# quic_ecs_dt — Project Guide for Claude

## What & why

Source repo for **"QUIC + ECS as Complementary Transport and Runtime Substrates for Industrial Digital Twins"** — UCAmI 2026 (Plantevin & Francillette, UQAC). Third paper in a sequence; the first two are at IEEE SWC 2026:

- `plantevin2026ecs` — ECS as runtime substrate for industrial DT (200k assets @ 114 Hz on Pi 5).
- `plantevin2026quic` — QUIC partial reliability for DT sensor streams (94% P99 reduction vs TCP at 5% loss).

**UCAmI hypothesis (the composition question):** prior work shows ECS and QUIC each work as substrates *independently*. Does integrating real QUIC traffic into a Bevy ECS ingest path introduce coupling that degrades either one's claimed properties? The paper argues no, and measures it.

## Architecture

Three-tier QUIC ↔ ECS bridge, headless Bevy runtime. **T1/T2 are inbound (device → substrate); T3 is outbound (substrate → device, actuator commands):**

| Tier | QUIC primitive | Direction | Use case | Channel cap | Sender |
|------|----------------|-----------|----------|-------------|--------|
| T1 | Unreliable datagrams (RFC 9221) | device → substrate | High-freq ephemeral telemetry; drops OK | 1024 | `T1Sender::send_lossy` (try_send, drop on full) |
| T2 | Unidirectional streams | device → substrate | Ordered threshold events; reliable | 512 | `T2Sender::send` (await, backpressure) |
| T3 | Bidirectional streams | **substrate → device** | Actuator commands w/ ACK | 256 | `T3OutboundSender::try_send` of `OutboundT3 { target_device, sensor_id, raw_value, sensor_type }` |

QUIC server runs on a dedicated OS thread with a Tokio multi-thread runtime. T1/T2 decoded `QuicMessage`s (39 B fixed LE: UUID + sensor_id + f64 + ts + seq + sensor_type) flow into per-tier `tokio::sync::mpsc` channels and are drained by Bevy's `ingest_system` in `PreUpdate`, gated by `run_if(in_state(ServerState::Started))`. T3 flows the other way: `automation_system` constructs `OutboundT3` items and the tokio-side `drain_outbound_t3` task opens bi-streams to the target device. The per-tier sender newtypes (in [substrate/src/transport/mod.rs](substrate/src/transport/mod.rs)) make tier mixups a type error. Pattern is in [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs).

**T3 actuator-command protocol.** The substrate's `automation_system` decides to actuate (e.g. Presence < 1.0 ⇒ Relay = stop) and pushes an `OutboundT3` onto the outbound channel. The tokio drain task pops it, looks up the target device's `quinn::Connection` in a `ConnectionRegistry` (populated by `read_datagrams` / `read_one_uni_stream` on first sight of each device UUID), then **spawns one task per command** to do `conn.open_bi() → write 39 B → finish → read 39 B ack`. Per-task spawning means a single stuck `read_exact` can't stall the pipeline. Latency from `open_bi()` to ack-receipt is recorded as `substrate_latency_us{tier="t3"}` and a successful ack increments `substrate_received_total{tier="t3"}`. Misses (`substrate_t3_outbound_no_route_total`), drops (`substrate_t3_outbound_dropped_total`), and bi-stream errors (`substrate_t3_outbound_errors_total`) each have their own counter.

**Connection registry.** `Arc<std::sync::RwLock<HashMap<Uuid, quinn::Connection>>>`. `quinn::Connection` is internally `Arc`; one simulator process commonly hosts 7 device UUIDs sharing one connection. Registry insert is idempotent (`ensure_registered`). On `conn.closed().await` returning, `handle_incoming` purges every key whose `Connection::stable_id()` matches the closed connection.

**Target hardware:** CM5 (BCM2712, Cortex-A76, 4 GB) as DT runtime; M4 Max as traffic generator; 1 Gbps direct Ethernet. Both rigs are in hand.

