All problems
TMKR-4001
Warning
Vendor or customer
Heartbeat sequence mismatch (auto-resynced)
A heartbeat arrived with an out-of-order counter; the SDK resynchronises automatically. This is informational and self-healing.Session & heartbeat•Also known as: INVALID_SEQUENCE, invalid-sequence, 409_sequence, heartbeat_sequence_mismatch
Symptoms
Experts log: "SDK Warning: Heartbeat sequence mismatch (HTTP 409), syncing...".
API response error_code: INVALID_SEQUENCE (HTTP 409) with expected/current sequence in context.
Causes
A heartbeat response was lost and retried after a brief disconnect.
The session reconnected and the counters realigned.
How to fix it
If you're the customer (running the product)
1
No action neededThe SDK reads the expected sequence from the response and continues. If you see repeated 409s, your connection is unstable (see TMKR-3003/TMKR-3004).
If you're the vendor (publisher)
1
Don't send heartbeats manuallyLet the SDK own the sequence counter. If you customised heartbeat logic, ensure the counter only ever increases by one per send.