codegraph/ui

ui/ — the codegraph ui viewer

The browser reader for an indexed project: Svelte 5 + Vite, built as static files and served by the CLI over loopback. An npm workspace of the engine, so npm ci at the repo root installs its toolchain; nothing here is a runtime dependency of the engine and nothing here is published to npm on its own.

Design spec (every token, size and measurement): ../docs/design/codegraph-ui-design-spec.md.

Build

npm run build          # from the repo root: tsc -> copy-assets -> this app
npm run build:ui       # just this app, plus the dist assertion
npm run dev -w ui      # Vite dev server on 127.0.0.1:5174
npm run check -w ui    # svelte-check

npm run build emits dist/viewer/ (index.html + hashed assets). scripts/check-ui-build.mjs then asserts the tree is complete, so a broken UI build fails the release instead of shipping a CLI that serves a 404. The same check runs again in scripts/build-bundle.sh (after the bundle stage copies dist) and in scripts/pack-npm.sh (after each archive is unpacked).

Why dist/viewer and not dist/ui

src/ui/ is the engine's terminal UI (shimmer progress and its worker) and tsc compiles it to dist/ui/. Pointing Vite there deletes those modules — the CLI then dies at startup with Cannot find module '../ui/shimmer-progress' — and would also leave the static server handing out compiled engine internals. check-ui-build.mjs re-asserts the compiled engine is intact after every UI build so that mistake cannot land twice.

Layout

src/
  main.ts                 fonts + tokens, mounts App into index.html's #app
  app.css                 design tokens (light/dark), reset, shell grid
  App.svelte              top bar / trail bar / main, global keys
  lib/router.svelte.ts    hash router: #/s/<id>, #/file/<path>, #/map, #/flow, #/entry
  lib/trail.svelte.ts     the walked path; mirrored into the `t` query param
  lib/kinds.ts            kind glyph letters
  lib/map-model.ts        the Map's deterministic layered layout (pure)
  lib/flow-model.ts       the Flow strip's card/link geometry + the end cap — a DAG (pure)
  lib/filecode-model.ts   the whole-file view: fixed line height, arcs, paging (pure)
  lib/entry-model.ts      the entry-points panel: rows, file groups, flow arming (pure)
  lib/export-svg.ts       the Flow strip and the Map as a standalone SVG (pure)
  lib/export-image.ts     rasterising that SVG to PNG, clipboard and download
  lib/live.svelte.ts      /api/events: two counters every screen refreshes from
  lib/toast.svelte.ts     the one transient note ("Index updated · reloaded")
  components/             TopBar, TrailBar, KindGlyph, DriftBanner, Toast, ExportButtons, map/, flow/, symbol/, file/, entry/
  views/                  one component per route

Fonts (Archivo Variable, IBM Plex Mono) are vendored through @fontsource* and emitted into dist/viewer/assets: a local reader must work offline and must not announce the project to a font CDN.

Export

The Flow strip's header and the Map's side panel carry Copy image (a PNG on the clipboard) and Download SVG (a file for a README). Both render the light theme whatever the viewer is set to — an image is read on somebody else's screen — with 24px of paper around the drawing, a caption naming the path or the root, and a "CodeGraph" mark in the corner.

export-svg.ts serialises the layout object; it does not scrape the DOM. buildFlowLayout and buildMapLayout already compute every rectangle, port and curve before a component renders, so the image and the screen come from one piece of arithmetic and cannot disagree — and the exporter is a pure function that a test can run with no browser at all. The output is presentation-only SVG (no script, no foreignObject, no external reference), which is what GitHub will render in a README.

Fonts travel as font-family stacks rather than embedded bytes. An SVG loaded as an image may not fetch a webfont, so a raster falls back to the platform's own monospace; every fallback in the stack advances at ~0.6em like IBM Plex Mono, so the code grid survives and only the letterforms change.

Routes

hash	view
#/	nothing selected
#/s/<id>?hl=<line>&t=<trail>	symbol view
#/file/<path>?hl=<line>	file view — outline in source order
#/file/<path>?src=1	file view — the whole file's source, with ports and call arcs
#/map?root=&depth=&tests=1	module map
#/flow?from=&to=	flow strip — the call path between two symbols
#/flow?symbols=a,b,c	flow strip — codegraph_explore's own question
#/flow?t=<trail>	flow strip — the trail you walked, read as a flow
#/entry	entry points — routes, files that run something, tests, hubs

Entry points

#/entry draws /api/entrypoints as file groups, reusing the Symbol view's .filegroup / .row shapes rather than inventing a second visual language for "a list of code, grouped by where it lives". Three things about it are decisions, not accidents:

• Routes group by where the URL is REGISTERED, not where it is served. A router file is the shape a reader already has in mind; handlers scatter across a package. The payload carries both, and the row's meta line names the handler and its file:line.
• A row offers a flow only if it names a callable symbol. /api/flow searches the graph by NAME, and a file has none the path finder can look up — so route and hub rows carry a Flow › chip and file and test rows do not. A chip that always failed would be worse than no chip.
• No empty Routes box. A project with fewer than three resolvable routes is not a routed app, and the section is absent rather than empty; the panel falls back to the files that run something and the tests that exercise them.

buildEntryPanel is pure and keeps panel.rows exactly equal to the sections it draws, the same identity the search palette rests its keyboard on.

Where the graph stops

A flow that does not reach everything it was asked about carries a boundary on the wire, and buildFlowLayout turns it into an extra 240px node one column past the symbol the path stopped at, joined by a dotted 2 4 link labelled "end of static path" that deliberately has no arrowhead — an arrow would point at a continuation, and the absence of one is the finding.

Two rules hold it together:

• The cap's height is arithmetic, like a card's. endCapText() builds every sentence the cap shows and endCapHeight() measures them; the component then renders exactly what was measured. Change the wording in one and the other moves with it — they are the same function read twice.
• One cap per stopping symbol, not per flow. Two paths that run out at the same place ran out for the same reason, and two caps side by side would read as two different findings.

The verdict itself is not computed here or in the server: it is findDynamicBoundaries in src/graph/dynamic-boundary-report.ts, the same detector codegraph_explore announces boundaries with.

Live updates

The viewer never polls. lib/live.svelte.ts holds one EventSource on /api/events for the life of the page and exposes two counters:

• indexTick — the graph moved (somebody synced). Every screen refetches: a rail is an answer about the whole graph, and a symbol gains a caller when some other file is edited, so filtering by the focused file would leave the rails quietly wrong. One request per sync.
• diskTick — source files changed on disk and the index has not caught up. Only the screen showing one of those files reacts, and what it does is draw a drift banner.

liveRefresh(file, refresh) is the three lines of bookkeeping that turns a counter into a single call; the Map and the Flow strip instead read live.indexTick straight inside the effect that already fetches them.

Reconnection is ours, not EventSource's: each failure closes the stream and schedules ONE retry on a backoff that ends after eight attempts (~90 s), at which point the top bar says "Not live" and nothing more is requested until the tab is focused again. A degraded event — the server's watcher gave up — is shown the same way and never answered with a poll.

Node ids and file paths are encoded per slash-separated segment, so #/file/src/mcp/tools.ts stays readable and still round-trips a segment containing a reserved character. Build hashes with symbolHref() / fileHref() / mapHref() / flowHref() rather than by hand.