--- title: "pythia vs hallucination-index" type: "comparison" canonical_url: "https://www.graphcanon.com/compare/eleutherai-pythia-vs-rungalileo-hallucination-index" tools: ["eleutherai-pythia", "rungalileo-hallucination-index"] --- # pythia vs hallucination-index *GraphCanon updated Aug 7, 2026* ## Verdict Pick pythia if pythia is a hub maintained by EleutherAI focused on research notebooks addressing interpretability and learning dynamics; pick hallucination-index if hallucination-Index helps users identify LLMs with the lowest propensity for factual errors across varying context lengths and source types. [pythia](https://github.com/EleutherAI/pythia) reports 2.9k GitHub stars, 222 forks, and 26 open issues, last pushed Nov 15, 2025. [hallucination-index](https://www.rungalileo.io/hallucinationindex) has 116 stars, 8 forks, and 1 open issues, last pushed Jul 28, 2025. Figures are from public GitHub metadata via [pythia's repository](https://github.com/EleutherAI/pythia) and [hallucination-index's repository](https://github.com/rungalileo/hallucination-index). | | [pythia](/tools/eleutherai-pythia.md) | [hallucination-index](/tools/rungalileo-hallucination-index.md) | | --- | --- | --- | | Tagline | Hub for EleutherAI's work on interpretability and learning dynamics | Initiative to evaluate and rank popular LLMs based on hallucination propensity | | Stars | 2,872 | 116 | | Forks | 222 | 8 | | Open issues | 26 | 1 | | Language | Jupyter Notebook | - | | Adopt for | Pythia is a hub maintained by EleutherAI focused on research notebooks addressing interpretability and learning dynamics. | Hallucination-Index helps users identify LLMs with the lowest propensity for factual errors across varying context lengths and source types. | | Persona | - | - | | Runtime | - | - | | License | The repository's content is licensed under Apache-2.0, which allows for a broad range of uses including both commercial and non-commercial purposes while requiring preservation of copyright notices. | - | | Categories | Evaluation & Observability | Evaluation & Observability | ## Trust and health _Sourced signals - not a safety guarantee. No winner column._ | | [pythia](/tools/eleutherai-pythia.md) | [hallucination-index](/tools/rungalileo-hallucination-index.md) | | --- | --- | --- | | Maintenance | Slowing (36%) | Dormant (18%) | | Days since push | 264d | 365d | | Open issues (now) | 26 | 1 | | Full report | [trust report](/tools/eleutherai-pythia/trust.md) | [trust report](/tools/rungalileo-hallucination-index/trust.md) | ## Decision facts: pythia - **Pricing:** freemium - All code in the GitHub repo, Pythia models, and other artifacts are available under an open-source Apache-2.0 license, making it free to use with attribution. - **Adopt for:** Pythia is a hub maintained by EleutherAI focused on research notebooks addressing interpretability and learning dynamics. - **License detail:** The repository's content is licensed under Apache-2.0, which allows for a broad range of uses including both commercial and non-commercial purposes while requiring preservation of copyright notices. ## Decision facts: hallucination-index - **Adopt for:** Hallucination-Index helps users identify LLMs with the lowest propensity for factual errors across varying context lengths and source types. ## Choose when ### Choose pythia if… - Pricing: All code in the GitHub repo, Pythia models, and other artifacts are available under an open-source Apache-2.0 license, making it free to use with attribution.. - Tags unique to pythia: interpretability, learning dynamics, research. - When you are specifically interested in understanding the internal workings and behavior of AI models, as Pythia is centered around interpretability and learning dynamics. ### Choose hallucination-index if… - Tags unique to hallucination-index: hallucinations, large language models, llm-evaluation, openai. - Use when you need to ensure accuracy in short-context tasks, as it tests models like Chain-of-Note prompting techniques specifically for such scenarios. - Leaner open-issue backlog (1). ## When NOT to use pythia - Avoid using Pythia if you need specific applications or tools for immediate practical AI model deployment, as it primarily focuses on research and not direct application. - If interpretability is not a prime focus of your project and the primary goal is building functional machine learning models without delving into theoretical aspects. ## When NOT to use hallucination-index - Avoid using Hallucination-Index when your application requires real-time evaluation of hallucinations, as it focuses on predefined tests rather than live model performance. - Do not rely solely on this index if your primary concern is the latest updates to LLM models; its data might not reflect recent improvements in models or the introduction of new ones. ## Common questions ### What is the difference between pythia and hallucination-index? pythia: Hub for EleutherAI's work on interpretability and learning dynamics. hallucination-index: Initiative to evaluate and rank popular LLMs based on hallucination propensity. See the comparison table for live GitHub stats and shared categories. ### When should I choose pythia over hallucination-index? Choose pythia over hallucination-index when Pricing: All code in the GitHub repo, Pythia models, and other artifacts are available under an open-source Apache-2.0 license, making it free to use with attribution.; Tags unique to pythia: interpretability, learning dynamics, research; When you are specifically interested in understanding the internal workings and behavior of AI models, as Pythia is centered around interpretability and learning dynamics. ### When should I choose hallucination-index over pythia? Choose hallucination-index over pythia when Tags unique to hallucination-index: hallucinations, large language models, llm-evaluation, openai; Use when you need to ensure accuracy in short-context tasks, as it tests models like Chain-of-Note prompting techniques specifically for such scenarios; Leaner open-issue backlog (1). ### When should I avoid pythia? Avoid using Pythia if you need specific applications or tools for immediate practical AI model deployment, as it primarily focuses on research and not direct application. If interpretability is not a prime focus of your project and the primary goal is building functional machine learning models without delving into theoretical aspects. ### When should I avoid hallucination-index? Avoid using Hallucination-Index when your application requires real-time evaluation of hallucinations, as it focuses on predefined tests rather than live model performance. Do not rely solely on this index if your primary concern is the latest updates to LLM models; its data might not reflect recent improvements in models or the introduction of new ones. ### Is pythia or hallucination-index more popular on GitHub? pythia has more GitHub stars (2,872 vs 116). Stars measure visibility, not whether either tool fits your constraints. ### Are pythia and hallucination-index open source? Yes - both are open-source projects on GitHub. ### Where can I find alternatives to pythia or hallucination-index? GraphCanon lists graph-backed alternatives at [pythia alternatives](/tools/eleutherai-pythia/alternatives) and [hallucination-index alternatives](/tools/rungalileo-hallucination-index/alternatives) ([pythia markdown twin](/tools/eleutherai-pythia/alternatives.md), [hallucination-index markdown twin](/tools/rungalileo-hallucination-index/alternatives.md)), ranked by typed relationship edges rather than popularity votes. ### Is there a machine-readable version of this comparison? Yes. The markdown twin at [this comparison](/compare/eleutherai-pythia-vs-rungalileo-hallucination-index.md) mirrors this page for agents and LLM crawlers, with the same stats table and FAQ answers. ### Which is better maintained, pythia or hallucination-index? pythia: Slowing. hallucination-index: Dormant. Compare maintenance labels, days since push, and release cadence in the trust section below - stars alone do not measure maintenance. ### Where are the full trust reports for pythia and hallucination-index? GraphCanon publishes per-repo trust reports with dated maintenance, provenance, and scan summaries: [pythia trust report](/tools/eleutherai-pythia/trust); [hallucination-index trust report](/tools/rungalileo-hallucination-index/trust). --- **Machine-readable endpoints** - JSON: [`/api/graphcanon/graph?tool=eleutherai-pythia`](/api/graphcanon/graph?tool=eleutherai-pythia) - LLM index: [/llms.txt](/llms.txt) - Full corpus: [/llms-full.txt](/llms-full.txt) _GraphCanon - The knowledge graph for AI development. https://www.graphcanon.com/_