## Repo map

```
quic_ecs_dt/
├── paper/                Quarto + LNCS source — single index.qmd, refs in references.bib
├── substrate/            Rust crate: Bevy 0.18 + Quinn 0.11 + rustls 0.23 + Tokio
│   └── src/
│       ├── main.rs       App::new, MinimalPlugins, EcsQuicTransportPlugin
│       ├── config.rs     figment chain: defaults → config.toml → APP_* env
│       └── transport/
│           ├── mod.rs    QuicMessage struct
│           ├── ecs.rs    Plugin: tokio thread + 3 mpsc + PreUpdate ingest
│           └── server.rs run_substrate_server (EMPTY STUB)
├── simulator/            Rust crate: stub today; will be Quinn client + Bevy sensor generators
├── data/                 (created by M6) loopback/, two_machine/ — raw CSVs committed, *_processed ignored
├── Cargo.toml            workspace
└── Makefile              render, preview, build, build-cm5, deploy-cm5
```

## Status

| Area | State |
|------|-------|
| `AppConfig` figment loader (defaults → TOML → env, `__` split) | Done — [substrate/src/config.rs](substrate/src/config.rs) |
| Inbound bridge scaffolding (Tokio thread + Bevy plugin) | Done — [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs) |
| `QuicMessage` struct + 39 B LE codec | Done — [substrate/src/transport/mod.rs](substrate/src/transport/mod.rs); 5 unit tests passing |
| Quinn server lifecycle | Listener up — `ServerState{Starting,Started}` in [substrate/src/transport/state.rs](substrate/src/transport/state.rs); `OnEnter(Starting)` → bind + accept loop in [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs). Explicit `TransportConfig` w/ tuned datagram recv buffer (256 KiB) in [substrate/src/transport/server.rs](substrate/src/transport/server.rs). Per-tier sender newtypes (`T1Sender::send_lossy`, `T2Sender::send`, `T3OutboundSender::try_send`) in [substrate/src/transport/mod.rs](substrate/src/transport/mod.rs) |
| T1 demux (datagrams → ECS) | Done — `handle_incoming` orchestrator + `read_datagrams` reader in [substrate/src/transport/server.rs](substrate/src/transport/server.rs); decode errors logged but non-fatal; channel-full drops silent at trace; received/dropped/decode_errors counters in the end-of-stream debug line. Calls `ensure_registered` on first decode so outbound T3 can route to this device |
| T2 demux (uni streams → ECS) | Done — `read_uni_streams` accepts streams in [substrate/src/transport/server.rs](substrate/src/transport/server.rs), spawns one task per stream that reads 39 B chunks until EOF; decode failure resets the stream via `recv.stop(0)` (one bad stream doesn't kill the connection); `t2.send().await` honours backpressure; first decode also calls `ensure_registered` |
| T3 outbound (ECS → device, substrate-initiated) | Done — `drain_outbound_t3` task in [substrate/src/transport/server.rs](substrate/src/transport/server.rs) pops `OutboundT3` items, looks up the target device's `Connection` in `ConnectionRegistry`, **spawns one task per command** to do `open_bi → write 39 B → finish → read ack`. Per-task spawning ensures one stuck ack can't stall the pipeline. Records `substrate_latency_us{tier="t3"}` on success; counts no-route, dropped, and error cases separately. The old simulator-initiated T3 inbound path (`T3Sender` / `T3Inbound` / `accept_bi_streams`) is **gone** as of this refactor |
| Connection registry (Uuid → Connection) | Done — `Arc<RwLock<HashMap<Uuid, quinn::Connection>>>` populated by readers; purged in `handle_incoming` after `conn.closed().await` using `Connection::stable_id()`. Constructor `new_connection_registry`; idempotent insert via `ensure_registered` |
| TLS / self-signed cert | Done (M1) — `certs/server.{crt,key}` via `make certs`, gitignored. PEM loader in [substrate/src/transport/server.rs:15](substrate/src/transport/server.rs#L15); rustls `aws-lc-rs` default provider installed in [substrate/src/main.rs](substrate/src/main.rs) |
| Wire codec for `QuicMessage` (39 B fixed LE, incl. `sensor_type: u8`) | Done — [substrate/src/transport/mod.rs](substrate/src/transport/mod.rs); 5 unit tests passing. `SensorType` enum: `Generic / Temperature / Humidity / Pressure / Voltage / Current` |
| `tracing-subscriber` init w/ `RUST_LOG` | Done (M1) — [substrate/src/main.rs:8-12](substrate/src/main.rs#L8-L12) |
