First test kinda working

2026-05-12 11:21:40 -04:00
parent cac6c9ac02
commit d3f09ee062
36 changed files with 3903 additions and 102 deletions
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -13,13 +13,15 @@ Source repo for **"QUIC + ECS as Complementary Transport and Runtime Substrates

 Three-tier QUIC ↔ ECS bridge, headless Bevy runtime:

-| Tier | QUIC primitive | Use case | Channel cap |
-|------|----------------|----------|-------------|
-| T1 | Unreliable datagrams (RFC 9221) | High-freq ephemeral telemetry; drops OK | 1024, lossy backpressure |
-| T2 | Unidirectional streams | Ordered threshold events; reliable | 512, fully drained |
-| T3 | Bidirectional streams | Actuator commands w/ ACK | 256, fully drained |
+| Tier | QUIC primitive | Use case | Channel cap | Tx newtype |
+|------|----------------|----------|-------------|------------|
+| T1 | Unreliable datagrams (RFC 9221) | High-freq ephemeral telemetry; drops OK | 1024 | `T1Sender::send_lossy` (try_send, drop on full) |
+| T2 | Unidirectional streams | Ordered threshold events; reliable | 512 | `T2Sender::send` (await, backpressure) |
+| T3 | Bidirectional streams | Actuator commands w/ ACK; per-command oneshot reply | 256 | `T3Sender::send` of `T3Inbound { command, reply }` |

-QUIC server runs on a dedicated OS thread with a Tokio multi-thread runtime; pushes decoded `QuicMessage` (UUID + stream_id + f64 + ts + seq) into `tokio::sync::mpsc` per tier; Bevy `IngestSystem` drains in `PreUpdate`. Pattern is in [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs).
+QUIC server runs on a dedicated OS thread with a Tokio multi-thread runtime; pushes decoded `QuicMessage` (UUID + sensor_id + f64 + ts + seq, 38 B fixed LE) into `tokio::sync::mpsc` per tier via the `T1Sender / T2Sender / T3Sender` newtypes (in [substrate/src/transport/mod.rs](substrate/src/transport/mod.rs)) so misuse is a type error. Bevy `ingest_system` drains in `PreUpdate`, gated by `run_if(in_state(ServerState::Started))`. Pattern is in [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs).
+
+**T3 ack protocol.** A device opens a bi-stream and writes one `QuicMessage` (the command). The demux task reads it, builds a `T3Inbound { command, reply: oneshot::Sender<QuicMessage> }`, and sends it on the T3 mpsc. The ECS handler writes the ack into `reply`; the demux task awaits `reply_rx` and writes the resulting `QuicMessage` back on the bi-stream. Dropping the oneshot signals "no handler" and propagates as a stream close — used by the placeholder ingest until M4 installs real handlers.

 **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.

@@ -49,13 +51,18 @@ quic_ecs_dt/
 | `AppConfig` figment loader (defaults → TOML → env) | Done — [substrate/src/config.rs:42](substrate/src/config.rs#L42) |
 | 3-tier MPSC bridge scaffolding (Tokio thread + Bevy plugin) | Done — [substrate/src/transport/ecs.rs](substrate/src/transport/ecs.rs) |
 | `QuicMessage` struct (no codec yet) | Defined — [substrate/src/transport/mod.rs:4](substrate/src/transport/mod.rs#L4) |
-| Quinn server (accept loop, demux, decode) | **Empty stub** — [substrate/src/transport/server.rs:4](substrate/src/transport/server.rs#L4) |
-| TLS / self-signed cert | Done (M1) — `certs/server.{crt,key}` via `make certs`, gitignored |
-| Wire codec for `QuicMessage` (38 B fixed LE) | Done (M1) — [substrate/src/transport/mod.rs:35](substrate/src/transport/mod.rs#L35); 4 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`, `T3Sender::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 |
+| 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 38 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 |
+| T3 demux (bi streams ↔ ECS) | Done — `accept_bi_streams` + `read_one_bi_stream` in [substrate/src/transport/server.rs](substrate/src/transport/server.rs); reads 38 B command, ships `T3Inbound { command, reply: oneshot::Sender }` to the ECS, awaits the reply, writes 38 B ack and finishes. If the ECS drops the oneshot (no handler installed yet — the M4 placeholder) `send.reset(0)` gives the client a clean signal instead of a half-open stream. `handle_incoming` joins all three readers on close |
+| 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`) + 5 systems (Ingest/Sim/Export/FaultInjection/Diagnostics) | Missing — placeholder at [substrate/src/transport/ecs.rs:26](substrate/src/transport/ecs.rs#L26) |
-| VictoriaMetrics + Grafana export | Missing |
-| Simulator (Quinn client + sensor generators) | `Hello, world!` — [simulator/src/main.rs](simulator/src/main.rs) |
+| ECS components (`RawSensorData`, `SmoothedValue`) + 5 systems (Ingest/Sim/Export/FaultInjection/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. `FaultInjection` is still a stub awaiting M6. `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, `request(&QuicMessage) -> QuicMessage` for T3. CLI driver in [simulator/src/main.rs](simulator/src/main.rs) with clap flags (`--addr`, `--rate-hz`, `--t2-rate-hz`, `--t3-rate-hz`, `--t3-timeout-ms`, `--count`, `--devices`, `--sensor-id`, `--sensor-type`, `--profile`, `--cert`, `--server-name`); parallel T1+T2+T3 emitters, per-(device,sensor) sequence counters, type-appropriate waveform generators (sin/cos curves centred on realistic sensor ranges), 1-Hz combined progress logs, Ctrl-C drain. `--profile industrial` fans out to 5 sensors per device (Temperature/Humidity/Pressure/Voltage/Current). Bevy-driven sensor generator still pending |
+| End-to-end test harness | Six integration 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_t3.rs](simulator/tests/end_to_end_t3.rs): T1 single-datagram round-trip + 32-msg burst order; T2 single-stream order-preservation + 4-stream concurrent per-device ordering; T3 round-trip with fake-ECS handler + no-handler stream-reset. Each test calls `bind_endpoint` + `accept_loop` in-process with channels owned by the test |
 | `config.toml` at repo root | Done (M1) — [config.toml](config.toml); loaded by [substrate/src/main.rs:9](substrate/src/main.rs#L9) |
 | Benchmark harness (sweep + CSV writer) | Missing |
 | CM5 cross-compile / deploy | Wired in [Makefile:30](Makefile#L30); not exercised |
@@ -67,10 +74,14 @@ quic_ecs_dt/
 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.** Fill [substrate/src/transport/server.rs](substrate/src/transport/server.rs): `Endpoint::server`, accept loop, demux T1=datagrams / T2=uni / T3=bi, push into matching `mpsc::Sender`. Use `rcgen` for a dev cert at boot. *Verify:* a Quinn smoke client connects, server logs handshake.
- **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.
- **M4 — ECS world.** Define `RawSensorData` and the 5 systems the paper names (`FaultInjectionSystem`, `IngestSystem`, `SimulationSystem`, `ExportSystem`, `DiagnosticsSystem`). Wire `IngestSystem` into the existing `PreUpdate` slot. *Verify:* with 10k simulated devices, entity count stabilizes; `DiagnosticsSystem` logs steady tick rate.
- **M5 — Observability (VictoriaMetrics + Grafana).** Substrate exposes Prometheus-format `/metrics` (use `metrics` + `metrics-exporter-prometheus`): tick rate, RSS, per-tier P50/P99/P999, channel depth, drop count. Commit a Grafana dashboard JSON. *Verify:* `curl :PORT/metrics` returns labeled samples; dashboard renders against VM.
+- **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. `FaultInjection` still a stub (M6). `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` or in-app injection. 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.
@@ -85,6 +96,17 @@ Each milestone has one verification gate. Update Status here as we go.
 - **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 three mpsc channels. 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) are orphaned at process exit. Fine for research runs; we'll need an `OnExit(Started)` (or a `Stopping` state) when M5 observability needs clean drain or M8 wants finalised CSV writes.
+- **Bind failure is fatal.** `OnEnter(Starting)` panics if `bind_endpoint` fails. A `ServerState::Failed` variant joins when we wire proper error surfacing.
+- **T3 ack semantics are minimal.** The current handler echoes the device's most recent `raw_value` with a server timestamp — adequate for "read sensor" commands, not for actuator-write semantics. A future iteration may introduce an `ActuatorState` component and a setpoint-apply path; for now T3 is best framed as "reliable read/query RPC" in the paper.
+- **`FaultInjectionSystem` is still empty.** Runs on schedule but does nothing. M6 fills it with rate-controlled in-app drop so loss sweeps don't depend on external `tc netem`.
+- **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

@@ -100,6 +122,35 @@ 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").
--- a/26
+++ b/26
@@ -1,14 +1,19 @@
 # ============================================================
 #  quic_ecs_dt — top-level Makefile
 #  Targets:
+#    make demo               — one-shot: certs → build → VM+Grafana →
+#                              substrate → simulator (Ctrl-C cleans up)
 #    make render             — build the paper PDF
 #    make preview            — live-reload preview in browser
 #    make build              — cargo build --release (native)
 #    make build-cm5          — cargo build --release (aarch64 cross)
+#    make monitoring-up      — start VictoriaMetrics + Grafana (docker)
+#    make monitoring-down    — stop them
+#    make monitoring-logs    — tail the monitoring stack
 #    make clean              — remove generated outputs
 # ============================================================

-.PHONY: render preview build build-cm5 clean certs
+.PHONY: render preview build build-cm5 clean certs monitoring-up monitoring-down monitoring-logs demo

 VENV        := $(HOME)/.venv/quic_ecs
 PYTHON      := $(VENV)/bin/python
@@ -53,6 +58,25 @@ deploy-cm5: build-cm5
 	scp target/aarch64-unknown-linux-gnu/release/quic_ecs_dt \
 	    $(CM5_USER)@$(CM5_HOST):$(CM5_BIN_DIR)/

