Supersedes the segment-header model entirely, including the fixes made
earlier today. Found via multi-agent structural analysis of the 25 files
that stalled the walker, then verified independently.
Records are self-delimiting: off+2 is a uint16 BE length, next_record =
off + 2 + len, and the chain ends on a record whose chan_id is 0x06.
off+8 carries a 3-valued mode enum:
02 00 14-byte header, 2 anchors, then CUMULATIVE delta blocks
01 00 10-byte header, no anchors, blocks are ABSOLUTE values
00 03 10-byte header, NO TAGS AT ALL - raw 12-bit packed absolute
`40 NN` is an ordinary int16 BE data block (2*NN + 2), never a header.
Reading it as a 2*NN + 16 header is what made walks drift — the
"variable-prefix segment descriptors" reported earlier today were not a
format feature, just walker drift of exactly
4 - (old_stop - true_record_start), on all 25 affected files.
Measured on the production snapshot:
all four channels equal length 156/1388 -> 1388/1388
ASCII sample-count exact 72/75 -> 75/75
ASCII fully exact 70/75 -> 73/75
device PPV waveform (live) 1288/1306 -> 1306/1306 (mean err 0.00000)
device PPV histogram (live) 4434/4459 -> 4458/4459
Also eliminates the walker-over-read class: 24 of those 35 files were
histograms that read_blastware_file fed to the waveform codec first; the
old walker accepted them and returned garbage (one yielded 98,923
"intervals"), while the record-chain decoder returns None so they fall
through to histogram_codec.
00 03 records are DECODED, not skipped. Skipping them silently shifts
the time base of everything after them on that channel — BE9558/
K558LOF2.820W had MicL displaced by exactly 512 samples with nothing
marking the gap.
Footer detection now prefers the 0e 08 candidate whose body yields a
chain terminating on 0x06; the signature can occur inside a sample
stream. Blast radius 1 file of 1388.
The superseded model survives as decode_waveform_legacy, pinned by
micromate/idf_file.py: its Thor IDFW body-offset search trial-decodes
candidates and keeps whichever yields the most samples, so the new
decoder returning None where the old returned garbage changes that
heuristic's winner. Deferred until that search uses the record chain.
Tests: 253 passed (+11), failure list unchanged from baseline. The 9
tests pinning the superseded model are retargeted at
decode_waveform_legacy, which still implements it.
NOTE: stored .h5 files need regenerating — nearly all get longer.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
serversdownandClaude Opus 5
9bb95003e9