diff --git a/atroposlib/envs/server_handling/managed_server.py b/atroposlib/envs/server_handling/managed_server.py
new file mode 100644
index 00000000..2740afea
--- /dev/null
+++ b/atroposlib/envs/server_handling/managed_server.py
@@ -0,0 +1,511 @@
+"""
+Managed server wrapper that tracks text sequences with aligned tokens and logprobs.
+
+This wrapper maintains a tree structure of sequences, where:
+- Each node represents a complete text sequence (prompt + completion)
+- Tokens and logprobs are tracked with proper masking for training
+- Branching occurs organically from different contexts and n > 1 completions
+"""
+
+import time
+import uuid
+import warnings
+from typing import Any, Dict, List, Optional, Union
+
+from openai.types.chat.chat_completion import (
+    ChatCompletion,
+    ChatCompletionMessage,
+    Choice,
+)
+from openai.types.completion import Completion, CompletionChoice
+from pydantic import BaseModel
+
+from atroposlib.envs.server_handling.server_baseline import APIServer
+
+
+class SequenceNode(BaseModel):
+    """
+    A node in the sequence tree representing a complete text sequence.
+
+    Attributes:
+        full_text: Complete text (prompt + completion)
+        tokens: Full token sequence (actual token IDs)
+        masked_tokens: Tokens with -100 for prompt positions, actual IDs for completion
+        logprobs: Logprobs with 0.0 for prompt positions, actual values for completion
+        metadata: Optional metadata (e.g., role information, finish_reason, etc.)
+    """
+
+    full_text: str
+    tokens: List[int]
+    masked_tokens: List[int]
+    logprobs: List[float]
+    metadata: Optional[Dict[str, Any]] = None
+
+
+class ManagedServer:
+    """
+    Wrapper around APIServer that tracks sequences with aligned tokens and logprobs.
+
+    Maintains a tree structure keyed by input text, where each completion creates
+    new branches. Provides proper masking for training (prompt tokens masked with -100,
+    logprobs set to 0.0).
+
+    Uses the clean _tokens_and_logprobs_completion_wrapper interface internally.
+    """
+
+    def __init__(
+        self,
+        server: APIServer,
+        tokenizer: Optional[Any] = None,
+        track_tree: bool = False,
+    ):
+        """
+        Initialize the managed server.
+
+        Args:
+            server: The underlying APIServer instance to wrap
+            tokenizer: Optional tokenizer for encoding/decoding. If not provided,
+                      will attempt to extract from server or create from model name.
+            track_tree: If True, maintains a tree structure with parent-child links
+                       (for multi-turn RL with per-step advantages). If False (default),
+                       maintains a simple list of current nodes that updates in-place.
+        """
+        self.server = server
+        self.tokenizer = tokenizer
+        self.track_tree = track_tree
+
+        # Initialize storage based on mode
+        if track_tree:
+            self.sequences: Dict[str, SequenceNode] = {}  # Tree mode: dict lookup
+        else:
+            self.current_nodes: List[SequenceNode] = []  # Default mode: simple list
+
+        # Try to get tokenizer from server if not provided
+        if self.tokenizer is None:
+            self._initialize_tokenizer()
+
+    def _initialize_tokenizer(self):
+        """Initialize tokenizer from server or model name."""
+        # Check if the wrapped server has a tokenizer
+        if hasattr(self.server, "tokenizer"):
+            self.tokenizer = self.server.tokenizer
+        else:
+            # Try to create from model name
+            try:
+                from transformers import AutoTokenizer
+
+                model_name = self.server.config.model_name
+                self.tokenizer = AutoTokenizer.from_pretrained(model_name)
+            except Exception as e:
+                warnings.warn(
+                    f"Could not initialize tokenizer: {e}. "
+                    "Sequence tracking will be limited without tokenizer."
+                )
+                self.tokenizer = None
+
+    def _convert_messages_to_prompt(self, messages: List[Dict[str, str]]) -> str:
+        """
+        Convert chat messages to prompt text using tokenizer's chat template.
+
+        Args:
+            messages: List of message dicts with 'role' and 'content'
+
+        Returns:
+            Formatted prompt string
+        """
+        if self.tokenizer is None:
+            # Fallback: simple concatenation
+            return "\n".join([f"{m['role']}: {m['content']}" for m in messages])
+
+        if hasattr(self.tokenizer, "apply_chat_template"):
+            # Only add generation prompt if last message is not from assistant
+            add_generation_prompt = (
+                len(messages) == 0 or messages[-1].get("role") != "assistant"
+            )
+
+            # Use the tokenizer's chat template
+            return self.tokenizer.apply_chat_template(
+                messages, tokenize=False, add_generation_prompt=add_generation_prompt
+            )
+        else:
+            # Fallback for tokenizers without chat template
+            return "\n".join([f"{m['role']}: {m['content']}" for m in messages])
+
+    def _find_extending_node(self, input_text: str) -> Optional[SequenceNode]:
+        """
+        Find a node that this input extends (default mode).
+
+        Args:
+            input_text: The input text to check
+
+        Returns:
+            The node that input_text extends, or None if no match
+        """
+        if not self.current_nodes:
+            return None
+
+        # Check if any current node's full_text is a prefix of the input
+        # This means the input is extending that node
+        for node in self.current_nodes:
+            if input_text.startswith(node.full_text):
+                return node
+        return None
+
+    def _compute_input_ids(
+        self, input_text: str, extending_node: Optional[SequenceNode]
+    ) -> List[int]:
+        """
+        Compute input_ids for the prompt, using existing tokens if extending.
