fix(anthropic): set default max tokens (#816)

Author: sixlive

src/Providers/Anthropic/Handlers/Structured.php

@@ -98,7 +98,7 @@ public static function buildHttpRequestPayload(PrismRequest $request): array
                         : config('prism.anthropic.default_thinking_budget', 1024),
                 ]
                 : null,
-            'max_tokens' => $request->maxTokens(),
+            'max_tokens' => $request->maxTokens() ?? 64000,
             'temperature' => $request->temperature(),
             'top_p' => $request->topP(),
             'mcp_servers' => $request->providerOptions('mcp_servers'),

src/Providers/Anthropic/Handlers/Text.php

@@ -90,7 +90,7 @@ public static function buildHttpRequestPayload(PrismRequest $request): array
                         : config('prism.anthropic.default_thinking_budget', 1024),
                 ]
                 : null,
-            'max_tokens' => $request->maxTokens(),
+            'max_tokens' => $request->maxTokens() ?? 64000,
             'temperature' => $request->temperature(),
             'top_p' => $request->topP(),
             'tools' => static::buildTools($request) ?: null,

tests/Providers/Anthropic/AnthropicStructuredRequestTest.php

@@ -319,3 +319,34 @@
         return true;
     });
 });
+
+it('always includes max_tokens in payload because it is required by anthropic', function (): void {
+    FixtureResponse::fakeResponseSequence('v1/messages', 'anthropic/structured');
+
+    $schema = new ObjectSchema(
+        'simple',
+        'Simple object',
+        [
+            'data' => new StringSchema('data', 'Some data'),
+        ],
+        ['data']
+    );
+
+    // Note: NOT calling withMaxTokens() - simulating user not setting it
+    Prism::structured()
+        ->using(Provider::Anthropic, 'claude-3-5-haiku-latest')
+        ->withMessages([new UserMessage('Generate simple data')])
+        ->withSchema($schema)
+        ->asStructured();
+
+    Http::assertSent(function (Request $request): bool {
+        $payload = $request->data();
+
+        // Anthropic API requires max_tokens - it should always be present
+        expect($payload)->toHaveKey('max_tokens');
+        expect($payload['max_tokens'])->toBeInt();
+        expect($payload['max_tokens'])->toBeGreaterThan(0);
+
+        return true;
+    });
+});

tests/Providers/Anthropic/AnthropicTextRequestTest.php

@@ -241,6 +241,26 @@
     });
 });
 
+it('always includes max_tokens in payload because it is required by anthropic', function (): void {
+    FixtureResponse::fakeResponseSequence('v1/messages', 'anthropic/generate-text-with-a-prompt');
+
+    Prism::text()
+        ->using(Provider::Anthropic, 'claude-3-5-haiku-latest')
+        ->withMessages([new UserMessage('Test')])
+        ->asText();
+
+    Http::assertSent(function (Request $request): bool {
+        $payload = $request->data();
+
+        // Anthropic API requires max_tokens - it should always be present
+        expect($payload)->toHaveKey('max_tokens');
+        expect($payload['max_tokens'])->toBeInt();
+        expect($payload['max_tokens'])->toBeGreaterThan(0);
+
+        return true;
+    });
+});
+
 it('can send images from file', function (): void {
     FixtureResponse::fakeResponseSequence('v1/messages', 'anthropic/generate-text-with-image');