/changelog.rss if you’d like to stay ahead of breaking changes.
You can reference the pending API spec under the “version” dropdown menu at the top left. When the actual API is upgraded to this new version, you will see the version marked as “Stable” in the drop-down menu and become the new default on the landing page.
This changelog is a work in progress. As always, we welcome any feedback in our Discord #dev channel!
Recent Updates
Fixed batch order creation to return proper error details when post-only orders cross the market. The response now includes:
- Error code:
"invalid order" - Error details:
"post only cross"
The Backward Compatible:
GET /portfolio/orders endpoint’s event_ticker parameter now supports filtering by multiple events using comma-separated values.Example usage:- Single event ticker queries continue to work as before
- Multiple event tickers return orders from all specified events
Fixed missing fields in Quote responses:
rfq_target_cost_centi_cents, rfq_creator_order_id, and creator_order_id are now properly included in all Quote-related endpoints.The
GET /events endpoint now supports an optional flag, with_milestones, that includes all milestones related to the returned events.Expected release: October 16, 2025The order returned by create order is now the same model as the model returned by get order.
The
GET /v2/incentive_programs and GET /incentive_programs endpoints now return a series_ticker field for each incentive program.Expected release: October 13, 2025The
price_level_structure field has been moved from the event level to the market level. Each market now has its own price_level_structure field.Affected endpoints:GET /trade-api/v2/eventsGET /trade-api/v2/events/:event_tickerGET /trade-api/v2/marketsGET /trade-api/v2/markets/:ticker
price_level_structure field on event objects is now deprecated and will be removed. Please use the field on individual market objects instead.Expected release date: Oct 15th, 2025Fixed the After (fixed):This change may affect integrations that relied on space-separated tags. Please update to use comma-separated tags only.
GET /series endpoint’s tags parameter to properly support tags containing spaces. Previously, the parameter would split on both commas AND spaces, breaking searches for tags like “Rotten Tomatoes”.Breaking Change:- The
tagsquery parameter now only splits on commas (,), not spaces - Tags with spaces (e.g., “Rotten Tomatoes”) now work correctly
- Multiple tags must be comma-separated:
?tags=Rotten Tomatoes,Television
Fixed routing inconsistency where certain collection endpoints required trailing slashes, causing unnecessary 301 redirects for requests without them.Endpoints now returning 200 for requests without trailing slash (previously returned 301):
GET /milestonesGET /structured_targetsGET /multivariate_event_collectionsGET /seriesGET /api_keysPOST /api_keys
/milestones/) will now receive a 301 redirect to the version without the trailing slash, which is the opposite of the previous behavior.Subpenny fields have been added to orders (
taker_fees_dollars, maker_fees_dollars), as well as to public trades (yes_price_dollars, no_price_dollars).Endpoints affected:GET /trade-api/v2/portfolio/ordersGET /trade-api/v2/markets/trades
Fields have been added to all RFQ and quote messages to support subpenny pricing via the dollar normalized price fields.
For more info reference:
Enhanced the existing
GET /portfolio/balance endpoint to include a portfolio_value field that provides the total portfolio value (available balance plus current market value of all positions), both in cents.The
GET /series/fee_changes endpoint now returns user-facing fee type names (quadratic, quadratic_with_maker_fees, flat) instead of internal fee structure names. This change also applies to CustomerIO notifications for scheduled series fee updates.Expected release: October 1, 2025Repeated subscriptions on the same websocket call will no longer error. If passing
the same market tickers as before, no action will be taken. If passing new market tickers,
they will be added to your existing subscription.Additionally, the user may supply WS Command
list_subscriptions to view their existing subscriptions.Expected release: October 1, 2025For optimization purposes, partial fills generated by self-crossing FoK orders are not rolled back.
If a FoK order self-crosses, order execution proceeds based on
self_trade_prevention_type:taker_at_cross: the taker is canceled, execution stops. Any partial fills are executed.maker: the maker is canceled, execution continues. After execution, remaining taker quantity is canceled. Any fills are executed.
Oct 1, 2025.User seeking a simple way to determine the direction of their fill should reference purchased_side. Both BUY YES or SELL NO result in purchased_side = YES. The addition of this field is the first step in standardizing the fills websocket and REST endpoints, which have different conventions for the interpretation ‘side’ and ‘user_action’.Expected Enforce Date: deprecation date for existing fields not yet scheduled.
