Implement CE-WP-0003 T01-T08: form binding + visual guide overlay

T01 EvidenceLink/EvidenceSet types
  - src/shared/evidence-link.ts: status (§2.4), relation (§2.5), target
  - src/shared/evidence-set.ts: ordered group + activeEvidenceItemId
  - enum-conformance test parses SharedContracts.md and asserts the
    runtime lists match exactly

T02 Binding service + in-memory link repo + active-state machine
  - src/binder/repos/in-memory-links.ts: Map-backed EvidenceLinkRepository
  - src/binder/services/bindings.ts: link/unlink/list/update/setActive
    emitting §4 EvidenceLinkCreated / EvidenceLinkUpdated /
    EvidenceItemActivated
  - src/binder/state/active.ts: (target, evidence, annotation) reducer
    + ActiveStateProvider + useActiveState hook
  - extended engine/events/types.ts with EvidenceLinkCreated,
    EvidenceLinkUpdated, FormFieldActivated payloads

T03 Rect registry (SharedContracts §7 — contract FROZEN)
  - src/binder/visual-guide/rect-registry.ts: register/getRect/subscribe
    + invalidate + getVersion for useSyncExternalStore
  - events.ts: scroll/resize/focus pumps via window + ResizeObserver +
    IntersectionObserver, rAF-throttled
  - react-hooks.ts: RectRegistryProvider, useRegisterRect(kind,id,ref),
    useRectRegistryVersion

T04 Form schema + renderer
  - src/app/forms/demo-schema.ts: text/textarea/date minimal schema
  - src/binder/FormRenderer.tsx: renders schema, each field registers
    as rect kind="field"; active field gets aria-current="true"
  - placed in binder/ (not work/) because work cannot import binder per
    DependencyMap.md §2 and the renderer needs the rect-registry hook;
    workplan T04 was amended in-place to document this

T05 Side-by-side Forms layout + click-to-link
  - src/app/forms/FormsApp.tsx + src/app/App.tsx top-bar router with
    hash route #/forms/demo
  - BinderProvider mounted at app root so links survive tab switching
  - stage-evidence-then-click-field linking interaction with banner
    + per-field link-count chip

T06 Active-evidence cycling
  - src/app/forms/ActiveEvidenceChips.tsx: chips per active target,
    Tab cycles natively, first chip auto-activates on field focus,
    each chip registers as rect kind="evidence-card"
  - ScrollBridge in FormsApp wires activeAnnotationId to viewer scroll
  - EvidenceSidebar + EvidenceStrip highlight the active item via the
    new useLastActivatedEvidence hook in work/EngineContext

T07 SVG visual-guide overlay
  - src/binder/visual-guide/Overlay.tsx: single fixed-positioned SVG,
    draws field→card and card→highlight bezier curves for the active
    triple, rAF-throttled via the registry
  - src/anchor exposes getHighlightClientRects(annotationId); the
    spike viewer wraps highlights in [data-highlight-id] so the helper
    can locate them
  - src/app/forms/HighlightRectBridge.tsx: registers the active
    annotation's rect via that helper

T08 End-to-end test (PRD scenario steps 5-9)
  - tests/integration/forms-overlay-e2e.dom.test.tsx: full path from
    Review-mode capture through Forms-mode link to active triple +
    aria-current assertions + 2 SVG paths in the overlay
  - additional integration coverage: forms-link-flow + forms-active-cycling

Gates: typecheck ✓ · lint ✓ · build ✓ · 152/152 tests across 21 files.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/anchor/index.ts

@@ -1,6 +1,7 @@
 export * from "./types";
 export {
   PdfSpikeViewer,
+  getHighlightClientRects,
   selectorsFromPdfCapture,
   type PdfSpikeViewerProps,
   type StoredAnnotation,

src/anchor/pdf-viewer-adapter-spike.tsx

@@ -113,13 +113,50 @@ function captureFromPdfSelection(sel: PdfSelection): PdfSelectionCapture {
  */
 function SpikeHighlightContainer(): ReactNode {
   const { highlight, isScrolledTo } = useHighlightContainerContext();
+  // Wrap the highlight in a data-tagged container so the visual-guide
+  // overlay's HighlightRectBridge can locate it via DOM query. The
+  // wrapper uses display: contents so it doesn't affect layout — the
+  // bounding rect is gathered from the live TextHighlight children at
+  // query time.
   return (
-    <MonitoredHighlightContainer>
-      <TextHighlight highlight={highlight} isScrolledTo={isScrolledTo} />
-    </MonitoredHighlightContainer>
+    <div data-highlight-id={highlight.id} style={{ display: "contents" }}>
+      <MonitoredHighlightContainer>
+        <TextHighlight highlight={highlight} isScrolledTo={isScrolledTo} />
+      </MonitoredHighlightContainer>
+    </div>
   );
 }
 
+/**
+ * Resolve the rendered DOM rect for a highlight by data attribute, or
+ * `null` if the highlight isn't currently rendered (e.g. its page hasn't
+ * scrolled into view). Used by `app/forms/HighlightRectBridge` to feed
+ * the rect registry as kind="highlight".
+ *
+ * `display: contents` on the wrapper means it has no box of its own; we
+ * union the rects of its children. For TextHighlight that's typically
+ * one rect per line.
+ */
+export function getHighlightClientRects(annotationId: string): DOMRect | null {
+  if (typeof document === "undefined") return null;
+  const wrapper = document.querySelector(`[data-highlight-id="${CSS.escape(annotationId)}"]`);
+  if (!wrapper) return null;
+  const rects = wrapper.getClientRects();
+  if (rects.length === 0) return null;
+  let left = Infinity;
+  let top = Infinity;
+  let right = -Infinity;
+  let bottom = -Infinity;
+  for (const r of Array.from(rects)) {
+    left = Math.min(left, r.left);
+    top = Math.min(top, r.top);
+    right = Math.max(right, r.right);
+    bottom = Math.max(bottom, r.bottom);
+  }
+  if (!isFinite(left)) return null;
+  return new DOMRect(left, top, right - left, bottom - top);
+}
+
 export interface PdfSpikeViewerProps {
   /** URL of the PDF to load (served by Vite dev server). */
   readonly pdfUrl: string;

src/app/App.tsx

@@ -1,40 +1,136 @@
 /**
  * App — the citation-evidence MVP shell.
  *
- * Three-pane layout per `wiki/ArchitectureOverview.md` §12.1:
+ * Composes the two top-level layouts:
  *
- *     ┌────────────┬──────────────────┬────────────┐
- *     │ Collection │ Document Viewer  │ Evidence   │
- *     │ List       │                  │ Sidebar    │
- *     └────────────┴──────────────────┴────────────┘
+ *   - Review mode (CE-WP-0002): collection list / viewer / evidence sidebar.
+ *   - Forms mode (CE-WP-0003): form renderer / viewer / evidence strip,
+ *     with click-to-link interaction.
  *
- * CE-WP-0002-T06 stops at "viewer shell is rendered, evidence list is
- * displayed". T07 wires the selection → annotation → evidence flow; T08
- * wires the sidebar-click → scroll-to-passage round-trip.
+ * Mode selection is driven by `location.hash`: `#/forms/demo` lands in
+ * Forms mode; anything else (including empty) lands in Review mode. The
+ * top bar toggles between them. We keep the hash sync so reload + deep
+ * links work; T08's E2E asserts the `/forms/demo` navigation path.
+ *
+ * Engine and binder providers are both mounted at the App root so
+ * evidence/annotations/links survive switching tabs.
  */
 
+import { useEffect, useState } from "react";
+
+import { BinderProvider } from "@binder/index";
 import {
-  CollectionList,
   EngineProvider,
-  EvidenceSidebar,
-  ViewerShell,
+  useEngine,
 } from "@work/index";
 
+import { FormsApp } from "./forms/FormsApp";
+import { ReviewLayout } from "./ReviewLayout";
+
+type Mode = "review" | "forms";
+
+const FORMS_HASH = "#/forms/demo";
+
+function readModeFromHash(): Mode {
+  if (typeof window === "undefined") return "review";
+  return window.location.hash === FORMS_HASH ? "forms" : "review";
+}
+
+function writeModeToHash(mode: Mode) {
+  if (typeof window === "undefined") return;
+  const target = mode === "forms" ? FORMS_HASH : "";
+  if (window.location.hash !== target) {
+    if (target) {
+      window.location.hash = target;
+    } else {
+      // Clear hash without leaving "#" trailing in the URL bar.
+      history.replaceState(null, "", window.location.pathname + window.location.search);
+    }
+  }
+}
+
+function ModeRouter() {
+  const [mode, setMode] = useState<Mode>(() => readModeFromHash());
+
+  useEffect(() => {
+    function onHash() {
+      setMode(readModeFromHash());
+    }
+    window.addEventListener("hashchange", onHash);
+    return () => window.removeEventListener("hashchange", onHash);
+  }, []);
+
+  const handleModeChange = (next: Mode) => {
+    writeModeToHash(next);
+    setMode(next);
+  };
+
+  return (
+    <div style={{ display: "flex", flexDirection: "column", height: "100vh", color: "#222" }}>
+      <TopBar mode={mode} onModeChange={handleModeChange} />
+      <div style={{ flex: 1, minHeight: 0 }}>
+        {mode === "review" ? <ReviewLayout /> : <FormsApp />}
+      </div>
+    </div>
+  );
+}
+
+function TopBar({ mode, onModeChange }: { mode: Mode; onModeChange: (m: Mode) => void }) {
+  return (
+    <header
+      style={{
+        display: "flex",
+        gap: 8,
+        padding: "6px 12px",
+        borderBottom: "1px solid #ddd",
+        background: "#fafafa",
+        fontFamily: "system-ui, sans-serif",
+        alignItems: "center",
+      }}
+    >
+      <strong style={{ fontSize: 13, marginRight: 8 }}>citation-evidence</strong>
+      <button
+        onClick={() => onModeChange("review")}
+        aria-pressed={mode === "review"}
+        style={tabStyle(mode === "review")}
+      >
+        Review
+      </button>
+      <button
+        onClick={() => onModeChange("forms")}
+        aria-pressed={mode === "forms"}
+        style={tabStyle(mode === "forms")}
+      >
+        Forms
+      </button>
+    </header>
+  );
+}
+
+function tabStyle(active: boolean) {
+  return {
+    padding: "4px 12px",
+    fontSize: 12,
+    border: "1px solid #ccc",
+    borderBottom: active ? "2px solid #0050b3" : "1px solid #ccc",
+    background: active ? "#e8f0ff" : "white",
+    cursor: "pointer" as const,
+  };
+}
+
+function AppInner() {
+  const engine = useEngine();
+  return (
+    <BinderProvider bus={engine.bus}>
+      <ModeRouter />
+    </BinderProvider>
+  );
+}
+
 export function App() {
   return (
     <EngineProvider>
-      <div
-        style={{
-          display: "flex",
-          height: "100vh",
-          fontFamily: "system-ui, sans-serif",
-          color: "#222",
-        }}
-      >
-        <CollectionList />
-        <ViewerShell />
-        <EvidenceSidebar />
-      </div>
+      <AppInner />
     </EngineProvider>
   );
 }

src/app/ReviewLayout.tsx

@@ -0,0 +1,30 @@
+/**
+ * Review mode — the three-pane layout from CE-WP-0002-T06.
+ *
+ *     ┌────────────┬──────────────────┬────────────┐
+ *     │ Collection │ Document Viewer  │ Evidence   │
+ *     │ List       │                  │ Sidebar    │
+ *     └────────────┴──────────────────┴────────────┘
+ */
+
+import {
+  CollectionList,
+  EvidenceSidebar,
+  ViewerShell,
+} from "@work/index";
+
+export function ReviewLayout() {
+  return (
+    <div
+      style={{
+        display: "flex",
+        height: "100%",
+        fontFamily: "system-ui, sans-serif",
+      }}
+    >
+      <CollectionList />
+      <ViewerShell />
+      <EvidenceSidebar />
+    </div>
+  );
+}

src/app/forms/ActiveEvidenceChips.tsx

@@ -0,0 +1,131 @@
+/**
+ * ActiveEvidenceChips — chip strip for the currently-focused field.
+ *
+ * Renders one chip per link on the active target. The chip:
+ *   - is a focusable `<button>` so Tab/Shift-Tab cycles natively;
+ *   - registers itself with the rect registry as `kind="evidence-card"`
+ *     and `id=evidenceItemId` (T07's overlay will draw from these);
+ *   - calls `setActiveEvidence(evidenceItemId, annotationId)` on focus
+ *     so the active-state machine + viewer scroll stay in sync.
+ *
+ * Auto-activation: when the active target changes and it has links, we
+ * focus the first chip. That gives the user immediate evidence preview
+ * without an extra click.
+ */
+
+import { useEffect, useRef } from "react";
+
+import type { EvidenceItemId } from "@shared/ids";
+
+import {
+  useActiveState,
+  useRegisterRect,
+} from "@binder/index";
+
+export interface ActiveEvidenceChipsItem {
+  readonly evidenceItemId: EvidenceItemId;
+  readonly annotationId: import("@shared/ids").AnnotationId | null;
+  readonly quote: string;
+  readonly commentary?: string;
+}
+
+export interface ActiveEvidenceChipsProps {
+  readonly items: readonly ActiveEvidenceChipsItem[];
+}
+
+function Chip({
+  item,
+  isActive,
+}: {
+  item: ActiveEvidenceChipsItem;
+  isActive: boolean;
+}) {
+  const ref = useRef<HTMLButtonElement>(null);
+  useRegisterRect("evidence-card", item.evidenceItemId, ref);
+  const { setActiveEvidence } = useActiveState();
+
+  return (
+    <button
+      ref={ref}
+      onFocus={() => setActiveEvidence(item.evidenceItemId, item.annotationId)}
+      onClick={() => setActiveEvidence(item.evidenceItemId, item.annotationId)}
+      aria-current={isActive ? "true" : undefined}
+      data-active={isActive ? "true" : "false"}
+      data-evidence-id={item.evidenceItemId}
+      style={{
+        minWidth: 200,
+        maxWidth: 260,
+        textAlign: "left",
+        fontSize: 12,
+        padding: 6,
+        border: isActive ? "2px solid #0050b3" : "1px solid #aac",
+        background: isActive ? "#e8f0ff" : "#fffceb",
+        cursor: "pointer",
+      }}
+    >
+      <div style={{ fontStyle: "italic", marginBottom: 2 }}>
+        &ldquo;{item.quote.slice(0, 80)}
+        {item.quote.length > 80 ? "…" : ""}&rdquo;
+      </div>
+      {item.commentary && <div style={{ color: "#333" }}>{item.commentary}</div>}
+    </button>
+  );
+}
+
+export function ActiveEvidenceChips({ items }: ActiveEvidenceChipsProps) {
+  const { state, setActiveEvidence } = useActiveState();
+  const targetKey = state.activeTarget
+    ? `${state.activeTarget.targetType}:${state.activeTarget.targetId}`
+    : null;
+
+  // Auto-activate the first item whenever the active target changes and
+  // we have something to show.
+  useEffect(() => {
+    if (!targetKey) return;
+    if (items.length === 0) return;
+    if (state.activeEvidenceItemId) return; // already active
+    const first = items[0]!;
+    setActiveEvidence(first.evidenceItemId, first.annotationId);
+  }, [targetKey, items, state.activeEvidenceItemId, setActiveEvidence]);
+
+  if (!state.activeTarget) return null;
+  if (items.length === 0) {
+    return (
+      <div
+        role="status"
+        style={{
+          padding: 6,
+          fontSize: 11,
+          color: "#666",
+          fontFamily: "system-ui, sans-serif",
+        }}
+      >
+        No evidence linked to this field yet.
+      </div>
+    );
+  }
+
+  return (
+    <div
+      role="group"
+      aria-label="Evidence for active field"
+      style={{
+        display: "flex",
+        gap: 6,
+        padding: 6,
+        borderTop: "1px dashed #ccc",
+        background: "#fdfdfd",
+        flexWrap: "wrap",
+        fontFamily: "system-ui, sans-serif",
+      }}
+    >
+      {items.map((item) => (
+        <Chip
+          key={item.evidenceItemId}
+          item={item}
+          isActive={state.activeEvidenceItemId === item.evidenceItemId}
+        />
+      ))}
+    </div>
+  );
+}

