RemoveMessage in subgraph not propagated back to main graph

[vanillechai]

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Example Code

from langgraph.graph.message import add_messages
from langchain_core.messages import AnyMessage
from typing_extensions import Annotated, TypedDict
from typing import Sequence
from langgraph.graph import StateGraph, START
from langchain_core.messages import HumanMessage, RemoveMessage


class TState(TypedDict):
    messages: Annotated[Sequence[AnyMessage], add_messages]


def node(state):
    msg = [RemoveMessage(id=m.id) for m in state["messages"]]
    return {"messages": msg}


subgraph_builder = StateGraph(TState)
subgraph_builder.add_node(node)
subgraph_builder.add_edge(START, "node")
subgraph = subgraph_builder.compile()

builder = StateGraph(TState)
builder.add_node("node_1", subgraph)
builder.add_edge(START, "node_1")
graph = builder.compile()

inputs = {"messages": [HumanMessage(content="hi")]}

print("\ncalling subgraph:", subgraph.invoke(inputs))

print("\ncalling graph:", graph.invoke(inputs))

Description

• I want to remove messages in a subgraph by sending a RemoveMessage with its id.
• While this works fine when running the subgraph independently, it fails when using it in the main graph.
• The example is greatly minimised and simplified to demonstrate the core of the issue.
• Expected: The message should have been removed from the graph state in both cases.
• Actual:
  Running the example:

calling subgraph: {'messages': []}

calling graph: {'messages': [HumanMessage(content='hi', additional_kwargs={}, response_metadata={}, id='51cb25b6-6800-43bd-a798-cbb0e34a97a2')]}

Any other state updates (e.g. changing messages, adding messages) show up as expected in the main graph. It seems that only the RemoveMessages are lost.

What am I missing here?

System Info

System Information

OS: Darwin
OS Version: Darwin Kernel Version 24.5.0: Tue Apr 22 19:48:46 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T8103
Python Version: 3.12.8 (main, Dec 6 2024, 14:26:42) [Clang 16.0.0 (clang-1600.0.26.4)]

Package Information

langchain_core: 0.3.58
langchain: 0.3.25
langchain_community: 0.3.23
langsmith: 0.3.42
langchain_anthropic: 0.3.12
langchain_mcp_adapters: 0.1.7
langchain_openai: 0.3.16
langchain_opengauss: 0.1.3
langchain_text_splitters: 0.3.8
langgraph_sdk: 0.1.66

Optional packages not installed

langserve

Other Dependencies

aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
anthropic<1,>=0.49.0: Installed. No version info available.
async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
httpx: 0.28.1
httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
jsonpatch<2.0,>=1.33: Installed. No version info available.
langchain-anthropic;: Installed. No version info available.
langchain-aws;: Installed. No version info available.
langchain-azure-ai;: Installed. No version info available.
langchain-cohere;: Installed. No version info available.
langchain-community;: Installed. No version info available.
langchain-core<0.4,>=0.3.36: Installed. No version info available.
langchain-core<1.0.0,>=0.3.51: Installed. No version info available.
langchain-core<1.0.0,>=0.3.53: Installed. No version info available.
langchain-core<1.0.0,>=0.3.56: Installed. No version info available.
langchain-core<1.0.0,>=0.3.58: Installed. No version info available.
langchain-deepseek;: Installed. No version info available.
langchain-fireworks;: Installed. No version info available.
langchain-google-genai;: Installed. No version info available.
langchain-google-vertexai;: Installed. No version info available.
langchain-groq;: Installed. No version info available.
langchain-huggingface;: Installed. No version info available.
langchain-mistralai;: Installed. No version info available.
langchain-ollama;: Installed. No version info available.
langchain-openai;: Installed. No version info available.
langchain-perplexity;: Installed. No version info available.
langchain-text-splitters<1.0.0,>=0.3.8: Installed. No version info available.
langchain-together;: Installed. No version info available.
langchain-xai;: Installed. No version info available.
langchain<1.0.0,>=0.3.24: Installed. No version info available.
langsmith-pyo3: Installed. No version info available.
langsmith<0.4,>=0.1.125: Installed. No version info available.
langsmith<0.4,>=0.1.17: Installed. No version info available.
mcp>=1.9.2: Installed. No version info available.
numpy>=1.26.2;: Installed. No version info available.
numpy>=2.1.0;: Installed. No version info available.
openai-agents: Installed. No version info available.
openai<2.0.0,>=1.68.2: Installed. No version info available.
opentelemetry-api: 1.32.1
opentelemetry-exporter-otlp-proto-http: 1.32.1
opentelemetry-sdk: 1.32.1
orjson: 3.10.18
packaging: 24.2
packaging<25,>=23.2: Installed. No version info available.
psycopg2-binary: 2.9.10
pydantic: 2.11.4
pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
pydantic<3.0.0,>=2.5.2;: Installed. No version info available.
pydantic<3.0.0,>=2.7.4: Installed. No version info available.
pydantic<3.0.0,>=2.7.4;: Installed. No version info available.
pytest: 8.4.1
PyYAML>=5.3: Installed. No version info available.
requests: 2.32.3
requests-toolbelt: 1.0.0
requests<3,>=2: Installed. No version info available.
rich: 13.9.4
SQLAlchemy<3,>=1.4: Installed. No version info available.
tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
tiktoken<1,>=0.7: Installed. No version info available.
typing-extensions>=4.7: Installed. No version info available.
zstandard: 0.23.0