+# One-shot demo runner — see scripts/demo.sh
+demo:
+	@./scripts/demo.sh
+
+# Monitoring (VictoriaMetrics + Grafana, auto-provisioned)
+monitoring-up:
+	docker compose -f monitoring/docker-compose.yml up -d
+	@echo ""
+	@echo "Grafana: http://localhost:3000   (admin / admin, or anonymous Admin)"
+	@echo "  • runtime dashboard:  quic_ecs_dt → quic_ecs_dt — substrate runtime"
+	@echo "  • sensors dashboard:  quic_ecs_dt → quic_ecs_dt — sensors"
+	@echo "VictoriaMetrics: http://localhost:8428"
+
+monitoring-down:
+	docker compose -f monitoring/docker-compose.yml down
+
+monitoring-logs:
+	docker compose -f monitoring/docker-compose.yml logs -f
+
 # Clean
 clean:
 	cargo clean
--- a/config.toml
+++ b/config.toml
@@ -16,3 +16,7 @@ server_key       = "certs/server.key"
 [simulation]
 tick_rate_hz = 60
 max_entities = 10000
+
+[observability]
+metrics_enabled = true
+metrics_listen  = "0.0.0.0:9100"
--- a/dashboards/runtime.json
+++ b/dashboards/runtime.json
@@ -0,0 +1,148 @@
+{
+  "title": "quic_ecs_dt — substrate runtime",
+  "uid": "quic-ecs-dt-runtime",
+  "schemaVersion": 39,
+  "version": 1,
+  "timezone": "",
+  "refresh": "5s",
+  "time": { "from": "now-15m", "to": "now" },
+  "tags": ["quic_ecs_dt", "ucami2026", "substrate"],
+  "templating": {
+    "list": [
+      {
+        "name": "datasource",
+        "label": "Data source",
+        "type": "datasource",
+        "query": "prometheus",
+        "current": { "selected": false, "text": "Prometheus", "value": "Prometheus" },
+        "hide": 0
+      }
+    ]
+  },
+  "panels": [
+    {
+      "id": 1,
+      "title": "Tick rate (Hz)",
+      "type": "stat",
+      "gridPos": { "h": 4, "w": 6, "x": 0, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "hertz", "decimals": 1 } },
+      "targets": [
+        { "expr": "substrate_tick_hz", "refId": "A", "legendFormat": "tick_hz" }
+      ]
+    },
+    {
+      "id": 2,
+      "title": "Entities",
+      "type": "stat",
+      "gridPos": { "h": 4, "w": 6, "x": 6, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short" } },
+      "targets": [
+        { "expr": "substrate_entities", "refId": "A", "legendFormat": "entities" }
+      ]
+    },
+    {
+      "id": 3,
+      "title": "RSS",
+      "type": "stat",
+      "gridPos": { "h": 4, "w": 6, "x": 12, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "bytes", "decimals": 1 } },
+      "targets": [
+        { "expr": "substrate_rss_bytes", "refId": "A", "legendFormat": "rss" }
+      ]
+    },
+    {
+      "id": 4,
+      "title": "T3 — no handler events (cumulative)",
+      "type": "stat",
+      "gridPos": { "h": 4, "w": 6, "x": 18, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short" } },
+      "targets": [
+        { "expr": "substrate_t3_no_handler_total", "refId": "A", "legendFormat": "no_handler" }
+      ]
+    },
+    {
+      "id": 5,
+      "title": "Per-tier receive rate",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 0, "y": 4 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "cps" } },
+      "targets": [
+        {
+          "expr": "rate(substrate_received_total[1m])",
+          "refId": "A",
+          "legendFormat": "received {{tier}}"
+        },
+        {
+          "expr": "rate(substrate_dropped_total[1m])",
+          "refId": "B",
+          "legendFormat": "dropped {{tier}}"
+        }
+      ]
+    },
+    {
+      "id": 6,
+      "title": "Per-tier latency (µs)",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 12, "y": 4 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "µs", "decimals": 0 } },
+      "targets": [
+        {
+          "expr": "substrate_latency_us{quantile=\"0.5\"}",
+          "refId": "A",
+          "legendFormat": "p50 {{tier}}"
+        },
+        {
+          "expr": "substrate_latency_us{quantile=\"0.99\"}",
+          "refId": "B",
+          "legendFormat": "p99 {{tier}}"
+        },
+        {
+          "expr": "substrate_latency_us{quantile=\"0.999\"}",
+          "refId": "C",
+          "legendFormat": "p999 {{tier}}"
+        }
+      ]
+    },
+    {
+      "id": 7,
+      "title": "Channel depth (vs. capacity)",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 0, "y": 12 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short" } },
+      "targets": [
+        {
+          "expr": "substrate_channel_depth",
+          "refId": "A",
+          "legendFormat": "depth {{tier}}"
+        },
+        {
+          "expr": "substrate_channel_capacity",
+          "refId": "B",
+          "legendFormat": "capacity {{tier}}"
+        }
+      ]
+    },
+    {
+      "id": 8,
+      "title": "Decode errors (rate)",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 12, "y": 12 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "cps" } },
+      "targets": [
+        {
+          "expr": "rate(substrate_decode_errors_total[1m])",
+          "refId": "A",
+          "legendFormat": "decode_errors {{tier}}"
+        }
+      ]
+    }
+  ]
+}
--- a/dashboards/sensors.json
+++ b/dashboards/sensors.json
@@ -0,0 +1,272 @@
+{
+  "title": "quic_ecs_dt — sensors",
+  "uid": "quic-ecs-dt-sensors",
+  "schemaVersion": 39,
+  "version": 1,
+  "timezone": "",
+  "refresh": "1s",
+  "time": { "from": "now-5m", "to": "now" },
+  "tags": ["quic_ecs_dt", "ucami2026", "sensors"],
+  "templating": {
+    "list": [
+      {
+        "name": "datasource",
+        "label": "Data source",
+        "type": "datasource",
+        "query": "prometheus",
+        "current": { "selected": false, "text": "Prometheus", "value": "Prometheus" },
+        "hide": 0
+      }
+    ]
+  },
+  "panels": [
+    {
+      "id": 1,
+      "title": "Temperature — mean (thermometer)",
+      "type": "gauge",
+      "gridPos": { "h": 8, "w": 6, "x": 0, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "options": {
+        "showThresholdLabels": false,
+        "showThresholdMarkers": true,
+        "orientation": "vertical"
+      },
+      "fieldConfig": {
+        "defaults": {
+          "unit": "celsius",
+          "decimals": 1,
+          "min": -20,
+          "max": 80,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "blue", "value": null },
+              { "color": "green", "value": 10 },
+              { "color": "yellow", "value": 30 },
+              { "color": "orange", "value": 50 },
+              { "color": "red", "value": 70 }
+            ]
+          }
+        }
+      },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"temperature\", stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "T mean"
+        }
+      ]
+    },
+    {
+      "id": 2,
+      "title": "Humidity — mean",
+      "type": "gauge",
+      "gridPos": { "h": 8, "w": 6, "x": 6, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "options": { "showThresholdMarkers": true, "orientation": "vertical" },
+      "fieldConfig": {
+        "defaults": {
+          "unit": "percent",
+          "decimals": 1,
+          "min": 0,
+          "max": 100,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "orange", "value": null },
+              { "color": "green", "value": 30 },
+              { "color": "blue", "value": 70 }
+            ]
+          }
+        }
+      },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"humidity\", stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "RH mean"
+        }
+      ]
+    },
+    {
+      "id": 3,
+      "title": "Pressure — mean",
+      "type": "stat",
+      "gridPos": { "h": 8, "w": 6, "x": 12, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "options": { "graphMode": "area", "colorMode": "value" },
+      "fieldConfig": {
+        "defaults": {
+          "unit": "pressurehpa",
+          "decimals": 1,
+          "min": 980,
+          "max": 1040,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "blue", "value": null },
+              { "color": "green", "value": 1000 },
+              { "color": "yellow", "value": 1025 }
+            ]
+          }
+        }
+      },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"pressure\", stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "P mean"
+        }
+      ]
+    },
+    {
+      "id": 4,
+      "title": "Voltage — mean",
+      "type": "stat",
+      "gridPos": { "h": 8, "w": 6, "x": 18, "y": 0 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "options": { "graphMode": "area", "colorMode": "value" },
+      "fieldConfig": {
+        "defaults": {
+          "unit": "volt",
+          "decimals": 2,
+          "min": 220,
+          "max": 240,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "yellow", "value": null },
+              { "color": "green", "value": 225 },
+              { "color": "yellow", "value": 235 }
+            ]
+          }
+        }
+      },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"voltage\", stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "V mean"
+        }
+      ]
+    },
+    {
+      "id": 5,
+      "title": "Current — mean",
+      "type": "stat",
+      "gridPos": { "h": 8, "w": 6, "x": 0, "y": 8 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "options": { "graphMode": "area", "colorMode": "value" },
+      "fieldConfig": {
+        "defaults": {
+          "unit": "amp",
+          "decimals": 2,
+          "min": 0,
+          "max": 30,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "green", "value": null },
+              { "color": "yellow", "value": 20 },
+              { "color": "red", "value": 25 }
+            ]
+          }
+        }
+      },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"current\", stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "I mean"
+        }
+      ]
+    },
+    {
+      "id": 6,
+      "title": "Sensor count by type",
+      "type": "stat",
+      "gridPos": { "h": 8, "w": 6, "x": 6, "y": 8 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short" } },
+      "options": { "colorMode": "value", "graphMode": "none" },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{stat=\"count\"}",
+          "refId": "A",
+          "legendFormat": "{{type}}"
+        }
+      ]
+    },
+    {
+      "id": 7,
+      "title": "Temperature — min / mean / max over time",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 12, "y": 8 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "celsius", "decimals": 1 } },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{type=\"temperature\", stat=\"min\"}",
+          "refId": "A",
+          "legendFormat": "min"
+        },
+        {
+          "expr": "sensor_aggregate{type=\"temperature\", stat=\"mean\"}",
+          "refId": "B",
+          "legendFormat": "mean"
+        },
+        {
+          "expr": "sensor_aggregate{type=\"temperature\", stat=\"max\"}",
+          "refId": "C",
+          "legendFormat": "max"
+        }
+      ]
+    },
+    {
+      "id": 8,
+      "title": "All sensor types — mean over time",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 24, "x": 0, "y": 16 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short", "decimals": 2 } },
+      "targets": [
+        {
+          "expr": "sensor_aggregate{stat=\"mean\"}",
+          "refId": "A",
+          "legendFormat": "{{type}}"
+        }
+      ]
+    },
+    {
+      "id": 9,
+      "title": "Threshold crossings (cumulative) — per type / direction",
+      "description": "Each time a sensor's smoothed mean crosses its per-type threshold, simulation_system increments the counter. up = rising through threshold; down = falling through. The counter being non-zero is the load-bearing evidence that the ECS runs the digital-twin transform — not just write-through ingest.",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 0, "y": 24 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "short" } },
+      "targets": [
+        {
+          "expr": "substrate_threshold_crossings_total",
+          "refId": "A",
+          "legendFormat": "{{type}} {{direction}}"
+        }
+      ]
+    },
+    {
+      "id": 10,
+      "title": "Threshold crossings — rate (events/min)",
+      "type": "timeseries",
+      "gridPos": { "h": 8, "w": 12, "x": 12, "y": 24 },
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "fieldConfig": { "defaults": { "unit": "cpm" } },
+      "targets": [
+        {
+          "expr": "60 * rate(substrate_threshold_crossings_total[1m])",
+          "refId": "A",
+          "legendFormat": "{{type}} {{direction}}"
+        }
+      ]
+    }
+  ]
+}
--- a/data/local/cross_tier.csv
+++ b/data/local/cross_tier.csv
@@ -0,0 +1,2 @@
+rate_hz,t3_rate_hz,devices,tick_rate_hz,window_s,t1_received,t1_dropped,t1_p50_us,t1_p99_us,t1_p999_us,t3_received,t3_no_handler,t3_p50_us,t3_p99_us,t3_p999_us,tick_hz,rss_mb,channel_depth_max
+100,100,100,0,25,2646,0,118.99720565324648,202.0065277946852,245.99224556720532,2646,0,120.98904580793433,199.99652925270829,238.0069829199846,15833.3,28.0,0
--- a/data/local/scaling.csv
+++ b/data/local/scaling.csv
@@ -0,0 +1,10 @@
+rate_hz,devices,tick_rate_hz,window_s,t1_received,t1_dropped,t1_p50_us,t1_p99_us,t1_p999_us,tick_hz,rss_mb,channel_depth_max
+100,100,0,25,2715,0,10287.656173771804,20683.6751522136,20899.90783549675,52.1,28.2,1
+500,100,0,25,13595,0,9945.744255905174,20441.042134756957,20879.018374063122,51.0,29.8,1
+1000,100,0,25,27324,0,9858.605678238058,20371.66060670275,20862.321838812768,51.6,30.3,2
+5000,100,0,25,136305,0,9700.182954474827,20144.770960915914,20803.98904149668,52.2,31.4,10
+10000,100,0,25,273443,0,9680.801975940145,20164.925807687836,20874.842987926906,51.9,31.9,10
+25000,100,0,25,685150,0,9466.362697231909,19813.128013911944,20766.575543347255,51.6,33.2,50
+50000,100,0,25,1371659,4515,9349.704574533685,19635.60989099387,20477.86914508828,51.5,33.3,100
+100000,100,0,25,2740689,1266351,13177.946960597013,20502.4573381096,28455.593524841766,53.0,35.2,200
+250000,100,0,25,6826035,5353528,16234.599694958577,20696.089081152582,22046.299162128806,53.2,35.6,747
--- a/monitoring/docker-compose.yml
+++ b/monitoring/docker-compose.yml
@@ -0,0 +1,56 @@
+# VictoriaMetrics + Grafana for `quic_ecs_dt` local demos.
+#
+# Run from the repo root (or via `make monitoring-up`). The substrate runs on
+# the host and exposes /metrics on :9100; VM scrapes it via
+# `host.docker.internal`, which works on Docker Desktop (mac/Windows) and on
+# recent Docker Engine on Linux thanks to the `extra_hosts` mapping below.
+#
+# Grafana auto-provisions:
+#   • a Prometheus-typed data source pointing at VM
+#   • both dashboards from ../dashboards (runtime + sensors)
+#
+# Endpoints:
+#   • Grafana            http://localhost:3000  (anonymous Admin)
+#   • VictoriaMetrics    http://localhost:8428
+#   • Substrate /metrics http://localhost:9100/metrics  (on the host)
+
+services:
+  victoria-metrics:
+    image: victoriametrics/victoria-metrics:v1.115.0
+    container_name: quic_ecs_dt_vm
+    ports:
+      - "8428:8428"
+    command:
+      - "-promscrape.config=/etc/vm/scrape.yml"
+      - "-retentionPeriod=1d"
+      - "-storageDataPath=/storage"
+    volumes:
+      - ./victoria-metrics/scrape.yml:/etc/vm/scrape.yml:ro
+      - vm-data:/storage
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
+    restart: unless-stopped
+
+  grafana:
+    image: grafana/grafana:11.4.0
+    container_name: quic_ecs_dt_grafana
+    ports:
+      - "3000:3000"
+    environment:
+      - GF_AUTH_ANONYMOUS_ENABLED=true
+      - GF_AUTH_ANONYMOUS_ORG_ROLE=Admin
+      - GF_AUTH_DISABLE_LOGIN_FORM=false
+      - GF_SECURITY_ADMIN_USER=admin
+      - GF_SECURITY_ADMIN_PASSWORD=admin
+      - GF_USERS_DEFAULT_THEME=dark
+    volumes:
+      - ./grafana/provisioning:/etc/grafana/provisioning:ro
+      - ../dashboards:/var/lib/grafana/dashboards:ro
+      - grafana-data:/var/lib/grafana
+    depends_on:
+      - victoria-metrics
+    restart: unless-stopped
+
+volumes:
+  vm-data:
+  grafana-data:
--- a/monitoring/grafana/provisioning/dashboards/provider.yml
+++ b/monitoring/grafana/provisioning/dashboards/provider.yml
@@ -0,0 +1,13 @@
+apiVersion: 1
+
+providers:
+  - name: quic_ecs_dt
+    orgId: 1
+    folder: "quic_ecs_dt"
+    type: file
+    disableDeletion: false
+    updateIntervalSeconds: 10
+    allowUiUpdates: true
+    options:
+      path: /var/lib/grafana/dashboards
+      foldersFromFilesStructure: false
--- a/monitoring/grafana/provisioning/datasources/datasource.yml
+++ b/monitoring/grafana/provisioning/datasources/datasource.yml
@@ -0,0 +1,13 @@
+apiVersion: 1
+
+datasources:
+  - name: Prometheus
+    type: prometheus
+    uid: prometheus
+    access: proxy
+    url: http://victoria-metrics:8428
+    isDefault: true
+    editable: true
+    jsonData:
+      timeInterval: "1s"
+      httpMethod: "POST"
--- a/monitoring/victoria-metrics/scrape.yml
+++ b/monitoring/victoria-metrics/scrape.yml
@@ -0,0 +1,14 @@
+# VictoriaMetrics scrape config — uses Prometheus-compatible syntax.
+# 1-second interval gives Grafana something to redraw every refresh tick.
+
+global:
+  scrape_interval: 1s
+  scrape_timeout: 800ms
+
+scrape_configs:
+  - job_name: substrate
+    static_configs:
+      - targets:
+          - "host.docker.internal:9100"
+        labels:
+          instance: "substrate-local"
--- a/scripts/bench-scaling.sh
+++ b/scripts/bench-scaling.sh
@@ -0,0 +1,248 @@
+#!/usr/bin/env bash
+# scripts/bench-scaling.sh — M6-lite: sweep T1 rate at fixed entity count,
+# record tick_hz / P99 latency / drops / RSS into a CSV the paper can plot.
+#
+# Two modes:
+#
+#  1. Scaling sweep (default).  Just T1 traffic. Tells you the substrate's
+#     throughput ceiling on this host and where the lossy-tier kicks in.
+#     Output: data/local/scaling.csv
+#
+#  2. Cross-tier isolation.  Set T3_RATE_HZ=<N> to run a constant T3 baseline
+#     in parallel with the T1 sweep. The CSV gains substrate-side T3 latency
+#     columns. If T3 P99 stays flat as T1 climbs orders of magnitude, the
+#     paper's composition thesis is supported.
+#     Output: data/local/cross_tier.csv
+#
+# Holds:
+#   - tick_rate_hz   $TICK_RATE_HZ   (default 1000; set 0 for busy-loop)
+#   - device count   $DEVICES        (default 100, single-sensor profile)
+#   - window         $WINDOW_S       (default 20s steady-state per rate)
+#   - T3 baseline    $T3_RATE_HZ     (default 0 = disabled)
+#   - T3 timeout     $T3_TIMEOUT_MS  (default 2000ms)
+#   - build profile  $BUILD          (release | debug; default release)
+#
+# Sweeps:
+#   T1 rate over the positional arguments, or these defaults:
+#     100 500 1000 5000 10000 25000 50000
+#
+# Examples:
+#   # Pure T1 scaling sweep.
+#   ./scripts/bench-scaling.sh
+#
+#   # Cross-tier isolation: hold T3 at 100 Hz, sweep T1.
+#   T3_RATE_HZ=100 ./scripts/bench-scaling.sh
+#
+#   # Custom sweep, longer windows.
+#   DEVICES=1000 WINDOW_S=30 ./scripts/bench-scaling.sh 1000 5000 20000
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+cd "$ROOT"
+
+# --- knobs ---
+DEVICES="${DEVICES:-100}"
+TICK_RATE_HZ="${TICK_RATE_HZ:-1000}"
+WARMUP_S="${WARMUP_S:-3}"
+WINDOW_S="${WINDOW_S:-20}"
+T3_RATE_HZ="${T3_RATE_HZ:-0}"
+T3_TIMEOUT_MS="${T3_TIMEOUT_MS:-2000}"
+BUILD="${BUILD:-release}"
+RATES=("${@}")
+if [[ ${#RATES[@]} -eq 0 ]]; then
+    RATES=(100 500 1000 5000 10000 25000 50000)
+fi
+
+# Pick default output path based on mode so the two CSVs don't clobber.
+CROSS_TIER=$(awk -v r="$T3_RATE_HZ" 'BEGIN { print (r+0 > 0) ? "1" : "0" }')
+if [[ "$CROSS_TIER" == "1" ]]; then
+    OUT_CSV="${OUT_CSV:-data/local/cross_tier.csv}"
+else
+    OUT_CSV="${OUT_CSV:-data/local/scaling.csv}"
+fi
+
+# --- pretty logging ---
+if [[ -t 1 ]]; then
+    BOLD=$'\033[1m'; DIM=$'\033[2m'; GREEN=$'\033[32m'; RED=$'\033[31m'; RESET=$'\033[0m'
+else BOLD=; DIM=; GREEN=; RED=; RESET=; fi
+step()  { printf '%s» %s%s\n' "$BOLD" "$1" "$RESET"; }
+ok()    { printf '%s  ✓ %s%s\n' "$GREEN" "$1" "$RESET"; }
+fail()  { printf '%s  ✗ %s%s\n' "$RED" "$1" "$RESET"; }
+
+# --- prereqs ---
+for cmd in cargo curl lsof awk; do
+    command -v "$cmd" >/dev/null || { fail "missing: $cmd"; exit 1; }
+done
+for port in 9000 9100; do
+    if lsof -nP -iUDP:$port -iTCP:$port -sTCP:LISTEN 2>/dev/null | grep -q LISTEN; then
+        fail "port $port in use — kill the running substrate first"
+        exit 1
+    fi
+done
+[[ -f certs/server.crt ]] || make certs >/dev/null
+
+# --- build ---
+step "Building ($BUILD)"
+if [[ "$BUILD" == "release" ]]; then
+    cargo build --release -p substrate -p simulator >/dev/null
+    SUBSTRATE="$ROOT/target/release/substrate"
+    SIMULATOR="$ROOT/target/release/simulator"
+else
+    cargo build -p substrate -p simulator >/dev/null
+    SUBSTRATE="$ROOT/target/debug/substrate"
+    SIMULATOR="$ROOT/target/debug/simulator"
+fi
+
+# --- start substrate with high tick rate ---
+LOG_DIR="/tmp/quic_ecs_dt_bench"
+mkdir -p "$LOG_DIR"
+SUB_LOG="$LOG_DIR/substrate.log"
+: > "$SUB_LOG"
+
+step "Starting substrate (tick_rate_hz=$TICK_RATE_HZ, log: $SUB_LOG)"
+APP_SIMULATION__TICK_RATE_HZ="$TICK_RATE_HZ" RUST_LOG=warn "$SUBSTRATE" >"$SUB_LOG" 2>&1 &
+SUBSTRATE_PID=$!
+
+# Wait for /metrics
+for i in $(seq 1 40); do
+    if curl -sf http://localhost:9100/metrics >/dev/null 2>&1; then
+        ok "substrate /metrics ready"; break
+    fi
+    sleep 0.25
+    if [[ $i -eq 40 ]]; then fail "substrate didn't start"; tail -20 "$SUB_LOG"; exit 1; fi
+done
+
+cleanup() {
+    [[ -n "${SIM_PID:-}" ]] && kill -TERM "$SIM_PID" 2>/dev/null || true
+    [[ -n "${SUBSTRATE_PID:-}" ]] && kill -TERM "$SUBSTRATE_PID" 2>/dev/null || true
+    wait 2>/dev/null || true
+}
+trap cleanup EXIT INT TERM
+
+# --- helpers to scrape a single value out of /metrics text ---
+snapshot_to() {
+    curl -s http://localhost:9100/metrics > "$1"
+}
+get_value() {
+    # $1: snapshot file, $2: full metric name (regex-anchored at line start)
+    awk -v pat="$2" '$0 ~ "^" pat " " { print $NF; exit }' "$1"
+}
+
+# --- sweep ---
+mkdir -p "$(dirname "$OUT_CSV")"
+echo "rate_hz,t3_rate_hz,devices,tick_rate_hz,window_s,t1_received,t1_dropped,t1_p50_us,t1_p99_us,t1_p999_us,t3_received,t3_no_handler,t3_p50_us,t3_p99_us,t3_p999_us,tick_hz,rss_mb,channel_depth_max" > "$OUT_CSV"
+
+if [[ "$CROSS_TIER" == "1" ]]; then
+    step "Sweeping T1 + holding T3 at ${T3_RATE_HZ} Hz (warmup ${WARMUP_S}s, window ${WINDOW_S}s, devices=$DEVICES)"
+else
+    step "Sweeping T1 rate (warmup ${WARMUP_S}s, window ${WINDOW_S}s, devices=$DEVICES)"
+fi
+printf '%s' "$BOLD"
+if [[ "$CROSS_TIER" == "1" ]]; then
+    printf '%-8s %-9s %-9s %-10s %-10s %-8s %-9s %-10s %-10s %-8s %-7s\n' \
+        "rate" "t1_recv" "t1_drop" "t1_p50" "t1_p99" "t3_recv" "t3_p50" "t3_p99" "t3_p999" "tick_hz" "rss_mb"
+else
+    printf '%-8s %-9s %-9s %-10s %-10s %-10s %-8s %-7s\n' \
+        "rate" "received" "dropped" "p50_us" "p99_us" "p999_us" "tick_hz" "rss_mb"
+fi
+printf '%s' "$RESET"
+
+# Snapshot file paths
+BEFORE="$LOG_DIR/before.txt"
+AFTER="$LOG_DIR/after.txt"
+
+# Peak-tracker for channel depth: tail /metrics at 4 Hz during the window
+peak_depth() {
+    local label="$1"  # "t1" or "t2" or "t3"
+    local max=0
+    local val
+    for _ in $(seq 1 $(( WINDOW_S * 4 ))); do
+        val=$(curl -s http://localhost:9100/metrics 2>/dev/null \
+            | awk -v pat="^substrate_channel_depth\\\\{tier=\"$label\"\\\\}" '$0 ~ pat {print $NF; exit}')
+        if [[ -n "$val" && "$val" != "0" ]]; then
+            # Compare numerically; bash can do integer compare via [[ ]]
+            int_val="${val%.*}"
+            if (( int_val > max )); then max=$int_val; fi
+        fi
+        sleep 0.25
+    done
+    echo "$max"
+}
+
+for rate in "${RATES[@]}"; do
+    # Launch simulator in background. In cross-tier mode it drives both T1
+    # and T3 on the same connection; otherwise just T1.
+    sim_args=(
+        --profile single
+        --sensor-type generic
+        --rate-hz "$rate"
+        --count 0
+        --devices "$DEVICES"
+    )
+    if [[ "$CROSS_TIER" == "1" ]]; then
+        sim_args+=(--t3-rate-hz "$T3_RATE_HZ" --t3-timeout-ms "$T3_TIMEOUT_MS")
+    fi
+    RUST_LOG=warn "$SIMULATOR" "${sim_args[@]}" >"$LOG_DIR/sim_${rate}.log" 2>&1 &
+    SIM_PID=$!
+
+    # Warmup, then snapshot counters at the start of the *measurement* window.
+    sleep "$WARMUP_S"
+    snapshot_to "$BEFORE"
+    rec_before=$(get_value "$BEFORE" 'substrate_received_total\{tier="t1"\}')
+    drop_before=$(get_value "$BEFORE" 'substrate_dropped_total\{tier="t1"\}')
+    t3_rec_before=$(get_value "$BEFORE" 'substrate_received_total\{tier="t3"\}')
+    t3_nh_before=$(get_value "$BEFORE" 'substrate_t3_no_handler_total')
+
+    depth_max=$(peak_depth t1)
+
+    snapshot_to "$AFTER"
+    kill -TERM "$SIM_PID" 2>/dev/null || true
+    wait "$SIM_PID" 2>/dev/null || true
+    SIM_PID=""
+
+    rec_after=$(get_value "$AFTER" 'substrate_received_total\{tier="t1"\}')
+    drop_after=$(get_value "$AFTER" 'substrate_dropped_total\{tier="t1"\}')
+    p50=$(get_value "$AFTER" 'substrate_latency_us\{tier="t1",quantile="0.5"\}')
+    p99=$(get_value "$AFTER" 'substrate_latency_us\{tier="t1",quantile="0.99"\}')
+    p999=$(get_value "$AFTER" 'substrate_latency_us\{tier="t1",quantile="0.999"\}')
+
+    t3_rec_after=$(get_value "$AFTER" 'substrate_received_total\{tier="t3"\}')
+    t3_nh_after=$(get_value "$AFTER" 'substrate_t3_no_handler_total')
+    t3_p50=$(get_value "$AFTER" 'substrate_latency_us\{tier="t3",quantile="0.5"\}')
+    t3_p99=$(get_value "$AFTER" 'substrate_latency_us\{tier="t3",quantile="0.99"\}')
+    t3_p999=$(get_value "$AFTER" 'substrate_latency_us\{tier="t3",quantile="0.999"\}')
+
+    tick_hz=$(get_value "$AFTER" 'substrate_tick_hz')
+    rss=$(get_value "$AFTER" 'substrate_rss_bytes')
+
+    # Compute deltas + format. Use awk for floating math.
+    received=$(awk -v a="$rec_after" -v b="$rec_before" 'BEGIN { printf "%d", a-b }')
