diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b17c61f..ae4e004 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -40,6 +40,7 @@ jobs:
         working-directory: packages/fri-forecaster
       - run: pip install -e '.[test]' -e './packages/fri-forecaster[dev]'
       - run: python -m pytest -q -rs
+      - run: node --test tests/test_tooltips.cjs
 
   # README promises that `build` and `assemble` round-trip to the tracked
   # bytes. Rebuild everything on a fresh checkout and fail if anything tracked
diff --git a/index.html b/index.html
index 81418a4..f04133b 100644
--- a/index.html
+++ b/index.html
@@ -115,9 +115,15 @@
   @media (max-width: 760px) { .rail-grid { grid-template-columns: minmax(0, 1fr); gap: 14px; } }
   .modal-grid { display: grid; grid-template-columns: 180px 1fr; gap: 12px; }
   @media (max-width: 560px) { .modal-grid { grid-template-columns: 1fr; gap: 4px; } }
+  .tippy-box[data-theme~="airo"] {
+    background: var(--panel); color: var(--ink); border: 1px solid var(--line);
+    border-radius: 8px; box-shadow: var(--shadow); font-family: inherit;
+    font-size: 12px; line-height: 1.5;
+  }
+  .tippy-box[data-theme~="airo"] > .tippy-content { padding: 8px 10px; }
+  .tippy-box[data-theme~="airo"] > .tippy-arrow { color: var(--panel); }
 </style>
 <link rel="stylesheet" href="https://unpkg.com/tippy.js@6.3.7/dist/tippy.css" />
-<link rel="stylesheet" href="https://unpkg.com/tippy.js@6.3.7/themes/light-border.css" />
 <!-- Visitor analytics (2026-09-11): who reaches the page, where from, which
      country. Plausible rather than GA because it sets no cookies and stores
      no personal data, so the page needs no consent banner and no privacy
@@ -192,6 +198,48 @@
 <script type="text/babel">
 const { useState, useMemo } = React;
 
+// One app-wide surface and placement policy for text, HTML and React tooltips.
+function appTooltip(target, options = {}) {
+  return window.tippy(target, {
+    theme: "airo", arrow: true, maxWidth: 360, offset: [0, 8],
+    placement: "right", appendTo: () => document.body, animation: false,
+    ...options,
+  });
+}
+
+// React owns content; Popper owns viewport-aware placement. Coordinates are SVG
+// user units, transformed through the actual screen matrix (including resize).
+function PointTooltip({ anchor, box, x, y, children }) {
+  const [content] = useState(() => document.createElement("div"));
+  const tooltip = React.useRef(null);
+  const position = React.useRef(null);
+  position.current = { anchor, box, x, y };
+  React.useLayoutEffect(() => {
+    const p = position.current;
+    const target = p.anchor || (p.box && p.box.current);
+    if (!target || !window.tippy) return;
+    const instance = appTooltip(target, {
+      content, trigger: "manual",
+      getReferenceClientRect: () => {
+        const p = position.current;
+        if (p.anchor) return p.anchor.getBoundingClientRect();
+        const svg = p.box.current.querySelector("svg");
+        const point = svg.createSVGPoint();
+        point.x = p.x; point.y = p.y;
+        const screen = point.matrixTransform(svg.getScreenCTM());
+        return { x: screen.x, y: screen.y, left: screen.x, right: screen.x,
+          top: screen.y, bottom: screen.y, width: 0, height: 0 };
+      },
+    });
+    tooltip.current = instance;
+    instance.show();
+    return () => { instance.destroy(); tooltip.current = null; };
+  }, [anchor, box, content]);
+  React.useLayoutEffect(() => {
+    if (tooltip.current && tooltip.current.popperInstance) tooltip.current.popperInstance.update();
+  });
+  return ReactDOM.createPortal(children, content);
+}
 /* ============================ mock data ============================ */
 function mulberry32(a) {
   return function () {
@@ -283,6 +331,7 @@
   const ymax = niceMax(Math.max(...allV, bandTop, 0.5) * 1.05);
   const y = v => pad.t + (1 - v / ymax) * (H - pad.t - pad.b);
   const yticks = Array.from({ length: 6 }, (_, i) => (ymax / 5) * i);
+  const box = React.useRef(null);
   const [hv, setHv] = useState(null);
 
   const linePath = pts => pts.map((p, k) => (k === 0 ? "M" : "L") + x(p.i).toFixed(1) + " " + y(p.v).toFixed(1)).join(" ");
@@ -295,7 +344,7 @@
   }
 
   return (
-    <div style={{ position: "relative" }}>
+    <div ref={box} style={{ position: "relative" }}>
       <svg viewBox={`0 0 ${W} ${H}`} style={{ width: "100%", height: "auto", display: "block" }} onMouseLeave={() => setHv(null)}>
         {yticks.map((t, i) => (
           <g key={i}>
@@ -335,9 +384,7 @@
         const rows = lines.map(l => ({ l, p: l.pts.find(p => p.i === hv) })).filter(r => r.p);
         if (!rows.length) return null;
         return (
-          <div style={{ position: "absolute", top: 6, left: `${(x(hv) / W) * 100}%`, transform: "translateX(8px)",
-            background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "8px 10px",
-            boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 150 }}>
+          <PointTooltip box={box} x={x(hv)} y={y(rows[0].p.v)}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 5 }}>{MONTHS[hv]}{SURVEY_IDX.includes(hv) ? " · survey" : ""}</div>
             {rows.map(({ l, p }) => (
               <div key={l.key} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12 }}>
@@ -345,7 +392,7 @@
                 <span className="mono" style={{ fontWeight: 500 }}>{p.v.toFixed(2)}%</span>
               </div>
             ))}
-          </div>
+          </PointTooltip>
         );
       })()}
     </div>
@@ -490,28 +537,6 @@
   })).filter(v => v.vals.some(val => val != null));
 };
 
-// React owns the content; Tippy owns placement relative to the actual SVG dot.
