AI-36: Add LangGraph plugin

[brianstrauch]

Summary

• Add a new temporalio.contrib.langgraph plugin that runs LangGraph nodes and tasks as Temporal Activities, bringing durable execution, automatic retries, and timeouts to AI agent workflows
• Supports both the LangGraph Graph API (wrapping StateGraph nodes) and Functional API (wrapping @entrypoint / @task functions)
• Includes a task result cache for continue-as-new support, so previously completed nodes/tasks are not re-executed across workflow continuations
• Handles GraphInterrupt propagation between Activities and Workflows for human-in-the-loop patterns
• Automatically configures the Temporal sandbox to pass through LangGraph/LangChain modules

Details

New files:

• langgraph_plugin.py — LangGraphPlugin (extends SimplePlugin) that registers graph nodes/tasks as Activities and configures the sandbox runner
• activity.py — Activity wrappers that serialize/deserialize LangGraph config and handle GraphInterrupt
• langgraph_config.py — Helpers to get/set LangGraph's internal RunnableConfig (checkpoint namespace, scratchpad) across the workflow-activity boundary
• task_cache.py — Content-addressed cache keyed by (task_id, args, kwargs) hash for deduplicating work across continue-as-new
• README.md — Usage documentation with examples for both Graph and Functional APIs

Tests cover: two-node graphs, subgraphs (as activities and workflows), interrupts, streaming, timeouts, continue-as-new (with and without caching), execute-in-workflow mode, and full end-to-end functional API workflows.

Test plan

• uv run pytest tests/contrib/langgraph/ — all 12 test files pass

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[Copilot]

Pull request overview

Adds a new temporalio.contrib.langgraph integration to run LangGraph Graph/Functional API nodes/tasks as Temporal Activities (with retries/timeouts), including continue-as-new caching and interrupt propagation, plus an accompanying test suite.

Changes:

• Introduces LangGraphPlugin + activity/config/cache plumbing for executing LangGraph nodes/tasks via Temporal Activities and supporting interrupts + continue-as-new deduping.
• Adds a new langgraph optional extra and locks required LangGraph/LangChain dependencies.
• Adds an end-to-end test suite covering graphs, subgraphs, interrupts (v1/v2), streaming, timeouts, execute-in-workflow, and continue-as-new caching.

Reviewed changes

Copilot reviewed 22 out of 24 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
uv.lock	Locks new LangGraph/LangChain-related dependencies and adds langgraph extra entries.
pyproject.toml	Adds langgraph optional dependency and dev dependency.
temporalio/contrib/langgraph/init.py	Exposes LangGraphPlugin, graph, entrypoint, and cache public API.
temporalio/contrib/langgraph/langgraph_plugin.py	Implements the plugin: registers activities, sandbox passthrough, and graph/entrypoint accessors.
temporalio/contrib/langgraph/activity.py	Activity wrappers for config propagation, interrupt handling, and cache-aware execution.
temporalio/contrib/langgraph/langgraph_config.py	Serializes/deserializes LangGraph runnable config (checkpoint namespace/scratchpad) across workflow/activity boundary.
temporalio/contrib/langgraph/task_cache.py	Implements a content-addressed task result cache for continue-as-new deduplication.
temporalio/contrib/langgraph/README.md	Documents installation and usage for Graph/Functional APIs and activity options.
tests/contrib/langgraph/init.py	Adds test package marker for the new test suite.
tests/contrib/langgraph/conftest.py	Provides langgraph-specific Temporal test environment and client fixtures.
tests/contrib/langgraph/test_two_nodes.py	Verifies basic two-node graph execution via activities.
tests/contrib/langgraph/test_timeout.py	Verifies activity timeout behavior is enforced through node metadata.
tests/contrib/langgraph/test_subgraph_workflow.py	Verifies subgraph execution with execute_in="workflow".
tests/contrib/langgraph/test_subgraph_activity.py	Verifies subgraph execution inside an activity node.
tests/contrib/langgraph/test_streaming.py	Verifies streaming (astream) behavior across activity-wrapped nodes.
tests/contrib/langgraph/test_interrupt.py	Verifies v1 interrupt propagation and resume semantics.
tests/contrib/langgraph/test_interrupt_v2.py	Verifies v2 interrupt semantics (GraphOutput.value/.interrupts) and resume.
tests/contrib/langgraph/test_execute_in_workflow.py	Verifies execute_in="workflow" bypasses activity wrapping.
tests/contrib/langgraph/test_continue_as_new.py	Verifies continue-as-new with LangGraph checkpointer state restoration.
tests/contrib/langgraph/test_continue_as_new_cached.py	Verifies continue-as-new caching prevents re-execution across continuations.
tests/contrib/langgraph/test_e2e_functional.py	End-to-end functional API workflows (including continue-as-new + partial execution scenarios).
tests/contrib/langgraph/test_e2e_functional_v2.py	End-to-end functional API workflows using version="v2" GraphOutput.
tests/contrib/langgraph/e2e_functional_entrypoints.py	Defines functional @task/@entrypoint implementations used by E2E tests.
tests/contrib/langgraph/e2e_functional_workflows.py	Defines Temporal workflow wrappers used by functional API E2E tests.

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