diff --git a/CHANGELOG.md b/CHANGELOG.md
index c35373c..3a44ec6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,7 @@
 
 **Insert**
 - Tables: insert via size picker, Word-style row/column drag-resize, add / delete rows & columns, delete table, cell borders, merge cells and split cells (N×M, Word/LibreOffice-style), cell background shading, header-row toggle (bold + shading); a table splits cleanly across page boundaries
+- Table border control (Word/LibreOffice-style): per-side cell borders with presets (all / outside / inside / single edges / none), line width and color; buttons show active states matching the current pen and toggle borders off; round-trips to ODF `fo:border-*` and DOCX `w:tcBorders`
 - Images: inline or floating with text wrap (left / right / top-bottom), resize handles, rotation, live size badge; insert via toolbar, drag-and-drop, or paste
 - Special characters picker
 - Table of contents: generated from headings (H1–H3) with live page numbers and dot leaders, click an entry to jump to its heading; round-trips to ODF `text:table-of-content` and a Word TOC field
diff --git a/src/lib/components/TableBorderPicker.svelte b/src/lib/components/TableBorderPicker.svelte
new file mode 100644
index 0000000..61cf660
--- /dev/null
+++ b/src/lib/components/TableBorderPicker.svelte
@@ -0,0 +1,310 @@
+<script lang="ts">
+  import type { Editor } from '@tiptap/core';
+  import { activeBorderPresets, type BorderPreset } from '../editor/extensions/tableCellBorders';
+
+  let { editor, tick }: { editor: Editor | null; tick: number } = $props();
+
+  let open = $state(false);
+  // Pen settings (Word-style): presets apply with the currently chosen width/color.
+  let widthPt = $state(0.5);
+  let color = $state('#000000');
+
+  const WIDTHS = [0.5, 1, 1.5, 2.25, 3];
+  // Greyscale + standard hues (the first two ColorPicker palette rows).
+  const COLORS = [
+    ['#000000', '#1A1A1A', '#333333', '#4D4D4D', '#666666', '#808080', '#999999', '#B3B3B3', '#CCCCCC', '#FFFFFF'],
+    ['#C00000', '#FF0000', '#FFC000', '#FFFF00', '#92D050', '#00B050', '#00B0F0', '#0070C0', '#002060', '#7030A0'],
+  ];
+
+  // Preset icons: 6 segments (outer edges + the two inner grid lines); "on" segments
+  // draw solid, the rest as faint guides.
+  type Seg = 'top' | 'right' | 'bottom' | 'left' | 'h' | 'v';
+  const SEG_PATH: Record<Seg, string> = {
+    top: 'M2 2H16', right: 'M16 2V16', bottom: 'M2 16H16', left: 'M2 2V16',
+    h: 'M2 9H16', v: 'M9 2V16',
+  };
+  const ALL_SEGS: Seg[] = ['top', 'right', 'bottom', 'left', 'h', 'v'];
+  const PRESETS: { id: BorderPreset | 'none'; title: string; on: Seg[] }[] = [
+    { id: 'all', title: 'All borders', on: ['top', 'right', 'bottom', 'left', 'h', 'v'] },
+    { id: 'outer', title: 'Outside borders', on: ['top', 'right', 'bottom', 'left'] },
+    { id: 'inner', title: 'Inside borders', on: ['h', 'v'] },
+    { id: 'innerH', title: 'Inside horizontal border', on: ['h'] },
+    { id: 'innerV', title: 'Inside vertical border', on: ['v'] },
+    { id: 'top', title: 'Top border', on: ['top'] },
+    { id: 'bottom', title: 'Bottom border', on: ['bottom'] },
+    { id: 'left', title: 'Left border', on: ['left'] },
+    { id: 'right', title: 'Right border', on: ['right'] },
+    { id: 'none', title: 'No border', on: [] },
+  ];
+
+  // Word-like button states, re-read per transaction (tick) and pen change: a preset
+  // is active when its boundaries all render the pen border; 'none' when borderless.
+  const active = $derived(
+    tick >= 0 && editor ? activeBorderPresets(editor.state, { widthPt, color }) : null,
+  );
+
+  // Clicking an inactive preset applies the pen; clicking an active one toggles those
+  // borders off (Word behavior). The panel stays open so the states visibly update.
+  function apply(id: BorderPreset | 'none') {
+    if (!editor) return;
+    if (id === 'none') editor.chain().focus().setTableBorders('all', null).run();
+    else if (active?.[id]) editor.chain().focus().setTableBorders(id, null).run();
+    else editor.chain().focus().setTableBorders(id, { widthPt, color }).run();
+  }
+
+  function clickOutside(node: HTMLElement) {
+    function handler(e: MouseEvent) {
+      if (!node.contains(e.target as Node)) open = false;
+    }
+    window.addEventListener('mousedown', handler);
+    return { destroy() { window.removeEventListener('mousedown', handler); } };
+  }
+</script>
+
+<div class="border-picker" use:clickOutside>
+  <button
+    class="bp-trigger"
+    class:active={open}
+    title="Borders"
+    aria-label="Borders"
+    aria-expanded={open}
+    onclick={() => (open = !open)}
+  >
+    <svg width="16" height="16" viewBox="0 0 18 18" fill="none" aria-hidden="true">
+      <rect x="2.5" y="2.5" width="13" height="13" stroke="currentColor" stroke-width="1.3"/>
+      <path d="M9 2.5V15.5M2.5 9H15.5" stroke="currentColor" stroke-width="1.1" stroke-dasharray="1.6 1.6"/>
+    </svg>
+    <svg class="bp-chevron" width="8" height="8" viewBox="0 0 8 8" fill="none" aria-hidden="true">
+      <path d="M1 2.5l3 3 3-3" stroke="currentColor" stroke-width="1.4" stroke-linecap="round" stroke-linejoin="round"/>
+    </svg>
+  </button>
+
+  {#if open}
+    <div class="bp-dropdown">
+      <div class="bp-title">Borders</div>
+      <div class="bp-presets">
+        {#each PRESETS as preset}
+          <button
+            class="bp-preset"
+            class:active={!!active?.[preset.id]}
+            title={preset.title}
+            aria-label={preset.title}
+            aria-pressed={!!active?.[preset.id]}
+            onclick={() => apply(preset.id)}
+          >
+            {#if preset.id === 'none'}
+              <!-- Prohibition sign over a faint grid: unmistakably "remove borders". -->
+              <svg width="18" height="18" viewBox="0 0 18 18" fill="none" aria-hidden="true">
+                {#each ALL_SEGS as seg}
+                  <path d={SEG_PATH[seg]} stroke="currentColor" stroke-width="1" opacity="0.22" stroke-dasharray="1.4 1.4"/>
+                {/each}
+                <circle cx="9" cy="9" r="4.6" fill="var(--color-surface)" stroke="currentColor" stroke-width="1.3"/>
+                <path d="M5.9 12.1L12.1 5.9" stroke="currentColor" stroke-width="1.3" stroke-linecap="round"/>
+              </svg>
+            {:else}
+              <svg width="18" height="18" viewBox="0 0 18 18" fill="none" aria-hidden="true">
+                {#each ALL_SEGS as seg}
+                  {#if !preset.on.includes(seg)}
+                    <path d={SEG_PATH[seg]} stroke="currentColor" stroke-width="1" opacity="0.22" stroke-dasharray="1.4 1.4"/>
+                  {/if}
+                {/each}
+                {#each preset.on as seg}
+                  <path d={SEG_PATH[seg]} stroke="currentColor" stroke-width="1.7"/>
+                {/each}
+              </svg>
+            {/if}
+          </button>
+        {/each}
+      </div>
+
+      <div class="bp-title">Line width</div>
+      <div class="bp-widths">
+        {#each WIDTHS as w}
+          <button
+            class="bp-width"
+            class:active={widthPt === w}
+            title="{w}pt"
+            aria-label="{w}pt"
+            aria-pressed={widthPt === w}
+            onclick={() => (widthPt = w)}
+          >
+            <span class="bp-width-line" style="height: {Math.max(1, Math.round((w * 96) / 72))}px"></span>
+          </button>
+        {/each}
+      </div>
+
+      <div class="bp-title">Line color</div>
+      <div class="bp-colors">
+        {#each COLORS as row}
+          <div class="bp-color-row">
+            {#each row as c}
+              <button
+                class="bp-color"
+                class:active={color === c}
+                style="background: {c}"
+                title={c}
+                aria-label={c}
+                onclick={() => (color = c)}
+              ></button>
+            {/each}
+          </div>
+        {/each}
+      </div>
+    </div>
+  {/if}
+</div>
+
+<style>
+  .border-picker {
+    position: relative;
+  }
+
+  .bp-trigger {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    gap: 1px;
+    height: 1.7rem;
+    min-width: unset;
+    padding: 0 3px;
+    border: none;
+    border-radius: calc(var(--radius) - 2px);
+    background: transparent;
+    color: var(--color-text);
+    cursor: pointer;
+    transition: background 0.12s, color 0.12s;
+  }
+
+  .bp-trigger:hover,
+  .bp-trigger.active {
+    background: var(--color-btn-hover);
+  }
+
+  .bp-chevron {
+    flex-shrink: 0;
+  }
+
+  .bp-dropdown {
+    position: absolute;
+    top: calc(100% + 3px);
+    left: 0;
+    z-index: 200;
+    display: flex;
+    flex-direction: column;
+    gap: 4px;
+    padding: 6px;
+    background: var(--color-surface);
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius);
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
+  }
+
+  .bp-title {
+    padding: 0.1rem 0.2rem 0.2rem;
+    font-size: 0.65rem;
+    font-weight: 600;
+    text-transform: uppercase;
+    letter-spacing: 0.06em;
+    color: var(--color-text);
+    font-family: var(--font-sans);
+    user-select: none;
+  }
+
+  .bp-presets {
+    display: grid;
+    grid-template-columns: repeat(5, 1fr);
+    gap: 2px;
+  }
+
+  .bp-preset {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    width: 1.9rem;
+    height: 1.9rem;
+    min-width: unset;
+    padding: 0;
+    border: 1px solid var(--color-border);
+    border-radius: calc(var(--radius) - 2px);
+    background: transparent;
+    color: var(--color-text);
+    cursor: pointer;
+    transition: background 0.1s;
+  }
+
+  .bp-preset:hover {
+    background: var(--color-btn-hover);
+  }
+
+  .bp-preset.active {
+    outline: 2px solid var(--color-primary);
+    outline-offset: -1px;
+  }
+
+  .bp-widths {
+    display: flex;
+    gap: 2px;
+  }
+
+  .bp-width {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    flex: 1;
+    height: 1.4rem;
+    min-width: unset;
+    padding: 0 4px;
+    border: 1px solid var(--color-border);
+    border-radius: calc(var(--radius) - 2px);
+    background: transparent;
+    color: var(--color-text);
+    cursor: pointer;
+    transition: background 0.1s;
+  }
+
+  .bp-width:hover {
+    background: var(--color-btn-hover);
+  }
+
+  .bp-width.active {
+    outline: 2px solid var(--color-primary);
+    outline-offset: -1px;
+  }
+
+  .bp-width-line {
+    display: block;
+    width: 100%;
+    background: currentColor;
+  }
+
+  .bp-colors {
+    display: flex;
+    flex-direction: column;
+    gap: 2px;
+  }
+
+  .bp-color-row {
+    display: flex;
+    gap: 2px;
+  }
+
+  .bp-color {
+    width: 18px;
+    height: 18px;
+    min-width: unset;
+    padding: 0;
+    border: 1px solid var(--color-border);
+    border-radius: 2px;
+    cursor: pointer;
+    transition: transform 0.05s;
+  }
+
+  .bp-color:hover {
+    transform: scale(1.15);
+  }
+
+  .bp-color.active {
+    outline: 2px solid var(--color-primary);
+    outline-offset: 1px;
+  }
+</style>
diff --git a/src/lib/components/TableToolbar.svelte b/src/lib/components/TableToolbar.svelte
index ac1353b..b34d918 100644
--- a/src/lib/components/TableToolbar.svelte
+++ b/src/lib/components/TableToolbar.svelte
@@ -3,6 +3,7 @@
   import { CellSelection } from '@tiptap/pm/tables';
   import { isHeaderRowStyled } from '../editor/extensions/tableHeaderRow';
   import ColorPicker from './ColorPicker.svelte';
+  import TableBorderPicker from './TableBorderPicker.svelte';
 
