Open Core

Open-source the framework so anyone can build with it and own it; charge for the hosted, integrated, pre-configured version for everyone who'd rather not assemble it. The open core isn't a giveaway — it's distribution.

The model

Open-core splits a product into two layers:

• The core (open source, free). The framework/engine — MIT or Apache, self-hostable. The user owns what they build, no lock-in. This is the credibility and distribution layer.
• The shell (paid, hosted). Deployment, integrations, configuration, governance, observation, and support — the assembly a buyer would otherwise do themselves. This is the revenue layer.

You make money not by gating the core capability but by selling the convenience and completeness around it: one-click hosting, integrations already wired, configs already chosen, the compliance/SSO/audit a team needs, and someone to call.

Why it works

The apparent paradox — "if it's open source, why will anyone pay?" — dissolves once you see the open core as distribution, not a giveaway:

• Builders who'd assemble it themselves can — and they become advocates, contributors, and the top of the funnel. (This is Build, Don't Buy from the user's side: build it yourself if that's your thing.)
• Everyone who'd rather not pays to skip the assembly. The afternoon of setup — wiring integrations, choosing configs, standing up hosting — is exactly what the hosted tier removes.
• Trust and no lock-in lower the barrier to adopt. Open code is auditable and portable, so the buyer commits more easily; the real switching cost accrues later in the hosted data, observation, and configuration.
• The open core is the cheapest distribution channel there is — GitHub, Show HN, integrations, ecosystem contributions (Distribution Is the Moat).

Examples

Source: User, 2026-06-15; reflex.dev/pricing + /enterprise, 2026-06-15; loop/README.md, 2026-06-13

Kevin's portfolio instantiates the model directly: the projects he builds to avoid buying SaaS (Build, Don't Buy) ship as open frameworks and monetize the hosted assembly. Sigil UI is MIT today (open core without a paid tier yet); Loop and Agent Machines already pair an open core with a paid hosted tier.

Open-core vs services-as-software

Different monetization shapes, often confused:

• Open-core sells the assembled tool — you still operate it (deploy the worker, run the app). Margin is hosting + integrations + governance.
• Services-as-Software sells the outcome/labor — the agent does the job; you buy the result. Margin widens as models improve.

They compose: Agent Machines is open-core today (you operate the worker), and its endgame — agents that deliver outcomes — edges toward services-as-software. Open-core funds distribution now; outcome-pricing is the deeper margin later.

Anti-patterns

• Gating the core capability so the "open" version is a crippled demo — kills trust and the distribution flywheel.
• Open-sourcing the differentiated/compounding layer instead of the commodity framework — give away the framework, keep the hosted data/observation/registry stickiness.
• Charging for what's trivial to self-host rather than for the assembly people actually don't want to do.
• Treating open source as a marketing checkbox without a hosted product that captures the value.

Concept Position

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Timeline

• 2026-07-01 | Concepts category refresh added this page to the Agent harness and runtime primitives family, linked it to Concept System Map, and kept it standalone because it owns this reusable mental model: Open-source the framework so anyone can build with it and own it; charge for the hosted, integrated, pre-configured version for everyone wh... Source: User request, 2026-07-01
• 2026-06-15 | Page created from Kevin's framing linking Build, Don't Buy to Agent Machines: open-source the persistent-agent framework, charge for hosted machines/agents with integrations + configs built in — the Reflex model. Source: User, 2026-06-15