diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index cf008824..27bc9d0b 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -231,6 +231,7 @@ jobs:
           CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-nav-more-floor-1139-e2e.js 2>&1 | tee -a e2e-output.txt
           BASE_URL=http://localhost:13581 node test-channel-fluid-e2e.js 2>&1 | tee -a e2e-output.txt
           BASE_URL=http://localhost:13581 node test-table-fluid-e2e.js 2>&1 | tee -a e2e-output.txt
+          BASE_URL=http://localhost:13581 node test-charts-fluid-1058-e2e.js 2>&1 | tee -a e2e-output.txt
           BASE_URL=http://localhost:13581 node test-slideover-1056-e2e.js 2>&1 | tee -a e2e-output.txt
           BASE_URL=http://localhost:13581 node test-slideover-1168-munger-e2e.js 2>&1 | tee -a e2e-output.txt
           BASE_URL=http://localhost:13581 node test-issue-1122-packets-filter-ux-e2e.js 2>&1 | tee -a e2e-output.txt
diff --git a/public/style.css b/public/style.css
index 8664aa61..952f14a1 100644
--- a/public/style.css
+++ b/public/style.css
@@ -2013,8 +2013,19 @@ button.ch-item.ch-item-encrypted .ch-badge { filter: grayscale(0.6); }
 .stat-label { font-size: 12px; color: var(--text-muted); margin-top: 2px; }
 .stat-detail { font-size: 11px; color: var(--text-muted); margin-top: 2px; }
 .stat-spark { margin-top: 6px; display: flex; justify-content: center; }
-.analytics-row { display: flex; gap: 16px; margin-bottom: 16px; }
-.analytics-row .flex-1 { flex: 1; min-width: 0; }
+/* #1058 — Analytics rows: fluid + auto-stacking via CSS Grid `auto-fit`.
+   Cards stack automatically when the row can't fit two columns at the
+   400px-floor minimum (avoids cramped charts), and otherwise lay out
+   side-by-side. Replaces the prior `flex` + `@media (max-width:640px)`
+   approach so behavior is driven by available width — not viewport —
+   matching #1050's fluid-everywhere mandate. `min(100%, 400px)` keeps
+   the track from overflowing at very narrow widths. */
+.analytics-row {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(min(100%, 400px), 1fr));
+  gap: 16px;
+  margin-bottom: 16px;
+}
 .rf-stats { display: flex; gap: 16px; flex-wrap: wrap; padding-top: 8px; font-size: 13px; }
 .payload-bars { display: flex; flex-direction: column; gap: 6px; }
 .payload-bar-row { display: flex; align-items: center; gap: 8px; }
@@ -2031,7 +2042,6 @@ button.ch-item.ch-item-encrypted .ch-badge { filter: grayscale(0.6); }
 .reach-nodes { flex: 1; font-size: 12px; line-height: 1.6; }
 .reach-count { min-width: 70px; text-align: right; font-size: 12px; color: var(--text-muted); }
 @media (max-width: 640px) {
-  .analytics-row { flex-direction: column; }
   .stats-grid { grid-template-columns: repeat(2, 1fr); }
   .repeater-name { min-width: 80px; }
   .reach-ring { flex-wrap: wrap; }
diff --git a/test-charts-fluid-1058-e2e.js b/test-charts-fluid-1058-e2e.js
new file mode 100644
index 00000000..1024f27c
--- /dev/null
+++ b/test-charts-fluid-1058-e2e.js
@@ -0,0 +1,230 @@
+/**
+ * E2E (#1058): Analytics chart containers — fluid + auto-stacking.
+ *
+ * Acceptance criteria:
+ *   - Chart containers fill their parent's available width (no fixed
+ *     px width on a chart container).
+ *   - Side-by-side cards inside `.analytics-row` stack vertically when
+ *     the container becomes too narrow.
+ *   - Wide viewports keep cards side-by-side (consecutive cards share
+ *     `getBoundingClientRect().top`).
+ *   - Re-layout works on viewport resize (no manual handler needed —
+ *     CSS does the work; test resizes 1920 → 800 and asserts re-flow).
+ *
+ * Boundary math (PR #1175 review follow-up):
+ *   The grid template is `repeat(auto-fit, minmax(min(100%, 400px), 1fr))`
+ *   with `gap: 16px`. Two columns first fit when the row's CONTENT width
+ *   is ≥ (2 × 400) + 16 = 816px.
+ *
+ *   `.analytics-page` has `padding: 16px 24px` → 48px horizontal padding,
+ *   so the row content width ≈ viewport - 48 (ignoring scrollbar, which
+ *   adds a few px in headless Chromium but doesn't shift conclusions
+ *   below).