   let {
     editor,
@@ -210,6 +211,8 @@
     {/snippet}
   </ColorPicker>
 
+  <TableBorderPicker {editor} {tick} />
+
   <span class="tt-sep"></span>
 
   <button
diff --git a/src/lib/editor/extensions.ts b/src/lib/editor/extensions.ts
index a61ae66..68c1a99 100644
--- a/src/lib/editor/extensions.ts
+++ b/src/lib/editor/extensions.ts
@@ -36,6 +36,7 @@ import { TableColumnResize } from './extensions/tableColumnResize';
 import { TableRowResize } from './extensions/tableRowResize';
 import { TableSplit } from './extensions/tableSplit';
 import { TableCellBackground } from './extensions/tableCellBackground';
+import { TableCellBorders } from './extensions/tableCellBorders';
 import { TableHeaderRow } from './extensions/tableHeaderRow';
 import { TrailingNode } from './extensions/trailingNode';
 import { Image } from './extensions/image';
@@ -98,6 +99,8 @@ export const extensions = [
   TableSplit,
   // Cell shading: backgroundColor attr on tableCell/tableHeader (→ fo:background-color).
   TableCellBackground,
+  // Word-style border presets: per-side border attrs on cells (→ fo:border-*).
+  TableCellBorders,
   // "Header row" styling preset: bold + light shading on the first row (toggle).
   TableHeaderRow,
   // Guarantees a paragraph after a trailing table so the cursor isn't trapped
diff --git a/src/lib/editor/extensions/tableCellBorders.ts b/src/lib/editor/extensions/tableCellBorders.ts
new file mode 100644
index 0000000..8e577a9
--- /dev/null
+++ b/src/lib/editor/extensions/tableCellBorders.ts
@@ -0,0 +1,239 @@
+import { Extension } from '@tiptap/core';
+import type { CommandProps } from '@tiptap/core';
+import type { EditorState } from '@tiptap/pm/state';
+import { selectedRect, isInTable } from '@tiptap/pm/tables';
+
+// Word/LibreOffice table borders: per-side attrs (`borderTop/Right/Bottom/Left`) on
+// table cells. `null` = the table default (0.5pt solid black), `'none'` = no border,
+// else the canonical `'<W>pt solid #RRGGBB'`. Round-trips to ODF fo:border-* and DOCX
+// w:tcBorders (export/odt.ts exportTable, import/odt.ts convertTable, export/import
+// docx.ts). setTableBorders applies a Word-style preset to the selected cell region,
+// writing BOTH sides of every affected boundary (incl. the facing side of neighbour
+// cells outside the region) so collapsed borders never disagree between two cells.
+
+export const DEFAULT_BORDER_WIDTH_PT = 0.5;
+export const DEFAULT_BORDER_COLOR = '#000000';
+
+export type BorderPreset =
+  | 'all' | 'outer' | 'inner' | 'innerH' | 'innerV'
+  | 'top' | 'bottom' | 'left' | 'right';
+// null = no border ('none').
+export type BorderSpec = { widthPt: number; color: string } | null;
+
+export const BORDER_SIDES = ['borderTop', 'borderRight', 'borderBottom', 'borderLeft'] as const;
+export type BorderSide = (typeof BORDER_SIDES)[number];
+
+declare module '@tiptap/core' {
+  interface Commands<ReturnType> {
+    tableCellBorders: {
+      setTableBorders: (preset: BorderPreset, spec: BorderSpec) => ReturnType;
+    };
+  }
+}
+
+// Canonical attr value for a spec; the editor default collapses to null.
+export function borderAttrValue(spec: BorderSpec): string | null {
+  if (!spec) return 'none';
+  const w = Math.round(spec.widthPt * 100) / 100;
+  const color = spec.color.toUpperCase();
+  if (w === DEFAULT_BORDER_WIDTH_PT && color === DEFAULT_BORDER_COLOR) return null;
+  return `${w}pt solid ${color}`;
+}
+
+// null = table default, 'none' = no border, else width/color of a custom border.
+export function parseBorderAttr(
+  value: string | null | undefined,
+): { widthPt: number; color: string } | 'none' | null {
+  if (value == null) return null;
+  if (value === 'none') return 'none';
+  const m = /^([\d.]+)pt solid (#[0-9A-Fa-f]{6})$/.exec(value);
+  if (!m) return null;
+  return { widthPt: parseFloat(m[1]), color: m[2].toUpperCase() };
+}
+
+// CSS value for a side. The default 0.5pt renders as 1px (editor.css); custom widths
+// scale the same way (pt → px, min 1px so thin lines stay crisp).
+function cssBorder(value: string): string | null {
+  const b = parseBorderAttr(value);
+  if (b === null) return null;
+  if (b === 'none') return 'none';
+  const px = Math.max(1, Math.round((b.widthPt * 96) / 72));
+  return `${px}px solid ${b.color}`;
+}
+
+const SIDE_META: Record<BorderSide, { data: string; css: string }> = {
+  borderTop: { data: 'data-border-top', css: 'border-top' },
+  borderRight: { data: 'data-border-right', css: 'border-right' },
+  borderBottom: { data: 'data-border-bottom', css: 'border-bottom' },
+  borderLeft: { data: 'data-border-left', css: 'border-left' },
+};
+
+// Walks every boundary a preset targets in the selected rect, reporting the two
+// facing (cellPos, side) pairs of each; a pos is null at the table edge. Boundaries
+// running inside a merged cell are skipped. Shared by the setTableBorders command
+// and the active-preset reader below.
+function forEachBoundary(
+  rect: ReturnType<typeof selectedRect>,
+  preset: BorderPreset,
+  cb: (aPos: number | null, aSide: BorderSide, bPos: number | null, bSide: BorderSide) => void,
+): void {
+  const { map } = rect;
+  const wants = {
+    topEdge: preset === 'all' || preset === 'outer' || preset === 'top',
+    bottomEdge: preset === 'all' || preset === 'outer' || preset === 'bottom',
+    leftEdge: preset === 'all' || preset === 'outer' || preset === 'left',
+    rightEdge: preset === 'all' || preset === 'outer' || preset === 'right',
+    innerH: preset === 'all' || preset === 'inner' || preset === 'innerH',
+    innerV: preset === 'all' || preset === 'inner' || preset === 'innerV',
+  };
+
+  // Horizontal boundaries: grid line y separates row y-1 (above) from row y (below).
+  for (let y = rect.top; y <= rect.bottom; y++) {
+    const isTop = y === rect.top;
+    const isBottom = y === rect.bottom;
+    if (isTop && !wants.topEdge) continue;
+    if (isBottom && !wants.bottomEdge) continue;
+    if (!isTop && !isBottom && !wants.innerH) continue;
+    for (let x = rect.left; x < rect.right; x++) {
+      const below = y < map.height ? map.map[y * map.width + x] : null;
