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api-docs/adr/ADR-323-native-rust-physics-constrained-pose-refinement.md

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+# ADR-323: Native Rust physics-constrained pose refinement
+
+- **Status**: Proposed
+- **Date**: 2026-08-15
+- **Deciders**: ruv
+- **Owners**: RuView perception and edge runtime maintainers
+- **Tags**: pose, physics, rust, uncertainty, provenance, abstention, edge
+- **Numbering note**: ADR-323 is the next free number in the authoring checkout. Re-run the ADR index/collision check immediately before merge and rename if needed.
+- **Extends**: ADR-020, ADR-027, ADR-079, ADR-101, ADR-135, ADR-145, ADR-150, ADR-273, ADR-279, ADR-282, ADR-295, ADR-296, ADR-297, ADR-298, ADR-302, ADR-303, ADR-304, ADR-305, ADR-306
+- **Supersedes**: None
+
+## Executive decision
+
+RuView will add a clean-room native Rust boundary between RF pose inference and
+semantic publication. It will preserve the immutable RF observation, publish a
+physics assessment, optionally produce a bounded corrected candidate, and
+abstain when required evidence is absent. It must never increase observational
+confidence merely because a pose is physically plausible.
+
+Three independently gated layers are adopted:
+
+1. A deterministic kinematic auditor and bounded covariance-weighted projector
+   using Rust and `nalgebra`.
+2. An optional articulated-body dynamics auditor using `rapier3d`.
+3. A later optional supervised residual model using Burn.
+
+The first production milestone is deterministic audit. It is not a GRIP port,
+not PPO, and not evidence that the current pose observer is production-ready.
+
+## Context
+
+ADR-101's committed Cog emits 17 COCO keypoints as normalized 2D coordinates.
+Its model has no per-joint uncertainty head and publishes a constant confidence.
+The sensing server also contains renderer-oriented EMA and bone clamping. These
+surfaces cannot establish metric 3D physics and can make weak evidence look
+more convincing.
+
+Pose output can violate bone length, floor, velocity, acceleration, and temporal
+continuity constraints. Downstream consumers also cannot reliably distinguish
+observed coordinates from derived correction. The rejected premise is:
+"physically plausible means more likely correct." Plausibility is only a prior;
+many incorrect poses are plausible.
+
+GRIP is architectural inspiration for an observer/controller split, but it
+observes four wearable IMUs and pressure insoles and drives a simulator. RuView
+observes RF, so GRIP weights are not input-compatible. External code, weights,
+simulators, and datasets require independent license review and never enter the
+runtime dependency graph by implication.
+
+## Outcome and actors
+
+For every accepted person track/timestamp, the engine returns exactly one
+`PoseRefinementV1`, including off, timeout, rejection, and abstention paths:
+
+- immutable `PoseObservationV2` content hash;
+- constraint residuals and quality disposition;
+- an optional bounded candidate and an explicit `selected` bit;
+- a typed reason when correction is unavailable;
+- model, calibration, configuration, and optional learned-artifact provenance.
+
+The RF observer owns observations and calibrated uncertainty; tracking owns
+identity stability; physics owns assessment/correction only; the sensing server
+owns deadlines, modes, publication, and rollback; the evidence engine owns
+release evaluation; clients choose raw/both/refined without silent fallback.
+
+## Input and coordinate contract
+
+Metric correction requires a monotonic nanosecond timestamp, session-scoped
+track ID, sequence and sensor epoch, 17 ordered COCO joints in metric X/Y/Z,
+per-joint positive-semidefinite covariance calibrated on held-out data, a
+versioned right-handed Z-up room frame, a normalized upward floor plane, model
+and calibration hashes, ADR-302 trust state, and authenticated/replay-protected
+source provenance.
+
+`Image2d` observations may be audited for image-plane ratios and continuity but
+must never enter 3D projection/dynamics or be called physically corrected.