src/app/forms/FormsApp.tsx

@@ -0,0 +1,322 @@
+/**
+ * FormsApp — the evidence-backed form mode for CE-WP-0003.
+ *
+ * Layout:
+ *
+ *     ┌────────────┬─────────────────┬─────────────┐
+ *     │ Collection │ FormRenderer    │ ViewerShell │
+ *     │            │ (left)          │ (right)     │
+ *     ├────────────┴─────────────────┴─────────────┤
+ *     │ EvidenceStrip (bottom)                     │
+ *     └────────────────────────────────────────────┘
+ *
+ * Linking interaction (T05):
+ *   1. User clicks an evidence card in the strip → it becomes "selected
+ *      for linking" (highlighted; banner appears in the form pane).
+ *   2. User then clicks a form field. The field's `FormFieldActivated`
+ *      event triggers `bindings.linkEvidenceToTarget(selected, field)`.
+ *   3. The selected-for-linking state clears; the field's link count
+ *      chip increments.
+ *
+ * Active-evidence cycling (T06) and the visual guide overlay (T07) build
+ * on this composition without changing the link interaction.
+ */
+
+import { useEffect, useMemo, useState } from "react";
+
+import type { EvidenceItem } from "@shared/evidence";
+import type { AnnotationId, EvidenceItemId } from "@shared/ids";
+
+import { Overlay, useActiveState, useBinder } from "@binder/index";
+import {
+  CollectionList,
+  ViewerShell,
+  useActiveDocument,
+  useEngine,
+  useEngineEventTick,
+  useScrollToAnnotation,
+} from "@work/index";
+
+import { FormRenderer } from "@binder/FormRenderer";
+
+import { ActiveEvidenceChips, type ActiveEvidenceChipsItem } from "./ActiveEvidenceChips";
+import { DEMO_SCHEMA } from "./demo-schema";
+import { HighlightRectBridge } from "./HighlightRectBridge";
+
+export function FormsApp() {
+  return (
+    <div style={{ display: "flex", flexDirection: "column", height: "100%" }}>
+      <div style={{ display: "flex", flex: 1, minHeight: 0 }}>
+        <CollectionList />
+        <FormPane />
+        <ViewerShell />
+      </div>
+      <EvidenceStrip />
+      <ScrollBridge />
+      <HighlightRectBridge />
+      <Overlay />
+    </div>
+  );
+}
+
+/**
+ * Bridge: the binder's active-state machine doesn't know how to scroll
+ * the viewer; the work-level `useScrollToAnnotation` does. This subscriber
+ * reads `activeAnnotationId` from the binder and calls `scrollTo` whenever
+ * it changes. Lives in app/ because that's where both subsystems meet.
+ */
+function ScrollBridge() {
+  const { state } = useActiveState();
+  const { scrollTo } = useScrollToAnnotation();
+  useEffect(() => {
+    if (state.activeAnnotationId) {
+      scrollTo(state.activeAnnotationId);
+    }
+  }, [state.activeAnnotationId, scrollTo]);
+  return null;
+}
+
+function FormPane() {
+  const { document } = useActiveDocument();
+  const { bindings } = useBinder();
+  const engine = useEngine();
+  const linkTick = useEngineEventTick("EvidenceLinkCreated");
+  const { state: activeState } = useActiveState();
+
+  const [selectedForLinking, setSelectedForLinking] = useState<EvidenceItemId | null>(
+    null,
+  );
+
+  // Compute per-field link counts. Re-derives on link create.
+  const linkCounts = useMemo<Record<string, number>>(() => {
+    const out: Record<string, number> = {};
+    for (const field of DEMO_SCHEMA.fields) {
+      out[field.id] = bindings.listEvidenceForTarget({
+        targetType: "form-field",
+        targetId: field.id,
+      }).length;
+    }
+    void linkTick;
+    return out;
+  }, [bindings, linkTick]);
+
+  // Compute chip items for the currently-active target.
+  const activeChipItems = useMemo<readonly ActiveEvidenceChipsItem[]>(() => {
+    if (!activeState.activeTarget) return [];
+    const links = bindings.listEvidenceForTarget(activeState.activeTarget);
+    return links
+      .map((link): ActiveEvidenceChipsItem | null => {
+        const item = engine.evidence.get(link.evidenceItemId);
+        if (!item) return null;
+        const annotationId: AnnotationId | null = item.annotationIds[0] ?? null;
+        const annotation = annotationId ? engine.annotations.get(annotationId) : null;
+        return {
+          evidenceItemId: link.evidenceItemId,
+          annotationId,
+          quote: annotation?.quote ?? "(no quote)",
+          ...(item.commentary ? { commentary: item.commentary } : {}),
+        };
+      })
+      .filter((c): c is ActiveEvidenceChipsItem => c !== null);
+    // linkTick is included so newly created links populate the chips
+    // without an explicit refresh.
+  }, [activeState.activeTarget, bindings, engine, linkTick]);
+
+  // Listen for FormFieldActivated and, if an evidence is staged, create
+  // the link. The state machine reduction (focus-target) happens in
+  // parallel via ActiveStateProvider's own handler.
+  useEffect(() => {
+    return engine.bus.on("FormFieldActivated", (event) => {
+      if (!selectedForLinking) return;
+      bindings.linkEvidenceToTarget({
+        evidenceItemId: selectedForLinking,
+        target: event.target,
+      });
+      setSelectedForLinking(null);
+    });
+  }, [engine, bindings, selectedForLinking]);
+
+  return (
+    <main
+      style={{
+        flex: "1 1 0",
+        minWidth: 320,
+        borderRight: "1px solid #ddd",
+        overflow: "auto",
+      }}
+    >
+      <SelectedBanner
+        selectedForLinking={selectedForLinking}
+        onClear={() => setSelectedForLinking(null)}
+      />
+      {document ? (
+        <>
+          <FormRenderer schema={DEMO_SCHEMA} linkCounts={linkCounts} />
+          <ActiveEvidenceChips items={activeChipItems} />
+        </>
+      ) : (
+        <EmptyHint />
+      )}
+      <SelectionContext setSelected={setSelectedForLinking} />
+    </main>
+  );
+}
+
+function EmptyHint() {
+  return (
+    <p style={{ padding: 12, color: "#666", fontSize: 13, fontFamily: "system-ui, sans-serif" }}>
+      Pick a fixture from the collection list to start binding evidence.
+    </p>
+  );
+}
+
+function SelectedBanner({
+  selectedForLinking,
+  onClear,
+}: {
+  selectedForLinking: EvidenceItemId | null;
+  onClear: () => void;
+}) {
+  if (!selectedForLinking) return null;
+  return (
+    <div
+      role="status"
+      aria-live="polite"
+      style={{
+        padding: 8,
+        background: "#fff4d6",
+        borderBottom: "1px solid #f0c040",
+        fontFamily: "system-ui, sans-serif",
+        fontSize: 12,
+        display: "flex",
+        alignItems: "center",
+        gap: 8,
+      }}
+    >
+      <span>
+        Evidence staged for linking. Click a form field to link it, or{" "}
+      </span>
+      <button onClick={onClear} style={{ fontSize: 12, padding: "2px 8px" }}>
+        cancel
+      </button>
+    </div>
+  );
+}
+
+/**
+ * Bridges the strip's "stage this evidence" callback to the FormPane's
+ * local state. The strip lives in a sibling DOM subtree; rather than
+ * lifting `selectedForLinking` all the way up to FormsApp, we publish a
+ * setter into a module-scoped event target.
+ *
+ * Simpler than another context for one local handshake.
+ */
+const STAGED_EVENT = "citation-evidence:staged-for-linking";
+
+function SelectionContext({
+  setSelected,
+}: {
+  setSelected: (id: EvidenceItemId | null) => void;
+}) {
+  useEffect(() => {
+    const handler = (e: Event) => {
+      const detail = (e as CustomEvent<EvidenceItemId | null>).detail;
+      setSelected(detail);
+    };
+    window.addEventListener(STAGED_EVENT, handler);
+    return () => window.removeEventListener(STAGED_EVENT, handler);
+  }, [setSelected]);
+  return null;
+}
+
+export function publishStagedForLinking(id: EvidenceItemId | null) {
+  if (typeof window === "undefined") return;
+  window.dispatchEvent(new CustomEvent(STAGED_EVENT, { detail: id }));
+}
+
+function EvidenceStrip() {
+  const engine = useEngine();
+  const { document } = useActiveDocument();
+  const createTick = useEngineEventTick("EvidenceItemCreated");
+  const updateTick = useEngineEventTick("EvidenceItemUpdated");
+  const linkTick = useEngineEventTick("EvidenceLinkCreated");
+  const { state: activeState } = useActiveState();
+  const [stagedId, setStagedId] = useState<EvidenceItemId | null>(null);
+
+  const items = useMemo<readonly EvidenceItem[]>(() => {
+    if (!document) return [];
+    void createTick;
+    void updateTick;
+    void linkTick;
+    return engine.evidence.listByDocument(document.id);
+  }, [document, engine, createTick, updateTick, linkTick]);
+
+  const handleStage = (id: EvidenceItemId) => {
+    const next = stagedId === id ? null : id;
+    setStagedId(next);
+    publishStagedForLinking(next);
+  };
+
+  if (!document) return null;
+
+  return (
+    <section
+      aria-label="Evidence list"
+      style={{
+        borderTop: "1px solid #ddd",
+        background: "#fafafa",
+        padding: 8,
+        display: "flex",
+        gap: 8,
+        overflowX: "auto",
+        flex: "0 0 auto",
+        minHeight: 100,
+        fontFamily: "system-ui, sans-serif",
+      }}
+    >
+      {items.length === 0 && (
+        <p style={{ fontSize: 12, color: "#888", margin: 0, alignSelf: "center" }}>
+          No evidence yet. Switch to Review mode to capture a passage.
+        </p>
+      )}
+      {items.map((item) => {
+        const firstAnn = item.annotationIds[0]
+          ? engine.annotations.get(item.annotationIds[0])
+          : null;
+        const quote = firstAnn?.quote ?? "(no quote)";
+        const isStaged = stagedId === item.id;
+        const isActive = activeState.activeEvidenceItemId === item.id;
+        return (
+          <button
+            key={item.id}
+            onClick={() => handleStage(item.id)}
+            data-staged={isStaged ? "true" : "false"}
+            aria-current={isActive ? "true" : undefined}
+            style={{
+              minWidth: 220,
+              maxWidth: 280,
+              textAlign: "left",
+              fontSize: 12,
+              padding: 8,
+              border: isActive
+                ? "2px solid #0050b3"
+                : isStaged
+                ? "2px solid #f0a000"
+                : "1px solid #ccc",
+              background: isActive ? "#e8f0ff" : isStaged ? "#fff4d6" : "white",
+              cursor: "pointer",
+            }}
+          >
+            <div style={{ fontStyle: "italic", marginBottom: 4 }}>
+              &ldquo;{quote.slice(0, 100)}
+              {quote.length > 100 ? "…" : ""}&rdquo;
+            </div>
+            {item.commentary && (
+              <div style={{ color: "#333" }}>{item.commentary}</div>
+            )}
+          </button>
+        );
+      })}
+    </section>
+  );
+}

src/app/forms/HighlightRectBridge.tsx

@@ -0,0 +1,46 @@
+/**
+ * HighlightRectBridge — wires the viewer's rendered highlight DOM into
+ * the binder's rect registry as `kind="highlight"`.
+ *
+ * The viewer adapter exposes `getHighlightClientRects(annotationId)`
+ * (CE-WP-0003-T07) which returns the live bounding rect of a highlight
+ * by data attribute. We register a lazy callback that re-runs that
+ * lookup on every `rect-changed` event from the scroll/resize pump, so
+ * even as the user scrolls, the registered rect tracks the visible
+ * position.
+ *
+ * Lives in app/ because it spans:
+ *   - binder (rect registry)
+ *   - work (active document, scroll bridge)
+ *   - anchor (the DOM-query helper)
+ *
+ * If the active annotation isn't currently rendered (its page is off
+ * screen, or no highlight matched), the callback returns null and the
+ * overlay omits the card→highlight curve until it becomes visible.
+ */
+
+import { useEffect } from "react";
+
+import { getHighlightClientRects } from "@anchor/index";
+import {
+  useActiveState,
+  useRectRegistryContext,
+} from "@binder/index";
+
+export function HighlightRectBridge() {
+  const { state } = useActiveState();
+  const { registry } = useRectRegistryContext();
+
+  useEffect(() => {
+    const annotationId = state.activeAnnotationId;
+    if (!annotationId) return;
+    const unregister = registry.register(
+      "highlight",
+      annotationId,
+      () => getHighlightClientRects(annotationId),
+    );
+    return unregister;
+  }, [state.activeAnnotationId, registry]);
+
+  return null;
+}

src/app/forms/demo-schema.ts

@@ -0,0 +1,29 @@
+/**
+ * Demo form schema for CE-WP-0003 (the form-binding slice).
+ *
+ * Deliberately minimal: text, textarea, date. JSON Schema is **not** used
+ * here — that's deferred to a later ADR. The MVP form's only job is to
+ * render a handful of fields and accept evidence links so the visual-guide
+ * round-trip can be exercised end-to-end.
+ */
+
+export type FormFieldSchema =
+  | { readonly type: "text"; readonly id: string; readonly label: string }
+  | { readonly type: "textarea"; readonly id: string; readonly label: string }
+  | { readonly type: "date"; readonly id: string; readonly label: string };
+
+export interface FormSchema {
+  readonly id: string;
+  readonly title: string;
+  readonly fields: readonly FormFieldSchema[];
+}
+
+export const DEMO_SCHEMA: FormSchema = {
+  id: "demo-form",
+  title: "Demo evidence-backed form",
+  fields: [
+    { type: "textarea", id: "summary", label: "Summary of the matter" },
+    { type: "date", id: "deadline", label: "Key deadline" },
+    { type: "text", id: "amount", label: "Disputed amount" },
+  ],
+};

src/binder/BinderProvider.tsx

@@ -0,0 +1,97 @@
+/**
+ * BinderProvider — composition root for the binder subsystem.
+ *
+ * Wires the four binder concerns (rect registry, binding service, link
+ * repo, active state machine) into one provider so a single mount inside
+ * the EngineProvider gives every binder consumer (FormRenderer, evidence
+ * picker, SVG overlay) what it needs.
+ *
+ * The provider is split out from the engine because in a future
+ * subsystem-extraction these will live in separate packages — the engine
+ * will publish only the event bus and the engine services, while
+ * `evidence-binder` will export this provider.
+ */
+
+import {
+  createContext,
+  useContext,
+  useEffect,
+  useMemo,
+  type ReactNode,
+} from "react";
+
+import type { EventBus } from "@engine/events";
+
+import {
+  ActiveStateProvider,
+  useActiveState,
+} from "./state/active";
+import {
+  createInMemoryLinkRepo,
+  type EvidenceLinkRepository,
+} from "./repos/in-memory-links";
+import {
+  createBindingService,
+  type BindingService,
+} from "./services/bindings";
+import {
+  RectRegistryProvider,
+  createRectRegistryContextValue,
+  type RectRegistryContextValue,
+} from "./visual-guide/react-hooks";
+
+export interface BinderServices {
+  readonly links: EvidenceLinkRepository;
+  readonly bindings: BindingService;
+  readonly rect: RectRegistryContextValue;
+}
+
+const BinderServicesContext = createContext<BinderServices | null>(null);
+
+export function useBinder(): BinderServices {
+  const ctx = useContext(BinderServicesContext);
+  if (!ctx) throw new Error("useBinder: missing <BinderProvider />");
+  return ctx;
+}
+
+export interface BinderProviderProps {
+  readonly children: ReactNode;
+  /**
+   * The engine's event bus, threaded in by the composition root so the
+   * binder can emit §4 events without importing work/EngineContext
+   * (work cannot be a dependency of binder — see DependencyMap §2).
+   */
+  readonly bus: EventBus;
+  /**
+   * Tests can inject a pre-built service set; production constructs a
+   * fresh one. The rect registry is *always* fresh per provider mount
+   * because its observers attach to the current `window`.
+   */
+  readonly services?: Omit<BinderServices, "rect">;
+}
+
+export function BinderProvider({ children, bus, services }: BinderProviderProps) {
+  const built = useMemo<BinderServices>(() => {
+    const links = services?.links ?? createInMemoryLinkRepo();
+    const bindings = services?.bindings ?? createBindingService(links, bus);
+    const rect = createRectRegistryContextValue();
+    return { links, bindings, rect };
+  }, [bus, services]);
+
+  // Disconnect rect observers + listeners on unmount.
+  useEffect(() => {
+    return () => {
+      built.rect.observer.disconnect();
+    };
+  }, [built.rect]);
+
+  return (
+    <BinderServicesContext.Provider value={built}>
+      <RectRegistryProvider value={built.rect}>
+        <ActiveStateProvider bus={bus}>{children}</ActiveStateProvider>
+      </RectRegistryProvider>
+    </BinderServicesContext.Provider>
+  );
+}
+
+export { useActiveState };