+      const above = y > 0 ? map.map[(y - 1) * map.width + x] : null;
+      if (above === below) continue; // grid line runs inside a merged cell
+      cb(above, 'borderBottom', below, 'borderTop');
+    }
+  }
+  // Vertical boundaries: grid line x separates column x-1 (left) from column x (right).
+  for (let x = rect.left; x <= rect.right; x++) {
+    const isLeft = x === rect.left;
+    const isRight = x === rect.right;
+    if (isLeft && !wants.leftEdge) continue;
+    if (isRight && !wants.rightEdge) continue;
+    if (!isLeft && !isRight && !wants.innerV) continue;
+    for (let y = rect.top; y < rect.bottom; y++) {
+      const right = x < map.width ? map.map[y * map.width + x] : null;
+      const left = x > 0 ? map.map[y * map.width + (x - 1)] : null;
+      if (left === right) continue;
+      cb(left, 'borderRight', right, 'borderLeft');
+    }
+  }
+}
+
+export function setTableBorders(preset: BorderPreset, spec: BorderSpec) {
+  return ({ state, tr, dispatch }: CommandProps): boolean => {
+    if (!isInTable(state)) return false;
+    if (!dispatch) return true;
+
+    const rect = selectedRect(state);
+    const value = borderAttrValue(spec);
+
+    // pos (relative to tableStart) → attr changes, deduped across grid slots of a span.
+    const changes = new Map<number, Record<string, string | null>>();
+    const set = (pos: number | null, side: BorderSide) => {
+      if (pos == null) return;
+      const c = changes.get(pos) ?? {};
+      c[side] = value;
+      changes.set(pos, c);
+    };
+    forEachBoundary(rect, preset, (aPos, aSide, bPos, bSide) => {
+      set(aPos, aSide);
+      set(bPos, bSide);
+    });
+
+    // setNodeMarkup doesn't shift positions, so all cell positions stay valid.
+    for (const [pos, attrs] of changes) {
+      const cell = tr.doc.nodeAt(rect.tableStart + pos);
+      if (!cell) continue;
+      tr.setNodeMarkup(rect.tableStart + pos, undefined, { ...cell.attrs, ...attrs });
+    }
+    dispatch(tr);
+    return true;
+  };
+}
+
+export const BORDER_PRESETS: BorderPreset[] = [
+  'all', 'outer', 'inner', 'innerH', 'innerV', 'top', 'bottom', 'left', 'right',
+];
+
+// What a boundary renders: the collapse winner of its two facing cell sides
+// (a border beats 'none', wider beats narrower; attr null = the table default).
+type EffectiveBorder = { widthPt: number; color: string } | 'none';
+
+// Word-like active states for the picker: a preset is active when every boundary it
+// targets renders exactly the pen border (width + color) — so with the default thin
+// pen a fresh table lights up every preset; picking a thicker pen turns them off.
+// 'none' is active when the whole region renders borderless. null outside a table.
+export function activeBorderPresets(
+  state: EditorState,
+  spec: Exclude<BorderSpec, null>,
+): Record<BorderPreset | 'none', boolean> | null {
+  if (!isInTable(state)) return null;
+  const rect = selectedRect(state);
+
+  const sideEff = (pos: number | null, side: BorderSide): EffectiveBorder | null => {
+    if (pos == null) return null;
+    const b = parseBorderAttr(state.doc.nodeAt(rect.tableStart + pos)?.attrs[side] as string | null);
+    return b ?? { widthPt: DEFAULT_BORDER_WIDTH_PT, color: DEFAULT_BORDER_COLOR };
+  };
+  const boundaryEff = (aPos: number | null, aSide: BorderSide, bPos: number | null, bSide: BorderSide): EffectiveBorder => {
+    let best: EffectiveBorder = 'none';
+    for (const v of [sideEff(aPos, aSide), sideEff(bPos, bSide)]) {
+      if (v == null || v === 'none') continue;
+      if (best === 'none' || v.widthPt > best.widthPt) best = v;
+    }
+    return best;
+  };
+  const matchesPen = (v: EffectiveBorder) =>
+    v !== 'none' && Math.abs(v.widthPt - spec.widthPt) < 0.01 && v.color === spec.color.toUpperCase();
+
+  const out = {} as Record<BorderPreset | 'none', boolean>;
+  for (const preset of BORDER_PRESETS) {
+    let n = 0;
+    let active = true;
+    forEachBoundary(rect, preset, (aPos, aSide, bPos, bSide) => {
+      n++;
+      if (!matchesPen(boundaryEff(aPos, aSide, bPos, bSide))) active = false;
+    });
+    out[preset] = n > 0 && active;
+  }
+  let n = 0;
+  let allNone = true;
+  forEachBoundary(rect, 'all', (aPos, aSide, bPos, bSide) => {
+    n++;
+    if (boundaryEff(aPos, aSide, bPos, bSide) !== 'none') allNone = false;
+  });
+  out.none = n > 0 && allNone;
+  return out;
+}
+
+export const TableCellBorders = Extension.create({
+  name: 'tableCellBorders',
+
+  addGlobalAttributes() {
+    return [
+      {
+        types: ['tableCell', 'tableHeader'],
+        attributes: Object.fromEntries(
+          BORDER_SIDES.map((side) => [
+            side,
+            {
+              default: null,
+              parseHTML: (element: HTMLElement) => element.getAttribute(SIDE_META[side].data),
+              renderHTML: (attributes: Record<string, unknown>) => {
+                const v = attributes[side] as string | null;
+                if (!v) return {};
+                const css = cssBorder(v);
+                if (!css) return {};
+                return { [SIDE_META[side].data]: v, style: `${SIDE_META[side].css}: ${css}` };
+              },
+            },
+          ]),
+        ),
+      },
+    ];
+  },
+
+  addCommands() {
+    return {
+      setTableBorders: (preset: BorderPreset, spec: BorderSpec) => setTableBorders(preset, spec),
+    };
+  },
+});
diff --git a/src/lib/export/docx.ts b/src/lib/export/docx.ts
index 3eb8aa1..adb9716 100644
--- a/src/lib/export/docx.ts
+++ b/src/lib/export/docx.ts
@@ -18,6 +18,7 @@ import { DEFAULT_MARGINS, type PageMargins } from '../storage/pageMargins';
 import type { Orientation } from '../storage/pageOrientation';
 import { HF_DISTANCE_CM, hfIsEmpty } from '../storage/headerFooter';
 import { HEADER_SHADE } from '../editor/extensions/tableHeaderRow';
+import { parseBorderAttr, type BorderSide } from '../editor/extensions/tableCellBorders';
 import { orderedTypeDef } from '../utils/orderedListTypes';
 import { normalizeColor, HEADING_STYLE_OVERRIDES, type HfExport } from './odt';
 
