrowError' '500': description: Internal server error. content: application/json: schema: $ref: '#/components/schemas/BorrowError' components: schemas: BorrowInitiateRequest: required: - smart_wallet_id - user_address - source_token_address - amount - loan_additional_sol - jito_tip_amount - main_tx - timestamp - user_signature type: object properties: smart_wallet_id: description: >- Identifier of the one-time wallet the funds are advanced into, returned by the /borrow/smart-wallet endpoint. Must belong to user_address. type: integer example: 4821 user_address: description: The Solana wallet address of the user opening the position. type: string source_token_address: description: >- The address of the token being advanced into the one-time wallet. Wrapped SOL is normalised to native SOL after the signature check. type: string amount: description: >- The amount to advance into the one-time wallet, expressed in the smallest unit (e.g., lamports for SOL). Must be greater than 0. Can be provided as a string or a number oneOf: - type: string pattern: ^[0-9]+$ - type: integer format: int64 loan_additional_sol: description: >- Additional SOL (in lamports) advanced alongside the token, typically used for ATA creation and account initialization. The one-time wallet starts empty, so this is required the first time the position uses a given token: one ATA costs approximately 2039280 lamports. Pass 0 when the wallet already holds enough. Can be provided as a string or a number oneOf: - type: string pattern: ^[0-9]+$ - type: integer format: int64 jito_tip_amount: description: >- The amount of Jito tip, expressed in the smallest unit (e.g., lamports for SOL). Only applied when the wrapped transaction overflows Solana's size limit and a two-transaction bundle is used instead, but always required - it is part of the signed message either way. Can be provided as a string or a number oneOf: - type: string pattern: ^[0-9]+$ - type: integer format: int64 main_tx: description: >- Serialized or encoded transaction data carrying your own deposit or open instructions. The transaction must be provided unsigned, with the one-time wallet address set as the signer. type: string timestamp: description: >- Unix timestamp of when the position was opened (in milliseconds). Must be within 10 minutes of server time. Can be provided as a string or a number oneOf: - type: string pattern: ^[0-9]+$ - type: integer format: int64 user_signature: description: >- A digital signature of 'By signing, I hereby agree to Vanish's Terms of Service and agree to be bound by them (docs.vanish.trade/legal/TOS) Details: borrow:{smart_wallet_id}:{source_token_address}:{amount}:{loan_additional_sol}:{timestamp}:{jito_tip_amount}', signed by the user's wallet. type: string BorrowActionResponse: required: - action_id - tx_id type: object properties: action_id: description: Identifier of this lending or settle action. type: integer example: 88213 tx_id: description: Transaction signature of the action. Poll it via /borrow/commit. type: string transaction: description: >- Base64-encoded signed transaction for you to broadcast. Null when Vanish submitted a Jito bundle instead; always populated for settle. type: string nullable: true jito_bundle_id: description: >- If the wrapped transaction was too large for a single transaction and Vanish submitted a two-transaction Jito bundle, its bundle ID; otherwise null. When set, there is nothing for you to broadcast. Always null for settle. type: string nullable: true BorrowError: required: - error type: object properties: error: description: >- The error code or short description. Endpoint errors use the HTTP status text (for example '400 Bad Request'); errors raised by the API key middleware and the rate limiter carry the description here instead. type: string message: description: >- The specific reason for the failure. Null on a signature verification failure, and absent entirely on API key and rate limit errors - check for the presence of this field rather than assuming every error body has the same shape. type: string nullable: true securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key ````