-function TimelinePointTooltip({ anchor, children }) {
-  const [content] = useState(() => document.createElement("div"));
-  const tooltip = React.useRef(null);
-  React.useEffect(() => {
-    if (!anchor || !window.tippy) return;
-    const instance = window.tippy(anchor, {
-      content, trigger: "manual", theme: "light-border", arrow: true,
-      maxWidth: 340, offset: [0, 8], placement: "top", appendTo: () => document.body,
-      animation: false,
-    });
-    tooltip.current = instance;
-    instance.show();
-    return () => { instance.destroy(); tooltip.current = null; };
-  }, [anchor, content]);
-  // Scale changes can move a pinned dot without changing its DOM element.
-  React.useLayoutEffect(() => {
-    if (tooltip.current && tooltip.current.popperInstance) tooltip.current.popperInstance.update();
-  });
-  return ReactDOM.createPortal(children, content);
-}
-
 /* ---------------- time-series chart ---------------- */
 // Before Oct 21 only the median is visible until hovered or selected; then
 // model answers appear as ink-gray circles. Since Oct 21 each prompt condition
@@ -718,7 +743,7 @@
       </svg>
 
       {hovered && (
-        <TimelinePointTooltip anchor={active.anchor}>
+        <PointTooltip anchor={active.anchor}>
           {hoveredModels.map(([label, val]) => (
             <div key={label} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12 }}>
               <span style={{ display: "flex", alignItems: "center", gap: 6 }}>
@@ -727,10 +752,10 @@
               <span className="mono">{fmtV(val)}</span>
             </div>
           ))}
-        </TimelinePointTooltip>
+        </PointTooltip>
       )}
       {hv != null && !hovered && (
-        <TimelinePointTooltip anchor={active.anchor}>
+        <PointTooltip anchor={active.anchor}>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>
             {snapshots[hv].date} · <span style={{ color: "var(--ink)", fontWeight: 600 }}>by {h}</span>
             {hasVar(hv) ? ` · ${variants.filter(v => v.vals[hv] != null).length} prompts per model · each model = mean of its prompts`
@@ -760,7 +785,7 @@
               </span>
             </div>
           ))}
-        </TimelinePointTooltip>
+        </PointTooltip>
       )}
     </div>
   );
@@ -1125,9 +1150,7 @@ <h2 style={{ fontSize: 22, marginTop: 0, marginBottom: 4 }}>{title}</h2>
         if ((q.ci || {})[hv]) rows.push({ label: "95% CI", color: "var(--ink-faint)", text: fmtV(q.ci[hv][0]) + "–" + fmtV(q.ci[hv][1]), ci: true });
         (q.human || []).forEach(hm => { if (hm.ps[hv] != null) rows.push({ label: hm.panel + " " + groupShort(hm.group), color: hm.color, v: hm.ps[hv], human: true }); });
         return (
-          <div style={{ position: "absolute", top: 6, left: `${(x(hv) / W) * 100}%`, transform: x(hv) > W * 0.6 ? "translateX(calc(-100% - 8px))" : "translateX(8px)",
-            background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "8px 10px",
-            boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 170, maxWidth: "calc(100% - 16px)" }}>
+          <PointTooltip box={box} x={x(hv)} y={y(q.median[hv] != null ? q.median[hv] : rows[0].v)}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 5 }}>by end of {hv}{loss ? " · deaths" : ""}</div>
             {rows.map(r => (
               <div key={r.label} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12, fontWeight: r.bold ? 600 : 400 }}>
@@ -1135,7 +1158,7 @@ <h2 style={{ fontSize: 22, marginTop: 0, marginBottom: 4 }}>{title}</h2>
                 <span className="mono" style={{ fontWeight: 500 }}>{r.text != null ? r.text : (r.censored === "upper" ? "<" : r.censored === "lower" ? ">" : "") + fmtV(r.v)}</span>
               </div>
             ))}
-          </div>
+          </PointTooltip>
         );
       })()}
     </div>
@@ -1454,10 +1477,7 @@ <h2 style={{ fontSize: 22, marginTop: 0 }}>
       {hist && (() => {
         const b = histBand(leg, hist);
         return (
-        <div style={{ position: "absolute", top: 8, left: `${(x(b.central) / W) * 100}%`,
-          transform: x(b.central) > W * 0.55 ? "translateX(calc(-100% - 10px))" : "translateX(10px)",
-          background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "9px 11px",
-          boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 210, maxWidth: "min(300px, calc(100% - 16px))" }}>
+        <PointTooltip box={box} x={x(b.central)} y={pad.t}>
           <div style={{ fontSize: 12, fontWeight: 600, marginBottom: 1 }}>{hist.label}</div>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>{hist.span} · {hist.basis}</div>
           <div style={{ fontSize: 12, marginBottom: 6 }}>
@@ -1474,14 +1494,11 @@ <h2 style={{ fontSize: 22, marginTop: 0 }}>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginTop: 6, paddingTop: 5, borderTop: "1px solid var(--line-soft)" }}>
             {hist.source}
           </div>
-        </div>
+        </PointTooltip>
         );
       })()}
       {hov && (
-        <div style={{ position: "absolute", top: 8, left: `${(x(hov.value) / W) * 100}%`,
-          transform: x(hov.value) > W * 0.55 ? "translateX(calc(-100% - 10px))" : "translateX(10px)",
-          background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "9px 11px",
-          boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 195, maxWidth: "min(265px, calc(100% - 16px))" }}>
+        <PointTooltip box={box} x={x(hov.value)} y={y(hov.median)}>
           <div style={{ fontSize: 12, fontWeight: 600, marginBottom: 1 }}>{hov.cause}</div>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>
             {hov.label} · <strong>{(G2.horizonLabels || {})[h] || "by " + h}</strong>
@@ -1505,7 +1522,7 @@ <h2 style={{ fontSize: 22, marginTop: 0 }}>
               ⚠ incoherent: {hov.bad.map(v => v.model).join(", ")} rate this above the weaker “{hov.bad[0].broaderLabel}” event.
