Mod
A change or addition that alters or extends the functionality of existing software, like custom instructions for AI agents.
A mod is a modification or an add-on. It changes or adds to how a program works.
For example, imagine an AI assistant. A mod could be a set of custom instructions you give it to make it better at a specific task, like writing code for a particular project. This changes the AI's behavior without altering its core programming.
A mod is a modification or extension that alters or enhances the functionality of existing software. In the context of frontier AI, this often refers to user-defined configurations, prompts, or agent instructions that steer a base model's behavior towards specific tasks or styles without retraining the model itself.
These mods leverage the model's existing capabilities, directing its output through carefully crafted inputs. The tradeoff is that they are limited by the base model's inherent knowledge and abilities, unlike fine-tuning which alters the model's weights.
Anthropic's Claude Code now allows users to define custom agent instructions. This feature acts as a mod, letting users alter the AI's behavior for specific coding tasks. This points to a growing trend of making AI models more adaptable and customizable for individual workflows.
- Quoting Thariq ShihiparAnthropic · Simon Willison ·
- Anthropic Claude
- Anthropic's Claude Code allows users to define custom agent instructions, which function as mods to tailor the AI's behavior for specific coding projects.
- Fine-tuning
- Fine-tuning retrains a model on new data to alter its core weights,
- Plugins
- Plugins are external tools that an AI can call upon, whereas mods are u
- System Prompt
- A system prompt is a set of instructions given to an AI, similar
The term 'mod' originated in the video game community, referring to user-created modifications to games. It has since been adopted more broadly in software development to describe any alteration or addition to existing software.
Go to Anthropic's Claude Code. Try giving it a custom instruction like 'Act as a senior Python developer specializing in data analysis. Prioritize clear, well-commented code and use pandas for all data manipulation tasks.' Then, ask it to write a simple script to read a CSV file and calculate the average of a column.
The Playbook: reusable how-tos, prompts, configs and tips pulled out of the news.
- PromptRole-play a student struggling with math for AI tutor simulationSimulate a student's math struggles and uncertainty for AI tutor evaluation. · 5 min
- TemplateReusable workflow templates for healthcare teamsTeams can create and share templates for common workflows like documentation or prior authorizations. · 15 min
- TemplateTemplate for building an AI tool tailored to your workA structured approach to defining and building a custom AI tool for specific business needs. · 15 min
- TemplateEvals CSV prompt list for agent skillsA CSV file template for listing prompts used in evaluating agent skills. · 20 min
- HeuristicDouble coding agent task completion with docs linksProviding coding agents with a documentation link significantly increases their task completion rate. · 2 min
Questions people ask
- Are mods the same as fine-tuning?
- No, mods typically guide an existing model's behavior through instructions or configurations, while fine-tuning involves retraining the model on new data to change its underlying capabilities.
- Can mods add new features to an AI?
- Mods can make an AI *behave* as if it has new features by directing its existing abilities in novel ways, but they don't add fundamentally new underlying functions to the AI itself.
First seen on Subvolts Sep 18, 2026. Updated Sep 25, 2026. Written by an AI model from the items above and reviewed against them weekly; report an error.