wren-langchain 0.2.0

LangChain and LangGraph integration for Wren AI Core — attach a CLI-prepared Wren project to your agent in three lines.

wren-langchain

LangChain and LangGraph integration for Wren AI Core.

Attach a CLI-prepared Wren project to a LangChain agent in three lines:

from wren_langchain import WrenToolkit
from langchain.agents import create_agent

toolkit = WrenToolkit.from_project("./analytics_db")
agent = create_agent(
    model="openai:gpt-4o",
    tools=toolkit.get_tools(),
    system_prompt=toolkit.system_prompt(),
)

Complete runnable demos:

• examples/langchain_demo.py — uses langchain.agents.create_agent, the high-level factory. Smallest amount of code; recommended starting point.
• examples/langgraph_demo.py — builds the ReAct loop from LangGraph primitives (StateGraph + ToolNode + conditional edges). Use this when you need custom routing, state, or streaming.

Prerequisites

This package assumes you have already used the Wren CLI to prepare a project:

wren context init
wren context build
wren memory index   # optional but recommended
wren profile add ...

If you haven't installed the CLI yet, install wren-engine first:

pip install "wren-engine[memory,postgres]"

Installation

wren-langchain exposes datasource and memory extras that pass through to the matching wren-engine extras, so you only have to install once:

# Match the datasource your wren_project.yml uses (DuckDB needs no extra):
pip install "wren-langchain[mysql]"
pip install "wren-langchain[postgres,memory]"
pip install "wren-langchain[bigquery,memory]"

# Available datasource extras: postgres, mysql, bigquery, snowflake,
# clickhouse, trino, mssql, databricks, redshift, spark, athena, oracle.

# `memory` extra enables the three memory tools (wren_fetch_context,
# wren_recall_queries, wren_store_query). Without it the toolkit exposes
# only the three runtime tools.

# Install everything for experimentation:
pip install "wren-langchain[all,memory]"

If you prefer to install wren-engine separately (e.g. you already use the CLI), the bare package is enough and your existing wren-engine extras carry over:

pip install wren-langchain

What you get

WrenToolkit.from_project(path) exposes:

• 6 LLM-facing tools (3 runtime + 3 memory when .wren/memory/ exists):
  • wren_query — execute SQL through Wren's context layer, returns rows
  • wren_dry_plan — plan SQL without execution to verify it targets models correctly
  • wren_list_models — list project models with column counts and descriptions
  • wren_fetch_context — retrieve relevant schema/business context for a question
  • wren_recall_queries — surface similar past NL→SQL pairs as few-shot examples
  • wren_store_query — persist a confirmed NL→SQL pair for future recall
• Direct Python API:

  toolkit.query("SELECT ...")             # → pyarrow.Table
  toolkit.dry_plan("SELECT ...")           # → str (target-dialect SQL)
  toolkit.dry_run("SELECT ...")            # → None (validation only)
  toolkit.memory.fetch("revenue trends")
  toolkit.memory.recall("top customers")
  toolkit.memory.store(nl="...", sql="...", tags=["..."])
  

• toolkit.system_prompt() — Wren-aware system prompt that adapts to enabled tools and includes your project's instructions.md when present.

Configuration

WrenToolkit.from_project(
    path,                # required — path to your prepared Wren project
    profile="prod",      # optional — picks a named profile (default: active)
)

toolkit.get_tools(
    include_memory_write=True,   # set False to keep memory read-only
    raise_on_error=False,        # set True to surface exceptions to LangChain retry
)

Memory is auto-detected from the project: present <path>/.wren/memory/ exposes the 3 memory tools alongside the 3 runtime tools; absent → only the runtime tools. To enable, run wren memory index from the project root; to disable, delete the directory. There is no override kwarg.

include_memory_write=False removes wren_store_query from the returned list while keeping wren_fetch_context and wren_recall_queries. Use this when you want the agent to read curated past pairs but never persist new ones (e.g., a shared / pinned memory). When memory is disabled, this flag has no effect — no memory tools are returned regardless.

