diff --git a/src/Traits/HasStocks.php b/src/Traits/HasStocks.php
index 4d54af8..b79adf5 100644
--- a/src/Traits/HasStocks.php
+++ b/src/Traits/HasStocks.php
@@ -402,7 +402,13 @@ trait HasStocks
 
         $date = $date ?? now();
 
-        // Base stock: all COMPLETED entries except CLAIMED, filtered using the provided date
+        // Base stock: all COMPLETED entries except CLAIMED, filtered using
+        // the provided date. This intentionally does NOT gate by the ledger
+        // row's created_at — callers like {@see ProductStock::claim} pass a
+        // booking-window start (which can predate the seed row by seconds)
+        // and rightly expect the current physical inventory back. For
+        // historical "as of date X, ignoring later changes" queries, use
+        // {@see self::availableOnDate()} instead.
         $baseStock = $this->stocks()
             ->withoutGlobalScope('willExpire')
             ->where('status', StockStatus::COMPLETED->value)
@@ -667,7 +673,41 @@ trait HasStocks
             return PHP_INT_MAX;
         }
 
-        return $this->getAvailableStock($date);
+        // Historically-aware variant of {@see self::getAvailableStock()}:
+        // ledger rows created AFTER $date are excluded, so a DECREASE placed
+        // today doesn't retroactively reduce availability on a prior day.
+        // Day-level comparison (against end of $date's day) so a row seeded
+        // mid-day still counts for queries on that same day.
+        $dateDayEnd = Carbon::instance($date)->copy()->endOfDay();
+
+        $baseStock = $this->stocks()
+            ->withoutGlobalScope('willExpire')
+            ->where('status', StockStatus::COMPLETED->value)
+            ->where('type', '!=', StockType::CLAIMED->value)
+            ->where('created_at', '<=', $dateDayEnd)
+            ->where(function ($query) use ($date) {
+                $query->whereNull('expires_at')
+                    ->orWhere('expires_at', '>', $date);
+            })
+            ->sum('quantity');
+
+        // Add back claims that should not reduce availability at the given date.
+        $inactiveClaims = $this->stocks()
+            ->withoutGlobalScope('willExpire')
+            ->where('type', StockType::CLAIMED->value)
+            ->where('status', StockStatus::PENDING->value)
+            ->where(function ($query) use ($date) {
+                $query->where(function ($q) use ($date) {
+                    $q->whereNotNull('claimed_from')
+                        ->where('claimed_from', '>', $date);
+                })->orWhere(function ($q) use ($date) {
+                    $q->whereNotNull('expires_at')
+                        ->where('expires_at', '<=', $date);
+                });
+            })
+            ->sum('quantity');
+
+        return max(0, $baseStock + $inactiveClaims);
     }
 
     /**
@@ -734,6 +774,14 @@ trait HasStocks
                 if ($stock->expires_at && $stock->expires_at->between($dayStart, $dayEnd)) {
                     $events[] = Carbon::parse($stock->expires_at);
                 }
+                // The moment a COMPLETED entry becomes effective is itself a
+                // transition point — without sampling here, a DECREASE at
+                // 13:32 followed by an INCREASE at 17:00 (or vice versa)
+                // would be invisible to min/max if we only inspected day
+                // boundaries.
+                if ($stock->created_at && $stock->created_at->between($dayStart, $dayEnd)) {
+                    $events[] = Carbon::parse($stock->created_at);
+                }
             }
 
             // Remove exact duplicates
@@ -743,11 +791,21 @@ trait HasStocks
             $dayMax = PHP_INT_MIN;
 
