`vendor/midstream` is a git submodule of RuView but no `v2/crates/*` depends
on a `midstreamer-*` crate and no Rust source uses one — i.e. it is vendored
but not consumed, the same state `vendor/rvcsi` was in before ADR-097.
ADR-098 evaluates whether to change that. The candidate seams (from the
prompt) were:
1. Streaming / pub-sub for the WS fan-out (today: `tokio::sync::broadcast`
at `wifi-densepose-sensing-server/src/main.rs:4769`).
2. CSI → DSP → event pipeline (today: rvcsi-events::EventPipeline, just
adopted by ADR-097).
3. Multi-source merging / TDM for the ESP32 mesh (ADR-029, ADR-073).
4. Backpressure / flow control between the UDP receiver and downstream
consumers (firmware `stream_sender` ENOMEM; host-side bounded
broadcast channel).
Reading all six midstream workspace crates end-to-end
(`vendor/midstream/crates/{temporal-compare,nanosecond-scheduler,
temporal-attractor-studio,temporal-neural-solver,strange-loop,
quic-multistream}/src/*.rs` — ~3,455 LOC) shows midstream's identity
unambiguously: `Cargo.toml:16` calls itself "Real-time LLM streaming with
inflight analysis", the README frames it as analyzing *LLM token streams*
in real time, and zero hits across the workspace for `csi|wifi|sensing|
sensor`. midstream's abstractions are LLM-token / dashboard-telemetry
shaped; RuView's pipeline is RF-frame / event-detector shaped.
Decisions:
D1 — WS fan-out: keep `tokio::sync::broadcast::channel::<String>(256)`.
midstream offers no equivalent in-process broadcast primitive.
D2 — CSI pipeline: keep `rvcsi-events::EventPipeline` (deterministic,
single-frame-at-a-time, replayable per ADR-095 D9). midstream's
attractor / LTL crates operate on multi-dimensional trajectories,
not validated single CSI frames.
D3 — TDM / aggregator: keep `wifi-densepose-hardware::aggregator` +
firmware-side TDM. midstream has no UDP merger and no cross-device
wall-clock scheduler.
D4 — Backpressure: the firmware ENOMEM rate-limit and the bounded host
`broadcast` channel are correct at each end; midstream's QUIC
primitives don't help the actual UDP+WS topology.
D5 — Carve-out: `midstreamer-temporal-compare` (DTW / LCS / Levenshtein)
is a plausible future-evaluation option if a *second* DTW use case
appears in RuView. RuvSense already has one (`gesture.rs`).
D6 — Carve-out: `midstreamer-scheduler` (deadline-aware, EDF / LLF /
RM) is a plausible future option if the cluster-Pi aggregator ever
takes over real-time scheduling. Today that lives in firmware.
D7 — Submodule: keep `vendor/midstream` pinned at `30fe5eb` as reference
material; do not advance the pin per-release (unlike vendor/rvcsi
under ADR-097 D7) because there is no in-build consumer.
D8 — Docs: cross-reference, don't import. ADR-098 added to
`docs/adr/README.md`.
Status: Rejected (with named re-evaluation triggers in §6 — second DTW use
case, host-side real-time scheduler, midstream gains a CSI adapter, or a
QUIC-to-external-client requirement that WS can't service).
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