From f45fbab945ca8bf6226400af829ab473ebf44a25 Mon Sep 17 00:00:00 2001
From: Wild Karl-Heinz <kh.wild@wicom.li>
Date: Tue, 8 Sep 2026 23:19:42 +0200
Subject: [PATCH] =?UTF-8?q?Interaktives=20Abh=C3=A4ngigkeiten-Panel=20(Vor?=
 =?UTF-8?q?g=C3=A4nger/Nachfolger,=20andockbar)?=
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Content-Type: text/plain; charset=UTF-8
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Rechtsklick auf eine Zelle → "🕸 Abhängigkeiten anzeigen" öffnet ein an der
rechten Seite angedocktes Panel (wie das Einstellungen-Panel links) mit den
direkten Vorgängern (was die Zelle liest) und Nachfolgern (was sie liest),
auch über Tabellen-/Blattgrenzen hinweg. Ein Klick auf einen Eintrag
navigiert wirklich dorthin: wählt die echte Zelle im Dokument aus, wechselt
bei Bedarf das Blatt-Tab, und das Panel zentriert sich neu — Blatt-Tabs,
Canvas, Formel- und Statusleiste bleiben dabei die ganze Zeit sichtbar und
bedienbar (kein Vollbild-Dialog). Jeder Eintrag zeigt immer den Blattnamen,
nie nur implizit. Zirkelbezüge werden rot markiert.

Neu in der Engine: Workbook.graphPrecedents/graphDependents, dünne
öffentliche Wrapper um den bereits vorhandenen DependencyGraph. Im Store:
cellGraphSelf/cellGraphNeighbors (Anreicherung für die Anzeige) sowie
openDependencyGraph/closeDependencyGraph (dokumentweiter UI-State, ruft
intern das bestehende selectCell auf).

424 Tests (Engine-/Store-Ebene vollständig abgedeckt), vue-tsc/eslint/build
sauber. Das Panel selbst nur live per Playwright verifiziert (kein
Komponenten-Test-Setup vorhanden, in README dokumentiert).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 README.md                              |  52 +++++
 src/App.vue                            |   2 +
 src/components/DependencyGraphView.vue | 305 +++++++++++++++++++++++++
 src/components/SheetCanvas.vue         |  10 +-
 src/components/TableGrid.vue           |  13 ++
 src/engine/README.md                   |  10 +
 src/engine/__tests__/workbook.spec.ts  |  65 ++++++
 src/engine/index.ts                    |   1 +
 src/engine/workbook.ts                 |  16 ++
 src/store/__tests__/document.spec.ts   | 139 +++++++++++
 src/store/document.ts                  |  79 ++++++-
 src/store/types.ts                     |  23 ++
 12 files changed, 712 insertions(+), 3 deletions(-)
 create mode 100644 src/components/DependencyGraphView.vue

diff --git a/README.md b/README.md
index fba9513..2687f76 100644
--- a/README.md
+++ b/README.md
@@ -411,6 +411,40 @@ mitgezogen:
   Tabelle liegt.
 - **Undo/Redo-fähig** wie jede andere Änderung.
 
+### Abhängigkeiten erkunden (🕸)
+
+Rechtsklick auf eine Zelle → **„🕸 Abhängigkeiten anzeigen"** öffnet ein
+andockbares Panel rechts (wie das Einstellungen-Panel links) — **kein**
+Vollbild-Dialog, damit Blatt-Tabs, Statusleiste und Canvas die ganze Zeit
+sichtbar und bedienbar bleiben: der Blattbezug geht beim Erkunden nie
+verloren. Zeigt für die Zelle:
+
+- **Vorgänger** — jede Zelle, die ihre Formel direkt liest (bei einem
+  Bereich wie `SUM(B2:E2)` jede einzelne Zelle darin).
+- **Nachfolger** — jede Zelle, die *diese* Zelle direkt liest, auch über
+  Tabellen-/Blattgrenzen hinweg.
+- Jeder Eintrag zeigt **Blatt · Tabelle!Zelle** (Blattname **immer**, nicht
+  nur bei Mehrdeutigkeit) sowie den aktuellen Wert.
+
+**Ein Klick auf einen Eintrag navigiert wirklich dorthin** — nicht nur
+innerhalb des Panels: Er wählt die echte Zelle im Dokument aus, wechselt bei
+Bedarf das Blatt-Tab, und das Panel zentriert sich neu auf sie. Formelleiste,
+Statusleiste und die Tabellen selbst zeigen danach exakt dieselbe Zelle, die
+im Panel zentriert ist — das Erkunden des Formel-Netzwerks *ist* Navigieren,
+keine isolierte Nebenansicht. **„← Zurück"** geht die so besuchten Zellen
+rückwärts durch (auch das mit echter Navigation, nicht nur Panel-intern).
+
+Ein Zirkelbezug (`#CIRC`) wird rot markiert (⚠), sowohl als Zentrum als auch
+als Vorgänger/Nachfolger-Eintrag — die Kante existiert im Abhängigkeitsgraphen
+unabhängig davon, dass sie bei der Neuberechnung übersprungen wird (s.
+„Fehlermodell" unten).
+
+**Bewusst ohne**: kein automatisches Scrollen der Zieltabelle zur
+navigierten Zelle, falls sie außerhalb des sichtbaren Ausschnitts liegt
+(bei einer „Feste Größe"-Tabelle mit vielen Zeilen); keine Gruppierung
+vieler Vorgänger/Nachfolger zu einem Bereichs-Eintrag (`Umsatz!B2:B100`
+erscheint als 99 einzelne Zeilen, nicht als ein zusammengefasster Eintrag).
+
 ### Zell-Formatierung
 