| ECS components (`RawSensorData`, `SmoothedValue`) + 4 systems (Ingest/Sim/Export/Diagnostics) | Done — entities = `(DeviceId, SensorId, SensorTypeTag, RawSensorData, SmoothedValue, Asset)` per (device, sensor); `SensorRegistry` upserts via `HashMap<(Uuid, u16), Entity>` in [substrate/src/world.rs](substrate/src/world.rs). `IngestSystem` drains all three tiers; T3 ack preserves command's `sensor_type` and returns the device's most recent `raw_value`. `SimulationSystem` maintains a 16-sample rolling mean per entity and emits `substrate_threshold_crossings_total{type, direction}` when the smoothed mean crosses a per-type threshold (`Changed<RawSensorData>` query so cost scales with ingress, not fleet size). `ExportSystem` samples `substrate_{entities,channel_depth,channel_capacity,rss_bytes}` + `sensor_aggregate{type, stat}` once per second. `Diagnostics` logs `tick_hz` once per second |
| Schedule rate-gating | Done (M4) — `MinimalPlugins.set(ScheduleRunnerPlugin::run_loop(1/tick_rate_hz))` in [substrate/src/main.rs](substrate/src/main.rs); replaces the default busy-loop with the configured period |
| Prometheus exporter + Grafana dashboards | Done (M5) — `ObservabilityPlugin` in [substrate/src/observability.rs](substrate/src/observability.rs) installs `metrics-exporter-prometheus` on the existing tokio runtime. **Runtime surface** (paper §Evaluation): counters `substrate_received_total{tier}`, `dropped_total{tier=t1}`, `decode_errors_total{tier}`, `t3_no_handler_total`; latency histograms `substrate_latency_us{tier}`; gauges `substrate_tick_hz`, `substrate_entities`, `substrate_channel_depth{tier}`, `substrate_channel_capacity{tier}`, `substrate_rss_bytes`. **Sensor data surface** (operator dashboard): per-type aggregates `sensor_aggregate{type, stat=count|mean|min|max}` computed once per second over the live world, cardinality bounded by `\|SensorType\| × 4` so it scales to thousands of sensors. Two dashboards: [dashboards/runtime.json](dashboards/runtime.json) and [dashboards/sensors.json](dashboards/sensors.json) (thermometer/gauge/stat panels per type) |
| Simulator (Quinn client + sensor generators) | `SimulatorClient` lib in [simulator/src/client.rs](simulator/src/client.rs) — connects, trusts the substrate's PEM cert via custom `ServerCertVerifier` (sidesteps `CaUsedAsEndEntity`); `send_datagram(QuicMessage)` for T1, `send_uni_stream(&[QuicMessage])` for T2. `SimulatorClient::request` exists for ad-hoc tests but the binary no longer initiates T3. CLI driver in [simulator/src/main.rs](simulator/src/main.rs) with clap flags (`--addr`, `--rate-hz`, `--t2-rate-hz`, `--count`, `--devices`, `--sensor-id`, `--sensor-type`, `--profile`, `--cert`, `--server-name`). `--profile industrial` fans out to **7 sensors per device** (Temperature/Humidity/Pressure/Voltage/Current/Presence/Relay). T1/T2 emitters check `engine_running` per-tick — Voltage stays at ~230 V regardless; Current drops to ~0 when stopped. HTTP trigger on `:9002` (`POST /trigger`) pushes a Presence=0 reading via T2 for Grafana-driven demos |
| Simulator command receiver (substrate → device T3) | Done — `run_command_receiver` in [simulator/src/commands.rs](simulator/src/commands.rs) loops on `conn.accept_bi()`, decodes 39 B, sets `engine_running` from `raw_value` when `sensor_type == Relay`, writes 39 B ack. Spawned by `main.rs` post-connect. `new_engine_state()` constructor exported for integration tests |
| End-to-end test harness | 18 tests across [simulator/tests/end_to_end_t1.rs](simulator/tests/end_to_end_t1.rs), [simulator/tests/end_to_end_t2.rs](simulator/tests/end_to_end_t2.rs), [simulator/tests/end_to_end_full_loop.rs](simulator/tests/end_to_end_full_loop.rs): T1 single-datagram + 32-msg burst order; T2 single-stream + 4-stream concurrent ordering; **full closed loop** (Presence < 1.0 → substrate T3 → simulator `engine_running` flips, then Presence > 1.0 → flips back). Plus codec + world unit tests including `automation_dispatches_relay_stop_when_presence_drops` |
| `config.toml` at repo root | Done — [config.toml](config.toml); loaded by [substrate/src/main.rs](substrate/src/main.rs); env override via `APP_*` with `__` split (`Env::prefixed("APP_").split("__")`) actually works now |
| Benchmark harness (sweep + CSV writer) | Done — [scripts/bench-loss.sh](scripts/bench-loss.sh) for entity×loss → `data/two_machine/final_table.csv`; [scripts/bench-scaling.sh](scripts/bench-scaling.sh) for T1 rate sweep with optional substrate-side synthetic T3 (`T3_RATE_HZ=100 ./scripts/bench-scaling.sh` enables `APP_NETWORK__SYNTHETIC_T3_RATE_HZ`) → `data/local/cross_tier.csv`. The synthetic driver lives in `accept_loop` and pushes through the same outbound channel `automation_system` uses |
| CM5 cross-compile / deploy | Wired in [Makefile:30](Makefile#L30); first trial run completed (commit `272d3b3`); [scripts/setup-cm5.sh](scripts/setup-cm5.sh) provisions the Pi |