+Unknown trust, missing calibration, missing uncertainty, stale/non-monotonic
+input, non-finite values, invalid covariance, excessive tracks, and room-bound
+violations fail to raw output with a typed reason.
+
+## Public contracts
+
+`wifi-densepose-core` owns `PoseObservationV2` and `PoseRefinementV1`; no
+duplicate server/Cog contract is permitted. Public output remains COCO17. The
+engine derives pelvis and thorax virtually and never labels them observed.
+
+The raw content hash is deterministic and excludes its own hash field. The
+idempotency key is `(sensor_epoch, sequence, track_id, raw_hash, config_hash)`.
+An exact duplicate returns the cached result; same sequence with different
+content is a replay rejection.
+
+Contact is `hypothesis` unless a measured sensor and its provenance say
+otherwise. Raw, derived, hypothesis, and unknown labels must survive every
+projection.
+
+## Confidence invariant
+
+For upstream calibrated confidence `c_obs`, normalized residual `r`, and
+normalized intervention `i`:
+
+```text
+c_physics = exp(-(beta_r * r + beta_i * i))
+c_effective = min(c_obs, c_obs * c_physics)
+0 <= c_effective <= c_obs <= 1
+```
+
+Only a separately witnessed multimodal fusion contract may increase fused
+confidence.
+
+## Deterministic projector
+
+The default `kinematic` feature has no Rapier, Burn, ONNX, libtorch, Python,
+CUDA, or network dependency. Per bounded iteration it:
+
+1. projects observed parent/child distances toward anonymous track-scoped
+   bone-length posteriors;
+2. applies broad joint/trunk validity checks without an upright prior;
+3. bounds temporal motion and resets derivatives after gaps;
+4. resolves floor penetration only, allowing seated, kneeling, prone, child-
+   scale, mobility-aid, and genuine-fall poses;
+5. recomputes residuals and stops below epsilon.
+
+Initial operator-owned caps are four iterations (hard maximum eight), 0.20 m
+single-joint correction, 0.10 m root correction, 250 ms derivative gap, 500 ms
+track reset, ten known joints, a 100 m metric room bound, a separate 16,384
+image-coordinate audit bound, and a 5 ms one-track Pi 5 p95 gate. Keeping image
+and metric bounds separate prevents legitimate pixel observations from
+weakening the physical room bound. A candidate over either correction cap is
+discarded in full.
+
+Bone posteriors are initialized only from high-confidence frames, anonymous,
+memory-only, track-scoped, and deleted on expiry. Persistent personalization is
+outside this ADR and requires consent/retention/deletion governance.
+
+## Optional dynamics and learned layers
+
+`dynamics` adds a process-owned Rapier humanoid and begins audit-only. Network
+input may never provide Rapier snapshots, bodies, constraints, solver limits,
+or arbitrary geometry. Dynamics approval is independent of kinematic approval.
+
+`learned` uses first-party Burn 0.21 core/NN components without `burn-tch`
+because this workspace already has a different native libtorch link.
+`learned-cpu` adds the ndarray backend. The implemented two-layer GRU uses a
+20-frame history and width 128 to predict bounded residuals, uncertainty,
+foot-contact hypotheses, and abstention. Verified model records can be loaded
+from bytes and executed natively; no trained artifact is shipped or approved.
+The resolved Burn/CubeCL graph declares Rust 1.92, while the workspace file
+pins Rust 1.89 and the authoring host provides Rust 1.91.1.
+`--ignore-rust-version` is diagnostic evidence only: learned activation remains
+blocked until an approved Rust 1.92 release-toolchain change builds it without
+that override. Residuals are hard-clipped to deterministic caps and cannot
+bypass validation or confidence monotonicity. PPO is deferred until measured
+evidence identifies a failure supervised residual learning cannot address.
