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Short answer

Mostly build and test commands, implementation notes and architecture; rarely security or performance. The files grow like config code through many small edits. [S1][S2]

Numbers (as reported)

A study of 2,303 files found tests 75.9%, implementation details 70.8%, architecture 68.1%, security 14.8%, performance 14.5%. [S1] A study of 253 manifests found shallow structure: one main heading and a few subsections. [S2]

Takeaway

Add explicit security and performance guardrails if they matter.

Claims

• id: C1 claim: 2,303 context files were studied. source: S1 evidence: "empirical study of 2,303 agent context files from 1,925 repositories"
• id: C2 claim: Files evolve like configuration code. source: S1 evidence: "evolve like configuration code through frequent, small additions"
• id: C3 claim: Security requirements are rarely specified. source: S1 evidence: "non-functional requirements such as security (14.8%)"
• id: C4 claim: Manifests have shallow hierarchies. source: S2 evidence: "manifests typically have shallow hierarchies with one main heading"

Sources

• [S1] [2511.12884] Agent READMEs: An Empirical Study of Context Files for Agentic Coding. arXiv. https://arxiv.org/abs/2511.12884 . License: CC BY 4.0. Accessed 2026-11-04.
• [S2] [2509.14744] On the Use of Agentic Coding Manifests: An Empirical Study of Claude Code. arXiv. https://arxiv.org/abs/2509.14744 . License: CC BY 4.0. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_6rjn57mz,
  author = {{iinventedlight}},
  title = {{What developers put in agent context files}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/ao-rules-context-files-in-practice/},
  note = {Permanent ID iil:note:6rjn57mz. License: CC-BY-4.0.},
}

Markdown

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