 Auswahl (Zelle, Bereich, Mehrfachauswahl, ganze Zeile/Spalte über den Kopf) → im
@@ -972,6 +1006,16 @@ Grundrechenarten: `Übersicht!B2 = =SUM(Umsatz!B2:E2)`, `D2 = =B2-C2`,
   Bereich, `$`-Sperren bleiben wirkungslos (anders als beim Kopieren),
   unveränderte Referenzen bleiben byte-identisch, Undo/Redo, Schutz gegen
   Löschen der letzten verbleibenden Zeile/Spalte.
+- **Abhängigkeiten erkunden** (`graphPrecedents`/`graphDependents` in
+  `workbook.spec.ts`, `cellGraphSelf`/`cellGraphNeighbors`/
+  `openDependencyGraph`/`closeDependencyGraph` in `document.spec.ts`) —
+  exakte Vorgänger/Nachfolger-Kanten, Auflösung über Tabellen-/Blattgrenzen,
+  bleibt korrekt für eine Zelle auf einem Zirkelbezug, aktualisiert sich
+  nach einer Neuzuordnung der Formel, `openDependencyGraph` löst wirklich
+  `selectCell` aus (inkl. Blatt-Tab-Wechsel), `closeDependencyGraph` rührt
+  die Auswahl nicht an. Das Panel selbst (`DependencyGraphView.vue`) ist
+  nur live per Playwright verifiziert, kein Komponenten-Test-Setup
+  vorhanden (s. „Bekannte Grenzen").
 - **„Mit Schleife"-Code** — Parser-Ebene (`parseFunctionBlock`): ein
   `FOR...DO...END` mit mehreren Anweisungen, mehrere unabhängige Schleifen
   nacheinander, `IF...THEN...END` und `IF...THEN...ELSE...END`, `IF`
@@ -1043,6 +1087,14 @@ Grundrechenarten: `Übersicht!B2 = =SUM(Umsatz!B2:E2)`, `D2 = =B2-C2`,
   Komponenten-Test-Setup (z. B. Vue Test Utils), nur Engine-/Store-Tests.
   Nur live per Playwright verifiziert (Wachsen, Schrumpfen mit
   Inhaltsschutz, deutliches Überschreiten der bestehenden Größe).
+- **Abhängigkeiten-Panel** (`DependencyGraphView.vue`) bewusst ohne: Gruppierung
+  vieler Vorgänger/Nachfolger zu einem Bereichs-Eintrag (jede Zelle einzeln,
+  ungeachtet der Anzahl), automatisches Scrollen der Zieltabelle zur
+  navigierten Zelle. Wie bei der Tabellen-Größenänderung oben: rein
+  UI-seitig, nur live per Playwright verifiziert, kein Komponenten-Test-Setup
+  vorhanden — die zugrundeliegenden Store-/Engine-Funktionen
+  (`graphPrecedents`/`graphDependents`/`cellGraphNeighbors`/
+  `openDependencyGraph`) sind es aber (s. „Tests" oben).
 - **Objekt-Bezüge beim Anhängen.** Beim JSON-*Anhängen* zweier Dokumente werden
   nur Blatt-/Objekt-IDs neu vergeben, nicht Tabellennamen. Kollidiert ein
   angehängter Tabellenname mit einem bestehenden, gewinnt bei der Auflösung der
diff --git a/src/App.vue b/src/App.vue
index af62a9c..9e2949e 100644
--- a/src/App.vue
+++ b/src/App.vue
@@ -6,6 +6,7 @@ import SheetCanvas from './components/SheetCanvas.vue';
 import SheetTabs from './components/SheetTabs.vue';
 import StatusBar from './components/StatusBar.vue';
 import SettingsPanel from './components/SettingsPanel.vue';
+import DependencyGraphView from './components/DependencyGraphView.vue';
 import { useToasts } from './composables/useToasts';
 import { useDocument } from './store/document';
 
@@ -48,6 +49,7 @@ onBeforeUnmount(() => window.removeEventListener('keydown', onGlobalKeydown));
     <main class="workspace">
       <SheetCanvas @files="onCanvasFiles" />
       <SettingsPanel />
+      <DependencyGraphView />
     </main>
 
