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Sim vs Vellum

Sim and Vellum, side by side — the researched facts from the index.

How Sim and Vellum compare

FeatureSimVellum
DescriptionOpen-source AI workspace for building, deploying, and managing AI agents with a Knowledge Base, Tables, and a full REST APIA personal AI assistant with persistent memory, built-in skills, and phone/voice access, hosted in the cloud or self-hosted.
Pricing$0 / forever$0 / month
TagsAPIEnterpriseFree tierOpen sourceSelf-hostedAPIAutonomousBrowser useFree tierOpen sourceSelf-hosted
Pricing modelfreemiumfreemium
Free tierYesYes
Model / LLMSupports every major LLMMultiple model providers via pass-through credits billed at cost, no markup on token usage
InterfaceWebWeb
Public APIYesYes
Open sourceYesYes
DeploymentBothBoth
Limitations
  • Self-hosting, SSO, and SOC2 compliance are gated to the Enterprise plan, so Free, Pro, and Max users cannot self-host
  • The vendor's own site states two different integration counts (1,000+ in navigation versus 244 on the integrations page), making real coverage hard to verify
  • Free plan log retention is capped at 30 days versus unlimited retention on paid plans
  • Pricing is layered across preset packages, a Custom configuration with separate machine, storage, and credit-bundle costs, and a $10/mo platform fee that applies only to some tiers, which makes total cost harder to estimate upfront.
  • Independent write-ups of Vellum's pricing disagree on the plan names, prices, and even the product's shape (one third-party source describes prompt/workflow execution limits and a $500/mo Pro tier that don't match the vendor's current Base/Mighty/Super/Ultra structure), suggesting the offering has changed and stale information is circulating.
  • Granting phone-calling, screen-control, and browser-extension access to a persistent-memory assistant raises a larger trust surface than a conventional chatbot, even with permission prompts in place.

Who each one is for

Sim

Dev teams wanting an open-source, API-first workspace to build and deploy AI agents

From $0 / forever

The digest

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