`cargo run -p substrate` boots, prints the loaded config, and idles on the (still-empty) Quinn server. `MinimalPlugins` busy-loops the ECS schedule by default — expected, will gate to `tick_rate_hz` in M4.

## Roadmap

Each milestone has one verification gate. Update Status here as we go.

- **M1 — Wire codec & root config.** ✅ Done 2026-05-04. Hand-rolled little-endian codec on `QuicMessage` (38 B fixed: 16 UUID + 2 stream_id + 8 f64 + 8 ts_us + 4 seq) with roundtrip + layout + length-error tests; `config.toml` at repo root; dev TLS via `make certs`; structured `tracing-subscriber` init reads `RUST_LOG` (default `info`).
- **M2 — Quinn server + self-signed TLS.** ✅ Done 2026-05-06. Listener up under `ServerState::Starting/Started`; type-system tier semantics + T3 oneshot ack protocol; per-connection `handle_incoming` orchestrator joining T1 datagram, T2 uni-stream, and T3 bi-stream readers. T1 has dropped/decoded counters; T2 resets a stream on decode failure without killing the connection; T3 ships `T3Inbound { command, reply }` to the ECS and resets the stream when no handler answers. End-to-end coverage: 6 integration tests in [simulator/tests/](simulator/tests/) plus 4 codec unit tests, all green.
- **M3 — Simulator client.** Replace [simulator/src/main.rs](simulator/src/main.rs) with a Bevy app: Quinn client, N synthetic devices, configurable per-tier rates. *Verify:* end-to-end loopback drains messages on all three tiers. **Status (2026-05-05):** simulator made into a lib + bin; `SimulatorClient::{connect,send_datagram,close}` plus a manual smoke runner in `simulator/src/main.rs`. Two integration tests in `simulator/tests/end_to_end_t1.rs` exercise the full T1 path against an in-process substrate. Bevy-driven generator + T2/T3 helpers + load profiles still pending.
- **M4 — ECS world.** ✅ Done. `Asset` + `DeviceId` + `SensorId` + `SensorTypeTag` + `RawSensorData` + `SmoothedValue` components in [substrate/src/world.rs](substrate/src/world.rs); `SensorRegistry` resource for O(1) `(Uuid, u16) → Entity`. `IngestSystem` drains all three tiers (T1 batched, T2/T3 fully); T3 handler returns the latest sensor value as ack. `SimulationSystem` runs a per-entity 16-sample rolling mean and emits `substrate_threshold_crossings_total{type, direction}` on per-type threshold crossings — gives the ECS observable digital-twin work, not just write-through ingest. `ExportSystem` samples `substrate_{entities,channel_depth,channel_capacity,rss_bytes}` + `sensor_aggregate{type, stat}` once per second. `DiagnosticsSystem` logs tick rate once per second. Schedule rate-gated via `ScheduleRunnerPlugin::run_loop(1/tick_rate_hz)`. 8 unit tests passing (entity create, in-place update, T3 ack, SmoothedValue push/window/non-finite/full-roll, threshold-crossing transition).
- **M5 — Observability (VictoriaMetrics + Grafana).** ✅ Done. Wire format extended to carry `sensor_type: u8` (38 → 39 B, decoded into `SensorType` enum). Two metric surfaces over `metrics-exporter-prometheus`:
  - **Runtime** (paper §Evaluation): `substrate_received_total{tier}`, `dropped_total{tier=t1}`, `decode_errors_total{tier}`, `t3_no_handler_total`, `latency_us{tier}` histograms, `tick_hz` / `entities` / `channel_depth{tier}` / `rss_bytes` gauges.
  - **Sensor data** (operator surface): `sensor_aggregate{type, stat=count|mean|min|max}` aggregated per second across the live ECS world. Cardinality bounded to `\|SensorType\| × 4` series independent of physical sensor count.
  - Dashboards: [dashboards/runtime.json](dashboards/runtime.json) + [dashboards/sensors.json](dashboards/sensors.json).
  - Verified: `--profile industrial --devices 2 --count 200` yields 10 entities and all 5 type aggregates with realistic values (T=20.5°C, RH=51%, P=1018 hPa, V=230.2 V, I=12 A).
- **M6 — Benchmark harness.** Sweep `entity_count ∈ {10k, 50k, 100k, 200k}` × `loss_rate ∈ {0%, 1%, 5%}` with 2k warmup + 5k measurement ticks. Loss via `tc netem`. Writes `data/loopback/final_table.csv`. *Verify:* one full sweep on M4 Max produces a CSV the Quarto figures consume.
- **M7 — CM5 cross-compile & deploy.** Exercise [Makefile:30](Makefile#L30) (`build-cm5`, `deploy-cm5`); set real `CM5_HOST`. *Verify:* binary runs on CM5 with a feed from M4 Max over 1 Gbps Ethernet.
- **M8 — Two-machine run + paper render.** Sweep with simulator on M4 Max → substrate on CM5; populate `data/two_machine/final_table.csv`; `make render` produces a PDF. **Update §Evaluation prose to reflect actual numbers.** Current paper figures (241 Hz, 64 µs / 15.8 ms P99, 2.6 µs jitter, 1.02 MB/1k, R²=0.9999) are **aspirational placeholders** — they may move and the conclusions may shift; that's expected.