+
+        Args:
+            input_text: The full input prompt text
+            extending_node: Node being extended, if any
+
+        Returns:
+            List of token IDs to use as input_ids
+        """
+        if extending_node is not None:
+            # Extending an existing sequence - use its tokens + tokenize the new part
+            existing_text = extending_node.full_text
+            new_text_suffix = input_text[len(existing_text) :]
+
+            # Tokenize only the new suffix (without BOS since we're continuing)
+            if new_text_suffix:
+                new_tokens = self.tokenizer.encode(
+                    new_text_suffix, add_special_tokens=False
+                )
+                return extending_node.tokens + new_tokens
+            else:
+                # No new text, just use existing tokens
+                return extending_node.tokens.copy()
+        else:
+            # New sequence - tokenize the whole thing
+            return self.tokenizer.encode(input_text, add_special_tokens=True)
+
+    def _find_parent_node(self, input_text: str) -> Optional[SequenceNode]:
+        """
+        Find a parent node whose full_text matches the input_text (tree mode).
+
+        Args:
+            input_text: The input text to search for
+
+        Returns:
+            Parent SequenceNode if found, None otherwise
+        """
+        return self.sequences.get(input_text, None)
+
+    def _create_sequence_node(
+        self,
+        input_text: str,
+        parent_node: Optional[SequenceNode],
+        prompt_tokens: List[int],
+        output_tokens: List[int],
+        output_logprobs: List[float],
+        completion_text: str,
+        finish_reason: str = "stop",
+    ) -> SequenceNode:
+        """
+        Create a sequence node with proper masking.
+
+        Args:
+            input_text: The input prompt text
+            parent_node: Parent node to extend from (if available)
+            prompt_tokens: Token IDs for the prompt
+            output_tokens: Token IDs for the output/completion
+            output_logprobs: Logprobs for output tokens
+            completion_text: The completion text
+            finish_reason: Finish reason from server
+
+        Returns:
+            SequenceNode with properly masked tokens and logprobs
+        """
+        # Combine text
+        full_text = input_text + completion_text
+
+        # If we have a parent node, we should use its tokens as the prompt base
+        if parent_node is not None:
+            # Use parent's full tokens as the prompt
+            prompt_tokens = parent_node.tokens.copy()
+
+        # Combine tokens
+        full_tokens = prompt_tokens + output_tokens
+        prompt_len = len(prompt_tokens)
+
+        # Create masked tokens: -100 for prompt, actual IDs for completion
+        masked_tokens = [-100] * prompt_len + output_tokens
+
+        # Create masked logprobs: 0.0 for prompt, actual for completion
+        # Pad logprobs to match token length if needed
+        if len(output_logprobs) < len(output_tokens):
+            output_logprobs = output_logprobs + [0.0] * (
+                len(output_tokens) - len(output_logprobs)
+            )
+        elif len(output_logprobs) > len(output_tokens):
+            output_logprobs = output_logprobs[: len(output_tokens)]
+
+        full_logprobs = [0.0] * prompt_len + output_logprobs
+
+        return SequenceNode(
+            full_text=full_text,
+            tokens=full_tokens,
+            masked_tokens=masked_tokens,
+            logprobs=full_logprobs,
+            metadata={"finish_reason": finish_reason},
+        )
+
+    async def chat_completion(self, **kwargs) -> ChatCompletion:
+        """
+        Intercept chat completion call and track sequences.
+
+        Internally converts to prompt, calls tokens_and_logprobs_completion,
+        tracks the sequence, and reconstructs a ChatCompletion response.
+
+        Args:
+            **kwargs: Standard chat completion kwargs (messages, n, etc.)
+
+        Returns:
+            ChatCompletion response
+        """
+        # Get input text
+        messages = kwargs.get("messages", [])
+        prompt = self._convert_messages_to_prompt(messages)
+
+        # Handle parent node and extending logic based on mode
+        if self.track_tree:
+            # Tree mode: look up parent in dict
+            parent_node = self._find_parent_node(prompt)
+            extending_node = None
+        else:
+            # Default mode: check if extending existing sequence
+            extending_node = self._find_extending_node(prompt)
+            parent_node = None  # Don't use parent merging in default mode
+
+        # Convert to completion format
+        completion_kwargs = kwargs.copy()
+        completion_kwargs["prompt"] = prompt
+        completion_kwargs.pop("messages", None)
+
+        # Set model name if not provided
+        if "model" not in completion_kwargs:
+            completion_kwargs["model"] = self.server.config.model_name
+
+        # Compute input_ids (using existing tokens if extending)
+        if not self.track_tree and self.tokenizer is not None:
+            input_ids = self._compute_input_ids(prompt, extending_node)
+            completion_kwargs["input_ids"] = input_ids
+
+        # Call the tokens and logprobs wrapper directly
+        (
+            prompt_tokens,
+            output_tokens_list,
+            output_logprobs_list,
+            finish_reasons,
+        ) = await self.server._tokens_and_logprobs_completion_wrapper(
+            **completion_kwargs
+        )
+
+        # Track each completion and build choices
+        n = len(output_tokens_list)
+        choices = []
+
+        for i in range(n):
+            output_tokens = output_tokens_list[i]
+            output_logprobs = output_logprobs_list[i]
+            finish_reason_raw = finish_reasons[i] if i < len(finish_reasons) else "stop"
+
+            # Extract finish_reason string from dict if needed
+            if isinstance(finish_reason_raw, dict):
+                finish_reason = finish_reason_raw.get("type", "stop")
+            else:
+                finish_reason = finish_reason_raw
+
+            # Decode completion text
+            if self.tokenizer is not None:
+                completion_text = self.tokenizer.decode(
+                    output_tokens, skip_special_tokens=True
+                )
+            else:
+                completion_text = "".join([chr(t) for t in output_tokens if t > 31])
+
+            # Create and store sequence node
+            node = self._create_sequence_node(
+                input_text=prompt,
+                parent_node=parent_node,
+                prompt_tokens=prompt_tokens,
+                output_tokens=output_tokens,
+                output_logprobs=output_logprobs,
+                completion_text=completion_text,
+                finish_reason=finish_reason,
+            )
+
+            # Store node based on mode
+            if self.track_tree:
+                # Tree mode: key by full text in dict
+                self.sequences[node.full_text] = node
+            else:
+                # Default mode: replace if extending, append if new context
+                if extending_node is not None:
+                    # Replace the extending node with the new extended version
+                    try:
+                        idx = self.current_nodes.index(extending_node)
+                        self.current_nodes[idx] = node
+                    except ValueError:
+                        # Extending node not in list anymore, just append
+                        self.current_nodes.append(node)
+                else:
+                    # New context - append to list
+                    self.current_nodes.append(node)
+
+            # Build choice
+            choice = Choice(
+                finish_reason=finish_reason,
+                index=i,
+                message=ChatCompletionMessage(content=completion_text, role="assistant"),
+            )
+            choices.append(choice)
+
+        # Construct ChatCompletion response
+        return ChatCompletion(
+            id=str(uuid.uuid4()),
+            created=int(time.time()),
+            model=self.server.config.model_name,
+            object="chat.completion",
+            choices=choices,
+        )
+
+    async def completion(self, **kwargs) -> Completion:
+        """
+        Intercept completion call and track sequences.
