v3.1 — 2026-07-09

v3.1 — 2026-07-09

Lets the Companion App
store its settings in the gateway's flash, so a companion container becomes
stateless — destroy it, start another on any host, and it restores its
configuration from the gateway. Drop-in upgrade from v3.0: every existing
endpoint, MQTT topic and module behaviour is unchanged, and the additions are
purely a new endpoint pair plus one new config field.

New

• Companion settings blob store. The gateway now offers a small, dumb blob
  store that the companion owns end to end:

  • GET /api/companion/settings → the stored gzip(minified JSON) body as
    application/gzip, or 404 when nothing is stored yet.
  • PUT /api/companion/settings → stores the gzipped body verbatim; replies
    {"ok":true,"bytes":N}.

  The firmware never parses the payload — the companion owns the schema and
  compresses/decompresses at its own end. Writes are atomic: the body streams
  to a temp file on the FATFS partition and is renamed over the live copy only
  once the last byte lands, so an interrupted upload cannot corrupt settings that
  were already good. The blob (/compset.gz) survives OTA firmware updates, is
  capped at 64 KB (real ones are 1–2 KB), and the companion debounces its writes,
  so this costs the flash almost nothing.

  Errors are 400 (empty or truncated body), 413 (too large), 503
  (filesystem not mounted) and 507 (write failed) — in every one of them the
  previously stored blob is left untouched.

• Firmware version in GET /api/config. The response now carries
  "version" (e.g. "3.1.0"). This is how the companion decides whether a
  gateway is new enough to hold its settings; against a 3.0 gateway the field is
  absent and the companion quietly falls back to storing them locally.