             // Check availability at each event timestamp to find min/max for the day
+            $eventDayEnd = $dayEnd->copy();
             foreach ($events as $eventTime) {
                 $available = 0;
                 foreach ($allStocks as $stock) {
                     if ($stock->status === StockStatus::COMPLETED && $stock->type !== StockType::CLAIMED) {
-                        if (is_null($stock->expires_at) || $stock->expires_at > $eventTime) {
+                        // A COMPLETED entry only contributes from the day it
+                        // was created — without this gate, a DECREASE from a
+                        // loan placed today would retroactively reduce
+                        // availability on every prior day in the grid.
+                        // Compared at day granularity (against end-of-day of
+                        // the rendered day) so a stock seeded mid-day still
+                        // contributes for every event in that same day.
+                        $hasStarted = $stock->created_at === null || $stock->created_at <= $eventDayEnd;
+                        $notExpired = is_null($stock->expires_at) || $stock->expires_at > $eventTime;
+                        if ($hasStarted && $notExpired) {
                             $available += $stock->quantity;
                         }
                     } elseif ($stock->status === StockStatus::PENDING && $stock->type === StockType::CLAIMED) {
diff --git a/tests/Feature/Product/HistoricalAvailabilityTest.php b/tests/Feature/Product/HistoricalAvailabilityTest.php
new file mode 100644
index 0000000..2d0d317
--- /dev/null
+++ b/tests/Feature/Product/HistoricalAvailabilityTest.php
@@ -0,0 +1,201 @@
+<?php
+
+namespace Blax\Shop\Tests\Feature\Product;
+
+use Blax\Shop\Enums\ProductStatus;
+use Blax\Shop\Enums\ProductType;
+use Blax\Shop\Models\Product;
+use Blax\Shop\Tests\TestCase;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Carbon;
+use PHPUnit\Framework\Attributes\Test;
+
+/**
+ * Regression coverage for the bug where stock ledger entries with no
+ * `expires_at` were treated as if they had always existed — so a DECREASE
+ * row created today retroactively reduced availability for every prior day.
+ *
+ * Real-world reproducer (from a librarian's report):
+ *   1. Book seeded with 5 copies at the start of the month
+ *   2. A member loans one copy on day 17
+ *   3. `shop:stocks:availability` for May rendered 4 available for ALL 31
+ *      days — including May 1–16, which is wrong because the loan didn't
+ *      exist yet on those days.
+ *
+ * The fix scopes COMPLETED stock entries to their `created_at` boundary in
+ * the historical-query paths ({@see HasStocks::calendarAvailability} and
+ * {@see HasStocks::availableOnDate}): an entry only contributes to
+ * availability on date $X if it was persisted on or before $X. The
+ * day-level comparison (against end-of-day of $X) means a row seeded
+ * mid-day still counts for queries on that same day.
+ *
+ * {@see HasStocks::getAvailableStock} is intentionally NOT gated — it's
+ * the "current snapshot" API and is called by {@see ProductStock::claim}
+ * with future/past booking dates, where the caller wants the live
+ * physical inventory. CLAIMED entries already model both ends of their
+ * window via `claimed_from` / `expires_at`, so this fix only touches the
+ * INCREASE/DECREASE/RETURN code path.
+ */
+class HistoricalAvailabilityTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private function newProduct(): Product
+    {
+        return Product::create([
+            'name' => 'Hyperion',
+            'sku' => 'HYP-HIST',
+            'type' => ProductType::SIMPLE,
+            'status' => ProductStatus::PUBLISHED,
+            'is_visible' => true,
+            'manage_stock' => true,
+        ]);
+    }
+
+    #[Test]
+    public function decrease_today_does_not_retroactively_reduce_yesterday(): void
+    {
+        // Day 1: seed inventory. Day 10: loan one copy.
+        Carbon::setTestNow(Carbon::parse('2026-05-01 09:00:00'));
+        $product = $this->newProduct();
+        $product->increaseStock(5);
+
+        Carbon::setTestNow(Carbon::parse('2026-05-10 13:32:00'));
+        $product->decreaseStock(1);
+
+        // Availability on day 5 (before the loan): still 5 copies.
+        $this->assertSame(
+            5,
+            $product->availableOnDate(Carbon::parse('2026-05-05 12:00:00')),
+            'past dates must not be affected by a later DECREASE',
+        );
+
+        // Availability on day 10 after the loan happened: 4.
+        $this->assertSame(
+            4,
+            $product->availableOnDate(Carbon::parse('2026-05-10 14:00:00')),
+            'present-day availability reflects the loan',
+        );
+
+        // Availability on day 20 (no further activity): still 4.
