diff --git a/openapi.yaml b/openapi.yaml
index 1a243387..ebfe00d6 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -9421,6 +9421,14 @@ paths:
                 license_plate:
                   type: string
                   description: Required for START command
+                wash_type:
+                  type: string
+                  enum: [Manual, Machine]
+                  description: Optional customer-selected wash type for START. When provided, Manual and Machine start actions use this explicit choice instead of inferring mode from allowed services.
+                wash_mode:
+                  type: string
+                  enum: [manual, machine]
+                  description: Lowercase alias for wash_type accepted by backend clients.
                 customer_number:
                   type: integer
                   description: Required for START and RESERVE commands. The authenticated customer's number is applied server-side when omitted by user clients.
diff --git a/services/nginx/app/modules/selfserve/classes/selfserve_lane_command_arguments.php b/services/nginx/app/modules/selfserve/classes/selfserve_lane_command_arguments.php
index dd8510f6..43d168ce 100644
--- a/services/nginx/app/modules/selfserve/classes/selfserve_lane_command_arguments.php
+++ b/services/nginx/app/modules/selfserve/classes/selfserve_lane_command_arguments.php
@@ -7,6 +7,7 @@ class selfserve_lane_command_arguments
     public ?string $license_plate = null;
     public ?int $customer_number = null;
     public ?int $subuser_id = null;
+    public ?string $wash_mode = null;
     public bool $defer_relay_side_effects = false;
 
     /**
@@ -32,6 +33,22 @@ class selfserve_lane_command_arguments
         return $this;
     }
 
+    public function setWashMode(?string $wash_mode): self
+    {
+        $normalized = strtolower(trim((string)$wash_mode));
+        if ($wash_mode === null || $normalized === '') {
+            $this->wash_mode = null;
+            return $this;
+        }
+
+        if (!in_array($normalized, ['manual', 'machine'], true)) {
+            throw new \InvalidArgumentException('Invalid wash type: ' . $wash_mode);
+        }
+
+        $this->wash_mode = $normalized;
+        return $this;
+    }
+
     public function setDeferRelaySideEffects(bool $defer_relay_side_effects): self
     {
         $this->defer_relay_side_effects = $defer_relay_side_effects;
@@ -50,6 +67,12 @@ class selfserve_lane_command_arguments
             if (array_key_exists('subuser_id', $params)) {
                 $this->setSubuserId($params['subuser_id'] === null ? null : (int)$params['subuser_id']);
             }
+            if (array_key_exists('wash_type', $params)) {
+                $this->setWashMode($params['wash_type'] === null ? null : (string)$params['wash_type']);
+            }
+            if (array_key_exists('wash_mode', $params)) {
+                $this->setWashMode($params['wash_mode'] === null ? null : (string)$params['wash_mode']);
+            }
             if (array_key_exists('defer_relay_side_effects', $params)) {
                 $this->setDeferRelaySideEffects(filter_var(
                     $params['defer_relay_side_effects'],
diff --git a/services/nginx/app/modules/selfserve/traits/selfserve_lane_command_t.php b/services/nginx/app/modules/selfserve/traits/selfserve_lane_command_t.php
index def685a0..304891bf 100644
--- a/services/nginx/app/modules/selfserve/traits/selfserve_lane_command_t.php
+++ b/services/nginx/app/modules/selfserve/traits/selfserve_lane_command_t.php
@@ -171,12 +171,12 @@ trait selfserve_lane_command_t
      * Ensure machine relay is ON when a wash starts, when it is allowed by configuration.
      * If machine relay is not configured, this is a no-op.
      */
-    protected function setMachineRelayStatusForWashStart(): void
+    protected function setMachineRelayStatusForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
         if (!$this->isRelayConfigured(selfserve_lane_relay::MACHINE)) {
             return;
         }
-        if ($this->isMachineWashSelectedAndAvailableForStart()) {
+        if ($this->isMachineWashSelectedAndAvailableForStart($arguments)) {
             try {
                 $this->setMachineRelayStatusHard(true);
             } catch (\Throwable) {
@@ -194,38 +194,39 @@ trait selfserve_lane_command_t
 
