Status: ready-for-agent

# 05 — Trace-driven activation compression

## What to build

Make zstd decisions from activation size, measured compression ratio, CPU cost,
and route conditions. Keep small decode payloads on the fast path, avoid
compressing data that does not shrink, and expose enough counters to compare
wire savings against compression latency on LAN and relay routes.

## Acceptance criteria

- [ ] A compression policy is explicit and configurable for LAN, relay, and
  benchmark environments.
- [ ] Bodies that do not meet the configured savings threshold are sent raw.
- [ ] Compression and decompression time plus input/output bytes are reported.
- [ ] Prefill and decode policies can differ; decode latency is not regressed by
  compressing small one-step activations.
- [ ] Tests cover incompressible, compressible, threshold, malformed, and
  legacy-uncompressed bodies.

## Blocked by

- 01 — Baseline and profiling harness.

