Updates & signing

There is no custom “firmware.” usb.plan.ai ships software on a standard drive, so “updates” means a signed app/update pipeline, not a hardware firmware flash. (If a branded hardware SKU ever ships, firmware gets its own doc.)

The chain

Need	Tool	Notes
Signed releases	cosign (sign-blob --bundle)	Sign release ZIPs, SBOMs, and the model manifest.
Rollback-safe updater	The Update Framework (TUF)	Signed metadata, expiry, version counters, target hashes, delegated roles.
Delta updates	xdelta3 patches as TUF targets	Verify patch SHA → apply into a staging dir → verify final tree SHA → switch.
SBOM	syft (-o cyclonedx-json)	One per release.
Rollback	Versioned dirs: app/versions/1.0.4/ + app/current-version.txt	Keep the last known-good. Avoid symlinks; exFAT doesn’t do them.
Runtime integrity	preflight-check	Verifies release manifest, engine binary hashes, model SHA-256, and license notices before launch.

Update flow

download TUF metadata → verify signatures + expiry
  → download full ZIP or xdelta3 patch → verify SHA
  → apply into app/versions/<new>/ (staging)
  → smoke test → atomically update current-version.txt

Model packs update separately. They are content-addressed by SHA-256, so a small app patch never rewrites 20 GB+ GGUF files. See the software stack for the models.lock.json shape and the security model for the threat boundary.

Sources: cosign / Sigstore · The Update Framework · syft. Pin exact tool versions per release.