+
+## Feature boundary
+
+```text
+default = kinematic
+dynamics = rapier3d
+learned = burn-core + burn-nn
+learned-cpu = learned + burn-ndarray
+learned-train = learned + burn-train
+learned-wgpu = learned-train + burn-wgpu
+learned-cuda = learned-train + burn-cuda
+deterministic = rapier3d?/enhanced-determinism
+```
+
+The lockfile is release authority. The learned feature currently requires the
+toolchain supported by Burn/CubeCL's resolved graph; this does not change the
+default edge build.
+
+## Runtime modes and API
+
+Rollout is `OFF -> AUDIT -> SHADOW_CORRECT -> OPT_IN_CORRECT -> DEFAULT_CORRECT`.
+Evidence permits forward transitions; any regression returns immediately to
+audit/off. Correct selection additionally requires authenticated sensor
+identity and replay protection from ADR-305. High model confidence cannot
+override missing source authentication.
+
+Existing pose fields stay unchanged and raw remains the migration default:
+
+```text
+GET /api/v1/pose/current?view=raw
+GET /api/v1/pose/current?view=both
+GET /api/v1/pose/current?view=refined
+```
+
+Refined-only returns HTTP 409 with `pose_refined_unavailable` when no selected
+candidate exists. It never silently returns raw labeled refined.
+
+## Security, privacy, and availability
+
+All frames, model output, geometry, and pre-verification artifacts are
+untrusted. Calibration/config/model artifacts become trusted only after signed,
+hash-addressed verification and atomic activation. Runtime inference performs
+no model retrieval or other network access.
+
+Fixed arrays/caps, bounded iterations, a maximum track count, room geometry
+limits, deadlines, and track expiry constrain denial of service. Timeout drops
+partial refinement, never raw publication. Backpressure retains the newest raw
+frame per track, drops intermediate refinement work, resets derivatives after
+250 ms, and never extrapolates beyond 500 ms.
+
+Metrics contain only allowlisted aggregate scalars: mode/disposition/reason,
+stage latency, iterations, maximum correction, residuals, confidence delta,
+track resets, invalid input, timeout, and raw/refined divergence. They exclude
+joint arrays, body dimensions, room coordinates, CSI, and persistent person
+identifiers. Bone/gait state is memory-only and excluded from logs.
+
+Refined output is not a sole medical, emergency, industrial-safety, or
+autonomous-control source. A real fall is valid state and must never be made
+upright to stabilize a simulator.
+
+## Threat model summary
+
+| Threat | Primary control | Residual risk |
+|---|---|---|
+| Spoofed/replayed sensor | ADR-305 identity, MAC, sequence and replay window; correction gate | Compromised legitimate sensor |
+| Altered model/floor/config | Signed hashes, authenticated configuration, atomic activation | Authorized unsafe configuration |
+| Poisoned data/splits | Immutable manifests, strict split validator, witnessed benchmarks | Subtle label poisoning |
+| Operator repudiation | Append-only witnessed transition with actor/old/new hash/reason | Compromised signer |
+| Biometric/log leakage | Track-local retention and fixed metric allowlist | Aggregate inference |
+| Track/geometry CPU flood | Authentication, cardinality/geometry/allocation/deadline caps | Valid dense-scene overload |
+| Remote mode escalation | Capability-scoped local control plane, deny by default | Compromised operator capability |
+| Derived output relabeled observed | Required schema/provenance and signed event envelope | Malicious downstream stripping |
+
+The implementation review records commit, lockfile hash, Rust toolchain,
+scanner versions, and advisory-feed timestamp.
+
+## Evidence protocol
+
+Evidence levels are L0 deterministic synthetic, L1 public measured replay, L2
+controlled RuView RF plus optical truth, L3 subject/room/hardware/session-
+disjoint RuView, L4 privacy-safe shadow fleet aggregates, and L5 independent
+vertical validation outside this ADR.
