6 October 2026

Listings no longer stack. Every copy of an item for sale is its own listing, with its own listing_id, and amount on a listing is always 1. A commodity with 40 copies for sale appears as 40 listings.

Why: a stacked listing mixed copies that could differ, for example in trade lock, and could not be bought, repriced or tracked one at a time. With one copy per listing, every purchase, edit and WebSocket event refers to exactly one copy, so there are no partial fills, stack splits or amount edits to reconcile.

The release runs under maintenance mode: authenticated REST calls return 503 MAINTENANCE_MODE until it ends, while the WebSocket stays up. During maintenance every existing stacked listing is split into single-copy listings and the WebSocket feed announces it: listing.amount_changed with new_amount: 1 for each original listing, and listing.created for each new copy. The new copies keep the original listing's created_at, so these listing.created events can carry old timestamps. Private listings are split without events. Once maintenance ends, resync your local book from GET /public/v1/book to be safe.

What you need to do

Resync after maintenance. Rebuild your local book from GET /public/v1/book, and refetch your own listings from GET /public/v1/my-listings.
Keep every listing_id. Listing and selling create one listing per copy, and POST /public/v1/list returns all of them. Store every id, not just the first.
Stop sending amount on edits. PATCH /public/v1/list no longer accepts amount and fails with BAD_REQUEST if you send it. To sell more copies list them; to sell fewer, delist them.
Buy several copies with several lines. On POST /public/v1/purchase every line's amount must be 1; send one line per listing. amount above 1 is rejected, normally with LISTING_OUT_OF_STOCK.
Expect LISTING_NOT_FOUND when you lose a race. A sold copy's listing is gone, so buying, repricing or delisting it returns LISTING_NOT_FOUND.
Use the bulk forms for many copies. Send listing_ids to reprice up to 500 listings at one price, or to delist up to 500 at once.
Check your bulk error handling. A bulk delist or reprice is all or nothing, and the error does not say which id failed. If a copy sold since you read your listings, refetch them and retry with the ids still there.
Handle LISTING_DISABLED. Listing can now be switched off site-wide. While it is off, listing, repricing and delisting fail with 503 LISTING_DISABLED; retry later.

Changed

Area	Before	Now
Listing `amount`	Number of copies in the stack	Always `1`
`POST /public/v1/list`	One listing per group	One listing per copy; the response lists every listing created
`POST /public/v1/sell`	One listing per group once the trade is accepted	One listing per copy
`PATCH /public/v1/list`	Edits `price` and `amount`; lowering `amount` with a new `price` split the stack	Edits the price only, with `price` or `price_decay` as before
`POST /public/v1/delist` bulk	Up to 50 ids, each removed on its own with a per-id `ok` / `error`	Up to 500 ids in one transaction: if any id is missing (`LISTING_NOT_FOUND`) or not yours (`FORBIDDEN`), the call fails and nothing is removed, without saying which id. On success every id comes back with `ok: true`
`POST /public/v1/purchase`	A line could buy several copies of a stack	Every line buys one listing; `amount` must be `1`
`POST /public/v1/purchase` losing a race	Usually `LISTING_OUT_OF_STOCK`, while the stack still had copies left	`LISTING_NOT_FOUND`: a sold copy's listing is removed. `LISTING_OUT_OF_STOCK` now only means a line asked for more than `1`
`GET /public/v1/my-listings`	One row per stack	One row per copy. On commodities, `available_amount` is how many more copies you could list from your backpack; otherwise `0`
`GET /public/v1/my-listings/value`	`listing_count` up to `item_count`	`listing_count` equals `item_count`
`GET /public/v1/book` and `GET /public/v1/listings`	One row per stack	One row per copy, so payloads are larger for commodity-heavy games
`GET /public/v1/prices/all`	`listing_count` up to `stock`	`listing_count` equals `stock`
WebSocket `listing.amount_changed`	Any stock change	Sent when a listing sells (`new_amount: 0`), and once with `new_amount: 1` per split listing during this release
WebSocket `listing.created`	Not sent for listings created from a Steam sell	Sent for every public listing, including those created when a Steam sell trade is accepted
WebSocket `listing.price_changed`	Not sent when an auto-decaying price dropped	Sent for every price change, including each auto-decay step

Event volume rises with the number of copies. Listing and selling send one listing.created per copy; buying sends one listing.amount_changed and one listing.sold per copy; delisting sends one listing.removed per copy; a bulk reprice sends one listing.price_changed per listing whose price changed.

Added

Area	What
`PATCH /public/v1/list`	A `listing_ids` form: up to 500 listings, each id once, set to one `price` or `price_decay` in one transaction. Fails as a whole if any id is missing, not yours, not active or below the item's minimum price. Returns `{ listings }`
`LISTING_DISABLED` error	`503` from `POST /public/v1/list`, `PATCH /public/v1/list` and `POST /public/v1/delist` while listing is switched off site-wide. The bulk `listings` form of `PATCH /public/v1/list` reports it per row in `results` instead

Removed

Area	What
`PATCH /public/v1/list`	The `amount` field, and with it the partial reprice that split a stack

What you need to do

Changed

Added

Removed

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