     <div class="bottom-bar">
diff --git a/src/components/DependencyGraphView.vue b/src/components/DependencyGraphView.vue
new file mode 100644
index 0000000..7960b7d
--- /dev/null
+++ b/src/components/DependencyGraphView.vue
@@ -0,0 +1,305 @@
+<script setup lang="ts">
+/**
+ * Interactive dependency-graph explorer, docked to the right (like
+ * SettingsPanel.vue docks left) -- NOT a full-screen modal: the canvas and
+ * sheet tabs stay visible and interactive the whole time, so navigating the
+ * graph never loses track of which sheet/table you're actually looking at.
+ *
+ * A single document-wide instance (controlled via `store.ui.depGraph`, the
+ * same pattern as `settingsOpen`), not owned by any one `TableGrid` -- opened
+ * from a cell's context menu ("🕸 Abhängigkeiten anzeigen"). Clicking any
+ * precedent/dependent node *really* navigates there (store.openDependencyGraph
+ * also calls selectCell, which switches the active sheet/object as a side
+ * effect) -- the drawer re-centers on it exactly like a fresh open would.
+ */
+import { computed, ref, watch } from 'vue';
+import { useDocument } from '../store/document';
+import type { CellGraphNode } from '../store/types';
+
+const store = useDocument();
+
+interface Loc {
+  tableId: string;
+  col: number;
+  row: number;
+}
+
+const loc = computed(() => store.ui.depGraph);
+const open = computed(() => loc.value !== null);
+
+const history = ref<Loc[]>([]);
+// a closed -> open transition always starts a fresh navigation history
+watch(open, (isOpen, wasOpen) => {
+  if (isOpen && !wasOpen) history.value = [];
+});
+
+function goTo(node: CellGraphNode) {
+  if (loc.value) history.value.push(loc.value);
+  store.openDependencyGraph(node.tableId, node.col, node.row);
+}
+function goBack() {
+  const prev = history.value.pop();
+  if (prev) store.openDependencyGraph(prev.tableId, prev.col, prev.row);
+}
+function close() {
+  store.closeDependencyGraph();
+}
+function onKey(e: KeyboardEvent) {
+  if (e.key === 'Escape') close();
+}
+watch(open, (isOpen) => {
+  if (isOpen) document.addEventListener('keydown', onKey);
+  else document.removeEventListener('keydown', onKey);
+});
+
+const self = computed(() => (loc.value ? store.cellGraphSelf(loc.value.tableId, loc.value.col, loc.value.row) : null));
+const neighbors = computed(() =>
+  loc.value
+    ? store.cellGraphNeighbors(loc.value.tableId, loc.value.col, loc.value.row)
+    : { precedents: [], dependents: [] },
+);
+
+/** Always "Blatt · Tabelle!Zelle" -- the sheet name is never omitted here
+ *  (unlike an in-formula reference, which only qualifies when needed): the
+ *  whole point of this panel is never losing track of *where* something is. */
+function label(node: CellGraphNode): string {
+  return `${node.sheetName ? node.sheetName + ' · ' : ''}${node.tableName}!${node.label}`;
+}
+function display(node: CellGraphNode): string {
+  return store.cellDisplay(node.tableId, node.col, node.row);
+}
+</script>
+
+<template>
+  <aside class="dg-drawer" :class="{ open }" aria-label="Abhängigkeiten">
+    <header>
+      <button class="back" :disabled="!history.length" title="Zurück" @click="goBack">←</button>
+      <h2>🕸 Abhängigkeiten</h2>
+      <button class="x" title="Schließen" @click="close">×</button>
+    </header>
+
+    <div v-if="self" class="body">
+      <section class="self-card" :class="{ circular: self.isCircular }">
+        <p v-if="self.isCircular" class="circ-warn">⚠ Teil eines Zirkelbezugs</p>
+        <p class="cell-label">{{ label(self) }}</p>
+        <p class="cell-value">{{ display(self) }}</p>
+        <p v-if="self.raw" class="cell-raw">{{ self.raw }}</p>
+      </section>
+
+      <section>
+        <h3>Vorgänger — liest von ({{ neighbors.precedents.length }})</h3>
+        <p v-if="!neighbors.precedents.length" class="empty">keine</p>
+        <ul v-else class="node-list">
+          <li v-for="(n, i) in neighbors.precedents" :key="'p' + i">
+            <button
+              type="button"
+              class="node-btn"
+              :class="{ circular: n.isCircular }"
+              :title="n.raw || display(n)"
+              @click="goTo(n)"
+            >
+              <span v-if="n.isCircular" class="warn">⚠</span>
+              <span class="node-label">{{ label(n) }}</span>
+              <span class="node-value">{{ display(n) }}</span>
+            </button>
+          </li>
+        </ul>
+      </section>
+
+      <section>
+        <h3>Nachfolger — liest davon ({{ neighbors.dependents.length }})</h3>
+        <p v-if="!neighbors.dependents.length" class="empty">keine</p>
+        <ul v-else class="node-list">
+          <li v-for="(n, i) in neighbors.dependents" :key="'d' + i">
+            <button
+              type="button"
+              class="node-btn"
+              :class="{ circular: n.isCircular }"
+              :title="n.raw || display(n)"
+              @click="goTo(n)"
+            >
+              <span v-if="n.isCircular" class="warn">⚠</span>
+              <span class="node-label">{{ label(n) }}</span>
+              <span class="node-value">{{ display(n) }}</span>
+            </button>
+          </li>
+        </ul>
+      </section>
+    </div>
+    <p v-else class="body-empty">Zelle nicht gefunden.</p>
+  </aside>
+</template>
+
+<style scoped>
+.dg-drawer {
+  position: absolute;
+  z-index: 60;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  width: 380px;
+  max-width: 88vw;
+  display: flex;
+  flex-direction: column;
+  background: var(--surface);
+  border-left: 1px solid var(--border);