             </div>
           )}
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
@@ -1815,8 +1832,7 @@ <h2 style={{ fontSize: 20, marginTop: 6, marginBottom: 4 }}>Coherence check</h2>
   React.useEffect(() => {
     if (!window.tippy || !ref.current) return;
     const nodes = ref.current.querySelectorAll("[data-tippy-content]");
-    const inst = window.tippy(nodes, { allowHTML: true, theme: "light-border", arrow: true,
-      maxWidth: 240, offset: [0, 8], placement: "top" });
+    const inst = appTooltip(nodes, { allowHTML: true });
     return () => inst.forEach(i => i.destroy());
   }, []);
   const box = React.useRef(null);
@@ -2042,8 +2058,7 @@ <h2 style={{ fontSize: 20, marginTop: 6, marginBottom: 4 }}>Coherence check</h2>
   React.useEffect(() => {
     if (!window.tippy || !ref.current) return;
     const nodes = ref.current.querySelectorAll("[data-tippy-content]");
-    const inst = window.tippy(nodes, { allowHTML: true, theme: "light-border", arrow: true,
-      maxWidth: 280, offset: [0, 8], placement: "top" });
+    const inst = appTooltip(nodes, { allowHTML: true });
     return () => inst.forEach(i => i.destroy());
   }, [points]);
   const box = React.useRef(null);
@@ -2430,10 +2445,7 @@ <h2 style={{ fontSize: 22, margin: "0 0 8px" }}>{title}</h2>
   const tooltip = React.useRef(null);
   React.useEffect(() => {
     if (!title || !window.tippy || !ref.current) return;
-    const instance = window.tippy(ref.current, {
-      content: title, allowHTML: false, theme: "light-border", arrow: true,
-      maxWidth: 360, offset: [0, 8], placement: "top",
-    });
+    const instance = appTooltip(ref.current, { content: title, allowHTML: false });
     tooltip.current = instance;
     return () => { instance.destroy(); tooltip.current = null; };
   }, [title]);
@@ -3138,17 +3150,16 @@ <h3 style={{ fontSize: 17, marginTop: 22, marginBottom: 8 }}>Intermediate (valid
         const b = rows.find(r => r.id === hv);
         const i = rows.indexOf(b);
         const cond = (C.conditions || []).find(c => c.id === b.id) || {};
-        const top = ((pad.t + rowH * (i + baseRow)) / H) * 100;
         const desc = cond.description || "";
         const cut = desc.length > 900 ? desc.slice(0, 900).replace(/\s+\S*$/, "") + " …" : desc;
         return (
-          <div style={{ position: "absolute", top: `${top}%`, right: 8, transform: "translateY(-100%)", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "10px 12px", boxShadow: "var(--shadow)", pointerEvents: "none", width: 460, maxWidth: narrow ? "calc(100% - 16px)" : "60%", zIndex: 5 }}>
+          <PointTooltip box={box} x={barVal(b) == null ? x0 : x(barVal(b))} y={barY(rowY(i))}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 3 }}>What the model was told{b.leapId ? <> · <span className="mono">{b.leapId}</span></> : null}</div>
             <div style={{ fontSize: 13.5, fontWeight: 600, marginBottom: 6 }}>{b.label}</div>
             {cond.assume && <div style={{ fontSize: 12.5, color: "var(--ink)", marginBottom: 6 }}><strong>Condition.</strong> {cond.assume}</div>}
             {cut && <div style={{ fontSize: 12, color: "var(--ink-soft)", whiteSpace: "pre-wrap", lineHeight: 1.45 }}>{cut}</div>}
             {desc.length > 900 && <div style={{ fontSize: 11, color: "var(--ink-faint)", marginTop: 6 }}>click the row for the full text</div>}
-          </div>
+          </PointTooltip>
         );
       })()}
       {loss && <ExpectedLossNote />}
@@ -3467,10 +3478,10 @@ <h2 style={{ fontSize: 22, marginTop: 0 }}>{q.heading || q.short} — by {hz}</h
         })}
       </svg>
       {hv && (
