fix(gemini): allow system message to be mapped to system prompt

src/Providers/Gemini/Maps/MessageMap.php

@@ -53,23 +53,14 @@ protected function mapMessage(Message $message): void
             UserMessage::class => $this->mapUserMessage($message),
             AssistantMessage::class => $this->mapAssistantMessage($message),
             ToolResultMessage::class => $this->mapToolResultMessage($message),
+            SystemMessage::class => $this->mapSystemMessage($message),
             default => throw new Exception('Could not map message type '.$message::class),
         };
     }
 
     protected function mapSystemMessage(SystemMessage $message): void
     {
-        if (isset($this->contents['system_instruction'])) {
-            throw new PrismException('Gemini only supports one system instruction.');
-        }
-
-        $this->contents['system_instruction'] = [
-            'parts' => [
-                [
-                    'text' => $message->content,
-                ],
-            ],
-        ];
+        $this->contents['system_instruction']['parts'][] = ['text' => $message->content];
     }
 
     protected function mapToolResultMessage(ToolResultMessage $message): void

tests/Fixtures/gemini/generate-text-with-multiple-system-prompts-1.json

@@ -0,0 +1,34 @@
+{
+  "candidates": [
+    {
+      "content": {
+        "parts": [
+          {
+            "text": "I am Prism, a helpful AI assistant created by echo labs.\n"
+          }
+        ],
+        "role": "model"
+      },
+      "finishReason": "STOP",
+      "avgLogprobs": -0.039341066564832418
+    }
+  ],
+  "usageMetadata": {
+    "promptTokenCount": 22,
+    "candidatesTokenCount": 14,
+    "totalTokenCount": 36,
+    "promptTokensDetails": [
+      {
+        "modality": "TEXT",
+        "tokenCount": 22
+      }
+    ],
+    "candidatesTokensDetails": [
+      {
+        "modality": "TEXT",
+        "tokenCount": 14
+      }
+    ]
+  },
+  "modelVersion": "gemini-1.5-flash"
+}

tests/Fixtures/gemini/generate-text-with-system-prompt-from-messages-1.json

@@ -0,0 +1,34 @@
+{
+  "candidates": [
+    {
+      "content": {
+        "parts": [
+          {
+            "text": "I am Prism, a helpful AI assistant created by echo labs.\n"
+          }
+        ],
+        "role": "model"
+      },
+      "finishReason": "STOP",
+      "avgLogprobs": -0.1486046314239502
+    }
+  ],
+  "usageMetadata": {
+    "promptTokenCount": 16,
+    "candidatesTokenCount": 14,
+    "totalTokenCount": 30,
+    "promptTokensDetails": [
+      {
+        "modality": "TEXT",
+        "tokenCount": 16
+      }
+    ],
+    "candidatesTokensDetails": [
+      {
+        "modality": "TEXT",
+        "tokenCount": 14
+      }
+    ]
+  },
+  "modelVersion": "gemini-1.5-flash"
+}