@@ -608,6 +609,14 @@ function columnWidthsCm(node: TiptapNode, contentWidthCm: number): number[] | un
 
 const cellBorder: IBorderOptions = { style: BorderStyle.SINGLE, size: 4, color: '000000' }; // 0.5pt
 
+// A cell's per-side border attr → w:tcBorders options (size in eighth-points).
+function docxCellBorder(attrs: Record<string, unknown> | undefined, side: BorderSide): IBorderOptions {
+  const b = parseBorderAttr(attrs?.[side] as string | null);
+  if (b === 'none') return { style: BorderStyle.NONE, size: 0, color: 'auto' };
+  if (b) return { style: BorderStyle.SINGLE, size: Math.max(2, Math.round(b.widthPt * 8)), color: hexColor(b.color) ?? '000000' };
+  return cellBorder;
+}
+
 function cellBlocksToDocx(content: TiptapNode[] = [], headerBold: boolean, num: Numbering, contentWidthCm: number): (Paragraph | Table)[] {
   const out: (Paragraph | Table)[] = [];
   for (const child of content) {
@@ -646,7 +655,12 @@ function tableToDocx(node: TiptapNode, contentWidthCm: number, num: Numbering):
         rowSpan: rowspan > 1 ? rowspan : undefined,
         shading: fill ? { type: ShadingType.CLEAR, fill } : undefined,
         width: widthTwip ? { size: widthTwip, type: WidthType.DXA } : undefined,
-        borders: { top: cellBorder, bottom: cellBorder, left: cellBorder, right: cellBorder },
+        borders: {
+          top: docxCellBorder(cell.attrs, 'borderTop'),
+          bottom: docxCellBorder(cell.attrs, 'borderBottom'),
+          left: docxCellBorder(cell.attrs, 'borderLeft'),
+          right: docxCellBorder(cell.attrs, 'borderRight'),
+        },
         children: cellBlocksToDocx(cell.content, bg === HEADER_SHADE, num, contentWidthCm),
       }));
     }
diff --git a/src/lib/export/odt.ts b/src/lib/export/odt.ts
index 8ce2b84..6ac919c 100644
--- a/src/lib/export/odt.ts
+++ b/src/lib/export/odt.ts
@@ -4,6 +4,7 @@ import { DEFAULT_MARGINS, type PageMargins } from '../storage/pageMargins';
 import type { Orientation } from '../storage/pageOrientation';
 import { HF_DISTANCE_CM, hfIsEmpty, type HfDoc } from '../storage/headerFooter';
 import { HEADER_SHADE } from '../editor/extensions/tableHeaderRow';
+import { BORDER_SIDES, parseBorderAttr } from '../editor/extensions/tableCellBorders';
 import { TEXTBOX_PADDING_CM } from '../editor/extensions/textBox';
 import { DEFAULT_ORDERED_TYPE, orderedTypeDef } from '../utils/orderedListTypes';
 
@@ -1286,6 +1287,12 @@ function exportTable(node: TiptapNode, doc: OdtDocument, contentWidthCm: number,
             const c = normalizeColor(bg);
             if (c) opts.backgroundColor = c;
           }
+          // Per-side borders → fo:border-* (null = the table default border below).
+          for (const side of BORDER_SIDES) {
+            const b = parseBorderAttr(cell.attrs?.[side] as string | null);
+            if (b === 'none') opts[side] = 'none';
+            else if (b) opts[side] = `${b.widthPt}pt solid ${normalizeColor(b.color) ?? b.color}`;
+          }
           // Header-row cells render bold via CSS (presentational), so bake bold into the
           // runs on export to keep Word/LibreOffice consistent (incl. freshly-typed text).
           const headerBold = bg === HEADER_SHADE;
diff --git a/src/lib/import/docx.ts b/src/lib/import/docx.ts
index 94810b3..7d7da2f 100644
--- a/src/lib/import/docx.ts
+++ b/src/lib/import/docx.ts
@@ -722,14 +722,41 @@ function convertPict(pict: Element, ctx: Ctx): Node | null {
 }
 
