NAK-triggered repacketization

For a missing full base-record DATA frame, stock's response to the caller's state query is called-keyed 288/1117. Independent stock-to-stock recordings at BW2300 (2026-09-19) and BW2750 (2026-09-12) show the caller restarting with the first 22 unconfirmed bytes at record 1 / 101, then returning to base records with the remaining stream. All three decoded frames in each capture have clean CRCs; the lower frame's full-body field is 0x99 in the 393-byte experiment.

Kestrel now prepares that smaller retry for a fresh solicited NAK while a full base frame is pending. It combines the original pending payload with the unsent remainder of the same host delivery, takes 22 bytes for the lower frame, and repartitions the remaining bytes into base frames when at least one full base frame remains. A smaller remainder stays at record 1 / 101 through its closing frame, with full bodies announcing 0x89 (hold record). Later host writes remain separate, and an exact multiple retains its empty closing block.

No acknowledgement is inferred from the NAK. The new pending body and unsent queue replace the old ones only after the retry transmits. A refused write leaves both unchanged. The over number and accumulated retry budget are retained; only a subsequent validated positive reply retires the smaller pending body. A subsequent host delivery starts at the normal base record.

The scope is explicit: a fresh query, an outstanding full base frame, a complete queued delivery boundary, and the normal sender. An unsolicited or short NAK, an explicit transmit-rate ladder, or another record retains the original retry geometry. Continuous SNR-based rate selection remains unimplemented.

The production sender completed clean and first-DATA-erasure experiments against VARA HF 4.9.0 at both wide bandwidths: 393 bytes sent and 225 bytes received, byte-for-byte, with no pending bytes or queued blocks at completion. Independent cable audits verify the erased first waveform, intact query and 288/1117 reply, CRC-clean 22-byte retry, and the exact concatenated continuation. These were virtual-audio tests, with no RF or physical codec use.

Experiment IDs: 20260919T164044Z-2300-* and 20260919T164404Z-2750-*. The initial failed trial is retained separately: its diagnostic driver used an expired idle deadline after synchronous DATA TX, queried across the ACK and duplicated data. The corrected driver restored the production scheduling order; subsequent runs use mail_session directly.

Short 94-byte clean/erasure pairs also pass at both bandwidths, with independent CRC and exact-byte audits. A rejected earlier candidate jumped from the 22-byte retry to a short base closing frame; stock did not accept that unannounced jump. The revised sender holds the lower record through 22/22/22/22/6-byte frames. Experiment IDs: 20260919T165735Z-2300-* and 20260919T165938Z-2750-*. Their captures and failed candidates remain in the private station archive.