+    dropped=$(awk -v a="$drop_after" -v b="$drop_before" 'BEGIN { printf "%d", a-b }')
+    t3_received=$(awk -v a="$t3_rec_after" -v b="$t3_rec_before" 'BEGIN { printf "%d", a-b }')
+    t3_no_handler=$(awk -v a="$t3_nh_after" -v b="$t3_nh_before" 'BEGIN { printf "%d", a-b }')
+    rss_mb=$(awk -v r="$rss" 'BEGIN { printf "%.1f", r/1048576 }')
+    tick_hz_fmt=$(awk -v t="$tick_hz" 'BEGIN { printf "%.1f", t }')
+
+    if [[ "$CROSS_TIER" == "1" ]]; then
+        printf '%-8s %-9s %-9s %-10.0f %-10.0f %-8s %-9.0f %-10.0f %-10.0f %-8s %-7s\n' \
+            "$rate" "$received" "$dropped" \
+            "${p50:-0}" "${p99:-0}" \
+            "$t3_received" "${t3_p50:-0}" "${t3_p99:-0}" "${t3_p999:-0}" \
+            "$tick_hz_fmt" "$rss_mb"
+    else
+        printf '%-8s %-9s %-9s %-10.0f %-10.0f %-10.0f %-8s %-7s\n' \
+            "$rate" "$received" "$dropped" "${p50:-0}" "${p99:-0}" "${p999:-0}" \
+            "$tick_hz_fmt" "$rss_mb"
+    fi
+
+    echo "$rate,$T3_RATE_HZ,$DEVICES,$TICK_RATE_HZ,$WINDOW_S,$received,$dropped,${p50:-0},${p99:-0},${p999:-0},$t3_received,$t3_no_handler,${t3_p50:-0},${t3_p99:-0},${t3_p999:-0},$tick_hz_fmt,$rss_mb,$depth_max" >> "$OUT_CSV"
+
+    # Tiny breather between rate points so the substrate's summary window
+    # doesn't carry over.
+    sleep 1
+done
+
+printf '\n%sCSV written to:%s %s\n' "$DIM" "$RESET" "$OUT_CSV"
+printf '%sSubstrate log:%s  %s\n' "$DIM" "$RESET" "$SUB_LOG"
--- a/scripts/demo.sh
+++ b/scripts/demo.sh
@@ -0,0 +1,222 @@
+#!/usr/bin/env bash
+# scripts/demo.sh — bring the whole stack up: certs → build → VM+Grafana →
+# substrate → simulator. Tails simulator progress in the foreground. Ctrl-C
+# cleans everything up.
+#
+# Overridable via env vars:
+#   PROFILE          single | industrial         (default: industrial)
+#   RATE_HZ          T1 datagram rate            (default: 500)
+#   T2_RATE_HZ       T2 uni stream rate          (default: 5)
+#   T3_RATE_HZ       T3 bi stream rate           (default: 2)
+#   DEVICES          number of devices           (default: 5)
+#   BUILD            release | debug             (default: release)
+#   KEEP_MONITORING  if 1, don't `docker compose down` on exit (default: 0)
+#
+# Example:
+#   ./scripts/demo.sh
+#   PROFILE=single RATE_HZ=100 DEVICES=20 ./scripts/demo.sh
+#   KEEP_MONITORING=1 ./scripts/demo.sh
+
+set -euo pipefail
+
+# --- locate repo root ---
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+cd "$ROOT"
+
+# --- defaults ---
+PROFILE="${PROFILE:-industrial}"
+RATE_HZ="${RATE_HZ:-500}"
+T2_RATE_HZ="${T2_RATE_HZ:-5}"
+T3_RATE_HZ="${T3_RATE_HZ:-2}"
+DEVICES="${DEVICES:-5}"
+BUILD="${BUILD:-release}"
+KEEP_MONITORING="${KEEP_MONITORING:-0}"
+LOG_DIR="${LOG_DIR:-/tmp/quic_ecs_dt}"
+
+# --- pretty logging ---
+if [[ -t 1 ]]; then
+    BOLD=$'\033[1m'; DIM=$'\033[2m'; GREEN=$'\033[32m'
+    YELLOW=$'\033[33m'; RED=$'\033[31m'; CYAN=$'\033[36m'; RESET=$'\033[0m'
+else
+    BOLD=; DIM=; GREEN=; YELLOW=; RED=; CYAN=; RESET=
+fi
+step()    { printf '%s» %s%s\n' "$BOLD" "$1" "$RESET"; }
+ok()      { printf '%s  ✓ %s%s\n' "$GREEN" "$1" "$RESET"; }
+warn()    { printf '%s  ! %s%s\n' "$YELLOW" "$1" "$RESET"; }
+fail()    { printf '%s  ✗ %s%s\n' "$RED" "$1" "$RESET"; }
+
+# --- prereq check ---
+step "Checking prerequisites"
+for cmd in cargo docker openssl curl lsof; do
+    if ! command -v "$cmd" >/dev/null 2>&1; then
+        fail "missing required command: $cmd"
+        exit 1
+    fi
+done
+if ! docker compose version >/dev/null 2>&1; then
+    fail "docker compose plugin not available (try 'docker compose version')"
+    exit 1
+fi
+ok "cargo, docker, openssl, curl, lsof present"
+
+# --- port collision check (substrate runs on 9000 udp + 9100 tcp) ---
+for port in 9000 9100; do
+    if lsof -nP -iUDP:$port -iTCP:$port -sTCP:LISTEN 2>/dev/null | grep -q LISTEN; then
+        fail "port $port appears to be in use — another substrate or process is running"
+        lsof -nP -iUDP:$port -iTCP:$port -sTCP:LISTEN 2>/dev/null | head -5
+        exit 1
+    fi
+done
+ok "ports 9000 (QUIC) and 9100 (/metrics) are free"
+
+# --- certs ---
+step "Ensuring dev TLS cert exists"
+if [[ ! -f certs/server.crt || ! -f certs/server.key ]]; then
+    make certs >/dev/null
+    ok "generated certs/server.{crt,key}"
+else
+    ok "certs/server.{crt,key} already present"
+fi
+
+# --- build ---
+step "Building substrate + simulator ($BUILD profile)"
+if [[ "$BUILD" == "release" ]]; then
+    cargo build --release -p substrate -p simulator
+    SUBSTRATE_BIN="$ROOT/target/release/substrate"
+    SIMULATOR_BIN="$ROOT/target/release/simulator"
+else
+    cargo build -p substrate -p simulator
+    SUBSTRATE_BIN="$ROOT/target/debug/substrate"
+    SIMULATOR_BIN="$ROOT/target/debug/simulator"
+fi
+ok "binaries: $SUBSTRATE_BIN, $SIMULATOR_BIN"
+
+# --- monitoring ---
+step "Bringing up VictoriaMetrics + Grafana (docker compose)"
+docker compose -f monitoring/docker-compose.yml up -d >/dev/null
+ok "containers started"
+
+printf '%s  ⏳ waiting for VictoriaMetrics on :8428' "$DIM"
+for i in $(seq 1 40); do
+    if curl -sf http://localhost:8428/health >/dev/null 2>&1; then
+        printf ' ready%s\n' "$RESET"; break
+    fi
+    printf '.'; sleep 0.5
+    if [[ $i -eq 40 ]]; then printf ' TIMEOUT%s\n' "$RESET"; exit 1; fi
+done
+
+printf '%s  ⏳ waiting for Grafana on :3000' "$DIM"
+for i in $(seq 1 40); do
+    if curl -sf http://localhost:3000/api/health >/dev/null 2>&1; then
+        printf ' ready%s\n' "$RESET"; break
+    fi
+    printf '.'; sleep 0.5
+    if [[ $i -eq 40 ]]; then printf ' TIMEOUT%s\n' "$RESET"; exit 1; fi
+done
+
+# --- substrate ---
+mkdir -p "$LOG_DIR"
+SUB_LOG="$LOG_DIR/substrate.log"
+SIM_LOG="$LOG_DIR/simulator.log"
+: >"$SUB_LOG"
+: >"$SIM_LOG"
+
+step "Starting substrate (log: $SUB_LOG)"
+RUST_LOG=info "$SUBSTRATE_BIN" >"$SUB_LOG" 2>&1 &
+SUBSTRATE_PID=$!
+
+printf '%s  ⏳ waiting for /metrics on :9100' "$DIM"
+for i in $(seq 1 40); do
+    if curl -sf http://localhost:9100/metrics >/dev/null 2>&1; then
+        printf ' ready%s\n' "$RESET"; break
+    fi
+    printf '.'; sleep 0.25
+    if [[ $i -eq 40 ]]; then
+        printf ' TIMEOUT%s\n' "$RESET"
+        warn "substrate failed to start; tail of $SUB_LOG:"
+        tail -30 "$SUB_LOG"
+        kill "$SUBSTRATE_PID" 2>/dev/null || true
+        exit 1
+    fi
+done
+
+# --- simulator ---
+TOTAL_SLOTS=$DEVICES
+if [[ "$PROFILE" == "industrial" ]]; then
+    TOTAL_SLOTS=$((DEVICES * 5))
+fi
+
+step "Starting simulator (log: $SIM_LOG)"
+RUST_LOG=info "$SIMULATOR_BIN" \
+    --profile "$PROFILE" \
+    --rate-hz "$RATE_HZ" \
+    --t2-rate-hz "$T2_RATE_HZ" \
+    --t3-rate-hz "$T3_RATE_HZ" \
+    --count 0 \
+    --devices "$DEVICES" \
+    >"$SIM_LOG" 2>&1 &
+SIMULATOR_PID=$!
+sleep 0.5
+if ! kill -0 "$SIMULATOR_PID" 2>/dev/null; then
+    fail "simulator exited immediately; tail of $SIM_LOG:"
+    tail -20 "$SIM_LOG"
+    kill "$SUBSTRATE_PID" 2>/dev/null || true
+    exit 1
+fi
+ok "simulator PID $SIMULATOR_PID"
+
+# --- cleanup trap ---
+cleanup() {
+    printf '\n%s» Cleaning up%s\n' "$BOLD" "$RESET"
+    if [[ -n "${SIMULATOR_PID:-}" ]]; then
+        kill -TERM "$SIMULATOR_PID" 2>/dev/null || true
+        wait "$SIMULATOR_PID" 2>/dev/null || true
+        ok "simulator stopped"
+    fi
+    if [[ -n "${SUBSTRATE_PID:-}" ]]; then
+        kill -TERM "$SUBSTRATE_PID" 2>/dev/null || true
+        wait "$SUBSTRATE_PID" 2>/dev/null || true
+        ok "substrate stopped"
+    fi
+    if [[ "$KEEP_MONITORING" == "1" ]]; then
+        warn "leaving monitoring stack up (KEEP_MONITORING=1) — 'make monitoring-down' to stop"
+    else
+        docker compose -f monitoring/docker-compose.yml down >/dev/null 2>&1 || true
+        ok "monitoring stack stopped"
+    fi
+    printf '%sLogs preserved at:%s %s\n' "$DIM" "$RESET" "$LOG_DIR"
+}
+trap cleanup EXIT INT TERM
+
+# --- summary ---
+cat <<EOF
+
+${BOLD}════════════════════════════════════════════════════════════${RESET}
+${BOLD} Demo is live${RESET}
+${BOLD}════════════════════════════════════════════════════════════${RESET}
+
+  ${CYAN}Grafana${RESET}            http://localhost:3000   (admin / admin)
+    sensors dash    http://localhost:3000/d/quic-ecs-dt-sensors
+    runtime dash    http://localhost:3000/d/quic-ecs-dt-runtime
+  ${CYAN}VictoriaMetrics${RESET}    http://localhost:8428
+  ${CYAN}substrate /metrics${RESET} http://localhost:9100/metrics
+
+  ${DIM}Logs${RESET}
+    substrate         $SUB_LOG
+    simulator         $SIM_LOG
+
+  ${DIM}Config${RESET}
+    profile           $PROFILE
+    rates             T1=$RATE_HZ Hz · T2=$T2_RATE_HZ Hz · T3=$T3_RATE_HZ Hz
+    devices           $DEVICES → $TOTAL_SLOTS sensor entities expected
+    build             $BUILD
+
+  ${DIM}Below: live tail of simulator progress (Ctrl-C to stop everything).${RESET}
+
+EOF
+
+# --- foreground tail of simulator progress ---
+# Filter for the per-second `progress` / `simulator done` lines so the user
+# sees the rates the simulator is observing without noise.
+tail -F "$SIM_LOG" | grep --line-buffered -E 'progress|simulator (done|launching|client connected)'
--- a/simulator/Cargo.toml
+++ b/simulator/Cargo.toml
@@ -8,3 +8,17 @@ thiserror = "2"
 anyhow = "1"
 bevy = "0.18"
 game_sockets = { git = "https://github.com/VALERE91/game_sockets.git"}
+substrate = { path = "../substrate" }
+quinn = "0.11"
+rustls = "0.23"
+rustls-pemfile = "2"
+rustls-pki-types = "1"
+tokio = { version = "1", features = ["full"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+uuid = { version = "1.23", features = ["v4"] }
+bytes = "1"
+clap = { version = "4", features = ["derive"] }
+
+[dev-dependencies]
+tokio = { version = "1", features = ["full", "test-util"] }
--- a/simulator/src/client.rs
+++ b/simulator/src/client.rs
@@ -0,0 +1,189 @@
+use std::net::SocketAddr;
+use std::path::Path;
+use std::sync::Arc;
+
+use anyhow::{anyhow, Context};
+use quinn::{ClientConfig, Connection, Endpoint};
+use rustls::client::danger::{HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier};
+use rustls::pki_types::{CertificateDer, ServerName, UnixTime};
+use rustls::{DigitallySignedStruct, SignatureScheme};
+use substrate::transport::QuicMessage;
+
+/// QUIC client for driving the substrate from tests, smoke runs, and
+/// (eventually) the full Bevy-driven sensor generator.
+///
+/// `connect` trusts the server's PEM cert by **exact byte match** — using a
+/// custom `ServerCertVerifier` that compares the leaf against the cert at
+/// `cert_path`. This sidesteps rustls' `CaUsedAsEndEntity` rejection of our
+/// self-signed cert (which acts as both trust anchor and leaf) without
+/// disabling signature verification or weakening the handshake.
+pub struct SimulatorClient {
+    pub endpoint: Endpoint,
+    pub conn: Connection,
+}
+
+impl SimulatorClient {
+    pub async fn connect(
+        server_addr: SocketAddr,
+        server_name: &str,
+        cert_path: impl AsRef<Path>,
+    ) -> anyhow::Result<Self> {
+        let cert_path = cert_path.as_ref();
+        let cert_pem = std::fs::read(cert_path)
+            .with_context(|| format!("read trust cert at {}", cert_path.display()))?;
+
+        let parsed: Vec<CertificateDer<'static>> = rustls_pemfile::certs(&mut cert_pem.as_slice())
+            .collect::<Result<_, _>>()
+            .with_context(|| format!("parse PEM certs at {}", cert_path.display()))?;
+        let expected = parsed
+            .into_iter()
+            .next()
+            .ok_or_else(|| anyhow!("no certificates found in {}", cert_path.display()))?;
+
+        // Reuse the process-wide rustls provider that `install_crypto_provider`
+        // (or substrate's main) already installed. Failing to find one here
+        // means nobody installed a default — caller error.
+        let provider = rustls::crypto::CryptoProvider::get_default()
+            .ok_or_else(|| anyhow!("no rustls default crypto provider installed"))?
+            .clone();
+
+        let verifier = Arc::new(TrustExactCert {
+            expected,
+            provider: provider.clone(),
+        });
+
+        let rustls_cfg = rustls::ClientConfig::builder_with_provider(provider)
+            .with_safe_default_protocol_versions()
+            .context("rustls client builder")?
+            .dangerous()
+            .with_custom_certificate_verifier(verifier)
+            .with_no_client_auth();
+
+        let quic_cfg = quinn::crypto::rustls::QuicClientConfig::try_from(rustls_cfg)
+            .context("wrap rustls config for QUIC")?;
+        let client_cfg = ClientConfig::new(Arc::new(quic_cfg));
+
+        let bind: SocketAddr = if server_addr.is_ipv6() {
+            "[::]:0".parse().unwrap()
+        } else {
+            "0.0.0.0:0".parse().unwrap()
+        };
+        let mut endpoint = Endpoint::client(bind).context("Endpoint::client bind")?;
+        endpoint.set_default_client_config(client_cfg);
+
+        let connecting = endpoint
+            .connect(server_addr, server_name)
+            .with_context(|| format!("client connect to {server_addr} as {server_name}"))?;
+        let conn = connecting.await.context("client TLS handshake")?;
+
+        tracing::info!(remote = %conn.remote_address(), "simulator client connected");
+        Ok(Self { endpoint, conn })
+    }
+
+    /// T1 — send one `QuicMessage` over a QUIC datagram (38 B fixed).
+    pub fn send_datagram(&self, msg: &QuicMessage) -> anyhow::Result<()> {
+        let bytes = bytes::Bytes::copy_from_slice(&msg.to_bytes());
+        self.conn.send_datagram(bytes).context("send_datagram")?;
+        Ok(())
+    }
+
+    /// T2 — open a unidirectional stream, write each message as 38 B back-to-back,
+    /// then `finish()` the stream. The substrate sees one or many events per
+    /// stream, ordered within the stream.
+    pub async fn send_uni_stream(&self, msgs: &[QuicMessage]) -> anyhow::Result<()> {
+        let mut send = self.conn.open_uni().await.context("open_uni")?;
+        for msg in msgs {
+            send.write_all(&msg.to_bytes())
+                .await
+                .context("write QuicMessage to uni stream")?;
+        }
+        send.finish().context("finish uni stream")?;
+        Ok(())
+    }
+
+    /// T3 — open a bidirectional stream, write the command (38 B), finish the
+    /// send half, then read the substrate's ack (38 B). Errors if the
+    /// substrate resets the stream (e.g. no handler installed yet) or if the
+    /// connection drops mid-exchange.
+    pub async fn request(&self, command: &QuicMessage) -> anyhow::Result<QuicMessage> {
+        let (mut send, mut recv) = self.conn.open_bi().await.context("open_bi")?;
+        send.write_all(&command.to_bytes())
+            .await
+            .context("write T3 command")?;
+        send.finish().context("finish T3 send half")?;
+
+        let mut buf = [0u8; QuicMessage::WIRE_SIZE];
+        recv.read_exact(&mut buf)
+            .await
+            .context("read T3 ack")?;
+        let ack = QuicMessage::decode(&buf).context("decode T3 ack")?;
+        Ok(ack)
+    }
+
+    /// Close the connection gracefully. Use before dropping in tests so the
+    /// peer's `conn.closed()` resolves cleanly instead of via timeout.
+    pub async fn close(&self) {
+        self.conn.close(0u32.into(), b"client done");
+        self.endpoint.wait_idle().await;
+    }
+}
+
+/// `ServerCertVerifier` that accepts exactly one specific cert by byte
+/// equality. Signature verification still runs through the default provider —
+/// only the chain-validity check is replaced.
+#[derive(Debug)]
+struct TrustExactCert {
+    expected: CertificateDer<'static>,
+    provider: Arc<rustls::crypto::CryptoProvider>,
+}
+
+impl ServerCertVerifier for TrustExactCert {
+    fn verify_server_cert(
+        &self,
+        end_entity: &CertificateDer<'_>,
+        _intermediates: &[CertificateDer<'_>],
+        _server_name: &ServerName<'_>,
+        _ocsp_response: &[u8],
+        _now: UnixTime,
+    ) -> Result<ServerCertVerified, rustls::Error> {
+        if end_entity.as_ref() == self.expected.as_ref() {
+            Ok(ServerCertVerified::assertion())
+        } else {
+            Err(rustls::Error::General(
+                "server cert does not match trusted dev cert".into(),
+            ))
+        }
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        rustls::crypto::verify_tls12_signature(
+            message,
+            cert,
+            dss,
+            &self.provider.signature_verification_algorithms,
+        )
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        rustls::crypto::verify_tls13_signature(
+            message,
+            cert,
+            dss,
+            &self.provider.signature_verification_algorithms,
+        )
+    }
+
+    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
+        self.provider.signature_verification_algorithms.supported_schemes()
+    }
+}
--- a/simulator/src/emitters.rs
+++ b/simulator/src/emitters.rs
@@ -0,0 +1,147 @@
+//! Async emitter tasks for T2 (uni streams) and T3 (bi streams + ack).
+//!
+//! Each emitter ticks at its own rate, opens a fresh stream per event, and
+//! shares a `Connection` with the rest of the simulator. T1 (datagrams) is
+//! driven inline by the main loop so the foreground task owns the progress
+//! reporting; the reliable tiers run as `tokio::spawn`ed background tasks.
+
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+use anyhow::Context;
+use substrate::transport::QuicMessage;
+use tokio::time::MissedTickBehavior;
+
+use crate::profile::{SensorSlot, generate_value};
+
+/// UNIX-epoch microseconds — the wall-clock timestamp the simulator stamps
+/// into every outgoing `QuicMessage`. Substrate-side latency is computed as
+/// `substrate_now_us - msg.timestamp_us`, so this needs to be a real wall
+/// clock both ends share (NTP for two-machine; loopback otherwise).
+pub fn now_us() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_micros() as u64)
+        .unwrap_or(0)
+}
+
+/// T2 emitter — opens a fresh uni stream per event, writes one
+/// `QuicMessage`, and `finish`es. Returns the count of events successfully
+/// delivered when `interrupted` is raised.
+pub async fn run_t2_emitter(
+    conn: quinn::Connection,
+    mut slot: SensorSlot,
+    rate_hz: f64,
+    interrupted: Arc<AtomicBool>,
+    counter: Arc<AtomicU64>,
+) -> u64 {
+    let period = Duration::from_nanos((1.0e9 / rate_hz) as u64);
+    let mut ticker = tokio::time::interval(period);
+    ticker.set_missed_tick_behavior(MissedTickBehavior::Delay);
+    let mut sent: u64 = 0;
+
+    loop {
+        ticker.tick().await;
+        if interrupted.load(Ordering::SeqCst) {
+            break;
+        }
+
+        let msg = QuicMessage {
+            device_id: slot.device_id,
+            sensor_id: slot.sensor_id,
+            raw_value: generate_value(slot.sensor_type, slot.seq),
+            timestamp_us: now_us(),
+            sequence_number: slot.seq,
+            sensor_type: slot.sensor_type.as_u8(),
+        };
+        slot.seq = slot.seq.wrapping_add(1);
+
+        match conn.open_uni().await {
+            Ok(mut send) => {
+                if let Err(e) = send.write_all(&msg.to_bytes()).await {
+                    tracing::warn!(error = %e, "T2 write_all failed");
+                    continue;
+                }
+                if let Err(e) = send.finish() {
+                    tracing::warn!(error = %e, "T2 finish failed");
+                    continue;
+                }
+                sent += 1;
+                counter.store(sent, Ordering::Relaxed);
+            }
+            Err(e) => {
+                tracing::warn!(error = %e, "T2 open_uni failed; emitter exiting");
+                break;
+            }
+        }
+    }
+    sent
+}
+
+/// T3 emitter — opens a fresh bi-stream per command, writes the command,
+/// awaits the ack with a bounded timeout. Returns `(acks_received, timeouts)`.
+pub async fn run_t3_emitter(
+    conn: quinn::Connection,
+    mut slot: SensorSlot,
+    rate_hz: f64,
+    timeout: Duration,
+    interrupted: Arc<AtomicBool>,
+    sent_counter: Arc<AtomicU64>,
+    timeout_counter: Arc<AtomicU64>,
+) -> (u64, u64) {
+    let period = Duration::from_nanos((1.0e9 / rate_hz) as u64);
+    let mut ticker = tokio::time::interval(period);
+    ticker.set_missed_tick_behavior(MissedTickBehavior::Delay);
+    let mut sent: u64 = 0;
+    let mut timeouts: u64 = 0;
+
+    loop {
+        ticker.tick().await;
+        if interrupted.load(Ordering::SeqCst) {
+            break;
+        }
+
+        let cmd = QuicMessage {
+            device_id: slot.device_id,
+            sensor_id: slot.sensor_id,
+            raw_value: generate_value(slot.sensor_type, slot.seq),
+            timestamp_us: now_us(),
+            sequence_number: slot.seq,
+            sensor_type: slot.sensor_type.as_u8(),
+        };
+        slot.seq = slot.seq.wrapping_add(1);
+
+        match tokio::time::timeout(timeout, t3_one_request(&conn, &cmd)).await {
+            Ok(Ok(_ack)) => {
+                sent += 1;
+                sent_counter.store(sent, Ordering::Relaxed);
+            }
+            Ok(Err(e)) => {
+                tracing::warn!(error = %e, "T3 request failed");
+            }
+            Err(_) => {
+                timeouts += 1;
+                timeout_counter.store(timeouts, Ordering::Relaxed);
+                tracing::warn!(?timeout, "T3 ack timed out");
+            }
+        }
+    }
+    (sent, timeouts)
+}
+
+/// Single T3 round-trip: open bi-stream, write 38 B command, `finish` the
+/// send half, read 38 B ack. Used by `run_t3_emitter`.
+async fn t3_one_request(
+    conn: &quinn::Connection,
+    cmd: &QuicMessage,
+) -> anyhow::Result<QuicMessage> {
+    let (mut send, mut recv) = conn.open_bi().await.context("T3 open_bi")?;
+    send.write_all(&cmd.to_bytes())
+        .await
+        .context("T3 write command")?;
+    send.finish().context("T3 finish send half")?;
+    let mut buf = [0u8; QuicMessage::WIRE_SIZE];
+    recv.read_exact(&mut buf).await.context("T3 read ack")?;
+    QuicMessage::decode(&buf).context("T3 decode ack")
+}
--- a/simulator/src/lib.rs
+++ b/simulator/src/lib.rs
@@ -0,0 +1,12 @@
+pub mod client;
+pub mod emitters;
+pub mod profile;
+
+/// Install rustls' default crypto provider. Idempotent: safe to call from
+/// every test, every binary entry, and the substrate process. The `aws_lc_rs`
+/// provider matches what the substrate installs in `main.rs`.
+pub fn install_crypto_provider() {
+    // Returns Err if a provider is already installed; that's the expected
+    // case in any process that's already booted substrate or a sibling test.
+    let _ = rustls::crypto::aws_lc_rs::default_provider().install_default();
+}
--- a/simulator/src/main.rs
+++ b/simulator/src/main.rs
@@ -1,3 +1,320 @@
-fn main() {
-    println!("Hello, world!");
+//! Manual smoke runner / load driver for the substrate.
+//!
+//! Parses the CLI, builds the per-device sensor layout, then drives T1
+//! datagrams in the foreground while T2 and T3 emitters run as background
+//! tokio tasks. Helpers live in the simulator library:
+//!
+//! - `simulator::profile`   — `SensorProfile`, `SensorSlot`, waveform generator
+//! - `simulator::emitters`  — `run_t2_emitter`, `run_t3_emitter`, `now_us`
+//! - `simulator::client`    — Quinn client + TLS trust-by-cert verifier
+
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::time::{Duration, Instant};
+
+use anyhow::{Context, anyhow};
+use clap::{Parser, ValueEnum};
+use simulator::client::SimulatorClient;
+use simulator::emitters::{now_us, run_t2_emitter, run_t3_emitter};
+use simulator::profile::{SensorProfile, build_slots, generate_value};
+use substrate::transport::{QuicMessage, SensorType};
+use tokio::time::MissedTickBehavior;
+use tracing_subscriber::EnvFilter;
+
+#[derive(Parser, Debug)]
+#[command(name = "simulator", about, long_about = None)]
+struct Cli {
+    /// Substrate address (host:port).
+    #[arg(long, default_value = "127.0.0.1:9000")]
+    addr: SocketAddr,
+
+    /// SNI name presented during the TLS handshake.
+    #[arg(long, default_value = "localhost")]
+    server_name: String,
+
+    /// Path to the substrate's PEM cert; used as the exact-match trust anchor.
+    #[arg(long, default_value = "certs/server.crt")]
+    cert: PathBuf,
+
+    /// Sensor mix per device.
+    ///
+    /// - `single` (default): one sensor per device of `--sensor-type`, on
+    ///   `--sensor-id`. Lowest-cardinality, easiest to reason about.
+    /// - `industrial`: five sensors per device on ids 0..4 — Temperature,
+    ///   Humidity, Pressure, Voltage, Current. Lights up every dashboard
+    ///   panel.
+    #[arg(long, value_enum, default_value_t = SensorProfile::Single)]
+    profile: SensorProfile,
+
+    /// Sensor type for the `single` profile. Ignored by `industrial`.
+    #[arg(long, value_enum, default_value_t = CliSensorType::Generic)]
+    sensor_type: CliSensorType,
+
+    /// T1 datagram rate across all (device, sensor) slots (Hz). `0` disables T1.
+    #[arg(long, default_value_t = 20.0)]
+    rate_hz: f64,
+
+    /// T2 uni-stream event rate (Hz). `0` disables T2 (default).
+    #[arg(long, default_value_t = 0.0)]
+    t2_rate_hz: f64,
+
+    /// T3 bidirectional command rate (Hz). `0` disables T3 (default).
+    #[arg(long, default_value_t = 0.0)]
+    t3_rate_hz: f64,
+
+    /// Per-command timeout for T3 ack waits (milliseconds).
+    #[arg(long, default_value_t = 2000)]
+    t3_timeout_ms: u64,
+
+    /// Number of T1 datagrams to send. `0` runs until Ctrl-C.
+    #[arg(long, default_value_t = 10)]
+    count: u64,
+
+    /// Number of distinct device UUIDs to round-robin.
+    #[arg(long, default_value_t = 1)]
+    devices: u32,
+
+    /// Sensor index for the `single` profile. Ignored by `industrial`.
+    #[arg(long, default_value_t = 0)]
+    sensor_id: u16,
+}
+
+#[derive(ValueEnum, Clone, Copy, Debug, Default)]
+enum CliSensorType {
+    #[default]
+    Generic,
+    Temperature,
+    Humidity,
+    Pressure,
+    Voltage,
+    Current,
+}
+
+impl From<CliSensorType> for SensorType {
+    fn from(c: CliSensorType) -> Self {
+        match c {
+            CliSensorType::Generic => SensorType::Generic,
+            CliSensorType::Temperature => SensorType::Temperature,
+            CliSensorType::Humidity => SensorType::Humidity,
+            CliSensorType::Pressure => SensorType::Pressure,
+            CliSensorType::Voltage => SensorType::Voltage,
+            CliSensorType::Current => SensorType::Current,
+        }
+    }
+}
+
+fn validate(cli: &Cli) -> anyhow::Result<()> {
+    if cli.rate_hz < 0.0 {
+        return Err(anyhow!("--rate-hz must be >= 0"));
+    }
+    if cli.t2_rate_hz < 0.0 {
+        return Err(anyhow!("--t2-rate-hz must be >= 0"));
+    }
+    if cli.t3_rate_hz < 0.0 {
+        return Err(anyhow!("--t3-rate-hz must be >= 0"));
+    }
+    if cli.rate_hz == 0.0 && cli.t2_rate_hz == 0.0 && cli.t3_rate_hz == 0.0 {
+        return Err(anyhow!(
+            "at least one of --rate-hz / --t2-rate-hz / --t3-rate-hz must be > 0"
+        ));
+    }
+    if cli.devices == 0 {
+        return Err(anyhow!("--devices must be >= 1"));
+    }
+    Ok(())
+}
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info")),
+        )
+        .init();
+
+    let cli = Cli::parse();
+    validate(&cli)?;
+
+    simulator::install_crypto_provider();
+
+    let mut slots = build_slots(
+        cli.profile,
+        cli.devices,
+        cli.sensor_type.into(),
+        cli.sensor_id,
+    );
+
+    tracing::info!(
+        ?cli.addr,
+        rate_hz = cli.rate_hz,
+        t2_rate_hz = cli.t2_rate_hz,
+        t3_rate_hz = cli.t3_rate_hz,
+        count = cli.count,
+        devices = cli.devices,
+        slots = slots.len(),
+        profile = ?cli.profile,
+        "simulator launching"
+    );
+
+    let client = SimulatorClient::connect(cli.addr, &cli.server_name, &cli.cert)
+        .await
+        .context("connect to substrate")?;
+
+    let interrupted = Arc::new(AtomicBool::new(false));
+    {
+        let flag = interrupted.clone();
+        tokio::spawn(async move {
+            let _ = tokio::signal::ctrl_c().await;
+            tracing::info!("Ctrl-C received, draining…");
+            flag.store(true, Ordering::SeqCst);
+        });
+    }
+
+    // T2 / T3 emitters target slot[0] for their device/sensor identity.
+    let t2_slot = slots[0].clone();
+    let t3_slot = slots[0].clone();
+
+    let t2_sent = Arc::new(AtomicU64::new(0));
+    let t2_handle = if cli.t2_rate_hz > 0.0 {
+        let conn = client.conn.clone();
+        let rate = cli.t2_rate_hz;
+        let interrupted = interrupted.clone();
+        let counter = t2_sent.clone();
+        Some(tokio::spawn(async move {
+            run_t2_emitter(conn, t2_slot, rate, interrupted, counter).await
+        }))
+    } else {
+        None
+    };
+
+    let t3_sent = Arc::new(AtomicU64::new(0));
+    let t3_timeouts = Arc::new(AtomicU64::new(0));
+    let t3_handle = if cli.t3_rate_hz > 0.0 {
+        let conn = client.conn.clone();
+        let rate = cli.t3_rate_hz;
+        let timeout = Duration::from_millis(cli.t3_timeout_ms);
+        let interrupted = interrupted.clone();
+        let sent_counter = t3_sent.clone();
+        let to_counter = t3_timeouts.clone();
+        Some(tokio::spawn(async move {
+            run_t3_emitter(
+                conn,
+                t3_slot,
+                rate,
+                timeout,
+                interrupted,
+                sent_counter,
+                to_counter,
+            )
+            .await
+        }))
+    } else {
+        None
+    };
+
+    let started = Instant::now();
+    let mut t1_sent: u64 = 0;
+    let mut send_errors: u64 = 0;
+
+    if cli.rate_hz > 0.0 {
+        let period = Duration::from_nanos((1.0e9 / cli.rate_hz) as u64);
+        let mut ticker = tokio::time::interval(period);
+        ticker.set_missed_tick_behavior(MissedTickBehavior::Delay);
+
+        let unlimited = cli.count == 0;
+        let mut last_progress = started;
+
+        loop {
+            ticker.tick().await;
+            if interrupted.load(Ordering::SeqCst) {
+                break;
+            }
+            if !unlimited && t1_sent >= cli.count {
+                break;
+            }
+
+            let slot_idx = (t1_sent as usize) % slots.len();
+            let slot = &mut slots[slot_idx];
+            let msg = QuicMessage {
+                device_id: slot.device_id,
+                sensor_id: slot.sensor_id,
+                raw_value: generate_value(slot.sensor_type, slot.seq),
+                timestamp_us: now_us(),
+                sequence_number: slot.seq,
+                sensor_type: slot.sensor_type.as_u8(),
+            };
+            slot.seq = slot.seq.wrapping_add(1);
+            t1_sent += 1;
+
+            if let Err(e) = client.send_datagram(&msg) {
+                send_errors += 1;
+                tracing::warn!(error = %e, "send_datagram failed");
+            }
+
+            let now = Instant::now();
+            if now.duration_since(last_progress) >= Duration::from_secs(1) {
+                let elapsed = now.duration_since(started).as_secs_f64();
+                let t1_hz = (t1_sent as f64) / elapsed.max(1e-9);
+                let t2_now = t2_sent.load(Ordering::Relaxed);
+                let t2_hz = (t2_now as f64) / elapsed.max(1e-9);
+                let t3_now = t3_sent.load(Ordering::Relaxed);
+                let t3_hz = (t3_now as f64) / elapsed.max(1e-9);
+                let t3_to = t3_timeouts.load(Ordering::Relaxed);
+                tracing::info!(
+                    t1_sent,
+                    t2_sent = t2_now,
+                    t3_sent = t3_now,
+                    t3_timeouts = t3_to,
+                    send_errors,
+                    t1_hz = format_args!("{:.1}", t1_hz),
+                    t2_hz = format_args!("{:.1}", t2_hz),
+                    t3_hz = format_args!("{:.1}", t3_hz),
+                    "progress"
+                );
+                last_progress = now;
+            }
+        }
+    } else {
+        while !interrupted.load(Ordering::SeqCst) {
+            tokio::time::sleep(Duration::from_millis(100)).await;
+        }
+    }
+
+    interrupted.store(true, Ordering::SeqCst);
+    let t2_total: u64 = match t2_handle {
+        Some(h) => h.await.unwrap_or_else(|e| {
+            tracing::warn!(error = %e, "T2 emitter task ended unexpectedly");
+            0
+        }),
+        None => 0,
+    };
+    let (t3_total, t3_timeouts_total): (u64, u64) = match t3_handle {
+        Some(h) => h.await.unwrap_or_else(|e| {
+            tracing::warn!(error = %e, "T3 emitter task ended unexpectedly");
+            (0, 0)
+        }),
+        None => (0, 0),
+    };
+
+    let elapsed = started.elapsed().as_secs_f64();
+    let t1_hz = (t1_sent as f64) / elapsed.max(1e-9);
+    let t2_hz = (t2_total as f64) / elapsed.max(1e-9);
+    let t3_hz = (t3_total as f64) / elapsed.max(1e-9);
+    tracing::info!(
+        t1_sent,
+        t2_sent = t2_total,
+        t3_sent = t3_total,
+        t3_timeouts = t3_timeouts_total,
+        send_errors,
+        elapsed_s = format_args!("{:.3}", elapsed),
+        t1_observed_hz = format_args!("{:.1}", t1_hz),
+        t2_observed_hz = format_args!("{:.1}", t2_hz),
+        t3_observed_hz = format_args!("{:.1}", t3_hz),
+        "simulator done"
+    );
+
+    client.close().await;
+    Ok(())
 }
--- a/simulator/src/profile.rs
+++ b/simulator/src/profile.rs
@@ -0,0 +1,88 @@
+//! Per-device sensor layout (the `--profile` CLI flag's runtime form) and the
+//! type-appropriate waveform generators that feed the substrate's Grafana
+//! dashboard with believable numbers.
+
+use clap::ValueEnum;
+use substrate::transport::SensorType;
+use uuid::Uuid;
+
+/// Per-device sensor layout selected by the `--profile` CLI flag.
+///
+/// - `Single`: one sensor per device of a chosen `SensorType`. Lowest
+///   cardinality; the right pick for throughput / latency benchmarks.
+/// - `Industrial`: five sensors per device on ids 0..4 — Temperature,
+///   Humidity, Pressure, Voltage, Current. Lights up every sensor-type
+///   panel in the operator dashboard.
+#[derive(ValueEnum, Clone, Copy, Debug)]
+pub enum SensorProfile {
+    Single,
+    Industrial,
+}
+
+/// A single emitter slot: the `(device, sensor, type)` triple plus the
+/// per-slot monotonic sequence counter that the simulator advances on every
+/// outgoing message.
+#[derive(Clone, Debug)]
+pub struct SensorSlot {
+    pub device_id: Uuid,
+    pub sensor_id: u16,
+    pub sensor_type: SensorType,
+    pub seq: u32,
+}
+
+/// Expand a `(profile, num_devices)` choice into the flat list of slots
+/// the T1 emitter rotates through. Each device gets a fresh UUID.
+pub fn build_slots(
+    profile: SensorProfile,
+    num_devices: u32,
+    default_type: SensorType,
+    default_sensor_id: u16,
+) -> Vec<SensorSlot> {
+    let mut slots = Vec::new();
+    for _ in 0..num_devices {
+        let device_id = Uuid::new_v4();
+        match profile {
+            SensorProfile::Single => {
+                slots.push(SensorSlot {
+                    device_id,
+                    sensor_id: default_sensor_id,
+                    sensor_type: default_type,
+                    seq: 0,
+                });
+            }
+            SensorProfile::Industrial => {
+                for (sensor_id, sensor_type) in [
+                    (0u16, SensorType::Temperature),
+                    (1, SensorType::Humidity),
+                    (2, SensorType::Pressure),
+                    (3, SensorType::Voltage),
+                    (4, SensorType::Current),
+                ] {
+                    slots.push(SensorSlot {
+                        device_id,
+                        sensor_id,
+                        sensor_type,
+                        seq: 0,
+                    });
+                }
+            }
+        }
+    }
+    slots
+}
+
+/// Type-appropriate waveform so the dashboard has something believable to
+/// render. `seq` is the sample index — multiplying by 0.05 gives a
+/// "seconds-like" wall-clock pacing inside the trig functions regardless of
+/// the actual send rate, so panels animate over the same visible period.
+pub fn generate_value(t: SensorType, seq: u32) -> f64 {
+    let t_phase = (seq as f64) * 0.05;
+    match t {
+        SensorType::Temperature => 20.0 + 5.0 * (t_phase / 10.0).sin(),
+        SensorType::Humidity => 50.0 + 20.0 * (t_phase / 15.0).sin(),
+        SensorType::Pressure => 1013.0 + 5.0 * (t_phase / 20.0).cos(),
+        SensorType::Voltage => 230.0 + 0.5 * (t_phase / 3.0).sin(),
+        SensorType::Current => 10.0 + 2.0 * (t_phase / 5.0).cos(),
+        SensorType::Generic => t_phase.sin(),
+    }
+}
--- a/simulator/tests/end_to_end_t1.rs
+++ b/simulator/tests/end_to_end_t1.rs
@@ -0,0 +1,139 @@
+//! End-to-end T1 datagram test: spin up substrate's listener in-process with
+//! channels the test owns, drive a `SimulatorClient` against it, and assert
+//! the datagram lands in the T1 receiver decoded.
+//!
+//! Run with `cargo test -p simulator`.
+
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use std::time::Duration;
+
+use anyhow::Result;
+use simulator::client::SimulatorClient;
+use substrate::config::QuicConfig;
+use substrate::transport::server::{accept_loop, bind_endpoint};
+use substrate::transport::{QuicMessage, SensorType, T1Sender, T2Sender, T3Sender};
+use tokio::sync::mpsc;
+use uuid::Uuid;
+
+fn cert_path(name: &str) -> PathBuf {
+    [env!("CARGO_MANIFEST_DIR"), "..", "certs", name].iter().collect()
+}
+
+fn loopback_config(cert: PathBuf, key: PathBuf) -> QuicConfig {
+    QuicConfig {
+        // Port 0 lets the OS pick a free ephemeral port — tests can run in
+        // parallel without colliding on a fixed bind.
+        server_port: 0,
+        server_interface: "127.0.0.1".to_string(),
+        server_cert: cert.to_string_lossy().into_owned(),
+        server_key: key.to_string_lossy().into_owned(),
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn t1_datagram_decoded_into_ecs_channel() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    // Bind the substrate's listener on an ephemeral port.
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    // Channels the test owns — gives us direct visibility into what the T1
+    // demux pushes into the ECS bridge.
+    let (t1_tx, mut t1_rx) = mpsc::channel(64);
+    let (t2_tx, _t2_rx) = mpsc::channel(64);
+    let (t3_tx, _t3_rx) = mpsc::channel(64);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    // Connect a client and send one datagram.
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    let sent = QuicMessage {
+        device_id: Uuid::from_u128(0xdead_beef_cafe_f00d_1234_5678_90ab_cdef),
+        sensor_id: 7,
+        raw_value: 42.0,
+        timestamp_us: 1_700_000_000_000_001,
+        sequence_number: 1,
+        sensor_type: SensorType::Temperature.as_u8(),
+    };
+    client.send_datagram(&sent)?;
+
+    // Wait for the substrate's read_datagrams reader to push it into T1.
+    let received = tokio::time::timeout(Duration::from_secs(2), t1_rx.recv())
+        .await
+        .expect("did not observe T1 datagram within 2s")
+        .expect("T1 channel closed unexpectedly");
+
+    assert_eq!(received, sent);
+
+    client.close().await;
+    server_task.abort();
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn t1_burst_preserves_order_and_count() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    // T1 capacity 64 ≥ burst size 32 so nothing is dropped under loopback.
+    let (t1_tx, mut t1_rx) = mpsc::channel(64);
+    let (t2_tx, _t2_rx) = mpsc::channel(8);
+    let (t3_tx, _t3_rx) = mpsc::channel(8);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    let device = Uuid::from_u128(0xa1a2_a3a4_b5b6_b7b8_c9ca_cbcc_cdce_cfd0);
+    const BURST: u32 = 32;
+    for seq in 0..BURST {
+        let msg = QuicMessage {
+            device_id: device,
+            sensor_id: 0,
+            raw_value: f64::from(seq),
+            timestamp_us: 1_700_000_000_000_000 + u64::from(seq),
+            sequence_number: seq,
+            sensor_type: SensorType::Generic.as_u8(),
+        };
+        client.send_datagram(&msg)?;
+    }
+
+    // Drain BURST messages with a per-message timeout. Loopback shouldn't
+    // reorder QUIC datagrams within a single connection.
+    for expected_seq in 0..BURST {
+        let msg = tokio::time::timeout(Duration::from_secs(2), t1_rx.recv())
+            .await
+            .unwrap_or_else(|_| panic!("missed datagram seq={expected_seq}"))
+            .expect("T1 channel closed");
+        assert_eq!(msg.sequence_number, expected_seq);
+        assert_eq!(msg.device_id, device);
+        assert_eq!(msg.raw_value, f64::from(expected_seq));
+    }
+
+    client.close().await;
+    server_task.abort();
+    Ok(())
+}
--- a/simulator/tests/end_to_end_t2.rs
+++ b/simulator/tests/end_to_end_t2.rs
@@ -0,0 +1,163 @@
+//! End-to-end T2 (unidirectional stream) tests. Mirrors the T1 harness:
+//! spin up substrate's listener with channels owned by the test, drive a
+//! `SimulatorClient` against it, assert what arrives on the T2 receiver.
+//!
+//! Run with `cargo test -p simulator`.
+
+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use std::time::Duration;
+
+use anyhow::Result;
+use simulator::client::SimulatorClient;
+use substrate::config::QuicConfig;
+use substrate::transport::server::{accept_loop, bind_endpoint};
+use substrate::transport::{QuicMessage, SensorType, T1Sender, T2Sender, T3Sender};
+use tokio::sync::mpsc;
+use uuid::Uuid;
+
+fn cert_path(name: &str) -> PathBuf {
+    [env!("CARGO_MANIFEST_DIR"), "..", "certs", name].iter().collect()
+}
+
+fn loopback_config(cert: PathBuf, key: PathBuf) -> QuicConfig {
+    QuicConfig {
+        server_port: 0,
+        server_interface: "127.0.0.1".to_string(),
+        server_cert: cert.to_string_lossy().into_owned(),
+        server_key: key.to_string_lossy().into_owned(),
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn t2_single_stream_preserves_order() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    let (t1_tx, _t1_rx) = mpsc::channel(64);
+    let (t2_tx, mut t2_rx) = mpsc::channel(64);
+    let (t3_tx, _t3_rx) = mpsc::channel(64);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    let device = Uuid::from_u128(0x0011_2233_4455_6677_8899_aabb_ccdd_eeff);
+    const N: u32 = 10;
+    let msgs: Vec<QuicMessage> = (0..N)
+        .map(|i| QuicMessage {
+            device_id: device,
+            sensor_id: 1,
+            raw_value: f64::from(i),
+            timestamp_us: 1_700_000_000_000_000 + u64::from(i),
+            sequence_number: i,
+            sensor_type: SensorType::Pressure.as_u8(),
+        })
+        .collect();
+
+    client.send_uni_stream(&msgs).await?;
+
+    for expected in &msgs {
+        let received = tokio::time::timeout(Duration::from_secs(2), t2_rx.recv())
+            .await
+            .expect("missed T2 message")
+            .expect("T2 channel closed unexpectedly");
+        assert_eq!(received, *expected);
+    }
+
+    client.close().await;
+    server_task.abort();
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn t2_concurrent_streams_each_internally_ordered() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    let (t1_tx, _t1_rx) = mpsc::channel(64);
+    let (t2_tx, mut t2_rx) = mpsc::channel(256);
+    let (t3_tx, _t3_rx) = mpsc::channel(64);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    // 4 devices × 8 messages each on independent uni streams. Cross-stream
+    // ordering may interleave; per-stream ordering must be strict.
+    const DEVICES: usize = 4;
+    const PER_DEVICE: u32 = 8;
+    let device_ids: Vec<Uuid> = (0..DEVICES).map(|_| Uuid::new_v4()).collect();
+
+    let mut handles = Vec::with_capacity(DEVICES);
+    for &device in &device_ids {
+        let conn = client.conn.clone();
+        handles.push(tokio::spawn(async move {
+            let msgs: Vec<QuicMessage> = (0..PER_DEVICE)
+                .map(|i| QuicMessage {
+                    device_id: device,
+                    sensor_id: 0,
+                    raw_value: f64::from(i),
+                    timestamp_us: 1_700_000_000_000_000 + u64::from(i),
+                    sequence_number: i,
+                    sensor_type: SensorType::Generic.as_u8(),
+                })
+                .collect();
+            // Use the connection directly so each task owns its own stream
+            // — same wire pattern as `SimulatorClient::send_uni_stream`.
+            let mut send = conn.open_uni().await.expect("open_uni");
+            for m in &msgs {
+                send.write_all(&m.to_bytes()).await.expect("write_all");
+            }
+            send.finish().expect("finish");
+        }));
+    }
+    for h in handles {
+        h.await?;
+    }
+
+    // Drain DEVICES × PER_DEVICE messages, group by device, assert per-device
+    // sequence numbers are strictly increasing from 0.
+    let total = DEVICES * PER_DEVICE as usize;
+    let mut by_device: HashMap<Uuid, Vec<u32>> = HashMap::new();
+    for _ in 0..total {
+        let msg = tokio::time::timeout(Duration::from_secs(2), t2_rx.recv())
+            .await
+            .expect("missed T2 message")
+            .expect("T2 channel closed unexpectedly");
+        by_device.entry(msg.device_id).or_default().push(msg.sequence_number);
+    }
+
+    assert_eq!(by_device.len(), DEVICES, "expected one entry per device");
+    for (dev, seqs) in &by_device {
+        let expected: Vec<u32> = (0..PER_DEVICE).collect();
+        assert_eq!(seqs, &expected, "out-of-order or missing sequence for {dev}");
+    }
+
+    client.close().await;
+    server_task.abort();
+    Ok(())
+}
--- a/simulator/tests/end_to_end_t3.rs
+++ b/simulator/tests/end_to_end_t3.rs
@@ -0,0 +1,152 @@
+//! End-to-end T3 (bidirectional stream + oneshot ack) tests. Same shape as
+//! the T1/T2 harnesses: spin up substrate's listener with channels owned by
+//! the test, run a "fake ECS" task that drains the T3 receiver and either
+//! replies or drops the oneshot, and assert the client observes the right
+//! behaviour.
+//!
+//! Run with `cargo test -p simulator`.
+
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use std::time::Duration;
+
+use anyhow::Result;
+use simulator::client::SimulatorClient;
+use substrate::config::QuicConfig;
+use substrate::transport::server::{accept_loop, bind_endpoint};
+use substrate::transport::{QuicMessage, SensorType, T1Sender, T2Sender, T3Sender};
+use tokio::sync::mpsc;
+use uuid::Uuid;
+
+fn cert_path(name: &str) -> PathBuf {
+    [env!("CARGO_MANIFEST_DIR"), "..", "certs", name].iter().collect()
+}
+
+fn loopback_config(cert: PathBuf, key: PathBuf) -> QuicConfig {
+    QuicConfig {
+        server_port: 0,
+        server_interface: "127.0.0.1".to_string(),
+        server_cert: cert.to_string_lossy().into_owned(),
+        server_key: key.to_string_lossy().into_owned(),
+    }
+}
+
+/// Marker `timestamp_us` the fake ECS stamps onto every ack so the test can
+/// distinguish a real reply from any echo of the command's own timestamp.
+const ACK_MARKER_TS: u64 = 999_999_999_999;
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn t3_round_trip_with_fake_handler() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    let (t1_tx, _t1_rx) = mpsc::channel(64);
+    let (t2_tx, _t2_rx) = mpsc::channel(64);
+    let (t3_tx, mut t3_rx) = mpsc::channel(64);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    // Fake ECS handler: drain T3 inbounds, mark the timestamp, send back.
+    let handler = tokio::spawn(async move {
+        while let Some(inbound) = t3_rx.recv().await {
+            let mut ack = inbound.command;
+            ack.timestamp_us = ACK_MARKER_TS;
+            // Ignore send error (client may have disconnected before listening).
+            let _ = inbound.reply.send(ack);
+        }
+    });
+
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    let cmd = QuicMessage {
+        device_id: Uuid::from_u128(0xa5a5_a5a5_5a5a_5a5a_a5a5_5a5a_a5a5_5a5a),
+        sensor_id: 3,
+        raw_value: 1.5,
+        timestamp_us: 1_700_000_000_000_000,
+        sequence_number: 7,
+        sensor_type: SensorType::Voltage.as_u8(),
+    };
+
+    let ack = tokio::time::timeout(Duration::from_secs(2), client.request(&cmd))
+        .await
+        .expect("T3 ack timed out")?;
+
+    assert_eq!(ack.device_id, cmd.device_id, "ack should preserve device_id");
+    assert_eq!(ack.sensor_id, cmd.sensor_id, "ack should preserve sensor_id");
+    assert_eq!(
+        ack.sequence_number, cmd.sequence_number,
+        "ack should preserve sequence_number for correlation"
+    );
+    assert_eq!(ack.timestamp_us, ACK_MARKER_TS, "fake ECS should stamp the marker");
+
+    client.close().await;
+    handler.abort();
+    server_task.abort();
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn t3_no_handler_resets_stream() -> Result<()> {
+    simulator::install_crypto_provider();
+
+    let cert = cert_path("server.crt");
+    let key = cert_path("server.key");
+    let cfg = loopback_config(cert.clone(), key);
+
+    let endpoint = bind_endpoint(&cfg)?;
+    let server_addr: SocketAddr = endpoint.local_addr()?;
+
+    let (t1_tx, _t1_rx) = mpsc::channel(64);
+    let (t2_tx, _t2_rx) = mpsc::channel(64);
+    let (t3_tx, mut t3_rx) = mpsc::channel(64);
+
+    let server_task = tokio::spawn(accept_loop(
+        endpoint,
+        T1Sender::new(t1_tx),
+        T2Sender::new(t2_tx),
+        T3Sender::new(t3_tx),
+    ));
+
+    // Fake ECS that *drops* every oneshot — simulates "no handler installed",
+    // which is the placeholder state in `ingest_system` until M4 lands.
+    let handler = tokio::spawn(async move {
+        while let Some(inbound) = t3_rx.recv().await {
+            drop(inbound);
+        }
+    });
+
+    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;
+
+    let cmd = QuicMessage {
+        device_id: Uuid::new_v4(),
+        sensor_id: 0,
+        raw_value: 0.0,
+        timestamp_us: 0,
+        sequence_number: 0,
+        sensor_type: SensorType::Generic.as_u8(),
+    };
+
+    let result = tokio::time::timeout(Duration::from_secs(2), client.request(&cmd)).await;
+    let inner = result.expect("client.request should not hang when stream is reset");
+    assert!(
+        inner.is_err(),
+        "expected request to fail when substrate resets the stream, got Ok({:?})",
+        inner.ok()
+    );
+
+    client.close().await;
+    handler.abort();
+    server_task.abort();
+    Ok(())
+}
--- a/substrate/Cargo.toml
+++ b/substrate/Cargo.toml
@@ -11,7 +11,12 @@ tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 quinn = { version = "0.11" }
 rustls = { version = "0.23" }
+rustls-pemfile = "2"
+rustls-pki-types = "1"
 tokio = { version = "1", features = ["full"] }
 uuid = { version = "1.23", features = ["v4"] }
 figment = { version = "0.10", features = ["toml", "env"] }
 serde = { version = "1", features = ["derive"] }
+metrics = "0.24"
+metrics-exporter-prometheus = "0.17"
+memory-stats = "1"
--- a/substrate/src/config.rs
+++ b/substrate/src/config.rs
@@ -7,6 +7,7 @@ use serde::{Deserialize, Serialize};
 pub struct AppConfig {
    pub network: QuicConfig,
    pub simulation: SimulationConfig,
+    pub observability: ObservabilityConfig,
 }

 #[derive(Debug, Serialize, Deserialize)]
@@ -23,6 +24,15 @@ pub struct QuicConfig {
    pub server_key: String,
 }

+#[derive(Debug, Serialize, Deserialize)]
+pub struct ObservabilityConfig {
+    /// When true, install the Prometheus exporter at startup. Disable for
+    /// environments where the metrics port collides or scraping is undesired.
+    pub metrics_enabled: bool,
+    /// Bind address for the `/metrics` HTTP listener.
+    pub metrics_listen: String,
+}
+
 impl Default for AppConfig {
    fn default() -> Self {
        Self {
@@ -36,6 +46,10 @@ impl Default for AppConfig {
                tick_rate_hz: 60,
                max_entities: 10000,
            },
+            observability: ObservabilityConfig {
+                metrics_enabled: true,
+                metrics_listen: "0.0.0.0:9100".to_string(),
+            },
        }
    }
 }
--- a/substrate/src/lib.rs
+++ b/substrate/src/lib.rs
@@ -0,0 +1,4 @@
+pub mod config;
+pub mod observability;
+pub mod transport;
+pub mod world;
--- a/substrate/src/main.rs
+++ b/substrate/src/main.rs
@@ -1,9 +1,10 @@
-mod transport;
-mod config;
-
 use bevy::prelude::*;
 use tracing_subscriber::EnvFilter;
-use crate::config::AppConfig;
+
+use substrate::config::AppConfig;
+use substrate::observability::ObservabilityPlugin;
+use substrate::transport;
+use substrate::world::WorldPlugin;