 // ---- tables -----------------------------------------------------------------
+
+// A w:tcBorders/w:tblBorders side element → border attr value: null = the editor
+// default (0.5pt black), 'none', or '<W>pt solid #RRGGBB' (w:sz is eighth-points).
+// undefined when the element is absent (side not declared at this level).
+function docxBorderAttr(el: Element | null): string | null | undefined {
+  if (!el) return undefined;
+  const val = el.getAttributeNS(W, 'val');
+  if (!val || val === 'none' || val === 'nil') return 'none';
+  const sz = intAttr(el, W, 'sz');
+  const w = Math.round(((sz != null ? sz / 8 : 0.5)) * 100) / 100;
+  const c = (hexColor(el.getAttributeNS(W, 'color')) ?? '#000000').toUpperCase();
+  if (Math.abs(w - 0.5) < 0.11 && c === '#000000') return null;
+  return `${w}pt solid ${c}`;
+}
+
 function convertTable(tbl: Element, ctx: Ctx): Node | null {
   const grid = fc(tbl, 'tblGrid');
   const weights = grid ? fcAll(grid, 'gridCol').map((g) => Math.max(1, intAttr(g, W, 'w') ?? 1)) : null;
   const useWeights = weights && weights.length ? weights : null;
 
+  // Table-level border defaults; per-cell w:tcBorders override per side. Edge cells
+  // fall back to the outer sides, interior cells to insideH/insideV.
+  const tblBorders = fc(fc(tbl, 'tblPr'), 'tblBorders');
+  const tblSide = (name: string) => docxBorderAttr(fc(tblBorders, name));
+  const tblDef = {
+    top: tblSide('top'), bottom: tblSide('bottom'), left: tblSide('left'),
+    right: tblSide('right'), insideH: tblSide('insideH'), insideV: tblSide('insideV'),
+  };
+  const gridWidth = useWeights?.length ?? null;
+
   const rows: Node[] = [];
   const pending: (Node | null)[] = []; // origin cell per grid column, for vMerge spans
-  for (const tr of fcAll(tbl, 'tr')) {
+  const trs = fcAll(tbl, 'tr');
+  for (let ri = 0; ri < trs.length; ri++) {
+    const tr = trs[ri];
     const cells: Node[] = [];
     let col = 0;
     for (const tc of fcAll(tr, 'tc')) {
@@ -748,6 +775,20 @@ function convertTable(tbl: Element, ctx: Ctx): Node | null {
       const blocks = convertBlocks(Array.from(tc.children), ctx, 'cell', bg === HEADER_SHADE);
       const attrs: Record<string, unknown> = { colspan, rowspan: 1 };
       if (bg) attrs.backgroundColor = bg;
+      const tcBorders = fc(tcPr, 'tcBorders');
+      const isRight = gridWidth != null && col + colspan >= gridWidth;
+      const resolve = (name: string, tblVal: string | null | undefined) => {
+        const own = docxBorderAttr(fc(tcBorders, name));
+        return own !== undefined ? own : tblVal;
+      };
+      const sides: [string, string | null | undefined][] = [
+        ['borderTop', resolve('top', ri === 0 ? tblDef.top : tblDef.insideH)],
+        ['borderBottom', resolve('bottom', ri === trs.length - 1 ? tblDef.bottom : tblDef.insideH)],
+        ['borderLeft', resolve('left', col === 0 ? tblDef.left : tblDef.insideV)],
+        ['borderRight', resolve('right', isRight ? tblDef.right : tblDef.insideV)],
+      ];
+      // undefined (nothing declared) and null (= editor default) both leave the attr off.
+      for (const [attr, v] of sides) if (typeof v === 'string') attrs[attr] = v;
       if (useWeights) attrs.colwidth = useWeights.slice(col, col + colspan);
       const cell: Node = { type: 'tableCell', attrs, content: blocks.length ? blocks : [{ type: 'paragraph' }] };
       cells.push(cell);
diff --git a/src/lib/import/odt.ts b/src/lib/import/odt.ts
index 53e07ff..1064147 100644
--- a/src/lib/import/odt.ts
+++ b/src/lib/import/odt.ts
@@ -833,6 +833,28 @@ function listLevelDef(listStyle: Element | null, depth: number): Element | null
 
 // ---- tables ------------------------------------------------------------------------
 
+// ODF border ("0.5pt solid #000000" / "none" / absent) → border attr value: null for
+// the editor default (0.5pt black, tolerance for producer unit rounding), 'none' for
+// no border, else the canonical '<W>pt solid #RRGGBB'. Non-solid styles are coerced
+// to solid (the editor only renders solid lines).
+export function borderAttrFromOdf(raw: string | null | undefined): string | null {
+  if (!raw || raw === 'none' || raw === 'hidden') return 'none';
+  let widthPt: number | null = null;
+  let color: string | null = null;
+  let styleTok: string | null = null;
+  for (const part of raw.trim().split(/\s+/)) {
+    if (/^-?[\d.]+\s*(pt|cm|mm|in|px|pc)?$/.test(part)) widthPt = lengthToPt(part);
+    else if (part.startsWith('#')) color = normalizeColor(part) ?? part;
+    else styleTok = part;
+  }
+  if (styleTok === 'none' || styleTok === 'hidden') return 'none';
+  if (widthPt != null && widthPt <= 0) return 'none';
+  const w = Math.round((widthPt ?? 0.5) * 100) / 100;
+  const c = (color ?? '#000000').toUpperCase();
+  if (Math.abs(w - 0.5) < 0.11 && c === '#000000') return null;
+  return `${w}pt solid ${c}`;
+}
+
 function convertTable(el: Element, ctx: Ctx): Node | null {
   const weights = columnWeights(el, ctx.resolver);
 
@@ -851,13 +873,24 @@ function convertTable(el: Element, ctx: Ctx): Node | null {
 
       const colspan = parseInt(cellEl.getAttributeNS(NS.table, 'number-columns-spanned') ?? '1', 10) || 1;
       const rowspan = parseInt(cellEl.getAttributeNS(NS.table, 'number-rows-spanned') ?? '1', 10) || 1;
-      const rawBg = ctx.resolver.cellBackgroundColor(cellEl.getAttributeNS(NS.table, 'style-name'));
+      const cellStyleName = cellEl.getAttributeNS(NS.table, 'style-name');
+      const rawBg = ctx.resolver.cellBackgroundColor(cellStyleName);
       const backgroundColor = rawBg ? normalizeColor(rawBg) ?? rawBg : null;
+      // Per-side borders; an undeclared side means no border in ODF → 'none'.
+      // Only null (= the editor's 0.5pt-black default) is left off the attrs.
+      const rawBorders = ctx.resolver.cellBorders(cellStyleName);
+      const borders: Record<string, string> = {};
+      for (const [attr, side] of [
+        ['borderTop', 'top'], ['borderRight', 'right'], ['borderBottom', 'bottom'], ['borderLeft', 'left'],
+      ] as const) {
+        const v = borderAttrFromOdf(rawBorders[side]);
+        if (v !== null) borders[attr] = v;
+      }
       // Header-shaded cells render bold by default (CSS); convert their runs like headings
       // so a baked-bold run needs no mark and only an explicitly normal run gets one.
       const blocks = convertBlocks(Array.from(cellEl.children), ctx, 'cell', backgroundColor === HEADER_SHADE);
       for (let r = 0; r < repeated; r++) {
-        const attrs: Record<string, unknown> = { colspan, rowspan };
+        const attrs: Record<string, unknown> = { colspan, rowspan, ...borders };
         if (backgroundColor) attrs.backgroundColor = backgroundColor;
         if (weights) attrs.colwidth = weights.slice(colIndex, colIndex + colspan);
         cells.push({
diff --git a/src/lib/import/styleResolver.ts b/src/lib/import/styleResolver.ts
index 7b79dea..2340bb9 100644
--- a/src/lib/import/styleResolver.ts
+++ b/src/lib/import/styleResolver.ts
@@ -248,6 +248,21 @@ export class StyleResolver {
     return c && c !== 'transparent' && c !== 'none' ? c : null;
   }
 