+  box-shadow: var(--shadow);
+  transform: translateX(102%);
+  transition: transform 0.18s ease;
+}
+.dg-drawer.open {
+  transform: none;
+}
+header {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 12px 14px;
+  border-bottom: 1px solid var(--border);
+  flex: none;
+}
+h2 {
+  flex: 1;
+  margin: 0;
+  font-size: 14px;
+}
+.back,
+.x {
+  border: 0;
+  background: transparent;
+  cursor: pointer;
+  color: var(--text-dim);
+  flex: none;
+}
+.back {
+  font-size: 15px;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  padding: 3px 9px;
+}
+.back:disabled {
+  opacity: 0.35;
+  cursor: default;
+}
+.back:not(:disabled):hover,
+.x:hover {
+  color: var(--accent);
+  border-color: var(--accent);
+}
+.x {
+  font-size: 18px;
+}
+.body {
+  overflow-y: auto;
+  padding: 4px 14px 20px;
+}
+.body-empty {
+  padding: 14px;
+  color: var(--text-dim);
+  font-size: 12.5px;
+}
+section {
+  padding: 14px 0;
+  border-bottom: 1px solid var(--border);
+}
+section:last-child {
+  border-bottom: 0;
+}
+h3 {
+  margin: 0 0 8px;
+  font-size: 11px;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.02em;
+  color: var(--text-dim);
+}
+.self-card {
+  border-radius: var(--radius-sm);
+  background: var(--accent);
+  color: #fff;
+  padding: 10px 12px;
+}
+.self-card.circular {
+  background: #dc2626;
+}
+.cell-label {
+  margin: 0;
+  font-family: ui-monospace, monospace;
+  font-size: 13px;
+  font-weight: 600;
+  overflow-wrap: anywhere;
+}
+.cell-value {
+  margin: 2px 0 0;
+  font-size: 12.5px;
+  opacity: 0.9;
+}
+.cell-raw {
+  margin: 4px 0 0;
+  font-size: 11px;
+  font-family: ui-monospace, monospace;
+  opacity: 0.8;
+  overflow-wrap: anywhere;
+}
+.circ-warn {
+  margin: 0 0 4px;
+  font-size: 11px;
+  font-weight: 600;
+}
+.empty {
+  margin: 0;
+  font-size: 12px;
+  font-style: italic;
+  color: var(--text-dim);
+}
+.node-list {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+.node-btn {
+  width: 100%;
+  text-align: left;
+  display: flex;
+  align-items: baseline;
+  gap: 6px;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background: var(--surface-2);
+  padding: 6px 9px;
+  font: inherit;
+  cursor: pointer;
+}
+.node-btn:hover {
+  border-color: var(--accent);
+}
+.node-btn.circular {
+  border-color: #dc2626;
+}
+.node-label {
+  font-family: ui-monospace, monospace;
+  font-size: 12px;
+  font-weight: 600;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+.node-value {
+  margin-left: auto;
+  flex: none;
+  font-size: 11.5px;
+  color: var(--text-dim);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  max-width: 40%;
+}
+.warn {
+  font-size: 10.5px;
+  color: #dc2626;
+  flex: none;
+}
+</style>
diff --git a/src/components/SheetCanvas.vue b/src/components/SheetCanvas.vue
index 92292df..5dec28f 100644
--- a/src/components/SheetCanvas.vue
+++ b/src/components/SheetCanvas.vue
@@ -74,7 +74,7 @@ function selectObj(id: string) {
 <template>
   <div
     class="canvas-wrap"
-    :class="{ 'drawer-open': store.ui.settingsOpen }"
+    :class="{ 'drawer-open': store.ui.settingsOpen, 'dep-open': store.ui.depGraph }"
     :style="appearance"
   >
     <div
@@ -118,15 +118,21 @@ function selectObj(id: string) {
   position: relative;
   height: 100%;
   overflow: hidden;
-  transition: margin-left 0.18s ease;
+  transition: margin-left 0.18s ease, margin-right 0.18s ease;
 }
 .canvas-wrap.drawer-open {
   margin-left: 320px;
 }
+.canvas-wrap.dep-open {
+  margin-right: 380px;
+}
 @media (max-width: 640px) {
   .canvas-wrap.drawer-open {
     margin-left: 0; /* drawer overlays on narrow screens */
   }
+  .canvas-wrap.dep-open {
+    margin-right: 0;
+  }
 }
 .canvas-scroll {
   position: absolute;
diff --git a/src/components/TableGrid.vue b/src/components/TableGrid.vue
index 357349f..53c7eb3 100644
--- a/src/components/TableGrid.vue
+++ b/src/components/TableGrid.vue
@@ -969,6 +969,18 @@ function onContextMenu(e: MouseEvent) {
   if (hit && !inSelection(hit.c, hit.r)) select(hit.c, hit.r);
   menu.value = { x: e.clientX, y: e.clientY, open: true };
 }
+
+// ---- dependency-graph view ---------------------------------
+/** Opens the (single, document-wide) dependency-graph drawer on the cell
+ *  the context menu was invoked on -- `select()` in onContextMenu above
+ *  already made it the active cell by the time this runs, so the active
+ *  selection's focus is exactly the right cell. */
+function openDependencyGraph() {
+  const s = store.doc.selection;
+  if (!s || s.tableId !== props.tableId) return;
+  store.openDependencyGraph(props.tableId, s.focus.col, s.focus.row);
+}
+
 const menuItems = computed(() => {
   const t = table.value;
   const ctx = menuCtx.value;
@@ -996,6 +1008,7 @@ const menuItems = computed(() => {
   ];
   if (store.hasClipboard.value) items.push({ label: 'Einfügen', action: () => store.pasteClipboard() });
   items.push(
+    { label: '🕸 Abhängigkeiten anzeigen', action: openDependencyGraph },
     { label: 'Zeile hinzufügen', action: () => store.addRows(props.tableId) },
     { label: 'Spalte hinzufügen', action: () => store.addColumns(props.tableId) },
     { label: 'Letzte Zeile entfernen', action: () => store.removeLastRow(props.tableId) },
diff --git a/src/engine/README.md b/src/engine/README.md
index f2252ef..c913a3a 100644
--- a/src/engine/README.md
+++ b/src/engine/README.md
@@ -558,6 +558,16 @@ gefunden wird — dieselbe konservative Konvention wie bei `IF`.
 Strukturänderungen (Tabelle umbenennen/löschen, Zeilen/Spalten, Blatt löschen)
 rufen `rebuild()` für einen vollständigen – trotzdem billigen – Durchlauf.
 
