diff --git a/app/Actions/CreateBucketAction.php b/app/Actions/CreateBucketAction.php
index e19771f..7e0c0c0 100644
--- a/app/Actions/CreateBucketAction.php
+++ b/app/Actions/CreateBucketAction.php
@@ -18,6 +18,7 @@ public function execute(
         BucketTypeEnum $type = BucketTypeEnum::NEED,
         ?float $allocationValue = null,
         ?int $priority = null,
+        ?float $bufferMultiplier = null,
     ): Bucket {
         // Validate type + allocation type constraints
         $this->validateTypeConstraints($type, $allocationType);
@@ -30,12 +31,23 @@ public function execute(
         // Validate allocation value based on type
         $this->validateAllocationValue($allocationType, $allocationValue);
 
+        // Validate and normalize buffer multiplier
+        $bufferMultiplier = $bufferMultiplier ?? 0.0;
+        if ($bufferMultiplier < 0) {
+            throw new InvalidArgumentException('Buffer multiplier must be non-negative');
+        }
+
         // Set allocation_value to null for unlimited buckets
         if ($allocationType === BucketAllocationTypeEnum::UNLIMITED) {
             $allocationValue = null;
         }
 
-        return DB::transaction(function () use ($scenario, $name, $allocationType, $allocationValue, $priority, $type) {
+        // Buffer only applies to fixed_limit buckets
+        if ($allocationType !== BucketAllocationTypeEnum::FIXED_LIMIT) {
+            $bufferMultiplier = 0.0;
+        }
+
+        return DB::transaction(function () use ($scenario, $name, $allocationType, $allocationValue, $priority, $type, $bufferMultiplier) {
             // Determine priority (append to end if not specified)
             if ($priority === null) {
                 $maxPriority = $scenario->buckets()->max('priority') ?? 0;
@@ -68,6 +80,7 @@ public function execute(
                 'sort_order' => $priority, // Start with sort_order matching priority
                 'allocation_type' => $allocationType,
                 'allocation_value' => $allocationValue,
+                'buffer_multiplier' => $bufferMultiplier,
             ]);
         });
     }
diff --git a/tests/Unit/Actions/CreateBucketActionTest.php b/tests/Unit/Actions/CreateBucketActionTest.php
index aac2d0c..1102032 100644
--- a/tests/Unit/Actions/CreateBucketActionTest.php
+++ b/tests/Unit/Actions/CreateBucketActionTest.php
@@ -359,4 +359,69 @@ public function test_creates_buckets_in_database_transaction(): void
         $this->assertEquals('Bucket 2', $buckets[0]->name); // New bucket at priority 1
         $this->assertEquals('Bucket 1', $buckets[1]->name); // Original bucket shifted to priority 2
     }
+
+    public function test_can_create_fixed_limit_bucket_with_buffer_multiplier(): void
+    {
+        $bucket = $this->action->execute(
+            $this->scenario,
+            'Buffered Bucket',
+            BucketAllocationTypeEnum::FIXED_LIMIT,
+            allocationValue: 50000,
+            bufferMultiplier: 1.5,
+        );
+
+        $this->assertEquals('1.50', $bucket->buffer_multiplier);
+    }
+
+    public function test_buffer_multiplier_defaults_to_zero(): void
+    {
+        $bucket = $this->action->execute(
+            $this->scenario,
+            'No Buffer Bucket',
+            BucketAllocationTypeEnum::FIXED_LIMIT,
+            allocationValue: 50000,
+        );
+
+        $this->assertEquals('0.00', $bucket->buffer_multiplier);
+    }
+
+    public function test_buffer_multiplier_forced_to_zero_for_percentage_bucket(): void
+    {
+        $bucket = $this->action->execute(
+            $this->scenario,
+            'Percentage Bucket',
+            BucketAllocationTypeEnum::PERCENTAGE,
+            allocationValue: 25.0,
+            bufferMultiplier: 1.0,
+        );
+
+        $this->assertEquals('0.00', $bucket->buffer_multiplier);
+    }
+
+    public function test_buffer_multiplier_forced_to_zero_for_unlimited_bucket(): void
+    {
+        $bucket = $this->action->execute(
+            $this->scenario,
+            'Unlimited Bucket',
+            BucketAllocationTypeEnum::UNLIMITED,
+            BucketTypeEnum::OVERFLOW,
+            bufferMultiplier: 1.0,
+        );
+
+        $this->assertEquals('0.00', $bucket->buffer_multiplier);
+    }
+
+    public function test_throws_exception_for_negative_buffer_multiplier(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Buffer multiplier must be non-negative');
+
+        $this->action->execute(
+            $this->scenario,
+            'Bad Buffer',
+            BucketAllocationTypeEnum::FIXED_LIMIT,
+            allocationValue: 50000,
+            bufferMultiplier: -0.5,
+        );
+    }
 }