src/binder/FormRenderer.dom.test.tsx

@@ -0,0 +1,114 @@
+/**
+ * FormRenderer (CE-WP-0003-T04) — happy-dom test covering:
+ *   - schema → DOM (3 demo fields render with their labels)
+ *   - each field registers with rect registry as kind="field"
+ *   - focusing a field calls activeState.focusTarget and emits FormFieldActivated
+ *   - typing in a field invokes onValueChange
+ *   - linkCounts shows the chip when > 0
+ */
+
+// @vitest-environment happy-dom
+
+import { cleanup, render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+
+import { createEventBus, type EngineEvent } from "@engine/events";
+
+import { FormRenderer, type FormSchema } from "./FormRenderer";
+import {
+  ActiveStateProvider,
+} from "./state/active";
+import {
+  RectRegistryProvider,
+  createRectRegistryContextValue,
+} from "./visual-guide/react-hooks";
+
+const SCHEMA: FormSchema = {
+  id: "demo",
+  title: "Demo form",
+  fields: [
+    { type: "textarea", id: "summary", label: "Summary" },
+    { type: "date", id: "deadline", label: "Deadline" },
+    { type: "text", id: "amount", label: "Amount" },
+  ],
+};
+
+function renderWithProviders(props: Parameters<typeof FormRenderer>[0]) {
+  const bus = createEventBus();
+  const events: EngineEvent[] = [];
+  bus.onAny((e) => events.push(e));
+  const ctxValue = createRectRegistryContextValue();
+  const utils = render(
+    <RectRegistryProvider value={ctxValue}>
+      <ActiveStateProvider bus={bus}>
+        <FormRenderer {...props} />
+      </ActiveStateProvider>
+    </RectRegistryProvider>,
+  );
+  return { ...utils, ctxValue, bus, events };
+}
+
+describe("FormRenderer (CE-WP-0003-T04)", () => {
+  let cleanupCtx: (() => void) | null = null;
+  beforeEach(() => {
+    cleanupCtx = null;
+  });
+  afterEach(() => {
+    cleanupCtx?.();
+    cleanup();
+  });
+
+  it("renders each schema field with its label", () => {
+    renderWithProviders({ schema: SCHEMA });
+    expect(screen.getByLabelText("Summary")).toBeTruthy();
+    expect(screen.getByLabelText("Deadline")).toBeTruthy();
+    expect(screen.getByLabelText("Amount")).toBeTruthy();
+  });
+
+  it("registers each field with the rect registry as kind=field", () => {
+    const { ctxValue } = renderWithProviders({ schema: SCHEMA });
+    cleanupCtx = () => ctxValue.observer.disconnect();
+    const list = ctxValue.registry.list();
+    expect(list).toHaveLength(3);
+    expect(list.every((r) => r.kind === "field")).toBe(true);
+    expect(list.map((r) => r.id).sort()).toEqual(["amount", "deadline", "summary"]);
+  });
+
+  it("focusing a field emits FormFieldActivated with the right target", async () => {
+    const user = userEvent.setup();
+    const { events, ctxValue } = renderWithProviders({ schema: SCHEMA });
+    cleanupCtx = () => ctxValue.observer.disconnect();
+    await user.click(screen.getByLabelText("Summary"));
+    const fieldEvents = events.filter((e) => e.type === "FormFieldActivated");
+    expect(fieldEvents).toHaveLength(1);
+    expect(fieldEvents[0]).toMatchObject({
+      target: { targetType: "form-field", targetId: "summary" },
+    });
+  });
+
+  it("typing forwards onValueChange with the field id + new value", async () => {
+    const user = userEvent.setup();
+    const changes: [string, string][] = [];
+    const { ctxValue } = renderWithProviders({
+      schema: SCHEMA,
+      onValueChange: (id, value) => changes.push([id, value]),
+    });
+    cleanupCtx = () => ctxValue.observer.disconnect();
+    await user.type(screen.getByLabelText("Amount"), "42");
+    expect(changes).toEqual([
+      ["amount", "4"],
+      ["amount", "2"],
+    ]);
+  });
+
+  it("renders the link-count chip when linkCounts[fieldId] > 0", () => {
+    const { ctxValue } = renderWithProviders({
+      schema: SCHEMA,
+      linkCounts: { summary: 2, amount: 0 },
+    });
+    cleanupCtx = () => ctxValue.observer.disconnect();
+    expect(screen.queryByTestId("field-summary-chip")).not.toBeNull();
+    expect(screen.queryByTestId("field-amount-chip")).toBeNull();
+  });
+});

src/binder/FormRenderer.tsx

@@ -0,0 +1,161 @@
+/**
+ * FormRenderer — renders a FormSchema as a small evidence-backed form.
+ *
+ * Each field registers itself with the rect registry under
+ * `kind="field"` and the field's `id`, so the SVG visual guide (T07) can
+ * draw curves from the active field to its linked evidence card and on
+ * to the source highlight.
+ *
+ * Lives in `src/binder/` (not `src/work/`) because it depends on the
+ * rect-registry hooks in `binder/visual-guide`. See `wiki/DependencyMap.md`
+ * §2/§5 for the `work ⊄ binder` rule that motivates this placement.
+ *
+ * No styling beyond minimum legibility (workplan T06 note). Tailwind /
+ * design system can land later without changing the registry contract.
+ */
+
+import { useRef, type ChangeEvent } from "react";
+
+import type { EvidenceTarget } from "@shared/evidence-link";
+
+import { useActiveState, type ActiveState } from "./state/active";
+import { useRegisterRect } from "./visual-guide/react-hooks";
+
+function isFieldActive(state: ActiveState, fieldId: string): boolean {
+  return (
+    state.activeTarget?.targetType === "form-field" &&
+    state.activeTarget?.targetId === fieldId
+  );
+}
+
+export interface FormFieldSchema {
+  readonly type: "text" | "textarea" | "date";
+  readonly id: string;
+  readonly label: string;
+}
+
+export interface FormSchema {
+  readonly id: string;
+  readonly title: string;
+  readonly fields: readonly FormFieldSchema[];
+}
+
+export interface FormRendererProps {
+  readonly schema: FormSchema;
+  readonly values?: Readonly<Record<string, string>>;
+  readonly onValueChange?: (fieldId: string, value: string) => void;
+  /**
+   * Per-field annotation count. Rendered as a small chip beside the
+   * label so the user can tell which fields already have evidence.
+   */
+  readonly linkCounts?: Readonly<Record<string, number>>;
+}
+
+function FieldRow({
+  field,
+  value,
+  linkCount,
+  isActive,
+  onChange,
+  onFocus,
+}: {
+  field: FormFieldSchema;
+  value: string;
+  linkCount: number;
+  isActive: boolean;
+  onChange: (next: string) => void;
+  onFocus: () => void;
+}) {
+  const ref = useRef<HTMLDivElement>(null);
+  useRegisterRect("field", field.id, ref);
+
+  const sharedProps = {
+    id: `field-${field.id}`,
+    value,
+    onFocus,
+    onChange: (e: ChangeEvent<HTMLInputElement | HTMLTextAreaElement>) =>
+      onChange(e.target.value),
+    style: { width: "100%", boxSizing: "border-box" as const, fontSize: 13, padding: 4 },
+  };
+
+  return (
+    <div
+      ref={ref}
+      data-field-id={field.id}
+      data-link-count={String(linkCount)}
+      aria-current={isActive ? "true" : undefined}
+      style={{
+        marginBottom: 12,
+        fontFamily: "system-ui, sans-serif",
+        padding: 4,
+        borderRadius: 4,
+        background: isActive ? "#e8f0ff" : "transparent",
+      }}
+    >
+      <label
+        htmlFor={sharedProps.id}
+        style={{ display: "block", fontSize: 12, fontWeight: 600, marginBottom: 4 }}
+      >
+        {field.label}
+        {linkCount > 0 ? (
+          <span
+            data-testid={`field-${field.id}-chip`}
+            style={{
+              marginLeft: 8,
+              padding: "1px 6px",
+              borderRadius: 4,
+              background: "#e7f0ff",
+              color: "#0050b3",
+              fontSize: 11,
+              fontWeight: 500,
+            }}
+          >
+            {linkCount} evidence
+          </span>
+        ) : null}
+      </label>
+      {field.type === "textarea" ? (
+        <textarea rows={2} {...sharedProps} />
+      ) : (
+        <input type={field.type === "date" ? "date" : "text"} {...sharedProps} />
+      )}
+    </div>
+  );
+}
+
+export function FormRenderer({
+  schema,
+  values,
+  onValueChange,
+  linkCounts,
+}: FormRendererProps) {
+  const { state, focusTarget } = useActiveState();
+
+  const handleFocus = (fieldId: string) => {
+    const target: EvidenceTarget = { targetType: "form-field", targetId: fieldId };
+    focusTarget(target);
+  };
+
+  return (
+    <form
+      data-form-id={schema.id}
+      style={{ padding: 12 }}
+      onSubmit={(e) => e.preventDefault()}
+    >
+      <h2 style={{ fontSize: 14, marginTop: 0, fontFamily: "system-ui, sans-serif" }}>
+        {schema.title}
+      </h2>
+      {schema.fields.map((field) => (
+        <FieldRow
+          key={field.id}
+          field={field}
+          value={values?.[field.id] ?? ""}
+          linkCount={linkCounts?.[field.id] ?? 0}
+          isActive={isFieldActive(state, field.id)}
+          onChange={(next) => onValueChange?.(field.id, next)}
+          onFocus={() => handleFocus(field.id)}
+        />
+      ))}
+    </form>
+  );
+}

src/binder/index.ts

@@ -1 +1,12 @@
-export {};
+export * from "./repos";
+export * from "./services";
+export * from "./state";
+export * from "./visual-guide";
+export { FormRenderer } from "./FormRenderer";
+export type {
+  FormFieldSchema,
+  FormRendererProps,
+  FormSchema,
+} from "./FormRenderer";
+export { BinderProvider, useBinder } from "./BinderProvider";
+export type { BinderServices, BinderProviderProps } from "./BinderProvider";

src/binder/repos/index.ts

@@ -0,0 +1 @@
+export * from "./in-memory-links";

src/binder/services/bindings.test.ts

@@ -0,0 +1,180 @@
+/**
+ * Binding service + in-memory link repo tests.
+ *
+ * Exercises every public surface plus the §4 events the service emits.
+ */
+
+import { describe, expect, it } from "vitest";
+
+import type {
+  EvidenceLink,
+  EvidenceTarget,
+} from "@shared/evidence-link";
+import type {
+  EvidenceItemId,
+  EvidenceLinkId,
+} from "@shared/ids";
+
+import { createEventBus } from "@engine/events";
+import type { EngineEvent } from "@engine/events";
+
+import { createInMemoryLinkRepo } from "../repos/in-memory-links";
+import { createBindingService } from "./bindings";
+
+function makeFixture() {
+  const bus = createEventBus();
+  const repo = createInMemoryLinkRepo();
+  const events: EngineEvent[] = [];
+  bus.onAny((e) => events.push(e));
+  let counter = 0;
+  const now = () => `2026-05-25T00:00:0${counter++}.000Z`;
+  const service = createBindingService(repo, bus, now);
+  return { bus, repo, events, service };
+}
+
+const FIELD_A: EvidenceTarget = { targetType: "form-field", targetId: "summary" };
+const FIELD_B: EvidenceTarget = { targetType: "form-field", targetId: "amount" };
+const EV1 = "ev_test_one" as EvidenceItemId;
+const EV2 = "ev_test_two" as EvidenceItemId;
+
+describe("createBindingService", () => {
+  it("linkEvidenceToTarget creates a link, emits EvidenceLinkCreated, and persists it", () => {
+    const { service, repo, events } = makeFixture();
+
+    const link = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+    });
+
+    expect(link.evidenceItemId).toBe(EV1);
+    expect(link.targetType).toBe("form-field");
+    expect(link.targetId).toBe("summary");
+    expect(link.relation).toBe("supports");
+    expect(link.status).toBe("candidate");
+    expect(link.createdAt).toBe(link.updatedAt);
+
+    expect(repo.get(link.id)).toEqual(link);
+
+    const created = events.filter((e) => e.type === "EvidenceLinkCreated");
+    expect(created).toHaveLength(1);
+    expect(created[0]).toMatchObject({ linkId: link.id, link });
+  });
+
+  it("honours explicit relation/status/confidence", () => {
+    const { service } = makeFixture();
+
+    const link = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+      relation: "contradicts",
+      status: "conflicting",
+      confidence: 0.42,
+      createdBy: "tegwick",
+    });
+
+    expect(link.relation).toBe("contradicts");
+    expect(link.status).toBe("conflicting");
+    expect(link.confidence).toBe(0.42);
+    expect(link.createdBy).toBe("tegwick");
+  });
+
+  it("listEvidenceForTarget returns only links for the requested target", () => {
+    const { service } = makeFixture();
+    const a1 = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+    service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_B });
+    const a2 = service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_A });
+
+    const linksForA = service.listEvidenceForTarget(FIELD_A);
+    expect(linksForA.map((l) => l.id).sort()).toEqual([a1.id, a2.id].sort());
+  });
+
+  it("listTargetsForEvidence returns all targets an evidence item is linked to", () => {
+    const { service } = makeFixture();
+    const a = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+    const b = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_B });
+    service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_A });
+
+    const targets = service.listTargetsForEvidence(EV1);
+    expect(targets.map((l) => l.id).sort()).toEqual([a.id, b.id].sort());
+  });
+
+  it("unlinkEvidence removes the link and reports success/failure", () => {
+    const { service } = makeFixture();
+    const link = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+
+    expect(service.unlinkEvidence(link.id)).toBe(true);
+    expect(service.getLink(link.id)).toBeNull();
+    expect(service.unlinkEvidence(link.id)).toBe(false);
+    expect(service.unlinkEvidence("evlink_unknown" as EvidenceLinkId)).toBe(false);
+  });
+
+  it("updateLink merges patch, bumps updatedAt, and emits EvidenceLinkUpdated", () => {
+    const { service, events } = makeFixture();
+    const original = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+    });
+
+    const updated = service.updateLink(original.id, {
+      status: "confirmed",
+      confidence: 0.9,
+    });
+
+    expect(updated.status).toBe("confirmed");
+    expect(updated.confidence).toBe(0.9);
+    expect(updated.relation).toBe(original.relation);
+    expect(updated.updatedAt).not.toBe(original.updatedAt);
+
+    const updatedEvents = events.filter((e) => e.type === "EvidenceLinkUpdated");
+    expect(updatedEvents).toHaveLength(1);
+    expect((updatedEvents[0] as Extract<EngineEvent, { type: "EvidenceLinkUpdated" }>).link).toEqual(updated);
+  });
+
+  it("updateLink throws on unknown id", () => {
+    const { service } = makeFixture();
+    expect(() =>
+      service.updateLink("evlink_unknown" as EvidenceLinkId, { status: "verified" }),
+    ).toThrow(/unknown id/);
+  });
+
+  it("setActiveEvidence emits EvidenceItemActivated with source=form-field", () => {
+    const { service, events } = makeFixture();
+    service.setActiveEvidence(EV1);
+    const activated = events.filter((e) => e.type === "EvidenceItemActivated");
+    expect(activated).toHaveLength(1);
+    expect(activated[0]).toMatchObject({ evidenceItemId: EV1, source: "form-field" });
+  });
+});
+
+describe("EvidenceLinkRepository (in-memory)", () => {
+  it("rejects duplicate ids on create", () => {
+    const repo = createInMemoryLinkRepo();
+    const link: EvidenceLink = {
+      id: "evlink_x" as EvidenceLinkId,
+      evidenceItemId: EV1,
+      targetType: "form-field",
+      targetId: "f",
+      relation: "supports",
+      status: "candidate",
+      createdAt: "2026-05-25T00:00:00.000Z",
+      updatedAt: "2026-05-25T00:00:00.000Z",
+    };
+    repo.create(link);
+    expect(() => repo.create(link)).toThrow(/duplicate/);
+  });
+
+  it("update throws on unknown id", () => {
+    const repo = createInMemoryLinkRepo();
+    const link: EvidenceLink = {
+      id: "evlink_unknown" as EvidenceLinkId,
+      evidenceItemId: EV1,
+      targetType: "form-field",
+      targetId: "f",
+      relation: "supports",
+      status: "candidate",
+      createdAt: "2026-05-25T00:00:00.000Z",
+      updatedAt: "2026-05-25T00:00:00.000Z",
+    };
+    expect(() => repo.update(link)).toThrow(/unknown/);
+  });
+});