+**`Workbook.graphPrecedents`/`graphDependents`** (dünne öffentliche Wrapper
+um `DependencyGraph.getPrecedents`/`getDependents`) sind der einzige Ort, an
+dem der Graph *abgefragt* statt nur für die Neuberechnung *benutzt* wird –
+die Datenquelle des interaktiven Abhängigkeiten-Panels (`src/store/
+document.ts`s `cellGraphNeighbors`/`cellGraphSelf`, `src/components/
+DependencyGraphView.vue`, s. Haupt-README „Abhängigkeiten erkunden"). Rein
+lesend, ohne jeden Effekt auf Auswertung/Neuberechnung; bleiben auch für
+eine Zelle auf einem Zirkelbezug korrekt (die Kante existiert im Graphen
+unabhängig davon, dass `topoOrder` sie aus der Auswertung ausschließt).
+
 ## Fehlermodell
 
 | Wert       | Bedeutung |
diff --git a/src/engine/__tests__/workbook.spec.ts b/src/engine/__tests__/workbook.spec.ts
index 96c0c05..9ad1740 100644
--- a/src/engine/__tests__/workbook.spec.ts
+++ b/src/engine/__tests__/workbook.spec.ts
@@ -193,6 +193,71 @@ describe('Workbook named ranges', () => {
   });
 });
 
+describe('Workbook graph queries (graphPrecedents/graphDependents)', () => {
+  const coords = (a1: string) => {
+    const m = /^([A-Z]+)([0-9]+)$/.exec(a1)!;
+    return { col: m[1].split('').reduce((n, ch) => n * 26 + (ch.charCodeAt(0) - 64), 0) - 1, row: Number(m[2]) - 1 };
+  };
+
+  it('graphPrecedents lists exactly the cells a formula reads, same-table', () => {
+    const wb = fixture();
+    const { col, row } = coords('D2'); // Übersicht!D2 = B2-C2
+    const precs = wb.graphPrecedents('s-ueber', col, row);
+    expect(precs).toHaveLength(2);
+    expect(precs).toContainEqual({ tableId: 's-ueber', ...coords('B2') });
+    expect(precs).toContainEqual({ tableId: 's-ueber', ...coords('C2') });
+  });
+
+  it('graphPrecedents follows a cross-table range reference to every cell in it', () => {
+    const wb = fixture();
+    const { col, row } = coords('B2'); // Übersicht!B2 = SUM(Umsatz!B2:E2)
+    const precs = wb.graphPrecedents('s-ueber', col, row);
+    expect(precs).toHaveLength(4);
+    for (const a1 of ['B2', 'C2', 'D2', 'E2']) {
+      expect(precs).toContainEqual({ tableId: 's-umsatz', ...coords(a1) });
+    }
+  });
+
+  it('graphDependents is the exact reverse of graphPrecedents', () => {
+    const wb = fixture();
+    const { col, row } = coords('B2'); // Übersicht!B2 -- read by D2 and (via D2) E2 directly reads B2 too
+    const deps = wb.graphDependents('s-ueber', col, row);
+    expect(deps).toContainEqual({ tableId: 's-ueber', ...coords('D2') });
+    expect(deps).toContainEqual({ tableId: 's-ueber', ...coords('E2') }); // E2 = D2/B2*100, reads B2 directly
+  });
+
+  it('a cell with no formula (or a literal) has no precedents', () => {
+    const wb = fixture();
+    const { col, row } = coords('B2'); // Umsatz!B2 is a plain literal, "1200"
+    expect(wb.graphPrecedents('s-umsatz', col, row)).toEqual([]);
+  });
+
+  it('a cell nothing reads has no dependents', () => {
+    const wb = fixture();
+    const { col, row } = coords('A2'); // Umsatz!A2 = "Nord", never referenced by a formula
+    expect(wb.graphDependents('s-umsatz', col, row)).toEqual([]);
+  });
+
+  it('stays accurate for cells on a circular reference (edges exist even though topoOrder drops them)', () => {
+    const a = sheet('s1', 'S1', { A1: '=B1', B1: '=A1' });
+    const wb = new Workbook([a]);
+    const a1 = coords('A1');
+    expect(wb.graphPrecedents('s1', a1.col, a1.row)).toContainEqual({ tableId: 's1', ...coords('B1') });
+    expect(wb.graphDependents('s1', a1.col, a1.row)).toContainEqual({ tableId: 's1', ...coords('B1') });
+  });
+
+  it('updates live after a cell is re-edited to reference something else', () => {
+    const wb = fixture();
+    const c1 = coords('C1');
+    wb.setCell('s-umsatz', c1.col, c1.row, '=B2');
+    expect(wb.graphPrecedents('s-umsatz', c1.col, c1.row)).toContainEqual({ tableId: 's-umsatz', ...coords('B2') });
+    wb.setCell('s-umsatz', c1.col, c1.row, '=B3');
+    const precs = wb.graphPrecedents('s-umsatz', c1.col, c1.row);
+    expect(precs).toContainEqual({ tableId: 's-umsatz', ...coords('B3') });
+    expect(precs).not.toContainEqual({ tableId: 's-umsatz', ...coords('B2') });
+  });
+});
+
 describe('Workbook recalculation order', () => {
   it('evaluates precedents before dependents (chain across sheets)', () => {
     const wb = fixture();
diff --git a/src/engine/index.ts b/src/engine/index.ts
index a7f5a8e..c056edd 100644
--- a/src/engine/index.ts
+++ b/src/engine/index.ts
@@ -62,6 +62,7 @@ export {
   ERROR_CODES,
   type ErrorCode,
   type CellValue,
+  type CellRef,
   type Scalar,
   type EngineHost,
   type NamedRangeDef,
diff --git a/src/engine/workbook.ts b/src/engine/workbook.ts
index aaee823..e8c75e2 100644
--- a/src/engine/workbook.ts
+++ b/src/engine/workbook.ts
@@ -29,6 +29,7 @@ import {
   isError,
   keyOf,
   parseKey,
+  type CellRef,
   type CellValue,
   type EngineHost,
   type NamedRangeDef,
@@ -158,6 +159,21 @@ export class Workbook implements EngineHost {
     return v === undefined ? null : v;
   }
 
