diff --git a/frontend/components/dataset/DatasetCard.tsx b/frontend/components/dataset/DatasetCard.tsx
index 2d362ae..5b4c700 100644
--- a/frontend/components/dataset/DatasetCard.tsx
+++ b/frontend/components/dataset/DatasetCard.tsx
@@ -9,7 +9,12 @@ export interface DatasetCardData {
   status: DatasetStatus;
   cadence: string;
   columns: { name: string; type: string }[];
+  // Preview is capped at 5 rows for the mini-table. The total row count
+  // is on `rowCount` (denormalized counter maintained by the row write
+  // mutations in convex/datasetRows.ts) so the footer stays reactive
+  // past the first 5 inserts.
   previewRows: Record<string, unknown>[];
+  rowCount: number;
   visibility?: "public" | "private";
 }
 
@@ -49,7 +54,7 @@ export function DatasetCard({ dataset }: { dataset: DatasetCardData }) {
               <span className="text-[11px] text-muted">{dataset.cadence}</span>
             </div>
             <span className="text-[11px] text-muted">
-              {dataset.previewRows?.length ?? 0} rows
+              {dataset.rowCount ?? 0} rows
             </span>
           </div>
         </div>
diff --git a/frontend/convex/datasetRows.ts b/frontend/convex/datasetRows.ts
index 99eadb0..fd7f16d 100644
--- a/frontend/convex/datasetRows.ts
+++ b/frontend/convex/datasetRows.ts
@@ -1,8 +1,28 @@
 import { query, internalMutation, internalQuery } from "./_generated/server.js";
+import type { MutationCtx } from "./_generated/server.js";
 import { v } from "convex/values";
+import type { Id } from "./_generated/dataModel.js";
 import { assertRowInDataset, loadReadableDataset } from "./lib/authz.js";
 import { consumeQuotaForDataset } from "./lib/quota.js";
 
+/**
+ * Authoritative row count for a dataset. O(N), so use only on the slow
+ * paths: self-heal in `insert` / `remove` when the dataset doc predates
+ * the `rowCount` field, or the explicit `datasets.backfillRowCounts`
+ * migration. Steady-state writes hit the cached counter and never call
+ * this.
+ */
+async function actualRowCount(
+  ctx: MutationCtx,
+  datasetId: Id<"datasets">,
+): Promise<number> {
+  const rows = await ctx.db
+    .query("datasetRows")
+    .withIndex("by_dataset", (q) => q.eq("datasetId", datasetId))
+    .collect();
+  return rows.length;
+}
+
 /**
  * Read all rows of a dataset.
  *
@@ -46,8 +66,26 @@ export const insert = internalMutation({
     sources: v.optional(v.array(v.string())),
   },
   handler: async (ctx, args) => {
-    await consumeQuotaForDataset(ctx, args.datasetId, 1);
-    return await ctx.db.insert("datasetRows", args);
+    // `consumeQuotaForDataset` returns the dataset doc so we don't
+    // double-read it.
+    const dataset = await consumeQuotaForDataset(ctx, args.datasetId, 1);
+
+    // Pre-insert count is either the cached counter (fast path) or — for
+    // datasets whose docs predate the rowCount field — recomputed once
+    // here. Subsequent inserts on the same dataset hit the fast path.
+    const previousCount =
+      typeof dataset.rowCount === "number"
+        ? dataset.rowCount
+        : await actualRowCount(ctx, args.datasetId);
+
+    const rowId = await ctx.db.insert("datasetRows", args);
+
+    // Maintain the denormalized counter the dashboard reads from. Same
+    // transaction as the row insert → atomic; quota-rejected inserts
+    // never bump the counter.
+    await ctx.db.patch(args.datasetId, { rowCount: previousCount + 1 });
+
+    return rowId;
   },
 });
 
@@ -114,6 +152,9 @@ export const clearByDataset = internalMutation({
     for (const row of rows) {
       await ctx.db.delete(row._id);
     }
+    // Reset the cached counter. We know the post-state exactly, so this
+    // doesn't need the read-then-add dance that `insert` / `remove` use.
+    await ctx.db.patch(args.datasetId, { rowCount: 0 });
     return rows.length;
   },
 });
@@ -163,6 +204,24 @@ export const remove = internalMutation({
   },
   handler: async (ctx, args) => {
     await assertRowInDataset(ctx, args.id, args.expectedDatasetId);
+
+    // Decrement the cached counter, self-healing if the dataset doc
+    // predates the rowCount field. `dataset` is guaranteed to exist —
+    // assertRowInDataset above verified the row belongs to it.
+    const dataset = await ctx.db.get(args.expectedDatasetId);
+    if (dataset) {
+      const previousCount =
+        typeof dataset.rowCount === "number"
+          ? dataset.rowCount
+          : await actualRowCount(ctx, args.expectedDatasetId);
+      await ctx.db.patch(args.expectedDatasetId, {
+        // clamp at 0 as a paranoid guard — counter should never go
+        // negative because we just confirmed the row exists, but a bug
+        // that drove it negative would manifest as an even weirder UI.
+        rowCount: Math.max(0, previousCount - 1),
+      });
+    }
+
     await ctx.db.delete(args.id);
   },
 });
diff --git a/frontend/convex/datasets.ts b/frontend/convex/datasets.ts
index e439576..281420b 100644
--- a/frontend/convex/datasets.ts
+++ b/frontend/convex/datasets.ts
@@ -30,13 +30,25 @@ const columnValidator = v.object({
 const PREVIEW_ROW_COUNT = 5;
 