+  // A cell style's raw fo:border-* values (per-side overriding the fo:border
+  // shorthand). Sides the style doesn't declare stay undefined (= no border in ODF).
+  cellBorders(styleName: string | null): Partial<Record<'top' | 'right' | 'bottom' | 'left', string>> {
+    if (!styleName) return {};
+    const misc = this.merged('table-cell', styleName).misc;
+    const all = misc['fo:border'];
+    const pick = (side: string) => misc[`fo:border-${side}`] ?? all;
+    const out: Partial<Record<'top' | 'right' | 'bottom' | 'left', string>> = {};
+    for (const side of ['top', 'right', 'bottom', 'left'] as const) {
+      const v = pick(side);
+      if (v != null) out[side] = v;
+    }
+    return out;
+  }
+
   listStyle(name: string | null): Element | null {
     return name ? this.listStyles.get(name) ?? null : null;
   }
diff --git a/tests/docx-roundtrip.test.ts b/tests/docx-roundtrip.test.ts
index e1aa5de..92668af 100644
--- a/tests/docx-roundtrip.test.ts
+++ b/tests/docx-roundtrip.test.ts
@@ -51,7 +51,7 @@ describe('DOCX export → import round trip', () => {
       { type: 'textBox', attrs: { width: 192, height: 96, wrap: 'right', shapeKind: 'ellipse', fillColor: '#FFEE00', strokeColor: '#FF0000', strokeWidthPt: 2.25, rotation: 30 }, content: [para('ellipse text')] },
       { type: 'table', content: [
         { type: 'tableRow', content: [headerCell('Name', { colwidth: [6] }), headerCell('Qty', { colwidth: [3] })] },
-        { type: 'tableRow', attrs: { rowHeight: 40 }, content: [cell('Widget', { backgroundColor: '#FFFF00', rowspan: 2 }), cell('1')] },
+        { type: 'tableRow', attrs: { rowHeight: 40 }, content: [cell('Widget', { backgroundColor: '#FFFF00', rowspan: 2 }), cell('1', { borderTop: 'none', borderRight: '2.25pt solid #FF0000' })] },
         { type: 'tableRow', content: [cell('2')] },
       ] },
     ],
@@ -157,6 +157,12 @@ describe('DOCX export → import round trip', () => {
     expect(widget.attrs.backgroundColor).toBe('#FFFF00');
     expect(rows[2].content!.length).toBe(1);
     expect(rows[1].attrs.rowHeight).toBe(40);
+    // per-side borders (w:tcBorders): hidden top + custom red right; defaults stay null
+    const qty = rows[1].content![1];
+    expect(qty.attrs.borderTop).toBe('none');
+    expect(qty.attrs.borderRight).toBe('2.25pt solid #FF0000');
+    expect(qty.attrs.borderBottom ?? null).toBe(null);
+    expect(widget.attrs.borderTop ?? null).toBe(null);
   });
 
   it('round-trips page geometry + header/footer with page fields', () => {
diff --git a/tests/lo-roundtrip.test.ts b/tests/lo-roundtrip.test.ts
index cd1ebee..c148d24 100644
--- a/tests/lo-roundtrip.test.ts
+++ b/tests/lo-roundtrip.test.ts
@@ -76,7 +76,7 @@ const fixture: N = {
       ] },
       { type: 'tableRow', content: [
         { type: 'tableCell', attrs: { colspan: 1, rowspan: 1, colwidth: [120] }, content: [P(null, T('A2'))] },
-        { type: 'tableCell', attrs: { colspan: 1, rowspan: 1, colwidth: [240] }, content: [P(null, T('B2'))] },
+        { type: 'tableCell', attrs: { colspan: 1, rowspan: 1, colwidth: [240], borderTop: 'none', borderRight: '2.25pt solid #FF0000' }, content: [P(null, T('B2'))] },
       ] },
     ] },
     TBX({ width: 288, height: 96, fillColor: '#FFFFFF', strokeColor: '#000000', strokeWidthPt: 1 },
@@ -114,6 +114,11 @@ function normalize(node: N): N {
     if (k === 'rotation') { attrs.rotation = 'R'; continue; } // exact angle checked leniently below
     if (k === 'wrap') { attrs.wrap = 'W'; continue; } // float survives; exact mode checked leniently
     if (k === 'strokeWidthPt') { attrs.strokeWidthPt = Math.round((v as number) * 4) / 4; continue; } // pt↔in noise
+    // Cell borders: LO re-saves widths with pt↔cm noise; quantize to 0.25pt steps.
+    if (k.startsWith('border') && typeof v === 'string' && v !== 'none') {
+      const bm = /^([\d.]+)pt solid (#[0-9A-F]{6})$/i.exec(v);
+      if (bm) { attrs[k] = `${Math.round(parseFloat(bm[1]) * 4) / 4}pt solid ${bm[2].toUpperCase()}`; continue; }
+    }
     if (k === 'fillColor' || k === 'strokeColor') { attrs[k] = typeof v === 'string' ? v.toUpperCase() : v; continue; }
     // LO re-parents text-box paragraphs onto its Frame-contents style (margin 0), so
     // an explicit spaceAfter 0 comes back where Standard's default was suppressed.
diff --git a/tests/roundtrip.test.ts b/tests/roundtrip.test.ts
index cb0b99e..f6efb09 100644
--- a/tests/roundtrip.test.ts
+++ b/tests/roundtrip.test.ts
@@ -328,6 +328,41 @@ describe('Leg 1c: header-row cells (bold-by-default, editable)', () => {
   });
 });
 