Added new public API endpoint for getting all of a series’ scheduled fees:
GET /series/fee_changes- Get a series’ fee changes. If query string parameter show_historical is set to true, ALL fee changes previous and upcoming will be shown. If set to false, only upcoming fee changes will be shown
Specifying Expected enforce date:
order_type is no longer required and only limit type orders will be supported.
Price must be supplied based on the underlying market structure. Example usage:Sep 25, 2025WebSocket connections per user are limited by usage tier. The default limit begins at 200 and increases based on API usage tier.
A new WS channel is being introduced for streaming information related to pre-trade communications (RFQs and quotes).
Additional metadata is being added to RFQs on multivarate events (MVEs) that break down their component parts explicitly. Market payloads are also being expanded with these new optional fields that are filled only for MVE markets.
Added new public API endpoint for event candlesticks:
GET /candlesticks- Get candlesticks for all markets associated with an event. If the # of candlesticks exceeds 5000, paginate the results and return an adjustedEndTs which should be used as the start_ts for your next request.
The TypeScript SDK is now available through NPM! Install with
npm install kalshi-typescript.Documentation and examples available at docs.kalshi.comAdded new public API endpoint for forecast percentiles history:
GET /forecast_percentiles_history- Get percentile history of a event forecast
Added new public API endpoint for incentive programs (not yet live):
GET /incentive_programs- List incentive programs with filtering options (by market ticker, active status, payout status)
Subpenny pricing fields have been added to websocket messages. Any message bearing price in cents will now also bear
an equivalent fixed-point dollars field.For more info, see Subpenny Pricing.
Both the individual and batch
GET events endpoints now also return available_on_brokers which indicates that they are available on intermediate platforms/ brokers.The python SDK is being generated from our OpenAPI spec and is available through pip with pip install kalshi-python.
Docs for the new SDK are available on docs.kalshi.com/python-sdk.
Subpenny pricing fields have been added to APIs involving price, fees, and money in general.
E.g. next to a field called
"price": 12 (representing 12 cents), you will also see "price_dollars": "0.1200",
which is a string bearing a fixed-point representation of money accuate to at 4 decimal points.For now, this change is read-only, meaning that the minimum allowable tick size for orders is still 1c. Eventually,
we will introduce sub-penny pricing on orders. For now, please prepare for an eventual migration to the higher granularity
price representation.For more info, see Subpenny Pricing.The market payload has been updated to include two new fields that describe markets which are part of Multivariate Events.
The market payload has been updated to include two new fields that describe markets which are part of Multivariate Events.
The MVE payload has been expanded to support more flexible structures. Several fields that are now redundant are deprecated, but not yet removed.
The Settlements API now includes the settlement value for a yes contract.
The get_milestones endpoint now uses case-insensitive matching for the category parameter, resolving inconsistent filtering behavior between “Sports” and “sports”.
Filtering events by close ts and series by tags supported in the API.
The batch order endpoints are now available to all API users in the demo environment:Affected Endpoints:
POST /portfolio/orders/batched(BatchCreateOrders)DELETE /portfolio/orders/batched(BatchCancelOrders)
- Basic tier users can now access batch endpoints in demo environment
- Production environment remains unchanged - Advanced tier or higher still required
- Rate limits still apply based on user tier
The error messages when an incorrect API signature is passed have been improved
The OpenAPI specification for the Kalshi API is now available at
https://docs.kalshi.com/openapi.yaml. This allows developers to easily generate client libraries and integrate with the API using OpenAPI-compatible tools.Added
client_order_id field to orderbook delta WebSocket messages. This field appears only when you caused the orderbook change and contains the client_order_id of your order that triggered the delta.WebSocket Message Enhancement:- New field:
client_order_id(string, optional) - Present only when the authenticated user’s order causes the orderbook change
- Contains the client-provided order ID of the triggering order
Added
GET /portfolio/orders/queue_positions endpoint for retrieving queue positions of multiple resting orders.Request Parameters:market_tickers(optional): Array of market tickers to filter byevent_ticker(optional): Event ticker to filter by
market_tickers and event_ticker in the request.We are migrating our API documentation to a new platform:
- RSS feed moved from
https://trading-api.readme.io/changelog.rsstohttps://docs.kalshi.com/changelog/rss.xml - Documentation site
trading-api.readme.iois now deprecated - New documentation home:
https://docs.kalshi.com - Historical changelog entries will not be backfilled to the new RSS feed
The GetEventMetadata endpoint has been expanded to include settlement sources.
The GetApiVersion endpoint has been removed. API versioning will not be available for the time being.