After a Polymarket WebSocket disconnect, reconnecting does not restore missed updates. Re-subscribe, rebuild the public order book from a fresh book event, and reconcile private account state by fetching open orders and recent trades before applying new user-stream events. Treat cached data as stale until those steps are complete.
Know which state you need to recover
Polymarket has separate real-time streams for public market data and private account activity. The market stream carries order-book and market updates; the authenticated user stream carries order and trade updates. They require different recovery steps.
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- Market state: The current real-time data documentation uses outcome asset IDs for market subscriptions. Events include
book,price_change,last_trade_price, andtick_size_change. Polymarket Real-Time Data - Account state: The user stream requires CLOB credentials and can be filtered by condition IDs. Its events report order and trade activity. Polymarket Order Updates
A public market feed is not a substitute for private account reads, and neither stream should be assumed to replay everything missed during an outage.
Reconnect and subscribe to the right stream
- Detect the outage. Track close and error conditions, as well as heartbeat failures, so the client can mark affected cached state stale.
- Reconnect to the appropriate channel. Market and user channels use an application-level
PINGevery 10 seconds and respond withPONG. Treat these as heartbeat messages, not market or account events. Polymarket Real-Time Data and Polymarket Order Updates - Send a subscription promptly. Subscribe to market data using outcome asset IDs. Subscribe to the user channel with CLOB credentials and, if useful, condition ID filters; the documentation notes that an unsubscribed user connection may be closed. Keep credentials on the server side. Polymarket Real-Time Data and Polymarket Order Updates
Rebuild the market book from a fresh event
Do not apply incoming price changes to the book that was in memory before the disconnect. Invalidate that book when connectivity is lost, then wait for a fresh book event and replace the local representation with its bids and asks. Apply subsequent price_change events only after that replacement.
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This is a conservative client design, not a documented replay or gap-repair protocol. Polymarket’s reviewed documentation describes book snapshots and change events, but does not establish replay of missed market events, guaranteed ordering across reconnection, or sequence numbers for detecting and repairing a gap. A reconnect alone therefore cannot prove that a cached book is exact. Polymarket Real-Time Data
Reconcile private orders and trades
For account state, Polymarket’s documented recovery procedure is explicit: after reconnecting, fetch open orders and recent trades, then continue consuming new user-stream events. Do not rely on the event feed alone to recover changes made while disconnected. Polymarket Order Updates
Use stable order and trade identifiers where available to apply events idempotently, so duplicate notifications do not create duplicate local records or actions. This is a client-side reliability practice, not a protocol guarantee.
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Preserve trade lifecycle states
A matched trade is not necessarily settled. Trade updates may pass through MATCHED, MINED, CONFIRMED, RETRYING, and FAILED. Keep these states distinct: confirmation and permanent failure are terminal, while a retry can later be mined and confirmed. Polymarket Order Updates
Refresh constraints before placing orders
Before submitting orders after recovery, refresh relevant market metadata and constraints, especially tick size. Polymarket’s maintained integration guidance warns that continuing to use an old tick size after a tick-size change can lead to rejected orders. Polymarket Real-Time Data and Polymarket integration guide
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Keep the documented wire formats distinct
The current Real-Time Data page presents a unified SDK-style envelope with topic, type, and payload. A Polymarket-maintained integration guide also shows a legacy raw CLOB format using fields such as event_type, assets_ids, and price_changes; in that legacy example, a level with size: "0" is removed. Do not combine field names from the two examples into one assumed schema. Follow the format for the client or endpoint you are actually using. Polymarket Real-Time Data and Polymarket integration guide
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A safe recovery sequence
- Mark the local book and account cache stale on disconnect.
- Reconnect and restore the heartbeat; send the correct market or user subscription.
- For the market stream, replace the old book only when a fresh
bookevent arrives, then apply later changes. - For the user stream, fetch open orders and recent trades, reconcile the local account view, and then apply new events idempotently.
- Refresh tick size and other relevant constraints before sending orders.
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