[AI-72] LangGraph plugin samples by DABH · Pull Request #289 · temporalio/samples-python

DABH · 2026-04-14T23:09:55Z

Summary

Add samples demonstrating the Temporal LangGraph plugin, which runs LangGraph workflows as durable Temporal workflows. Each graph node or @task executes as a Temporal activity or in a workflow, enabling features like automatic retries, timeouts, and crash recovery.

Samples are provided for both the Graph API (declarative StateGraph with nodes and edges) and the Functional API (imperative @task / @entrypoint decorators).

Sample	Graph API	Functional API	Description
Hello World	✅	✅	Minimal sample — single node/task that processes a query string. Start here.
Human-in-the-loop	✅	✅	Chatbot that uses `interrupt()` to pause for human approval, Temporal signals to receive feedback, and queries to expose the pending draft.
Continue-as-new	✅	✅	Multi-stage data pipeline that uses `continue-as-new` with task result caching so previously-completed stages are not re-executed.
ReAct Agent	✅	✅	Tool-calling agent loop. Graph API uses `add_conditional_edges`; Functional API uses a `while` loop.
Control Flow	—	✅	Parallel task execution, `for` loops, and `if/else` branching — patterns that are natural in the Functional API.
LangSmith Tracing	✅	✅	Combines `LangGraphPlugin` with Temporal's `LangSmithPlugin` for durable execution + full LLM observability. Requires API keys.

Key Features Demonstrated

Durable execution — Every graph node / @task runs as a Temporal activity with configurable timeouts and retry policies.
Human-in-the-loop — LangGraph's interrupt() pauses the graph; Temporal signals deliver human input; queries expose pending state to UIs.
Continue-as-new with caching — get_cache() captures completed task results; passing the cache to the next execution avoids re-running them.
Conditional routing — Graph API's add_conditional_edges and Functional API's native if/else/while for agent loops.
Parallel execution — Functional API launches multiple tasks concurrently by creating futures before awaiting them.
LangSmith observability — LangSmithPlugin on the client + LangGraphPlugin on the worker for full trace propagation through Temporal workflows.

Related PRs

SDK: AI-36: Add LangGraph plugin sdk-python#1448 [shipped in Python SDK 1.27.0]
Supersedes: LangGraph Samples #272

Test plan

Samples are not runnable until the SDK PR lands; verify after merge of AI-36: Add LangGraph plugin sdk-python#1448
Run each sample with uv run langgraph_plugin/<api>/<sample>/run_worker.py + run_workflow.py
LangSmith tracing samples require ANTHROPIC_API_KEY and LANGCHAIN_API_KEY

Seven samples demonstrating the Temporal LangGraph plugin across both the Graph API and Functional API: - Human-in-the-loop: interrupt() + Temporal signals for chatbot approval - Continue-as-new: task result caching across workflow boundaries - ReAct agent: tool-calling loop with conditional edges / while loop - Control flow (Functional API only): parallel, for-loop, if/else Related SDK PR: temporalio/sdk-python#1448

CLAassistant · 2026-04-14T23:10:01Z

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CLAassistant · 2026-04-14T23:10:03Z

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… merge) so that CI otherwise passes

Copilot

Pull request overview

Adds a new langgraph_plugin/ sample suite to demonstrate running LangGraph workflows as durable Temporal workflows via the Temporal LangGraph plugin, covering both LangGraph Graph API and Functional API patterns.

Changes:

Introduces 7 new LangGraph+Temporal sample workflows (human-in-the-loop, continue-as-new w/ caching, ReAct agent, control-flow).
Adds a new langgraph dependency group and includes langgraph_plugin in the build packages list.
Updates repository documentation to link to the new sample suite and provides a dedicated README for running the samples.

