codegraph/ui/README.md

ui/ — the codegraph ui viewer, and @colbymchenry/codegraph-ui

One source tree, two builds.

• The app — the browser reader for an indexed project: Svelte 5 + Vite, built as static files into ../dist/viewer and served by the CLI over loopback.
• The library — the same components, packaged with svelte-package into dist/ as @colbymchenry/codegraph-ui, so a host (CodeGraph Pro) renders the Symbol view, the Flow strip and the Map over its own graph reads.

They are one tree on purpose. A forked component is a second answer to the same question about the same graph, and sooner or later the two get quoted against each other in a review.

An npm workspace of the engine, so npm ci at the repo root installs the toolchain for both.

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 the app, plus the dist assertion
npm run build:lib      # the LIBRARY: svelte-package -> ui/dist, plus its checks
npm run dev -w ui      # Vite dev server on 127.0.0.1:5174
npm run check -w ui    # svelte-check

build:lib is deliberately not part of npm run build: the CLI does not need it, and a release that fails because a component library would not compile is a release that failed for the wrong reason.

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.

@colbymchenry/codegraph-ui

<script lang="ts">
  import { CodegraphUi, SymbolView, FlowStrip, ArchitectureMap }
    from '@colbymchenry/codegraph-ui';
  import '@colbymchenry/codegraph-ui/theme.css';
</script>

<CodegraphUi adapter={myAdapter} nav={myNavigation}>
  <SymbolView id={symbolId} line={null} />
</CodegraphUi>

Exports: SymbolView, FlowStrip, ArchitectureMap, FileView, FileSourceView, EntryPointsView, DeadCodeView, TypeHierarchy, TrailBar, SavedTrails, SearchPalette, PalettePanel, PaletteRows, DriftBanner, KindGlyph, ExportButtons, CodegraphUi — plus every pure model function the screens are built from (buildCalleeRail, buildFlowLayout, buildMapLayout, buildHierarchyModel, tokensByLine, …) and the Wire* types an adapter answers in.

TypeHierarchy is the one screen that takes its data as a prop rather than asking the adapter: it is part of SymbolView's payload (/api/node's hierarchy), so a host that already holds a WireSymbolPayload can render the tree on its own without a second read.

The adapter is the only way data arrives

interface GraphAdapter {
  stats(signal?): Promise<WireStats>;
  search(query, opts?, signal?): Promise<WireSearch>;
  node(id, signal?): Promise<WireSymbolPayload>;
  nodes(ids, signal?): Promise<WireNodeRefs>;
  source(request, signal?): Promise<WireSource>;
  file(path, signal?): Promise<WireFilePayload>;
  fileCode(path, signal?): Promise<WireFileCodePayload>;
  flow(request, signal?): Promise<WireFlowPayload>;
  map(request?, signal?): Promise<WireMapPayload>;
  routes(request?, signal?): Promise<WireRoutes>;
  entryPoints(request?, signal?): Promise<WireEntryPoints>;
  deadCode(request?, signal?): Promise<WireDeadCode>;
  trails(signal?): Promise<WireTrails>;

  // The only mutating pair, and the only optional methods besides `events`.
  saveTrail?(request, signal?): Promise<WireTrails>;
  deleteTrail?(id, signal?): Promise<WireTrails>;
  events?(handlers): () => void;   // optional: the live channel
}

The shapes are exactly what src/ui-server/api/ serialises, and they live in src/lib/wire.ts — no imports, no runtime — so a host can depend on the vocabulary without depending on the viewer. The default implementation, createHttpAdapter(), is the loopback JSON API; a host that already holds the index implements the same thirteen required methods against its own reads and never makes an HTTP request. scripts/check-ui-package.mjs asserts that no module in the built package but lib/adapter.js touches the network, because a screen that reached past the adapter would be a screen that ignored the host.

events is optional. Omit it and nothing connects and nothing polls; a host that learns about a sync some other way calls live.signal('index') instead, which is the same code path the stream uses.

saveTrail / deleteTrail are optional for a different reason: they are the only methods in the interface that CHANGE anything, and a host must be able to render the reader without inheriting a write it never asked for. Omit them and TrailBar grows no Save button and SavedTrails says the host does not store them — the same thing it does when trails() answers readOnly: true, which is how a host that can store them declines a particular project. trails() itself is required: a host with nowhere to keep them answers an empty read-only list, so the screen is explained rather than silently missing.

