> ## Documentation Index > Fetch the complete documentation index at: https://docs.arena-predictions.com/llms.txt > Use this file to discover all available pages before exploring further. # Cancel a paper order > Cancels a resting paper order and returns its hold. Kalshi's path and answer (the order and reducedBy). Send X-Arena-Org to cancel on that organization's paper sandbox; without the header the cancel is on the personal account. An unknown or forbidden organization cancels nothing. An order that already filled or closed answers unchanged with reducedBy 0, so a cancel is safe to send twice. No ticker, title or price in the answer while the venue-data switch is off. ## OpenAPI ````yaml /openapi.json delete /portfolio/orders/{orderId} openapi: 3.1.0 info: title: Arena API version: 1.10.0 summary: >- Arena Predictions paper trading with an API key: read, and place paper orders with trade:write. Arena-owned data only. description: >- Arena Predictions (arena-predictions.com) is a sandbox for paper trading prediction markets at live prices. Every endpoint here serves Arena's sandbox, where every trade is a paper trade (mode "paper"); routing to live trading is coming. Keys are read-only and reach Arena-owned data only: the key's own identity and account, the leaderboards and published trader records with their resets and settled picks. Keys are managed with the signed-in browser session, never with a key. No exchange ticker, market title, entry price or venue price appears in any keyed response; the owner's own portfolio carries the owner's own paper numbers (a resting order's limitCents, a position's costDollars and contracts). Balances carry over: every account starts with 100,000 paper dollars, and a reset (at most one every 30 days, shown on a public profile) starts a new run. 1.2.0: seasons removed (no season field anywhere), leaderboard windows and kinds, trader resets, GET /account. 1.3.0: accounts are private by default. A private trader answers private: true with every P&L and rank null (resets and busts 0) and an empty pick list; a public trader whose earlier trades are still hidden has numbersShown: false and no P&L or rank. The key owner reads their own picks (each with placedPrivate and shown) and their own eval rows (GET /me/eval) with portfolio:read. No key can make an account public. 1.4.0: keys are managed by a person's session, on the website or as a signed-in CLI's session token (arena keys), never by a key; keys rotate with a grace period; every keyed answer carries the plan and its counts (RateLimit-*, Arena-Quota-*, Arena-Plan) and GET /usage says where the account stands; a new scope, markets:read, reads instruments, games and quotes; GET /portfolio and /portfolio/trades read the owner's positions, orders and trades. Venue references and venue prices are served only while the venue-data switch is on (it ships off): until then the quotes routes answer 403 venue_data_off and nothing keyed names a ticker or a venue's price. 1.5.0: GET /eval, the public eval board (records:read), each row with 95% intervals clustered by game. 1.6.0: GET /traders/{traderId}/track-record, a trader's Ed25519-signed 90-day record exactly as Arena signed it (records:read; it names Kalshi series inside its signed bytes, so it is served only while the venue-data switch is on), and tiedWithAbove on each eval row (null while this row's or the row above's interval is unknown). 1.7.0: a key created with trade:write (only when asked for by name: the Settings checkbox, arena keys create --trade, or scopes in the body) places paper orders with POST /portfolio/orders and cancels them with DELETE /portfolio/orders/{orderId}, at Kalshi's paths. Market and limit orders, buys by instrument or ticker and sells of a whole position, each with an idempotencyKey: the same key again answers the stored order with replayed: true and places nothing. Hard trade limits are always enforced: per key 10 new orders a minute and 50 a day, and 20 sells and cancels a minute; per account, across every key and connected app, 20 new orders a minute, 100 a day, and 40 sells and cancels a minute. 1.8.0: GET /traders/{traderId}/track-record asks promote-record for audience=keyed and is served while the venue-data switch is off (records:read). That envelope has the same scores, signed with the same key, and names no Kalshi series ticker and no venue. Quotes still answer 403 venue_data_off until the switch is on. The CLI, the Python SDK and hosted MCP verify still read the public envelope, which names series. 1.9.0: POST /backtest (markets:read) forwards a paper replay of settled Kalshi game-winner markets to the backtest edge function. The JSON body is forwarded and the function's JSON is returned, with mode paper. GET and every other method answer 405 method_not_allowed and are not forwarded. 