+
+        Uses tokens_and_logprobs_completion internally, tracks the sequence,
+        and reconstructs a Completion response.
+
+        Args:
+            **kwargs: Standard completion kwargs (prompt, n, etc.)
+
+        Returns:
+            Completion response
+        """
+        # Get input text
+        prompt = kwargs.get("prompt", "")
+
+        # Handle parent node and extending logic based on mode
+        if self.track_tree:
+            # Tree mode: look up parent in dict
+            parent_node = self._find_parent_node(prompt)
+            extending_node = None
+        else:
+            # Default mode: check if extending existing sequence
+            extending_node = self._find_extending_node(prompt)
+            parent_node = None  # Don't use parent merging in default mode
+
+        # Set model name if not provided
+        if "model" not in kwargs:
+            kwargs["model"] = self.server.config.model_name
+
+        # Compute input_ids (using existing tokens if extending)
+        if not self.track_tree and self.tokenizer is not None:
+            input_ids = self._compute_input_ids(prompt, extending_node)
+            kwargs["input_ids"] = input_ids
+
+        # Call the tokens and logprobs wrapper directly
+        (
+            prompt_tokens,
+            output_tokens_list,
+            output_logprobs_list,
+            finish_reasons,
+        ) = await self.server._tokens_and_logprobs_completion_wrapper(**kwargs)
+
+        # Track each completion and build choices
+        n = len(output_tokens_list)
+        choices = []
+
+        for i in range(n):
+            output_tokens = output_tokens_list[i]
+            output_logprobs = output_logprobs_list[i]
+            finish_reason_raw = finish_reasons[i] if i < len(finish_reasons) else "stop"
+
+            # Extract finish_reason string from dict if needed
+            if isinstance(finish_reason_raw, dict):
+                finish_reason = finish_reason_raw.get("type", "stop")
+            else:
+                finish_reason = finish_reason_raw
+
+            # Decode completion text
+            if self.tokenizer is not None:
+                completion_text = self.tokenizer.decode(
+                    output_tokens, skip_special_tokens=True
+                )
+            else:
+                completion_text = "".join([chr(t) for t in output_tokens if t > 31])
+
+            # Create and store sequence node
+            node = self._create_sequence_node(
+                input_text=prompt,
+                parent_node=parent_node,
+                prompt_tokens=prompt_tokens,
+                output_tokens=output_tokens,
+                output_logprobs=output_logprobs,
+                completion_text=completion_text,
+                finish_reason=finish_reason,
+            )
+
+            # Store node based on mode
+            if self.track_tree:
+                # Tree mode: key by full text in dict
+                self.sequences[node.full_text] = node
+            else:
+                # Default mode: replace if extending, append if new context
+                if extending_node is not None:
+                    # Replace the extending node with the new extended version
+                    try:
+                        idx = self.current_nodes.index(extending_node)
+                        self.current_nodes[idx] = node
+                    except ValueError:
+                        # Extending node not in list anymore, just append
+                        self.current_nodes.append(node)
+                else:
+                    # New context - append to list
+                    self.current_nodes.append(node)
+
+            # Build choice
+            choice = CompletionChoice(
+                finish_reason=finish_reason, index=i, text=completion_text
+            )
+            choices.append(choice)
+
+        # Construct Completion response
+        return Completion(
+            id=str(uuid.uuid4()),
+            created=int(time.time()),
+            model=self.server.config.model_name,
+            object="text_completion",
+            choices=choices,
+        )
+
+    def get_state(self) -> Dict[str, Any]:
+        """
+        Get the current state of tracked sequences.
+
+        Returns:
+            For default mode (track_tree=False):
+                Dictionary with 'nodes': List[SequenceNode] - ready for training
+            For tree mode (track_tree=True):
+                Dictionary with 'sequences': Dict[str, SequenceNode] and 'tree' alias
+        """
+        if self.track_tree:
+            return {
+                "sequences": self.sequences.copy(),
+                "tree": self.sequences.copy(),  # Alias for compatibility
+            }
+        else:
+            return {
+                "nodes": self.current_nodes.copy(),  # Return a copy so reset() doesn't affect it
+            }
+
+    def reset(self):
+        """Clear all tracked sequences."""