-        <div style={{ position: "absolute", left: Math.min(hv.x / W * 100, 65) + "%", top: Math.max(0, (hv.y / H) * 100 - 18) + "%", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "6px 9px", boxShadow: "var(--shadow)", pointerEvents: "none", fontSize: 12, zIndex: 5, whiteSpace: "nowrap" }}>
+        <PointTooltip box={box} x={hv.x} y={hv.y}>
           <div style={{ fontWeight: 600 }}>{hv.title}</div>
           {hv.lines.map(t => <div key={t} className="mono" style={{ color: "var(--ink-soft)" }}>{t}</div>)}
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
@@ -3804,13 +3815,13 @@ <h2 style={{ fontSize: 22, marginTop: 0, marginBottom: 4 }}>{q.heading || q.shor
         {trailing}
       </div>
       {hv && (
-        <div style={{ position: "absolute", left: Math.min(x(hv.x) / W * 100, 70) + "%", top: Math.max(0, (y(hv.p) / H) * 100 - 16) + "%", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "6px 9px", boxShadow: "var(--shadow)", pointerEvents: "none", fontSize: 12, zIndex: 5, whiteSpace: "nowrap" }}>
+        <PointTooltip box={box} x={x(hv.x)} y={y(hv.p)}>
           <div style={{ fontWeight: 600 }}>{hv.label}</div>
           <div className="mono" style={{ color: "var(--ink-soft)" }}>
             {hv.kind === "human" ? `unconditional ${axFmtY(kind, hv.p)} · their own median ${fx(hv.x)}`
               : `${fx(hv.x)} → ${axFmtY(kind, hv.p)}`}
           </div>
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
diff --git a/tests/test_tooltips.cjs b/tests/test_tooltips.cjs
new file mode 100644
index 0000000..27a455a
--- /dev/null
+++ b/tests/test_tooltips.cjs
@@ -0,0 +1,73 @@
+// Run: node --test tests/test_tooltips.cjs (no npm dependencies).
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const vm = require('node:vm');
+const fs = require('node:fs');
+const path = require('node:path');
+
+test('shared tooltip policy, SVG placement, updates and cleanup', () => {
+  let options, shown = 0, destroyed = 0, updated = 0;
+  const body = {};
+  const effects = [];
+  const refs = [];
+  let cursor = 0;
+  const context = vm.createContext({
+    window: { tippy(target, opts) {
+      options = opts;
+      return { show() { shown++; }, destroy() { destroyed++; },
+        popperInstance: { update() { updated++; } } };
+    } },
+    document: { body, createElement: () => ({}) },
+    useState: init => [init()],
+    React: {
+      useRef(value) { const i = cursor++; return refs[i] || (refs[i] = { current: value }); },
+      useLayoutEffect(effect) { effects.push(effect); },
+    },
+    ReactDOM: { createPortal: (children, content) => ({ children, content }) },
+  });
+  vm.runInContext(fs.readFileSync(path.join(__dirname, '../web/shared/tooltips.jsx'), 'utf8'), context);
+  context.appTooltip({}, { content: 'Legend' });
+  assert.equal(options.theme, 'airo');
+  assert.equal(options.placement, 'right');
+  assert.equal(options.appendTo(), body);
+  let scale = 0.5;
+  const svg = {
+    createSVGPoint: () => ({ x: 0, y: 0, matrixTransform(m) {
+      return { x: this.x * m.scale + 100, y: this.y * m.scale + 300 };
+    } }),
+    getScreenCTM: () => ({ scale }),
+  };
+  const box = { current: { querySelector: () => svg } };
+  const portal = context.PointTooltip({ box, x: 40, y: 80, children: 'Forecast' });
+  assert.equal(portal.children, 'Forecast');
+  const cleanup = effects[0]();
+  effects[1]();
+  assert.equal(shown, 1);
+  assert.equal(options.getReferenceClientRect().left, 120);
+  assert.equal(options.getReferenceClientRect().top, 340);
+  // Same chart, new dimensions and point: callback must read the latest values.
