fix(histogram): block is big-endian + terminal block tail — 1/1196 to 1211/1211

Two errors in the series-3 histogram block model, both found by diffing
against the per-interval data table in the preserved Blastware ASCII
exports (1211 files in the prod snapshot — far stronger ground truth
than the header PPV used previously).

1. The block is uniformly BIG-ENDIAN.  Peaks and half-periods are uint16
   BE (T_peak [5:7], T_halfperiod [7:9], V_peak [9:11], V_halfperiod
   [11:13], L_peak [13:15], L_halfperiod [15:17], M_peak [17:19],
   M_halfperiod [19:21]); only block_ctr [2:4] is little-endian.

   The old uint8-peak model silently CLIPPED any peak above 1.275 in/s:
   the final interval of BE18193/T193LQ9K.OE0H reads 8.270 in/s in BW's
   export (1654 counts = 0x0676) and decoded as 0x76 = 118 = 0.590.

   The byte documented as a per-channel "annotation" was never an
   annotation — it is the half-period's high byte, which is exactly why
   it was non-zero on the sub-Hz intervals BW renders as "<1.0".

   The marker is block[4] alone.  Testing [4:6] as a uint16 LE marker
   forced block[5] == 0, which is what capped the peak at one byte.

2. The final block of each stream carries tail 9c 06 00 42 instead of
   1e 0a 00 00, and holds arbitrary bytes at [21:23].  Rejecting it
   dropped the last interval of nearly every histogram — frequently the
   interval holding the event peak, so the file's PPV read low.

Verified end to end through the production path: 1211/1211 histograms
decode exactly (interval count + every per-interval peak), plus 842,442
per-interval frequency comparisons with zero mismatches.  Previously
1 of 1196 files was fully correct.

decode_histogram_body_full records expose `is_terminal` in place of the
removed `annotations` tuple.  +6 tests.  No regressions: full-suite
failure list unchanged from baseline.

NOTE: stored histogram .h5 files need regenerating to pick this up.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog

docs/instantel_protocol_reference.md

@@ -11,6 +11,7 @@
 
 | Date | Section | Change |
 |---|---|---|
+| 2026-08-25 (2) | S7.6.2, S15 | **HISTOGRAM BLOCK IS BIG-ENDIAN + terminal block tail.** The 32-byte histogram block's per-channel fields are uint16 **big-endian** (`T_peak` [5:7], `T_halfperiod` [7:9], `V_peak` [9:11], `V_halfperiod` [11:13], `L_peak` [13:15], `L_halfperiod` [15:17], `M_peak` [17:19], `M_halfperiod` [19:21]); only `block_ctr` [2:4] is little-endian. The marker is `block[4]` alone - the previous uint16 LE marker test at [4:6] forced `block[5] == 0` and thereby capped every geo peak at 255 counts (1.275 in/s), silently clipping larger peaks. The byte previously documented as a per-channel "annotation" is the high byte of the big-endian half-period, which is why it was non-zero exactly on sub-Hz intervals. Separately, the **final block of each stream carries tail `9c 06 00 42`** rather than `1e 0a 00 00` and holds arbitrary bytes at [21:23]; rejecting it dropped the last interval of nearly every histogram. Verified against 1211 production histograms paired with their Blastware ASCII exports: 1211/1211 decode exactly, plus 842,442 per-interval frequency comparisons with zero mismatches (previously 1 of 1196 files fully correct). |
 | 2026-08-25 | §7.6.1, §15, Appendix E (NEW) | **BODY CODEC + SCALE PASS — five findings, all verified against 75 production events paired with their preserved Blastware ASCII exports.** (1) **Geo full scale is 32000 ADC counts, not 32768** — one decoder unit (16 counts) is exactly 0.005 in/s, so 10.000 in/s = 32000 counts. Consumers dividing by 32768 read every geophone sample and derived peak **2.34% low**; the error scales with amplitude so it was invisible on quiet events and worst on loud ones. 216 per-channel comparisons: 32768 → 151/216 exact (worst 0.238 in/s on a 10 in/s event); 32000 → 216/216 exact, worst 1 LSB. Affects waveforms, histograms and series-4 alike. (2) **Wide-NN RLE `0X NN`** — the 12-bit NN encoding already known for `1X`/`2X` also applies to the `00 NN` RLE tag (runs > 252 samples). (3) **`30 NN` is not capped at NN=0x10** — data-section blocks reach at least 0x18; the length formula was already right. (4) **`40 NN` segment headers are variable width** — NN counts the previous-channel continuation deltas, so the header is `2*NN + 16` bytes; `40 01` and `40 03` occur alongside `40 02`. A header can also appear **tagless** (the NN=0 case): just the 14-byte tail. (5) **The header field documented as a "monotonic uint32 LE counter" is really `[channel_id][00][00][segment_index]`** with 0x46=Tran 0x47=Vert 0x48=Long 0x49=MicL — verified on 1697/1697 segment headers, zero disagreements. Decoders should take the channel from this field, not from rotation position. Items (2)–(5) each caused **silent channel truncation**: an unhandled tag ends the walk and the decoder returns short channels with no error. Corpus result end-to-end: exact 37 → 72, truncated 23 → 3, full-length value errors 15 → 0. New Appendix E documents the field-observed "offset" device fault. |
 | 2026-05-20 | §2, §3, §4.2, §5.1, §5.3, §6, §7.5b, §7.6.1, §7.6.3, §7.6.4, §7.7.2, §7.7.3, §7.7.5, §7.8.4, §7.8.7, §7.9, §8, §11, §12, §13, §14, §15, Appendix D | **DOC AUDIT PASS — accuracy sweep against `CLAUDE.md` + `minimateplus/` code.** Fixed: (1) S3 frames terminate on bare ETX, not DLE+ETX — §2/§3 rewritten. (2) §3 payload layout corrected — byte[1]=flags, byte[2]=SUB (was wrongly labelled DLE/ADDR). (3) §4.2 — probe responses do NOT carry data length; lengths are hardcoded `DATA_LENGTHS` constants. (4) §5.1 — removed stale duplicate "SUB 1C = TRIGGER CONFIG READ" row; SUB 0A lengths corrected from `0x30/0x26` to `0x46/0x2C` (real event / boundary marker). (5) §5.3 — added missing write-frame format (BW_CMD-only doubling, DLE-aware checksum, offset formula, ack format, SUB 71 chunk parameters). (6) §6 — fixed "SUB 06 → channel config read" → event storage range. (7) §7.5b / §8 — added the 10-byte `sub_code=0x03` continuous-mode timestamp variant alongside the 9-byte single-shot layout; peak vector sum location corrected from "fixed offset 87" to `tran_pos − 12` (label-relative). (8) §7.6 / §7.6.1 / §7.6.3 / §7.6.4 — switched compliance-anchor convention from the 10-byte form to the canonical 6-byte `\xbe\x80\x00\x00\x00\x00`; recording_mode confirmed at anchor−8 in BOTH read and write (was wrongly listed as anchor−3 write / anchor−4 read); sample_rate at anchor−6, histogram_interval at anchor−4, record_time at anchor+6; geo_range row added at channel_label+33. (9) §7.7.2 — token byte position corrected from `params[6]` to `params[7]`. (10) §7.8.4 — fi==9 skip marked FIXED (already removed from code); chunk-count totals updated. (11) §7.8.7 — TODO replaced with current state of `_decode_a5_metadata_into`. (12) §7.9 — Histogram Interval upgraded ❓ → ✅. (13) §11 — POLL example wire bytes corrected; SUB 5A row added to checksum table. (14) §13 — device-under-test updated for current primary unit (BE11529 / S338.17). (15) §14 — TCP Idle Timeout fixed (0→2 min); Data Forwarding Timeout units clarified. (16) §15 (renumbered from second §14) — open-question items already resolved in CLAUDE.md closed out. (17) Appendix D — extension taxonomy rewritten to reflect the AB0T timestamp encoding (D.5.2/D.5.3); EXTENSION REFUTED warning replaced with the resolved encoding. |