+ *
+ *   Boundary viewports tested:
+ *     - 859px: content ≈ 811px  → < 816 → MUST stack (1 col)
+ *     - 870px: content ≈ 822px  → ≥ 816 → MUST be side-by-side (2 col)
+ *     - 950px: content ≈ 902px  → clearly ≥ 816 → side-by-side
+ *
+ *   The previous 2560 viewport case was tautological: `.analytics-page`
+ *   is capped at `max-width: 1600px`, so the row is never wider than
+ *   1600 - 48 = 1552 regardless of viewport. The cap is asserted
+ *   directly below to document WHY (see "max-width cap" step).
+ *
+ * Tested viewports: 768 / 859 / 870 / 950 / 1080 / 1440 / 1920.
+ *
+ * Selector contract:
+ *   - `.analytics-row` containers hold the side-by-side chart cards.
+ *   - Each chart card matched with `.analytics-row > .analytics-card.flex-1`.
+ *   - This avoids virtual-scroll-spacer / utility wrappers.
+ *
+ * Usage: BASE_URL=http://localhost:13581 node test-charts-fluid-1058-e2e.js
+ */
+'use strict';
+const { chromium } = require('playwright');
+
+const BASE = process.env.BASE_URL || 'http://localhost:13581';
+
+let passed = 0, failed = 0;
+async function step(name, fn) {
+  try { await fn(); passed++; console.log('  ✓ ' + name); }
+  catch (e) { failed++; console.error('  ✗ ' + name + ': ' + e.message); }
+}
+function assert(c, m) { if (!c) throw new Error(m || 'assertion failed'); }
+
+// Pairs of side-by-side chart cards exist on the Overview tab
+// (default landing tab). Use that for cross-viewport coverage.
+const HASH = '#/analytics';
+
+const VIEWPORTS = [
+  { w: 768,  h: 900, expectStacked: true  },
+  // Boundary: just below the 2-col threshold (~816px content needed).
+  { w: 859,  h: 900, expectStacked: true  },
+  // Boundary: just above the 2-col threshold.
+  { w: 870,  h: 900, expectStacked: false },
+  // Comfortably above the threshold.
+  { w: 950,  h: 900, expectStacked: false },
+  { w: 1080, h: 900, expectStacked: false },
+  { w: 1440, h: 900, expectStacked: false },
+  { w: 1920, h: 900, expectStacked: false },
+];
+
+async function gatherRows(page) {
+  return page.evaluate(() => {
+    const rows = Array.from(document.querySelectorAll('.analytics-row'));
+    return rows.map((row, idx) => {
+      const cards = Array.from(row.querySelectorAll(':scope > .analytics-card.flex-1'));
+      const rect = row.getBoundingClientRect();
+      return {
+        idx,
+        rowWidth: row.clientWidth,
+        rowRect: { left: rect.left, top: rect.top, width: rect.width },
+        cardCount: cards.length,
+        cards: cards.map(c => {
+          const r = c.getBoundingClientRect();
+          return { width: c.clientWidth, top: Math.round(r.top), left: Math.round(r.left) };
+        }),
+      };
+    }).filter(r => r.cardCount >= 2); // only multi-card rows are interesting
+  });
+}
+
+(async () => {
+  const browser = await chromium.launch({
+    headless: true,
+    executablePath: process.env.CHROMIUM_PATH || undefined,
+    args: ['--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage'],
+  });
+
+  console.log(`\n=== #1058 fluid analytics charts E2E against ${BASE} ===`);
+
+  for (const vp of VIEWPORTS) {
+    const ctx = await browser.newContext({ viewport: { width: vp.w, height: vp.h } });
+    const page = await ctx.newPage();
+    page.setDefaultTimeout(10000);
+    page.on('pageerror', (e) => console.error('[pageerror]', e.message));
+
+    const tag = `analytics@${vp.w}`;
+
+    await step(`${tag}: page renders + analytics-row containers found`, async () => {
+      await page.goto(BASE + '/' + HASH, { waitUntil: 'domcontentloaded' });
+      await page.waitForSelector('.analytics-row', { timeout: 10000 });
+      // Wait for at least one multi-card row to materialize (data fetch)
+      await page.waitForFunction(() => {
+        const rows = document.querySelectorAll('.analytics-row');
+        for (const r of rows) {
+          if (r.querySelectorAll(':scope > .analytics-card.flex-1').length >= 2) return true;
+        }
+        return false;
+      }, { timeout: 10000 });
+      await page.waitForTimeout(300);
+    });
+
+    await step(`${tag}: chart cards fill row width (no fixed px constraint)`, async () => {
+      const rows = await gatherRows(page);
+      assert(rows.length >= 1, `expected ≥1 multi-card row, got ${rows.length}`);
+      // Each card should be sized by the grid/flex track — sum of card
+      // widths plus gaps should be ≈ rowWidth (within tolerance).
+      for (const r of rows) {
+        const total = r.cards.reduce((s, c) => s + c.width, 0);
+        // When stacked: each card.width ≈ rowWidth. When side-by-side:
+        // total + gaps ≈ rowWidth. Either way, no card should exceed
+        // rowWidth + 2px.
