Add OpenRouter provider support to auto_client routing

- Add 'openrouter' to supported_providers list
- Implement OpenRouter routing logic following DeepSeek pattern
- Use OpenAI-compatible API with https://openrouter.ai/api/v1 base URL
- Default to Mode.TOOLS with support for OPENROUTER_STRUCTURED_OUTPUTS and JSON modes
- Handle OPENROUTER_API_KEY from environment or kwargs

Co-Authored-By: Jason Liu <jason@jxnl.co>

Author: devin-ai-integration[bot]

instructor/auto_client.py

@@ -31,6 +31,7 @@
     "deepseek",
     "fireworks",
     "ollama",
+    "openrouter",
     "xai",
     "litellm",
 ]
@@ -946,6 +947,60 @@ def from_provider(
             )
             raise
 
+    elif provider == "openrouter":
+        try:
+            import openai
+            from instructor import from_openai
+            import os
+
+            # Get API key from kwargs or environment
+            api_key = api_key or os.environ.get("OPENROUTER_API_KEY")
+
+            if not api_key:
+                from .core.exceptions import ConfigurationError
+
+                raise ConfigurationError(
+                    "OPENROUTER_API_KEY is not set. "
+                    "Set it with `export OPENROUTER_API_KEY=<your-api-key>` or pass it as kwarg api_key=<your-api-key>"
+                )
+
+            # OpenRouter uses OpenAI-compatible API
+            base_url = kwargs.pop("base_url", "https://openrouter.ai/api/v1")
+
+            client = (
+                openai.AsyncOpenAI(api_key=api_key, base_url=base_url)
+                if async_client
+                else openai.OpenAI(api_key=api_key, base_url=base_url)
+            )
+
+            result = from_openai(
+                client,
+                model=model_name,
+                mode=mode if mode else instructor.Mode.TOOLS,
+                **kwargs,
+            )
+            logger.info(
+                "Client initialized",
+                extra={**provider_info, "status": "success"},
+            )
+            return result
+        except ImportError:
+            from .core.exceptions import ConfigurationError
+
+            raise ConfigurationError(
+                "The openai package is required to use the OpenRouter provider. "
+                "Install it with `pip install openai`."
+            ) from None
+        except Exception as e:
+            logger.error(
+                "Error initializing %s client: %s",
+                provider,
+                e,
+                exc_info=True,
+                extra={**provider_info, "status": "error"},
+            )
+            raise
+
     elif provider == "litellm":
         try:
             from litellm import completion, acompletion