Reviewed changes

Copilot reviewed 24 out of 34 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
pyproject.toml	Adds `langgraph` dependency group, includes `langgraph_plugin` in wheel packages, adjusts lint/test tasks, and adds mypy override.
README.md	Links the new `langgraph_plugin` samples from the repo root README.
langgraph_plugin/README.md	Adds usage documentation and a sample matrix for the new suite.
langgraph_plugin/init.py	Declares the new top-level sample package.
langgraph_plugin/graph_api/init.py	Declares Graph API samples namespace.
langgraph_plugin/graph_api/react_agent/init.py	Declares Graph API ReAct agent package.
langgraph_plugin/graph_api/react_agent/workflow.py	Implements Graph API ReAct agent workflow and graph definition.
langgraph_plugin/graph_api/react_agent/run_worker.py	Worker wiring for Graph API ReAct agent sample.
langgraph_plugin/graph_api/react_agent/run_workflow.py	Starter script for Graph API ReAct agent sample.
langgraph_plugin/graph_api/human_in_the_loop/init.py	Declares Graph API human-in-the-loop package.
langgraph_plugin/graph_api/human_in_the_loop/workflow.py	Implements Graph API interrupt + Temporal signal/query human approval flow.
langgraph_plugin/graph_api/human_in_the_loop/run_worker.py	Worker wiring for Graph API human-in-the-loop sample.
langgraph_plugin/graph_api/human_in_the_loop/run_workflow.py	Starter script for Graph API human-in-the-loop sample.
langgraph_plugin/graph_api/continue_as_new/init.py	Declares Graph API continue-as-new package.
langgraph_plugin/graph_api/continue_as_new/workflow.py	Implements Graph API pipeline w/ continue-as-new + cache handoff.
langgraph_plugin/graph_api/continue_as_new/run_worker.py	Worker wiring for Graph API continue-as-new sample.
langgraph_plugin/graph_api/continue_as_new/run_workflow.py	Starter script for Graph API continue-as-new sample.
langgraph_plugin/functional_api/init.py	Declares Functional API samples namespace.
langgraph_plugin/functional_api/react_agent/init.py	Declares Functional API ReAct agent package.
langgraph_plugin/functional_api/react_agent/workflow.py	Implements Functional API ReAct agent via `@task` + `@entrypoint`.
langgraph_plugin/functional_api/react_agent/run_worker.py	Worker wiring for Functional API ReAct agent sample.
langgraph_plugin/functional_api/react_agent/run_workflow.py	Starter script for Functional API ReAct agent sample.
langgraph_plugin/functional_api/human_in_the_loop/init.py	Declares Functional API human-in-the-loop package.
langgraph_plugin/functional_api/human_in_the_loop/workflow.py	Implements Functional API interrupt + signal/query human approval flow.
langgraph_plugin/functional_api/human_in_the_loop/run_worker.py	Worker wiring for Functional API human-in-the-loop sample.
langgraph_plugin/functional_api/human_in_the_loop/run_workflow.py	Starter script for Functional API human-in-the-loop sample.
langgraph_plugin/functional_api/control_flow/init.py	Declares Functional API control-flow package.
langgraph_plugin/functional_api/control_flow/workflow.py	Implements Functional API sample demonstrating parallelism + branching.
langgraph_plugin/functional_api/control_flow/run_worker.py	Worker wiring for Functional API control-flow sample.
langgraph_plugin/functional_api/control_flow/run_workflow.py	Starter script for Functional API control-flow sample.
langgraph_plugin/functional_api/continue_as_new/init.py	Declares Functional API continue-as-new package.
langgraph_plugin/functional_api/continue_as_new/workflow.py	Implements Functional API pipeline w/ continue-as-new + cache handoff.
langgraph_plugin/functional_api/continue_as_new/run_worker.py	Worker wiring for Functional API continue-as-new sample.
langgraph_plugin/functional_api/continue_as_new/run_workflow.py	Starter script for Functional API continue-as-new sample.

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…gs, and configurable client

Combines LangGraphPlugin (durable execution) with LangSmithPlugin (observability) for full tracing of LLM calls through Temporal workflows.

- graphs parameter is now a list, not a dict - No graph()/entrypoint() lookup functions — reference objects directly - No entrypoints parameter on LangGraphPlugin - Use set_cache()/get_cache() for continue-as-new caching - Update tests and READMEs accordingly

# Conflicts: # pyproject.toml # uv.lock

The plugin API has evolved past PR #1448: - LangGraphPlugin(graphs=...) now takes dict[str, StateGraph], not list - Same for entrypoints (dict[str, Pregel]) - Each node/task must declare execute_in: "activity" | "workflow" in metadata - Workflows look up registered graphs/entrypoints via graph(name) / entrypoint(name) instead of importing them directly - get_cache/set_cache replaced by cache() and graph(name, cache=...) / entrypoint(name, cache=...) Other changes: - State schemas converted from primitives (str, int) to TypedDict, since langgraph's StateT is bound to TypedDict / dataclass / pydantic models - Module-level graph instances replaced with make_<name>_graph() factories because LangGraphPlugin mutates node metadata in-place at construction time, which prevented reuse across tests - langgraph dep group now pulls langchain, langchain-anthropic, and temporalio[langgraph,langsmith] so the langsmith_tracing samples and human_in_the_loop's RunnableConfig usage actually resolve

These features rely on contextvars propagation through asyncio.create_task(), which is only available in Python 3.11+. On 3.10 they hang rather than fail cleanly, so CI sat for an hour before today's fix landed. Mirrors the pytestmark skipif used in sdk-python's own contrib/langgraph tests.