+
+No sequence, contiguous take, subject, room, or calibration session may cross
+train/test for the generalization gate. Preprocessing, body priors, and
+uncertainty calibration fit training data only. Reports include raw observer,
+renderer smoothing, audit, deterministic correction, dynamics audit, and
+learned residual on identical observations, plus empty-room, prone/fall,
+missing-joint, and OOD subsets.
+
+Primary metrics are 3D MPJPE, declared-threshold PCK, per-joint error, foot
+slide, floor penetration, jerk, uncertainty calibration, abstention coverage,
+and selective risk. Learned runs use at least five fixed seeds and report mean,
+median, standard deviation, and 95% bootstrap intervals. All frames count;
+selective metrics report risk and coverage.
+
+## Acceptance gates
+
+- **G0 contract**: real metric 3D/covariance output, round-trip raw hash,
+  versioned frame/floor, 2D compatibility, non-stub observer, ADR-298 artifact
+  sanity, and the ADR-079 PCK@20 >=35% gate or adopted successor. The current
+  committed Cog does not pass G0, so correction remains unavailable.
+- **G1 deterministic audit**: property/fuzz tests, deterministic hashes per
+  platform class, 24-hour accelerated replay without panic/growth, Pi 5 p95
+  <=5 ms, and universal confidence monotonicity.
+- **G2 shadow correction**: strict-disjoint measured median MPJPE improvement
+  >=10% with positive 95% CI lower bound; foot slide >=30% and jerk >=25%
+  better; no joint median >5 mm worse; fall/prone sensitivity change <=2 pp;
+  >=95% corrections below 0.10 m; every correction above 0.20 m abstains.
+- **G3 opt-in**: >=30 subjects, 10 rooms, 3 hardware configurations, and 3
+  independent sessions/room; UNKNOWN never selected; confidence monotonic;
+  live disable; REST/WebSocket/MQTT/Home Assistant/replay compatibility.
+- **G4 default visualization only**: 30 shadow days under 0.1% timeout/internal
+  error, no open severity 1/2 incidents, and gates still valid for current
+  model/calibration.
+
+Dynamics and learned engines each repeat G2-G4; approval is not inherited.
+
+## Testing and completion evidence
+
+Unit/property/fuzz/integration/security coverage maps to requirements R1-R13:
+raw hash, confidence, modes, malformed/stale/frame/covariance input, caps and
+deadlines, provenance, dependency graph, pose diversity/fall preservation,
+strict splits, fail-to-raw faults, no network capability, and authenticated
+source/replay selection.
+
+Release commands include focused core/physics tests, default/dynamics/learned
+feature checks, format/clippy, benches, `cargo deny`, `cargo audit`, strict split
+verification, and golden replay verification. Completion also requires JSON
+schemas, measured Pi 5/x86 rows, strict manifest hashes, raw/refined metrics,
+SBOM/license report, rollback drill, and residual-risk owners. Missing measured
+or operational evidence leaves status Proposed and runtime in audit.
+
+## Rollback
+
+Rollback is an authenticated mode transition to audit/off, not a binary
+downgrade. Stop selection immediately, keep raw publication and disposition
+records, discard track state, and retain only aggregate incident metrics plus
+signed configuration history. Failed artifact activation leaves the previous
+engine atomically active. Additive schemas remain; refined-only callers receive
+the typed unavailable response.
+
+## Consequences
+
+### Positive
+
+- Explicit anti-hallucination and provenance boundary after RF inference.
+- Reusable native Rust consistency primitive with measurable abstention.
+- Python/CUDA remain absent from the production default.
+- Cross-modal teacher data remains possible without wearable runtime inputs.
+
+### Negative
+
+- Full value requires a real metric 3D observer and calibrated uncertainty.
+- Stateful tracks add latency/memory; optional backends add supply-chain surface.
+- A constrained but wrong pose can look more credible.
+- Strict data collection costs more than the software implementation.
+
+### Neutral
+
+- This ADR does not improve RF observability or current weight evidence.
