Architecture

A short map. The authoritative, line-anchored design document is docs/architecture.md in the repository; this page summarises the shape and points at where behaviour actually lives.

Three layers, one direction of dependency

src/ (React + TypeScript, ~124 modules)      the UI and the pure analysis modules
  │  Tauri IPC (invoke) — the single seam is src/bridge.ts
  ▼
src-tauri/ (Tauri 2 shell: main.rs, mcp.rs, tuning.rs)   commands, MCP server, tuning
  │  depends on ↓, never the reverse
  ▼
crates/profile-core/ (Rust: import + analysis)    the one analysis core

• crates/profile-core does all importing and analysis (≈45 files). It also builds the headless importer CLI (cargo run -p profile-core -- …) and backs the MCP server. The GUI, CLI and MCP all go through one cancellable, fingerprinted import router (project::load_input wrapping import::load_capture_options), so they accept the same inputs (including .rocprof-att).
• src-tauri registers 50 Tauri commands (generate_handler! at main.rs:1563 — 39 in main.rs, 7 in mcp.rs, 4 in tuning.rs), hosts the MCP server, and owns the kernel-tuning subsystem. Its capability set is deliberately tiny: core:default + dialog:allow-open, with a strict CSP and only the dialog plugin. Every file save/pick goes through Rust.
• src is React with no store library: plain hooks in one large App component, four Contexts, a useRef per-capture "shadow store", and window CustomEvents for cross-surface IPC. src/bridge.ts is the single IPC seam and the only place the browser-preview fallback is decided. The frontend's pure .ts modules carry the analysis math and have sibling Vitest tests; the .tsx components are thin and are covered through Playwright.

Two things to know

• The frontend analysis modules are shared with the backend. build.rs bundles several src/* modules into a Node CLI (mcp-analysis.cjs) so the MCP capture_analyze tool runs the same code as the webview. That is why Node.js is both a build-time and (for that one tool) a runtime requirement, and why editing src/ triggers a Rust rebuild.
• The decoder ZIP is resolved at startup. The desktop app loads decoder-python.zip from Tauri's resource directory during .setup(...); a missing resource aborts startup. See Installation.

Paging and budgets

Large captures are transferred to the UI in pages (catalog/observation pages, 4096 rows / 4 MiB each) and bounded wave queries load each selected wave fully before filtering by the viewport. The app pages timeline lanes and ISA rows; it is not an indexed out-of-core viewer, though an on-disk token index exists and is preferred when available. All the caps are in Limits & caveats.

Where behaviour lives (quick index)

You want to change…	Look at
How a format is imported	crates/profile-core/src/import.rs (and project.rs for the GUI path)
A Tauri command	src-tauri/src/main.rs, registered at main.rs:1563
The MCP tool surface	src-tauri/src/mcp.rs (fn tools()), and MCP mode
Kernel tuning	src-tauri/src/tuning.rs, tuning_worker.py
A view or analysis	a pure src/<name>.ts module (+ its .test.ts) and a src/components/*.tsx panel