+  scale = 2;
+  cursor = 0;
+  context.PointTooltip({ box, x: 50, y: 100, children: 'Changed' });
+  effects[3]();
+  assert.equal(options.getReferenceClientRect().left, 200);
+  assert.equal(options.getReferenceClientRect().top, 500);
+  assert.equal(updated, 2);
+  cleanup();
+  assert.equal(destroyed, 1);
+  cursor = 0;
+  context.PointTooltip({ anchor: { getBoundingClientRect: () => ({ top: 900 }) } });
+  const cleanupPinned = effects[4]();
+  assert.equal(options.getReferenceClientRect().top, 900);
+  cleanupPinned();
+  assert.equal(destroyed, 2);
+});
+
+test('all app tooltip callers use the shared implementation', () => {
+  const demo = path.join(__dirname, '../web/demo');
+  for (const file of fs.readdirSync(demo).filter(name => name.endsWith('.jsx'))) {
+    const source = fs.readFileSync(path.join(demo, file), 'utf8');
+    assert.ok(!source.includes('window.tippy('), file);
+    assert.ok(!source.includes('position: "absolute"'), file);
+  }
+});
diff --git a/web/demo/00-head.html b/web/demo/00-head.html
index f5f000f..b0a2e9f 100644
--- a/web/demo/00-head.html
+++ b/web/demo/00-head.html
@@ -115,9 +115,15 @@
   @media (max-width: 760px) { .rail-grid { grid-template-columns: minmax(0, 1fr); gap: 14px; } }
   .modal-grid { display: grid; grid-template-columns: 180px 1fr; gap: 12px; }
   @media (max-width: 560px) { .modal-grid { grid-template-columns: 1fr; gap: 4px; } }
+  .tippy-box[data-theme~="airo"] {
+    background: var(--panel); color: var(--ink); border: 1px solid var(--line);
+    border-radius: 8px; box-shadow: var(--shadow); font-family: inherit;
+    font-size: 12px; line-height: 1.5;
+  }
+  .tippy-box[data-theme~="airo"] > .tippy-content { padding: 8px 10px; }
+  .tippy-box[data-theme~="airo"] > .tippy-arrow { color: var(--panel); }
 </style>
 <link rel="stylesheet" href="https://unpkg.com/tippy.js@6.3.7/dist/tippy.css" />
-<link rel="stylesheet" href="https://unpkg.com/tippy.js@6.3.7/themes/light-border.css" />
 <!-- Visitor analytics (2026-09-11): who reaches the page, where from, which
      country. Plausible rather than GA because it sets no cookies and stores
      no personal data, so the page needs no consent banner and no privacy
diff --git a/web/demo/10-mock-graph1.jsx b/web/demo/10-mock-graph1.jsx
index a5c183e..1de4713 100644
--- a/web/demo/10-mock-graph1.jsx
+++ b/web/demo/10-mock-graph1.jsx
@@ -89,6 +89,7 @@ function TimeSeriesChart({ panel, active }) {
   const ymax = niceMax(Math.max(...allV, bandTop, 0.5) * 1.05);
   const y = v => pad.t + (1 - v / ymax) * (H - pad.t - pad.b);
   const yticks = Array.from({ length: 6 }, (_, i) => (ymax / 5) * i);
+  const box = React.useRef(null);
   const [hv, setHv] = useState(null);
 
   const linePath = pts => pts.map((p, k) => (k === 0 ? "M" : "L") + x(p.i).toFixed(1) + " " + y(p.v).toFixed(1)).join(" ");
@@ -101,7 +102,7 @@ function TimeSeriesChart({ panel, active }) {
   }
 
   return (
-    <div style={{ position: "relative" }}>
+    <div ref={box} style={{ position: "relative" }}>
       <svg viewBox={`0 0 ${W} ${H}`} style={{ width: "100%", height: "auto", display: "block" }} onMouseLeave={() => setHv(null)}>
         {yticks.map((t, i) => (
           <g key={i}>
@@ -141,9 +142,7 @@ function TimeSeriesChart({ panel, active }) {
         const rows = lines.map(l => ({ l, p: l.pts.find(p => p.i === hv) })).filter(r => r.p);
         if (!rows.length) return null;
         return (
-          <div style={{ position: "absolute", top: 6, left: `${(x(hv) / W) * 100}%`, transform: "translateX(8px)",
-            background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "8px 10px",
-            boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 150 }}>
+          <PointTooltip box={box} x={x(hv)} y={y(rows[0].p.v)}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 5 }}>{MONTHS[hv]}{SURVEY_IDX.includes(hv) ? " · survey" : ""}</div>
             {rows.map(({ l, p }) => (
               <div key={l.key} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12 }}>
@@ -151,7 +150,7 @@ function TimeSeriesChart({ panel, active }) {
                 <span className="mono" style={{ fontWeight: 500 }}>{p.v.toFixed(2)}%</span>
               </div>
             ))}
-          </div>
+          </PointTooltip>
         );
       })()}
     </div>
diff --git a/web/demo/19-live-timeline.jsx b/web/demo/19-live-timeline.jsx
index 5fb2527..da797d8 100644
--- a/web/demo/19-live-timeline.jsx
+++ b/web/demo/19-live-timeline.jsx
@@ -49,28 +49,6 @@ const tlVariants = (q, horizon, snapshots) => {
   })).filter(v => v.vals.some(val => val != null));
 };
 
-// React owns the content; Tippy owns placement relative to the actual SVG dot.
-function TimelinePointTooltip({ anchor, children }) {
-  const [content] = useState(() => document.createElement("div"));
-  const tooltip = React.useRef(null);
-  React.useEffect(() => {
-    if (!anchor || !window.tippy) return;
-    const instance = window.tippy(anchor, {
-      content, trigger: "manual", theme: "light-border", arrow: true,
-      maxWidth: 340, offset: [0, 8], placement: "top", appendTo: () => document.body,
-      animation: false,
-    });
-    tooltip.current = instance;
-    instance.show();
-    return () => { instance.destroy(); tooltip.current = null; };
-  }, [anchor, content]);
-  // Scale changes can move a pinned dot without changing its DOM element.