+describe('Leg 1d: table cell borders (per-side, fo:border-*)', () => {
+  const bcell = (text: string, borders: Record<string, string> = {}): N =>
+    ({ type: 'tableCell', attrs: { colspan: 1, rowspan: 1, colwidth: [100], ...borders }, content: [P(null, T(text))] });
+
+  // A: default borders (null attrs) · B: top hidden + custom red right ·
+  // C/D: fully borderless.
+  const doc: N = { type: 'doc', content: [
+    { type: 'table', content: [
+      ROW(bcell('A'), bcell('B', { borderTop: 'none', borderRight: '2.25pt solid #FF0000' })),
+      ROW(bcell('C', { borderTop: 'none', borderRight: 'none', borderBottom: 'none', borderLeft: 'none' }),
+          bcell('D', { borderTop: 'none', borderRight: 'none', borderBottom: 'none', borderLeft: 'none' })),
+    ] },
+  ] };
+
+  it('exports fo:border-* per side and re-imports the attrs', async () => {
+    const bytes = await buildOdt(doc, margins, 'portrait');
+    const xml = strFromU8(unzipSync(bytes)['content.xml']);
+    check('export emits fo:border-top="none"', xml.includes('fo:border-top="none"'), xml.match(/fo:border-top="[^"]*"/g));
+    check('export emits the custom red right border', xml.includes('fo:border-right="2.25pt solid #FF0000"'), xml.match(/fo:border-right="[^"]*"/g));
+
+    const res = importOdt(bytes);
+    check('no warnings on own export', res.warnings.length === 0, res.warnings);
+    const table = (res.content.content ?? []).find((n: N) => n.type === 'table');
+    const [row0, row1] = table?.content ?? [];
+    const a = row0?.content?.[0]?.attrs ?? {};
+    const b = row0?.content?.[1]?.attrs ?? {};
+    const c = row1?.content?.[0]?.attrs ?? {};
+    check('A keeps default borders (attrs null)', a.borderTop == null && a.borderRight == null && a.borderBottom == null && a.borderLeft == null, a);
+    check('B top border stays hidden', b.borderTop === 'none', b);
+    check('B custom right border round-trips', b.borderRight === '2.25pt solid #FF0000', b);
+    check('B bottom/left stay default', b.borderBottom == null && b.borderLeft == null, b);
+    check('C is fully borderless', c.borderTop === 'none' && c.borderRight === 'none' && c.borderBottom === 'none' && c.borderLeft === 'none', c);
+  });
+});
+
 describe('Leg 2: foreign (LibreOffice/Word-style) .odt → importOdt', () => {
   it('resolves named/automatic styles, repeated cells, lists, and reports degradations', () => {
     const stylesXml = `<?xml version="1.0" encoding="UTF-8"?>
diff --git a/tests/unit/table-borders.test.ts b/tests/unit/table-borders.test.ts
new file mode 100644
index 0000000..0df6a5f
--- /dev/null
+++ b/tests/unit/table-borders.test.ts
@@ -0,0 +1,245 @@
+// Unit tests for the table border feature: the setTableBorders preset command
+// (driven against a ProseMirror EditorState, like table-split.test.ts) and the
+// attr-value parse/normalize helpers used by export and import.
+import { describe, it, expect } from 'vitest';
+import { getSchema } from '@tiptap/core';
+import { EditorState, TextSelection } from '@tiptap/pm/state';
+import { CellSelection } from '@tiptap/pm/tables';
+import type { Node as PMNode } from '@tiptap/pm/model';
+import Document from '@tiptap/extension-document';
+import Paragraph from '@tiptap/extension-paragraph';
+import Text from '@tiptap/extension-text';
+import { Table, TableHeader, TableCell } from '@tiptap/extension-table';
+import { ResizableTableRow } from '../../src/lib/editor/extensions/tableRow';
+import {
+  TableCellBorders, setTableBorders, activeBorderPresets, borderAttrValue, parseBorderAttr,
+  type BorderPreset, type BorderSpec,
+} from '../../src/lib/editor/extensions/tableCellBorders';
+import { borderAttrFromOdf } from '../../src/lib/import/odt';
+
+type N = any;
+
+const schema = getSchema([
+  Document, Paragraph, Text, Table, ResizableTableRow, TableCell, TableHeader, TableCellBorders,
+]);
+
+const cell = (text: string): N => ({
+  type: 'tableCell',
+  attrs: { colspan: 1, rowspan: 1, colwidth: null },
+  content: [{ type: 'paragraph', content: [{ type: 'text', text }] }],
+});
+const row = (...cells: N[]): N => ({ type: 'tableRow', content: cells });
+// 3×3 grid: [A B C] / [D E F] / [G H I]
+const grid3 = (): N => ({
+  type: 'doc',
+  content: [{ type: 'table', content: [
+    row(cell('A'), cell('B'), cell('C')),
+    row(cell('D'), cell('E'), cell('F')),
+    row(cell('G'), cell('H'), cell('I')),
+  ] }],
+});
+
+function textPos(doc: PMNode, text: string): number {
+  let pos = -1;
+  doc.descendants((node: PMNode, p: number) => {
+    if (node.isText && node.text === text) pos = p;
+  });
+  if (pos < 0) throw new Error(`text ${text} not found`);
+  return pos;
+}
+
+function cellPos(doc: PMNode, text: string): number {
+  const $pos = doc.resolve(textPos(doc, text));
+  for (let d = $pos.depth; d > 0; d--) {
+    if ($pos.node(d).type.spec.tableRole === 'cell') return $pos.before(d);
+  }
+  throw new Error(`no cell around ${text}`);
+}
+
+// Run the command with the cursor in `target` (string) or a CellSelection over
+// [anchor, head] cells; returns cellText → border attrs for the whole table.
+function run(json: N, target: string | [string, string], preset: BorderPreset, spec: BorderSpec): Record<string, N> {
+  const doc = schema.nodeFromJSON(json);
+  const selection = typeof target === 'string'
+    ? TextSelection.create(doc, textPos(doc, target))
+    : new CellSelection(doc.resolve(cellPos(doc, target[0])), doc.resolve(cellPos(doc, target[1])));
+  const state = EditorState.create({ schema, doc, selection });
+  let next: EditorState | null = null;
+  const ok = setTableBorders(preset, spec)({
+    state,
+    tr: state.tr,
+    dispatch: (tr: any) => { next = state.apply(tr); },
+  } as any);
+  expect(ok).toBe(true);
+  const out: Record<string, N> = {};
+  next!.doc.descendants((node: PMNode) => {
+    if (node.type.spec.tableRole === 'cell') {
+      const { borderTop, borderRight, borderBottom, borderLeft } = node.attrs;
+      out[node.textContent] = { borderTop, borderRight, borderBottom, borderLeft };
+    }
+  });
+  return out;
+}
+
+const RED = { widthPt: 1, color: '#FF0000' };
+const V = '1pt solid #FF0000';
+
+describe('setTableBorders', () => {
+  it('"all" on a single cell sets its four sides and mirrors the facing neighbour sides', () => {
+    const t = run(grid3(), 'E', 'all', RED);
+    expect(t.E).toEqual({ borderTop: V, borderRight: V, borderBottom: V, borderLeft: V });
+    expect(t.B.borderBottom).toBe(V); // above
+    expect(t.H.borderTop).toBe(V);    // below
+    expect(t.D.borderRight).toBe(V);  // left
+    expect(t.F.borderLeft).toBe(V);   // right
+    // Corners untouched.
+    expect(t.A).toEqual({ borderTop: null, borderRight: null, borderBottom: null, borderLeft: null });
+    // Neighbours' other sides untouched.
+    expect(t.B.borderTop).toBe(null);
