Technical Design

Boundaries

bin/road-workbench.js owns process startup and creates an import session/workspace.
workbench/server.js owns HTTP routes and session-local files; it continues to call compileInput() for compilation.
workbench/client/index.html and workbench/client/app.js add the upload/bootstrap state only; existing editing panels remain unchanged.
src/compile/compiler.js and src/osm.js remain the source of truth for input validation and OSM processing.

CLI starts a workbench with an optional existing --input for compatibility, or with no input for the new import-first flow.
The browser submits multipart OSM content (bounded by a server upload limit) to a new session/import endpoint.
The server validates the filename/content, creates a unique workspace directory under a configured workbench data root, and writes:
- source.osm
- native-road-overrides.json with the existing empty schema
- native-traffic-signals.json with the existing empty schema
- RoadCompilerInput.json using conservative defaults and workspace-relative output paths
The server calls compileInput() and swaps the active session from the import screen to the existing state/map view.
Existing routes operate against the active session's area object. A failed import/compile removes only the new staging directory and leaves any prior active session untouched.

Area id is derived from a sanitized user-provided name or uploaded basename, with a unique suffix when necessary.
options.edgeLines and options.junctionTemplates use the same shape required by validateInput(); no new compiler options are introduced.
Existing --input RoadCompilerInput.json startup remains supported by adapting it into the same active-session context.
The server binds to localhost as it does today and does not add authentication or remote persistence.

Reject empty/non-XML uploads, oversized bodies, malformed OSM, and compile failures with JSON errors suitable for the browser.
Stage all files before switching the active session; cleanup on failure.
Keep workspace directories recoverable on disk; do not delete an existing user workspace during a new import.

Unit/integration tests for workspace initialization, default input generation, upload size/content validation, and failed-import cleanup.
HTTP smoke test for import -> state -> compile/export using the existing fixture OSM.
Existing compiler and fixture tests remain the regression gate.