Glossary#

Bifacial component — the core primitive: one definition projecting a view (humans), a resource (agents) and tools (both). Named after Janus.

Island — a bifacial component mounted in a page. Server-rendered, then resumed (not hydrated) on first interaction.

Resource — the agent-readable projection of a component's state: ui://cart, store://theme. Plain JSON, schema-described.

Tool — an intent or api() as agents see it: name, description, JSON Schema input, guard.

Intent — a named, schema-typed action on a component. The unit of interactivity and the tool unit. The only place state mutates.

Guard — auto / confirm / forbidden: who may invoke a tool and whether a human approves first. Resolved per request context.

Proposal — the suspended execution produced when an agent hits a confirm guard. A human approves (runs exactly once) or rejects.

Manifest — the machine-readable contract of a mounted page: resources, tools, guards, events. Generated from code; served at /_janux/manifest.

Source — declarative async data-in (query + refresh policy). Loads server-side before render; its value travels in the snapshot.

Effect — a named side effect with a declared trigger (when) and optional debounce/cleanup.

Store — a bifacial component without a view; shared state as store://name, mutable only through its own intents.

Snapshot — the serialized { state, sources } a page embeds per island; what the client resumes from.

Resume (structural resumability) — booting an island from its snapshot without re-running or replaying anything. Zero component code until first interaction.

Bridge — window.janux: read / call / approve / settled / subscribe / manifest. The gui-agent surface of the page.

settled() — the quiescence primitive: resolves when no source, effect, debounce or in-flight intent remains. Kills sleep(500).

Origin — who's invoking: human (clicks, forms — most privileged) or agent (bridge, copilot, x-janux-origin).

ctx — the per-request context built by src/ctx.ts (auth, tenant, role). Flows into apis, sources, guards and routes; agents act under the end user's ctx.

Foreign island — a component from another runtime (React today) mounted with foreign(): a real embedded root inside a Janux island. Projects a view only — no resource, no tools, until you wrap it.

Harness — the opt-in agent runtime around the loop: defineAgent({ harness }) adds thread memory, guardrail processors, rate limits and identity resolution. Durable workflows, attachments and outbound MCP clients live alongside it.

WebMCP — the browser standard for exposing a page's tools to agents (document.modelContext). boot() registers every manifest tool with it, sanitizing names (counter.inc → counter_inc), and polyfills it where it's missing.

Hosted MCP endpoint — /_janux/mcp: a real, stateless MCP server generated from the app, so an external client (Claude Code, CI, any agent) drives the same tools by URL.

llms.txt — an opt-in markdown index at /llms.txt: every page (dynamic routes enumerated by staticParams) and every server tool, with approval-gated ones annotated.

Query cache — useQuery / mutation / QueryClient from janux/query: server state with staleness, background revalidation and optimistic rollback. Component state stays in schema.

urlState — one query-string param bound to a schema-typed signal. The URL is the source of truth, so filters and tabs are deep-linkable and back/forward-correct — and query-only changes never re-render the page.

Matcher — a named predicate behind a typed route segment ([id=int]), built in or exported from src/matchers.ts.

Zero-JS page — a route mounting no islands: the HTML document contains no <script> at all.