Real esptool output on a live Heltec V4 exposed the next layer of the
--no-stub fix: "A fatal error occurred: ESP32-S3 ROM does not support
function erase_flash." The ESP32-S3 ROM bootloader only implements
per-sector erase (used internally as write_flash streams data), not a bulk
full-chip-erase opcode — that's a stub-firmware-only feature, and Debian's
esptool package ships without the stub (hence --no-stub in the first
place).
write_flash's own --erase-all flag gets the same "erase everything before
writing" outcome our "always erase before write" default requires, but via
the per-sector mechanism the ROM bootloader actually supports — one esptool
invocation instead of a separate erase_flash + write_flash pair.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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