## Conventions

- **Rust:** edition 2024; workspace at root with `simulator` + `substrate`; `opt-level=1` dev, `opt-level=3` for deps.
- **Pinned crates:** Bevy 0.18, Quinn 0.11, rustls 0.23, Tokio 1 (full), figment 0.10 (toml + env), uuid 1.23 (v4), serde 1.
- **Config:** `figment` chain — defaults in [substrate/src/config.rs:25](substrate/src/config.rs#L25) → `config.toml` → env `APP_*` (double-underscore for nesting, e.g. `APP_NETWORK__SERVER_PORT=9000`).
- **Bevy:** headless — `MinimalPlugins` only; do not pull rendering plugins.
- **Tokio↔Bevy:** keep the dedicated-thread + mpsc pattern in [substrate/src/transport/ecs.rs:49](substrate/src/transport/ecs.rs#L49); do not block the ECS schedule on async work.
- **Paper:** Quarto + LNCS template ([paper/_extensions/template.tex](paper/_extensions/template.tex), [paper/_quarto.yml](paper/_quarto.yml)). **Never commit `llncs.cls` or `splncs04.bst`** — CTAN licensing; download per [README.md:25-34](README.md#L25-L34).
- **Data:** raw CSVs under `data/` are committed; `*_processed.csv` is gitignored. Paper figures consume `data/loopback/final_table.csv` and `data/two_machine/final_table.csv`.
- **Build artifacts:** `target/`, `paper/_output/`, `paper/figures/`, `paper/.quarto/`, `paper/index.tex` all gitignored.
- **Errors:** `anyhow` (with `.context()`) for internal startup paths where the error type is uninteresting; `thiserror` for boundary types we want to match against (e.g. `WireError` in the codec).
- **Warnings:** let real warnings show. No `#[allow(dead_code)]`, `_var` blanket suppression, or `PhantomData` shims to silence the compiler — warnings are honest TODO markers and disappear when the consuming code lands. See [feedback memory](../../.claude/projects/-Users-vplantevin-Projects-Research-quic-ecs-dt/memory/feedback_no_warning_hacks.md).

## Known deferrals

- **Channel ownership is per-host, not per-connection.** All connections share the same inbound mpsc channels and the same outbound T3 channel. Fairness under N-device load relies on tokio scheduling. Acceptable for the "one ECS world per host" model the paper describes; revisit if many-device benchmarks show starvation.
- **No graceful shutdown.** The `quic-runtime` thread is parked on `pending()`; spawned tasks (accept loop, per-conn demux, outbound drain, per-command T3 spawns) are orphaned at process exit. Fine for research runs.
- **Bind failure is fatal.** `OnEnter(Starting)` panics if `bind_endpoint` fails. A `ServerState::Failed` variant joins when we wire proper error surfacing.
- **T3 outbound concurrency is unbounded.** `drain_outbound_t3` spawns one task per command (so a stuck `read_exact` can't stall the pipeline). Under sustained T1 ingest beyond ~10k msg/s the per-command tasks queue behind the tokio scheduler and T3 P99 latency climbs into the hundreds of ms while throughput holds. If we need true latency isolation under load, add a `tokio::Semaphore` cap or a dedicated runtime/thread for T3.
- **Schedule rate-gating is approximate.** `ScheduleRunnerPlugin::run_loop(period)` honours `period` as a minimum; observed `tick_hz` runs ~85% of target on macOS dev (target 60 → ~50). Should be tighter on the CM5; revisit if M6 sweeps depend on a steady tick.