src/binder/services/bindings.ts

@@ -0,0 +1,114 @@
+/**
+ * Binding service — links EvidenceItems to structured targets.
+ *
+ * Implements `wiki/ArchitectureOverview.md` §4.6 + SharedContracts §2.4
+ * (status enum), §2.5 (relation enum). Emits §4 events:
+ * `EvidenceLinkCreated`, `EvidenceLinkUpdated`, `EvidenceItemActivated`.
+ *
+ * MVP semantics:
+ *   - `linkEvidenceToTarget` defaults `relation="supports"`, `status="candidate"`.
+ *   - `unlinkEvidence` is hard-delete; the rejected-status path is left to
+ *     a later ADR.
+ *   - `setActiveEvidence` emits an `EvidenceItemActivated` event with
+ *     `source="form-field"` so the viewer/sidebar can react.
+ */
+
+import type {
+  EvidenceLink,
+  EvidenceLinkStoredStatus,
+  EvidenceRelation,
+  EvidenceTarget,
+} from "@shared/evidence-link";
+import type { EvidenceItemId, EvidenceLinkId } from "@shared/ids";
+import { newId } from "@shared/ids";
+
+import type { EventBus } from "@engine/events";
+
+import type { EvidenceLinkRepository } from "../repos/in-memory-links";
+
+export interface LinkEvidenceToTargetInput {
+  readonly evidenceItemId: EvidenceItemId;
+  readonly target: EvidenceTarget;
+  readonly relation?: EvidenceRelation;
+  readonly status?: EvidenceLinkStoredStatus;
+  readonly confidence?: number;
+  readonly createdBy?: string;
+}
+
+export interface UpdateLinkStatusInput {
+  readonly status?: EvidenceLinkStoredStatus;
+  readonly relation?: EvidenceRelation;
+  readonly confidence?: number;
+}
+
+export interface BindingService {
+  linkEvidenceToTarget(input: LinkEvidenceToTargetInput): EvidenceLink;
+  unlinkEvidence(id: EvidenceLinkId): boolean;
+  updateLink(id: EvidenceLinkId, input: UpdateLinkStatusInput): EvidenceLink;
+  getLink(id: EvidenceLinkId): EvidenceLink | null;
+  listEvidenceForTarget(target: EvidenceTarget): readonly EvidenceLink[];
+  listTargetsForEvidence(evidenceItemId: EvidenceItemId): readonly EvidenceLink[];
+  setActiveEvidence(evidenceItemId: EvidenceItemId): void;
+}
+
+export function createBindingService(
+  links: EvidenceLinkRepository,
+  bus: EventBus,
+  now: () => string = () => new Date().toISOString(),
+): BindingService {
+  return {
+    linkEvidenceToTarget(input) {
+      const ts = now();
+      const link: EvidenceLink = {
+        id: newId("evidence-link"),
+        evidenceItemId: input.evidenceItemId,
+        targetType: input.target.targetType,
+        targetId: input.target.targetId,
+        relation: input.relation ?? "supports",
+        status: input.status ?? "candidate",
+        ...(input.confidence !== undefined ? { confidence: input.confidence } : {}),
+        ...(input.createdBy !== undefined ? { createdBy: input.createdBy } : {}),
+        createdAt: ts,
+        updatedAt: ts,
+      };
+      const stored = links.create(link);
+      bus.emit({ type: "EvidenceLinkCreated", linkId: stored.id, link: stored });
+      return stored;
+    },
+    unlinkEvidence(id) {
+      return links.delete(id);
+    },
+    updateLink(id, input) {
+      const existing = links.get(id);
+      if (!existing) {
+        throw new Error(`BindingService.updateLink: unknown id ${id}`);
+      }
+      const next: EvidenceLink = {
+        ...existing,
+        ...(input.status !== undefined ? { status: input.status } : {}),
+        ...(input.relation !== undefined ? { relation: input.relation } : {}),
+        ...(input.confidence !== undefined ? { confidence: input.confidence } : {}),
+        updatedAt: now(),
+      };
+      const stored = links.update(next);
+      bus.emit({ type: "EvidenceLinkUpdated", linkId: stored.id, link: stored });
+      return stored;
+    },
+    getLink(id) {
+      return links.get(id);
+    },
+    listEvidenceForTarget(target) {
+      return links.listForTarget(target);
+    },
+    listTargetsForEvidence(evidenceItemId) {
+      return links.listForEvidenceItem(evidenceItemId);
+    },
+    setActiveEvidence(evidenceItemId) {
+      bus.emit({
+        type: "EvidenceItemActivated",
+        evidenceItemId,
+        source: "form-field",
+      });
+    },
+  };
+}

src/binder/services/index.ts

@@ -0,0 +1 @@
+export * from "./bindings";

src/binder/state/active.test.ts

@@ -0,0 +1,64 @@
+/**
+ * Reducer-level tests for the active-state machine.
+ *
+ * React-level Provider/hook tests live with the integration suites.
+ */
+
+import { describe, expect, it } from "vitest";
+
+import type { EvidenceTarget } from "@shared/evidence-link";
+import type { AnnotationId, EvidenceItemId } from "@shared/ids";
+
+import { __test } from "./active";
+
+const { reducer, EMPTY_ACTIVE_STATE } = __test;
+
+const FIELD_A: EvidenceTarget = { targetType: "form-field", targetId: "summary" };
+const FIELD_B: EvidenceTarget = { targetType: "form-field", targetId: "amount" };
+const EV1 = "ev_one" as EvidenceItemId;
+const EV2 = "ev_two" as EvidenceItemId;
+const ANN1 = "ann_one" as AnnotationId;
+
+describe("ActiveState reducer", () => {
+  it("focus-target sets activeTarget and clears active evidence", () => {
+    const seeded = reducer(EMPTY_ACTIVE_STATE, { type: "focus-target", target: FIELD_A });
+    const withEv = reducer(seeded, {
+      type: "set-active-evidence",
+      evidenceItemId: EV1,
+      annotationId: ANN1,
+    });
+    const refocused = reducer(withEv, { type: "focus-target", target: FIELD_B });
+    expect(refocused.activeTarget).toEqual(FIELD_B);
+    expect(refocused.activeEvidenceItemId).toBeNull();
+    expect(refocused.activeAnnotationId).toBeNull();
+  });
+
+  it("focus-target on the same target is a no-op (preserves identity)", () => {
+    const seeded = reducer(EMPTY_ACTIVE_STATE, { type: "focus-target", target: FIELD_A });
+    const withEv = reducer(seeded, {
+      type: "set-active-evidence",
+      evidenceItemId: EV1,
+      annotationId: ANN1,
+    });
+    const sameAgain = reducer(withEv, { type: "focus-target", target: { ...FIELD_A } });
+    expect(sameAgain).toBe(withEv);
+  });
+
+  it("set-active-evidence updates evidence + annotation without touching target", () => {
+    const seeded = reducer(EMPTY_ACTIVE_STATE, { type: "focus-target", target: FIELD_A });
+    const next = reducer(seeded, {
+      type: "set-active-evidence",
+      evidenceItemId: EV2,
+      annotationId: null,
+    });
+    expect(next.activeTarget).toEqual(FIELD_A);
+    expect(next.activeEvidenceItemId).toBe(EV2);
+    expect(next.activeAnnotationId).toBeNull();
+  });
+
+  it("clear returns to the empty state", () => {
+    const seeded = reducer(EMPTY_ACTIVE_STATE, { type: "focus-target", target: FIELD_A });
+    const cleared = reducer(seeded, { type: "clear" });
+    expect(cleared).toEqual(EMPTY_ACTIVE_STATE);
+  });
+});

src/binder/state/active.ts

@@ -0,0 +1,171 @@
+/**
+ * Active state machine + React context for the form-binding flow.
+ *
+ * Tracks the `(activeTarget, activeEvidenceItemId, activeAnnotationId)`
+ * triple that the SVG visual guide and the viewer adapter both depend on.
+ *
+ * Transitions:
+ *   - `focusTarget(target)` — clears the active evidence, emits
+ *     `FormFieldActivated`.
+ *   - `setActiveEvidence(evidenceItemId, annotationId?)` — sets active
+ *     evidence (and optionally the active annotation derived from it),
+ *     emits `EvidenceItemActivated` with `source="form-field"`. The
+ *     binding-service helper does the same; the state machine owns the
+ *     React-facing source of truth.
+ *   - `clear()` — drops everything back to undefined.
+ *
+ * The state itself is a small immutable record (so React equality checks
+ * stay simple). All mutations go through a single reducer.
+ */
+
+import {
+  createContext,
+  createElement,
+  useCallback,
+  useContext,
+  useEffect,
+  useMemo,
+  useReducer,
+  useRef,
+  type ReactNode,
+} from "react";
+
+import type { EvidenceTarget } from "@shared/evidence-link";
+import type { AnnotationId, EvidenceItemId } from "@shared/ids";
+
+import type { EventBus } from "@engine/events";
+
+export interface ActiveState {
+  readonly activeTarget: EvidenceTarget | null;
+  readonly activeEvidenceItemId: EvidenceItemId | null;
+  readonly activeAnnotationId: AnnotationId | null;
+}
+
+export const EMPTY_ACTIVE_STATE: ActiveState = {
+  activeTarget: null,
+  activeEvidenceItemId: null,
+  activeAnnotationId: null,
+};
+
+type Action =
+  | { type: "focus-target"; target: EvidenceTarget }
+  | {
+      type: "set-active-evidence";
+      evidenceItemId: EvidenceItemId;
+      annotationId: AnnotationId | null;
+    }
+  | { type: "clear" };
+
+function reducer(state: ActiveState, action: Action): ActiveState {
+  switch (action.type) {
+    case "focus-target":
+      // Focusing a target resets the active evidence — a different field
+      // means a different evidence set.
+      if (
+        state.activeTarget?.targetType === action.target.targetType &&
+        state.activeTarget?.targetId === action.target.targetId
+      ) {
+        return state;
+      }
+      return {
+        activeTarget: action.target,
+        activeEvidenceItemId: null,
+        activeAnnotationId: null,
+      };
+    case "set-active-evidence":
+      return {
+        activeTarget: state.activeTarget,
+        activeEvidenceItemId: action.evidenceItemId,
+        activeAnnotationId: action.annotationId,
+      };
+    case "clear":
+      return EMPTY_ACTIVE_STATE;
+  }
+}
+
+export interface ActiveStateApi {
+  readonly state: ActiveState;
+  focusTarget(target: EvidenceTarget): void;
+  setActiveEvidence(
+    evidenceItemId: EvidenceItemId,
+    annotationId?: AnnotationId | null,
+  ): void;
+  clear(): void;
+}
+
+const ActiveStateContext = createContext<ActiveStateApi | null>(null);
+
+export interface ActiveStateProviderProps {
+  readonly bus: EventBus;
+  readonly children: ReactNode;
+}
+
+/**
+ * React provider for the binder's active-state machine. Mounts inside the
+ * EngineProvider so it can wire `bus` from the engine.
+ */
+export function ActiveStateProvider(props: ActiveStateProviderProps) {
+  const [state, dispatch] = useReducer(reducer, EMPTY_ACTIVE_STATE);
+  const stateRef = useRef(state);
+  useEffect(() => {
+    stateRef.current = state;
+  }, [state]);
+
+  const focusTarget = useCallback(
+    (target: EvidenceTarget) => {
+      const previousTarget = stateRef.current.activeTarget;
+      const samePrevious =
+        previousTarget?.targetType === target.targetType &&
+        previousTarget?.targetId === target.targetId;
+      if (samePrevious) return;
+      props.bus.emit({
+        type: "FormFieldActivated",
+        target,
+        ...(previousTarget !== null ? { previousTarget } : {}),
+      });
+      dispatch({ type: "focus-target", target });
+    },
+    [props.bus],
+  );
+
+  const setActiveEvidence = useCallback(
+    (evidenceItemId: EvidenceItemId, annotationId?: AnnotationId | null) => {
+      props.bus.emit({
+        type: "EvidenceItemActivated",
+        evidenceItemId,
+        source: "form-field",
+      });
+      dispatch({
+        type: "set-active-evidence",
+        evidenceItemId,
+        annotationId: annotationId ?? null,
+      });
+    },
+    [props.bus],
+  );
+
+  const clear = useCallback(() => {
+    dispatch({ type: "clear" });
+  }, []);
+
+  const value = useMemo<ActiveStateApi>(
+    () => ({ state, focusTarget, setActiveEvidence, clear }),
+    [state, focusTarget, setActiveEvidence, clear],
+  );
+
+  return createElement(ActiveStateContext.Provider, { value }, props.children);
+}
+
+export function useActiveState(): ActiveStateApi {
+  const ctx = useContext(ActiveStateContext);
+  if (!ctx) {
+    throw new Error("useActiveState must be used inside <ActiveStateProvider />");
+  }
+  return ctx;
+}
+
+/**
+ * Pure reducer + initial state, exported so the headless tests can verify
+ * transitions without spinning up React.
+ */
+export const __test = { reducer, EMPTY_ACTIVE_STATE };

src/binder/state/index.ts

@@ -0,0 +1 @@
+export * from "./active";

src/binder/visual-guide/Overlay.dom.test.tsx

@@ -0,0 +1,150 @@
+/**
+ * Overlay unit test (CE-WP-0003-T07).
+ *
+ * Verifies the SVG renders the right number of paths given the active
+ * triple state and registered rects. Curve geometry is not asserted —
+ * the bezier helper is intentionally simple and changes will be caught
+ * by visual review, not test maintenance.
+ */
+
+// @vitest-environment happy-dom
+
+import { act, cleanup, render } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+
+import { createEventBus } from "@engine/events";
+
+import { Overlay } from "./Overlay";
+import { ActiveStateProvider, useActiveState } from "../state/active";
+import {
+  RectRegistryProvider,
+  createRectRegistryContextValue,
+  type RectRegistryContextValue,
+} from "./react-hooks";
+import type { EvidenceTarget } from "@shared/evidence-link";
+import type { AnnotationId, EvidenceItemId } from "@shared/ids";
+
+function fakeRect(x: number, y: number, w: number, h: number): DOMRect {
+  return {
+    x, y, width: w, height: h,
+    top: y, left: x, right: x + w, bottom: y + h,
+    toJSON() { return { x, y, width: w, height: h }; },
+  } as DOMRect;
+}
+
+const FIELD: EvidenceTarget = { targetType: "form-field", targetId: "summary" };
+const EV_ID = "ev_one" as EvidenceItemId;
+const ANN_ID = "ann_one" as AnnotationId;
+
+// Tiny harness to drive the binder's active-state from outside the
+// provider tree (so the test can stage state without a long click path).
+function Driver({ onActive }: { onActive: (api: ReturnType<typeof useActiveState>) => void }) {
+  const api = useActiveState();
+  onActive(api);
+  return null;
+}
+
+describe("Overlay (CE-WP-0003-T07)", () => {
+  let ctx: RectRegistryContextValue;
+
+  beforeEach(() => {
+    ctx = createRectRegistryContextValue();
+  });
+
+  afterEach(() => {
+    ctx.observer.disconnect();
+    cleanup();
+  });
+
+  it("renders nothing when no triple is active", () => {
+    const bus = createEventBus();
+    const { container } = render(
+      <RectRegistryProvider value={ctx}>
+        <ActiveStateProvider bus={bus}>
+          <Overlay />
+        </ActiveStateProvider>
+      </RectRegistryProvider>,
+    );
+    expect(container.querySelector("svg")).toBeNull();
+  });
+
+  it("draws one path when only field + card rects are registered", async () => {
+    const bus = createEventBus();
+    let api: ReturnType<typeof useActiveState> | null = null;
+    render(
+      <RectRegistryProvider value={ctx}>
+        <ActiveStateProvider bus={bus}>
+          <Driver onActive={(a) => (api = a)} />
+          <Overlay />
+        </ActiveStateProvider>
+      </RectRegistryProvider>,
+    );
+
+    // Register the two known rects.
+    ctx.registry.register("field", FIELD.targetId, () => fakeRect(10, 10, 100, 30));
+    ctx.registry.register("evidence-card", EV_ID, () => fakeRect(400, 200, 150, 60));
+
+    // Activate the triple. annotationId left null so no highlight is queried.
+    await act(async () => {
+      api!.focusTarget(FIELD);
+      api!.setActiveEvidence(EV_ID, null);
+    });
+
+    const svg = document.querySelector('[data-testid="visual-guide-overlay"]')!;
+    expect(svg).not.toBeNull();
+    expect(svg.getAttribute("data-path-count")).toBe("1");
+  });
+
+  it("draws two paths when field + card + highlight rects are all registered", async () => {
+    const bus = createEventBus();
+    let api: ReturnType<typeof useActiveState> | null = null;
+    render(
+      <RectRegistryProvider value={ctx}>
+        <ActiveStateProvider bus={bus}>
+          <Driver onActive={(a) => (api = a)} />
+          <Overlay />
+        </ActiveStateProvider>
+      </RectRegistryProvider>,
+    );
+
+    ctx.registry.register("field", FIELD.targetId, () => fakeRect(10, 10, 100, 30));
+    ctx.registry.register("evidence-card", EV_ID, () => fakeRect(400, 200, 150, 60));
+    ctx.registry.register("highlight", ANN_ID, () => fakeRect(700, 400, 200, 20));
+
+    await act(async () => {
+      api!.focusTarget(FIELD);
+      api!.setActiveEvidence(EV_ID, ANN_ID);
+    });
+
+    const svg = document.querySelector('[data-testid="visual-guide-overlay"]')!;
+    expect(svg.getAttribute("data-path-count")).toBe("2");
+    expect(svg.querySelectorAll("path").length).toBe(2);
+  });
+
+  it("re-renders when the registry invalidates after rect changes", async () => {
+    const bus = createEventBus();
+    let api: ReturnType<typeof useActiveState> | null = null;
+    render(
+      <RectRegistryProvider value={ctx}>
+        <ActiveStateProvider bus={bus}>
+          <Driver onActive={(a) => (api = a)} />
+          <Overlay />
+        </ActiveStateProvider>
+      </RectRegistryProvider>,
+    );
+    ctx.registry.register("field", FIELD.targetId, () => fakeRect(0, 0, 10, 10));
+    ctx.registry.register("evidence-card", EV_ID, () => fakeRect(100, 100, 10, 10));
+    await act(async () => {
+      api!.focusTarget(FIELD);
+      api!.setActiveEvidence(EV_ID, null);
+    });
+    const d1 = document.querySelector('[data-testid="visual-guide-overlay"] path')!.getAttribute("d");
+    // Mutate one of the getters' results, then invalidate.
+    ctx.registry.register("field", FIELD.targetId, () => fakeRect(500, 500, 10, 10));
+    await act(async () => {
+      ctx.registry.invalidate();
+    });
+    const d2 = document.querySelector('[data-testid="visual-guide-overlay"] path')!.getAttribute("d");
+    expect(d1).not.toBe(d2);
+  });
+});

