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This is not a traditional drop copy session. Kalshi’s Drop Copy uses a request-response pattern for querying historical execution reports. For a real-time streaming feed, use a Listener Session on KalshiRT instead.
Historical execution-report replay through EventResendRequest (35=U1) requires allowlisting for your user account on both KalshiNR and KalshiDC sessions. Contact institutional@kalshi.com to request access. Requests from accounts that are not allowlisted are rejected with EventResendReject (35=U3), reason 5 (NOT_ENABLED). Allowlisting does not backfill earlier events.
Lookback window is limited to the last 3 hours. Only ExecutionReport (35=8) messages are returned. Rejects and pending orders (ExecID "-1;-1") are excluded.
Resent messages have new FIX sequence numbers, different from their original numbers on the order entry session. Use ExecID to reconcile.

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EventResendRequest (35=U1)

Request execution reports within a specified ExecID range. ExecID format is clock;event for exchange index 0 and clock;event;exchange_index for other indexes. Resend ranges are scoped to one exchange index; EndExecID, if provided, must use the same exchange index as BeginExecID. Example:

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EventResendComplete (35=U2)

Sent after all requested events have been resent.

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EventResendReject (35=U3)

Sent when a resend request cannot be fulfilled.