diff --git a/pkgs/development/python-modules/langchain-classic/default.nix b/pkgs/development/python-modules/langchain-classic/default.nix
new file mode 100644
index 000000000000..18bf037bebc9
--- /dev/null
+++ b/pkgs/development/python-modules/langchain-classic/default.nix
@@ -0,0 +1,114 @@
+{
+  lib,
+  buildPythonPackage,
+  fetchFromGitHub,
+
+  # build-system
+  hatchling,
+
+  # dependencies
+  langchain-core,
+  langchain-text-splitters,
+  langsmith,
+  pydantic,
+  pyyaml,
+  requests,
+  sqlalchemy,
+
+  # tests
+  blockbuster,
+  cffi,
+  freezegun,
+  langchain-openai,
+  langchain-tests,
+  lark,
+  numpy,
+  packaging,
+  pandas,
+  pytest-asyncio,
+  pytest-dotenv,
+  pytest-mock,
+  pytest-socket,
+  pytest-xdist,
+  pytestCheckHook,
+  requests-mock,
+  responses,
+  syrupy,
+  toml,
+}:
+
+buildPythonPackage rec {
+  pname = "langchain-classic";
+  version = "1.0.0-unstable-2025-11-11";
+  pyproject = true;
+
+  src = fetchFromGitHub {
+    owner = "langchain-ai";
+    repo = "langchain";
+    # no tagged releases avaialble
+    rev = "3dfea96ec1d2dac4e506d287860ee943c183c9f1";
+    hash = "sha256-U3UllSSa4tFz+nXAP6aNoYceU/xCPbwKSP2F2et+qgQ=";
+  };
+
+  sourceRoot = "${src.name}/libs/langchain";
+
+  build-system = [ hatchling ];
+
+  pythonRelaxDeps = [
+    # Each component release requests the exact latest core.
+    "langchain-core"
+  ];
+
+  dependencies = [
+    langchain-core
+    langchain-text-splitters
+    langsmith
+    pydantic
+    pyyaml
+    requests
+    sqlalchemy
+  ];
+
+  nativeCheckInputs = [
+    blockbuster
+    cffi
+    freezegun
+    langchain-core
+    langchain-openai
+    langchain-tests
+    langchain-text-splitters
+    lark
+    numpy
+    packaging
+    pandas
+    pytest-asyncio
+    pytest-dotenv
+    pytest-mock
+    pytest-socket
+    pytest-xdist
+    pytestCheckHook
+    requests-mock
+    responses
+    syrupy
+    toml
+  ];
+
+  enabledTestPaths = [
+    # integration_tests require network access, database access and require `OPENAI_API_KEY`, etc.
+    "tests/unit_tests"
+  ];
+
+  disabledTests = [
+    # Network access (web.example.com)
+    "test_socket_disabled"
+  ];
+
+  pythonImportsCheck = [ "langchain_classic" ];
+
+  meta = {
+    description = "Classic (0.x) compatibility layer for LangChain";
+    homepage = "https://github.com/langchain-ai/langchain/tree/master/libs/langchain";
+    license = lib.licenses.mit;
+    maintainers = with lib.maintainers; [ sarahec ];
+  };
+}
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index bcace84c7fdc..ca504685a4fd 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -8079,6 +8079,8 @@ self: super: with self; {
 
   langchain-chroma = callPackage ../development/python-modules/langchain-chroma { };
 
+  langchain-classic = callPackage ../development/python-modules/langchain-classic { };
+
   langchain-community = callPackage ../development/python-modules/langchain-community { };
 
   langchain-core = callPackage ../development/python-modules/langchain-core { };