feat: Add LangChain middleware integration

.github/ci-path-filters.yml

@@ -57,6 +57,7 @@ node:
 python:
   - 'crates/python/Cargo.toml'
   - 'crates/python/src/**'
+  - 'integrations/langchain/**'
   - 'pyproject.toml'
   - 'python/**/!(*.md)'
   - 'uv.lock'

.github/workflows/ci_python.yml

@@ -81,7 +81,9 @@ jobs:
         with:
           version: ${{ steps.ci-config.outputs.uv_version }}
           enable-cache: true
-          cache-dependency-glob: ${{ env.NEMO_FLOW_CI_WORKSPACE }}/uv.lock
+          cache-dependency-glob: |
+            ${{ env.NEMO_FLOW_CI_WORKSPACE }}/uv.lock
+            ${{ env.NEMO_FLOW_CI_WORKSPACE }}/integrations/langchain/uv.lock
 
       - name: Set up Windows ARM Python
         if: ${{ matrix.platform == 'windows-arm64' }}
@@ -109,6 +111,10 @@ jobs:
         working-directory: ${{ env.NEMO_FLOW_CI_WORKSPACE }}
         run: just --set ci true --set output_dir "${{ github.workspace }}" test-python
 
+      - name: Run LangChain integration tests
+        working-directory: ${{ env.NEMO_FLOW_CI_WORKSPACE }}
+        run: just test-python-integration
+
       - name: Upload Python coverage to Codecov
         uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v6
         with:
@@ -170,7 +176,9 @@ jobs:
         with:
           version: ${{ steps.ci-config.outputs.uv_version }}
           enable-cache: true
-          cache-dependency-glob: ${{ env.NEMO_FLOW_CI_WORKSPACE }}/uv.lock
+          cache-dependency-glob: |
+            ${{ env.NEMO_FLOW_CI_WORKSPACE }}/uv.lock
+            ${{ env.NEMO_FLOW_CI_WORKSPACE }}/integrations/langchain/uv.lock
 
       - name: Set up Windows ARM Python
         if: ${{ matrix.platform == 'windows-arm64' }}
@@ -229,6 +237,13 @@ jobs:
             --set ref_name "${NEMO_FLOW_PACKAGE_VERSION}" \
             package-python
 
+      - name: Package LangChain integration wheel
+        if: ${{ matrix.platform == 'linux-amd64' }}
+        working-directory: ${{ env.NEMO_FLOW_CI_WORKSPACE }}/integrations/langchain
+        run: |
+          set -e
+          uv build --wheel --out-dir "${{ env.NEMO_FLOW_CI_WORKSPACE_TMP }}/wheels"
+
       - name: Upload wheel artifact
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
         with:

.gitignore

@@ -74,6 +74,7 @@ benchmarks/
 # Local third-party upstream checkouts. These are bootstrapped from
 # third_party/sources.lock and are intentionally excluded from the tracked
 # first-party repository surface.
+third_party/deepagents/
 third_party/langchain/
 third_party/langchain-nvidia/
 third_party/langgraph/
@@ -90,3 +91,6 @@ CHANGELOG.md
 
 crates/wasm/coverage/
 .scannerwork/
+
+# VSCode
+/.vscode

AGENTS.md

@@ -38,6 +38,7 @@ python/
 go/
   nemo_flow/  # Experimental Go CGo binding and tests
 docs/         # Sphinx documentation site
+integrations/ # Sample integrations using public APIs without patching
 scripts/      # Stable wrappers and helper scripts; build/test/docs entry points live in justfile
 third_party/  # Pinned upstream checkouts for sample integration patches
 patches/      # NeMo Flow patch sets applied to third_party checkouts
@@ -205,6 +206,7 @@ truth.
 
 ## Third-Party Integrations And Patches
 
+### Patch-based Integrations
 Sample integrations are maintained as patch sets, not as primary package source. The pinned upstream checkouts are listed in `third_party/sources.lock`, local checkouts live under `third_party/`, and NeMo Flow patches live under `patches/`.
 
 Current integration patch sets include:
@@ -227,6 +229,12 @@ Use the stable root-level wrappers:
 
 `apply-patches.sh` expects clean third-party checkouts. After editing an integration checkout, run `./scripts/generate-patches.sh` to regenerate patch files and verify they apply to a clean detached checkout.
 
+### Public API-based Integrations
+Some integrations can be implemented using public APIs without patching. These implementations are maintained under `integrations/` with their own README files and test suites.
+
+Current public API-based integrations include:
+- LangChain: `integrations/langchain`
+
 ## Documentation And Contribution Workflow
 
 These workflow notes keep public documentation, examples, and PR preparation aligned

README.md

@@ -133,6 +133,10 @@ The table below summarizes the support level for each binding surface.
 Some framework integrations are maintained as patch sets against upstream
 projects rather than as packages in this repository.
 