+        if self.track_tree:
+            self.sequences.clear()
+        else:
+            self.current_nodes.clear()
diff --git a/atroposlib/envs/server_handling/server_harness.py b/atroposlib/envs/server_handling/server_harness.py
index b0807d98..af004d02 100644
--- a/atroposlib/envs/server_handling/server_harness.py
+++ b/atroposlib/envs/server_handling/server_harness.py
@@ -87,6 +87,7 @@ def create_completion(
 class ServerHarness:
     def __init__(self):
         self.response_map = dict()
+        self.tokens_and_logprobs_map = dict()  # Map for tokens/logprobs responses
         self.sem = asyncio.Semaphore(1)
         self.eval_sem = asyncio.Semaphore(1)
         pass
@@ -110,6 +111,31 @@ class ServerHarness:
     def set_desired_completion(self, input_message: str, completion: Completion):
         self.response_map[input_message] = completion
 
+    def set_tokens_and_logprobs_response(
+        self,
+        prompt: str,
+        prompt_tokens: list,
+        output_tokens_list: list,
+        output_logprobs_list: list,
+        finish_reasons: list,
+    ):
+        """
+        Set expected response for _tokens_and_logprobs_completion_wrapper.
+
+        Args:
+            prompt: The prompt string (key)
+            prompt_tokens: List of prompt token IDs
+            output_tokens_list: List of lists of output token IDs (one per completion)
+            output_logprobs_list: List of lists of output logprobs (one per completion)
+            finish_reasons: List of finish reasons (one per completion)
+        """
+        self.tokens_and_logprobs_map[prompt] = (
+            prompt_tokens,
+            output_tokens_list,
+            output_logprobs_list,
+            finish_reasons,
+        )
+
     async def chat_completion(self, *args, **kwargs) -> ChatCompletion:
         messages = kwargs.get("messages")
         dictkey = self.conv_to_dictkey(messages)
@@ -125,6 +151,21 @@ class ServerHarness:
         except KeyError as e:
             raise KeyError(f"KeyError: {e} for key:\n{prompt}")
 
+    async def _tokens_and_logprobs_completion_wrapper(
+        self, **kwargs
+    ) -> tuple[list, list, list, list]:
+        """
+        Mock implementation of tokens and logprobs completion wrapper.
+
+        Returns:
+            Tuple of (prompt_tokens, output_tokens_list, output_logprobs_list, finish_reasons)
+        """
+        prompt = kwargs.get("prompt")
+        try:
+            return self.tokens_and_logprobs_map.get(prompt)
+        except KeyError as e:
+            raise KeyError(f"KeyError: {e} for prompt:\n{prompt}")
+
 
 if __name__ == "__main__":
 
diff --git a/atroposlib/envs/server_handling/server_manager.py b/atroposlib/envs/server_handling/server_manager.py
index 41ed3bf5..d2c89ab8 100644
--- a/atroposlib/envs/server_handling/server_manager.py
+++ b/atroposlib/envs/server_handling/server_manager.py
@@ -8,6 +8,7 @@ from openai.types.chat.chat_completion import ChatCompletion
 from openai.types.completion import Completion
 from pydantic import BaseModel, Field
 
+from atroposlib.envs.server_handling.managed_server import ManagedServer
 from atroposlib.envs.server_handling.openai_server import OpenAIServer
 from atroposlib.envs.server_handling.server_baseline import (
     APIServer,
@@ -308,3 +309,50 @@ class ServerManager:
                 yield self.servers[most_available_server]
             finally:
                 pass
+
+    @asynccontextmanager
+    async def managed_server(
+        self, tokenizer=None
+    ) -> AsyncGenerator[ManagedServer, None]:
+        """
+        Context manager that provides a ManagedServer instance.
+
+        The ManagedServer wraps the most available server and tracks text sequences
+        with aligned tokens and logprobs. State is automatically cleared on exit.
+
+        Args:
+            tokenizer: Optional tokenizer to use. If not provided, will attempt to
+                      extract from server or create from model name.
+
+        Yields:
+            ManagedServer instance wrapping the selected server
+
+        Example:
+            async with server_manager.managed_server() as managed:
+                response = await managed.chat_completion(
+                    messages=[{"role": "user", "content": "Hello"}],
+                    n=2
+                )
+                state = managed.get_state()
+                # Process state...
+                # State is automatically cleared when exiting context
+        """
+        most_available_server = 0
+        most_available_server_num_slots = -1
+        for i, server in enumerate(self.servers):
+            if not server.server_healthy:
+                continue
+            if server.sem._value > most_available_server_num_slots:
+                most_available_server = i
+                most_available_server_num_slots = server.sem._value
+
+        # Create ManagedServer wrapping the selected server
+        managed = ManagedServer(
+            server=self.servers[most_available_server], tokenizer=tokenizer
+        )
+
+        try:
+            yield managed
+        finally:
+            # Clean up: reset tracked sequences
+            managed.reset()
diff --git a/atroposlib/envs/server_handling/sglang_server.py b/atroposlib/envs/server_handling/sglang_server.py
index 1a2f1362..1e838374 100644
--- a/atroposlib/envs/server_handling/sglang_server.py
+++ b/atroposlib/envs/server_handling/sglang_server.py
@@ -148,14 +148,24 @@ class SGLangServer(APIServer):
             kwargs.get("model", None) is not None
         ), "Model is required for completion!"
         assert (
-            kwargs.get("prompt", None) is not None
-        ), "Prompt is required for completion!"
+            kwargs.get("prompt", None) is not None or kwargs.get("input_ids", None) is not None
+        ), "Prompt or input_ids is required for completion!"
