Echelon Architecture Alignment Brief

## Purpose - Align the new Rust-based performance instrument plan with existing Computational Studio capabilities and Episode 1 assets before parallel implementation starts. - Document reuse targets, gaps, and decision points so engine, AI, UI, and ops teams can execute in lockstep. ## Product Scope & Surface - Target the **Standalone Rust DAW** as the primary experience to deliver the differentiated real-time control surface, while preserving a clear integration path for the **Serato/Ableton bridge** as outlined in the product tiers (`Echelon.md` lines 190-206). - Maintain compatibility hooks for the future **cloud rehearsal companion** so nightly training loops can progress without blocking the on-device release (`Echelon.md` lines 207-214, 236-239). - Frame the user journey around rehearsal → preparation → live performance → computational rehearsal so feature priorities reflect the promised flow (`Echelon.md` lines 219-238). ## Workspace Layout (Rust) - `apps/studio` orchestrates threads and runtime wiring. - Core crates: `audio-engine`, `scheduler`, `ui-shell`, `control-bus`, `media`, `midi-osc`, `dsp-utils`, `link-clock`, `ts-shift`, `shmem-ipc`, `viz`. - `xtask` hosts developer tooling; `docs/` captures plans/to-dos; configs live under `apps/studio/src/config`. - Sidecars will reside in `sidecars/` and are bridged via `shmem-ipc` once implemented. ## Visualization Concept (crates/viz) - Follow `docs/visualize.md` to render the latent manifold, beat phase, solver residual, slow attractor, and limb energies without disturbing the audio thread. - Default projector weights live at `configs/visualization/projector.json`; override via `ECHELON_VIZ_PROJECTOR`. - Extend `control-bus` with `FastState`, `SlowState`, and `Telemetry` snapshots; scheduler publishes decimated frames to a dedicated ring buffered for the viz subscriber. - Provide both embedded (egui widget) and standalone window modes so Studio can ship headless or with an instrument-grade monitor. ## Current Assets & Reuse - Computational Studio already hits real-time fusion, audio bridge, and telemetry targets (<10 ms pipeline, multi-device sensor handling, OSC/Ableton integration) that form the backbone for Echelon control and monitoring (`computational-studio/README.md` lines 9-99, 121-125). - Episode 1 delivered 35+ modules, logging/replay infrastructure, and the DELL motion interpreter that can be wrapped rather than rewritten (`EPISODE1_OVERVIEW.py` lines 27-84, 59-62, 74-82). - The DJ Agent work provides mature safety policies, action scheduling, and automation tests that should be ported into Rust to accelerate quantization and deck protection (`COMPLETE_IMPLEMENTATION_SUMMARY.txt` lines 21-49, 63-74, 144-149).