Techniques
These files disagree about almost everything, including how long an AGENTS.md should be. Ghostty gets it done in 39 lines; herdr takes 317. But the same moves keep turning up, and those are the transferable part: one file teaches you about one repo, these apply to yours.
Roughly easiest to adopt first. Each one lists the projects in the directory that use it.
Hard prohibitions
A short list of actions the file states the agent must never take, without hedging.
Stated as flat "never" rather than "prefer not to", and usually naming the exact action rather than a category. Several files pair the rule with what to do when a user asks anyway.
12 of 16 projects
and 6 more
Good and bad pairs
A style rule is shown with the wrong version beside the right one.
Some files pair whole code blocks, others contrast inline within a sentence. The rule is stated once and then demonstrated twice, which removes the judgement call at the margins.
2 of 16 projects
Generated file guards
Generated files are named, along with the generator to run instead.
The lists are explicit paths rather than a description of what generated files look like. Several entries also name the command and, in a few cases, the extra steps that have to happen in the same change, such as deleting a superseded fixture.
5 of 16 projects
Verification by change type
The kind of change is mapped to the specific checks that cover it.
A rendering change maps to one command, a protocol change to another. Several files also state what the default test command leaves out, which is otherwise discoverable only by finding the gap.
9 of 16 projects
and 3 more
Nested instruction files
Per-package AGENTS.md files, with a stated order of precedence.
The root file covers repository-wide navigation and defers subsystem detail to a file next to the code. Where the files could conflict, the precedence order is written down rather than left to the agent.
5 of 16 projects
Pointing at the source of truth
The file refuses to copy values that live somewhere authoritative.
Version numbers, rule lists and counts are replaced with a pointer to the config, script or array that defines them. Some files state the reason directly: a copied value drifts from the thing it copied.
6 of 16 projects
Router files
The entry file dispatches to deeper task guides rather than containing them.
A short index maps a kind of work to the guide to read before starting it. The deeper document is loaded when the task touches that subsystem, instead of on every request.
5 of 16 projects
Behavioral framing
Rules about how to approach the work rather than facts about the repository.
Surface tradeoffs, do not over-build, touch only what was asked. Two files state outright that these sections were written from recurring mistakes in agent-authored changes to that repo.
7 of 16 projects
and 1 more
House vocabulary
Specific words the project does and does not use, defined once.
Ranges from fixing the spelling of a domain term across all prose, to defining the difference between two near-synonyms, to listing individual words that may not appear. Naming drift is hard to catch in review, which is what these rules are aimed at.
5 of 16 projects
Architecture as narrative
How the system works, written out, rather than a list of rules about it.
Request lifecycles, data flows and component boundaries. It lets the agent derive an answer for a case the file does not cover, at the cost of length.
4 of 16 projects
Ratchets
Baselines that may only shrink and lists that may only grow.
A known-violations file, a lint warning count, or a tombstone list, each with a direction of travel stated in the file and usually enforced in CI.
3 of 16 projects
Contribution etiquette
Rules for what the agent may open, push or post on the project's behalf.
Covers pull requests, issues, @-mentions and commit trailers. Two of these files give the reason as agent traffic specifically: unsolicited pull requests, and issues that attract duplicate work from other agents.
3 of 16 projects
Scope layering
Different rules for different actors, with a test for which set applies.
One file covers maintainers, external contributors and forks, and states how the agent determines which it is before the rules take effect.
1 of 16 projects
Context budgeting
Rules governing what may enter the model context, with size caps.
Appears in repos that build agents. The context window is treated as a resource with an owner, a cap per item, and a review threshold.
1 of 16 projects
Context your AGENTS.md cannot carry
These techniques tell an agent how your codebase works. None of them can tell it which bug three customers hit this week. Modem keeps that context current and attaches it to the work.