 
         # Get n parameter for number of completions
         n = kwargs.get("n", 1)
-        prompt_tokens = self.tokenizer.encode(kwargs.pop("prompt"))
+
+        # Use input_ids if provided (from ManagedServer), otherwise tokenize prompt
+        if "input_ids" in kwargs:
+            prompt_tokens = kwargs.pop("input_ids")
+            kwargs.pop("prompt", None)  # Remove prompt if it exists
+        else:
+            prompt_tokens = self.tokenizer.encode(kwargs.pop("prompt"))
+
         # Check for double BOS token, can happen if you use chat templates and forget that they insert a BOS token
-        if prompt_tokens[0] == self.tokenizer.bos_token_id == prompt_tokens[1]:
+        if (
+            len(prompt_tokens) >= 2
+            and prompt_tokens[0] == self.tokenizer.bos_token_id == prompt_tokens[1]
+        ):
             prompt_tokens = prompt_tokens[1:]
         if "max_tokens" in kwargs:
             kwargs["max_new_tokens"] = kwargs.pop("max_tokens")
diff --git a/atroposlib/tests/test_managed_server.py b/atroposlib/tests/test_managed_server.py
new file mode 100644
index 00000000..b8a14046
--- /dev/null
+++ b/atroposlib/tests/test_managed_server.py
@@ -0,0 +1,498 @@
+"""Tests for ManagedServer tracking of sequences with tokens and logprobs."""
+
+import pytest
+
+from atroposlib.envs.server_handling.managed_server import ManagedServer
+from atroposlib.envs.server_handling.server_harness import ServerHarness
+
+
+class MockTokenizer:
+    """Mock tokenizer for testing."""
+
+    def __init__(self):
+        self.eos_token_id = 2
+        self.bos_token_id = 1
+
+    def encode(self, text, add_special_tokens=True):
+        """Simple character-based encoding for testing."""
+        tokens = [ord(c) for c in text]
+        if add_special_tokens:
+            tokens = [self.bos_token_id] + tokens
+        return tokens
+
+    def decode(self, tokens, skip_special_tokens=False):
+        """Simple character-based decoding for testing."""
+        if skip_special_tokens:
+            # Filter out special tokens
+            tokens = [
+                t for t in tokens if t not in [self.bos_token_id, self.eos_token_id]
+            ]
+        return "".join([chr(t) if t > 31 else "" for t in tokens])
+
+    def apply_chat_template(
+        self, messages, tokenize=False, add_generation_prompt=True
+    ):
+        """Simple chat template for testing."""
+        result = ""
+        for msg in messages:
+            result += f"<{msg['role']}>{msg['content']}</{msg['role']}>"
+        if add_generation_prompt:
+            result += "<assistant>"
+        if tokenize:
+            return self.encode(result)
+        return result
+
+
+@pytest.fixture
+def mock_server():
+    """Create a mock server with a tokenizer."""
+    server = ServerHarness()
+    server.tokenizer = MockTokenizer()
+    # Add config for compatibility
+    class Config:
+        model_name = "test_model"
+
+    server.config = Config()
+    return server
+
+
+@pytest.mark.asyncio
+async def test_single_completion(mock_server):
+    """Test single completion tracking."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    prompt = "Hello"
+    prompt_tokens = mock_server.tokenizer.encode(prompt)
+    output_text = " World"
+    output_tokens = [ord(c) for c in output_text]  # Don't include BOS
+    output_logprobs = [-0.1, -0.2, -0.3, -0.4, -0.5, -0.6]
+
+    # Set up mock response
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt,
+        prompt_tokens=prompt_tokens,
+        output_tokens_list=[output_tokens],
+        output_logprobs_list=[output_logprobs],
+        finish_reasons=["stop"],
+    )
+
+    # Call managed server
+    result = await managed.completion(prompt=prompt)
+
+    # Check response
+    assert result.choices[0].text == " World"
+    assert result.choices[0].finish_reason == "stop"
+
+    # Check tracked state (default mode uses nodes list)
+    state = managed.get_state()
+    assert len(state["nodes"]) == 1
+
+    # Get the sequence node
+    node = state["nodes"][0]
+    full_text = prompt + output_text
+
+    # Check structure
+    assert node.full_text == full_text
+    assert len(node.tokens) == len(prompt_tokens) + len(output_tokens)
+
+    # Check masking: prompt should be -100, completion should have actual tokens
+    prompt_len = len(prompt_tokens)
+    assert all(t == -100 for t in node.masked_tokens[:prompt_len])
+    assert node.masked_tokens[prompt_len:] == output_tokens
+
+    # Check logprobs: prompt should be 0.0, completion should have actual logprobs
+    assert all(lp == 0.0 for lp in node.logprobs[:prompt_len])
+    assert node.logprobs[prompt_len:] == output_logprobs
+
+
+@pytest.mark.asyncio
+async def test_chat_completion(mock_server):
+    """Test chat completion with message conversion."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    messages = [{"role": "user", "content": "Hello"}]
+    prompt = managed._convert_messages_to_prompt(messages)
+    prompt_tokens = mock_server.tokenizer.encode(prompt)
+    output_text = "Hi there!"