src/binder/visual-guide/Overlay.tsx

@@ -0,0 +1,115 @@
+/**
+ * Visual-guide overlay — draws curves between the active triple.
+ *
+ * Subscribes to the rect registry + active-state machine and redraws a
+ * pair of bezier curves on every rect-change event:
+ *
+ *     field  ──►  evidence-card  ──►  highlight
+ *
+ * Throttling: `attachRectChangePumps` already coalesces scroll/resize
+ * bursts into one `rect-changed` per animation frame. The overlay's
+ * `useSyncExternalStore` subscription via `useRectRegistryVersion` picks
+ * up that single tick and React re-renders once per frame.
+ *
+ * Active-only: only the currently active triple is drawn. If any leg's
+ * rect is missing (e.g. the viewer hasn't reported a highlight rect for
+ * the active annotation yet), that leg is omitted but the other one
+ * still renders.
+ *
+ * MVP-sufficient. Future polish: easing the curve direction by source
+ * type, animating the transition between active states, dimming
+ * non-active rects rather than hiding them.
+ */
+
+import { useMemo } from "react";
+
+import { useActiveState } from "../state/active";
+import {
+  useRectRegistryContext,
+  useRectRegistryVersion,
+} from "./react-hooks";
+
+function rectCenter(rect: DOMRect): { x: number; y: number } {
+  return { x: rect.left + rect.width / 2, y: rect.top + rect.height / 2 };
+}
+
+/**
+ * Build a quadratic bezier from `a` to `b` whose control point bulges
+ * horizontally between them. The horizontal-bulge style is right for a
+ * left-pane→centre-pane→right-pane layout; vertical-bulge can be added
+ * later when we have a layout that needs it.
+ */
+function bezierPath(a: { x: number; y: number }, b: { x: number; y: number }): string {
+  const dx = b.x - a.x;
+  const cpx = a.x + dx / 2;
+  return `M ${a.x} ${a.y} Q ${cpx} ${a.y} ${(a.x + b.x) / 2} ${(a.y + b.y) / 2} T ${b.x} ${b.y}`;
+}
+
+export interface OverlayProps {
+  /** Curve stroke colour. Defaults to the engine's accent blue. */
+  readonly strokeColor?: string;
+  /** Curve stroke width. Defaults to 2px. */
+  readonly strokeWidth?: number;
+  /** Optional className for styling hooks; the inline styles cover layout. */
+  readonly className?: string;
+}
+
+export function Overlay({
+  strokeColor = "#0050b3",
+  strokeWidth = 2,
+  className,
+}: OverlayProps = {}) {
+  const { state } = useActiveState();
+  const { registry } = useRectRegistryContext();
+  const version = useRectRegistryVersion();
+
+  const paths = useMemo<readonly string[]>(() => {
+    if (!state.activeTarget || !state.activeEvidenceItemId) return [];
+    const fieldRect = registry.getRect("field", state.activeTarget.targetId);
+    const cardRect = registry.getRect("evidence-card", state.activeEvidenceItemId);
+    const highlightRect = state.activeAnnotationId
+      ? registry.getRect("highlight", state.activeAnnotationId)
+      : null;
+    const out: string[] = [];
+    if (fieldRect && cardRect) {
+      out.push(bezierPath(rectCenter(fieldRect), rectCenter(cardRect)));
+    }
+    if (cardRect && highlightRect) {
+      out.push(bezierPath(rectCenter(cardRect), rectCenter(highlightRect)));
+    }
+    void version; // memo invalidator
+    return out;
+  }, [state, registry, version]);
+
+  if (paths.length === 0) return null;
+
+  return (
+    <svg
+      data-testid="visual-guide-overlay"
+      data-active-target={state.activeTarget?.targetId ?? ""}
+      data-active-evidence={state.activeEvidenceItemId ?? ""}
+      data-path-count={String(paths.length)}
+      className={className}
+      style={{
+        position: "fixed",
+        top: 0,
+        left: 0,
+        width: "100vw",
+        height: "100vh",
+        pointerEvents: "none",
+        zIndex: 9999,
+      }}
+    >
+      {paths.map((d, i) => (
+        <path
+          key={i}
+          d={d}
+          stroke={strokeColor}
+          strokeWidth={strokeWidth}
+          fill="none"
+          strokeLinecap="round"
+        />
+      ))}
+    </svg>
+  );
+}

src/binder/visual-guide/events.ts

@@ -0,0 +1,118 @@
+/**
+ * Browser-level rect-change pumps.
+ *
+ * The rect registry holds `getRect` callbacks but doesn't observe the DOM
+ * itself. This module wires the four global change sources from
+ * `wiki/SharedContracts.md` §7 ("scroll, resize, focus, and
+ * active-evidence change") into a single `registry.invalidate()` call.
+ *
+ * Active-evidence change is fired imperatively by the binder service when
+ * it calls `setActiveEvidence` — see `services/bindings.ts`.
+ *
+ * SSR-safe: every API checks `typeof window !== "undefined"` and is a
+ * no-op when the DOM isn't available, so tests that import this module
+ * under Node never crash.
+ */
+
+import type { RectRegistry } from "./rect-registry";
+
+export interface RectChangeObserverOptions {
+  /**
+   * Throttle invalidations to a single requestAnimationFrame; otherwise a
+   * fast scroll event burst causes the overlay to redraw on every pixel.
+   * Defaults to true. Tests pass `false` for deterministic synchronous
+   * behaviour.
+   */
+  readonly throttle?: boolean;
+}
+
+export interface RectChangeObserverHandle {
+  /**
+   * Begin watching a DOM element. The registry is notified of any
+   * scroll/resize/focus event that bubbles to the ancestor chain or fires
+   * on the element itself. Returns a cleanup that stops watching.
+   */
+  observe(element: Element): () => void;
+  /** Tear down all observers + global listeners. */
+  disconnect(): void;
+}
+
+/**
+ * Attach scroll/resize/focus pumps to the given registry. Returns an
+ * observer handle so per-element ResizeObservers can be cleaned up by
+ * the components that registered them.
+ */
+export function attachRectChangePumps(
+  registry: RectRegistry,
+  options: RectChangeObserverOptions = {},
+): RectChangeObserverHandle {
+  const throttle = options.throttle ?? true;
+
+  if (typeof window === "undefined") {
+    return {
+      observe: () => () => {},
+      disconnect: () => {},
+    };
+  }
+
+  let pending = false;
+
+  function invalidate() {
+    if (!throttle) {
+      registry.invalidate();
+      return;
+    }
+    if (pending) return;
+    pending = true;
+    requestAnimationFrame(() => {
+      pending = false;
+      registry.invalidate();
+    });
+  }
+
+  const onScroll = invalidate;
+  const onResize = invalidate;
+  const onFocusIn = invalidate;
+
+  // capture-phase scroll catches scrolling in any nested scroll container,
+  // not just the document — needed for the PDF viewer's inner scroller.
+  window.addEventListener("scroll", onScroll, { passive: true, capture: true });
+  window.addEventListener("resize", onResize, { passive: true });
+  document.addEventListener("focusin", onFocusIn);
+
+  // One global ResizeObserver shared across observed elements is cheaper
+  // than per-element observers but loses the per-element resolution; we
+  // don't need per-element resolution because invalidations are global.
+  const ro: ResizeObserver | null =
+    typeof ResizeObserver !== "undefined" ? new ResizeObserver(invalidate) : null;
+
+  // IntersectionObserver fires when an element moves into/out of the
+  // viewport — useful for the highlight which may scroll off-screen.
+  const io: IntersectionObserver | null =
+    typeof IntersectionObserver !== "undefined"
+      ? new IntersectionObserver(invalidate, { threshold: [0, 1] })
+      : null;
+
+  const observedElements = new Set<Element>();
+
+  return {
+    observe(element) {
+      observedElements.add(element);
+      ro?.observe(element);
+      io?.observe(element);
+      return () => {
+        observedElements.delete(element);
+        ro?.unobserve(element);
+        io?.unobserve(element);
+      };
+    },
+    disconnect() {
+      window.removeEventListener("scroll", onScroll, { capture: true } as EventListenerOptions);
+      window.removeEventListener("resize", onResize);
+      document.removeEventListener("focusin", onFocusIn);
+      ro?.disconnect();
+      io?.disconnect();
+      observedElements.clear();
+    },
+  };
+}

src/binder/visual-guide/index.ts

@@ -0,0 +1,4 @@
+export * from "./rect-registry";
+export * from "./events";
+export * from "./react-hooks";
+export { Overlay, type OverlayProps } from "./Overlay";

src/binder/visual-guide/react-hooks.dom.test.tsx

@@ -0,0 +1,152 @@
+/**
+ * happy-dom-level test for the rect registry React hooks.
+ *
+ * Verifies the full §7 contract under realistic conditions:
+ *   - useRegisterRect attaches a getRect callback bound to the
+ *     element's getBoundingClientRect
+ *   - mutating the element's rect produces fresh values via getRect
+ *   - scroll/resize events on window fan out to a registry invalidate
+ *   - useRectRegistryVersion bumps each time the registry emits
+ */
+
+// @vitest-environment happy-dom
+
+import { act, render } from "@testing-library/react";
+import { useRef } from "react";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+
+import {
+  RectRegistryProvider,
+  createRectRegistryContextValue,
+  useRectRegistryContext,
+  useRectRegistryVersion,
+  useRegisterRect,
+} from "./react-hooks";
+import type { RectRegistryEvent } from "./rect-registry";
+
+function FieldUnderTest({
+  id,
+  onVersion,
+}: {
+  id: string;
+  onVersion?: (v: number) => void;
+}) {
+  const ref = useRef<HTMLDivElement>(null);
+  useRegisterRect("field", id, ref);
+  const version = useRectRegistryVersion();
+  onVersion?.(version);
+  return <div ref={ref} data-testid={`f-${id}`} />;
+}
+
+function CtxSpy({ onCtx }: { onCtx: (registry: ReturnType<typeof useRectRegistryContext>) => void }) {
+  const ctx = useRectRegistryContext();
+  onCtx(ctx);
+  return null;
+}
+
+describe("useRegisterRect (happy-dom)", () => {
+  let ctxValue: ReturnType<typeof createRectRegistryContextValue>;
+
+  beforeEach(() => {
+    ctxValue = createRectRegistryContextValue();
+  });
+
+  afterEach(() => {
+    ctxValue.observer.disconnect();
+  });
+
+  it("registers the element's getBoundingClientRect and unregisters on unmount", () => {
+    const events: RectRegistryEvent[] = [];
+    ctxValue.registry.subscribe((e) => events.push(e));
+
+    const { unmount } = render(
+      <RectRegistryProvider value={ctxValue}>
+        <FieldUnderTest id="summary" />
+      </RectRegistryProvider>,
+    );
+
+    expect(ctxValue.registry.getRect("field", "summary")).not.toBeNull();
+    expect(ctxValue.registry.list()).toEqual([{ kind: "field", id: "summary" }]);
+
+    unmount();
+
+    expect(ctxValue.registry.getRect("field", "summary")).toBeNull();
+    expect(events.map((e) => e.type)).toContain("unregistered");
+  });
+
+  it("getRect reflects mutated bounding rects", () => {
+    let getter: () => DOMRect | null = () => null;
+    // Spy on the registered callback by hijacking register
+    const realRegister = ctxValue.registry.register;
+    ctxValue.registry.register = (kind, id, fn) => {
+      getter = fn;
+      return realRegister.call(ctxValue.registry, kind, id, fn);
+    };
+
+    render(
+      <RectRegistryProvider value={ctxValue}>
+        <FieldUnderTest id="amount" />
+      </RectRegistryProvider>,
+    );
+
+    // happy-dom returns a DOMRect with all zeros by default. Patch the
+    // element's getBoundingClientRect and verify the registered callback
+    // forwards the new rect.
+    const el = document.querySelector('[data-testid="f-amount"]') as HTMLDivElement;
+    el.getBoundingClientRect = () => ({
+      x: 11,
+      y: 22,
+      width: 33,
+      height: 44,
+      top: 22,
+      left: 11,
+      right: 11 + 33,
+      bottom: 22 + 44,
+      toJSON() {
+        return {};
+      },
+    });
+
+    const rect = getter();
+    expect(rect).not.toBeNull();
+    expect(rect!.x).toBe(11);
+    expect(rect!.width).toBe(33);
+  });
+
+  it("useRectRegistryVersion bumps on register and on invalidate", async () => {
+    const seen: number[] = [];
+    const renderResult = render(
+      <RectRegistryProvider value={ctxValue}>
+        <FieldUnderTest
+          id="bumpy"
+          onVersion={(v) => seen.push(v)}
+        />
+      </RectRegistryProvider>,
+    );
+
+    // Wait one microtask for effects to flush.
+    await act(async () => {});
+
+    const beforeInvalidate = seen[seen.length - 1]!;
+    await act(async () => {
+      ctxValue.registry.invalidate();
+    });
+    const afterInvalidate = seen[seen.length - 1]!;
+    expect(afterInvalidate).toBeGreaterThan(beforeInvalidate);
+
+    renderResult.unmount();
+  });
+
+  it("exposes the same registry across consumers in the provider subtree", () => {
+    let firstCtx: ReturnType<typeof useRectRegistryContext> | undefined;
+    let secondCtx: ReturnType<typeof useRectRegistryContext> | undefined;
+    render(
+      <RectRegistryProvider value={ctxValue}>
+        <CtxSpy onCtx={(c) => (firstCtx = c)} />
+        <CtxSpy onCtx={(c) => (secondCtx = c)} />
+      </RectRegistryProvider>,
+    );
+    expect(firstCtx).toBe(secondCtx);
+    expect(firstCtx?.registry).toBe(ctxValue.registry);
+  });
+});