+  /** Direct precedents of a cell -- the cells its own formula reads (a
+   *  formula's `#REF`/named-range/etc. resolution already baked into the
+   *  graph edges, see `precedentsOf()` above). Public wrapper around the
+   *  internal `DependencyGraph`, for UI features (the dependency-graph
+   *  view) that need to *query* the graph -- evaluation itself never calls
+   *  this, it only calls `setPrecedents`/`affected`/`topoOrder`. */
+  graphPrecedents(tableId: string, col: number, row: number): CellRef[] {
+    return [...this.graph.getPrecedents(keyOf(tableId, col, row))].map(parseKey);
+  }
+  /** Direct dependents of a cell -- every cell whose formula reads *this*
+   *  one. See graphPrecedents() above. */
+  graphDependents(tableId: string, col: number, row: number): CellRef[] {
+    return [...this.graph.getDependents(keyOf(tableId, col, row))].map(parseKey);
+  }
+
   // ---- writes ---------------------------------------------------------
 
   /** Set (or clear, with `''`) one cell and recalculate the affected cells. */
diff --git a/src/store/__tests__/document.spec.ts b/src/store/__tests__/document.spec.ts
index 46066bd..0fe38ca 100644
--- a/src/store/__tests__/document.spec.ts
+++ b/src/store/__tests__/document.spec.ts
@@ -1233,6 +1233,145 @@ describe('insertRow/deleteRow/insertColumn/deleteColumn (mid-grid, not just edge
   });
 });
 