+    output_tokens = [ord(c) for c in output_text]
+    output_logprobs = [-0.1] * len(output_tokens)
+
+    # Set up mock response
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt,
+        prompt_tokens=prompt_tokens,
+        output_tokens_list=[output_tokens],
+        output_logprobs_list=[output_logprobs],
+        finish_reasons=["stop"],
+    )
+
+    # Call managed server
+    result = await managed.chat_completion(messages=messages)
+
+    # Check response
+    assert result.choices[0].message.content == output_text
+    assert result.choices[0].message.role == "assistant"
+
+    # Check tracked state
+    state = managed.get_state()
+    assert len(state["nodes"]) == 1
+
+    # Verify tokens are properly tracked
+    node = state["nodes"][0]
+    prompt_len = len(prompt_tokens)
+    assert all(t == -100 for t in node.masked_tokens[:prompt_len])
+
+
+@pytest.mark.asyncio
+async def test_multi_turn_conversation(mock_server):
+    """Test multi-turn conversation with parent node merging."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    # Turn 1
+    prompt_1 = "Hello"
+    prompt_tokens_1 = mock_server.tokenizer.encode(prompt_1)
+    output_1 = " World"
+    output_tokens_1 = [ord(c) for c in output_1]
+    output_logprobs_1 = [-0.1] * len(output_tokens_1)
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt_1,
+        prompt_tokens=prompt_tokens_1,
+        output_tokens_list=[output_tokens_1],
+        output_logprobs_list=[output_logprobs_1],
+        finish_reasons=["stop"],
+    )
+
+    await managed.completion(prompt=prompt_1)
+
+    # Turn 2: extends turn 1
+    prompt_2 = "Hello World"  # Parent's full_text
+    # In a real scenario, prompt_tokens would be from parent node
+    full_tokens_from_turn_1 = prompt_tokens_1 + output_tokens_1
+    output_2 = "!"
+    output_tokens_2 = [ord(c) for c in output_2]
+    output_logprobs_2 = [-0.2]
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt_2,
+        prompt_tokens=full_tokens_from_turn_1,  # Use parent's full tokens
+        output_tokens_list=[output_tokens_2],
+        output_logprobs_list=[output_logprobs_2],
+        finish_reasons=["stop"],
+    )
+
+    await managed.completion(prompt=prompt_2)
+
+    # Check state - turn 2 extended turn 1, so it should replace that node
+    state = managed.get_state()
+    assert len(state["nodes"]) == 1
+
+    # Check the extended node
+    node = state["nodes"][0]
+    assert node.full_text == "Hello World!"
+
+    # Check the extended node has correct tokens
+    # Tokens should be: turn_1_full + output_2
+    assert len(node.tokens) == len(full_tokens_from_turn_1) + len(output_tokens_2)
+
+
+@pytest.mark.asyncio
+async def test_branching_with_n(mock_server):
+    """Test branching when n > 1."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    prompt = "Hello"
+    prompt_tokens = mock_server.tokenizer.encode(prompt)
+
+    # Three different completions
+    output_texts = [" World", " There", " Friend"]
+    output_tokens_list = [[ord(c) for c in text] for text in output_texts]
+    output_logprobs_list = [[-0.1] * len(tokens) for tokens in output_tokens_list]
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt,
+        prompt_tokens=prompt_tokens,
+        output_tokens_list=output_tokens_list,
+        output_logprobs_list=output_logprobs_list,
+        finish_reasons=["stop", "stop", "stop"],
+    )
+
+    result = await managed.completion(prompt=prompt, n=3)
+
+    # Check we got 3 completions
+    assert len(result.choices) == 3
+
+    # Check state has 3 nodes (one per branch)
+    state = managed.get_state()
+    assert len(state["nodes"]) == 3
+
+    # Verify each node has different text
+    full_texts = {node.full_text for node in state["nodes"]}
+    assert full_texts == {"Hello World", "Hello There", "Hello Friend"}
+
+
+@pytest.mark.asyncio
+async def test_bos_token_handling(mock_server):
+    """Test that BOS token is only at the start of sequence."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    prompt = "Test"
+    # Tokenizer adds BOS
+    prompt_tokens = mock_server.tokenizer.encode(prompt)  # [1, 84, 101, 115, 116]
+    assert prompt_tokens[0] == mock_server.tokenizer.bos_token_id
+
+    output_text = "ing"
+    output_tokens = [ord(c) for c in output_text]  # Should NOT have BOS
+    output_logprobs = [-0.1] * len(output_tokens)
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt,
+        prompt_tokens=prompt_tokens,
+        output_tokens_list=[output_tokens],
+        output_logprobs_list=[output_logprobs],
+        finish_reasons=["stop"],
+    )
+
+    await managed.completion(prompt=prompt)
+
+    # Check sequence
+    state = managed.get_state()
+    assert len(state["nodes"]) == 1
+    node = state["nodes"][0]
+
+    # Should have exactly one BOS at the start
+    assert node.tokens[0] == mock_server.tokenizer.bos_token_id
+    # And no BOS in the rest of the sequence
+    assert mock_server.tokenizer.bos_token_id not in node.tokens[1:]
+
+
+@pytest.mark.asyncio
+async def test_reset_clears_sequences(mock_server):
+    """Test that reset() clears all tracked sequences."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    prompt = "Test"
+    prompt_tokens = mock_server.tokenizer.encode(prompt)
+    output_tokens = [ord("!")]
+    output_logprobs = [-0.1]
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt,
+        prompt_tokens=prompt_tokens,
+        output_tokens_list=[output_tokens],
+        output_logprobs_list=[output_logprobs],
+        finish_reasons=["stop"],
+    )
+
+    await managed.completion(prompt=prompt)
+
+    # Verify nodes exist
+    state = managed.get_state()
+    assert len(state["nodes"]) > 0
+
+    # Reset
+    managed.reset()
+
+    # Verify nodes are cleared
+    state = managed.get_state()
+    assert len(state["nodes"]) == 0
+
+
+@pytest.mark.asyncio
+async def test_tokenizer_initialization_from_server(mock_server):
+    """Test that tokenizer is initialized from server if available."""
+    managed = ManagedServer(mock_server)  # Don't pass tokenizer
+
+    # Should have gotten tokenizer from server
+    assert managed.tokenizer is not None
+    assert managed.tokenizer == mock_server.tokenizer
+
+
+@pytest.mark.asyncio
+async def test_input_ids_extension(mock_server):
+    """Test that input_ids are computed correctly when extending sequences."""