-  React.useLayoutEffect(() => {
-    if (tooltip.current && tooltip.current.popperInstance) tooltip.current.popperInstance.update();
-  });
-  return ReactDOM.createPortal(children, content);
-}
-
 /* ---------------- time-series chart ---------------- */
 // Before Oct 21 only the median is visible until hovered or selected; then
 // model answers appear as ink-gray circles. Since Oct 21 each prompt condition
@@ -277,7 +255,7 @@ function TimelineChart({ q, snapshots, horizon, scale }) {
       </svg>
 
       {hovered && (
-        <TimelinePointTooltip anchor={active.anchor}>
+        <PointTooltip anchor={active.anchor}>
           {hoveredModels.map(([label, val]) => (
             <div key={label} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12 }}>
               <span style={{ display: "flex", alignItems: "center", gap: 6 }}>
@@ -286,10 +264,10 @@ function TimelineChart({ q, snapshots, horizon, scale }) {
               <span className="mono">{fmtV(val)}</span>
             </div>
           ))}
-        </TimelinePointTooltip>
+        </PointTooltip>
       )}
       {hv != null && !hovered && (
-        <TimelinePointTooltip anchor={active.anchor}>
+        <PointTooltip anchor={active.anchor}>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>
             {snapshots[hv].date} · <span style={{ color: "var(--ink)", fontWeight: 600 }}>by {h}</span>
             {hasVar(hv) ? ` · ${variants.filter(v => v.vals[hv] != null).length} prompts per model · each model = mean of its prompts`
@@ -319,7 +297,7 @@ function TimelineChart({ q, snapshots, horizon, scale }) {
               </span>
             </div>
           ))}
-        </TimelinePointTooltip>
+        </PointTooltip>
       )}
     </div>
   );
diff --git a/web/demo/20-live-graph1.jsx b/web/demo/20-live-graph1.jsx
index 90b2303..24080ea 100644
--- a/web/demo/20-live-graph1.jsx
+++ b/web/demo/20-live-graph1.jsx
@@ -186,9 +186,7 @@ function HorizonChart({ q, models, scale }) {
         if ((q.ci || {})[hv]) rows.push({ label: "95% CI", color: "var(--ink-faint)", text: fmtV(q.ci[hv][0]) + "–" + fmtV(q.ci[hv][1]), ci: true });
         (q.human || []).forEach(hm => { if (hm.ps[hv] != null) rows.push({ label: hm.panel + " " + groupShort(hm.group), color: hm.color, v: hm.ps[hv], human: true }); });
         return (
-          <div style={{ position: "absolute", top: 6, left: `${(x(hv) / W) * 100}%`, transform: x(hv) > W * 0.6 ? "translateX(calc(-100% - 8px))" : "translateX(8px)",
-            background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "8px 10px",
-            boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 170, maxWidth: "calc(100% - 16px)" }}>
+          <PointTooltip box={box} x={x(hv)} y={y(q.median[hv] != null ? q.median[hv] : rows[0].v)}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 5 }}>by end of {hv}{loss ? " · deaths" : ""}</div>
             {rows.map(r => (
               <div key={r.label} style={{ display: "flex", justifyContent: "space-between", gap: 14, fontSize: 12, fontWeight: r.bold ? 600 : 400 }}>
@@ -196,7 +194,7 @@ function HorizonChart({ q, models, scale }) {
                 <span className="mono" style={{ fontWeight: 500 }}>{r.text != null ? r.text : (r.censored === "upper" ? "<" : r.censored === "lower" ? ">" : "") + fmtV(r.v)}</span>
               </div>
             ))}
-          </div>
+          </PointTooltip>
         );
       })()}
     </div>
diff --git a/web/demo/30-live-graph2.jsx b/web/demo/30-live-graph2.jsx
index 294a056..6b8b860 100644
--- a/web/demo/30-live-graph2.jsx
+++ b/web/demo/30-live-graph2.jsx
@@ -195,10 +195,7 @@ function SeverityChart({ leg, d, h, showModels, scale }) {
       {hist && (() => {
         const b = histBand(leg, hist);
         return (
-        <div style={{ position: "absolute", top: 8, left: `${(x(b.central) / W) * 100}%`,
-          transform: x(b.central) > W * 0.55 ? "translateX(calc(-100% - 10px))" : "translateX(10px)",
-          background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "9px 11px",
-          boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 210, maxWidth: "min(300px, calc(100% - 16px))" }}>
+        <PointTooltip box={box} x={x(b.central)} y={pad.t}>
           <div style={{ fontSize: 12, fontWeight: 600, marginBottom: 1 }}>{hist.label}</div>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>{hist.span} · {hist.basis}</div>
           <div style={{ fontSize: 12, marginBottom: 6 }}>
@@ -215,14 +212,11 @@ function SeverityChart({ leg, d, h, showModels, scale }) {
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginTop: 6, paddingTop: 5, borderTop: "1px solid var(--line-soft)" }}>
             {hist.source}
           </div>
-        </div>
+        </PointTooltip>
         );
       })()}
       {hov && (
-        <div style={{ position: "absolute", top: 8, left: `${(x(hov.value) / W) * 100}%`,
-          transform: x(hov.value) > W * 0.55 ? "translateX(calc(-100% - 10px))" : "translateX(10px)",
-          background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "9px 11px",
-          boxShadow: "var(--shadow)", pointerEvents: "none", minWidth: 195, maxWidth: "min(265px, calc(100% - 16px))" }}>
+        <PointTooltip box={box} x={x(hov.value)} y={y(hov.median)}>
           <div style={{ fontSize: 12, fontWeight: 600, marginBottom: 1 }}>{hov.cause}</div>
           <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 6 }}>
             {hov.label} · <strong>{(G2.horizonLabels || {})[h] || "by " + h}</strong>
@@ -246,7 +240,7 @@ function SeverityChart({ leg, d, h, showModels, scale }) {
               ⚠ incoherent: {hov.bad.map(v => v.model).join(", ")} rate this above the weaker “{hov.bad[0].broaderLabel}” event.