+- Existing 2D consumers continue to function.
+
+## Implementation phases
+
+P0 contracts/schemas; P1 deterministic audit; P2 bounded shadow correction; P3
+server/Cog publication and evidence ledger; P4 Rapier audit; P5 Burn residual
+training/inference. Code may land ahead of evidence, but runtime authority
+advances only through the gates above.
+
+## Implementation status at proposal
+
+- P0-P3 are implemented on this branch: canonical contracts, strict schemas,
+  deterministic audit/projection, authenticated correction receipts,
+  idempotency, bounded track state, latest-frame backpressure, additive HTTP
+  and WebSocket publication, live legacy-2D audit, privacy-safe metrics, golden
+  replay, and strict-split checks.
+- P4 is implemented as an optional persistent per-track Rapier dynamics auditor
+  and remains audit-only pending independent G2-G4 evidence.
+- P5 inference architecture, artifact verification, serialization, and native
+  CPU execution are implemented. Training data, a signed trained artifact, and
+  G2-G4 accuracy/calibration evidence do not exist, so the layer has no runtime
+  selection authority. Its resolved Rust 1.92 requirement is also an explicit
+  activation blocker on the current Rust 1.91.1 release host.
+- The live Cog honestly emits `Image2d`, degraded trust, and uncalibrated
+  uncertainty. It can be audited but cannot be selected for 3D correction.
+  G0 therefore remains open until an independently released metric-3D observer
+  with calibrated covariance is integrated.
+- Local x86 latency and synthetic contract checks are recorded in the append-
+  only evidence ledger. Pi 5 measurements, 24-hour replay, 100-million-case
+  fuzzing, held-out RF/optical accuracy, fleet shadowing, and vertical safety
+  validation remain release evidence gates rather than software claims.
+
+## References
+
+- [GRIP project](https://ryosukehori.github.io/grip-project/)
+- [GRIP paper (arXiv:2603.16233)](https://arxiv.org/abs/2603.16233)
+- [Rapier documentation](https://docs.rs/rapier3d/)
+- [Burn documentation](https://docs.rs/burn/0.21.0/burn/)
+- [ADR-020](./ADR-020-rust-ruvector-ai-model-migration.md)
+- [ADR-079](./ADR-079-camera-ground-truth-training.md)
+- [ADR-101](./ADR-101-pose-estimation-cog.md)
+- [ADR-150](./ADR-150-rf-foundation-encoder.md)
+- [ADR-273](./ADR-273-unified-rf-spatial-world-model.md)
+- [ADR-279](./ADR-279-native-rf-frame-contract.md)
+- [ADR-298](./ADR-298-model-release-sanity-gates.md)
+- [ADR-302](./ADR-302-out-of-distribution-detection.md)
+- [ADR-303](./ADR-303-ground-truth-synchronization.md)
+- [ADR-304](./ADR-304-evidence-engine.md)
+- [ADR-305](./ADR-305-authenticated-sensor-identity.md)
+- [ADR-306](./ADR-306-canonical-spatial-ontology.md)

api-docs/adr/README.md

@@ -179,6 +179,7 @@ Statuses: **Proposed** (under discussion), **Accepted** (approved and/or impleme
 | [ADR-319](ADR-319-witness-chain.md) | Witness chain — staged, signed epistemic envelope | Accepted (phase 1) |
 | [ADR-320](ADR-320-sensor-hal.md) | RuView sensor HAL — abstract all sensing hardware to one Observation type | Proposed (phase 2) |
 | [ADR-321](ADR-321-decision-policy-action-authorization.md) | Decision policy — action authorization conditioned on certificate class, freshness, uncertainty, evidence | Accepted (phase 1) |
+| [ADR-323](ADR-323-native-rust-physics-constrained-pose-refinement.md) | Native Rust physics-constrained pose refinement | Proposed |
 
 ---