[cfremling]

trigger_exposure() set SEQ_WAIT_EXPOSE after camerad's reply to expose and the EXPOSING database write. The async listener clears that bit on the first PIXELCOUNT and disarms. With EXPTIME 0 readout starts immediately, so PIXELCOUNT can arrive before the set; the bit is then set with nothing left to clear it and sequence_start waits on it forever. The set now happens before the command is sent.

Example, 2026-09-08 UT, CAL_BIAS id 112442 (NEXP 7, EXPTIME 0):

sequencerd_20260909.log
23:34:23.064  trigger_exposure  sending expose command
23:34:23.654  target CAL_BIAS id 112442 state exposing
23:34:23.654  waiting for exposure            <- "done waiting for expose" never follows
camerad_20260909.log
23:34:23.389  do_expose  expose is done now!   <- reply
23:36:57.585  ngps_260909_0021.fits closed; ready for next exposure

Wait bits stayed EXPOSE READOUT. Every earlier bias in the logs cleared EXPOSE 28-45 ms after "waiting for exposure".

The database part (integer keys matched with like) is now #511.

Rebuild, restart sequencerd. Tested on sky using branch cf/summit-20261030 on 2026-11-03: the evening bias series completed without hanging.

Jira: PAL-164.

🤖 Generated with Claude Code

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[cfremling]

Tested on sky 2026-10-28 UT using branch cf/summit-20261020: the evening calibration set (CAL_BIAS first) ran straight through at 22:51-23:03 UT, where on main both bias series had wedged on 2026-10-21 and needed abort / do all / start.