+    expect(t.D.borderLeft).toBe(null);
+  });
+
+  it('"all" with the default 0.5pt black spec normalizes to null (table default)', () => {
+    const t = run(grid3(), 'E', 'all', { widthPt: 0.5, color: '#000000' });
+    expect(t.E).toEqual({ borderTop: null, borderRight: null, borderBottom: null, borderLeft: null });
+  });
+
+  it('a null spec removes borders ("no border"), both sides of each boundary', () => {
+    const t = run(grid3(), 'E', 'all', null);
+    expect(t.E).toEqual({ borderTop: 'none', borderRight: 'none', borderBottom: 'none', borderLeft: 'none' });
+    expect(t.B.borderBottom).toBe('none');
+    expect(t.F.borderLeft).toBe('none');
+  });
+
+  it('"outer" on a 2×2 region sets only the region edges (+ outside mirrors)', () => {
+    const t = run(grid3(), ['A', 'E'], 'outer', RED); // region = A B / D E
+    expect(t.A.borderTop).toBe(V);
+    expect(t.A.borderLeft).toBe(V);
+    expect(t.B.borderTop).toBe(V);
+    expect(t.B.borderRight).toBe(V);
+    expect(t.E.borderRight).toBe(V);
+    expect(t.E.borderBottom).toBe(V);
+    // Inner boundaries untouched.
+    expect(t.A.borderRight).toBe(null);
+    expect(t.A.borderBottom).toBe(null);
+    expect(t.E.borderTop).toBe(null);
+    expect(t.E.borderLeft).toBe(null);
+    // Outside neighbours mirror the shared edge.
+    expect(t.C.borderLeft).toBe(V);
+    expect(t.F.borderLeft).toBe(V);
+    expect(t.G.borderTop).toBe(V);
+    expect(t.H.borderTop).toBe(V);
+    expect(t.I).toEqual({ borderTop: null, borderRight: null, borderBottom: null, borderLeft: null });
+  });
+
+  it('"inner" on a 2×2 region sets only the boundaries between region cells', () => {
+    const t = run(grid3(), ['A', 'E'], 'inner', RED);
+    expect(t.A.borderRight).toBe(V);
+    expect(t.B.borderLeft).toBe(V);
+    expect(t.A.borderBottom).toBe(V);
+    expect(t.D.borderTop).toBe(V);
+    expect(t.E.borderTop).toBe(V);
+    expect(t.E.borderLeft).toBe(V);
+    // Region edges untouched.
+    expect(t.A.borderTop).toBe(null);
+    expect(t.A.borderLeft).toBe(null);
+    expect(t.E.borderRight).toBe(null);
+    expect(t.E.borderBottom).toBe(null);
+    expect(t.C.borderLeft).toBe(null);
+  });
+
+  it('"top" sets only the region top edge', () => {
+    const t = run(grid3(), ['D', 'E'], 'top', RED); // region = D E (row 1)
+    expect(t.D.borderTop).toBe(V);
+    expect(t.E.borderTop).toBe(V);
+    expect(t.A.borderBottom).toBe(V); // mirror above
+    expect(t.B.borderBottom).toBe(V);
+    expect(t.D.borderBottom).toBe(null);
+    expect(t.D.borderLeft).toBe(null);
+    expect(t.F.borderTop).toBe(null);
+  });
+});
+
+describe('activeBorderPresets', () => {
+  function stateFor(json: N, target: string | [string, string]): EditorState {
+    const doc = schema.nodeFromJSON(json);
+    const selection = typeof target === 'string'
+      ? TextSelection.create(doc, textPos(doc, target))
+      : new CellSelection(doc.resolve(cellPos(doc, target[0])), doc.resolve(cellPos(doc, target[1])));
+    return EditorState.create({ schema, doc, selection });
+  }
+  const THIN = { widthPt: 0.5, color: '#000000' };
+
+  it('fresh table (default borders) + default pen → every preset active except none', () => {
+    const a = activeBorderPresets(stateFor(grid3(), ['A', 'I']), THIN)!;
+    expect(a.all && a.outer && a.inner && a.innerH && a.innerV && a.top && a.bottom && a.left && a.right).toBe(true);
+    expect(a.none).toBe(false);
+  });
+
+  it('active state follows the pen width: thicker pen → default borders no longer match', () => {
+    const a = activeBorderPresets(stateFor(grid3(), ['A', 'I']), { widthPt: 2.25, color: '#000000' })!;
+    expect(a.all).toBe(false);
+    expect(a.outer).toBe(false);
+    expect(a.none).toBe(false);
+  });
+
+  it('borderless region → only none active', () => {
+    // Remove all borders of the whole table first.
+    const st = stateFor(grid3(), ['A', 'I']);
+    let next: EditorState | null = null;
+    setTableBorders('all', null)({ state: st, tr: st.tr, dispatch: (tr: any) => { next = st.apply(tr); } } as any);
+    const a = activeBorderPresets(next!, THIN)!;
+    expect(a.none).toBe(true);
+    expect(a.all).toBe(false);
+    expect(a.top).toBe(false);
+  });
+
+  it('single cell: inner presets have no boundaries → inactive; edges active', () => {
+    const a = activeBorderPresets(stateFor(grid3(), 'E'), THIN)!;
+    expect(a.inner).toBe(false);
+    expect(a.innerH).toBe(false);
+    expect(a.all && a.outer && a.top && a.bottom && a.left && a.right).toBe(true);
+  });
+
+  it('a boundary with a mismatched color breaks the match for presets that cover it', () => {
+    const st = stateFor(grid3(), 'E');
+    let next: EditorState | null = null;
+    setTableBorders('top', { widthPt: 0.5, color: '#FF0000' })({ state: st, tr: st.tr, dispatch: (tr: any) => { next = st.apply(tr); } } as any);
+    const withSel = EditorState.create({ schema, doc: next!.doc, selection: TextSelection.create(next!.doc, textPos(next!.doc, 'E')) });
+    const a = activeBorderPresets(withSel, THIN)!;
+    expect(a.top).toBe(false);   // now red, pen is black
+    expect(a.all).toBe(false);
+    expect(a.bottom).toBe(true); // untouched sides still match
+    const red = activeBorderPresets(withSel, { widthPt: 0.5, color: '#FF0000' })!;
+    expect(red.top).toBe(true);
+  });
+
+  it('returns null outside a table', () => {
+    const doc = schema.nodeFromJSON({ type: 'doc', content: [{ type: 'paragraph', content: [{ type: 'text', text: 'x' }] }] });
+    const st = EditorState.create({ schema, doc, selection: TextSelection.create(doc, 1) });
+    expect(activeBorderPresets(st, THIN)).toBe(null);
+  });
+});
+
+describe('border attr helpers', () => {
+  it('borderAttrValue: default collapses to null, none to "none", custom to canonical', () => {
+    expect(borderAttrValue({ widthPt: 0.5, color: '#000000' })).toBe(null);
+    expect(borderAttrValue(null)).toBe('none');
+    expect(borderAttrValue({ widthPt: 2.25, color: '#ff0000' })).toBe('2.25pt solid #FF0000');
+  });
+
+  it('parseBorderAttr inverts borderAttrValue', () => {
+    expect(parseBorderAttr(null)).toBe(null);
+    expect(parseBorderAttr('none')).toBe('none');
+    expect(parseBorderAttr('2.25pt solid #FF0000')).toEqual({ widthPt: 2.25, color: '#FF0000' });
+  });
+
+  it('borderAttrFromOdf: absent/none → "none", the 0.5pt-black default → null (unit tolerance)', () => {
+    expect(borderAttrFromOdf(undefined)).toBe('none');
+    expect(borderAttrFromOdf('none')).toBe('none');
+    expect(borderAttrFromOdf('0.5pt solid #000000')).toBe(null);
+    expect(borderAttrFromOdf('0.018cm solid #000000')).toBe(null); // LibreOffice cm form
+    expect(borderAttrFromOdf('2.25pt solid #ff0000')).toBe('2.25pt solid #FF0000');
+    expect(borderAttrFromOdf('0.06pt double #808080')).toBe('0.06pt solid #808080'); // style coerced
+  });
+});