History Server intake and recovery

How the drop zone fetches a run from a History Server and recovers from errors.

DropZone keeps the History Server disclosure, Base URL, Application ID, optional Attempt ID, validation/touched state, recoverable SHS error, and local-server reachability in mounted React state rather than Zustand. The local browser-first path is the default: Choose file loads a single event log, while Choose rolling-log folder accepts only an eventlog_v2_* directory and directs a rejected folder back to the file picker.

The three text fields also mirror to window.localStorage (shuffle-works-shs-base-url/-app-id/-attempt-id), read back as each useState's initializer, so a returning visitor's values survive a reload; storage access is wrapped in try/catch and silently ignored when unavailable, matching store.ts's initialTheme/initialWidgetDensity pattern. Both this disclosure's toggle and the Other sources toggle show a chevron (ChevronDownIcon/ChevronUpIcon) that flips with aria-expanded, so the open/closed state has a visual signal beyond the attribute.

On mount (skipped in compact mode), DropZone probes reachability with an empty, short-timeout fetch('/shs-proxy'): a 400 means validateShsRequest (packages/core/src/proxy.js) rejected the empty request synchronously, which only happens when a local server is actually routing that path, so it flips shsReachable to true. A network error, a 404 (static deploy, no such route), or a probe still in flight all leave shsReachable at its default false, so nothing changes on screen after paint unless the server is confirmed present. When shsReachable is true, the landing page shows a neutral callout above the Other sources disclosure pointing the user at it; the disclosure itself doesn't move or auto-expand.

The collapsed Fetch from Spark History Server disclosure requires local-server mode, a reachable History Server, and a supported base application ID: application_<timestamp>_<id>, local-<timestamp>, app-<identifier>, spark-<identifier> or driver-<number> (APP_ID_PATTERNS in packages/core/src/shs-request.js). packages/core/src/shs-request.js trims and validates the three request fields, accepts only absolute credential-free http:/https: base URLs without a query or fragment, preserves a reverse-proxy path prefix, and canonicalizes the base URL to one trailing slash. The optional attempt is a separate path-safe identifier; neither identifier can contain a path separator. The shared helper builds the encoded /shs-proxy request and the encoded api/v1/applications/<app>[/<attempt>]/logs upstream path from that normalized object only.

The optional Node server is loopback-only: a narrow CORS proxy, not a general or hosted proxy. It validates the same request contract, sends no credentials, follows no upstream redirects, and returns only stable safe error codes. It never forwards upstream response text, status details, locations, or credentials to the browser.

Routing preserves the recovery boundary: local file and folder failures use the page-level error route. A typed SHS failure instead resets the model to idle and returns to the still-mounted, expanded History Server disclosure, which retains its values and shows safe recovery guidance along with local file intake. During an SHS parse, the mounted intake shows progress in place; successful completion follows the normal dashboard route.