+### Public API-based Integrations
+Some integrations can be implemented using public APIs without patching. These implementations are maintained under `integrations/` with their own README files and test suites.
+
+### Patch-based Integrations
 Use [third_party/README.md](third_party/README.md) for the clone, checkout, and
 patch-application workflow for those integrations.
 

integrations/langchain/README.md

@@ -0,0 +1,74 @@
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+-->
+
+# NeMo Flow LangChain Integration
+
+This directory contains the `langchain_nemo_flow` package which provides observability integration for LangChain.
+
+The intent of this project is to enable as much NeMo Flow functionality as possible using public LangChain APIs without requiring changes to LangChain itself.
+
+For an alternate approach refer to [the patch-based integration in `third_party/langchain`](../../third_party/README-langchain.md).
+
+## Setup
+
+```bash
+uv venv .venv
+. .venv/bin/activate
+uv pip install -e .
+uv pip install -e integrations/langchain
+```
+
+Optionally install the langchain-nvidia-ai-endpoints package.
+
+```bash
+uv pip install langchain-nvidia-ai-endpoints
+```
+
+## Usage Example
+
+```python
+import asyncio
+
+import nemo_flow
+from langchain.agents import create_agent
+from langchain_core.tools import tool
+from langchain_nemo_flow import NemoFlowCallbackHandler, NemoFlowMiddleware
+
+@tool
+def get_weather(location: str) -> str:
+    """Get the current weather for a location."""
+    return f"The weather in {location} is sunny and 72 degrees."
+
+agent = create_agent(
+    model="nvidia:nvidia/nemotron-3-nano-30b-a3b",
+    tools=[get_weather],
+    middleware=[NemoFlowMiddleware()],
+    system_prompt="Use tools when they are relevant. Keep the final answer brief.",
+)
+
+input_payload = {
+    "messages": [
+        {
+            "role": "user",
+            "content": "What is the weather in San Francisco?",
+        }
+    ]
+}
+
+with nemo_flow.scope.scope("langchain-request", nemo_flow.ScopeType.Agent):
+    result = asyncio.run(agent.ainvoke(input_payload, config={"callbacks": [NemoFlowCallbackHandler()]}))
+
+final_message = result["messages"][-1]
+print(f"Final response: {final_message.content}")
+```
+
+## Validation
+
+Run tests for the `langchain_nemo_flow` package to validate the integration:
+
+```bash
+cd integrations/langchain
+uv run --group test pytest -q
+```

integrations/langchain/pyproject.toml

@@ -0,0 +1,75 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+[build-system]
+build-backend = "setuptools.build_meta"
+requires = ["setuptools>=64", "setuptools-scm>=8", "setuptools_dynamic_dependencies>=1.0.0"]
+
+[tool.setuptools.packages.find]
+where = ["src"]
+
+[tool.setuptools_scm]
+git_describe_command = "git describe --long --first-parent"
+root = "../.."
+
+[project]
+name = "langchain-nemo-flow"
+dynamic = ["version", "dependencies"]
+description = "NeMo Flow middleware and callback integrations for LangChain."
+requires-python = ">=3.11"
+license = "Apache-2.0"
+authors = [
+    { name = "NVIDIA Corporation & Affiliates" },
+]
+keywords = [
+    "agents",
+    "langchain",
+    "middleware",
+    "nemo-flow",
+    "observability",
+]
+classifiers = [
+    "Development Status :: 4 - Beta",
+    "Intended Audience :: Developers",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+]
+
+[tool.setuptools_dynamic_dependencies]
+dependencies = [
+    # Minimum version to support they hooks we are using
+    "langchain>=1.2.9,<2.0.0",
+    # Allow the langchain to dictate the version of langchain-core, not strictly needed
+    # but we do import from langchain_core
+    "langchain-core",
+    "nemo-flow == {version}",
+]
+
+[dependency-groups]
+test = [
+    "pytest>=8",
+]
+
+[project.urls]
+Documentation = "https://nvidia.github.io/NeMo-Flow/"
+Homepage = "https://github.com/NVIDIA/NeMo-Flow"
+Issues = "https://github.com/NVIDIA/NeMo-Flow/issues"
+Repository = "https://github.com/NVIDIA/NeMo-Flow"
+
+[tool.ruff]
+line-length = 120
+target-version = "py311"
+
+[tool.ruff.format]
+quote-style = "double"
+
+[tool.ruff.lint]
+select = ["E", "F", "W", "I"]
+
+[tool.uv]
+default-groups = ["test"]
+
+[tool.uv.sources]
+nemo-flow = { path = "../..", editable = true }

integrations/langchain/src/langchain_nemo_flow/__init__.py

@@ -0,0 +1,12 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""NeMo Flow integrations for LangChain."""
+
+from langchain_nemo_flow.callbacks import NemoFlowCallbackHandler
+from langchain_nemo_flow.middleware import NemoFlowMiddleware
+
+__all__ = [
+    "NemoFlowCallbackHandler",
+    "NemoFlowMiddleware",
+]