[doc] fix: Fix the role assignment error in the interaction demo file and doc. (#2476)

### What does this PR do?

Fix the role assignment error in the interaction demo file
verl/interactions/gsm8k_interaction.py and doc. The assistant is
expected to solve problems, while users provide problems and feedback
within the messages list.

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### Test

Update tests/interactions/test_gsm8k_interaction.py.

### API and Usage Example

> Demonstrate how the API changes if any, and provide usage example(s)
if possible.

```python
# Add code snippet or script demonstrating how to use this
```

### Design & Code Changes

> Demonstrate the high-level design if this PR is complex, and list the
specific changes.

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---------

Co-authored-by: H <linhaibin.eric@gmail.com>

docs/sglang_multiturn/interaction_system.rst

@@ -180,7 +180,7 @@ The GSM8K interaction demonstrates a complete implementation for math problem-so
             return instance_id
 
         async def generate_response(self, instance_id, messages, **kwargs):
-            # Extract last user message content
+            # Extract last assistant message content
             content = ""
             for item in reversed(messages):
                 if item.get("role") == "assistant":
@@ -299,7 +299,8 @@ Comprehensive testing is essential for interaction systems:
         # Test complete workflow
         instance_id = await interaction.start_interaction(ground_truth="expected_answer")
         
-        messages = [{"role": "user", "content": "user_content"}, {"role": "assistant", "content": "assistant_response"}]
+
+        messages = [{"role": "user", "content": "user_content"}, {"role": "assistant", "content": "assistant_content"}]
         should_terminate, response, reward, metadata = await interaction.generate_response(instance_id, messages)
         
         assert should_terminate in [True, False]

tests/interactions/test_gsm8k_interaction.py

@@ -80,7 +80,7 @@ class TestGsm8kInteraction:
         # Setup instance
         await self.interaction.start_interaction(instance_id=instance_id, ground_truth=ground_truth)
 
-        messages = [{"role": "user", "content": "#### 42"}]
+        messages = [{"role": "assistant", "content": "#### 42"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=1.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -102,7 +102,7 @@ class TestGsm8kInteraction:
         # Setup instance
         await self.interaction.start_interaction(instance_id=instance_id, ground_truth=ground_truth)
 
-        messages = [{"role": "user", "content": "42"}]
+        messages = [{"role": "assistant", "content": "42"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=1.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -123,7 +123,7 @@ class TestGsm8kInteraction:
         # Setup instance
         await self.interaction.start_interaction(instance_id=instance_id, ground_truth=ground_truth)
 
-        messages = [{"role": "user", "content": "24"}]
+        messages = [{"role": "assistant", "content": "24"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=0.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -137,7 +137,7 @@ class TestGsm8kInteraction:
 
     @pytest.mark.asyncio
     async def test_generate_response_multiple_messages(self):
-        """Test generate_response with multiple messages (should use last user message)."""
+        """Test generate_response with multiple messages (should use last assistant message)."""
         instance_id = "test_instance"
         ground_truth = "42"
 
@@ -146,8 +146,9 @@ class TestGsm8kInteraction:
 
         messages = [
             {"role": "user", "content": "What is 2+2?"},
-            {"role": "assistant", "content": "Let me think about this..."},
+            {"role": "assistant", "content": "### 4"},
-            {"role": "user", "content": "#### 42"},
+            {"role": "user", "content": "What is 40+2?"},
+            {"role": "assistant", "content": "#### 42"},
         ]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=1.0):
@@ -160,15 +161,15 @@ class TestGsm8kInteraction:
         assert self.interaction._instance_dict[instance_id]["response"] == "#### 42"
 
     @pytest.mark.asyncio
-    async def test_generate_response_no_user_message(self):
+    async def test_generate_response_no_assistant_message(self):
-        """Test generate_response with no user messages."""
+        """Test generate_response with no assistant messages."""
         instance_id = "test_instance"
         ground_truth = "42"
 
         # Setup instance
         await self.interaction.start_interaction(instance_id=instance_id, ground_truth=ground_truth)
 
-        messages = [{"role": "assistant", "content": "Hello!"}]
+        messages = [{"role": "user", "content": "Hello!"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=0.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -262,7 +263,7 @@ class TestGsm8kInteraction:
         instance_id = await self.interaction.start_interaction(ground_truth=ground_truth)
 
         # Generate response with correct answer
-        messages = [{"role": "user", "content": "42"}]
+        messages = [{"role": "assistant", "content": "42"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=1.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -285,7 +286,7 @@ class TestGsm8kInteraction:
         instance_id = await self.interaction.start_interaction(ground_truth=ground_truth)
 
         # Generate response with incorrect answer
-        messages = [{"role": "user", "content": "24"}]
+        messages = [{"role": "assistant", "content": "24"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=0.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -296,8 +297,8 @@ class TestGsm8kInteraction:
         assert reward == 0.0
 
         # Continue with another attempt
-        messages.append({"role": "assistant", "content": response})
+        messages.append({"role": "user", "content": response})
-        messages.append({"role": "user", "content": "42"})
+        messages.append({"role": "assistant", "content": "42"})
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=1.0):
             should_terminate, response, reward, metadata = await self.interaction.generate_response(
@@ -326,8 +327,8 @@ class TestGsm8kInteraction:
         assert instance_id_2 in self.interaction._instance_dict
 
         # Test responses for both instances
-        messages_1 = [{"role": "user", "content": "42"}]
+        messages_1 = [{"role": "assistant", "content": "42"}]
-        messages_2 = [{"role": "user", "content": "24"}]
+        messages_2 = [{"role": "assistant", "content": "24"}]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", side_effect=[1.0, 1.0]):
             should_terminate_1, _, reward_1, _ = await self.interaction.generate_response(instance_id_1, messages_1)
@@ -374,7 +375,7 @@ class TestGsm8kInteraction:
         await self.interaction.start_interaction(instance_id=instance_id, ground_truth=ground_truth)
 
         messages = [
-            {"role": "user"}  # Missing content field
+            {"role": "assistant"}  # Missing content field
         ]
 
         with patch("verl.utils.reward_score.gsm8k.compute_score", return_value=0.0):

verl/interactions/gsm8k_interaction.py

@@ -31,7 +31,7 @@ class Gsm8kInteraction(BaseInteraction):
     """A demo interaction for calculating the reward of gsm8k.
 
     - `start_interaction`: start a interaction instance for a trajectory.
-    - `generate_response`: generate the response of the user.
+    - `generate_response`: generate the response of the assistant.
     - `calculate_score`: calculate the score of the interaction.
     - `finalize_interaction`: finalize the interaction instance.
     """