- Drop cross-references between Functional API and Graph API READMEs so each stands alone (review comment 1) - Combine run_worker.py + run_workflow.py into a single main.py for the langsmith_tracing samples to reduce setup steps (review comment 2) - Fix workflow -> Workflow casing (review comment 3) - Alias temporalio's entrypoint and graph helpers as temporal_entrypoint / temporal_graph at import sites to avoid the langgraph.func.entrypoint collision (review comment 4) - Demonstrate @Traceable in three places in both langsmith_tracing samples: on the Activity/task itself, on a helper called from the Activity, and on a helper called from the Workflow (review comment 5) - Drop unnecessary single-task list comprehension for activity_options in hello_world and langsmith_tracing functional samples (review comment 6) - Spell out 'temporal server start-dev' in every sample README's prerequisites (review comment 7) - Fix stale README references to get_cache() now that the API is cache() (review comment 8) - Rename arbitrarily-named ETL pipeline functions in continue_as_new to honest math names (double / add_50 / triple) per review comment 9

- Drop the [tool.uv.sources] git pin; consume temporalio from PyPI now that 1.27.0 ships the LangGraph plugin. - Keep the protoc CI step around as a permanent fixture so we don't have to add and remove it each time we iterate on a new plugin sample. - Replace dict-comprehension activity_options with explicit per-task literals in the Functional API samples. - Emphasize workflow.wait_condition() in the human-in-the-loop READMEs as the durable wait primitive that pairs with interrupt() and signals. - Clarify that the task result cache is provided by the LangGraph plugin (Temporal), not by upstream LangGraph. - Drop "Same pattern as the Graph API version" cross-references from Functional API workflow docstrings; readers pick one API style. - Tighten the Functional API LangSmith tracing README copy. - Point the parent README to the released contrib package docs.

DABH requested a review from a team as a code owner April 14, 2026 23:09

DABH requested review from brianstrauch and Copilot April 14, 2026 23:16

Copilot started reviewing on behalf of DABH April 14, 2026 23:16 View session

DABH added 2 commits April 14, 2026 18:17

Remove explicit langchain deps from langgraph group to avoid conflict

8a260c6

Declare langchain and langgraph as conflicting dependency groups

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DABH added 2 commits April 14, 2026 18:22

Fix import sorting and formatting

3e7f91b

Update dependencies and lint config (temporarily - waiting for SDK PR…

0505fd1

… merge) so that CI otherwise passes

DABH force-pushed the langgraph-samples branch from 0256bd3 to 0505fd1 Compare April 15, 2026 00:38

DABH requested a review from Copilot April 15, 2026 00:40

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DABH added 3 commits April 14, 2026 21:21

Add hello_world samples, per-sample READMEs, tests, __init__ docstrin…

ee781cd

…gs, and configurable client

Address review: consistent v2 API, unique thread_id, SDK prereq note

e2832bb

Remove SDK prereq note - PR won't merge until plugin is released

f3fb15c

DABH mentioned this pull request Apr 15, 2026

LangGraph Samples #272

Closed

Add LangSmith tracing sample (Graph API + Functional API)

67d1310

Combines LangGraphPlugin (durable execution) with LangSmithPlugin (observability) for full tracing of LLM calls through Temporal workflows.

brianstrauch reviewed Apr 15, 2026

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DABH mentioned this pull request Apr 16, 2026

Add LangGraph integration documentation temporalio/documentation#4442

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DABH added 3 commits April 18, 2026 17:24

Merge branch 'main' into langgraph-samples

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# Conflicts: # pyproject.toml # uv.lock

DABH force-pushed the langgraph-samples branch from 3ebfbd2 to 9c06edd Compare April 29, 2026 04:05

DABH added 3 commits April 28, 2026 23:15

CI: install protoc for building temporalio from sdk-python git source

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DABH requested a review from brianstrauch April 29, 2026 06:30

brianstrauch reviewed Apr 29, 2026

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brianstrauch approved these changes May 4, 2026

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Merge branch 'main' into langgraph-samples

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DABH changed the title ~~LangGraph plugin samples~~ [AI-72] LangGraph plugin samples May 4, 2026

DABH merged commit 601f5d4 into temporalio:main May 4, 2026
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Summary

Key Features Demonstrated

Related PRs

Test plan

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DABH commented Apr 14, 2026 •

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