Three things that will bite

1. Import theme.css once. Every component paints from the design tokens. Override any variable on a narrower selector — including on a container, since custom properties inherit; <CodegraphUi theme="light"> uses exactly that to put a light reader inside a dark application.
2. The adapter and the navigation driver are module-level, not context. The pure model modules are plain TypeScript and cannot read a component's context, so one page reads one project. <CodegraphUi> installs them during initialisation, once — swapping projects means re-mounting the subtree ({#key project}), not swapping the prop.
3. Geometry is not themable. 34px rail rows, the 300/320px rails, the 20px code line: the Symbol view measures these against each other to put a callee row beside the line that calls it. Colour and type are yours.

Navigation

Every link the components build goes through a NavigationDriver (src/lib/navigation.ts). The default is the viewer's own hash space (#/s/<id>); a host installs one that addresses its app instead, and the rails, breadcrumbs, chips and cards follow. They are hrefs rather than click handlers because middle-click, cmd-click and "copy link address" are how people read code.

The app's half — parsing the hash, holding the live route — is src/lib/router.svelte.ts, which attaches hashchange/popstate listeners at module scope and is therefore pruned out of the published package. Nothing a host imports may drag a hash router into its application.

Versioning and publishing

The package is versioned with the engine (scripts/sync-ui-version.mjs runs on every build:lib): @colbymchenry/codegraph-ui@X.Y.Z is the reader for codegraph@X.Y.Z, because the payload shapes are versioned with the binary that serves them.

It is prepared, not published. "private": true in package.json is the guard — npm refuses to publish it — and scripts/pack-npm.sh only builds the tarball when CODEGRAPH_PACK_UI=1, into release/npm-ui/ (never release/npm/, whose codegraph-* glob the release workflow publishes). Publishing is the maintainer's call and takes two deliberate edits.

Layout

src/
  index.ts                the LIBRARY's entry — everything the package exports
  main.ts                 fonts + tokens, mounts App into index.html's #app
  app.css                 the app's reset, shell grid and primitives
  lib/theme.css           the design tokens (light/dark) + the Svelte Flow map
  lib/adapter.ts          GraphAdapter, createHttpAdapter, the registry
  lib/wire.ts             every Wire* payload shape — types only, no runtime
  lib/api.ts              the screens' calls, one line each, over the adapter
  lib/navigation.ts       href builders + navigate, behind a driver
  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/trails.svelte.ts    saved trails: one shared fetch, and the two writes
  lib/trails-model.ts     what a saved trail's row says, incl. its decay (pure)
  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, SavedTrails, 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.

The type hierarchy

A class, interface, struct, trait or enum carries a hierarchy on its /api/node payload: ancestors up, subtypes down, and the fan an interface call dispatches into. buildHierarchyModel turns it into a tree whose geometry is arithmetic — 24px rows, 22px of indent per descendant level, orthogonal 1px connectors computed from those two numbers. Nothing is measured; the same payload always draws the same picture.

The details worth knowing before changing it:

• extends is solid, implements dashed 4 3, a synthesized edge dashed 6 3 with a via <mechanism> pill. In Go, System satisfies Clock without either file naming the other and the edge exists only because the resolver made it — the block says so rather than drawing it like a parse.
• Overrides on the members outline are a NAME match, not an overrides edge (nothing in the engine emits one). They are matched against the nearest ancestor that declares the name and are blind to signatures, and the tooltip says which claim was actually checked.
• The fold trims the deepest end, because the walk is breadth-first: a reader looking at an interface gets every direct implementation before any subclass of one appears at all.

The walk is not computed here or in the server: it is buildTypeHierarchy in src/graph/type-hierarchy.ts, whose countImplementers is also the number codegraph_explore prints when it announces an interface dispatch — so "N types implement X" is the same N wherever you read it.

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.