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vellum-workflow-server

library1.14.7pypypiunverified

The Vellum Workflow Server is a Python library for building and hosting AI workflows. It provides a framework to define, execute, and serve complex LLM-based pipelines with features like node-based DAGs, retries, observability, and API endpoints. Current version: 1.14.7. Release cadence: frequent updates (weekly/biweekly). Requires Python >=3.9, <4.

llm-agents ai-ml workflow

pip install vellum-workflow-server

package ↗homepage ↗

INSTALL

IMPORT

SIG · VELLUM-WORKFLOW-SE

vellum-workflow-server

llm-agentspythonv1.14.7

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Workflow

✓ from workflow_server import Workflow

✗ from vellum_workflow_server import Workflow

Defines a simple workflow with input, prompt (GPT-4), and output nodes, then executes it.

from vellum_workflow_server import Workflow from vellum_workflow_server.nodes import PromptNode, InputNode, OutputNode import os workflow = Workflow() input_node = InputNode(name="input") prompt_node = PromptNode( name="prompt", prompt_template="Hello {{ input.text }}", model="gpt-4", api_key=os.environ.get("OPENAI_API_KEY", "") ) output_node = OutputNode(name="output") workflow.add_node(input_node) workflow.add_node(prompt_node, depends_on=[input_node]) workflow.add_node(output_node, depends_on=[prompt_node]) result = workflow.run(input={"text": "world"}) print(result)

Debug

Known issues

breakingLibrary was renamed from 'vellum' to 'vellum-workflow-server' in v2.0. Old 'pip install vellum' installs a different package. Must update imports and dependencies.

fix

Replace 'from vellum import ...' with 'from vellum_workflow_server import ...'. Also update requirements.txt.

affects: <2.0.0

gotchaAPI keys must be set via environment variables or passed explicitly. The library does not auto-read .env files.

fix

Use os.environ.get('VARIABLE_NAME') or set keys in code (not recommended for production).

affects: >=1.0.0

deprecatedNode base class 'Node' is deprecated in favor of specific node types (e.g., PromptNode, CodeNode). Direct subclassing of Node may break in future releases.

fix

Use provided node classes or extend their subclasses.

affects: >=1.10.0

gotchaWorkflow.run() is synchronous and blocking. For async execution, use Workflow.arun() but requires async environment.

fix

For async, ensure event loop is running and use await workflow.arun().

affects: >=1.0.0

Upgrade

Version history

1.14.7latest on PyPI · released Mar 5, 2026

Audit

Dependencies

vellumrequiredCore SDK for Vellum API interactions

Agent activity

42 hits · last 30 days

node

OpenAI (training)

Resources

packagehttps://pypi.org/project/vellum-workflow-server/ ↗

homepagehttps://vellum.ai ↗