+        $this->assertSame(
+            4,
+            $product->availableOnDate(Carbon::parse('2026-05-20 09:00:00')),
+        );
+    }
+
+    #[Test]
+    public function increase_today_does_not_retroactively_inflate_yesterday(): void
+    {
+        // Symmetric guard: stock added today shouldn't make yesterday richer.
+        Carbon::setTestNow(Carbon::parse('2026-05-01 09:00:00'));
+        $product = $this->newProduct();
+        $product->increaseStock(2);
+
+        Carbon::setTestNow(Carbon::parse('2026-05-15 10:00:00'));
+        $product->increaseStock(3); // restock — three more copies arrived
+
+        $this->assertSame(
+            2,
+            $product->availableOnDate(Carbon::parse('2026-05-10 12:00:00')),
+            'past dates only see the initial 2 copies',
+        );
+        $this->assertSame(
+            5,
+            $product->availableOnDate(Carbon::parse('2026-05-20 12:00:00')),
+            'after the restock, total is 5',
+        );
+    }
+
+    #[Test]
+    public function calendar_availability_reflects_the_actual_timeline(): void
+    {
+        // This is the user's reported scenario almost verbatim. The library
+        // had its 5 copies long before the queried month, so we seed in April
+        // — otherwise the INCREASE row's created_at would itself split day 1
+        // (legitimately) and complicate the assertions.
+        Carbon::setTestNow(Carbon::parse('2026-04-15 09:00:00'));
+        $product = $this->newProduct();
+        $product->increaseStock(5);
+
+        // Loan on May 17 13:32 — exactly as the bug report described.
+        Carbon::setTestNow(Carbon::parse('2026-05-17 13:32:00'));
+        $product->decreaseStock(1);
+
+        $calendar = $product->calendarAvailability(
+            Carbon::parse('2026-05-01 00:00:00'),
+            Carbon::parse('2026-05-31 23:59:59'),
+        );
+
+        $dates = $calendar['dates'];
+
+        // Days 1–16 (before the loan): full availability.
+        foreach (['2026-05-01', '2026-05-10', '2026-05-16'] as $day) {
+            $this->assertSame(
+                ['min' => 5, 'max' => 5],
+                $dates[$day],
+                "calendar must show 5 available on {$day} (before the loan)",
+            );
+        }
+
+        // Day 17 (the loan day itself): the calendar uses day-level
+        // granularity for the created_at gate, so a stock change anywhere
+        // during the day counts at every event on that day. Result: 4 across
+        // the board, even though the actual transition happened at 13:32.
+        // This is a deliberate trade-off — instant-level granularity created
+        // test-fixture chaos for any seed-then-query-now pattern, since the
+        // calendar's day boundaries always landed before the seed timestamp.
+        $this->assertSame(
+            ['min' => 4, 'max' => 4],
+            $dates['2026-05-17'],
+        );
+
+        // Days 18–31 (loan still out, nothing returned): 4 available.
+        foreach (['2026-05-18', '2026-05-25', '2026-05-31'] as $day) {
+            $this->assertSame(
+                ['min' => 4, 'max' => 4],
+                $dates[$day],
+                "calendar must show 4 available on {$day} (loan in effect)",
+            );
+        }
+    }
+
+    #[Test]
+    public function calendar_summary_reports_the_correct_min_and_max(): void
+    {
+        // 5 copies seeded before the queried month, 1 loaned mid-month →
+        // calendar should report max_available=5 (some days), min_available=4
+        // (after the loan). Before the fix, both would have been 4 because
+        // every day rendered 4-4.
+        Carbon::setTestNow(Carbon::parse('2026-04-15 09:00:00'));
+        $product = $this->newProduct();
+        $product->increaseStock(5);
+
+        Carbon::setTestNow(Carbon::parse('2026-05-17 13:32:00'));
+        $product->decreaseStock(1);
+
+        $calendar = $product->calendarAvailability(
+            Carbon::parse('2026-05-01 00:00:00'),
+            Carbon::parse('2026-05-31 23:59:59'),
+        );
+
+        $this->assertSame(5, $calendar['max_available'], 'peak availability for the month is 5');
+        $this->assertSame(4, $calendar['min_available'], 'trough availability is 4 after the loan');
+    }
+
+    #[Test]
+    public function available_on_date_in_the_future_anticipates_no_changes(): void
+    {
+        // Asking about a future date with no scheduled changes should return
+        // current availability — the loan persists, so 4 stays 4.
+        Carbon::setTestNow(Carbon::parse('2026-05-17 13:32:00'));
+        $product = $this->newProduct();
+        $product->increaseStock(5);
+        $product->decreaseStock(1);
+
+        $this->assertSame(
+            4,
+            $product->availableOnDate(Carbon::parse('2026-06-15 12:00:00')),
+        );
+    }
+}