             </div>
           )}
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
diff --git a/web/demo/40-graph3-graph4-charts.jsx b/web/demo/40-graph3-graph4-charts.jsx
index 986bc75..e7b7de3 100644
--- a/web/demo/40-graph3-graph4-charts.jsx
+++ b/web/demo/40-graph3-graph4-charts.jsx
@@ -88,8 +88,7 @@ function ECIScatter({ points }) {
   React.useEffect(() => {
     if (!window.tippy || !ref.current) return;
     const nodes = ref.current.querySelectorAll("[data-tippy-content]");
-    const inst = window.tippy(nodes, { allowHTML: true, theme: "light-border", arrow: true,
-      maxWidth: 240, offset: [0, 8], placement: "top" });
+    const inst = appTooltip(nodes, { allowHTML: true });
     return () => inst.forEach(i => i.destroy());
   }, []);
   const box = React.useRef(null);
diff --git a/web/demo/45-conditional-benches.jsx b/web/demo/45-conditional-benches.jsx
index b4876d6..99da11f 100644
--- a/web/demo/45-conditional-benches.jsx
+++ b/web/demo/45-conditional-benches.jsx
@@ -46,8 +46,7 @@ function BenchScatter({ points, yKey, yDomain, yTicks, yLabel, yFmt, band, refs,
   React.useEffect(() => {
     if (!window.tippy || !ref.current) return;
     const nodes = ref.current.querySelectorAll("[data-tippy-content]");
-    const inst = window.tippy(nodes, { allowHTML: true, theme: "light-border", arrow: true,
-      maxWidth: 280, offset: [0, 8], placement: "top" });
+    const inst = appTooltip(nodes, { allowHTML: true });
     return () => inst.forEach(i => i.destroy());
   }, [points]);
   const box = React.useRef(null);
diff --git a/web/demo/60-atoms.jsx b/web/demo/60-atoms.jsx
index b8e0a55..9d1edbb 100644
--- a/web/demo/60-atoms.jsx
+++ b/web/demo/60-atoms.jsx
@@ -28,10 +28,7 @@ function LegendDot({ color, label, hollow, onClick, dim, title }) {
   const tooltip = React.useRef(null);
   React.useEffect(() => {
     if (!title || !window.tippy || !ref.current) return;
-    const instance = window.tippy(ref.current, {
-      content: title, allowHTML: false, theme: "light-border", arrow: true,
-      maxWidth: 360, offset: [0, 8], placement: "top",
-    });
+    const instance = appTooltip(ref.current, { content: title, allowHTML: false });
     tooltip.current = instance;
     return () => { instance.destroy(); tooltip.current = null; };
   }, [title]);
diff --git a/web/demo/75-conditional.jsx b/web/demo/75-conditional.jsx
index 3c85174..57751b5 100644
--- a/web/demo/75-conditional.jsx
+++ b/web/demo/75-conditional.jsx
@@ -235,17 +235,16 @@ function CondDeltaChart({ cell, onPick, picked, axisValues, ctx }) {
         const b = rows.find(r => r.id === hv);
         const i = rows.indexOf(b);
         const cond = (C.conditions || []).find(c => c.id === b.id) || {};
-        const top = ((pad.t + rowH * (i + baseRow)) / H) * 100;
         const desc = cond.description || "";
         const cut = desc.length > 900 ? desc.slice(0, 900).replace(/\s+\S*$/, "") + " …" : desc;
         return (
-          <div style={{ position: "absolute", top: `${top}%`, right: 8, transform: "translateY(-100%)", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "10px 12px", boxShadow: "var(--shadow)", pointerEvents: "none", width: 460, maxWidth: narrow ? "calc(100% - 16px)" : "60%", zIndex: 5 }}>
+          <PointTooltip box={box} x={barVal(b) == null ? x0 : x(barVal(b))} y={barY(rowY(i))}>
             <div style={{ fontSize: 11, color: "var(--ink-faint)", marginBottom: 3 }}>What the model was told{b.leapId ? <> · <span className="mono">{b.leapId}</span></> : null}</div>
             <div style={{ fontSize: 13.5, fontWeight: 600, marginBottom: 6 }}>{b.label}</div>
             {cond.assume && <div style={{ fontSize: 12.5, color: "var(--ink)", marginBottom: 6 }}><strong>Condition.</strong> {cond.assume}</div>}
             {cut && <div style={{ fontSize: 12, color: "var(--ink-soft)", whiteSpace: "pre-wrap", lineHeight: 1.45 }}>{cut}</div>}
             {desc.length > 900 && <div style={{ fontSize: 11, color: "var(--ink-faint)", marginTop: 6 }}>click the row for the full text</div>}
-          </div>
+          </PointTooltip>
         );
       })()}
       {loss && <ExpectedLossNote />}
diff --git a/web/demo/77-capability.jsx b/web/demo/77-capability.jsx
