chore: add claude.md and agents.md

[MounirDhahri]

Description

In this PR, I am adding AGENTS.md and CLAUDE.md files to make AI tools more efficient inside Eigen.

How was this built?

1. Gathered best practices

Sources:
https://www.builder.io/blog/claude-md-guide
https://skills.sh/mounirdhahri/skills/agentsmd-claudemd-generator
https://acjay.com/2026/02/18/the-ai-landslide-is-happening/
https://agents.md/
Force agents.md https://github.com/artsy/force/blob/main/AGENTS.md
https://code.claude.com/docs/en/memory

2. Combined best practices into a skill

Using the above files and docs, I generated a skill to generate a CLAUDE.md and AGENTS.md skill that we can use in our repos

3. Manually review that it makes sense and that it follows our best practices and the community best practices. Mainly:

• import AGENTS.md inside CLAUDE.md
• reference docs instead of copying them
• Prefer docs over what's in the folders (double edged sword)
• Warn about context window
• ...

4. Published the skill (maybe it's useful to someone else)

I published the skill here https://skills.sh/mounirdhahri/skills/agentsmd-claudemd-generator and installed it to generate the docs

5. Used the skill to generate AGENTS.md and CLAUDE.md inside Eigen.

6. Review generated docs and update the skill accordingly

What will be the impact of this on the context window?

Source	Lines	Est. Tokens	% of 200k context
AGENTS.md (without import)	103	~1,200	0.6%
best_practices.md (imported)	444	~4,500	2.3%
Total loaded per conversation	547	~5,700	~2.9%

~5,700 tokens on every conversation. That's still small — leaves ~194k tokens for actual work. For a file you'd want agents to reference on nearly every code change, that's a reasonable trade imo

If it ever feels too much, we can still reference best_practices.md for example instead of importing it using @import

PR Checklist

• I have tested my changes on the following platforms:
  • Android.
  • iOS.
• I hid my changes behind a feature flag, or they don't need one.
• I have included screenshots or videos at least on Android, or I have not changed the UI.
• I have added tests, or my changes don't require any.
• I added an app state migration, or my changes do not require one.
• I have documented any follow-up work that this PR will require, or it does not require any.
• I have added a changelog entry below, or my changes do not require one.

To the reviewers 👀

• I would like at least one of the reviewers to run this PR on the simulator or device.

Changelog updates

Changelog updates

Cross-platform user-facing changes

iOS user-facing changes

Android user-facing changes

Dev changes

• add Agents.md and Claude.md files - mounir

Need help with something? Have a look at our docs, or get in touch with us.

[ArtsyOpenSource]

This PR contains the following changes:

• Dev changes (add Agents.md and Claude.md files - mounir - MounirDhahri)

Generated by 🚫 dangerJS against 8f57dbe

[anandaroop]

lgtm, just confirming one question below

[anandaroop]

The @ will immediately pull the linked doc (~4k tokens) into the context.

Just confirming that's what you want for best practices (as opposed to the further docs below, which will be progressively disclosed as needed)?

[MounirDhahri]

Yes, that’s intentional. I did the math here and found the additional tokens would lead to 2% extra in the window size (assuming 200k size) but would make sure that the best practices are always respected. I initially wrote the best docs in a short format compared to the main best practices docs, but this would mean that we need to maintain parity. So for the time being, I guessed because it’s not a problem, yet, I will do the easy route