 fn main() {
    tracing_subscriber::fmt()
@@ -12,12 +13,22 @@ fn main() {
        )
        .init();

+    // rustls 0.23 requires an explicit default crypto provider. Quinn's
+    // ServerConfig::with_single_cert otherwise panics at first use.
+    rustls::crypto::aws_lc_rs::default_provider()
+        .install_default()
+        .expect("install rustls default crypto provider");
+
    let config = AppConfig::load("config.toml").expect("Failed to load config");
    tracing::info!(?config, "substrate starting");

+    // Plugin order matters: EcsQuicTransportPlugin inserts the TokioHandle
+    // resource ObservabilityPlugin reads in its `build()`.
    App::new()
        .insert_resource(config)
        .add_plugins(MinimalPlugins)
-        .add_plugins(transport::ecs::EcsQuicTransportPlugin {})
+        .add_plugins(transport::ecs::EcsQuicTransportPlugin)
+        .add_plugins(WorldPlugin)
+        .add_plugins(ObservabilityPlugin)
        .run();
 }
--- a/substrate/src/observability.rs
+++ b/substrate/src/observability.rs
@@ -0,0 +1,116 @@
+//! M5 — Prometheus-format `/metrics` exporter installation and counter
+//! pre-registration.
+//!
+//! Counters and histograms are emitted from the demux path
+//! ([`crate::transport::server`]) and the world systems
+//! ([`crate::world::ingest_system`], [`crate::world::simulation_system`],
+//! [`crate::world::export_system`]). This module's only job is:
+//!
+//! 1. Install the global metrics recorder + HTTP listener on the existing
+//!    tokio runtime, once at startup.
+//! 2. Pre-register every counter at value 0 so panels render "0" rather than
+//!    "No data" before the first event of a given kind fires.
+//!
+//! ## Runtime telemetry
+//!
+//! - `substrate_received_total{tier=t1|t2|t3}`           — counter
+//! - `substrate_dropped_total{tier=t1}`                  — counter (T1 lossy)
+//! - `substrate_decode_errors_total{tier=t1|t2|t3}`      — counter
+//! - `substrate_t3_no_handler_total`                     — counter
+//! - `substrate_latency_us{tier=t1|t2|t3}`               — histogram
+//! - `substrate_tick_hz`                                 — gauge
+//! - `substrate_entities`                                — gauge
+//! - `substrate_channel_depth{tier=t1|t2|t3}`            — gauge
+//! - `substrate_channel_capacity{tier=t1|t2|t3}`         — gauge
+//! - `substrate_rss_bytes`                               — gauge
+//!
+//! ## Digital-twin surface (operator dashboard)
+//!
+//! - `sensor_aggregate{type=…, stat=count|mean|min|max}` — gauge
+//! - `substrate_threshold_crossings_total{type, direction}` — counter
+
+use std::net::SocketAddr;
+
+use bevy::prelude::*;
+use metrics::counter;
+use metrics_exporter_prometheus::PrometheusBuilder;
+
+use crate::config::AppConfig;
+use crate::transport::SensorType;
+use crate::transport::ecs::TokioHandle;
+
+pub struct ObservabilityPlugin;
+
+impl Plugin for ObservabilityPlugin {
+    fn build(&self, app: &mut App) {
+        let config = app
+            .world()
+            .get_resource::<AppConfig>()
+            .expect("AppConfig must be inserted before ObservabilityPlugin");
+
+        if !config.observability.metrics_enabled {
+            tracing::info!("metrics exporter disabled by config");
+            return;
+        }
+
+        let listen: SocketAddr = config
+            .observability
+            .metrics_listen
+            .parse()
+            .expect("invalid metrics_listen address in config");
+
+        let runtime_handle = app
+            .world()
+            .get_resource::<TokioHandle>()
+            .expect("TokioHandle must be inserted before ObservabilityPlugin (load order: transport plugin first)")
+            .0
+            .clone();
+
+        // PrometheusBuilder::install spawns the HTTP listener via tokio::spawn,
+        // which requires being inside a runtime context.
+        let _guard = runtime_handle.enter();
+        PrometheusBuilder::new()
+            .with_http_listener(listen)
+            .install()
+            .expect("install prometheus exporter");
+        drop(_guard);
+
+        tracing::info!(?listen, "metrics exporter installed");
+
+        pre_register_counters();
+    }
+}
+
+/// Pre-register every counter at value 0 so Grafana sees a series to plot
+/// even before the first event of that kind. Without this, the Prometheus
+/// exporter omits any counter that has never been incremented, and panels
+/// render "No data" — confusing when the metric exists, the counter is just
+/// genuinely zero (e.g., `substrate_t3_no_handler_total` in normal operation).
+fn pre_register_counters() {
+    for tier in ["t1", "t2", "t3"] {
+        counter!("substrate_received_total", "tier" => tier).increment(0);
+        counter!("substrate_decode_errors_total", "tier" => tier).increment(0);
+    }
+    counter!("substrate_dropped_total", "tier" => "t1").increment(0);
+    counter!("substrate_t3_no_handler_total").increment(0);
+
+    // Threshold crossings — bounded `|SensorType| × 2` cardinality, all
+    // pre-registered so dashboard panels show "0" instead of "No data".
+    for t in [
+        SensorType::Generic,
+        SensorType::Temperature,
+        SensorType::Humidity,
+        SensorType::Pressure,
+        SensorType::Voltage,
+        SensorType::Current,
+    ] {
+        for direction in ["up", "down"] {
+            counter!(
+                "substrate_threshold_crossings_total",
+                "type" => t.label_str(),
+                "direction" => direction
+            )
+            .increment(0);
+        }
+    }
+}
--- a/substrate/src/transport/ecs.rs
+++ b/substrate/src/transport/ecs.rs
@@ -1,68 +1,111 @@
 use std::sync::Mutex;
+
 use bevy::prelude::*;
+use bevy::state::app::StatesPlugin;
+use tokio::runtime::Handle;
 use tokio::sync::mpsc;
-use crate::transport::QuicMessage;
-use crate::transport::server::run_substrate_server;
+
+use crate::config::AppConfig;
+use crate::transport::{QuicMessage, T1Sender, T2Sender, T3Inbound, T3Sender};
+use crate::transport::server::{accept_loop, bind_endpoint};
+use crate::transport::state::ServerState;

 const T1_CAPACITY: usize = 1024;
 const T2_CAPACITY: usize = 512;
 const T3_CAPACITY: usize = 256;