 async function attachPreview(ctx: QueryCtx, dataset: Doc<"datasets">) {
-  const rows = await ctx.db
+  // Mini-table preview: just the first N rows. `.take` keeps the
+  // subscription's read set small — the dashboard's reactivity for the
+  // row count does NOT depend on this query. It depends on the
+  // denormalized `rowCount` field on the dataset doc itself, maintained
+  // by datasetRows.{insert,remove,clearByDataset}. That field is part of
+  // `dataset`, which is part of the query's read set, so patches to it
+  // invalidate the subscription and the card re-renders with the new
+  // count even after the first PREVIEW_ROW_COUNT rows.
+  const previewRows = await ctx.db
     .query("datasetRows")
     .withIndex("by_dataset", (q) => q.eq("datasetId", dataset._id))
     .take(PREVIEW_ROW_COUNT);
   return {
     ...dataset,
-    previewRows: rows.map((r) => r.data),
+    previewRows: previewRows.map((r) => r.data),
+    // Fallback to the preview length only when the dataset doc predates
+    // the `rowCount` field. Write paths self-heal on the next insert /
+    // remove; `datasets.backfillRowCounts` migrates every doc at once.
+    rowCount: dataset.rowCount ?? previewRows.length,
   };
 }
 
@@ -160,6 +172,7 @@ export const create = mutation({
       ownerId: identity.subject,
       status: "building",
       visibility: "private",
+      rowCount: 0,
     });
   },
 });
@@ -194,3 +207,38 @@ export const remove = mutation({
     await ctx.db.delete(dataset._id);
   },
 });
+
+/**
+ * One-shot migration: scan every dataset, count its rows, and patch
+ * `rowCount` to the true value. Idempotent and safe to re-run.
+ *
+ * Needed once after deploying the `rowCount` field — write paths
+ * self-heal on first hit, but datasets that haven't been written to
+ * since the field landed keep showing the preview-length fallback
+ * (capped at PREVIEW_ROW_COUNT). Running this promotes every doc to
+ * the fast path in one shot.
+ *
+ * Cost is O(total rows). Run from the convex CLI:
+ *   npx convex run datasets:backfillRowCounts
+ */
+export const backfillRowCounts = internalMutation({
+  args: {},
+  handler: async (ctx) => {
+    const datasets = await ctx.db.query("datasets").collect();
+    let patched = 0;
+    let alreadyCorrect = 0;
+    for (const ds of datasets) {
+      const rows = await ctx.db
+        .query("datasetRows")
+        .withIndex("by_dataset", (q) => q.eq("datasetId", ds._id))
+        .collect();
+      if (ds.rowCount === rows.length) {
+        alreadyCorrect++;
+        continue;
+      }
+      await ctx.db.patch(ds._id, { rowCount: rows.length });
+      patched++;
+    }
+    return { patched, alreadyCorrect, total: datasets.length };
+  },
+});
diff --git a/frontend/convex/publicSeed.ts b/frontend/convex/publicSeed.ts
index 304d026..68c49d7 100644
--- a/frontend/convex/publicSeed.ts
+++ b/frontend/convex/publicSeed.ts
@@ -376,7 +376,10 @@ export const seedPublicDatasets = internalMutation({
           continue;
         }
 
-        // Force-update: patch metadata + replace rows.
+        // Force-update: patch metadata + replace rows. Reset rowCount
+        // alongside the row replacement so the dashboard reflects the
+        // curated content immediately. We know the exact post-state
+        // (`ds.rows.length`), so no recount needed.
         await ctx.db.patch(tracked._id, {
           name: ds.name,
           description: ds.description,
@@ -384,6 +387,7 @@ export const seedPublicDatasets = internalMutation({
           columns: ds.columns,
           status: "live",
           visibility: "public",
+          rowCount: ds.rows.length,
         });
 
         const oldRows = await ctx.db
@@ -424,6 +428,7 @@ export const seedPublicDatasets = internalMutation({
         cadence: ds.cadence,
         visibility: "public",
         columns: ds.columns,
+        rowCount: ds.rows.length,
       });
 
       for (const row of ds.rows) {
diff --git a/frontend/convex/schema.ts b/frontend/convex/schema.ts
index 68cd55f..c1346a3 100644
--- a/frontend/convex/schema.ts
+++ b/frontend/convex/schema.ts
@@ -21,6 +21,15 @@ export default defineSchema({
     // time doesn't rely on `name` (which marketing changes). User-created
     // datasets do not set this. See convex/publicSeed.ts.
     seedKey: v.optional(v.string()),
+    // Denormalized row count maintained by `datasetRows.insert / remove /
+    // clearByDataset` and by the seed/create paths. Read by the dashboard
+    // card's "X rows" footer via `datasets.attachPreview` so the count
+    // stays reactive past the first PREVIEW_ROW_COUNT inserts (a query
+    // over `.take(5)` only invalidates when one of the first 5 rows
+    // changes, freezing the dashboard at 5). Optional for backward compat
+    // with rows created before this field existed — write paths self-heal
+    // on first hit, and `datasets.backfillRowCounts` migrates all at once.
+    rowCount: v.optional(v.number()),
     columns: v.array(
       v.object({
         name: v.string(),