fix(ReAct): Change format so that trajectory demos inside history are used using chat format

dspy/predict/react.py

@@ -4,7 +4,9 @@
 from litellm import ContextWindowExceededError
 
 import dspy
+from dspy.adapters.types.history import History
 from dspy.adapters.types.tool import Tool
+from dspy.primitives.example import Example
 from dspy.primitives.module import Module
 from dspy.signatures.signature import ensure_signature
 
@@ -93,6 +95,34 @@ def _format_trajectory(self, trajectory: dict[str, Any]):
         trajectory_signature = dspy.Signature(f"{', '.join(trajectory.keys())} -> x")
         return adapter.format_user_message_content(trajectory_signature, trajectory)
 
+    def _format_history_with_trajectory(self, history: History | None) -> History | None:
+        if history is None or not history.messages:
+            return history
+
+        formatted_messages = []
+        changed = False
+
+        for message in history.messages:
+            if isinstance(message, Example):
+                message_data = dict(message.items())
+            elif isinstance(message, dict):
+                message_data = dict(message)
+            else:
+                formatted_messages.append(message)
+                continue
+
+            trajectory_value = message_data.get("trajectory")
+            if trajectory_value and not isinstance(trajectory_value, str):
+                message_data["trajectory"] = self._format_trajectory(trajectory_value)
+                changed = True
+
+            formatted_messages.append(message_data)
+
+        if not changed:
+            return history
+
+        return History(messages=formatted_messages)
+
     def forward(self, **input_args):
         trajectory = {}
         max_iters = input_args.pop("max_iters", self.max_iters)
@@ -146,21 +176,29 @@ async def aforward(self, **input_args):
     def _call_with_potential_trajectory_truncation(self, module, trajectory, **input_args):
         for _ in range(3):
             try:
-                return module(
-                    **input_args,
-                    trajectory=self._format_trajectory(trajectory),
-                )
+                call_kwargs = dict(input_args)
+                call_kwargs["trajectory"] = self._format_trajectory(trajectory)
+
+                history_value = call_kwargs.get("history")
+                if isinstance(history_value, History):
+                    call_kwargs["history"] = self._format_history_with_trajectory(history_value)
+
+                return module(**call_kwargs)
             except ContextWindowExceededError:
                 logger.warning("Trajectory exceeded the context window, truncating the oldest tool call information.")
                 trajectory = self.truncate_trajectory(trajectory)
 
     async def _async_call_with_potential_trajectory_truncation(self, module, trajectory, **input_args):
         for _ in range(3):
             try:
-                return await module.acall(
-                    **input_args,
-                    trajectory=self._format_trajectory(trajectory),
-                )
+                call_kwargs = dict(input_args)
+                call_kwargs["trajectory"] = self._format_trajectory(trajectory)
+
+                history_value = call_kwargs.get("history")
+                if isinstance(history_value, History):
+                    call_kwargs["history"] = self._format_history_with_trajectory(history_value)
+
+                return await module.acall(**call_kwargs)
             except ContextWindowExceededError:
                 logger.warning("Trajectory exceeded the context window, truncating the oldest tool call information.")
                 trajectory = self.truncate_trajectory(trajectory)

tests/predict/test_react.py

@@ -50,6 +50,73 @@ def make_images():
     assert sum(1 for part in observation_content if isinstance(part, dict) and part.get("type") == "image_url") == 2
 
 
+def test_history_trajectory_uses_chat_format():
+    def math_tool(expression: str) -> str:
+        return str(eval(expression))
+
+    adapter = dspy.ChatAdapter()
+    lm = DummyLM(
+        [
+            {
+                "next_thought": "I should use the math tool.",
+                "next_tool_name": "math_tool",
+                "next_tool_args": {"expression": "2+2"},
+            },
+            {
+                "next_thought": "That answers the question; time to finish.",
+                "next_tool_name": "finish",
+                "next_tool_args": {},
+            },
+            {
+                "reasoning": "Computed 2+2 with the provided tool.",
+                "answer": "4",
+            },
+            {
+                "next_thought": "Reusing the math tool for another calculation.",
+                "next_tool_name": "math_tool",
+                "next_tool_args": {"expression": "3*4"},
+            },
+            {
+                "next_thought": "I have the second result and can finish now.",
+                "next_tool_name": "finish",
+                "next_tool_args": {},
+            },
+            {
+                "reasoning": "Computed 3*4 with the provided tool.",
+                "answer": "12",
+            },
+        ],
+        adapter=adapter,
+    )
+
+    dspy.settings.configure(lm=lm, adapter=adapter)
+
+    class HistorySignature(dspy.Signature):
+        history: dspy.History = dspy.InputField()
+        question: str = dspy.InputField()
+        answer: str = dspy.OutputField()
+
+    react = dspy.ReAct(HistorySignature, tools=[math_tool])
+
+    history = dspy.History(messages=[])
+
+    q1 = "What is 2+2?"
+    first_outputs = react(history=history, question=q1)
+    history.messages.append({"question": q1, **first_outputs})
+
+    q2 = "Now compute 3*4."
+    react(history=history, question=q2)
+
+    messages = lm.history[-1]["messages"]
+    user_messages = [message for message in messages if message.get("role") == "user"]
+    assert len(user_messages) >= 2
+
+    first_user_content = user_messages[0]["content"]
+    assert "[[ ## trajectory ## ]]" in first_user_content
+    assert "[[ ## thought_0 ## ]]" in first_user_content
+    assert '"thought_0"' not in first_user_content
+
+
 def test_tool_calling_with_pydantic_args():
     class CalendarEvent(BaseModel):
         name: str