-pub struct EcsQuicTransportPlugin{}
+pub struct EcsQuicTransportPlugin;

+/// Receive halves of the three tier channels, wrapped so they can sit in a
+/// Bevy `Resource`. The `world` module's ingest system is the sole reader.
 #[derive(Resource)]
-struct BridgeReceivers {
-    t1: Mutex<mpsc::Receiver<QuicMessage>>,
-    t2: Mutex<mpsc::Receiver<QuicMessage>>,
-    t3: Mutex<mpsc::Receiver<QuicMessage>>,
+pub(crate) struct BridgeReceivers {
+    pub(crate) t1: Mutex<mpsc::Receiver<QuicMessage>>,
+    pub(crate) t2: Mutex<mpsc::Receiver<QuicMessage>>,
+    pub(crate) t3: Mutex<mpsc::Receiver<T3Inbound>>,
 }

-fn ingest_system(bridge: Res<BridgeReceivers>){
-    let mut t1 = bridge.t1.lock().unwrap();
-    // Tier 1: drain up to N messages, drop the rest
-    for _ in 0..T1_CAPACITY {
-        match t1.try_recv() {
-            Ok(msg) => { /* write RawSensorData */ }
-            Err(_) => break,
-        }
+#[derive(Resource, Clone)]
+pub(crate) struct BridgeSenders {
+    pub(crate) t1: T1Sender,
+    pub(crate) t2: T2Sender,
+    pub(crate) t3: T3Sender,
 }

-    // T2/T3: drain completely, these are low volume
-    let mut t2 = bridge.t2.lock().unwrap();
-    while let Ok(msg) = t2.try_recv() { /* ... */ }
+#[derive(Resource, Clone)]
+pub(crate) struct TokioHandle(pub(crate) Handle);

-    let mut t3 = bridge.t3.lock().unwrap();
-    while let Ok(msg) = t3.try_recv() { /* ... */ }
+/// Bring up the QUIC listener using the loaded `AppConfig` and transition to
+/// `ServerState::Started`. Runs once via `OnEnter(ServerState::Starting)`.
+fn start_quic_server(
+    config: Res<AppConfig>,
+    senders: Res<BridgeSenders>,
+    runtime: Res<TokioHandle>,
+    mut next: ResMut<NextState<ServerState>>,
+) {
+    tracing::info!("entering ServerState::Starting — bringing up QUIC listener");
+
+    // `Endpoint::server` is sync but needs a tokio runtime context for
+    // `Handle::current()`; entering the runtime is enough — no async block
+    // required.
+    let _guard = runtime.0.enter();
+    let endpoint = bind_endpoint(&config.network).expect("failed to bind QUIC endpoint");
+    drop(_guard);
+
+    tracing::info!(local = ?endpoint.local_addr().ok(), "QUIC listener bound");
+
+    let s = senders.clone();
+    runtime.0.spawn(accept_loop(endpoint, s.t1, s.t2, s.t3));
+
+    next.set(ServerState::Started);
+    tracing::info!("ServerState::Started");
 }

 impl Plugin for EcsQuicTransportPlugin {
    fn build(&self, app: &mut App) {
-        // Create the channels for multi-thread communication
-        let (t1_tx, t1_rx) =
-            mpsc::channel::<QuicMessage>(T1_CAPACITY);
-        let (t2_tx, t2_rx) =
-            mpsc::channel::<QuicMessage>(T2_CAPACITY);
-        let (t3_tx, t3_rx) =
-            mpsc::channel::<QuicMessage>(T3_CAPACITY);
+        // Three-tier bridge between the tokio-side QUIC accept loop and the
+        // ECS PreUpdate ingest system (in the `world` module).
+        let (t1_tx, t1_rx) = mpsc::channel::<QuicMessage>(T1_CAPACITY);
+        let (t2_tx, t2_rx) = mpsc::channel::<QuicMessage>(T2_CAPACITY);
+        let (t3_tx, t3_rx) = mpsc::channel::<T3Inbound>(T3_CAPACITY);

-        let quic_handle = std::thread::spawn(move || {
+        // Spawn a tokio runtime on a dedicated OS thread, ship its Handle back
+        // to the ECS, and keep the runtime alive for the lifetime of the app
+        // by parking on `pending()`.
+        let (handle_tx, handle_rx) = std::sync::mpsc::sync_channel::<Handle>(1);
+        std::thread::Builder::new()
+            .name("quic-runtime".to_string())
+            .spawn(move || {
                let rt = tokio::runtime::Builder::new_multi_thread()
                    .worker_threads(2)
                    .enable_all()
+                    .thread_name("quic-worker")
                    .build()
-                .unwrap();
+                    .expect("build tokio runtime");
+                handle_tx
+                    .send(rt.handle().clone())
+                    .expect("send tokio Handle to ECS");
+                rt.block_on(std::future::pending::<()>());
+            })
+            .expect("spawn quic-runtime thread");

-            rt.block_on(async move {
-                run_substrate_server(t1_tx, t2_tx, t3_tx).await;
-            });
-        });
+        let handle = handle_rx.recv().expect("receive tokio Handle");

-        app.insert_resource(BridgeReceivers {
+        // Bevy 0.18 split state machinery into its own plugin; under
+        // MinimalPlugins it isn't installed by default.
+        app.add_plugins(StatesPlugin)
+            .init_state::<ServerState>()
+            .insert_resource(TokioHandle(handle))
+            .insert_resource(BridgeSenders {
+                t1: T1Sender::new(t1_tx),
+                t2: T2Sender::new(t2_tx),
+                t3: T3Sender::new(t3_tx),
+            })
+            .insert_resource(BridgeReceivers {
                t1: Mutex::new(t1_rx),
                t2: Mutex::new(t2_rx),
                t3: Mutex::new(t3_rx),
-        });
-
-        app.add_systems(PreUpdate, ingest_system);
+            })
+            .add_systems(OnEnter(ServerState::Starting), start_quic_server);
    }
 }
--- a/substrate/src/transport/mod.rs
+++ b/substrate/src/transport/mod.rs
@@ -1,27 +1,100 @@
 pub mod ecs;
-mod server;
+pub mod server;
+pub mod state;

-/// One sensor sample on the wire.
+use tokio::sync::{mpsc, oneshot};
+
+/// Logical type of a sensor reading. Travels in `QuicMessage::sensor_type`
+/// so the substrate (and any downstream dashboard) knows which units / range
+/// / visualisation applies to the `raw_value`.
 ///
-/// Fixed 38-byte little-endian layout — same on x86_64 and aarch64 (the two
+/// Forward compat: unknown discriminants decode as `Generic`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
+#[repr(u8)]
+pub enum SensorType {
+    #[default]
+    Generic = 0,
+    Temperature = 1,
+    Humidity = 2,
+    Pressure = 3,
+    Voltage = 4,
+    Current = 5,
+}
+
+impl SensorType {
+    pub fn from_u8(b: u8) -> Self {
+        match b {
+            1 => Self::Temperature,
+            2 => Self::Humidity,
+            3 => Self::Pressure,
+            4 => Self::Voltage,
+            5 => Self::Current,
+            _ => Self::Generic,
+        }
+    }
+
+    pub fn as_u8(self) -> u8 {
+        self as u8
+    }
+
+    /// Lowercase label used as a Prometheus label value.
+    pub fn label_str(self) -> &'static str {
+        match self {
+            Self::Generic => "generic",
+            Self::Temperature => "temperature",
+            Self::Humidity => "humidity",
+            Self::Pressure => "pressure",
+            Self::Voltage => "voltage",
+            Self::Current => "current",
+        }
+    }
+
+    /// SI / engineering unit string for Grafana axis labels.
+    pub fn unit_str(self) -> &'static str {
+        match self {
+            Self::Generic => "",
+            Self::Temperature => "°C",
+            Self::Humidity => "%",
+            Self::Pressure => "hPa",
+            Self::Voltage => "V",
+            Self::Current => "A",
+        }
+    }
+}
+
+/// One sample (T1/T2 sensor reading or T3 actuator command/ack) on the wire.
+///
+/// Fixed 39-byte little-endian layout — same on x86_64 and aarch64 (the two
 /// evaluation hosts), so encode/decode is effectively a memcpy.
 ///
 /// ```text
 ///   offset  size  field
 ///   ------  ----  --------------------------
 ///        0    16  device_id          (UUID)
-///       16     2  data_stream_id     (u16)
+///       16     2  sensor_id          (u16)
 ///       18     8  raw_value          (f64)
 ///       26     8  timestamp_us       (u64)
 ///       34     4  sequence_number    (u32)
+///       38     1  sensor_type        (u8 — `SensorType` discriminant)
 /// ```
+///
+/// Field semantics:
+/// - `device_id` — UUID of the originating device (or target, for T3 commands).
+/// - `sensor_id` — logical sensor/actuator on that device (per-device index).
+/// - `raw_value` — sensor reading (T1/T2) or actuator setpoint/feedback (T3).
+/// - `timestamp_us` — capture time on the device clock for T1/T2; server-side
+///   ack time on T3 replies.
+/// - `sequence_number` — monotonic counter per `(device_id, sensor_id)` for
+///   T1/T2; correlation id linking T3 command and ack.
+/// - `sensor_type` — `SensorType` discriminant, decoded via `SensorType::from_u8`.
 #[derive(Debug, Clone, Default, Copy, PartialEq)]
 pub struct QuicMessage {
    pub device_id: uuid::Uuid,
-    pub data_stream_id: u16,
+    pub sensor_id: u16,
    pub raw_value: f64,
    pub timestamp_us: u64,
    pub sequence_number: u32,
+    pub sensor_type: u8,
 }

 #[derive(Debug, thiserror::Error)]
@@ -32,7 +105,7 @@ pub enum WireError {

 impl QuicMessage {
    /// Bytes on the wire — fixed-size, no length prefix.
-    pub const WIRE_SIZE: usize = 38;
+    pub const WIRE_SIZE: usize = 39;

    pub fn encode_to(&self, buf: &mut [u8]) -> Result<(), WireError> {
        if buf.len() != Self::WIRE_SIZE {
@@ -42,10 +115,11 @@ impl QuicMessage {
            });
        }
        buf[0..16].copy_from_slice(self.device_id.as_bytes());
-        buf[16..18].copy_from_slice(&self.data_stream_id.to_le_bytes());
+        buf[16..18].copy_from_slice(&self.sensor_id.to_le_bytes());
        buf[18..26].copy_from_slice(&self.raw_value.to_le_bytes());
        buf[26..34].copy_from_slice(&self.timestamp_us.to_le_bytes());
        buf[34..38].copy_from_slice(&self.sequence_number.to_le_bytes());
+        buf[38] = self.sensor_type;
        Ok(())
    }

@@ -66,12 +140,113 @@ impl QuicMessage {
        id_bytes.copy_from_slice(&buf[0..16]);
        Ok(Self {
            device_id: uuid::Uuid::from_bytes(id_bytes),
-            data_stream_id: u16::from_le_bytes(buf[16..18].try_into().unwrap()),
+            sensor_id: u16::from_le_bytes(buf[16..18].try_into().unwrap()),
            raw_value: f64::from_le_bytes(buf[18..26].try_into().unwrap()),
            timestamp_us: u64::from_le_bytes(buf[26..34].try_into().unwrap()),
            sequence_number: u32::from_le_bytes(buf[34..38].try_into().unwrap()),
+            sensor_type: buf[38],
        })
    }
+
+    /// Convenience accessor — decodes `sensor_type` to the typed enum.
+    pub fn typ(&self) -> SensorType {
+        SensorType::from_u8(self.sensor_type)
+    }
+}
+
+// --- Per-tier bridge senders -----------------------------------------------
+//
+// Three newtypes encode the paper's tier semantics into the type system so
+// the demux can't mix them up:
+//
+//   * T1 (datagrams)        — lossy; `try_send` drops on full
+//   * T2 (uni streams)      — reliable, ordered; `send().await` backpressures
+//   * T3 (bi streams)       — reliable command + per-command oneshot reply
+
+/// Tier 1 — high-frequency telemetry over QUIC datagrams. Full channel drops.
+#[derive(Clone)]
+pub struct T1Sender {
+    inner: mpsc::Sender<QuicMessage>,
+}
+
+impl T1Sender {
+    pub fn new(inner: mpsc::Sender<QuicMessage>) -> Self {
+        Self { inner }
+    }
+
+    /// Returns `true` if queued, `false` if dropped (channel full or closed).
+    pub fn send_lossy(&self, msg: QuicMessage) -> bool {
+        self.inner.try_send(msg).is_ok()
+    }
+
+    /// Currently queued messages — used for channel-depth gauges.
+    pub fn depth(&self) -> usize {
+        self.inner.max_capacity().saturating_sub(self.inner.capacity())
+    }
+
+    pub fn capacity(&self) -> usize {
+        self.inner.max_capacity()
+    }
+}
+
+/// Tier 2 — ordered events over a QUIC unidirectional stream. Awaits on full.
+#[derive(Clone)]
+pub struct T2Sender {
+    inner: mpsc::Sender<QuicMessage>,
+}
+
+impl T2Sender {
+    pub fn new(inner: mpsc::Sender<QuicMessage>) -> Self {
+        Self { inner }
+    }
+
+    pub async fn send(
+        &self,
+        msg: QuicMessage,
+    ) -> Result<(), mpsc::error::SendError<QuicMessage>> {
+        self.inner.send(msg).await
+    }
+
+    pub fn depth(&self) -> usize {
+        self.inner.max_capacity().saturating_sub(self.inner.capacity())
+    }
+
+    pub fn capacity(&self) -> usize {
+        self.inner.max_capacity()
+    }
+}
+
+/// Tier 3 — actuator command on a QUIC bidirectional stream, paired with a
+/// `oneshot` channel the ECS uses to write the ack back over the same stream.
+pub struct T3Inbound {
+    pub command: QuicMessage,
+    pub reply: oneshot::Sender<QuicMessage>,
+}
+
+#[derive(Clone)]
+pub struct T3Sender {
+    inner: mpsc::Sender<T3Inbound>,
+}
+
+impl T3Sender {
+    pub fn new(inner: mpsc::Sender<T3Inbound>) -> Self {
+        Self { inner }
+    }
+
+    pub async fn send(
+        &self,
+        inbound: T3Inbound,
+    ) -> Result<(), mpsc::error::SendError<T3Inbound>> {
+        self.inner.send(inbound).await
+    }
+
+    pub fn depth(&self) -> usize {
+        self.inner.max_capacity().saturating_sub(self.inner.capacity())
+    }
+
+    pub fn capacity(&self) -> usize {
+        self.inner.max_capacity()
+    }
 }

 #[cfg(test)]
@@ -80,33 +255,35 @@ mod tests {

    #[test]
    fn wire_size_matches_fields() {
-        assert_eq!(QuicMessage::WIRE_SIZE, 16 + 2 + 8 + 8 + 4);
+        assert_eq!(QuicMessage::WIRE_SIZE, 16 + 2 + 8 + 8 + 4 + 1);
    }

    #[test]
    fn roundtrip_preserves_all_fields() {
        let msg = QuicMessage {
            device_id: uuid::Uuid::from_u128(0x0123456789abcdef_fedcba9876543210),
-            data_stream_id: 0xBEEF,
+            sensor_id: 0xBEEF,
            raw_value: -273.15,
            timestamp_us: 1_700_000_000_000_001,
            sequence_number: 42,
+            sensor_type: SensorType::Temperature.as_u8(),
        };
        let bytes = msg.to_bytes();
        assert_eq!(bytes.len(), QuicMessage::WIRE_SIZE);
        let decoded = QuicMessage::decode(&bytes).unwrap();
        assert_eq!(msg, decoded);
+        assert_eq!(decoded.typ(), SensorType::Temperature);
    }

    #[test]
    fn decode_rejects_wrong_length() {
        assert!(matches!(
-            QuicMessage::decode(&[0u8; 37]),
-            Err(WireError::BadLength { expected: 38, got: 37 })
+            QuicMessage::decode(&[0u8; 38]),
+            Err(WireError::BadLength { expected: 39, got: 38 })
        ));
        assert!(matches!(
-            QuicMessage::decode(&[0u8; 39]),
-            Err(WireError::BadLength { expected: 38, got: 39 })
+            QuicMessage::decode(&[0u8; 40]),
+            Err(WireError::BadLength { expected: 39, got: 40 })
        ));
    }

@@ -114,13 +291,22 @@ mod tests {
    fn encode_layout_is_little_endian() {
        let msg = QuicMessage {
            device_id: uuid::Uuid::nil(),
-            data_stream_id: 0x0102,
+            sensor_id: 0x0102,
            raw_value: 0.0,
            timestamp_us: 0,
            sequence_number: 0x04030201,
+            sensor_type: SensorType::Humidity.as_u8(),
        };
        let bytes = msg.to_bytes();
        assert_eq!(&bytes[16..18], &[0x02, 0x01]);
        assert_eq!(&bytes[34..38], &[0x01, 0x02, 0x03, 0x04]);
+        assert_eq!(bytes[38], SensorType::Humidity.as_u8());
+    }
+
+    #[test]
+    fn unknown_sensor_type_decodes_as_generic() {
+        assert_eq!(SensorType::from_u8(0), SensorType::Generic);
+        assert_eq!(SensorType::from_u8(99), SensorType::Generic);
+        assert_eq!(SensorType::from_u8(255), SensorType::Generic);
    }
 }
--- a/substrate/src/transport/server.rs
+++ b/substrate/src/transport/server.rs
@@ -1,8 +1,350 @@
-use tokio::sync::mpsc::Sender;
-use crate::transport::QuicMessage;
+use std::net::SocketAddr;
+use std::sync::Arc;

-pub async fn run_substrate_server(t1_tx: Sender<QuicMessage>,
-                        t2_tx: Sender<QuicMessage>,
-                        t3_tx: Sender<QuicMessage>) {
+use anyhow::{Context, anyhow};
+use metrics::counter;
+use quinn::{
+    Connection, Endpoint, Incoming, RecvStream, SendStream, ServerConfig, StreamId, TransportConfig,
+};
+use rustls_pki_types::{CertificateDer, PrivateKeyDer};
+use tokio::sync::oneshot;