## Run / verify

```bash
make certs              # generate certs/server.{crt,key} (ECDSA P-256, SAN: localhost/cm5.local/127.0.0.1/::1)
make build              # cargo build --release (native, depends on certs)
make build-cm5          # aarch64 cross-build for the CM5 (depends on certs)
make deploy-cm5         # scp to $CM5_HOST (set in env or override Makefile var)
make render             # build the paper PDF
make preview            # live-reload paper preview at :4848
make clean              # cargo clean + drop generated paper outputs
```

`certs/` is gitignored; `make build` regenerates the dev cert if missing. From the repo root: `cargo run -p substrate` boots, prints the loaded `AppConfig`, and idles. `config.toml` and cert paths are resolved relative to the cwd — always launch from the repo root.

**Tests.** `cargo test --workspace` runs the codec unit tests in `substrate` plus the end-to-end integration tests in [simulator/tests/](simulator/tests/). Each integration test calls `bind_endpoint` + `accept_loop` in-process on `127.0.0.1:0` (OS-assigned port), connects a `SimulatorClient` against it, and asserts what arrives on the test-owned T1 receiver. Add a new `simulator/tests/end_to_end_*.rs` for each new wire path (T2 uni, T3 bi) as the substrate-side demux lands.

**Metrics scrape.** With `metrics_enabled = true` (default), the substrate exposes a Prometheus-format endpoint:

```bash
curl http://127.0.0.1:9100/metrics
```

A docker-compose stack under [monitoring/](monitoring/) brings up VictoriaMetrics + Grafana auto-provisioned: `make monitoring-up` then Grafana at <http://localhost:3000> (admin / admin), both dashboards under the `quic_ecs_dt` folder. The compose mounts [dashboards/](dashboards/) directly so any edit to the JSON files re-imports within 10 s.

Two Grafana dashboards under [dashboards/](dashboards/):

- [`runtime.json`](dashboards/runtime.json) — tick rate, RSS, per-tier received/dropped/latency, channel depth (paper §Evaluation surface).
- [`sensors.json`](dashboards/sensors.json) — thermometer + gauges + stat panels per `SensorType`, driven by `sensor_aggregate{type, stat}` (operator-facing surface).

Both use the `${datasource}` template variable so you can point them at any Prometheus-compatible source.

**Manual two-process run.** From the repo root, in two shells:

```bash
# shell 1 — server (use RUST_LOG=substrate=debug to see the per-conn summary)
cargo run -p substrate

# shell 2 — client; --help shows all flags
cargo run -p simulator -- --rate-hz 100 --count 0 --devices 4
```

Simulator flags (see `cargo run -p simulator -- --help`): `--addr`, `--server-name`, `--cert`, `--rate-hz` (T1 datagram rate; `0` disables T1), `--t2-rate-hz` / `--t3-rate-hz` (per-tier event rate; `0` disables), `--t3-timeout-ms` (T3 ack wait, default `2000`), `--count` (T1 count; `0` = until Ctrl-C), `--devices`, `--sensor-id`, `--sensor-type` (one of `generic|temperature|humidity|pressure|voltage|current`), `--profile` (`single` or `industrial` — 5 sensors per device on ids 0..4 covering all types). The client logs a one-second `progress` line with `t1_sent`/`t2_sent`/`t3_sent`/`t3_timeouts`/per-tier observed Hz, and a final `simulator done` line with elapsed time on exit.

## Key references

- Prior self-citations: `plantevin2026ecs`, `plantevin2026quic` (both IEEE SWC 2026, "to appear").
- QUIC: RFC 9000 (core), RFC 9221 (unreliable datagrams).
- DT foundations: Tao et al. 2019; Grieves & Vickers 2017; Minerva et al. 2020.
- ECS: Nystrom 2014, *Game Programming Patterns*.
- Mixed-reliability transport: Peeck et al. (W2RP for DDS).
- DT sync metrics: Çakır et al. 2023 (Twin Alignment Ratio); Bellavista et al. 2023 (ODTE).
- Industrial QUIC/IIoT: Fernández et al. 2021; Boeding et al. 2025.
- Full bibliography: [paper/references.bib](paper/references.bib).