Three fixes:
1. Modem-preset authoritative: parse_config_lora_region now also decodes
modem_preset (field 2) alongside region, tracked as current_modem_preset.
ensure_lora_region's "region already set, don't touch it" branch (correct,
unchanged) now ALSO re-asserts LONG_FAST when a real observed preset has
drifted -- previously modem_preset only ever got written when region was
UNSET, so a radio with the right region but wrong preset was never fixed.
Only acts on an actually-observed wrong value (never speculative), so it
can't reboot-loop.
2. RX-stall watchdog: run_mesh_session now bails (triggering the existing
auto-reconnect path) if no frame has been successfully received in 5
minutes -- the existing consecutive_write_failures counter is blind to a
receive-only stall (writes can keep succeeding while inbound streaming is
wedged).
3. Hot-swap detection: spawn_mesh_listener now compares self_node_id across
session restarts and logs clearly when the physical radio itself changed
(not just an ordinary reconnect of the same board). Per-session device
state (contacts, current_region, etc.) was already naturally isolated
per-session (fresh struct each reconnect) -- nothing else needed clearing.
107/107 mesh tests pass (2 new: modem_preset decode + the
absent-field-defaults-to-LONG_FAST case).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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