docs(prefix.md): add prefix support to docs

docs/my-website/docs/completion/prefix.md

@@ -0,0 +1,119 @@
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+# Pre-fix Assistant Messages
+
+Supported by:
+- Deepseek
+- Mistral
+- Anthropic
+
+```python
+{
+  "role": "assistant", 
+  "content": "..", 
+  ...
+  "prefix": true # 👈 KEY CHANGE
+}
+```
+
+## Quick Start 
+
+<Tabs>
+<TabItem value="sdk" label="SDK">
+
+```python
+from litellm import completion
+import os 
+
+os.environ["DEEPSEEK_API_KEY"] = ""
+
+response = completion(
+  model="deepseek/deepseek-chat",
+  messages=[
+    {"role": "user", "content": "Who won the world cup in 2022?"},
+    {"role": "assistant", "content": "Argentina", "prefix": True}
+  ]
+)
+print(response.choices[0].message.content)
+```
+</TabItem>
+<TabItem value="proxy" label="PROXY">
+
+```bash
+curl http://0.0.0.0:4000/v1/chat/completions \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer $LITELLM_KEY" \
+  -d '{
+    "model": "deepseek/deepseek-chat",
+    "messages": [
+      {
+        "role": "user",
+        "content": "Who won the world cup in 2022?"
+      },
+      {
+        "role": "assistant", 
+        "content": "Argentina", "prefix": true
+      }
+    ]
+}'
+```
+</TabItem>
+</Tabs>
+
+**Expected Response**
+
+```bash
+{
+    "id": "3b66124d79a708e10c603496b363574c",
+    "choices": [
+        {
+            "finish_reason": "stop",
+            "index": 0,
+            "message": {
+                "content": " won the FIFA World Cup in 2022.",
+                "role": "assistant",
+                "tool_calls": null,
+                "function_call": null
+            }
+        }
+    ],
+    "created": 1723323084,
+    "model": "deepseek/deepseek-chat",
+    "object": "chat.completion",
+    "system_fingerprint": "fp_7e0991cad4",
+    "usage": {
+        "completion_tokens": 12,
+        "prompt_tokens": 16,
+        "total_tokens": 28,
+    },
+    "service_tier": null
+}
+```
+
+## Check Model Support 
+
+Call `litellm.get_model_info` to check if a model/provider supports `response_format`. 
+
+<Tabs>
+<TabItem value="sdk" label="SDK">
+
+```python
+from litellm import get_model_info
+
+params = get_model_info(model="deepseek/deepseek-chat")
+
+assert params["supports_assistant_prefill"] is True
+```
+
+</TabItem>
+<TabItem value="proxy" label="PROXY">
+
+Call the `/model/info` endpoint to get a list of models + their supported params.
+
+```bash
+curl -X GET 'http://0.0.0.0:4000/v1/model/info' \
+-H 'Authorization: Bearer $LITELLM_KEY' \
+```
+</TabItem>
+</Tabs>

docs/my-website/sidebars.js

@@ -162,6 +162,7 @@ const sidebars = {
         "completion/input",
         "completion/provider_specific_params",
         "completion/json_mode",
+        "completion/prefix",
         "completion/drop_params",
         "completion/prompt_formatting",
         "completion/output",

litellm/utils.py

@@ -4585,7 +4585,7 @@ def get_llm_provider(
                 api_base = (
                     api_base
                     or get_secret("DEEPSEEK_API_BASE")
-                    or "https://api.deepseek.com/v1"
+                    or "https://api.deepseek.com/beta"
                 )  # type: ignore
                 dynamic_api_key = api_key or get_secret("DEEPSEEK_API_KEY")
             elif custom_llm_provider == "fireworks_ai":