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    # Turn 1
+    prompt_1 = "Hello"
+    prompt_tokens_1 = mock_server.tokenizer.encode(prompt_1)  # [1, 72, 101, 108, 108, 111]
+    output_1 = " World"
+    output_tokens_1 = [ord(c) for c in output_1]
+    output_logprobs_1 = [-0.1] * len(output_tokens_1)
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt_1,
+        prompt_tokens=prompt_tokens_1,
+        output_tokens_list=[output_tokens_1],
+        output_logprobs_list=[output_logprobs_1],
+        finish_reasons=["stop"],
+    )
+
+    await managed.completion(prompt=prompt_1)
+
+    # Turn 2: extends turn 1 with new text
+    prompt_2 = "Hello World!"  # Extends "Hello World" with "!"
+    # The input_ids should be: existing_node_tokens + tokenize("!")
+    node_1 = managed.current_nodes[0]
+    expected_input_ids = node_1.tokens + mock_server.tokenizer.encode("!", add_special_tokens=False)
+
+    output_2 = " Yay"
+    output_tokens_2 = [ord(c) for c in output_2]
+    output_logprobs_2 = [-0.2] * len(output_tokens_2)
+
+    # The server should receive the computed input_ids
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt_2,
+        prompt_tokens=expected_input_ids,  # Should match what ManagedServer computes!
+        output_tokens_list=[output_tokens_2],
+        output_logprobs_list=[output_logprobs_2],
+        finish_reasons=["stop"],
+    )
+
+    result = await managed.completion(prompt=prompt_2)
+
+    # Verify the response
+    assert result.choices[0].text == " Yay"
+
+    # Verify we have 1 node (turn 2 replaced turn 1 since it extended)
+    state = managed.get_state()
+    assert len(state["nodes"]) == 1
+
+    # Verify the node has the correct combined tokens
+    node = state["nodes"][0]
+    assert node.tokens == expected_input_ids + output_tokens_2
+
+
+@pytest.mark.asyncio
+async def test_multi_turn_chat_with_branching(mock_server):
+    """
+    Test complex multi-turn scenario:
+    - Turn 1: n=8 group completion → 8 nodes (1 assistant turn each)
+    - Turn 2: 8 individual calls extending each → extends those 8 nodes (2 assistant turns each)
+    - Turn 3: Add system prompt, 8 calls → 8 NEW nodes (different context, 3 assistant turns each)
+    Final: 16 nodes total
+    """
+    managed = ManagedServer(mock_server, tokenizer=mock_server.tokenizer)
+
+    # Turn 1: Single completion with n=8
+    messages_1 = [{"role": "user", "content": "Hello"}]
+    prompt_1 = managed._convert_messages_to_prompt(messages_1)
+    prompt_tokens_1 = mock_server.tokenizer.encode(prompt_1)
+
+    # Create 8 different responses
+    responses_1 = [f"Response{i}" for i in range(8)]
+    output_tokens_1 = [[ord(c) for c in resp] for resp in responses_1]
+    output_logprobs_1 = [[-0.1] * len(tokens) for tokens in output_tokens_1]
+
+    mock_server.set_tokens_and_logprobs_response(
+        prompt=prompt_1,
+        prompt_tokens=prompt_tokens_1,
+        output_tokens_list=output_tokens_1,
+        output_logprobs_list=output_logprobs_1,
+        finish_reasons=["stop"] * 8,
+    )
+
+    await managed.chat_completion(messages=messages_1, n=8)
+
+    # After turn 1: should have 8 nodes
+    state = managed.get_state()
+    assert len(state["nodes"]) == 8
+
+    # Save references to turn 1 nodes for later verification
+    turn_1_nodes = [node.full_text for node in state["nodes"]]
+
+    # Turn 2: For each of the 8 nodes, extend with another user+assistant turn
+    for i in range(8):
+        messages_2 = [
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": responses_1[i]},
+            {"role": "user", "content": "Continue"},
+        ]
+        prompt_2 = managed._convert_messages_to_prompt(messages_2)
+
+        # This prompt extends turn 1's output, so input_ids should use existing tokens
+        extending_node = state["nodes"][i]
+        # The new part is just the user turn
+        new_suffix = prompt_2[len(extending_node.full_text):]
+        expected_input_ids = extending_node.tokens + mock_server.tokenizer.encode(
+            new_suffix, add_special_tokens=False
+        )
+
+        response_2 = f"Continued{i}"
+        output_tokens_2 = [ord(c) for c in response_2]
+        output_logprobs_2 = [-0.2] * len(output_tokens_2)
+
+        mock_server.set_tokens_and_logprobs_response(
+            prompt=prompt_2,
+            prompt_tokens=expected_input_ids,
+            output_tokens_list=[output_tokens_2],
+            output_logprobs_list=[output_logprobs_2],
+            finish_reasons=["stop"],
+        )
+
+        await managed.chat_completion(messages=messages_2, n=1)
+
+    # After turn 2: still 8 nodes (they were extended/replaced, not added)
+    state = managed.get_state()
+    assert len(state["nodes"]) == 8
+
+    # Verify turn 2 nodes have 2 assistant turns each
+    for i in range(8):
+        node = state["nodes"][i]
+        assert f"Response{i}" in node.full_text
+        assert f"Continued{i}" in node.full_text
+
+    # Turn 3: Add system prompt at start - this creates a DIFFERENT context
+    # These won't extend because the prefix is different (system prompt added)
+    for i in range(8):
+        messages_3 = [
+            {"role": "system", "content": "Helpful"},
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": responses_1[i]},
+            {"role": "user", "content": "Continue"},
+            {"role": "assistant", "content": f"Continued{i}"},
+            {"role": "user", "content": "More"},
+        ]
+        prompt_3 = managed._convert_messages_to_prompt(messages_3)
+        prompt_tokens_3 = mock_server.tokenizer.encode(prompt_3)
+
+        response_3 = f"More{i}"
+        output_tokens_3 = [ord(c) for c in response_3]
+        output_logprobs_3 = [-0.3] * len(output_tokens_3)
+
+        mock_server.set_tokens_and_logprobs_response(
+            prompt=prompt_3,
+            prompt_tokens=prompt_tokens_3,
+            output_tokens_list=[output_tokens_3],
+            output_logprobs_list=[output_logprobs_3],
+            finish_reasons=["stop"],
+        )
+
+        await managed.chat_completion(messages=messages_3, n=1)
+
+    # After turn 3: 8 (turn 2 nodes) + 8 (turn 3 new context) = 16 nodes total!