+        for (const c of r.cards) {
+          assert(c.width <= r.rowWidth + 2,
+            `card width ${c.width} > rowWidth ${r.rowWidth} (row #${r.idx}) — chart not fluid`);
+        }
+        // And no card should be <50% of rowWidth/cardCount (proxy for
+        // "didn't lay out at all" — guards against zero-width stacking
+        // bugs).
+        for (const c of r.cards) {
+          assert(c.width > 0, `card has zero width (row #${r.idx})`);
+        }
+      }
+    });
+
+    await step(`${tag}: layout matches expected mode (stacked vs side-by-side)`, async () => {
+      const rows = await gatherRows(page);
+      assert(rows.length >= 1, 'no rows');
+      // Look at the first multi-card row.
+      const r = rows[0];
+      const tops = r.cards.map(c => c.top);
+      const allSameTop = tops.every(t => Math.abs(t - tops[0]) <= 2);
+      if (vp.expectStacked) {
+        assert(!allSameTop,
+          `expected cards to STACK at ${vp.w}px but all share top=${tops[0]} (tops=${JSON.stringify(tops)})`);
+      } else {
+        assert(allSameTop,
+          `expected cards SIDE-BY-SIDE at ${vp.w}px but tops differ: ${JSON.stringify(tops)}`);
+      }
+    });
+
+    await ctx.close();
+  }
+
+  // Re-layout on resize: start wide, then resize narrow, observe re-flow.
+  await step('resize 1920 → 800 re-flows charts', async () => {
+    const ctx = await browser.newContext({ viewport: { width: 1920, height: 900 } });
+    const page = await ctx.newPage();
+    page.setDefaultTimeout(10000);
+    await page.goto(BASE + '/' + HASH, { waitUntil: 'domcontentloaded' });
+    await page.waitForSelector('.analytics-row', { timeout: 10000 });
+    await page.waitForFunction(() => {
+      const rows = document.querySelectorAll('.analytics-row');
+      for (const r of rows) {
+        if (r.querySelectorAll(':scope > .analytics-card.flex-1').length >= 2) return true;
+      }
+      return false;
+    }, { timeout: 10000 });
+    await page.waitForTimeout(300);
+
+    const wideRows = await gatherRows(page);
+    assert(wideRows.length >= 1, 'no rows at 1920');
+    const wideTops = wideRows[0].cards.map(c => c.top);
+    const wideSame = wideTops.every(t => Math.abs(t - wideTops[0]) <= 2);
+    assert(wideSame, `expected side-by-side at 1920 (tops=${JSON.stringify(wideTops)})`);
+
+    await page.setViewportSize({ width: 800, height: 800 });
+    await page.waitForTimeout(400);
+
+    const narrowRows = await gatherRows(page);
+    const narrowTops = narrowRows[0].cards.map(c => c.top);
+    const narrowSame = narrowTops.every(t => Math.abs(t - narrowTops[0]) <= 2);
+    assert(!narrowSame,
+      `expected re-flow / stacked layout after resize to 800 (tops=${JSON.stringify(narrowTops)})`);
+    await ctx.close();
+  });
+
+  // Max-width cap on .analytics-page documents WHY the previous 2560
+  // viewport case was tautological. The cap exists to keep chart
+  // density readable on ultrawide displays — without it, fluid
+  // grid would spread cards across 2560+px, hurting scannability.
+  // Replaces the dropped 2560 case with a direct assertion of the
+  // architectural contract that made it tautological.
+  // Follow-up: cap-vs-fluid tension is tracked separately; this
+  // test pins the current contract so a regression is caught.
+  await step('analytics-page max-width: 1600px cap is enforced', async () => {
+    const ctx = await browser.newContext({ viewport: { width: 2560, height: 1200 } });
+    const page = await ctx.newPage();
+    page.setDefaultTimeout(10000);
+    await page.goto(BASE + '/' + HASH, { waitUntil: 'domcontentloaded' });
+    await page.waitForSelector('.analytics-page', { timeout: 10000 });
+    const pageWidth = await page.evaluate(() => {
+      const el = document.querySelector('.analytics-page');
+      return el ? el.getBoundingClientRect().width : null;
+    });
+    assert(pageWidth !== null, '.analytics-page not found');
+    assert(pageWidth <= 1600 + 1,
+      `.analytics-page width ${pageWidth} exceeds 1600px cap at 2560 viewport`);
+    // And the cap must actually be ACTIVE at 2560 (i.e. capped, not
+    // viewport-limited). At 2560 viewport, page width should be at
+    // the cap, not the viewport.
+    assert(pageWidth >= 1500,
+      `.analytics-page width ${pageWidth} suspiciously below cap — selector or styles changed?`);
+    await ctx.close();
+  });
+
+  await browser.close();
+  console.log(`\n=== #1058 fluid analytics charts E2E: ${passed} passed, ${failed} failed ===`);
+  process.exit(failed ? 1 : 0);
+})();