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GrandPlan/.claude/memory/packaging-signing-decisions.md
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Packaging & Signing — Key Decisions

Full detail lives in docs/superpowers/specs/2026-07-28-flowfile-packaging-signing-design.md. These are the non-obvious calls worth remembering, several of which reversed an earlier direction during design review:

  • No sidecar fronting ingestion. A claim-check sidecar to bypass NiFi's content repo for large payloads was considered and rejected — all content must transit NiFi for routing/content-assurance controls. The external service's role is post-NiFi only: assembly, stall monitoring, cleanup, catalog DB maintenance.
  • No external signing service. Vault Transit / a network-isolated signer was considered and rejected in favor of in-process signing (Bouncy Castle OpenPGP, key loaded via a Controller Service) to keep the architecture self-contained within NiFi. This is a deliberate non-repudiation trade-off, stated explicitly in the spec — key custody now depends on host-level protection (sensitive-property encryption, restricting which instances have the Controller Service) rather than network isolation.
  • Clear-sign (OpenPGP), not a bespoke signature format. Chosen specifically because an operator on the far side of MR can verify an artifact by hand with stock gpg --verify and a public key — no custom SDK needed. Matters because MR already has a manual-operator recovery model for missing chunks (adopted from the Phat Files design).
  • HMAC was considered and rejected as the integrity mechanism — it detects tampering but can't give non-repudiation, since every verifier necessarily holds the same shared secret and could in principle have forged the tag themselves.
  • Content + JSON trailer as one object, not two. Chosen for end-to-end loss protection: two separate objects (content, manifest) have independent failure/lifecycle/replication paths that can diverge. A single completed write can't end up in a split state.
  • S3 attribute handover defers to an existing, established handover interface spec, not this design's own invention — see open-external-dependencies.
  • S3-vs-XFS storage backend split by file size is unresolved — open question whether S3 can serve small files efficiently enough to drop the XFS tier entirely.