src/binder/visual-guide/react-hooks.ts

@@ -0,0 +1,98 @@
+/**
+ * React hooks for the rect registry.
+ *
+ * Components mount, get a ref to a DOM node, and ask the registry to
+ * track it via `useRegisterRect(kind, id, ref)`. Unmount/ref-change
+ * unregisters automatically.
+ *
+ * The registry itself lives behind a React context so multiple subtrees
+ * can share one registry (the overlay sees what every renderer publishes).
+ */
+
+import {
+  createContext,
+  useCallback,
+  useContext,
+  useEffect,
+  useSyncExternalStore,
+  type RefObject,
+} from "react";
+
+import {
+  createRectRegistry,
+  type RectKind,
+  type RectRegistry,
+} from "./rect-registry";
+import { attachRectChangePumps, type RectChangeObserverHandle } from "./events";
+
+export interface RectRegistryContextValue {
+  readonly registry: RectRegistry;
+  readonly observer: RectChangeObserverHandle;
+}
+
+const RectRegistryContext = createContext<RectRegistryContextValue | null>(null);
+
+/**
+ * Create an isolated registry + change pump pair for tests or app
+ * composition roots that wire their own provider.
+ */
+export function createRectRegistryContextValue(): RectRegistryContextValue {
+  const registry = createRectRegistry();
+  const observer = attachRectChangePumps(registry);
+  return { registry, observer };
+}
+
+export function useRectRegistryContext(): RectRegistryContextValue {
+  const ctx = useContext(RectRegistryContext);
+  if (!ctx) {
+    throw new Error(
+      "useRectRegistryContext must be used inside <RectRegistryProvider />",
+    );
+  }
+  return ctx;
+}
+
+export const RectRegistryProvider = RectRegistryContext.Provider;
+
+/**
+ * Register a DOM ref's bounding rect with the registry.
+ *
+ * Re-runs when `kind`/`id`/`ref.current` change. The observer also starts
+ * watching the element for scroll/resize so the overlay can re-query
+ * without polling.
+ */
+export function useRegisterRect(
+  kind: RectKind,
+  id: string,
+  ref: RefObject<Element | null>,
+): void {
+  const { registry, observer } = useRectRegistryContext();
+  useEffect(() => {
+    const el = ref.current;
+    if (!el) return;
+    const unregister = registry.register(kind, id, () => el.getBoundingClientRect());
+    const unobserve = observer.observe(el);
+    return () => {
+      unobserve();
+      unregister();
+    };
+  }, [kind, id, ref, registry, observer]);
+}
+
+/**
+ * Subscribe to registry change events from inside React. Returns a
+ * monotonically-increasing version number that bumps on every event, so
+ * `useMemo`/`useEffect` deps can include it to re-derive cached values.
+ *
+ * Implementation: leans on `registry.getVersion()` for the snapshot so
+ * `useSyncExternalStore` doesn't accumulate per-render subscribers.
+ */
+export function useRectRegistryVersion(): number {
+  const { registry } = useRectRegistryContext();
+  const subscribe = useCallback(
+    (callback: () => void) => registry.subscribe(callback),
+    [registry],
+  );
+  const getSnapshot = useCallback(() => registry.getVersion(), [registry]);
+  return useSyncExternalStore(subscribe, getSnapshot, () => 0);
+}

src/binder/visual-guide/rect-registry.test.ts

@@ -0,0 +1,151 @@
+/**
+ * Rect registry unit tests — exercise every public surface plus the
+ * §7-contract guarantees:
+ *   - register/unregister fire subscriber events
+ *   - getRect returns the live result of the registered callback
+ *   - invalidate fires a global `rect-changed` event
+ *   - version bumps on every emit
+ *   - re-registering the same (kind,id) supersedes the prior callback;
+ *     the stale unregister cleanup does not delete the new entry.
+ */
+
+import { describe, expect, it } from "vitest";
+
+import {
+  createRectRegistry,
+  type RectRegistryEvent,
+} from "./rect-registry";
+
+function fakeRect(x: number, y: number, w: number, h: number): DOMRect {
+  // happy-dom/jsdom isn't loaded for this test — synth a DOMRect-shaped
+  // object. The registry contract only reads these properties.
+  return {
+    x,
+    y,
+    width: w,
+    height: h,
+    top: y,
+    left: x,
+    right: x + w,
+    bottom: y + h,
+    toJSON() {
+      return { x, y, width: w, height: h };
+    },
+  } as DOMRect;
+}
+
+describe("createRectRegistry", () => {
+  it("returns null for unknown rects", () => {
+    const r = createRectRegistry();
+    expect(r.getRect("field", "missing")).toBeNull();
+  });
+
+  it("register/getRect roundtrip", () => {
+    const r = createRectRegistry();
+    r.register("field", "f1", () => fakeRect(1, 2, 3, 4));
+    const rect = r.getRect("field", "f1");
+    expect(rect).not.toBeNull();
+    expect(rect!.x).toBe(1);
+    expect(rect!.width).toBe(3);
+  });
+
+  it("getRect reflects live callback results", () => {
+    const r = createRectRegistry();
+    let xPos = 10;
+    r.register("highlight", "h1", () => fakeRect(xPos, 0, 5, 5));
+    expect(r.getRect("highlight", "h1")!.x).toBe(10);
+    xPos = 200;
+    expect(r.getRect("highlight", "h1")!.x).toBe(200);
+  });
+
+  it("returns null when the callback throws", () => {
+    const r = createRectRegistry();
+    r.register("field", "boom", () => {
+      throw new Error("nope");
+    });
+    expect(r.getRect("field", "boom")).toBeNull();
+  });
+
+  it("emits registered + unregistered events", () => {
+    const r = createRectRegistry();
+    const events: RectRegistryEvent[] = [];
+    r.subscribe((e) => events.push(e));
+    const unregister = r.register("evidence-card", "ev1", () => fakeRect(0, 0, 1, 1));
+    unregister();
+    expect(events).toEqual([
+      { type: "registered", kind: "evidence-card", id: "ev1" },
+      { type: "unregistered", kind: "evidence-card", id: "ev1" },
+    ]);
+  });
+
+  it("invalidate emits a global rect-changed event and bumps version", () => {
+    const r = createRectRegistry();
+    const events: RectRegistryEvent[] = [];
+    r.subscribe((e) => events.push(e));
+    const before = r.getVersion();
+    r.invalidate();
+    expect(events).toEqual([{ type: "rect-changed" }]);
+    expect(r.getVersion()).toBe(before + 1);
+  });
+
+  it("re-registering the same (kind,id) supersedes; stale cleanup is a no-op", () => {
+    const r = createRectRegistry();
+    const events: RectRegistryEvent[] = [];
+    r.subscribe((e) => events.push(e));
+
+    const firstGetRect = () => fakeRect(1, 1, 1, 1);
+    const secondGetRect = () => fakeRect(9, 9, 9, 9);
+
+    const cleanup1 = r.register("highlight", "x", firstGetRect);
+    r.register("highlight", "x", secondGetRect); // supersede
+
+    // The stale cleanup must not remove the new registration.
+    cleanup1();
+
+    expect(r.getRect("highlight", "x")!.x).toBe(9);
+    // Two `registered` events, no `unregistered` event — the second
+    // register overwrote without an explicit unregister, and the stale
+    // cleanup detected the (kind,id) holds a different callback.
+    expect(events.filter((e) => e.type === "unregistered")).toHaveLength(0);
+    expect(events.filter((e) => e.type === "registered")).toHaveLength(2);
+  });
+
+  it("subscribe returns an unsubscribe that detaches the listener", () => {
+    const r = createRectRegistry();
+    let count = 0;
+    const off = r.subscribe(() => count++);
+    r.invalidate();
+    off();
+    r.invalidate();
+    expect(count).toBe(1);
+  });
+
+  it("listener errors do not break sibling listeners", () => {
+    const r = createRectRegistry();
+    let okCount = 0;
+    r.subscribe(() => {
+      throw new Error("boom");
+    });
+    r.subscribe(() => {
+      okCount++;
+    });
+    r.invalidate();
+    expect(okCount).toBe(1);
+  });
+
+  it("list enumerates current registrations", () => {
+    const r = createRectRegistry();
+    r.register("field", "f1", () => null);
+    r.register("evidence-card", "ev1", () => null);
+    r.register("highlight", "h1", () => null);
+    const list = r.list();
+    expect(list).toHaveLength(3);
+    expect(list).toEqual(
+      expect.arrayContaining([
+        { kind: "field", id: "f1" },
+        { kind: "evidence-card", id: "ev1" },
+        { kind: "highlight", id: "h1" },
+      ]),
+    );
+  });
+});

src/engine/events/types.ts

@@ -11,10 +11,15 @@
 import type { Annotation, AnnotationResolutionStatus } from "@shared/annotation";
 import type { Document, DocumentRepresentation } from "@shared/document";
 import type { EvidenceItem, EvidenceItemStatus } from "@shared/evidence";
+import type {
+  EvidenceLink,
+  EvidenceTarget,
+} from "@shared/evidence-link";
 import type {
   AnnotationId,
   DocumentId,
   EvidenceItemId,
+  EvidenceLinkId,
   RepresentationId,
 } from "@shared/ids";
 
@@ -69,6 +74,24 @@ export interface EvidenceItemActivatedEvent {
   readonly source?: "sidebar" | "form-field" | "citation-card";
 }
 
+export interface EvidenceLinkCreatedEvent {
+  readonly type: "EvidenceLinkCreated";
+  readonly linkId: EvidenceLinkId;
+  readonly link: EvidenceLink;
+}
+
+export interface EvidenceLinkUpdatedEvent {
+  readonly type: "EvidenceLinkUpdated";
+  readonly linkId: EvidenceLinkId;
+  readonly link: EvidenceLink;
+}
+
+export interface FormFieldActivatedEvent {
+  readonly type: "FormFieldActivated";
+  readonly target: EvidenceTarget;
+  readonly previousTarget?: EvidenceTarget;
+}
+
 export type EngineEvent =
   | DocumentImportedEvent
   | DocumentRepresentationGeneratedEvent
@@ -77,7 +100,10 @@ export type EngineEvent =
   | AnnotationResolutionFailedEvent
   | EvidenceItemCreatedEvent
   | EvidenceItemUpdatedEvent
-  | EvidenceItemActivatedEvent;
+  | EvidenceItemActivatedEvent
+  | EvidenceLinkCreatedEvent
+  | EvidenceLinkUpdatedEvent
+  | FormFieldActivatedEvent;
 
 export type EngineEventType = EngineEvent["type"];
 

src/shared/evidence-link.test.ts

@@ -0,0 +1,62 @@
+/**
+ * Conformance test: the runtime enum lists in `evidence-link.ts` must
+ * match the lists in `wiki/SharedContracts.md` §2.4 and §2.5 exactly.
+ *
+ * If you intentionally change an enum, update both the doc and the
+ * runtime list together — this test will tell you which one you forgot.
+ */
+
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import { describe, expect, it } from "vitest";
+
+import {
+  EVIDENCE_LINK_STATUS_VALUES,
+  EVIDENCE_RELATION_VALUES,
+} from "./evidence-link";
+
+const HERE = fileURLToPath(new URL(".", import.meta.url));
+const CONTRACTS_PATH = resolve(HERE, "../../wiki/SharedContracts.md");
+
+function extractFencedListAfterHeading(markdown: string, heading: string): string[] {
+  const headingIndex = markdown.indexOf(heading);
+  if (headingIndex === -1) {
+    throw new Error(`Could not find heading "${heading}" in SharedContracts.md`);
+  }
+  const after = markdown.slice(headingIndex + heading.length);
+  const fenceOpen = after.indexOf("```");
+  if (fenceOpen === -1) throw new Error(`No fenced block after "${heading}"`);
+  const bodyStart = after.indexOf("\n", fenceOpen) + 1;
+  const fenceClose = after.indexOf("```", bodyStart);
+  if (fenceClose === -1) throw new Error(`Unterminated fenced block after "${heading}"`);
+  const body = after.slice(bodyStart, fenceClose);
+  return body
+    .split("\n")
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0)
+    // Strip trailing "  — explanatory note" if present (none in §2.4/§2.5 today,
+    // but §2.1/§2.2 use that style — being defensive keeps the helper reusable).
+    .map((line) => line.split(/\s+[—-]\s+/)[0]!.trim());
+}
+
+describe("EvidenceLink enum conformance with SharedContracts.md", () => {
+  const markdown = readFileSync(CONTRACTS_PATH, "utf8");
+
+  it("§2.4 EvidenceLink.status matches EVIDENCE_LINK_STATUS_VALUES", () => {
+    const docValues = extractFencedListAfterHeading(
+      markdown,
+      "### 2.4 `EvidenceLink.status` (per target)",
+    );
+    expect(docValues).toEqual([...EVIDENCE_LINK_STATUS_VALUES]);
+  });
+
+  it("§2.5 EvidenceLink.relation matches EVIDENCE_RELATION_VALUES", () => {
+    const docValues = extractFencedListAfterHeading(
+      markdown,
+      "### 2.5 `EvidenceLink.relation`",
+    );
+    expect(docValues).toEqual([...EVIDENCE_RELATION_VALUES]);
+  });
+});

src/shared/evidence-link.ts

@@ -0,0 +1,107 @@
+/**
+ * EvidenceLink + EvidenceTarget shapes.
+ *
+ * Implements `wiki/SharedContracts.md` §1 (vocabulary), §2.4
+ * (EvidenceLink.status) and §2.5 (EvidenceLink.relation), and
+ * `wiki/ArchitectureOverview.md` §4 (target-type catalogue).
+ *
+ * An EvidenceLink ties exactly one EvidenceItem to one structured target
+ * (e.g. a form field). Multiple links per item are allowed when the same
+ * evidence supports several targets. Multiple links per target are allowed
+ * when several pieces of evidence apply to the same field — the
+ * EvidenceSet captures that ordered group.
+ */
+
+import type { EvidenceItemId, EvidenceLinkId } from "./ids";
+
+/**
+ * Closed enum per `wiki/SharedContracts.md` §2.4.
+ *
+ * `no-evidence` is a *derived* state — computed when a target has zero
+ * links — and is therefore NOT stored on a link itself. The stored values
+ * are the five members of `EvidenceLinkStoredStatus`.
+ */
+export type EvidenceLinkStatus =
+  | "no-evidence"
+  | "candidate"
+  | "confirmed"
+  | "conflicting"
+  | "insufficient"
+  | "verified";
+
+/**
+ * The subset of `EvidenceLinkStatus` that may appear on a stored link
+ * record. `no-evidence` is excluded because it is derived from the
+ * absence of links on a target, not stored.
+ */
+export type EvidenceLinkStoredStatus = Exclude<EvidenceLinkStatus, "no-evidence">;
+
+/** Closed enum per `wiki/SharedContracts.md` §2.5. */
+export type EvidenceRelation =
+  | "supports"
+  | "contradicts"
+  | "explains"
+  | "qualifies"
+  | "source-for"
+  | "context-for";
+
+/**
+ * Known target-type catalogue per `wiki/ArchitectureOverview.md` §4
+ * (`EvidenceTargetType`). The MVP only exercises `"form-field"`; the
+ * others are reserved so future workplans can extend without renaming.
+ */
+export type EvidenceTargetType =
+  | "form-field"
+  | "claim"
+  | "requirement"
+  | "decision"
+  | "document-section";
+
+/**
+ * Generic shape of an evidence target. `targetId` is opaque to the engine
+ * — the host subsystem (form renderer, claims index, …) owns the
+ * namespace for its `targetType`.
+ */
+export interface EvidenceTarget {
+  readonly targetType: EvidenceTargetType;
+  readonly targetId: string;
+}
+
+export interface EvidenceLink {
+  readonly id: EvidenceLinkId;
+  readonly evidenceItemId: EvidenceItemId;
+  readonly targetType: EvidenceTargetType;
+  readonly targetId: string;
+  readonly relation: EvidenceRelation;
+  readonly status: EvidenceLinkStoredStatus;
+  /** Optional 0..1 confidence assigned by user or auto-process. */
+  readonly confidence?: number;
+  readonly createdBy?: string;
+  /** ISO-8601 timestamp. */
+  readonly createdAt: string;
+  /** ISO-8601 timestamp. */
+  readonly updatedAt: string;
+}
+
+/**
+ * The canonical lists, exported for use by enum-conformance tests
+ * (see `evidence-link.test.ts`) and for any UI code that needs to
+ * enumerate options. Order matches `wiki/SharedContracts.md`.
+ */
+export const EVIDENCE_LINK_STATUS_VALUES: readonly EvidenceLinkStatus[] = [
+  "no-evidence",
+  "candidate",
+  "confirmed",
+  "conflicting",
+  "insufficient",
+  "verified",
+];
+
+export const EVIDENCE_RELATION_VALUES: readonly EvidenceRelation[] = [
+  "supports",
+  "contradicts",
+  "explains",
+  "qualifies",
+  "source-for",
+  "context-for",
+];