 | 2026-05-08 | §7.6.1 (RETRACTION) | **❌ RETRACTED — "raw int16 LE 8 bytes/sample-set" body codec was never validated.** The original 4-2-26 confirmation was based on misreading broken-decoder output (full-scale ±32K noise) as evidence the signal had saturated. BW's own 0C peaks for that capture (Tran=0.420 / Vert=3.870 / Long=0.495 in/s) prove the signal was NOT saturated — none of those exceed 13K ADC counts. No event in the project's archive has ever come close to saturation, yet the decoder consistently produces ±32K noise on every event. Conclusion: the body codec is not raw int16 LE; the actual encoding is open. Body byte distribution is heavily skewed (24% `0x00`, 10.5% `0x10`, lots of `10 XX` pairs) — likely a delta encoding with `0x10` as escape, but unverified. Retraction box added at top of §7.6.1; "fully-saturating event" claim removed from channel-identification note. The histogram codec in §7.6.2 IS verified and decoded correctly (different recording mode, 32-byte blocks); use it as a structural hint when reverse-engineering the waveform codec. |
@@ -3037,7 +3038,7 @@ The `.bin` files produced by `s3_bridge` are **not raw wire bytes**. The logger
 | **Sensor Check dropdown byte location** — byte offset in 1A compliance config payload for the "Sensor Check: Before monitoring / After each event / Disabled" setting is NOT YET LOCATED. Confirmed: unit always runs with "Before monitoring" set. Need a capture with "Disabled" to diff. | MEDIUM | 2026-04-08 | Still open |
 | **RV55 DCD/DTR default** — newer Sierra Wireless RV55 firmware does not assert DCD/DTR by default, so the MiniMate Plus never detects TCP disconnect and stays idle instead of resuming monitoring. Root cause: RV55 ACEmanager `DCD Control` setting. Workaround not yet found. | MEDIUM | 2026-04-11 | Still open |
 | **Variable-prefix segment descriptors** — 3 of 75 ground-truth events still truncate. The walk reaches a segment header whose channel-id field is preceded by a *variable-width* prefix (2, 4 or 6 bytes observed; the standard tagless form always has 4), carrying an `01 00` marker instead of `02 00`. The marker is **not** simply an anchor count — `01 00` records appear with both 2- and 4-byte anchor fields in the same file, so prefix width and marker are not yet reconciled. Examples: `BE12599/N599LPNB.JF0W` @1155, `BE12599/N599LPWJ.980W` @849, `BE9558/K558LOF2.820W` @1485. | MEDIUM | 2026-08-25 | Still open |
-| **Histogram codec drops trailing intervals (series-3)** — measured per-interval against the histogram ASCII data table (which carries Tran/Vert/Long peak + freq + PVS per interval), n=1196: the decoded per-interval **values are right** — 1031/1196 (86%) match the ASCII table within 1 LSB across the overlapping prefix — but the interval **count** is short in 1195 of 1196 files. Median 1 interval missing; 1088 files short by 1–2, 65 by 3–10, 39 by 11–100, 3 by more than 100 (max 205). When a dropped interval is the one holding the event peak, the decoded max falls below the device-reported PPV — 169/1196 (14%) of files. This is a termination bug in `histogram_codec.decode_histogram_body`, the same family as the waveform-walker truncation fixed 2026-08-25, and it was untouched by that pass. | MEDIUM | 2026-08-25 | Still open |
+| ~~**Histogram codec drops trailing intervals (series-3)**~~ - **RESOLVED 2026-08-25.** Two errors, both in the block model. (1) The block is **uniformly big-endian**: peaks and half-periods are uint16 BE (`T_peak` [5:7], `T_halfperiod` [7:9], `V_peak` [9:11], ...); only `block_ctr` [2:4] is LE. The old uint8-peak + "annotation"-byte model silently clipped any peak above 1.275 in/s, and the "annotation" byte was really the half-period high byte - non-zero exactly on the sub-Hz intervals BW renders `<1.0`. The marker is `block[4]` alone; testing [4:6] as a uint16 LE marker forced `block[5] == 0`, which is what capped the peak at one byte. (2) The **final block of the stream carries tail `9c 06 00 42`** instead of `1e 0a 00 00`, with arbitrary bytes at [21:23]; rejecting it dropped the last interval of nearly every histogram - often the one holding the event peak. Verified on 1211 production histograms vs their BW ASCII exports: **1211/1211 exact** (interval count + every per-interval peak) and 842,442 frequency comparisons with zero mismatches; was 1/1196. | RESOLVED | 2026-08-25 | Resolved 2026-08-25 |
 | **Micromate (UM-series) IDF decode is ~1000x low** — e.g. `UM11402_20260406130113.IDFW` decodes a Tran peak of 0.0009 in/s against a device-reported 1.1168. Distinct from the Thor IDF path, which decodes sanely. Suspect a different per-count LSB or a body offset that does not hold for UM-series files. | MEDIUM | 2026-08-25 | Still open |
 | **Thor IDF per-count LSB** — after the 32000 geo full-scale correction, series-4 Thor peaks sit at a median 0.983 of the device-reported peak (was 0.960 under 32768). Closer, but the residual ~1.7% suggests Thor uses its own per-count LSB rather than the BW 16-count/0.005 in/s convention. A code comment in `sfm/waveform_store.py` claims Thor's LSB is 0.0003 in/s, which would predict Thor reading *high* — the measurement shows the opposite, so that comment is unverified. | LOW | 2026-08-25 | Still open |