diff --git a/app/Services/Projection/PipelineAllocationService.php b/app/Services/Projection/PipelineAllocationService.php
index 66b4cf9..8540bf2 100644
--- a/app/Services/Projection/PipelineAllocationService.php
+++ b/app/Services/Projection/PipelineAllocationService.php
@@ -81,7 +81,7 @@ private function calculateBucketAllocation(Bucket $bucket, int $remainingAmount)
      */
     private function calculateFixedAllocation(Bucket $bucket, int $remainingAmount): int
     {
-        $bucketCapacity = (int) ($bucket->allocation_value ?? 0);
+        $bucketCapacity = (int) round($bucket->getEffectiveCapacity());
         $currentBalance = $bucket->getCurrentBalance();
         $availableSpace = max(0, $bucketCapacity - $currentBalance);
 
diff --git a/tests/Unit/PipelineAllocationServiceTest.php b/tests/Unit/PipelineAllocationServiceTest.php
index 6a89d2a..60a9aef 100644
--- a/tests/Unit/PipelineAllocationServiceTest.php
+++ b/tests/Unit/PipelineAllocationServiceTest.php
@@ -339,4 +339,74 @@ public function test_percentage_allocation_with_insufficient_remaining_amount()
         $this->assertEquals(95000, $draws[0]->amount);
         $this->assertEquals(1000, $draws[1]->amount); // 20% of $50
     }
+
+    public function test_fixed_allocation_respects_buffer_multiplier(): void
+    {
+        Bucket::factory()->create([
+            'scenario_id' => $this->scenario->id,
+            'allocation_type' => BucketAllocationTypeEnum::FIXED_LIMIT,
+            'allocation_value' => 50000,
+            'buffer_multiplier' => 1.0,
+            'starting_amount' => 0,
+            'priority' => 1,
+        ]);
+
+        // Effective capacity = 50000 * (1 + 1.0) = 100000
+        $draws = $this->service->allocateInflow($this->scenario, 100000);
+
+        $this->assertCount(1, $draws);
+        $this->assertEquals(100000, $draws[0]->amount);
+    }
+
+    public function test_fixed_allocation_with_buffer_partially_filled(): void
+    {
+        $bucket = Bucket::factory()->create([
+            'scenario_id' => $this->scenario->id,
+            'allocation_type' => BucketAllocationTypeEnum::FIXED_LIMIT,
+            'allocation_value' => 50000,
+            'buffer_multiplier' => 1.0,
+            'starting_amount' => 30000,
+            'priority' => 1,
+        ]);
+
+        // Effective capacity = 100000, balance = 30000, available = 70000
+        $draws = $this->service->allocateInflow($this->scenario, 80000);
+
+        $this->assertCount(1, $draws);
+        $this->assertEquals(70000, $draws[0]->amount);
+    }
+
+    public function test_buffer_does_not_affect_percentage_allocation(): void
+    {
+        Bucket::factory()->create([
+            'scenario_id' => $this->scenario->id,
+            'allocation_type' => BucketAllocationTypeEnum::PERCENTAGE,
+            'allocation_value' => 25.00,
+            'buffer_multiplier' => 1.0,
+            'starting_amount' => 0,
+            'priority' => 1,
+        ]);
+
+        $draws = $this->service->allocateInflow($this->scenario, 100000);
+
+        $this->assertCount(1, $draws);
+        $this->assertEquals(25000, $draws[0]->amount); // 25% of 100000
+    }
+
+    public function test_buffer_does_not_affect_unlimited_allocation(): void
+    {
+        Bucket::factory()->create([
+            'scenario_id' => $this->scenario->id,
+            'allocation_type' => BucketAllocationTypeEnum::UNLIMITED,
+            'allocation_value' => null,
+            'buffer_multiplier' => 1.0,
+            'starting_amount' => 0,
+            'priority' => 1,
+        ]);
+
+        $draws = $this->service->allocateInflow($this->scenario, 100000);
+
+        $this->assertCount(1, $draws);
+        $this->assertEquals(100000, $draws[0]->amount);
+    }
 }