diff --git a/src/window.zig b/src/window.zig
index aeba2e8..b68e512 100644
--- a/src/window.zig
+++ b/src/window.zig
@@ -1445,3 +1445,161 @@ test "orderedIndices propagates OutOfMemory without leaking" {
     try std.testing.expectError(error.OutOfMemory, orderedIndices(failing.allocator(), rows.items, &.{}, &.{}));
 }
 
+test "computeMany matches calling compute() once per spec, sharing one partition/order/frame" {
+    const allocator = std.testing.allocator;
+    var rows = std.ArrayList(Row).init(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const data = [_]struct { city: []const u8, amount: i64 }{
+        .{ .city = "warsaw", .amount = 10 },
+        .{ .city = "krakow", .amount = 9 },
+        .{ .city = "warsaw", .amount = 20 },
+        .{ .city = "krakow", .amount = 2 },
+    };
+    for (data) |d| {
+        try rows.append(try makeRow(allocator, &.{
+            .{ .name = "city", .value = .{ .text = d.city } },
+            .{ .name = "amount", .value = .{ .int = d.amount } },
+        }));
+    }
+
+    const partition = [_][]const u8{"city"};
+    const order = [_]querymod.OrderBy{.{ .field = "amount" }};
+    const specs = [_]WindowSpec{
+        .{ .field = "amount", .kind = .sum },
+        .{ .field = "amount", .kind = .avg },
+        .{ .field = "", .kind = .row_number },
+    };
+
+    const many = try computeMany(allocator, rows.items, &partition, &order, &specs, .rows);
+    defer freeManyResults(allocator, many);
+
+    for (specs, 0..) |spec, specIdx| {
+        const solo = try compute(allocator, rows.items, &partition, &order, spec, .rows);
+        defer freeResults(allocator, solo);
+        for (rows.items, 0..) |_, rowIdx| {
+            try std.testing.expect(rowmod.compare(many[rowIdx][specIdx], solo[rowIdx]) == .eq);
+        }
+    }
+}
+
+test "computeMany keeps min/max text results independently owned per row and per spec" {
+    const allocator = std.testing.allocator;
+    var rows = std.ArrayList(Row).init(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const names = [_][]const u8{ "mango", "apple", "kiwi" };
+    for (names) |n| {
+        try rows.append(try makeRow(allocator, &.{.{ .name = "name", .value = .{ .text = n } }}));
+    }
+
+    const specs = [_]WindowSpec{
+        .{ .field = "name", .kind = .min },
+        .{ .field = "name", .kind = .max },
+    };
+    const results = try computeMany(allocator, rows.items, &.{}, &.{}, &specs, .rows);
+    defer freeManyResults(allocator, results);
+
+    for (results) |row| {
+        try std.testing.expectEqualStrings("apple", row[0].text);
+        try std.testing.expectEqualStrings("mango", row[1].text);
+    }
+    // Every row's `min` slice is its own allocation, not a shared pointer -
+    // `freeManyResults` frees each independently, which the testing
+    // allocator would already reject as a double free if they aliased.
+    try std.testing.expect(results[0][0].text.ptr != results[1][0].text.ptr);
+}
+
+test "computeMany with zero specs returns one empty values slice per row, no crash" {
+    const allocator = std.testing.allocator;
+    var rows = try threeRowsOnePartition(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const results = try computeMany(allocator, rows.items, &.{}, &.{}, &.{}, .rows);
+    defer freeManyResults(allocator, results);
+    try std.testing.expectEqual(@as(usize, 3), results.len);
+    for (results) |row| try std.testing.expectEqual(@as(usize, 0), row.len);
+}
+
+test "computeMany propagates OutOfMemory without leaking, at an early allocation" {
+    const allocator = std.testing.allocator;
+    var rows = try threeRowsOnePartition(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const specs = [_]WindowSpec{
+        .{ .field = "score", .kind = .sum },
+        .{ .field = "", .kind = .row_number },
+    };
+    var failing = std.testing.FailingAllocator.init(allocator, .{ .fail_index = 0 });
+    try std.testing.expectError(error.OutOfMemory, computeMany(failing.allocator(), rows.items, &.{}, &.{}, &specs, .rows));
+}
+
+test "computeMany propagates OutOfMemory without leaking, mid-way through the row-major transpose" {
+    const allocator = std.testing.allocator;
+    var rows = try threeRowsOnePartition(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const specs = [_]WindowSpec{
+        .{ .field = "score", .kind = .sum },
+        .{ .field = "team", .kind = .min },
+    };
+    // Large enough to run past both columns' own computation (sum has no
+    // extra allocations per row; min dupes a `Value` per row observed) and
+    // into the per-row `rowValues`/`dupe` allocations the transpose loop
+    // itself makes - proven by the assertion below, not by counting by hand.
+    var failIndex: usize = 0;
+    while (failIndex < 40) : (failIndex += 1) {
+        var failing = std.testing.FailingAllocator.init(allocator, .{ .fail_index = failIndex });
+        const result = computeMany(failing.allocator(), rows.items, &.{}, &.{}, &specs, .rows);
+        if (result) |ok| {
+            freeManyResults(allocator, ok);
+            break;
+        } else |err| {
+            try std.testing.expectEqual(error.OutOfMemory, err);
+        }
+    } else return error.TestUnexpectedResult;
+}
+
+test "lag/lead default offset of 1: NULL (default) at the edge, adjacent value otherwise" {
+    const allocator = std.testing.allocator;
+    var rows = std.ArrayList(Row).init(allocator);
+    defer {
+        for (rows.items) |*r| r.deinit();
+        rows.deinit();
+    }
+    const data = [_]struct { day: i64, amount: i64 }{
+        .{ .day = 1, .amount = 10 },
+        .{ .day = 2, .amount = 20 },
+        .{ .day = 3, .amount = 30 },
+    };
+    for (data) |d| {
+        try rows.append(try makeRow(allocator, &.{
+            .{ .name = "day", .value = .{ .int = d.day } },
+            .{ .name = "amount", .value = .{ .int = d.amount } },
+        }));
+    }
+    const order = [_]querymod.OrderBy{.{ .field = "day" }};
+
+    const lag = try compute(allocator, rows.items, &.{}, &order, .{ .field = "amount", .kind = .lag }, .rows);
+    defer freeResults(allocator, lag);
+    try std.testing.expectEqual(rowmod.ValueTag.none, @as(rowmod.ValueTag, lag[0]));
+    try std.testing.expectEqual(@as(i64, 10), lag[1].int);
+    try std.testing.expectEqual(@as(i64, 20), lag[2].int);
+
+    const lead = try compute(allocator, rows.items, &.{}, &order, .{ .field = "amount", .kind = .lead }, .rows);
+    defer freeResults(allocator, lead);
+    try std.testing.expectEqual(@as(i64, 20), lead[0].int);
+    try std.testing.expectEqual(@as(i64, 30), lead[1].int);
+    try std.testing.expectEqual(rowmod.ValueTag.none, @as(rowmod.ValueTag, lead[2]));
+}
+