src/shared/evidence-set.ts

@@ -0,0 +1,36 @@
+/**
+ * EvidenceSet — an ordered group of evidence items pointed at a target.
+ *
+ * Implements `wiki/SharedContracts.md` §1 (vocabulary) and
+ * `wiki/ArchitectureOverview.md` §4.6.
+ *
+ * The set itself is target-shaped: it carries the `(targetType, targetId)`
+ * pair so the binder can answer "give me the EvidenceSet for this form
+ * field" in one call. `activeEvidenceItemId` is the membership of the
+ * set that the UI is currently focused on; cycling Tab/Shift-Tab through
+ * the field's chips updates it.
+ */
+
+import type { EvidenceItemId, EvidenceSetId } from "./ids";
+import type { EvidenceTargetType } from "./evidence-link";
+
+export interface EvidenceSet {
+  readonly id: EvidenceSetId;
+  readonly label?: string;
+  /**
+   * Optional target binding. Form-field sets always carry these; ad-hoc
+   * topical sets may leave them undefined.
+   */
+  readonly targetType?: EvidenceTargetType;
+  readonly targetId?: string;
+  /**
+   * Membership in display order. The binder is free to reorder, but
+   * persistence preserves this order so cycling is deterministic.
+   */
+  readonly evidenceItemIds: readonly EvidenceItemId[];
+  /**
+   * The currently active member, or undefined if the set is empty or
+   * no member is yet focused.
+   */
+  readonly activeEvidenceItemId?: EvidenceItemId;
+}

src/shared/index.ts

@@ -3,4 +3,6 @@ export * from "./document";
 export * from "./selector";
 export * from "./annotation";
 export * from "./evidence";
+export * from "./evidence-link";
+export * from "./evidence-set";
 export { normalize, NORMALIZE_VERSION } from "./text/normalize";

src/work/EngineContext.tsx

@@ -217,3 +217,18 @@ export function useScrollToAnnotation(): {
     scrollTo: ctx.scrollToAnnotation,
   };
 }
+
+/**
+ * Track the most-recent `EvidenceItemActivated` event id from the engine
+ * bus. Returns `null` until something is activated. UI components that
+ * highlight "the active evidence" subscribe via this hook so they don't
+ * need to import the binder's active-state machine directly.
+ */
+export function useLastActivatedEvidence(): import("@shared/ids").EvidenceItemId | null {
+  const engine = useEngine();
+  const [id, setId] = useState<import("@shared/ids").EvidenceItemId | null>(null);
+  useEffect(() => {
+    return engine.bus.on("EvidenceItemActivated", (e) => setId(e.evidenceItemId));
+  }, [engine]);
+  return id;
+}

src/work/EvidenceSidebar.tsx

@@ -16,6 +16,7 @@ import {
   useActiveDocument,
   useEngine,
   useEngineEventTick,
+  useLastActivatedEvidence,
   useScrollToAnnotation,
 } from "./EngineContext";
 
@@ -27,6 +28,7 @@ export function EvidenceSidebar(props: EvidenceSidebarProps) {
   const engine = useEngine();
   const { document } = useActiveDocument();
   const { scrollTo } = useScrollToAnnotation();
+  const activeId = useLastActivatedEvidence();
 
   // Refresh the list when items are created or updated. The tick values are
   // included in the memo deps below so the list re-resolves on each event.
@@ -64,6 +66,7 @@ export function EvidenceSidebar(props: EvidenceSidebarProps) {
           const firstAnnotationId = item.annotationIds[0];
           const annotation = firstAnnotationId ? engine.annotations.get(firstAnnotationId) : null;
           const quote = annotation?.quote ?? "(no quote)";
+          const isActive = activeId === item.id;
           return (
             <li key={item.id} style={{ marginBottom: 8 }}>
               <button
@@ -72,12 +75,13 @@ export function EvidenceSidebar(props: EvidenceSidebarProps) {
                   if (firstAnnotationId) scrollTo(firstAnnotationId);
                   props.onActivate?.(item);
                 }}
+                aria-current={isActive ? "true" : undefined}
                 style={{
                   display: "block",
                   width: "100%",
                   textAlign: "left",
-                  background: "#fff8d6",
-                  border: "1px solid #e0c050",
+                  background: isActive ? "#e8f0ff" : "#fff8d6",
+                  border: isActive ? "2px solid #0050b3" : "1px solid #e0c050",
                   padding: 8,
                   cursor: "pointer",
                   fontSize: 12,

src/work/index.ts

@@ -8,6 +8,8 @@ export {
   useActiveDocument,
   useActiveDocumentId,
   useEngineEventTick,
+  useLastActivatedEvidence,
   usePendingSelection,
+  useScrollToAnnotation,
   type PendingSelection,
 } from "./EngineContext";

tests/integration/forms-active-cycling.dom.test.tsx

@@ -0,0 +1,224 @@
+/**
+ * CE-WP-0003-T06 integration — focusing a field auto-activates its first
+ * linked evidence, the chip is marked aria-current, and the ScrollBridge
+ * fires scrollTo on the viewer with the right annotation.
+ *
+ * Flow:
+ *   1. Review mode: open fixture, inject a selection capture, save the
+ *      evidence item (T09 pattern).
+ *   2. Switch to Forms mode.
+ *   3. Stage the saved evidence in the strip.
+ *   4. Click a field → BindingService creates a link.
+ *   5. Click the field again → ActiveStateProvider focuses target →
+ *      chip list re-derives → auto-activates first chip → ScrollBridge
+ *      calls scrollTo → mock viewer sees `scrollToAnnotationId`.
+ */
+
+// @vitest-environment happy-dom
+
+import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import type { Document, DocumentRepresentation } from "@shared/document";
+import type { DocumentId, RepresentationId } from "@shared/ids";
+import type { Selector } from "@shared/selector";
+
+import type { PdfSelectionCapture } from "@anchor/index";
+import manifest from "../../fixtures/pdfs/manifest.json" with { type: "json" };
+
+interface ViewerProps {
+  pdfUrl: string;
+  storedAnnotations: readonly { id: string; text: string; selectors: readonly Selector[] }[];
+  scrollToAnnotationId?: string;
+  onSelectionCaptured(capture: PdfSelectionCapture, selectors: Selector[]): void;
+}
+
+interface ViewerSnapshot {
+  pdfUrl: string | null;
+  scrollToAnnotationId: string | null;
+  onSelectionCaptured: ViewerProps["onSelectionCaptured"] | null;
+  storedAnnotationIds: string[];
+}
+
+const viewerSnapshot: ViewerSnapshot = {
+  pdfUrl: null,
+  scrollToAnnotationId: null,
+  onSelectionCaptured: null,
+  storedAnnotationIds: [],
+};
+
+vi.mock("@anchor/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@anchor/index")>();
+  const MockPdfSpikeViewer = (props: ViewerProps) => {
+    viewerSnapshot.pdfUrl = props.pdfUrl;
+    viewerSnapshot.scrollToAnnotationId = props.scrollToAnnotationId ?? null;
+    viewerSnapshot.onSelectionCaptured = props.onSelectionCaptured;
+    viewerSnapshot.storedAnnotationIds = props.storedAnnotations.map((a) => a.id);
+    return (
+      <div
+        data-testid="mock-pdf-viewer"
+        data-pdf-url={props.pdfUrl}
+        data-scroll-to={props.scrollToAnnotationId ?? ""}
+      />
+    );
+  };
+  return { ...original, PdfSpikeViewer: MockPdfSpikeViewer };
+});
+
+const FIXTURE = manifest.fixtures.find((f) => f.id === "fristsetzung-bezifferung")!;
+const SYNTHETIC_CANONICAL = [
+  "Pre quote.",
+  FIXTURE.known_good_quote,
+  "Post quote.",
+].join(" ");
+
+vi.mock("@source/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@source/index")>();
+  return {
+    ...original,
+    ingestPdf: vi.fn(async (_input: unknown, options?: { filename?: string }) => {
+      const documentId = ("doc_test_" + Math.random().toString(36).slice(2, 10)) as DocumentId;
+      const representationId = ("rep_test_" + Math.random().toString(36).slice(2, 10)) as RepresentationId;
+      const document: Document = {
+        id: documentId,
+        mediaType: "application/pdf",
+        ...(options?.filename ? { title: options.filename } : {}),
+        fingerprint: "synthetic-fingerprint-for-test",
+        createdAt: "2026-05-25T00:00:00.000Z",
+        updatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      const representation: DocumentRepresentation = {
+        id: representationId,
+        documentId,
+        representationType: "pdf-text",
+        contentHash: "synthetic-fingerprint-for-test",
+        canonicalText: SYNTHETIC_CANONICAL,
+        pageMap: [{ page: 1, width: 595, height: 842 }],
+        offsetMap: [
+          {
+            page: 1,
+            globalStart: 0,
+            globalEnd: SYNTHETIC_CANONICAL.length,
+            pageLength: SYNTHETIC_CANONICAL.length,
+          },
+        ],
+        generatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      return { document, representation };
+    }),
+  };
+});
+
+function syntheticCaptureFor(text: string, page: number): PdfSelectionCapture {
+  return {
+    kind: "pdf",
+    text,
+    page,
+    rects: [{ x: 0.1, y: 0.2, width: 0.4, height: 0.04 }],
+    boundingRect: { x: 0.1, y: 0.2, width: 0.4, height: 0.04 },
+  };
+}
+
+async function loadApp() {
+  const { App } = await import("@app/App");
+  return render(<App />);
+}
+
+function resetSnapshot() {
+  viewerSnapshot.pdfUrl = null;
+  viewerSnapshot.scrollToAnnotationId = null;
+  viewerSnapshot.onSelectionCaptured = null;
+  viewerSnapshot.storedAnnotationIds = [];
+}
+
+describe("FormsApp — active-evidence cycling (CE-WP-0003-T06)", () => {
+  beforeEach(() => {
+    resetSnapshot();
+    globalThis.localStorage?.clear();
+    globalThis.fetch = vi.fn(async () =>
+      new Response(new Uint8Array([0x25, 0x50, 0x44, 0x46]).buffer, {
+        status: 200,
+        headers: { "Content-Type": "application/pdf" },
+      }),
+    );
+    if (typeof window !== "undefined") {
+      history.replaceState(null, "", window.location.pathname);
+    }
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    cleanup();
+  });
+
+  it("focusing a linked field auto-activates the first evidence and bridges to viewer scroll", { timeout: 15000 }, async () => {
+    const user = userEvent.setup();
+    await loadApp();
+
+    // --- Review mode: create an evidence item via the captured-selection flow.
+    const fixtureBtn = screen.getByRole("button", { name: new RegExp(FIXTURE.id) });
+    await user.click(fixtureBtn);
+    await waitFor(() => expect(viewerSnapshot.onSelectionCaptured).not.toBeNull());
+    await act(async () => {
+      viewerSnapshot.onSelectionCaptured!(
+        syntheticCaptureFor(FIXTURE.known_good_quote, FIXTURE.known_good_quote_page),
+        [{ type: "TextQuoteSelector", exact: FIXTURE.known_good_quote }],
+      );
+    });
+    const textarea = screen.getByPlaceholderText(/Add a one-line comment/);
+    await user.type(textarea, "Form-cycling test evidence");
+    await user.click(screen.getByRole("button", { name: /Save evidence/ }));
+    await screen.findByText(/Form-cycling test evidence/);
+
+    // --- Switch to Forms mode.
+    await user.click(screen.getByRole("button", { name: "Forms" }));
+
+    // The evidence should appear in the Forms strip too (it queries by doc).
+    const stripCard = await screen.findByRole("button", {
+      name: /Form-cycling test evidence/,
+    });
+
+    // Stage it.
+    await user.click(stripCard);
+
+    // Click the Summary field → link gets created.
+    const summaryField = screen.getByLabelText("Summary of the matter");
+    await user.click(summaryField);
+
+    // Link chip on Summary now shows "1 evidence"
+    await waitFor(
+      () => {
+        expect(screen.queryByTestId("field-summary-chip")).not.toBeNull();
+      },
+      { timeout: 4000 },
+    );
+
+    // Resetting the previous scrollToAnnotationId so we can detect a *new*
+    // scroll triggered by chip auto-activation.
+    viewerSnapshot.scrollToAnnotationId = null;
+
+    // Click the Summary field again — this re-focuses the target. The chip
+    // computed for it should now contain our evidence; the chips' auto-
+    // activation effect fires setActiveEvidence; ScrollBridge translates
+    // it to a viewer scroll.
+    //
+    // Note: clicking the same field doesn't fire onFocus if it's already
+    // focused. Move focus elsewhere first, then back.
+    await user.click(screen.getByLabelText("Disputed amount"));
+    await user.click(summaryField);
+
+    // The chip rendered inside the form pane has aria-current="true".
+    await waitFor(() => {
+      const chip = document.querySelector(
+        '[data-evidence-id][aria-current="true"]',
+      );
+      expect(chip).not.toBeNull();
+    });
+
+    // The viewer was asked to scroll to the underlying annotation.
+    await waitFor(() => {
+      expect(viewerSnapshot.scrollToAnnotationId).toMatch(/^ann_/);
+    });
+  });
+});

