Add agent langgraph basic

agent-langgraph-basic/.env.example

@@ -0,0 +1,29 @@
+# Copy to .env for local development:  cp .env.example .env
+#
+# The only required setting for local dev is a Databricks auth profile (used to call the model).
+# Everything else — Lakebase durability, MLflow tracing — is optional and off by default.
+
+# Databricks auth profile (from `databricks auth profiles`). Used to call the model endpoint.
+DATABRICKS_CONFIG_PROFILE=DEFAULT
+# Or use explicit host/token instead of a profile:
+# DATABRICKS_HOST=https://<your-workspace>.databricks.com
+# DATABRICKS_TOKEN=dapi...
+
+# --- Optional: MLflow tracing ---
+# Leave UNSET to skip tracing (local dev). To enable, set both: an experiment to log to, and the
+# tracking destination (your workspace).
+# MLFLOW_EXPERIMENT_ID=
+# MLFLOW_TRACKING_URI="databricks"
+
+# --- Optional: durable conversation history (managed session store) ---
+# Leave UNSET to keep the local SQLite session store. Set to a managed session store name to
+# persist the transcript to its agents/v1 items API (durable, shared across replicas).
+# AGENT_SESSION_STORE=my-agent-sessions
+
+# --- Optional: long-running background mode + crash recovery (Lakebase) ---
+# Leave UNSET to serve in-request. Set the Lakebase endpoint to enable durable background mode.
+# LAKEBASE_AUTOSCALING_ENDPOINT=
+
+# --- Optional: local SQLite session store path (when AGENT_SESSION_STORE is unset) ---
+# Defaults to a file so history survives restarts. Set ":memory:" for ephemeral storage.
+# LOCAL_SESSION_DB_PATH=local_agent_sessions.db

agent-langgraph-basic/.gitignore

@@ -0,0 +1,195 @@
+# Created by https://www.toptal.com/developers/gitignore/api/python
+# Edit at https://www.toptal.com/developers/gitignore?templates=python
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# poetry
+#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
+#poetry.lock
+
+# pdm
+#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
+#pdm.lock
+#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
+#   in version control.
+#   https://pdm.fming.dev/#use-with-ide
+.pdm.toml
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# PyCharm
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/
+
+# VS Code
+.vscode/
+
+### Python Patch ###
+# Poetry local configuration file - https://python-poetry.org/docs/configuration/#local-configuration
+poetry.toml
+
+# ruff
+.ruff_cache/
+
+# LSP config files
+pyrightconfig.json
+
+# End of https://www.toptal.com/developers/gitignore/api/python
+
+.DS_*
+
+# Databricks / MLflow local artifacts
+**/mlruns/
+mlflow.db
+**/.databricks
+.claude/
+
+# Environment files
+**/.env
+**/.env.local
+
+# Local (Lakebase-free) SQLite session store
+local_agent_sessions.db
+local_agent_sessions.db-*
+*.db-journal

agent-langgraph-basic/AGENTS.md

@@ -0,0 +1,69 @@
+# Agent Development Guide
+
+A lean LangGraph agent backend for Databricks Apps. Local-first: runs with no database and no setup
+beyond a Databricks auth profile. Lakebase durability and MLflow tracing are optional.
+
+See `README.md` for the full run / deploy / client-contract docs. This file is the quick map for
+making changes.
+
+## Run it
+
+```bash
+cp .env.example .env          # set DATABRICKS_CONFIG_PROFILE=<your-profile>
+uv run start-server           # http://localhost:8000
+```
+
+No database needed — conversation state uses an in-process LangGraph checkpointer by default.
+
+## Where things live
+
+| You want to… | Edit |
+| --- | --- |
+| Change model / instructions | `agent/agent.py` (`create_agent_graph`) |
+| Add a function tool | new `*.py` in `agent/tools/` with a `@tool` function (auto-collected) |
+| Add an MCP server | append a `DatabricksMCPServer` to `build_mcp_servers()` in `agent/mcps.py` |
+| Change how a request maps to a run | `agent/agent.py` (`@invoke` / `@stream` handlers) |
+| Change the session checkpointer | `agent/mason/session_store.py` |
+| Server / durability wiring | `server/start_server.py` (rarely needed) |
+| Add a test | `tests/` (hermetic; gate model calls on a workspace profile — see `test_agent.py`) |
+
+`agent/mason/` holds plumbing (session checkpointer, tracing, MCP tool loading, wire translation)
+slated to move into Databricks SDKs — grouped so that migration is localized. You rarely edit it;
+build the agent in `agent/agent.py`, `agent/tools/`, and `agent/mcps.py`.
+
+## How tools register
+
+`agent/tools/all_tools()` auto-imports every module in the package and collects every
+`@tool`-decorated `BaseTool` it finds. So a tool registers just by existing in a file there —
+`create_agent_graph()` calls `all_tools()`. **Do not** edit `agent/agent.py` to add a tool — just
+add a file to `agent/tools/`.
+
+## Sessions & durability
+
+- Default: `agent/mason/session_store.py`'s `checkpointer()` returns an in-process `InMemorySaver`,
+  keyed per request by `thread_config(session_id)` — no database, multi-turn works in-process.
+- **Two independent durable stores:**
+  - Conversation history → swap the checkpointer for a `PostgresSaver` over Lakebase (durable,
+    shared across replicas).
+  - `LAKEBASE_AUTOSCALING_ENDPOINT` → `start_server.py` passes it into `LongRunningAgentServer` for
+    its durable server store (background mode + crash recovery).
+  - Enable either/both/neither.
+
+## MLflow tracing
+
+Optional. Set both `MLFLOW_EXPERIMENT_ID` and `MLFLOW_TRACKING_URI` to enable (`mlflow.langchain.autolog()`);
+leave either unset to skip (the server boots with tracing disabled).
+
+## Quick commands
+
+| Task | Command |
+| --- | --- |
+| Run locally | `uv run start-server` |
+| Run via CLI local App runner | `databricks apps run-local --prepare-environment -p <profile>` |
+| Test | `uv run pytest` (hermetic; live model test runs only with a profile) |
+| Deploy | `databricks apps deploy agent-langgraph-basic --source-code-path <path>` |
+
+## Notes for maintainers
+
+- `agent/mason/wire/` is LangGraph-specific (inbound request→session id; outbound `astream`
+  `updates`/`messages` events→Responses wire events).

agent-langgraph-basic/CLAUDE.md

@@ -0,0 +1 @@
+@AGENTS.md