The shape-of-payload dump shipped earlier rules out cache wipes —
shaddowlink's round-1 captures show AMS data reaches the slicer
byte-identical to what the printer sent. The remaining symptom
(picking a generic filament in archive mode "unloads" the slot) lives
on the command path, which the snapshot dump doesn't see: it writes
only the cached _latest_print_state and the periodic 1Hz push.
Add append_event() in _debug.py — same env flag, separate file at
<log_dir>/vp_wire/<vp>_cmd.jsonl. One JSONL line per event with UTC
iso timestamp, direction (slicer_to_bridge / printer_to_slicer), MQTT
topic, <channel>.<command> grep handle, and parsed payload. Wired at
two points: mqtt_server._handle_publish for slicer publishes (after
JSON decode so the trace matches what the bridge actually parsed) and
mqtt_bridge._on_printer_raw "everything else" branch for printer
responses (after serial rewrite so the trace matches what the slicer
sees on the wire). Pushall / get_version stay out — both are handled
locally and never round-trip through the bridge.
Bytes payloads get the same \x00-tolerance fix from #927 so
OrcaSlicer's C-string-null publishes parse cleanly; un-parseable
bytes fall back to {"raw": "..."} so every line stays valid JSON.
maziggy
19eed8eba0