+describe('dependency-graph view (cellGraphSelf/cellGraphNeighbors)', () => {
+  it('cellGraphSelf describes a formula cell: label, raw text, value, table/sheet name', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'B5', '10');
+    setCell(s, name, 'C1', '=B5+1');
+    const { col, row } = coords('C1');
+    const node = s.cellGraphSelf(id, col, row)!;
+    expect(node).toMatchObject({
+      tableId: id,
+      tableName: name,
+      col,
+      row,
+      label: 'C1',
+      raw: '=B5+1',
+      value: 11,
+      isCircular: false,
+    });
+  });
+
+  it('cellGraphNeighbors.precedents lists exactly the cells a formula reads', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'B2', '1');
+    setCell(s, name, 'B3', '2');
+    setCell(s, name, 'D1', '=SUM(B2:B3)');
+    const { col, row } = coords('D1');
+    const { precedents } = s.cellGraphNeighbors(id, col, row);
+    expect(precedents.map((n) => n.label).sort()).toEqual(['B2', 'B3']);
+    expect(precedents.every((n) => n.tableId === id)).toBe(true);
+  });
+
+  it('cellGraphNeighbors.dependents is the reverse: who reads this cell', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'A1', '5');
+    setCell(s, name, 'B1', '=A1*2');
+    setCell(s, name, 'C1', '=A1+1');
+    const { col, row } = coords('A1');
+    const { dependents } = s.cellGraphNeighbors(id, col, row);
+    expect(dependents.map((n) => n.label).sort()).toEqual(['B1', 'C1']);
+  });
+
+  it('follows a cross-table reference, labelling with the other table/sheet name', () => {
+    const s = fresh();
+    const src = s.addTable(s.doc.activeSheetId);
+    s.renameObject(src, 'Quelle4');
+    const dst = s.addTable(s.doc.activeSheetId);
+    s.renameObject(dst, 'Ziel4');
+    setCell(s, 'Quelle4', 'B2', '42');
+    setCell(s, 'Ziel4', 'A1', '=Quelle4!B2');
+    const { col, row } = coords('A1');
+    const { precedents } = s.cellGraphNeighbors(dst, col, row);
+    expect(precedents).toHaveLength(1);
+    expect(precedents[0]).toMatchObject({ tableId: src, tableName: 'Quelle4', label: 'B2', value: 42 });
+  });
+
+  it('flags a cell on a circular reference via isCircular', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'A1', '=B1');
+    setCell(s, name, 'B1', '=A1');
+    const { col, row } = coords('A1');
+    expect(s.cellGraphSelf(id, col, row)!.isCircular).toBe(true);
+    // the edge itself is still reported even though the cell is circular
+    const { precedents } = s.cellGraphNeighbors(id, col, row);
+    expect(precedents.map((n) => n.label)).toEqual(['B1']);
+  });
+
+  it('a literal (non-formula) cell has no precedents; an unreferenced cell has no dependents', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'A1', '5');
+    const { col, row } = coords('A1');
+    const { precedents, dependents } = s.cellGraphNeighbors(id, col, row);
+    expect(precedents).toEqual([]);
+    expect(dependents).toEqual([]);
+  });
+
+  it('reflects a re-edit (e.g. after changing which cell a formula reads)', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const name = s.tableById(id)!.name;
+    setCell(s, name, 'B2', '1');
+    setCell(s, name, 'B3', '2');
+    setCell(s, name, 'C1', '=B2');
+    const { col, row } = coords('C1');
+    expect(s.cellGraphNeighbors(id, col, row).precedents.map((n) => n.label)).toEqual(['B2']);
+    setCell(s, name, 'C1', '=B3');
+    expect(s.cellGraphNeighbors(id, col, row).precedents.map((n) => n.label)).toEqual(['B3']);
+  });
+});
+
+describe('openDependencyGraph/closeDependencyGraph (the drawer, not just the data)', () => {
+  it('opens the drawer centered on the given cell', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const { col, row } = coords('B2');
+    expect(s.ui.depGraph).toBeNull();
+    s.openDependencyGraph(id, col, row);
+    expect(s.ui.depGraph).toEqual({ tableId: id, col, row });
+  });
+
+  it('also really selects the cell -- the rest of the app (selection) reflects where you navigated', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    const { col, row } = coords('C3');
+    s.openDependencyGraph(id, col, row);
+    expect(s.doc.selection).toMatchObject({ tableId: id, anchor: { col, row }, focus: { col, row } });
+    expect(s.doc.activeObjectId).toBe(id);
+  });
+
+  it('switches the active sheet tab when navigating to a cell on a different sheet', () => {
+    const s = fresh();
+    const otherSheet = s.addSheet();
+    const id = s.addTable(otherSheet);
+    expect(s.doc.activeSheetId).toBe(otherSheet); // addTable already switched here
+    s.setActiveSheet(s.doc.sheets[0].id); // move away
+    expect(s.doc.activeSheetId).not.toBe(otherSheet);
+
+    s.openDependencyGraph(id, 0, 0);
+    expect(s.doc.activeSheetId).toBe(otherSheet); // navigated back automatically
+  });
+
+  it('closeDependencyGraph clears it without touching the current selection', () => {
+    const s = fresh();
+    const id = s.addTable(s.doc.activeSheetId);
+    s.openDependencyGraph(id, 0, 0);
+    s.closeDependencyGraph();
+    expect(s.ui.depGraph).toBeNull();
+    expect(s.doc.selection).toMatchObject({ tableId: id, focus: { col: 0, row: 0 } });
+  });
+});
+
 describe('functionSuggestions (formula autocomplete)', () => {
   it('filters built-ins by prefix, case-insensitively', () => {
     const s = fresh();
diff --git a/src/store/document.ts b/src/store/document.ts
index 75412e6..bf12157 100644
--- a/src/store/document.ts
+++ b/src/store/document.ts
@@ -35,6 +35,7 @@ import {
   blockAlwaysReturns,
   parseDateTimeLiteral,
   BUILTIN_SIGNATURES,
+  type CellRef,
   type CellValue,
   type TableModel,
   type Token,
@@ -51,6 +52,7 @@ import {
 import type {
   CellCoord,
   CellFormat,
+  CellGraphNode,
   ChartObject,
   CustomFunction,
   DocumentState,
@@ -423,7 +425,14 @@ function createStore() {
   const bump = () => (recalcTick.value += 1);
 
   /** View-only state: not part of the document, not persisted. */
-  const ui = reactive({ settingsOpen: false });
+  const ui = reactive({
+    settingsOpen: false,
+    /** The dependency-graph drawer's centered cell, or `null` when closed
+     *  -- a single document-wide panel (like `settingsOpen`), not owned by
+     *  any one `TableGrid` instance, so navigating across tables/sheets
+     *  inside it doesn't depend on which grid happened to open it. */
+    depGraph: null as { tableId: string; col: number; row: number } | null,
+  });
   /** Copy/cut buffer -- not part of the persisted document. */
   const clipboard = ref<ClipboardData | null>(null);
   /** Whichever formula editor is currently open (in-cell editor or formula
@@ -1244,6 +1253,70 @@ function createStore() {
   const cellIsError = (t: string, c: number, r: number) => isError(cellValue(t, c, r));
   const cellIsFormula = (t: string, c: number, r: number) => cellInput(t, c, r).startsWith('=');
 
