head to head · open source
haystack vs workflow-core
haystack has 26,559 GitHub stars, 3,153 forks, 143 open issues and last shipped yesterday. workflow-core has 5,926 stars, 1,262 forks, 133 open issues and last shipped 4 days ago. haystack leads on adoption by 348% (26,559 vs 5,926 stars). haystack is written in Python under Apache-2.0; workflow-core is written in C# under MIT. haystack has attracted 12% as many forks as stars, workflow-core 21%. haystack was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| haystack | workflow-core | |
|---|---|---|
| GitHub stars | ★ 27K | ★ 5.9K |
| License | Apache-2.0 | MIT |
| Written in | Python | C# |
| Last push | 2026-09-19 | 2026-09-16 |
| Forks | ⑂ 3.2K | ⑂ 1.3K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick haystack if
- You weight community size — 27K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick workflow-core if
- You want the workflow-core feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches C#
- You evaluated both and workflow-core fits your workflow better
About haystack
Haystack is an open source AI orchestration framework written in Python under the Apache 2.0 licence, for building context engineered, production ready large language model applications as modular pipelines and agent workflows with explicit control over retrieval, routing, memory, and generation, and it is aimed at developers and teams building scalable agents, retrieval augmented generation, multimodal applications, semantic search, question answering, and conversational systems.
read the full haystack overview →
About workflow-core
Workflow Core is a lightweight, embeddable workflow engine targeting .NET Standard, written in C and released under the MIT license. It lives in the .NET ecosystem, distributed as NuGet packages, and is built around the idea of long running processes that contain multiple tasks and must track their state between steps. Rather than running as a separate server, it is a library that is hosted inside an application, and it exposes a fluent C API for defining workflows. Workflows are expressed as a starting step followed by chained steps, and the same class can declare inputs and outputs that move data from one step …
read the full workflow-core overview →
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Frequently asked questions
Is haystack or workflow-core more popular?
haystack has 26,559 GitHub stars and workflow-core has 5,926. haystack has the larger community by that measure.
Are haystack and workflow-core free?
Both are open source. haystack is licensed under Apache-2.0 and workflow-core under MIT. Neither carries a licence fee.
What is the difference between haystack and workflow-core?
haystack is written in Python and workflow-core in C#. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, haystack or workflow-core?
Choose haystack if you want the larger community (26,559 stars) or its Apache-2.0 licence terms. Choose workflow-core if its feature set, stack or MIT licence fits better. Both are self-hostable.