     /**
      * Keep the program picker relay aligned with the selected wash mode at START.
-     * It is ON only when the active self-serve session is allowed to start machine wash.
+     * It is ON only when the customer explicitly selected machine wash.
      */
-    protected function setProgramPickerRelayStatusForWashStart(): void
+    protected function setProgramPickerRelayStatusForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
         if (!$this->isRelayConfigured(selfserve_lane_relay::MACHINE_PROGRAM_PICKER)) {
             return;
         }
 
         try {
-            $shouldEnable = $this->isMachineWashSelectedAndAvailableForStart();
+            $shouldEnable = $this->isExplicitMachineWashModeSelectedForStart($arguments)
+                && $this->isMachineWashSelectedAndAvailableForStart($arguments);
             $this->setMachineProgramPickerRelayStatusHard($shouldEnable);
         } catch (\Throwable) {
             // Best effort only; wash start must continue.
         }
     }
 
-    protected function setProgramPickerRelayStatusFromSelectedServiceForWashStart(): void
+    protected function setProgramPickerRelayStatusFromSelectedServiceForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
         if (!$this->isRelayConfigured(selfserve_lane_relay::MACHINE_PROGRAM_PICKER)) {
             return;
         }
 
         try {
-            $this->setMachineProgramPickerRelayStatusHard($this->isMachineServiceSelectedForWashStart());
+            $this->setMachineProgramPickerRelayStatusHard($this->shouldEnableProgramPickerRelayForWashStart($arguments));
         } catch (\Throwable) {
             // Best effort only; wash start must continue.
         }
     }
 
-    protected function isMachineWashSelectedAndAvailableForStart(): bool
+    protected function isMachineWashSelectedAndAvailableForStart(?selfserve_lane_command_arguments $arguments = null): bool
     {
-        if (!$this->isMachineServiceSelectedForWashStart()) {
+        if (!$this->shouldEnableSelectedMachineServiceForWashStart($arguments)) {
             return false;
         }
 
@@ -248,6 +249,39 @@ trait selfserve_lane_command_t
         }
     }
 
+    protected function shouldEnableSelectedMachineServiceForWashStart(?selfserve_lane_command_arguments $arguments = null): bool
+    {
+        if (!$this->isMachineWashModeSelectedForStart($arguments)) {
+            return false;
+        }
+
+        return $this->isMachineServiceSelectedForWashStart();
+    }
+
+    protected function shouldEnableProgramPickerRelayForWashStart(?selfserve_lane_command_arguments $arguments = null): bool
+    {
+        return $this->isExplicitMachineWashModeSelectedForStart($arguments)
+            && $this->isMachineServiceSelectedForWashStart();
+    }
+
+    protected function isExplicitMachineWashModeSelectedForStart(?selfserve_lane_command_arguments $arguments = null): bool
+    {
+        return $arguments !== null && $arguments->wash_mode === selfserve_studio_actions::MODE_MACHINE;
+    }
+
+    protected function isMachineWashModeSelectedForStart(?selfserve_lane_command_arguments $arguments = null): bool
+    {
+        if ($arguments !== null && $arguments->wash_mode === selfserve_studio_actions::MODE_MANUAL) {
+            return false;
+        }
+
+        if ($arguments !== null && $arguments->wash_mode === selfserve_studio_actions::MODE_MACHINE) {
+            return true;
+        }
+
+        return $this->isMachineServiceSelectedForWashStart();
+    }
+
     protected function isMachineServiceSelectedForWashStart(): bool
     {
         try {
@@ -349,17 +383,24 @@ trait selfserve_lane_command_t
     protected function runRelaySideEffectsForWashStart(selfserve_lane_command_arguments $arguments): void
     {
         if ($arguments->defer_relay_side_effects) {
-            $this->setProgramPickerRelayStatusFromSelectedServiceForWashStart();
+            $this->setProgramPickerRelayStatusFromSelectedServiceForWashStart($arguments);
             return;
         }
 
         $this->turnOnCleanerRelayForWashStart();
-        $this->setProgramPickerRelayStatusForWashStart();
-        $this->setMachineRelayStatusForWashStart();
+        $this->setProgramPickerRelayStatusForWashStart($arguments);
+        $this->setMachineRelayStatusForWashStart($arguments);
     }
 