+  // ---- dependency-graph view (precedents/dependents of a cell) ---------
+  const isCellCircular = (v: CellValue): boolean => isError(v) && v.code === '#CIRC';
+  function describeCellRef(ref: CellRef): CellGraphNode | null {
+    const table = tableById(ref.tableId);
+    if (!table) return null; // dangling (table deleted mid-navigation) -- drop it
+    const sheetId = sheetIdOfObject(ref.tableId);
+    const sheetName = (sheetId && sheetById(sheetId)?.name) || '';
+    const value = wb.cellValue(ref.tableId, ref.col, ref.row);
+    return {
+      tableId: ref.tableId,
+      tableName: table.name,
+      sheetName,
+      col: ref.col,
+      row: ref.row,
+      label: toA1(ref.col, ref.row),
+      raw: cellInput(ref.tableId, ref.col, ref.row),
+      value,
+      isCircular: isCellCircular(value),
+    };
+  }
+  /** Stable render order -- a `Set`'s iteration order is otherwise
+   *  insertion-order-dependent and would make the graph view jump around
+   *  on every re-render for no reason. */
+  const graphNodeSort = (a: CellGraphNode, b: CellGraphNode): number =>
+    a.tableName.localeCompare(b.tableName) || a.row - b.row || a.col - b.col;
+
+  /** The centered cell itself, described the same way as a precedent/
+   *  dependent node -- null if its table no longer exists. */
+  function cellGraphSelf(tableId: string, col: number, row: number): CellGraphNode | null {
+    void recalcTick.value;
+    return describeCellRef({ tableId, col, row });
+  }
+  /** Direct precedents/dependents of a cell (see engine/graph.ts), enriched
+   *  for display -- the data source for the interactive dependency-graph
+   *  view (`DependencyGraphView.vue`). */
+  function cellGraphNeighbors(
+    tableId: string,
+    col: number,
+    row: number,
+  ): { precedents: CellGraphNode[]; dependents: CellGraphNode[] } {
+    void recalcTick.value;
+    const toNodes = (refs: CellRef[]) =>
+      refs.map(describeCellRef).filter((n): n is CellGraphNode => n !== null).sort(graphNodeSort);
+    return {
+      precedents: toNodes(wb.graphPrecedents(tableId, col, row)),
+      dependents: toNodes(wb.graphDependents(tableId, col, row)),
+    };
+  }
+  /** Opens the dependency-graph drawer centered on this cell -- also *really*
+   *  selects it (via the existing `selectCell`, which already switches the
+   *  active sheet/object as a side effect), so the sheet tabs, canvas,
+   *  formula bar and status bar all reflect where you are, not just the
+   *  drawer itself. Reused as-is for navigating *inside* the already-open
+   *  drawer (clicking a precedent/dependent node calls this again) -- a
+   *  jump across sheets/tables inside the graph is then indistinguishable
+   *  from clicking that cell directly. */
+  function openDependencyGraph(tableId: string, col: number, row: number) {
+    selectCell(tableId, col, row);
+    ui.depGraph = { tableId, col, row };
+  }
+  function closeDependencyGraph() {
+    ui.depGraph = null;
+  }
+
   // ---- cell writes --------------------------------------
   function setCellInput(tableId: string, col: number, row: number, raw: string) {
     const table = tableById(tableId);
@@ -2157,6 +2230,10 @@ function createStore() {
     cellIsNumeric,
     cellIsError,
     cellIsFormula,
+    cellGraphSelf,
+    cellGraphNeighbors,
+    openDependencyGraph,
+    closeDependencyGraph,
     setCellInput,
     clearRange,
     addRows,
diff --git a/src/store/types.ts b/src/store/types.ts
index 94cee01..03dfbbf 100644
--- a/src/store/types.ts
+++ b/src/store/types.ts
@@ -6,6 +6,7 @@
  */
 
 import type { NumberLocale } from './format';
+import type { CellValue } from '../engine';
 
 export interface CellCoord {
   col: number;
@@ -201,6 +202,28 @@ export interface FnSuggestion {
   kind: 'builtin' | 'custom';
 }
 
+/** One node of the interactive dependency-graph view (document.ts's
+ *  `cellGraphNeighbors()`/`cellGraphSelf()`) -- a precedent/dependent cell
+ *  (or the centered cell itself), enriched with what the UI needs to
+ *  render and label it without a second lookup. */
+export interface CellGraphNode {
+  tableId: string;
+  tableName: string;
+  /** the sheet the table lives on -- shown only when navigating makes the
+   *  centered cell's own sheet ambiguous otherwise. */
+  sheetName: string;
+  col: number;
+  row: number;
+  /** A1 label within its table, e.g. "B5" (never table/sheet-qualified --
+   *  the UI adds that itself from `tableName`/`sheetName` as needed). */
+  label: string;
+  /** raw input (formula text or literal), for a tooltip/detail view. */
+  raw: string;
+  value: CellValue;
+  /** this cell's *own* value is `#CIRC` -- it sits on a circular reference. */
+  isCircular: boolean;
+}
+
 export interface DocumentState {
   version: 2;
   sheets: Sheet[];