+    state = managed.get_state()
+    assert len(state["nodes"]) == 16
+
+    # Verify structure:
+    # First 8 nodes: 2 assistant turns (no system prompt)
+    for i in range(8):
+        node = state["nodes"][i]
+        assert "Helpful" not in node.full_text  # No system prompt
+        assert f"Response{i}" in node.full_text
+        assert f"Continued{i}" in node.full_text
+        assert f"More{i}" not in node.full_text  # Not the third turn
+
+    # Last 8 nodes: 3 assistant turns (with system prompt)
+    for i in range(8, 16):
+        node = state["nodes"][i]
+        actual_i = i - 8
+        assert "Helpful" in node.full_text  # Has system prompt
+        assert f"Response{actual_i}" in node.full_text
+        assert f"Continued{actual_i}" in node.full_text
+        assert f"More{actual_i}" in node.full_text  # Has third turn
+
+
+if __name__ == "__main__":
+    # Run tests
+    pytest.main([__file__, "-v"])
diff --git a/environments/math_server_zero.py b/environments/math_server_zero.py
index 7596e6cf..93b7fda1 100644
--- a/environments/math_server_zero.py
+++ b/environments/math_server_zero.py
@@ -315,8 +315,10 @@ class MathEnv(BaseEnv):
         curr_length = int(curr_length * (self.curr_step / self.config.total_steps))
         curr_length += self.config.start_tok_length
         thinking_len = min(thinking_len, curr_length)
-        prompt_tokens, out_tokens, out_logprobs, finish_reasons = (
-            await self.server.tokens_and_logprobs_completion(
+
+        # Use managed server for automatic token/logprob tracking
+        async with self.server.managed_server(tokenizer=self.tokenizer) as managed:
+            completion = await managed.completion(
                 prompt=user_prompt,
                 n=self.config.group_size,
                 max_tokens=thinking_len,
@@ -324,22 +326,23 @@ class MathEnv(BaseEnv):
                 top_p=1.0,
                 stop=stop_list,
             )
-        )
-        # print(completions, flush=True)
+
+            # Get tracked sequences with aligned tokens and logprobs
+            state = managed.get_state()
+            nodes = state["nodes"]
+
+        # Extract data from SequenceNodes for scoring
         to_score = list()
         to_backlog = list()
-        for i, (tokens, logprobs, finish_reason) in enumerate(
-            zip(out_tokens, out_logprobs, finish_reasons)
-        ):
-            message = self.tokenizer.decode(prompt_tokens + tokens)
+        for i, (choice, node) in enumerate(zip(completion.choices, nodes)):
             to_score.append(
                 (
-                    message,
-                    item[1],
-                    finish_reason,
-                    prompt_tokens,
-                    tokens,
-                    logprobs,
+                    node.full_text,  # Complete text (prompt + completion)
+                    item[1],  # Answer
+                    choice.finish_reason,  # finish_reason (already a clean string)
+                    node.tokens,  # all tokens (prompt + completion)
+                    node.masked_tokens,  # masked tokens (already formatted correctly)
+                    node.logprobs,  # logprobs (already formatted correctly)
                 )
             )
         to_postprocess = await self.score(to_score)
@@ -376,11 +379,13 @@ class MathEnv(BaseEnv):
         for item in rollout_group_data:
             scores["overrides"].append(dict())
             resp = item[0]
-            finish_reason = item[2]
-            user_prompt_tokens = item[3]
-            out_toks = item[4]
-            out_logps = item[5]
-            if item[2]["type"] == "length":
+            finish_reason = item[2]  # Now a clean string like "stop" or "length"
+            # ManagedServer already provides properly formatted data
+            tokens = item[3]  # Full token sequence
+            masks = item[4]   # Masked tokens (already formatted)
+            inf_logp = item[5]  # Logprobs (already formatted)
+
+            if finish_reason == "length":
                 reward = False
                 if self.config.mask_too_long_completions:
                     scores["overrides"][-1]["set_advantage_to_zero"] = True
@@ -389,11 +394,7 @@ class MathEnv(BaseEnv):
                 reward = await task
                 if reward is None:
                     return None
-            tokens = user_prompt_tokens + out_toks
-            masks = [-100 for _ in range(len(user_prompt_tokens))]
-            masks = masks + out_toks
-            inf_logp = [0 for _ in range(len(user_prompt_tokens))]
-            inf_logp = inf_logp + out_logps
+
             assert len(inf_logp) == len(
                 masks
             ), f"{len(inf_logp)}, {len(masks)} mismatch"
@@ -405,7 +406,7 @@ class MathEnv(BaseEnv):
             # remove obviously bad examples
             if len([1 for i in masks if i != -100]) < 10:
                 continue
-            if (item[2] == "length") and (not self.config.mask_too_long_completions):
+            if (finish_reason == "length") and (not self.config.mask_too_long_completions):
                 scores["overrides"][-1]["set_advantage_to_zero"] = True
             scores["tokens"].append(tokens)
             scores["masks"].append(masks)