1.10.0: X-Arena-Org, an organization id, on GET /portfolio, GET /portfolio/trades, POST /portfolio/orders and DELETE /portfolio/orders/{orderId}. When the header is present those calls use that organization's paper sandbox. When it is absent they use the key owner's personal paper account. A value that is not an organization id is 400 invalid_request. An unknown organization is 404 organization_not_found and one this key cannot use is 403 organization_forbidden. The personal account is never the fallback, and the header does not select a Combine evaluation account. Paper only. The keyless website routes (/api/quotes/{instrumentId}, /api/quotes/batch, /api/gaps, /api/gaps/{instrumentId}) are described in their own document, /openapi-public.json. termsOfService: https://arena-predictions.com/terms contact: name: Arena email: support@zbgcllc.com url: https://arena-predictions.com/support servers: - url: https://arena-predictions.com/api/v1 description: >- The Arena API. Every account on it trades in the sandbox (paper trading); routing to live trading is coming. security: [] tags: - name: Status description: Is the API up. - name: Identity description: Whose account a key acts for, and what it may do. - name: API keys description: >- Create, list, rotate and revoke keys, at the same path Kalshi uses. A person's session only (the website, or a signed-in CLI's session token): a key can never mint, rotate or revoke a key. - name: Records description: >- Arena's public records: the leaderboards, trader records with their resets, and settled picks. Scope records:read. Arena-owned data only: no exchange tickers, market titles, entry prices or live prices. Points equal paper dollars 1:1. - name: Portfolio description: >- The key owner's own paper account, positions, orders and trades. Scope portfolio:read. Send X-Arena-Org to read an organization sandbox instead. Arena-owned data only while the venue-data switch is off. - name: Markets description: >- Arena's instruments and games, venue quotes, and POST /backtest (a paper game-winner replay). Scope markets:read. Venue references and prices only while the venue-data switch is on. - name: Trading description: >- Place and cancel paper orders for the key owner. Scope trade:write, which a key carries only when its creator asked for it. Send X-Arena-Org to trade that organization's paper sandbox. Paper only: nothing is sent to any venue. - name: Usage description: >- Where the key's account stands against its plan. Any valid key; never counted. externalDocs: description: Arena API docs url: https://docs.arena-predictions.com paths: /portfolio/orders/{orderId}: delete: tags: - Trading summary: Cancel a paper order description: >- Cancels a resting paper order and returns its hold. Kalshi's path and answer (the order and reducedBy). Send X-Arena-Org to cancel on that organization's paper sandbox; without the header the cancel is on the personal account. An unknown or forbidden organization cancels nothing. An order that already filled or closed answers unchanged with reducedBy 0, so a cancel is safe to send twice. No ticker, title or price in the answer while the venue-data switch is off. operationId: cancelOrder parameters: - name: X-Arena-Org in: header required: false schema: type: string maxLength: 63 description: >- Organization id. When present, this call uses that organization's paper sandbox. When absent, the key owner's personal paper account. A value that is not an organization id is 400 invalid_request. An unknown organization is 404 organization_not_found and one this key cannot use is 403 organization_forbidden. The personal account is never the fallback. Paper only. This header does not select a Combine evaluation account. - name: orderId in: path required: true schema: type: string format: uuid description: The order's id (orderId in GET /portfolio). responses: '200': description: The order, and how many contracts came off the book. headers: RateLimit-Limit: $ref: '#/components/headers/RateLimit-Limit' RateLimit-Remaining: $ref: '#/components/headers/RateLimit-Remaining' RateLimit-Reset: $ref: '#/components/headers/RateLimit-Reset' Arena-Quota-Limit: $ref: '#/components/headers/Arena-Quota-Limit' Arena-Quota-Remaining: $ref: '#/components/headers/Arena-Quota-Remaining' Arena-Quota-Reset: $ref: '#/components/headers/Arena-Quota-Reset' Arena-Plan: $ref: '#/components/headers/Arena-Plan' X-Request-Id: $ref: '#/components/headers/X-Request-Id' content: application/json: schema: $ref: '#/components/schemas/CancelResult' '400': description: 'invalid_request: orderId is not a UUID.' content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: >- Missing, malformed, unknown, revoked or expired key. Carries a WWW-Authenticate: Bearer challenge. content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: >- insufficient_scope: the key does not carry trade:write. organization_forbidden: X-Arena-Org names an organization this key cannot use. Nothing was canceled on the personal account. content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: >- order_not_found: no order with that id on this account. organization_not_found: no organization matches X-Arena-Org. content: application/json: schema: $ref: '#/components/schemas/Error' '429': description: >- rate_limited: over a hard trade limit (always enforced), or over the plan's requests while those limits are enforced; or quota_exceeded. error.retryAfterSeconds equals Retry-After. headers: Retry-After: $ref: '#/components/headers/Retry-After' RateLimit-Limit: $ref: '#/components/headers/RateLimit-Limit' RateLimit-Remaining: $ref: '#/components/headers/RateLimit-Remaining' RateLimit-Reset: $ref: '#/components/headers/RateLimit-Reset' Arena-Quota-Limit: $ref: '#/components/headers/Arena-Quota-Limit' Arena-Quota-Remaining: $ref: '#/components/headers/Arena-Quota-Remaining' Arena-Quota-Reset: $ref: '#/components/headers/Arena-Quota-Reset' Arena-Plan: $ref: '#/components/headers/Arena-Plan' X-Request-Id: $ref: '#/components/headers/X-Request-Id' content: application/json: schema: $ref: '#/components/schemas/Error' '503': description: >- trading_off: trading with API keys is switched off right now. internal_error: Arena could not confirm the cancel; send it again. content: application/json: schema: $ref: '#/components/schemas/Error' security: - apiKey: - trade:write components: headers: RateLimit-Limit: description: The plan's requests per minute (all keys of the account together). schema: type: integer RateLimit-Remaining: description: Requests left in this minute. schema: type: integer RateLimit-Reset: description: Seconds until the minute window resets. schema: type: integer Arena-Quota-Limit: description: The plan's requests per month (UTC). schema: type: integer Arena-Quota-Remaining: description: Requests left this month. schema: type: integer Arena-Quota-Reset: description: Seconds until 00:00 UTC on the 1st. schema: type: integer Arena-Plan: description: none (signed in, without a plan), basic, builder, desk or enterprise. schema: type: string X-Request-Id: description: Quote it when asking for help. schema: type: string Retry-After: description: Seconds to wait before trying again. schema: type: integer schemas: CancelResult: type: object required: - order - reducedBy - mode - venueData properties: order: $ref: '#/components/schemas/OrderDetail' reducedBy: type: integer minimum: 0 description: >- Contracts taken off the book. 0 when the order had already filled or closed. mode: type: string const: paper venueData: type: boolean organization: type: object description: >- Present when X-Arena-Org selected an organization sandbox. Absent on the personal account. required: - id properties: id: type: string format: uuid slug: type: - string - 'null' Error: type: object required: - error properties: error: type: object required: - code - message properties: code: type: string description: Stable machine token. Branch on this, never on message. enum: - invalid_request - unauthorized - invalid_token - insufficient_scope - guest_account - scope_not_available - key_limit_reached - key_not_found - trader_not_found - account_not_found - route_not_found - method_not_allowed - internal_error - session_required - key_creation_limited - rate_limited - quota_exceeded - venue_data_off - instrument_not_found - game_not_found - membership_required - trading_off - idempotency_key_reused - insufficient_balance - market_not_found - no_tradable_listing - market_not_open - market_resolved - no_liquidity - price_moved - trade_not_found - already_closed - order_not_found - organization_not_found - organization_forbidden message: type: string description: Human sentence. May change. retryAfterSeconds: type: integer minimum: 1 description: 'On every 429: the same number as the Retry-After header.' OrderDetail: allOf: - $ref: '#/components/schemas/Order' - type: object required: - type - cancelReason - tradeId properties: type: type: string const: limit cancelReason: type: - string - 'null' description: >- user, expired, not_filled, market_closed, market_resolved, position_closed, and so on. tradeId: type: - string - 'null' format: uuid description: The position it opened or closed, once executed. fillPriceCents: type: - integer - 'null' description: Only while the venue-data switch is on. Order: type: object required: - orderId - action - instrumentId - instrumentLabel - instrumentSide - orderSide - contracts - filledContracts - remainingContracts - limitCents - holdDollars - timeInForce - expiresAt - status - createdAt properties: orderId: type: string format: uuid action: type: - string - 'null' enum: - buy - sell - null instrumentId: type: - string - 'null' instrumentLabel: type: - string - 'null' instrumentSide: type: - string - 'null' enum: - 'yes' - 'no' - null orderSide: type: - string - 'null' enum: - 'yes' - 'no' - null contracts: type: integer filledContracts: type: integer remainingContracts: type: integer limitCents: type: - integer - 'null' description: Your own limit. holdDollars: type: number timeInForce: type: - string - 'null' expiresAt: type: - string - 'null' format: date-time status: type: - string - 'null' statedProbPct: type: - integer - 'null' placedVia: type: - string - 'null' placedPrivate: type: boolean createdAt: type: - string - 'null' format: date-time marketTicker: type: - string - 'null' description: Only while the venue-data switch is on. securitySchemes: apiKey: type: http scheme: bearer bearerFormat: arena_sk_ + 43 base64url characters description: >- Authorization: Bearer arena_sk_... (the x-arena-key header is accepted too). Keys are made in Settings (https://arena-predictions.com/settings#api-keys) or with `arena keys create`, shown once, stored hashed. ````