How path, profile, and .env interact

Three pieces of state combine to produce a connection. Understanding which one drives what avoids surprises:

Source	Holds	Resolved by
path/wren_project.yml + target/mdl.json	MDL models, schema, data_source	from_project(path)
path/.env	Secret values (MYSQL_HOST, MYSQL_PASSWORD, …)	from_project(path) auto-loads it
~/.wren/profiles.yml	Connection template (host: ${MYSQL_HOST}, …)	profile= kwarg or fallback chain

profile= resolution chain (highest priority first):

1. Explicit profile="<name>" kwarg passed to from_project.
2. The profile: field inside the project's wren_project.yml, e.g.:

   schema_version: 3
   data_source: mysql
   profile: test-project3   # locks this project to a specific profile
   

3. The globally active profile (wren profile switch <name>).

When does profile= actually change which database you connect to?

This is subtle, because profile values are templates that resolve from the project's .env, not standalone connection records. Three scenarios:

Scenario A — profile= is a no-op (most common)

Your ~/.wren/profiles.yml has multiple profiles that all use the same placeholder names:

profiles:
  test-project3:
    datasource: mysql
    host: ${MYSQL_HOST}
    database: ${MYSQL_DATABASE}
  test-project4:
    datasource: mysql
    host: ${MYSQL_HOST}        # ← same placeholder
    database: ${MYSQL_DATABASE}

Because from_project("/path/to/test-project3") loads test-project3/.env into the environment, both profiles resolve to the same connection — ${MYSQL_HOST} reads from project3's .env regardless of which profile name you picked. Profile selection is cosmetic in this layout.

Scenario B — profile= selects different placeholders

profiles:
  dev:
    host: ${DEV_HOST}
  prod:
    host: ${PROD_HOST}

Now profile="dev" and profile="prod" read different env vars from the same .env, so the choice matters.

Scenario C — profile= selects hardcoded values or different datasources

profiles:
  local:
    datasource: duckdb
    url: /tmp/local.duckdb
    format: duckdb
  remote:
    datasource: postgres
    host: prod-db.example.com   # hardcoded
    port: 5432

profile="local" vs profile="remote" connect to genuinely different databases. Note: if wren_project.yml specifies data_source: and you pick a profile with a different datasource:, the connection will fail — the project's MDL is built against one specific dialect.

Recommendation: one project, one profile

If you follow the common pattern of one Wren project per database (each project gets its own .env and points at its own DB), set the profile inside wren_project.yml and stop passing profile=:

# wren_project.yml
schema_version: 3
name: test-project3
data_source: mysql
profile: test-project3

toolkit = WrenToolkit.from_project("/path/to/test-project3")

This pins the project to its intended profile, no more "is the active profile what I think it is?" — and it survives wren profile switch elsewhere on the same machine.

Compatibility matrix

wren-langchain	wren-engine	langchain	langgraph
0.1.0	>= 0.5.0	>= 1.0	>= 1.0

Known limitations (v0.1)

• Synchronous tools only. LangChain auto-bridges to a thread pool when tools run in async LangGraph; multi-tenant servers serving > ~32 concurrent users may exhaust the default executor pool.
• One toolkit per agent. If you need to query multiple Wren projects, build separate agents.
• Memory is auto-detected from .wren/memory/ and there is no kwarg to override. To enable, run wren memory index; to disable, delete the directory.
• No hot reload mechanism. target/mdl.json is re-read on every tool call, so wren context build updates from CLI are picked up automatically. Profile changes require constructing a new toolkit.
• Don't run wren memory index while an agent is using the same project. The index operation drops and recreates the LanceDB schema table; concurrent reads may transiently fail.

License

Apache License 2.0. See LICENSE for the full text, or the repository-level LICENSE for the path-to-license map.

The names "Wren", "WrenAI", and the project's logos are trademarks of Canner, Inc. and are not licensed under Apache 2.0; their use is governed separately.