fix(protocol): correct continuous-mode record header classification for accurate timestamp extraction

minimateplus/client.py

@@ -1638,31 +1638,48 @@ def _decode_a5_waveform(
 
 def _extract_record_type(data: bytes) -> Optional[str]:
     """
-    Decode the recording mode from byte[1] of the 210-byte waveform record.
+    Detect the waveform record format by inspecting the first 3 bytes of the
+    210-byte record returned by SUB 0C.
 
-    Byte[1] is the sub-record code that immediately follows the day byte in the
-    9-byte timestamp header at the start of each waveform record:
-      [day:1] [sub_code:1] [month:1] [year:2 BE] ...
+    Two formats exist (confirmed from BE11529 captures and CLAUDE.md docs):
 
-    Confirmed codes (✅ 2026-04-01):
-      0x10 → "Waveform"   (continuous / single-shot mode)
+      Single-shot mode — 9-byte header:
+        data[0]   = day
+        data[1]   = 0x10            ← sub_code marker
+        data[2]   = month
+        data[3:5] = year (BE)
+        ...
 
-    Histogram mode code is not yet confirmed — a histogram event must be
-    captured with debug=true to identify it.  Returns None for unknown codes.
+      Continuous mode — 10-byte header:
+        data[0]   = 0x10            ← marker A
+        data[1]   = day             ← variable (NOT 0x10)
+        data[2]   = 0x10            ← marker B
+        data[3]   = month
+        data[4:6] = year (BE)
+        ...
+
+    Disambiguate by checking BOTH data[0] and data[2]:
+      - data[0]==0x10 AND data[2]==0x10  →  Continuous (10-byte header)
+      - data[1]==0x10                    →  Single-shot (9-byte header)
+      - otherwise                        →  Unknown
+
+    Previous logic only checked data[1] and so mis-classified continuous-mode
+    records as "Unknown(0xXX)" wherever day != 0x10 — see filename
+    M5290000.000 regression report (2026-05-01 SFM log).
     """
-    if len(data) < 2:
+    if len(data) < 3:
         return None
-    code = data[1]
-    if code == 0x10:
-        return "Waveform"
-    if code == 0x03:
-        # Continuous mode waveform record (confirmed by user — NOT a monitor log).
-        # The byte layout differs from 0x10 single-shot records: the timestamp
-        # fields decode as garbage under the 0x10 waveform layout.
-        # TODO: confirm correct timestamp layout for 0x03 records from a known-time event.
+    # 10-byte continuous format: 0x10 markers at byte 0 AND byte 2
+    if data[0] == 0x10 and data[2] == 0x10:
         return "Waveform (Continuous)"
-    log.warning("_extract_record_type: unknown sub_code=0x%02X", code)
-    return f"Unknown(0x{code:02X})"
+    # 9-byte single-shot format: 0x10 sub_code marker at byte 1
+    if data[1] == 0x10:
+        return "Waveform"
+    log.warning(
+        "_extract_record_type: unrecognized header: data[0:3]=%02X %02X %02X",
+        data[0], data[1], data[2],
+    )
+    return f"Unknown({data[0]:02X}.{data[1]:02X}.{data[2]:02X})"
 
 
 def _extract_peak_floats(data: bytes) -> Optional[PeakValues]: