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VerseVDI-Data-Plane/openspec/changes/gateway-candidate-evidence-integrity/design.md
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Context

The native production path and fair pacer already exist. The defect was evidence collection: provider sends waited synchronously for client delivery, RTT was arithmetic, CPU was available capacity, and the repository had no canonical Linux build target.

Goals / Non-Goals

Goals:

  • Observe concurrent source-shaped traversal without a duplicate transport.
  • Distinguish actual one-way delivery, acknowledged RTT, queue/processing/pacing, and consumed process CPU.
  • Produce reproducible inspectable Linux artifacts for the deployment architectures.

Non-Goals:

  • A new transport, scheduler, dependency, codec operation, scanner, signer, or container framework.
  • Live provider/client/firewall evidence or Connection Server image remediation.

Decisions

  • Keep the existing provider fixture and production path; overlap its UDP sender with the public QUIC receiver.
  • Apply fixed-seed impairment before provider UDP injection and derive delivery statistics from decoded payload sequence and timestamps.
  • Use native ENet acknowledgement timing for RTT instead of doubling one-way completion.
  • Use OS process user plus system CPU for the isolated qualification command; retain memory, goroutine, and allocation series separately.
  • Build both Linux architectures with CGO_ENABLED=0, GOWORK=off, -trimpath, no VCS stamping, and an empty build ID, then inspect ELF and embedded Go settings.
  • Delete the dead exported pacer rather than consolidate it with the sole production fairPacer.

Risks / Trade-offs

  • [Short RTT smoke runs contain ENet smoothing history] → Classify the metric as acknowledged transport RTT and enforce profile tolerances on the full frozen run.
  • [Process CPU includes the bounded fixture/client harness] → Run only the named qualification test in an isolated process and label the scope exactly; never call it host-wide or binary-only CPU.
  • [No qualifying vulnerability scanner is installed] → Record unscanned status and deterministic dependency/artifact evidence without zero-finding claims.