index dfa5e79..56b0afb 100644
--- a/web/demo/77-capability.jsx
+++ b/web/demo/77-capability.jsx
@@ -162,10 +162,10 @@ function EciTrendChart({ eci, variants, active, onPick }) {
         })}
       </svg>
       {hv && (
-        <div style={{ position: "absolute", left: Math.min(hv.x / W * 100, 65) + "%", top: Math.max(0, (hv.y / H) * 100 - 18) + "%", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "6px 9px", boxShadow: "var(--shadow)", pointerEvents: "none", fontSize: 12, zIndex: 5, whiteSpace: "nowrap" }}>
+        <PointTooltip box={box} x={hv.x} y={hv.y}>
           <div style={{ fontWeight: 600 }}>{hv.title}</div>
           {hv.lines.map(t => <div key={t} className="mono" style={{ color: "var(--ink-soft)" }}>{t}</div>)}
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
diff --git a/web/demo/78-axes.jsx b/web/demo/78-axes.jsx
index c941dcd..93a30b8 100644
--- a/web/demo/78-axes.jsx
+++ b/web/demo/78-axes.jsx
@@ -231,13 +231,13 @@ function AxisScatter({ axis, q, hz, models, yDomain, trailing }) {
         {trailing}
       </div>
       {hv && (
-        <div style={{ position: "absolute", left: Math.min(x(hv.x) / W * 100, 70) + "%", top: Math.max(0, (y(hv.p) / H) * 100 - 16) + "%", background: "var(--panel)", border: "1px solid var(--line)", borderRadius: 8, padding: "6px 9px", boxShadow: "var(--shadow)", pointerEvents: "none", fontSize: 12, zIndex: 5, whiteSpace: "nowrap" }}>
+        <PointTooltip box={box} x={x(hv.x)} y={y(hv.p)}>
           <div style={{ fontWeight: 600 }}>{hv.label}</div>
           <div className="mono" style={{ color: "var(--ink-soft)" }}>
             {hv.kind === "human" ? `unconditional ${axFmtY(kind, hv.p)} · their own median ${fx(hv.x)}`
               : `${fx(hv.x)} → ${axFmtY(kind, hv.p)}`}
           </div>
-        </div>
+        </PointTooltip>
       )}
     </div>
   );
diff --git a/web/demo/manifest.json b/web/demo/manifest.json
index bc0742f..5d10443 100644
--- a/web/demo/manifest.json
+++ b/web/demo/manifest.json
@@ -18,6 +18,7 @@
   "chunks": [
     "00-head.html",
     "01-shell-open.html",
+    "../shared/tooltips.jsx",
     "10-mock-graph1.jsx",
     "15-graph3-graph4-mock.jsx",
     "19-live-timeline.jsx",
diff --git a/web/shared/tooltips.jsx b/web/shared/tooltips.jsx
new file mode 100644
index 0000000..7c56c75
--- /dev/null
+++ b/web/shared/tooltips.jsx
@@ -0,0 +1,42 @@
+// One app-wide surface and placement policy for text, HTML and React tooltips.
+function appTooltip(target, options = {}) {
+  return window.tippy(target, {
+    theme: "airo", arrow: true, maxWidth: 360, offset: [0, 8],
+    placement: "right", appendTo: () => document.body, animation: false,
+    ...options,
+  });
+}
+
+// React owns content; Popper owns viewport-aware placement. Coordinates are SVG
+// user units, transformed through the actual screen matrix (including resize).
+function PointTooltip({ anchor, box, x, y, children }) {
+  const [content] = useState(() => document.createElement("div"));
+  const tooltip = React.useRef(null);
+  const position = React.useRef(null);
+  position.current = { anchor, box, x, y };
+  React.useLayoutEffect(() => {
+    const p = position.current;
+    const target = p.anchor || (p.box && p.box.current);
+    if (!target || !window.tippy) return;
+    const instance = appTooltip(target, {
+      content, trigger: "manual",
+      getReferenceClientRect: () => {
+        const p = position.current;
+        if (p.anchor) return p.anchor.getBoundingClientRect();
+        const svg = p.box.current.querySelector("svg");
+        const point = svg.createSVGPoint();
+        point.x = p.x; point.y = p.y;
+        const screen = point.matrixTransform(svg.getScreenCTM());
+        return { x: screen.x, y: screen.y, left: screen.x, right: screen.x,
+          top: screen.y, bottom: screen.y, width: 0, height: 0 };
+      },
+    });
+    tooltip.current = instance;
+    instance.show();
+    return () => { instance.destroy(); tooltip.current = null; };
+  }, [anchor, box, content]);
+  React.useLayoutEffect(() => {
+    if (tooltip.current && tooltip.current.popperInstance) tooltip.current.popperInstance.update();
+  });
+  return ReactDOM.createPortal(children, content);
+}