-    protected function resolveSelfServeActionWashModeForStart(): string
+    protected function resolveSelfServeActionWashModeForStart(?selfserve_lane_command_arguments $arguments = null): string
     {
+        if ($arguments !== null && in_array($arguments->wash_mode, [
+            selfserve_studio_actions::MODE_MANUAL,
+            selfserve_studio_actions::MODE_MACHINE,
+        ], true)) {
+            return $arguments->wash_mode;
+        }
+
         if ($this->isMachineServiceSelectedForWashStart()) {
             return selfserve_studio_actions::MODE_MACHINE;
         }
@@ -634,7 +675,7 @@ trait selfserve_lane_command_t
                     $this->runRelaySideEffectsForWashStart($arguments);
                     $this->runPublishedStudioActions(
                         selfserve_studio_actions::EVENT_WASH_START_COMMAND,
-                        $this->resolveSelfServeActionWashModeForStart(),
+                        $this->resolveSelfServeActionWashModeForStart($arguments),
                         [
                             'customer_number' => (int)$customer_number,
                             'reg' => $license_plate,
diff --git a/services/nginx/app/openapi.yaml b/services/nginx/app/openapi.yaml
index 1a243387..ebfe00d6 100644
--- a/services/nginx/app/openapi.yaml
+++ b/services/nginx/app/openapi.yaml
@@ -9421,6 +9421,14 @@ paths:
                 license_plate:
                   type: string
                   description: Required for START command
+                wash_type:
+                  type: string
+                  enum: [Manual, Machine]
+                  description: Optional customer-selected wash type for START. When provided, Manual and Machine start actions use this explicit choice instead of inferring mode from allowed services.
+                wash_mode:
+                  type: string
+                  enum: [manual, machine]
+                  description: Lowercase alias for wash_type accepted by backend clients.
                 customer_number:
                   type: integer
                   description: Required for START and RESERVE commands. The authenticated customer's number is applied server-side when omitted by user clients.
diff --git a/services/nginx/app/tests/Api/SelfserveCustomerStartApiTest.php b/services/nginx/app/tests/Api/SelfserveCustomerStartApiTest.php
index fdb06877..f7e4b398 100644
--- a/services/nginx/app/tests/Api/SelfserveCustomerStartApiTest.php
+++ b/services/nginx/app/tests/Api/SelfserveCustomerStartApiTest.php
@@ -76,6 +76,7 @@ it('allows the customer self-serve start sequence without department access', fu
             'lane_id' => $laneId,
             'command' => 'START',
             'license_plate' => $reg,
+            'wash_type' => 'Manual',
             'defer_relay_side_effects' => true,
         ], $headers)
         ->assertStatus(200)
@@ -131,6 +132,7 @@ it('marks the active customer session relay-enabled after machine relay enable',
             'lane_id' => $laneId,
             'command' => 'START',
             'license_plate' => $reg,
+            'wash_type' => 'Machine',
             'defer_relay_side_effects' => true,
         ], $headers)
         ->assertStatus(200)
diff --git a/services/nginx/app/tests/Api/SelfserveLaneCommandApiTest.php b/services/nginx/app/tests/Api/SelfserveLaneCommandApiTest.php
index 4ffdd7d4..65f0cfb0 100644
--- a/services/nginx/app/tests/Api/SelfserveLaneCommandApiTest.php
+++ b/services/nginx/app/tests/Api/SelfserveLaneCommandApiTest.php
@@ -64,6 +64,7 @@ it('allows customer self-serve permission to execute START without department ac
         'lane_id' => (int)$scenario['lane']['id'],
         'command' => 'START',
         'license_plate' => (string)$scenario['vehicle']['reg'],
+        'wash_type' => 'Manual',
         'defer_relay_side_effects' => true,
     ], api_fixtures()->bearerHeaders($token));
 
@@ -170,6 +171,7 @@ it('still allows elevated operators with department access to execute lane comma
         'lane_id' => (int)$scenario['lane']['id'],
         'command' => 'START',
         'license_plate' => 'OP' . (int)$scenario['lane']['id'],
+        'wash_type' => 'Manual',
         'defer_relay_side_effects' => true,
     ], $session['headers']);
 
diff --git a/services/nginx/app/tests/Unit/Selfserve/SelfserveLaneStartEntranceTimeoutTest.php b/services/nginx/app/tests/Unit/Selfserve/SelfserveLaneStartEntranceTimeoutTest.php
index e87c5df7..ca37da28 100644
--- a/services/nginx/app/tests/Unit/Selfserve/SelfserveLaneStartEntranceTimeoutTest.php
+++ b/services/nginx/app/tests/Unit/Selfserve/SelfserveLaneStartEntranceTimeoutTest.php
@@ -53,20 +53,23 @@ class SelfserveLaneStartEntranceTimeoutHarness
         $this->relayEvents[] = 'cleaner:on';
     }
 
