Constitution vs AGENTS.md, copilot-instructions.md, CLAUDE.md, etc

[mikedane-bitovi]

I've seen this discussed a couple times before but the answers never really addressed my main concern. I don't really see a difference between the constitution in spec-kit and any of the other "context" files that are supported by the leading agent frameworks (AGENTS.md, copilot-instructions.md, CLAUDE.md, etc)

Are these files serving the same purpose? If so why do we need to constitution at all, it seems to me that including it just means that now we all need to keep our agent specific context files and the constitution in sync, which violates DRY principles outright.

So what exactly is the purpose of the constitution, and what are the best practices for using it in combination with the other context files? And tbh if the answer is "Just have the constitution point to your AGENTS.md" or vice versa, that seems completely unnecessary. Context engineering is becoming more and more important and a lot of care is placed in curating the right AGENTS.md/copilot instructions, so how does the constitution file fit into that process?

[mnriem]

The constitution file is loaded on-demand by the commands for establishing context and it does not mean it will always need the entire file. Whereas AGENTS.md, copilot-instructions.md, CLAUDE.md get sent with every request to the LLM irrespective of the context at hand

[mikedane-bitovi]

But how does that differ from something like skills, which are also loaded on demand?

I understand the mechanics of how it's loaded, but my question is more about the overlap in content. What specifically should go in the constitution vs the agent instructions files vs skills? Or should the constitution link to the other files?

Every time I generate a constitution file using spec-kit, the agent basically just replicates what's in the AGENTS.md file

[mnriem]

AGENTS.md is for how the agent is allowed to operate and what it can or cannot do and is dependent on your coding agent. Constitution are principles irrespective of that

[mikedane-bitovi]

Can you elaborate, please? That doesn't really answer my question...

According to the official AGENTS.md website the AGENTS.md file is

a dedicated, predictable place to provide the context and instructions to help AI coding agents work on your project.

In my experience, these files are for more than just telling the agent how it's allowed to operate; they provide information about project architecture, folder structure, dependencies, patterns, project scripts, and workflows. Basically, provide a high-level view of the environment the agent is operating in. I don't think the primary intention of AGENTS.md or CLAUDE.md or copilot-instrictions.md is to say what the agent is "allowed" to do...

When you say "Constitution are principles irrespective of that" can you be more percise? That seems to indicate that the Constitution should include everything other than what the agent is allowed to do?

I don't mean to be a pain here, just trying to understand. I teach spec-kit in trainings all the time, and by far the most common confusion among experienced developers is this. I'm not sure your answer really hit the mark