+use crate::config::QuicConfig;
+use crate::transport::{QuicMessage, T1Sender, T2Sender, T3Inbound, T3Sender};
+
+/// Datagram receive buffer in bytes. Sized to absorb microbursts at the
+/// telemetry rates.
+const DATAGRAM_RECV_BUFFER_BYTES: usize = 256 * 1024;
+
+/// Load the cert chain + private key from disk and build a Quinn `ServerConfig`.
+pub fn build_server_config(cfg: &QuicConfig) -> anyhow::Result<ServerConfig> {
+    let cert_pem = std::fs::read(&cfg.server_cert)
+        .with_context(|| format!("read server_cert at {}", cfg.server_cert))?;
+    let key_pem = std::fs::read(&cfg.server_key)
+        .with_context(|| format!("read server_key at {}", cfg.server_key))?;
+
+    let certs: Vec<CertificateDer<'static>> = rustls_pemfile::certs(&mut cert_pem.as_slice())
+        .collect::<Result<_, _>>()
+        .with_context(|| format!("parse PEM certs at {}", cfg.server_cert))?;
+    if certs.is_empty() {
+        return Err(anyhow!("no certificates found in {}", cfg.server_cert));
+    }
+
+    let key: PrivateKeyDer<'static> = rustls_pemfile::private_key(&mut key_pem.as_slice())
+        .with_context(|| format!("parse PEM key at {}", cfg.server_key))?
+        .ok_or_else(|| anyhow!("no private key found in {}", cfg.server_key))?;
+
+    let mut server_config =
+        ServerConfig::with_single_cert(certs, key).context("build Quinn ServerConfig")?;
+
+    // Explicit transport config so the values driving evaluation are visible
+    // in source and at startup, not buried in Quinn's defaults.
+    let mut transport = TransportConfig::default();
+    transport.datagram_receive_buffer_size(Some(DATAGRAM_RECV_BUFFER_BYTES));
+    server_config.transport = Arc::new(transport);
+
+    tracing::info!(
+        datagram_recv_buffer_bytes = DATAGRAM_RECV_BUFFER_BYTES,
+        "Quinn TransportConfig tuned"
+    );
+
+    Ok(server_config)
+}
+
+/// Bind the listener. Must be called from inside a tokio runtime context
+/// (Quinn relies on `Handle::current()` internally).
+pub fn bind_endpoint(cfg: &QuicConfig) -> anyhow::Result<Endpoint> {
+    let server_config = build_server_config(cfg)?;
+    let addr: SocketAddr = format!("{}:{}", cfg.server_interface, cfg.server_port)
+        .parse()
+        .with_context(|| {
+            format!(
+                "invalid bind address {}:{}",
+                cfg.server_interface, cfg.server_port
+            )
+        })?;
+    Endpoint::server(server_config, addr).context("Endpoint::server bind")
+}
+
+/// Accept loop: per-connection senders are cloned from the tier handles and
+/// shipped into `handle_incoming` for orchestration.
+pub async fn accept_loop(endpoint: Endpoint, t1: T1Sender, t2: T2Sender, t3: T3Sender) {
+    tracing::info!(local = ?endpoint.local_addr().ok(), "QUIC accept loop running");
+    while let Some(incoming) = endpoint.accept().await {
+        let t1 = t1.clone();
+        let t2 = t2.clone();
+        let t3 = t3.clone();
+        tokio::spawn(handle_incoming(incoming, t1, t2, t3));
+    }
+    tracing::info!("QUIC accept loop exited");
+}
+
+/// Per-connection orchestrator. Performs the handshake and spawns one reader
+/// per tier, then waits for the connection to close and joins the readers.
+async fn handle_incoming(incoming: Incoming, t1: T1Sender, t2: T2Sender, t3: T3Sender) {
+    let conn = match incoming.await {
+        Ok(c) => c,
+        Err(e) => {
+            tracing::warn!(error = %e, "handshake failed");
+            return;
+        }
+    };
+    let remote = conn.remote_address();
+    tracing::info!(?remote, "connection established");
+
+    // One task per tier — fully wired across T1/T2/T3.
+    let dgram_task = tokio::spawn(read_datagrams(conn.clone(), t1));
+    let uni_task = tokio::spawn(read_uni_streams(conn.clone(), t2));
+    let bi_task = tokio::spawn(accept_bi_streams(conn.clone(), t3));
+
+    let _ = conn.closed().await;
+
+    if let Err(e) = dgram_task.await {
+        tracing::warn!(?remote, error = %e, "T1 datagram task ended unexpectedly");
+    }
+    if let Err(e) = uni_task.await {
+        tracing::warn!(?remote, error = %e, "T2 uni stream task ended unexpectedly");
+    }
+    if let Err(e) = bi_task.await {
+        tracing::warn!(?remote, error = %e, "T3 bi stream task ended unexpectedly");
+    }
+    tracing::info!(?remote, "connection closed");
+}
+
+/// T1 — read QUIC datagrams, decode each as a fixed-size `QuicMessage`, push
+/// into the lossy T1 channel.
+async fn read_datagrams(conn: Connection, t1: T1Sender) {
+    let remote = conn.remote_address();
+    let mut received: u64 = 0;
+    let mut dropped: u64 = 0;
+    let mut decode_errors: u64 = 0;
+
+    loop {
+        match conn.read_datagram().await {
+            Ok(bytes) => match QuicMessage::decode(&bytes[..]) {
+                Ok(msg) => {
+                    received += 1;
+                    counter!("substrate_received_total", "tier" => "t1").increment(1);
+                    if !t1.send_lossy(msg) {
+                        dropped += 1;
+                        counter!("substrate_dropped_total", "tier" => "t1").increment(1);
+                        tracing::trace!(?remote, "T1 channel full, datagram dropped");
+                    }
+                }
+                Err(e) => {
+                    decode_errors += 1;
+                    counter!("substrate_decode_errors_total", "tier" => "t1").increment(1);
+                    tracing::warn!(
+                        ?remote,
+                        len = bytes.len(),
+                        error = %e,
+                        "T1 datagram decode failed"
+                    );
+                }
+            },
+            Err(e) => {
+                tracing::debug!(
+                    ?remote,
+                    received,
+                    dropped,
+                    decode_errors,
+                    error = %e,
+                    "T1 datagram reader ended"
+                );
+                return;
+            }
+        }
+    }
+}
+
+/// T2 — accept unidirectional streams. Each accepted stream gets its own task
+/// reading 38-byte chunks until EOF (one stream may carry one event or many).
+/// Cross-stream interleaving is allowed; ordering is only guaranteed *within*
+/// a stream, matching QUIC's stream semantics.
+async fn read_uni_streams(conn: Connection, t2: T2Sender) {
+    let remote = conn.remote_address();
+    let mut streams_accepted: u64 = 0;
+
+    loop {
+        let recv = match conn.accept_uni().await {
+            Ok(s) => s,
+            Err(e) => {
+                tracing::debug!(
+                    ?remote,
+                    streams_accepted,
+                    error = %e,
+                    "T2 uni accept loop ended"
+                );
+                return;
+            }
+        };
+        streams_accepted += 1;
+        let t2 = t2.clone();
+        tokio::spawn(read_one_uni_stream(remote, recv, t2));
+    }
+}
+
+/// Per-stream worker for T2. Reads fixed-size `QuicMessage`s back-to-back,
+/// awaits backpressure on the T2 channel, and resets the stream on a decode
+/// failure (one corrupt stream shouldn't take down the whole connection).
+async fn read_one_uni_stream(remote: SocketAddr, mut recv: RecvStream, t2: T2Sender) {
+    let stream_id: StreamId = recv.id();
+    let mut buf = [0u8; QuicMessage::WIRE_SIZE];
+    let mut count: u64 = 0;
+
+    loop {
+        match recv.read_exact(&mut buf).await {
+            Ok(()) => match QuicMessage::decode(&buf) {
+                Ok(msg) => {
+                    count += 1;
+                    counter!("substrate_received_total", "tier" => "t2").increment(1);
+                    if t2.send(msg).await.is_err() {
+                        // T2 receiver dropped (substrate shutting down).
+                        tracing::warn!(
+                            ?remote,
+                            ?stream_id,
+                            count,
+                            "T2 channel closed; abandoning stream"
+                        );
+                        return;
+                    }
+                }
+                Err(e) => {
+                    counter!("substrate_decode_errors_total", "tier" => "t2").increment(1);
+                    tracing::warn!(
+                        ?remote,
+                        ?stream_id,
+                        count,
+                        error = %e,
+                        "T2 decode failed; resetting stream"
+                    );
+                    let _ = recv.stop(0u32.into());
+                    return;
+                }
+            },
+            Err(e) => {
+                tracing::trace!(
+                    ?remote,
+                    ?stream_id,
+                    count,
+                    error = %e,
+                    "T2 uni stream ended"
+                );
+                return;
+            }
+        }
+    }
+}
+
+/// T3 — accept bidirectional streams. Each stream is one command/ack
+/// exchange, modeled per the paper's "per-command oneshot channels": the
+/// reader pushes a `T3Inbound { command, reply }` to the ECS, awaits the
+/// response on `reply_rx`, and writes it back on the same stream.
+async fn accept_bi_streams(conn: Connection, t3: T3Sender) {
+    let remote = conn.remote_address();
+    let mut streams_accepted: u64 = 0;
+
+    loop {
+        let (send, recv) = match conn.accept_bi().await {
+            Ok(s) => s,
+            Err(e) => {
+                tracing::debug!(
+                    ?remote,
+                    streams_accepted,
+                    error = %e,
+                    "T3 bi accept loop ended"
+                );
+                return;
+            }
+        };
+        streams_accepted += 1;
+        let t3 = t3.clone();
+        tokio::spawn(read_one_bi_stream(remote, send, recv, t3));
+    }
+}
+
+/// Per-stream worker for T3. Reads exactly one command, ships it with a
+/// `oneshot::Sender` to the ECS, awaits the reply, writes it back. If the
+/// ECS drops the oneshot (no handler installed), the stream is reset so the
+/// client sees an explicit reset instead of a half-open stream.
+async fn read_one_bi_stream(
+    remote: SocketAddr,
+    mut send: SendStream,
+    mut recv: RecvStream,
+    t3: T3Sender,
+) {
+    let stream_id: StreamId = recv.id();
+
+    let mut buf = [0u8; QuicMessage::WIRE_SIZE];
+    if let Err(e) = recv.read_exact(&mut buf).await {
+        tracing::trace!(
+            ?remote,
+            ?stream_id,
+            error = %e,
+            "T3: incomplete command read; closing"
+        );
+        return;
+    }
+    let command = match QuicMessage::decode(&buf) {
+        Ok(m) => m,
+        Err(e) => {
+            counter!("substrate_decode_errors_total", "tier" => "t3").increment(1);
+            tracing::warn!(
+                ?remote,
+                ?stream_id,
+                error = %e,
+                "T3 command decode failed; resetting stream"
+            );
+            let _ = recv.stop(0u32.into());
+            let _ = send.reset(0u32.into());
+            return;
+        }
+    };
+    counter!("substrate_received_total", "tier" => "t3").increment(1);
+
+    let (reply_tx, reply_rx) = oneshot::channel::<QuicMessage>();
+    let inbound = T3Inbound {
+        command,
+        reply: reply_tx,
+    };
+    if t3.send(inbound).await.is_err() {
+        tracing::warn!(?remote, ?stream_id, "T3 channel closed; abandoning command");
+        let _ = send.reset(0u32.into());
+        return;
+    }
+
+    let response = match reply_rx.await {
+        Ok(msg) => msg,
+        Err(_) => {
+            // ECS dropped the oneshot. With M4's handler installed this
+            // shouldn't happen normally; if it does, the stream is reset so
+            // the client sees a clean signal.
+            counter!("substrate_t3_no_handler_total").increment(1);
+            tracing::debug!(
+                ?remote,
+                ?stream_id,
+                "T3: no handler for command, resetting stream"
+            );
+            let _ = send.reset(0u32.into());
+            return;
+        }
+    };
+
+    if let Err(e) = send.write_all(&response.to_bytes()).await {
+        tracing::warn!(
+            ?remote,
+            ?stream_id,
+            error = %e,
+            "T3 ack write failed"
+        );
+        return;
+    }
+    if let Err(e) = send.finish() {
+        tracing::warn!(
+            ?remote,
+            ?stream_id,
+            error = %e,
+            "T3 ack finish failed"
+        );
+    }
 }
--- a/substrate/src/transport/state.rs
+++ b/substrate/src/transport/state.rs
@@ -0,0 +1,13 @@
+use bevy::prelude::States;
+
+/// Lifecycle of the QUIC listener inside the ECS schedule.
+///
+/// `Starting` is the default; `OnEnter(Starting)` performs the bind and, on
+/// success, transitions to `Started`. A `Failed` variant will join when we
+/// add proper error surfacing — for now a bind failure panics the app.
+#[derive(States, Debug, Clone, Copy, Default, Eq, PartialEq, Hash)]
+pub enum ServerState {
+    #[default]
+    Starting,
+    Started,
+}
--- a/substrate/src/world/components.rs
+++ b/substrate/src/world/components.rs
@@ -0,0 +1,97 @@
+//! Components attached to per-sensor entities, plus the per-type threshold
+//! table used by `simulation_system`'s crossing detection.
+//!
+//! Each (device, sensor) pair becomes one entity tagged with `Asset` and
+//! carrying `DeviceId` + `SensorId` + `SensorTypeTag` + `RawSensorData` +
+//! `SmoothedValue`.
+
+use bevy::prelude::*;
+
+use crate::transport::SensorType;
+
+/// Marker — every (device, sensor) pair becomes one entity tagged `Asset`.
+#[derive(Component, Debug, Default, Clone, Copy)]
+pub struct Asset;
+
+#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct DeviceId(pub uuid::Uuid);
+
+#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct SensorId(pub u16);
+
+/// Sensor type — set on entity creation from the first message that names
+/// the (device, sensor) pair, then immutable. We don't track type changes:
+/// a given (device_id, sensor_id) is one logical sensor with one type for
+/// the lifetime of the run.
+#[derive(Component, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct SensorTypeTag(pub SensorType);
+
+/// Latest reading from this (device, sensor). Updated in place by
+/// `ingest_system`; read by simulation/export/diagnostics.
+#[derive(Component, Debug, Default, Clone, Copy, PartialEq)]
+pub struct RawSensorData {
+    pub raw_value: f64,
+    pub timestamp_us: u64,
+    pub sequence_number: u32,
+}
+
+pub const SMOOTHED_WINDOW: usize = 16;
+
+/// Rolling-window mean of the last `SMOOTHED_WINDOW` raw readings, plus a
+/// hysteresis flag for threshold-crossing detection. Maintained by
+/// `simulation_system` — this is the bit of the ECS that does honest
+/// digital-twin transform work, not just write-through of incoming samples.
+#[derive(Component, Debug, Clone, Copy)]
+pub struct SmoothedValue {
+    ring: [f64; SMOOTHED_WINDOW],
+    head: usize,
+    filled: u16,
+    pub mean: f64,
+    pub above_threshold: bool,
+}
+
+impl Default for SmoothedValue {
+    fn default() -> Self {
+        Self {
+            ring: [0.0; SMOOTHED_WINDOW],
+            head: 0,
+            filled: 0,
+            mean: 0.0,
+            above_threshold: false,
+        }
+    }
+}
+
+impl SmoothedValue {
+    /// Push a new sample. Non-finite values (NaN / ±∞) are ignored — the
+    /// smoothed state stays whatever it was. This matters because T3 acks
+    /// can carry NaN when the substrate has never seen the target sensor.
+    pub fn push(&mut self, v: f64) {
+        if !v.is_finite() {
+            return;
+        }
+        self.ring[self.head] = v;
+        self.head = (self.head + 1) % SMOOTHED_WINDOW;
+        if (self.filled as usize) < SMOOTHED_WINDOW {
+            self.filled += 1;
+        }
+        let n = self.filled as usize;
+        let sum: f64 = self.ring.iter().take(n).sum();
+        self.mean = sum / n as f64;
+    }
+}
+
+/// Per-type threshold for `simulation_system`'s crossing detection. Chosen
+/// mid-band against the simulator's waveforms so crossings actually fire
+/// during a demo; in a real deployment these would be alarm thresholds
+/// supplied by config.
+pub(super) fn threshold_for(t: SensorType) -> f64 {
+    match t {
+        SensorType::Generic => 0.0,
+        SensorType::Temperature => 22.0,  // °C — simulator oscillates 15..25
+        SensorType::Humidity => 55.0,     // %  — 30..70
+        SensorType::Pressure => 1014.0,   // hPa — 1008..1018
+        SensorType::Voltage => 230.2,     // V  — 229.5..230.5
+        SensorType::Current => 10.5,      // A  — 8..12
+    }
+}
--- a/substrate/src/world/mod.rs
+++ b/substrate/src/world/mod.rs
@@ -0,0 +1,52 @@
+//! ECS world: the five paper-named systems plus the components and resources
+//! they operate on.
+//!
+//! ```text
+//!   components.rs   ── per-sensor components + per-type threshold table
+//!   resources.rs    ── SensorRegistry, DiagnosticsState, ExportSampleState
+//!   systems.rs      ── ingest / fault_injection / simulation / export / diagnostics
+//!   tests.rs        ── unit tests (#[cfg(test)] only)
+//! ```
+//!
+//! Each (device, sensor) pair becomes one entity with `Asset` + `DeviceId` +
+//! `SensorId` + `SensorTypeTag` + `RawSensorData` + `SmoothedValue`.
+//! `ingest_system` upserts on every incoming `QuicMessage`; the registry maps
+//! `(Uuid, u16) → Entity` for O(1) lookup.
+
+mod components;
+mod resources;
+mod systems;
+
+#[cfg(test)]
+mod tests;
+
+use bevy::prelude::*;
+use bevy::state::condition::in_state;
+
+use crate::transport::state::ServerState;
+
+pub use components::{
+    Asset, DeviceId, RawSensorData, SMOOTHED_WINDOW, SensorId, SensorTypeTag, SmoothedValue,
+};
+pub use resources::SensorRegistry;
+
+pub struct WorldPlugin;
+
+impl Plugin for WorldPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<SensorRegistry>()
+            .init_resource::<resources::DiagnosticsState>()
+            .init_resource::<resources::ExportSampleState>()
+            .add_systems(
+                PreUpdate,
+                (systems::fault_injection_system, systems::ingest_system)
+                    .chain()
+                    .run_if(in_state(ServerState::Started)),
+            )
+            .add_systems(Update, systems::simulation_system)
+            .add_systems(
+                PostUpdate,
+                (systems::export_system, systems::diagnostics_system).chain(),
+            );
+    }
+}
--- a/substrate/src/world/resources.rs
+++ b/substrate/src/world/resources.rs
@@ -0,0 +1,48 @@
+//! Bevy `Resource`s consumed by the world's systems.
+
+use std::collections::HashMap;
+use std::time::Instant;
+
+use bevy::prelude::{Entity, Resource};
+
+/// O(1) lookup `(device_id, sensor_id) → Entity`. Populated lazily by the
+/// ingest system; queried by export/diagnostics.
+#[derive(Resource, Default)]
+pub struct SensorRegistry {
+    pub(crate) map: HashMap<(uuid::Uuid, u16), Entity>,
+}
+
+impl SensorRegistry {
+    pub fn entity_count(&self) -> usize {
+        self.map.len()
+    }
+}
+
+/// Rolling counter of ticks since the last `diagnostics` log line was emitted.
+#[derive(Resource)]
+pub(super) struct DiagnosticsState {
+    pub(super) last_log: Instant,
+    pub(super) ticks_since_log: u64,
+}
+
+impl Default for DiagnosticsState {
+    fn default() -> Self {
+        Self {
+            last_log: Instant::now(),
+            ticks_since_log: 0,
+        }
+    }
+}
+
+/// Rate-limiter for `export_system` — runs at the ECS tick rate but only
+/// emits gauges once per second.
+#[derive(Resource)]
+pub(super) struct ExportSampleState {
+    pub(super) last_sample: Instant,
+}
+
+impl Default for ExportSampleState {
+    fn default() -> Self {
+        Self { last_sample: Instant::now() }
+    }
+}
--- a/substrate/src/world/systems.rs
+++ b/substrate/src/world/systems.rs
@@ -0,0 +1,278 @@
+//! The five paper-named ECS systems and their private helpers.
+//!
+//! Scheduler placement (configured in [`super::WorldPlugin`]):
+//!
+//! | Schedule  | Systems                              |
+//! |-----------|--------------------------------------|
+//! | PreUpdate | fault_injection → ingest             |
+//! | Update    | simulation                           |
+//! | PostUpdate| export → diagnostics                 |
+
+use std::collections::HashMap;
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+
+use bevy::prelude::*;
+use metrics::{counter, gauge, histogram};
+
+use crate::transport::ecs::{BridgeReceivers, BridgeSenders};
+use crate::transport::{QuicMessage, SensorType};
+
+use super::components::{
+    Asset, DeviceId, RawSensorData, SensorId, SensorTypeTag, SmoothedValue, threshold_for,
+};
+use super::resources::{DiagnosticsState, ExportSampleState, SensorRegistry};
+
+/// T1 batch limit per tick. Anything beyond this stays in the channel and
+/// either drains next tick or gets dropped on full (T1's contract is lossy).
+const T1_INGEST_BATCH: usize = 1024;
+
+/// Drain the three tier channels into ECS state.
+///
+/// T1: bounded batch (lossy); T2: full drain (reliable); T3: full drain, with
+/// each command answered by an ack carrying the device's current sensor value.
+pub(super) fn ingest_system(
+    bridge: Res<BridgeReceivers>,
+    mut registry: ResMut<SensorRegistry>,
+    mut commands: Commands,
+    mut q: Query<&mut RawSensorData>,
+) {
+    let now = now_us();
+
+    // T1 — datagrams.
+    {
+        let mut t1 = bridge.t1.lock().unwrap();
+        for _ in 0..T1_INGEST_BATCH {
+            match t1.try_recv() {
+                Ok(msg) => {
+                    histogram!("substrate_latency_us", "tier" => "t1")
+                        .record(now.saturating_sub(msg.timestamp_us) as f64);
+                    upsert_reading(&mut registry, &mut commands, &mut q, msg);
+                }
+                Err(_) => break,
+            }
+        }
+    }
+
+    // T2 — uni streams.
+    {
+        let mut t2 = bridge.t2.lock().unwrap();
+        while let Ok(msg) = t2.try_recv() {
+            histogram!("substrate_latency_us", "tier" => "t2")
+                .record(now.saturating_sub(msg.timestamp_us) as f64);
+            upsert_reading(&mut registry, &mut commands, &mut q, msg);
+        }
+    }
+
+    // T3 — bidirectional commands. Reply with the device's most recent
+    // sensor value (NaN if we've never seen this (device, sensor) before).
+    {
+        let mut t3 = bridge.t3.lock().unwrap();
+        while let Ok(inbound) = t3.try_recv() {
+            histogram!("substrate_latency_us", "tier" => "t3")
+                .record(now.saturating_sub(inbound.command.timestamp_us) as f64);
+            let key = (inbound.command.device_id, inbound.command.sensor_id);
+            let current_value = registry
+                .map
+                .get(&key)
+                .and_then(|&e| q.get(e).ok())
+                .map(|d| d.raw_value)
+                .unwrap_or(f64::NAN);
+            let ack = QuicMessage {
+                device_id: inbound.command.device_id,
+                sensor_id: inbound.command.sensor_id,
+                raw_value: current_value,
+                timestamp_us: now_us(),
+                sequence_number: inbound.command.sequence_number,
+                sensor_type: inbound.command.sensor_type,
+            };
+            // Ignore send errors: the demux task may have given up if the
+            // connection died while we were processing.
+            let _ = inbound.reply.send(ack);
+        }
+    }
+}
+
+fn upsert_reading(
+    registry: &mut SensorRegistry,
+    commands: &mut Commands,
+    q: &mut Query<&mut RawSensorData>,
+    msg: QuicMessage,
+) {
+    let key = (msg.device_id, msg.sensor_id);
+    let data = RawSensorData {
+        raw_value: msg.raw_value,
+        timestamp_us: msg.timestamp_us,
+        sequence_number: msg.sequence_number,
+    };
+
+    if let Some(&entity) = registry.map.get(&key) {
+        // Common case: existing entity, mutate in place.
+        if let Ok(mut existing) = q.get_mut(entity) {
+            *existing = data;
+        } else {
+            // Edge case: entity was registered earlier in *this* tick via
+            // `commands.spawn`, so the components aren't in the archetype
+            // yet (`Commands` is deferred). Queue another insert; last write
+            // wins when Commands flushes.
+            commands.entity(entity).insert(data);
+        }
+        return;
+    }
+
+    let entity = commands
+        .spawn((
+            Asset,
+            DeviceId(msg.device_id),
+            SensorId(msg.sensor_id),
+            SensorTypeTag(SensorType::from_u8(msg.sensor_type)),
+            SmoothedValue::default(),
+            data,
+        ))
+        .id();
+    registry.map.insert(key, entity);
+}
+
+/// Stub — M6 inserts loss/delay here for benchmark scenarios.
+pub(super) fn fault_injection_system() {}
+
+/// Per-sensor digital-twin transform. Pulls each entity's latest
+/// `RawSensorData` into a sliding-window mean (`SmoothedValue`), and emits
+/// `substrate_threshold_crossings_total{type, direction}` when that mean
+/// transitions across the per-type threshold. The `Changed<RawSensorData>`
+/// filter restricts the scan to entities updated *this tick*, so the cost
+/// scales with ingress rate, not fleet size.
+pub(super) fn simulation_system(
+    mut q: Query<(&SensorTypeTag, &RawSensorData, &mut SmoothedValue), Changed<RawSensorData>>,
+) {
+    for (st, raw, mut smoothed) in q.iter_mut() {
+        smoothed.push(raw.raw_value);
+        let now_above = smoothed.mean > threshold_for(st.0);
+        if now_above != smoothed.above_threshold {
+            smoothed.above_threshold = now_above;
+            let dir = if now_above { "up" } else { "down" };
+            counter!(
+                "substrate_threshold_crossings_total",
+                "type" => st.0.label_str(),
+                "direction" => dir
+            )
+            .increment(1);
+        }
+    }
+}
+
+/// Sample ECS-side gauges into the Prometheus exporter. Runs every tick but
+/// only emits once per second to keep cost negligible. This is the system
+/// the paper's §Architecture diagram calls `ExportSystem`.
+pub(super) fn export_system(
+    senders: Res<BridgeSenders>,
+    registry: Res<SensorRegistry>,
+    sensors_q: Query<(&SensorTypeTag, &RawSensorData)>,
+    mut state: ResMut<ExportSampleState>,
+) {
+    let now = Instant::now();
+    if now.duration_since(state.last_sample) < Duration::from_secs(1) {
+        return;
+    }
+    state.last_sample = now;
+
+    // ---- runtime telemetry ----
+    gauge!("substrate_entities").set(registry.entity_count() as f64);
+
+    gauge!("substrate_channel_depth", "tier" => "t1").set(senders.t1.depth() as f64);
+    gauge!("substrate_channel_depth", "tier" => "t2").set(senders.t2.depth() as f64);
+    gauge!("substrate_channel_depth", "tier" => "t3").set(senders.t3.depth() as f64);
+
+    gauge!("substrate_channel_capacity", "tier" => "t1").set(senders.t1.capacity() as f64);
+    gauge!("substrate_channel_capacity", "tier" => "t2").set(senders.t2.capacity() as f64);
+    gauge!("substrate_channel_capacity", "tier" => "t3").set(senders.t3.capacity() as f64);
+
+    if let Some(stats) = memory_stats::memory_stats() {
+        gauge!("substrate_rss_bytes").set(stats.physical_mem as f64);
+    }
+
+    // ---- sensor data aggregates (per type) ----
+    let mut by_type: HashMap<&'static str, Aggregate> = HashMap::new();
+    for (st, data) in &sensors_q {
+        by_type
+            .entry(st.0.label_str())
+            .or_insert_with(Aggregate::new)
+            .push(data.raw_value);
+    }
+    for (label, agg) in &by_type {
+        gauge!("sensor_aggregate", "type" => *label, "stat" => "count").set(agg.count as f64);
+        if agg.count > 0 {
+            gauge!("sensor_aggregate", "type" => *label, "stat" => "mean").set(agg.mean());
+            gauge!("sensor_aggregate", "type" => *label, "stat" => "min").set(agg.min);
+            gauge!("sensor_aggregate", "type" => *label, "stat" => "max").set(agg.max);
+        }
+    }
+}
+
+pub(super) fn diagnostics_system(
+    mut state: ResMut<DiagnosticsState>,
+    registry: Res<SensorRegistry>,
+) {
+    state.ticks_since_log += 1;
+    let now = Instant::now();
+    let elapsed = now.duration_since(state.last_log);
+    if elapsed >= Duration::from_secs(1) {
+        let tick_hz = state.ticks_since_log as f64 / elapsed.as_secs_f64();
+        gauge!("substrate_tick_hz").set(tick_hz);
+        tracing::info!(
+            tick_hz = format_args!("{:.1}", tick_hz),
+            entities = registry.entity_count(),
+            "diagnostics"
+        );
+        state.last_log = now;
+        state.ticks_since_log = 0;
+    }
+}
+
+fn now_us() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_micros() as u64)
+        .unwrap_or(0)
+}
+
+/// Per-type accumulator for `export_system`'s sensor aggregates. NaN-safe.
+#[derive(Debug, Clone, Copy)]
+struct Aggregate {
+    count: u64,
+    sum: f64,
+    min: f64,
+    max: f64,
+}
+
+impl Aggregate {
+    fn new() -> Self {
+        Self {
+            count: 0,
+            sum: 0.0,
+            min: f64::INFINITY,
+            max: f64::NEG_INFINITY,
+        }
+    }
+
+    fn push(&mut self, v: f64) {
+        if !v.is_finite() {
+            return;
+        }
+        self.count += 1;
+        self.sum += v;
+        if v < self.min {
+            self.min = v;
+        }
+        if v > self.max {
+            self.max = v;
+        }
+    }
+
+    fn mean(&self) -> f64 {
+        if self.count == 0 {
+            f64::NAN
+        } else {
+            self.sum / self.count as f64
+        }
+    }
+}
--- a/substrate/src/world/tests.rs
+++ b/substrate/src/world/tests.rs
@@ -0,0 +1,294 @@
+//! Unit tests for the world's components and systems.
+//!
+//! Lives as a child module so it can poke at `pub(super)` items (the
+//! internal resources, `threshold_for`, etc.) without enlarging the
+//! public API.
+
+use std::sync::Mutex;
+
+use bevy::prelude::*;
+use bevy::state::app::StatesPlugin;
+use tokio::sync::{mpsc, oneshot};
+use uuid::Uuid;
+
+use crate::transport::ecs::{BridgeReceivers, BridgeSenders};
+use crate::transport::state::ServerState;
+use crate::transport::{QuicMessage, SensorType, T1Sender, T2Sender, T3Inbound, T3Sender};
+
+use super::WorldPlugin;
+use super::components::{RawSensorData, SMOOTHED_WINDOW, SmoothedValue, threshold_for};
+use super::resources::SensorRegistry;
+
+/// Build a Bevy app with just enough plugins/resources to run the world
+/// systems against test-owned channels. No QUIC, no tokio runtime.
+fn make_test_app() -> (
+    App,
+    mpsc::Sender<QuicMessage>,
+    mpsc::Sender<QuicMessage>,
+    mpsc::Sender<T3Inbound>,
+) {
+    let (t1_tx, t1_rx) = mpsc::channel::<QuicMessage>(64);
+    let (t2_tx, t2_rx) = mpsc::channel::<QuicMessage>(64);
+    let (t3_tx, t3_rx) = mpsc::channel::<T3Inbound>(64);
+
+    let bridge = BridgeReceivers {
+        t1: Mutex::new(t1_rx),
+        t2: Mutex::new(t2_rx),
+        t3: Mutex::new(t3_rx),
+    };
+    // export_system samples channel depth/capacity from the senders; it
+    // requires the resource even when the test pushes via the raw senders
+    // directly (which is what the rest of the test does).
+    let senders = BridgeSenders {
+        t1: T1Sender::new(t1_tx.clone()),
+        t2: T2Sender::new(t2_tx.clone()),
+        t3: T3Sender::new(t3_tx.clone()),
+    };
+
+    let mut app = App::new();
+    app.add_plugins(MinimalPlugins)
+        .add_plugins(StatesPlugin)
+        .init_state::<ServerState>()
+        .insert_resource(bridge)
+        .insert_resource(senders)
+        .add_plugins(WorldPlugin);
+
+    // Force the state machine into Started so the run_if guard passes.
+    app.world_mut()
+        .resource_mut::<NextState<ServerState>>()
+        .set(ServerState::Started);
+    // Process the state transition before tests push messages.
+    app.update();
+
+    (app, t1_tx, t2_tx, t3_tx)
+}
+
+// ---- ingest_system: entity lifecycle and T3 ack semantics ----
+
+#[test]
+fn ingest_t1_creates_entity_and_writes_raw_data() {
+    let (mut app, t1_tx, _t2_tx, _t3_tx) = make_test_app();
+
+    let device = Uuid::from_u128(0xa1a2_a3a4_a5a6_a7a8_a9aa_abac_adae_afb0);
+    let msg = QuicMessage {
+        device_id: device,
+        sensor_id: 5,
+        raw_value: 3.14,
+        timestamp_us: 1_700_000_000_000_001,
+        sequence_number: 1,
+        sensor_type: SensorType::Temperature.as_u8(),
+    };
+    t1_tx.try_send(msg).expect("channel cap");
+
+    // Tick 1: ingest drains the channel and spawns via Commands.
+    app.update();
+    // Tick 2: Commands have flushed into the archetype.
+    app.update();
+
+    let registry = app.world().resource::<SensorRegistry>();
+    assert_eq!(registry.map.len(), 1);
+
+    let entity = *registry
+        .map
+        .get(&(device, 5))
+        .expect("entity not registered");
+    let data = app
+        .world()
+        .get::<RawSensorData>(entity)
+        .expect("RawSensorData missing");
+    assert_eq!(data.raw_value, 3.14);
+    assert_eq!(data.sequence_number, 1);
+    assert_eq!(data.timestamp_us, 1_700_000_000_000_001);
+}
+
+#[test]
+fn ingest_t1_repeated_messages_update_in_place() {
+    let (mut app, t1_tx, _t2_tx, _t3_tx) = make_test_app();
+    let device = Uuid::new_v4();
+
+    // First reading.
+    t1_tx
+        .try_send(QuicMessage {
+            device_id: device,
+            sensor_id: 0,
+            raw_value: 1.0,
+            timestamp_us: 1,
+            sequence_number: 1,
+            sensor_type: SensorType::Generic.as_u8(),
+        })
+        .unwrap();
+    app.update();
+    app.update();
+
+    // Second reading on the same (device, sensor).
+    t1_tx
+        .try_send(QuicMessage {
+            device_id: device,
+            sensor_id: 0,
+            raw_value: 2.0,
+            timestamp_us: 2,
+            sequence_number: 2,
+            sensor_type: SensorType::Generic.as_u8(),
+        })
+        .unwrap();
+    app.update();
+
+    let registry = app.world().resource::<SensorRegistry>();
+    assert_eq!(registry.map.len(), 1, "should reuse the same entity");
+
+    let entity = *registry.map.get(&(device, 0)).unwrap();
+    let data = app.world().get::<RawSensorData>(entity).unwrap();
+    assert_eq!(data.raw_value, 2.0);
+    assert_eq!(data.sequence_number, 2);
+}
+
+#[test]
+fn ingest_t3_replies_with_current_sensor_value() {
+    let (mut app, t1_tx, _t2_tx, t3_tx) = make_test_app();
+    let device = Uuid::new_v4();
+
+    // Seed a T1 reading so the (device, sensor) entity exists.
+    t1_tx
+        .try_send(QuicMessage {
+            device_id: device,
+            sensor_id: 9,
+            raw_value: 42.0,
+            timestamp_us: 1,
+            sequence_number: 1,
+            sensor_type: SensorType::Temperature.as_u8(),
+        })
+        .unwrap();
+    app.update();
+    app.update();
+
+    // Send a T3 command and capture the ack via the oneshot.
+    let (reply_tx, reply_rx) = oneshot::channel();
+    t3_tx
+        .try_send(T3Inbound {
+            command: QuicMessage {
+                device_id: device,
+                sensor_id: 9,
+                raw_value: 0.0,
+                timestamp_us: 0,
+                sequence_number: 7,
+                sensor_type: SensorType::Temperature.as_u8(),
+            },
+            reply: reply_tx,
+        })
+        .unwrap();
+    app.update();
+
+    let ack = reply_rx
+        .blocking_recv()
+        .expect("ECS handler should have replied");
+    assert_eq!(ack.device_id, device);
+    assert_eq!(ack.sensor_id, 9);
+    assert_eq!(ack.sequence_number, 7, "ack preserves correlation id");
+    assert_eq!(ack.raw_value, 42.0, "ack carries the latest sensor reading");
+    assert_eq!(
+        ack.typ(),
+        SensorType::Temperature,
+        "ack preserves sensor type"
+    );
+    assert!(ack.timestamp_us > 0, "ack stamped with server time");
+}
+
+// ---- SmoothedValue unit tests ----
+
+#[test]
+fn smoothed_value_first_push_sets_mean() {
+    let mut s = SmoothedValue::default();
+    s.push(10.0);
+    assert_eq!(s.mean, 10.0);
+    assert!(!s.above_threshold);
+}
+
+#[test]
+fn smoothed_value_averages_filled_window() {
+    let mut s = SmoothedValue::default();
+    for v in [1.0, 2.0, 3.0, 4.0] {
+        s.push(v);
+    }
+    assert!((s.mean - 2.5).abs() < 1e-9);
+}
+
+#[test]
+fn smoothed_value_rolls_after_window_fills() {
+    let mut s = SmoothedValue::default();
+    for _ in 0..SMOOTHED_WINDOW {
+        s.push(0.0);
+    }
+    assert!((s.mean - 0.0).abs() < 1e-9);
+    for _ in 0..SMOOTHED_WINDOW {
+        s.push(10.0);
+    }
+    assert!((s.mean - 10.0).abs() < 1e-9, "ring should fully roll over");
+}
+
+#[test]
+fn smoothed_value_ignores_nonfinite() {
+    let mut s = SmoothedValue::default();
+    s.push(5.0);
+    let before = s.mean;
+    s.push(f64::NAN);
+    s.push(f64::INFINITY);
+    s.push(f64::NEG_INFINITY);
+    assert_eq!(s.mean, before, "non-finite values should not perturb the mean");
+}
+
+// ---- simulation_system: end-to-end threshold-crossing transition ----
+
+#[test]
+fn simulation_smoothes_and_detects_threshold_crossing() {
+    let (mut app, t1_tx, _t2_tx, _t3_tx) = make_test_app();
+    let device = Uuid::new_v4();
+    let threshold = threshold_for(SensorType::Temperature); // 22.0 °C
+
+    // Below-threshold readings: smoothed mean stays under, no crossing.
+    for seq in 0..SMOOTHED_WINDOW as u32 {
+        t1_tx
+            .try_send(QuicMessage {
+                device_id: device,
+                sensor_id: 0,
+                raw_value: 18.0,
+                timestamp_us: u64::from(seq),
+                sequence_number: seq,
+                sensor_type: SensorType::Temperature.as_u8(),
+            })
+            .unwrap();
+        app.update();
+        app.update();
+    }
+
+    let registry = app.world().resource::<SensorRegistry>();
+    let entity = *registry.map.get(&(device, 0)).unwrap();
+    let smoothed = app
+        .world()
+        .get::<SmoothedValue>(entity)
+        .expect("SmoothedValue should be on every sensor entity");
+    assert!(smoothed.mean < threshold);
+    assert!(!smoothed.above_threshold, "should not have crossed up yet");
+
+    // Above-threshold readings: enough samples to drag the mean above
+    // the threshold (window = 16; pushing 30°C for 16 ticks lands mean ≈ 30).
+    for seq in (SMOOTHED_WINDOW as u32)..(SMOOTHED_WINDOW as u32 * 2) {
+        t1_tx
+            .try_send(QuicMessage {
+                device_id: device,
+                sensor_id: 0,
+                raw_value: 30.0,
+                timestamp_us: u64::from(seq),
+                sequence_number: seq,
+                sensor_type: SensorType::Temperature.as_u8(),
+            })
+            .unwrap();
+        app.update();
+    }
+
+    let smoothed = app.world().get::<SmoothedValue>(entity).unwrap();
+    assert!(smoothed.mean > threshold);
+    assert!(
+        smoothed.above_threshold,
+        "smoothed mean should have crossed up through {threshold}"
+    );
+}