-    protected function setProgramPickerRelayStatusFromSelectedServiceForWashStart(): void
+    protected function setProgramPickerRelayStatusFromSelectedServiceForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
+        unset($arguments);
         $this->programPickerRelayCalls++;
         $this->relayEvents[] = 'program_picker:selected_service';
     }
 
-    protected function setProgramPickerRelayStatusForWashStart(): void
+    protected function setProgramPickerRelayStatusForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
+        unset($arguments);
         $this->programPickerRelayCalls++;
         $this->relayEvents[] = 'program_picker:eligibility_sync';
     }
 
-    protected function setMachineRelayStatusForWashStart(): void
+    protected function setMachineRelayStatusForWashStart(?selfserve_lane_command_arguments $arguments = null): void
     {
+        unset($arguments);
         $this->machineRelayCalls++;
         $this->relayEvents[] = 'machine:sync';
     }
@@ -107,14 +110,30 @@ it('parses deferred relay side effects on start command arguments', function ():
     $arguments = (new selfserve_lane_command_arguments())->setParameters([
         'license_plate' => 'ab12345',
         'customer_number' => 12345679,
+        'wash_type' => 'Manual',
         'defer_relay_side_effects' => true,
     ]);
 
     expect($arguments->license_plate)->toBe('AB12345');
     expect($arguments->customer_number)->toBe(12345679);
+    expect($arguments->wash_mode)->toBe('manual');
     expect($arguments->defer_relay_side_effects)->toBeTrue();
 });
 
+it('parses wash mode aliases on start command arguments', function (): void {
+    $arguments = (new selfserve_lane_command_arguments())->setParameters([
+        'wash_mode' => 'machine',
+    ]);
+
+    expect($arguments->wash_mode)->toBe('machine');
+});
+
+it('rejects invalid wash types on start command arguments', function (): void {
+    expect(fn() => (new selfserve_lane_command_arguments())->setParameters([
+        'wash_type' => 'automatic',
+    ]))->toThrow(\InvalidArgumentException::class, 'Invalid wash type: automatic');
+});
+
 it('only syncs program picker from selected service when start asks to defer machine side effects', function (): void {
     $lane = new SelfserveLaneStartEntranceTimeoutHarness();
 
diff --git a/services/nginx/app/tests/Unit/Selfserve/SelfserveOpenApiSpecTest.php b/services/nginx/app/tests/Unit/Selfserve/SelfserveOpenApiSpecTest.php
index 3d937789..d6c99b2c 100644
--- a/services/nginx/app/tests/Unit/Selfserve/SelfserveOpenApiSpecTest.php
+++ b/services/nginx/app/tests/Unit/Selfserve/SelfserveOpenApiSpecTest.php
@@ -138,6 +138,8 @@ it('documents property gate lane commands and sanitized gate failure responses',
 
     expect($commandPathBlock)->toContain('OPEN_PROPERTY_ACCESS_GATE');
     expect($commandPathBlock)->toContain('OPEN_PROPERTY_EXIT_GATE');
+    expect($commandPathBlock)->toContain('wash_type:');
+    expect($commandPathBlock)->toContain('wash_mode:');
     expect($commandPathBlock)->toContain('Command execution failed');
     expect($commandPathBlock)->toContain('Failed to execute command: Failed to open property access gate.');
 
diff --git a/services/nginx/app/tests/Unit/Selfserve/SelfserveProgramPickerWashTypeSelectionTest.php b/services/nginx/app/tests/Unit/Selfserve/SelfserveProgramPickerWashTypeSelectionTest.php
index 31aacb01..399caa2b 100644
--- a/services/nginx/app/tests/Unit/Selfserve/SelfserveProgramPickerWashTypeSelectionTest.php
+++ b/services/nginx/app/tests/Unit/Selfserve/SelfserveProgramPickerWashTypeSelectionTest.php
@@ -41,6 +41,8 @@ class SelfserveProgramPickerSelectionHarness
     public object $department_lane;
     public int $licensePlateReads = 0;
     public int $customerNumberReads = 0;
+    public int $availabilityChecks = 0;
+    public bool $machineAvailable = true;
     /** @var array<int,bool> */
     public array $programPickerWrites = [];
     /** @var array<string,mixed> */
@@ -79,29 +81,84 @@ class SelfserveProgramPickerSelectionHarness
         return true;
     }
 
