[softmarshmallow]

N3's Rust editor now runs as a static WebAssembly/WebGPU application with the same workspace, semantic actions, menus, and user guide as the native app. Browser capabilities hide unsupported controls, including the local terminal and external settings-file editor.

The host boundary keeps filesystem effects, persistence, GPU setup, clocks, and event scheduling target-specific. Shared rendering retains its revision caches and edit lifecycle; native device limits, scheduling, and presentation policy remain intact. The browser adapter handles pinch/wheel/WebKit gestures and startup focus, and the framework-neutral JavaScript controller supports selected-file loading, downloads, status callbacks, and teardown.

Contributor commands build and serve the baseline, and a dedicated WASM CI lane runs wrapper regressions, warnings-denied Clippy, and the real bindgen build. Native verification remains independent of optional WASM setup. The opt-in Linux software-renderer lane uses one test thread after parallel GPU-backed tests crashed on both committed HEAD and this port; all assertions and exact captures remain enabled. The engineering contract records the shared product model and each host's performance ownership.

Review focus

• src/web.rs, src/web/, and web/n3.js: browser lifecycle, input, settings, and embedding.
• src/render/workspace.rs and src/asset_io/native/: shared rendering and native effect boundaries.
• vendor/egui-winit/N3-PATCH.md: the narrowly scoped WASM compatibility patch and upstream notices.
• docs/architecture/platform-boundaries.md and docs/development.md: ownership, commands, and explicit baseline limits.

Validation

• Native just verify: 939 Rust tests passed, 1 existing ignored test; 81 Python tests and 6 JavaScript wrapper tests passed. Formatting, Clippy, and exact native guide checks passed.
• just ci-macos: native app bundle, ad-hoc signature, metadata/icon checks, and 35 focused integration tests passed.
• just web-verify: wrapper regressions, warnings-denied WASM Clippy, and static WASM/glue build passed.
• Fresh rebuilt browser smoke: WebGPU initialization, Shift+I before any focus switch, viewport deselection, and double-click edit entry passed. Earlier baseline review also covered multi-object selection, held Z/Space, blur cancellation, gestures, file round-tripping, preference synchronization, and teardown.
• Linux just ci checks: formatting, Clippy, tooling, inventory validation, and 938 focused Rust tests passed with the contained serial test policy. All 104 Linux guide images match the previous receipt exactly; the refreshed receipt records only intended prose/manifest changes. just ci-docs check passed all 27 features and 133 exact artifacts. The underlying parallel-test fault remains tracked in TODO.md.

The results above are local verification. Hosted results are reported in this pull request’s checks.

Baseline limits

Requires a secure context and available WebGPU. No local shell/PTY or arbitrary filesystem access; external asset-resource resolution and recovery need later work. Downloads do not establish durable save completion. One editor lifetime per WASM module is supported; an iframe isolates independent lifetimes. Broader browser/device, physical trackpad, touch, IME, and accessibility coverage remains follow-up work.

Large-mesh orbit performance and native/browser profiling are tracked separately in issue #2. The reported slowdown is not yet measured or attributed; this baseline does not establish performance parity.