🐛 fix: apply Y minRange absolute floor only for zero spans

src/math/__tests__/math.test.ts

@@ -69,6 +69,21 @@ describe('computeRange', () => {
     const mid = (min + max) / 2
     expect(mid).toBeCloseTo(50, 1)
   })
+
+  it('uses absolute floor only for zero-span data', () => {
+    const { min, max } = computeRange(pts([10, 10]), 10)
+    expect(max - min).toBeCloseTo(0.4)
+  })
+
+  it('does not force absolute floor for tiny nonzero spans', () => {
+    // Forcing 0.4 for every tiny span over-pads micro volatility into a
+    // flat-looking chart. Keep relative domain + margin; grid guards (#19)
+    // prevent hangs when the step size is denormal.
+    const rawRange = 1e-8
+    const { min, max } = computeRange(pts([9, 9 + rawRange]), 9)
+    expect(max - min).toBeCloseTo(rawRange * (1 + 2 * 0.12), 12)
+    expect(max - min).toBeLessThan(0.4)
+  })
 })
 
 // -- detectMomentum --

src/math/range.ts

@@ -29,7 +29,14 @@ export function computeRange(
 
   const rawRange = targetMax - targetMin
   const marginFactor = exaggerate ? 0.01 : 0.12
-  const minRange = rawRange * (exaggerate ? 0.02 : 0.1) || (exaggerate ? 0.04 : 0.4)
+  // `rawRange * k || floor` skipped the absolute floor for any tiny nonzero
+  // span (JS || only falls through on 0/falsy), which produced denormal Y
+  // domains and could freeze the Y-grid loop. Apply the floor only when the
+  // span is zero / non-finite; keep relative min for real nonzero ranges.
+  const relativeMin = rawRange * (exaggerate ? 0.02 : 0.1)
+  const absoluteFloor = exaggerate ? 0.04 : 0.4
+  const minRange =
+    rawRange > 0 && Number.isFinite(rawRange) ? relativeMin : absoluteFloor
 
   if (rawRange < minRange) {
     const mid = (targetMin + targetMax) / 2

src/useLivelineEngine.ts

@@ -424,7 +424,10 @@ function computeCandleRange(
   if (!isFinite(min) || !isFinite(max)) return { min: 99, max: 101 }
   const range = max - min
   const margin = range * 0.12
-  const minRange = range * 0.1 || 0.4
+  // Same floor semantics as computeRange: do not use `||` (skips floor for
+  // tiny nonzero spans). Absolute floor only when span is zero / non-finite.
+  const relativeMin = range * 0.1
+  const minRange = range > 0 && Number.isFinite(range) ? relativeMin : 0.4
   if (range < minRange) {
     const mid = (min + max) / 2
     return { min: mid - minRange / 2, max: mid + minRange / 2 }