feat(gemini): add service_tier support for Flex Inference

src/Providers/Gemini/Handlers/Stream.php

@@ -507,6 +507,7 @@ protected function sendRequest(Request $request): Response
                     'tools' => $tools !== [] ? $tools : null,
                     'tool_config' => $request->toolChoice() ? ToolChoiceMap::map($request->toolChoice()) : null,
                     'safetySettings' => $providerOptions['safetySettings'] ?? null,
+                    'service_tier' => $providerOptions['serviceTier'] ?? null,
                 ])
             );
 

src/Providers/Gemini/Handlers/Structured.php

@@ -137,6 +137,7 @@ public function sendRequest(Request $request): array
                 'tools' => $tools !== [] ? $tools : null,
                 'tool_config' => $request->toolChoice() ? ToolChoiceMap::map($request->toolChoice()) : null,
                 'safetySettings' => $providerOptions['safetySettings'] ?? null,
+                'service_tier' => $providerOptions['serviceTier'] ?? null,
             ])
         );
 

src/Providers/Gemini/Handlers/Text.php

@@ -119,6 +119,7 @@ protected function sendRequest(Request $request): ClientResponse
                 'tools' => $tools !== [] ? $tools : null,
                 'tool_config' => $request->toolChoice() ? ToolChoiceMap::map($request->toolChoice()) : null,
                 'safetySettings' => $providerOptions['safetySettings'] ?? null,
+                'service_tier' => $providerOptions['serviceTier'] ?? null,
             ])
         );
 

tests/Providers/Gemini/GeminiStreamTest.php

@@ -440,3 +440,27 @@
     expect($toolCalls[1]->reasoningId)->not->toBeNull();
     expect($toolCalls[0]->reasoningId)->toBe($toolCalls[1]->reasoningId);
 });
+
+it('passes service_tier in the request body for streaming', function (): void {
+    FixtureResponse::fakeResponseSequence('*', 'gemini/stream-basic-text');
+
+    $response = Prism::text()
+        ->using(Provider::Gemini, 'gemini-2.5-flash')
+        ->withPrompt('Summarize this document.')
+        ->withProviderOptions(['serviceTier' => 'flex'])
+        ->asStream();
+
+    // Consume the stream
+    foreach ($response as $event) {
+        //
+    }
+
+    Http::assertSent(function (Request $request): true {
+        $data = $request->data();
+
+        expect($data)->toHaveKey('service_tier')
+            ->and($data['service_tier'])->toBe('flex');
+
+        return true;
+    });
+});

tests/Providers/Gemini/GeminiStructuredTest.php

@@ -404,3 +404,32 @@
     expect($response->steps[0]->additionalContent['thoughtSummaries'])->toBeArray();
     expect($response->steps[0]->additionalContent['thoughtSummaries'][0])->toContain('Let me think about');
 });
+
+it('passes service_tier in the request body for structured output', function (): void {
+    FixtureResponse::fakeResponseSequence('*', 'gemini/generate-structured');
+
+    $schema = new ObjectSchema(
+        'output',
+        'the output object',
+        [
+            new StringSchema('weather', 'The weather forecast'),
+        ],
+        ['weather']
+    );
+
+    Prism::structured()
+        ->using(Provider::Gemini, 'gemini-2.5-flash')
+        ->withSchema($schema)
+        ->withPrompt('What is the weather?')
+        ->withProviderOptions(['serviceTier' => 'flex'])
+        ->asStructured();
+
+    Http::assertSent(function (Request $request): true {
+        $data = $request->data();
+
+        expect($data)->toHaveKey('service_tier')
+            ->and($data['service_tier'])->toBe('flex');
+
+        return true;
+    });
+});

tests/Providers/Gemini/GeminiTextTest.php

@@ -620,3 +620,41 @@ function (Request $request): bool {
         });
     });
 });
+
+describe('Flex Inference for Gemini', function (): void {
+    it('passes service_tier in the request body', function (): void {
+        FixtureResponse::fakeResponseSequence('*', 'gemini/generate-text-with-a-prompt');
+
+        Prism::text()
+            ->using(Provider::Gemini, 'gemini-2.5-flash')
+            ->withPrompt('Summarize this document.')
+            ->withProviderOptions(['serviceTier' => 'flex'])
+            ->asText();
+
+        Http::assertSent(function (Request $request): true {
+            $data = $request->data();
+
+            expect($data)->toHaveKey('service_tier')
+                ->and($data['service_tier'])->toBe('flex');
+
+            return true;
+        });
+    });
+
+    it('does not include service_tier when not set', function (): void {
+        FixtureResponse::fakeResponseSequence('*', 'gemini/generate-text-with-a-prompt');
+
+        Prism::text()
+            ->using(Provider::Gemini, 'gemini-2.5-flash')
+            ->withPrompt('Hello')
+            ->asText();
+
+        Http::assertSent(function (Request $request): true {
+            $data = $request->data();
+
+            expect($data)->not->toHaveKey('service_tier');
+
+            return true;
+        });
+    });
+});