Fill the prompt with as much messages as possible

libertai_agents/libertai_agents/models/base.py

@@ -76,21 +76,37 @@
         )
         raw_messages = [x.model_dump() for x in messages]
 
-        for i in range(len(raw_messages)):
+        prompt = (
+            self.tokenizer.apply_chat_template(
+                conversation=system_messages,
+                tools=[x.args_schema for x in tools],
+                tokenize=False,
+                add_generation_prompt=True,
+            )
+            if len(system_messages) != 0
+            else ""
+        )
+        if self.__count_tokens(prompt) > self.context_length:
+            raise ValueError(
+                f"Can't fit system messages into the available context length ({self.context_length} tokens)"
+            )
+
+        # Adding as many messages as we can fit into the context, starting from the last ones
+        for i in reversed(range(len(raw_messages))):
             included_messages: list = system_messages + raw_messages[i:]
-            prompt = self.tokenizer.apply_chat_template(
+            new_prompt = self.tokenizer.apply_chat_template(
                 conversation=included_messages,
                 tools=[x.args_schema for x in tools],
                 tokenize=False,
                 add_generation_prompt=True,
             )
             if not isinstance(prompt, str):
                 raise TypeError("Generated prompt isn't a string")
-            if self.__count_tokens(prompt) <= self.context_length:
+            if self.__count_tokens(new_prompt) >= self.context_length:
                 return prompt
-        raise ValueError(
-            f"Can't fit messages into the available context length ({self.context_length} tokens)"
-        )
+            prompt = new_prompt
+
+        return prompt
 
     def generate_tool_call_id(self) -> str | None:
         """