Collection

Open Source AI Agent Tools (2026)

We compare 26 open source AI agent tools as of October 2026. 26 have a free plan.

Updated 24 October 2026

Prices checked 12 September–24 October 2026

Reviewed by The Agents Index editorial team.

On this page

At a glance
The 26 agents
Browse the full categories
Sources and method
Where next

The 26 tools in our index with a clean, unrestricted OSI-style license (MIT, Apache-2.0, GPL-3.0-or-later or AGPLv3) — free to fork, self-host and run forever, no source-available caveats and no proprietary layer gating the part you would actually run.

We checked the license behind all 188 tools in our index and found 33 that call themselves open source in some form, but only 26 clear the bar of a clean, unrestricted license with no strings attached. This collection is those 26: the tools you can fork today, self-host forever, and keep running even if the vendor disappears, with nothing held back behind a separate commercial tier.

At a glance

agents: 26
Free to start: 26 of 26; free plan or freemium
Public API: 22 of 26; 3 more only on a paid tier
Public pricing: 26 of 26; price on their own site

What this collection covers

The other seven "open" tools don't make this list, and that's deliberate: n8n and Dify both hedge their openness with a license condition their own docs tell you to check (fair-code, added-conditions Apache), Mastra and OpenHands are open at the core but gate their enterprise controls behind a separate paid license, Sim is open-source at the code level (29.4k GitHub stars) but sells self-hosting itself only on its Enterprise tier, and Warp and Claude Agent SDK each open-source only one half of the product: Warp's terminal client (AGPL-3.0/MIT) while its Oz cloud-agent platform stays closed, and the Agent SDK's two wrapper packages (MIT) while the Claude Code CLI binary they spawn as a subprocess is never published as source. Junie isn't part of that "hedged open" group either. It's simply closed-source, with no public repository at all. Real, legitimate business models, just not a "no caveats" self-hosting story. See our full license census for the complete breakdown, caveats included.

This list isn't the same set as our [self-hostable collection](/collections/ai-agent-tools-you-can-self-host/), even though the two overlap heavily. 24 of these 26 tools also appear there. Cartesia and Kilo Code are the two exceptions. Cartesia's Apache-2.0 Line SDK is unconditionally open but its voice runtime only ever runs on Cartesia's own infrastructure. Kilo Code was added to this collection on 2026-08-18, the same day it was published, and the self-hostable collection has not yet been re-read to include it. That collection also counts 13 tools that don't clear this one's bar: Mastra, Claude Agent SDK, n8n and Dify carry a license condition on an otherwise-open core, and Augment Code, Factory, CodeRabbit, Bland AI, Deepgram Voice Agent API, Windsurf, Warp, OpenHands and Junie are closed-source products that still sell a real self-hosted or on-prem path. If what you actually need is "can I run this myself," check that collection instead.

What it takes to be on this list

A tool earns a place here only if its entire self-hostable codebase carries a clean, unrestricted OSI-style license (MIT, Apache-2.0, GPL-3.0-or-later, or AGPLv3) with no source-available carve-out, no fair-code condition, and no proprietary enterprise layer gating the part you'd actually run. Verified against each tool's own GitHub license file or our sourced listing research, not a vendor's marketing claim of "open source."

We distinguish an open core from the complete runnable product: a hosted control plane, closed runtime, source-available restriction, fair-code clause, or paid license for self-hosting excludes the listing even when part of its repository is public. Each refresh rechecks the license identifier, repository scope, self-hosting path and whether the licensed code is sufficient to operate the product independently of the vendor.