tests/integration/forms-link-flow.dom.test.tsx

@@ -0,0 +1,184 @@
+/**
+ * CE-WP-0003-T05 integration — the side-by-side Forms layout +
+ * click-evidence-then-click-field linking interaction.
+ *
+ * Mirrors `app-prd-scenario.dom.test.tsx` (T09 of CE-WP-0002):
+ *   - mocks `@anchor/index` to swap PdfSpikeViewer for an inert div
+ *   - mocks `@source/index.ingestPdf` to skip PDF.js
+ *
+ * The flow:
+ *   1. Render <App />, switch to Forms mode via the top-bar button.
+ *   2. Open the fixture (CollectionList click).
+ *   3. Seed an EvidenceItem directly via the engine (creating one through
+ *      the UI requires Review mode and is exercised by T09).
+ *   4. Click the evidence card in the strip → staged for linking.
+ *   5. Click a form field → BindingService.linkEvidenceToTarget called.
+ *   6. The field's link-count chip shows "1 evidence".
+ */
+
+// @vitest-environment happy-dom
+
+import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import type { Document, DocumentRepresentation } from "@shared/document";
+import type { AnnotationId, DocumentId, RepresentationId } from "@shared/ids";
+import type { Selector } from "@shared/selector";
+
+import type { PdfSelectionCapture } from "@anchor/index";
+import manifest from "../../fixtures/pdfs/manifest.json" with { type: "json" };
+
+interface ViewerProps {
+  pdfUrl: string;
+  storedAnnotations: readonly { id: string; text: string; selectors: readonly Selector[] }[];
+  scrollToAnnotationId?: string;
+  onSelectionCaptured(capture: PdfSelectionCapture, selectors: Selector[]): void;
+}
+
+vi.mock("@anchor/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@anchor/index")>();
+  const MockPdfSpikeViewer = (props: ViewerProps) => {
+    return (
+      <div
+        data-testid="mock-pdf-viewer"
+        data-pdf-url={props.pdfUrl}
+        data-stored-count={String(props.storedAnnotations.length)}
+      />
+    );
+  };
+  return {
+    ...original,
+    PdfSpikeViewer: MockPdfSpikeViewer,
+  };
+});
+
+const FIXTURE = manifest.fixtures.find((f) => f.id === "fristsetzung-bezifferung")!;
+
+vi.mock("@source/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@source/index")>();
+  return {
+    ...original,
+    ingestPdf: vi.fn(async (_input: unknown, options?: { filename?: string }) => {
+      const documentId = ("doc_test_" + Math.random().toString(36).slice(2, 10)) as DocumentId;
+      const representationId = ("rep_test_" + Math.random().toString(36).slice(2, 10)) as RepresentationId;
+      const synthetic = "Synthetic canonical text for the form-link test.";
+      const document: Document = {
+        id: documentId,
+        mediaType: "application/pdf",
+        ...(options?.filename ? { title: options.filename } : {}),
+        fingerprint: "synthetic-fingerprint-for-test",
+        createdAt: "2026-05-25T00:00:00.000Z",
+        updatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      const representation: DocumentRepresentation = {
+        id: representationId,
+        documentId,
+        representationType: "pdf-text",
+        contentHash: "synthetic-fingerprint-for-test",
+        canonicalText: synthetic,
+        pageMap: [{ page: 1, width: 595, height: 842 }],
+        offsetMap: [
+          { page: 1, globalStart: 0, globalEnd: synthetic.length, pageLength: synthetic.length },
+        ],
+        generatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      return { document, representation };
+    }),
+  };
+});
+
+async function loadApp() {
+  const { App } = await import("@app/App");
+  return render(<App />);
+}
+
+describe("FormsApp — click-evidence-then-click-field linking (CE-WP-0003-T05)", () => {
+  beforeEach(() => {
+    globalThis.localStorage?.clear();
+    globalThis.fetch = vi.fn(async () =>
+      new Response(new Uint8Array([0x25, 0x50, 0x44, 0x46]).buffer, {
+        status: 200,
+        headers: { "Content-Type": "application/pdf" },
+      }),
+    );
+    // Forms mode is hash-driven; make sure we start clean.
+    if (typeof window !== "undefined") {
+      history.replaceState(null, "", window.location.pathname);
+    }
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    cleanup();
+  });
+
+  it("stages an evidence item then links it to the clicked field", async () => {
+    const user = userEvent.setup();
+    await loadApp();
+
+    // Switch to Forms via the top-bar button.
+    await user.click(screen.getByRole("button", { name: "Forms" }));
+
+    // The collection list is in the Forms layout too.
+    const fixtureBtn = screen.getByRole("button", { name: new RegExp(FIXTURE.id) });
+    await user.click(fixtureBtn);
+
+    // Wait for the fixture to load and the form to appear.
+    await waitFor(() => {
+      expect(screen.queryByLabelText("Summary of the matter")).not.toBeNull();
+    });
+
+    // Seed an EvidenceItem directly via the engine. We grab it through the
+    // EvidenceStrip empty-state lifecycle: capture an item via a mock
+    // dispatch. Since the engine is wrapped inside EngineProvider, we
+    // reach it by emitting a synthetic AnnotationCreated → EvidenceItem
+    // via window for testing isn't easy. Simpler: import the engine
+    // module directly and wire a parallel engine into the rendered app
+    // by patching localStorage. Even simpler for T05: drive the
+    // BindingService through its public API by talking to the engine
+    // through a getter we expose on window for tests.
+    //
+    // The smallest hack: drive engine.evidence.create + annotations.create
+    // by reaching through the engine instance the persister stores in
+    // localStorage. The persister key is "citation-evidence:engine-snapshot:v1".
+    // But the engine hasn't persisted yet — it has no events.
+    //
+    // The cleanest path: use a test-only window hook. We add it during
+    // the next iteration when wiring the active-cycling. For T05 the
+    // proof is the link-creation pipeline given a staged item — we
+    // dispatch the staged event manually with a synthetic id and verify
+    // that clicking a field triggers a link.
+    const SYNTHETIC_EV_ID = "ev_test_synthetic" as const;
+    await act(async () => {
+      window.dispatchEvent(
+        new CustomEvent("citation-evidence:staged-for-linking", {
+          detail: SYNTHETIC_EV_ID,
+        }),
+      );
+    });
+
+    // Click the Summary field → triggers FormFieldActivated → BindingService
+    // creates the link.
+    const summaryField = screen.getByLabelText("Summary of the matter");
+    await user.click(summaryField);
+
+    // The chip on the Summary field should now show 1 evidence.
+    await waitFor(() => {
+      expect(screen.queryByTestId("field-summary-chip")).not.toBeNull();
+    });
+    expect(screen.getByTestId("field-summary-chip").textContent).toMatch(/1 evidence/);
+  });
+
+  it("starts in Review mode by default and switches to Forms via hash", async () => {
+    await loadApp();
+    expect(screen.getByText("Collection")).toBeTruthy();
+    // Review pane's no-doc-open hint from EvidenceSidebar:
+    expect(screen.queryByText(/No document open/)).not.toBeNull();
+    // No demo form rendered yet
+    expect(screen.queryByText("Demo evidence-backed form")).toBeNull();
+  });
+});
+
+// Silence unused-import warnings for type-only imports referenced via JSX.
+void ((): AnnotationId | null => null);

tests/integration/forms-overlay-e2e.dom.test.tsx

@@ -0,0 +1,218 @@
+/**
+ * CE-WP-0003-T08 — end-to-end test of the form-binding slice (PRD
+ * scenario steps 5-9 from CE-WP-0002-T09's continuation):
+ *
+ *   5. Navigate to /forms/demo (hash route).
+ *   6. Link the previously-created evidence item to the "summary" field.
+ *   7. Click the "summary" field.
+ *   8. The field, the evidence card, and the highlight all have
+ *      aria-current="true".
+ *   9. The SVG visual-guide overlay contains exactly two <path> elements
+ *      (one field→card, one card→highlight).
+ *
+ * The viewer is mocked (same pattern as CE-WP-0002-T09) and
+ * `getHighlightClientRects` is stubbed to return a non-null DOMRect so
+ * the HighlightRectBridge can register a highlight rect — without that
+ * stub there is no real highlight DOM for the bridge to find.
+ *
+ * Step 10 (scroll → paths update next frame) is exercised by
+ * `Overlay.dom.test.tsx`'s invalidate-on-rect-change case; reproducing
+ * it through the full app stack would require driving the rAF scheduler
+ * deterministically, which is overkill given the dedicated unit test.
+ */
+
+// @vitest-environment happy-dom
+
+import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import type { Document, DocumentRepresentation } from "@shared/document";
+import type { DocumentId, RepresentationId } from "@shared/ids";
+import type { Selector } from "@shared/selector";
+
+import type { PdfSelectionCapture } from "@anchor/index";
+import manifest from "../../fixtures/pdfs/manifest.json" with { type: "json" };
+
+interface ViewerProps {
+  pdfUrl: string;
+  storedAnnotations: readonly { id: string; text: string; selectors: readonly Selector[] }[];
+  scrollToAnnotationId?: string;
+  onSelectionCaptured(capture: PdfSelectionCapture, selectors: Selector[]): void;
+}
+
+interface ViewerSnapshot {
+  pdfUrl: string | null;
+  scrollToAnnotationId: string | null;
+  onSelectionCaptured: ViewerProps["onSelectionCaptured"] | null;
+}
+
+const viewerSnapshot: ViewerSnapshot = {
+  pdfUrl: null,
+  scrollToAnnotationId: null,
+  onSelectionCaptured: null,
+};
+
+function fakeHighlightRect(): DOMRect {
+  // happy-dom may not expose a stable DOMRect constructor; use a literal.
+  return {
+    x: 700, y: 400, width: 200, height: 20,
+    top: 400, left: 700, right: 900, bottom: 420,
+    toJSON() { return {}; },
+  } as DOMRect;
+}
+
+vi.mock("@anchor/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@anchor/index")>();
+  const MockPdfSpikeViewer = (props: ViewerProps) => {
+    viewerSnapshot.pdfUrl = props.pdfUrl;
+    viewerSnapshot.scrollToAnnotationId = props.scrollToAnnotationId ?? null;
+    viewerSnapshot.onSelectionCaptured = props.onSelectionCaptured;
+    return <div data-testid="mock-pdf-viewer" />;
+  };
+  return {
+    ...original,
+    PdfSpikeViewer: MockPdfSpikeViewer,
+    // Always return a non-null rect so the HighlightRectBridge has
+    // something to register and the Overlay can draw the second leg.
+    getHighlightClientRects: vi.fn(() => fakeHighlightRect()),
+  };
+});
+
+const FIXTURE = manifest.fixtures.find((f) => f.id === "fristsetzung-bezifferung")!;
+const SYNTHETIC_CANONICAL = ["Pre.", FIXTURE.known_good_quote, "Post."].join(" ");
+
+vi.mock("@source/index", async (importOriginal) => {
+  const original = await importOriginal<typeof import("@source/index")>();
+  return {
+    ...original,
+    ingestPdf: vi.fn(async (_input: unknown, options?: { filename?: string }) => {
+      const documentId = ("doc_test_" + Math.random().toString(36).slice(2, 10)) as DocumentId;
+      const representationId = ("rep_test_" + Math.random().toString(36).slice(2, 10)) as RepresentationId;
+      const document: Document = {
+        id: documentId,
+        mediaType: "application/pdf",
+        ...(options?.filename ? { title: options.filename } : {}),
+        fingerprint: "synthetic-fingerprint-for-test",
+        createdAt: "2026-05-25T00:00:00.000Z",
+        updatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      const representation: DocumentRepresentation = {
+        id: representationId,
+        documentId,
+        representationType: "pdf-text",
+        contentHash: "synthetic-fingerprint-for-test",
+        canonicalText: SYNTHETIC_CANONICAL,
+        pageMap: [{ page: 1, width: 595, height: 842 }],
+        offsetMap: [
+          { page: 1, globalStart: 0, globalEnd: SYNTHETIC_CANONICAL.length, pageLength: SYNTHETIC_CANONICAL.length },
+        ],
+        generatedAt: "2026-05-25T00:00:00.000Z",
+      };
+      return { document, representation };
+    }),
+  };
+});
+
+function syntheticCaptureFor(text: string, page: number): PdfSelectionCapture {
+  return {
+    kind: "pdf",
+    text,
+    page,
+    rects: [{ x: 0.1, y: 0.2, width: 0.4, height: 0.04 }],
+    boundingRect: { x: 0.1, y: 0.2, width: 0.4, height: 0.04 },
+  };
+}
+
+async function loadApp() {
+  const { App } = await import("@app/App");
+  return render(<App />);
+}
+
+describe("CE-WP-0003-T08 — PRD scenario steps 5-9 end-to-end", () => {
+  beforeEach(() => {
+    viewerSnapshot.pdfUrl = null;
+    viewerSnapshot.scrollToAnnotationId = null;
+    viewerSnapshot.onSelectionCaptured = null;
+    globalThis.localStorage?.clear();
+    globalThis.fetch = vi.fn(async () =>
+      new Response(new Uint8Array([0x25, 0x50, 0x44, 0x46]).buffer, {
+        status: 200,
+        headers: { "Content-Type": "application/pdf" },
+      }),
+    );
+    if (typeof window !== "undefined") {
+      history.replaceState(null, "", window.location.pathname);
+    }
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    cleanup();
+  });
+
+  it(
+    "navigates to /forms/demo, links evidence, focuses field, asserts active triple + 2 SVG paths",
+    { timeout: 15000 },
+    async () => {
+      const user = userEvent.setup();
+      await loadApp();
+
+      // Steps 1-4 (CE-WP-0002 setup): create an evidence item in Review mode.
+      const fixtureBtn = screen.getByRole("button", { name: new RegExp(FIXTURE.id) });
+      await user.click(fixtureBtn);
+      await waitFor(() => expect(viewerSnapshot.onSelectionCaptured).not.toBeNull());
+      await act(async () => {
+        viewerSnapshot.onSelectionCaptured!(
+          syntheticCaptureFor(FIXTURE.known_good_quote, FIXTURE.known_good_quote_page),
+          [{ type: "TextQuoteSelector", exact: FIXTURE.known_good_quote }],
+        );
+      });
+      await user.type(
+        screen.getByPlaceholderText(/Add a one-line comment/),
+        "Overlay E2E evidence",
+      );
+      await user.click(screen.getByRole("button", { name: /Save evidence/ }));
+      await screen.findByText(/Overlay E2E evidence/);
+
+      // Step 5: navigate to /forms/demo via the top-bar.
+      await user.click(screen.getByRole("button", { name: "Forms" }));
+      expect(window.location.hash).toBe("#/forms/demo");
+
+      // Step 6: stage the evidence in the strip, then click the summary
+      // field to create the link.
+      const stripCard = await screen.findByRole("button", {
+        name: /Overlay E2E evidence/,
+      });
+      await user.click(stripCard);
+      const summaryField = screen.getByLabelText("Summary of the matter");
+      await user.click(summaryField);
+
+      // Move focus elsewhere and back to re-fire focus on summary so that
+      // ActiveStateProvider triggers focus-target (the previous click that
+      // created the link consumed the staged state).
+      await user.click(screen.getByLabelText("Disputed amount"));
+      await user.click(summaryField);
+
+      // Step 8: aria-current on field row, chip, and (via the active
+      // state) the strip card.
+      await waitFor(() => {
+        const fieldRow = document.querySelector(
+          '[data-field-id="summary"][aria-current="true"]',
+        );
+        expect(fieldRow).not.toBeNull();
+      });
+      const activeChip = document.querySelector('[data-evidence-id][aria-current="true"]');
+      expect(activeChip).not.toBeNull();
+
+      // Step 9: SVG overlay renders 2 paths (field→card + card→highlight).
+      // HighlightRectBridge registers via the mocked getHighlightClientRects.
+      await waitFor(() => {
+        const svg = document.querySelector('[data-testid="visual-guide-overlay"]');
+        expect(svg).not.toBeNull();
+        expect(svg!.getAttribute("data-path-count")).toBe("2");
+        expect(svg!.querySelectorAll("path").length).toBe(2);
+      });
+    },
+  );
+});

workplans/CE-WP-0003-form-binding-visual-guide.md

@@ -8,10 +8,10 @@ repo_id: a677c189-b4e2-4f2a-9e48-faa482c277e6
 topic_slug: citation_evidence_mvp
 topic_id: 96fa8e80-9f74-40f2-84cd-644e9747b9ec
 state_hub_workstream_id: 7b5b7235-57e3-4835-8fa6-376bb518fe2d
-status: todo
+status: done
 owner: Bernd
 created: 2026-05-24
-updated: 2026-05-24
+updated: 2026-05-25
 depends_on_workplan: CE-WP-0002
 spec_refs:
   - wiki/ProductRequirementsDocument.md
@@ -58,7 +58,7 @@ T01 (EvidenceLink + EvidenceSet types + relation/status enums)
 id: CE-WP-0003-T01
 state_hub_task_id: 120b9b5a-9ca3-4dff-8c26-1b5c2e832dc4
 priority: critical
-status: todo
+status: done
 ```
 
 Add under `src/shared/`:
@@ -82,7 +82,7 @@ updating the doc, the test fails.
 id: CE-WP-0003-T02
 state_hub_task_id: f17e251d-4fd7-4ef3-b35c-e8e0dfb3a455
 priority: high
-status: todo
+status: done
 depends_on: [T01]
 ```
 
@@ -106,7 +106,7 @@ Emit the events from SharedContracts §4 (`EvidenceLinkCreated`,
 id: CE-WP-0003-T03
 state_hub_task_id: d3b853ef-7afe-491f-b40b-b6e980a23478
 priority: critical
-status: todo
+status: done
 depends_on: [T02]
 ```
 
@@ -134,7 +134,7 @@ it in T05/T06/T07.
 id: CE-WP-0003-T04
 state_hub_task_id: f42e1ecc-351c-4248-8872-1a25e79d3640
 priority: medium
-status: todo
+status: done
 depends_on: [T01]
 ```
 
@@ -150,7 +150,12 @@ type FormFieldSchema =
 JSON Schema is **not** used yet — defer that to a later ADR. The MVP form
 just needs to render 3-4 fields and accept evidence links.
 
-- `src/work/FormRenderer.tsx` renders the schema as a basic form
+- `src/binder/FormRenderer.tsx` renders the schema as a basic form
+  (relocated from `src/work/` per `wiki/DependencyMap.md` §2/§5 — `work`
+  cannot import `binder`, but FormRenderer needs `useRegisterRect` from
+  `binder/visual-guide`. The "evidence-backed form" composition belongs
+  in `binder/`; `app/` mounts both `work` panes and `binder` panes
+  side-by-side.)
 - Each field registers itself with the rect registry as kind `"field"` with
   the field's `id`
 
@@ -162,7 +167,7 @@ just needs to render 3-4 fields and accept evidence links.
 id: CE-WP-0003-T05
 state_hub_task_id: 100fb1ca-6168-4e5d-9dc5-f051e6f9ff61
 priority: high
-status: todo
+status: done
 depends_on: [T02, T04]
 ```
 
@@ -185,7 +190,7 @@ linked fields (e.g. a chip showing the count of linked evidence items).
 id: CE-WP-0003-T06
 state_hub_task_id: e3bdf1d3-c7a1-484c-8895-8d103e7f9fe6
 priority: high
-status: todo
+status: done
 depends_on: [T05]
 ```
 
@@ -209,7 +214,7 @@ Each evidence card registers itself with the rect registry as
 id: CE-WP-0003-T07
 state_hub_task_id: e2ec50be-d9c5-47dd-b801-9c1afb01e6fd
 priority: high
-status: todo
+status: done
 depends_on: [T03, T06]
 ```
 
@@ -237,7 +242,7 @@ registered.
 id: CE-WP-0003-T08
 state_hub_task_id: e6754c8e-f9e2-435a-af28-31a693c6d9a8
 priority: high
-status: todo
+status: done
 depends_on: [T05, T07]
 ```