-    public function runDeferredStartRelaySideEffects(): void
+    public function runDeferredStartRelaySideEffects(?string $washType = null): void
     {
-        $arguments = (new selfserve_lane_command_arguments())->setDeferRelaySideEffects(true);
+        $arguments = (new selfserve_lane_command_arguments())
+            ->setDeferRelaySideEffects(true)
+            ->setWashMode($washType);
         $this->runRelaySideEffectsForWashStart($arguments);
     }
+
+    public function runNormalStartProgramPickerRelay(?string $washType = null): void
+    {
+        $arguments = (new selfserve_lane_command_arguments())->setWashMode($washType);
+        $this->setProgramPickerRelayStatusForWashStart($arguments);
+    }
+
+    public function resolveStartWashMode(?string $washType = null): string
+    {
+        $arguments = (new selfserve_lane_command_arguments())->setWashMode($washType);
+        return $this->resolveSelfServeActionWashModeForStart($arguments);
+    }
+
+    protected function isMachineWashSelectedAndAvailableForStart(?selfserve_lane_command_arguments $arguments = null): bool
+    {
+        unset($arguments);
+        $this->availabilityChecks++;
+        return $this->machineAvailable;
+    }
 }
 
 it('turns off the program picker on deferred start when the frontend selected manual wash', function (): void {
     $lane = new SelfserveProgramPickerSelectionHarness();
     $lane->setSelectedServices([]);
 
-    $lane->runDeferredStartRelaySideEffects();
+    $lane->runDeferredStartRelaySideEffects('Manual');
 
     expect($lane->programPickerWrites)->toBe([false]);
 });
 
 it('does not let backend machine eligibility override a frontend manual wash selection', function (): void {
     $lane = new SelfserveProgramPickerSelectionHarness();
-    $lane->setSelectedServices([]);
+    $lane->setSelectedServices(['MACHINE']);
 
-    $lane->runDeferredStartRelaySideEffects();
+    $lane->runDeferredStartRelaySideEffects('Manual');
 
     expect($lane->licensePlateReads)->toBe(0)
         ->and($lane->customerNumberReads)->toBe(0)
-        ->and($lane->programPickerWrites)->toBe([false]);
+        ->and($lane->programPickerWrites)->toBe([false])
+        ->and($lane->resolveStartWashMode('Manual'))->toBe('manual');
+});
+
+it('does not infer program picker enablement from machine service without a customer machine selection', function (): void {
+    $lane = new SelfserveProgramPickerSelectionHarness();
+    $lane->setSelectedServices(['MACHINE']);
+
+    $lane->runDeferredStartRelaySideEffects();
+    $lane->runNormalStartProgramPickerRelay();
+
+    expect($lane->programPickerWrites)->toBe([false, false])
+        ->and($lane->availabilityChecks)->toBe(0);
+});
+
+it('keeps normal start program picker off when the customer selected manual wash', function (): void {
+    $lane = new SelfserveProgramPickerSelectionHarness();
+    $lane->setSelectedServices(['MACHINE']);
+
+    $lane->runNormalStartProgramPickerRelay('Manual');
+
+    expect($lane->programPickerWrites)->toBe([false])
+        ->and($lane->availabilityChecks)->toBe(0);
+});
+
+it('honors a frontend machine wash selection when machine service is selected', function (): void {
+    $lane = new SelfserveProgramPickerSelectionHarness();
+    $lane->setSelectedServices(['MACHINE']);
+
+    $lane->runDeferredStartRelaySideEffects('Machine');
+    $lane->runNormalStartProgramPickerRelay('Machine');
+
+    expect($lane->programPickerWrites)->toBe([true, true])
+        ->and($lane->availabilityChecks)->toBe(1)
+        ->and($lane->resolveStartWashMode('Machine'))->toBe('machine');
 });