# agents-md

`AGENTS.md` read the way Claude Code reads `CLAUDE.md`, as a plugin, under
one option, `instructionFiles`:

- `claude-md`: only `CLAUDE.md` is loaded, by the engine, as today. The plugin
  adds nothing.
- `claude-md-or-agents-md` (the default): a project with no instruction files
  of its own gets its `AGENTS.md` files instead, loaded exactly where and how
  `CLAUDE.md` would be. "Of its own" is read off what the engine loaded for
  the context: a `CLAUDE.md`, `.claude/CLAUDE.md` or `CLAUDE.local.md` in any
  directory from the root down to the working directory leaves the whole
  project to the engine, and the plugin stays out (the organization's managed
  file, the person's `~/.claude/CLAUDE.md`, a `.claude/rules` file and an
  added directory's `CLAUDE.md` do not count, as the nested walk does not see
  them either). With none, every `AGENTS.md` and `.claude/AGENTS.md` on that
  path joins the instruction files the engine renders, and a `Read` under a
  subdirectory attaches that directory's `AGENTS.md` unless a `CLAUDE.md`
  there claims it.
- `claude-md-and-agents-md`: every `AGENTS.md` is loaded beside `CLAUDE.md`,
  up and down the tree; a file `CLAUDE.md` already `@`-imports, or is a link
  to, is not loaded a second time (compared by path, then by content).
- `managed-only`: the project's checked-in and private instruction files and
  the person's own are dropped from the context; the organization's managed
  `CLAUDE.md` and the engine's memory stay. The engine's nested `CLAUDE.md`
  attachments on `Read` are not an event yet and still arrive. (The engine's
  `claudeMdExcludes` setting also exists, for user, project and local files,
  and applies to the `AGENTS.md` files this plugin reads too.)

How the files reach the model is the engine's doing, not the plugin's:
`prompt.context` hands a hook the instruction files behind `claudeMd`
(`{ path, kind, content, parent? }`, kinds `managed`, `user`, `project`,
`local`, `memory`, in load order) and a hook answers the list changed. The
engine then renders `claudeMd` from the answered files with its own preamble
and framing, announces them by name, and keeps only the `managed` ones for an
agent that omits project instructions (Explore, Plan, a custom agent with
`omitClaudeMd`). So an `AGENTS.md` this plugin adds as a `project` file is, to
everything downstream, a project instruction file: same place in the context,
same framing, same omission rules, same announcement. An organization's
prepended plugin on `prompt.context` sits above this one and has the last
word on the files.

`hooks/register.ts` is the module; everything under `hooks/` is its parts,
importing `claude-code` and one another alone. `tests/` runs under
`claude plugin test <this folder>`.

## Setting the option

As a built-in its option is the `/config` row "Project instructions", a
picker over the four values, each described there. By hand it is

```json
{
  "pluginConfigs": {
    "agents-md@builtin": {
      "options": { "instructionFiles": "claude-md-and-agents-md" }
    }
  }
}
```

in user settings (`~/.claude/settings.json`), `--settings`, or managed
settings; a project's `.claude/settings.json` is not read for plugin
options. Changing it reloads the module, and the next context the engine
builds (the next turn after the reload, a new conversation, `/clear`, a
compaction) carries the new mode's files. A hand-typed value outside the
four is told once in the transcript and reads as the default. `/plugin`
lists the plugin among the built-ins, where a person can turn it off; with
it off the engine reads `CLAUDE.md` alone. No hooks setting or CLI mode turns
it off (`disableAllHooks`, `allowManagedHooksOnly` and `--bare` govern
settings hooks and installed plugins, not built-ins); where the engine loads
no instruction files (`--bare` without `--add-dir`, `--safe-mode`,
`CLAUDE_CODE_DISABLE_CLAUDE_MDS`) its walk finds none and it adds none,
`CLAUDE.md` and `AGENTS.md` alike.

The option was first keyed `projectInstructions`, with the values `claude`,
`agents-fallback`, `both` and `none`. A value still stored under that key is
honoured for now while `instructionFiles` reads as its default: `none` as
`managed-only`, `claude` as `claude-md`, `agents-fallback` as
`claude-md-or-agents-md`, `both` as `claude-md-and-agents-md`, any other
value as `claude-md` (which adds nothing, never as the default, which loads
`AGENTS.md`); the first `session.start` of a load says in the transcript how
it was read. Once `instructionFiles` is set to anything but its default, the
old key is not read and the transcript says to remove it.

Run from this folder instead (`claude --plugin-dir mods/agents-md`), the
same entry is keyed `"agents-md"`.

## What it hooks

| event | what the hook does |
| --- | --- |
| `session.start` | in every mode: passes the start straight through and floats the usage row for the configured mode, never awaited; the first start of a load logs how a stored `projectInstructions` value is read. The session's start never waits on this plugin |
| `prompt.context` | under `claude-md-or-agents-md` and `claude-md-and-agents-md`: walks `$.fs.ancestors` for the `AGENTS.md` files above the working directory and answers them as `project` instruction files, each `@` import its own entry after its file, each placed where a project file of its directory stands (root first, before the first deeper project file, else after the last project file, before memory); files the engine already holds by path or by content are left out; under `claude-md-or-agents-md` it answers nothing when the project has a `CLAUDE.md` of its own (among the handed files, else found by a `$.fs.ancestors` walk, so a `CLAUDE.md` the engine loaded and then withheld still counts), and names the files it loaded in the debug log (`$.ui.log` with `to: "debug"`: `no CLAUDE.md found; AGENTS.md loaded: <paths>`, nothing in the transcript) once, and again after a move to another project root; handed unknown files (a hook above rewrote the `claudeMd` text) it adds nothing; the first context of a load sends the load row (counts) and the feature mark; under `managed-only` (matcher: a `project`, `local` or `user` file present): answers the list without those kinds |
| `agent.spawn` on `fork: true` | under `claude-md-or-agents-md` and `claude-md-and-agents-md`: a fork the Agent tool starts shares its parent's prompt prefix, so the parent loop's delivered nested files are copied to the fork's loop and not attached to it again (a run that resumes a fork is passed on untouched, the fork keeping the set its own loop was given; a `/fork` or `/subtask` fork does not raise `agent.spawn` yet and starts from an empty set, as every fork did before; a fork started in the same tool batch as a `Read` inherits that Read's file although its prefix holds a placeholder for it) |
| `tool.call` on `Read` | under `claude-md-or-agents-md` and `claude-md-and-agents-md`, for a file under the session's project root (`$.session.root()`, read live, so `/cd`, a host's directory change and worktree moves are followed and a moved root starts the delivered sets and the fallback decision over; a file elsewhere gets nothing, as the engine attaches no nested `CLAUDE.md` there; and nothing anywhere in a run where the engine attaches nothing to a turn, `--bare` with its `CLAUDE_CODE_SIMPLE` or `CLAUDE_CODE_DISABLE_ATTACHMENTS`, read on every Read through `$.env.get` as the engine reads them on every turn): walks only the directories strictly between the root and the read file (`$.fs.ancestors` with `below: root`, as the engine walks only those for a nested `CLAUDE.md`, never up to the filesystem root again) and attaches their `AGENTS.md` files not yet given to that agent loop, not already among the context's instruction files (by path or, for a project file, by text) and not claimed by a `CLAUDE.md` of the same directory (or imported by one), as `context` after the tool result, framed `Contents of <path>:` byte for byte as the engine frames a nested `CLAUDE.md`, whatever its size; each file once per loop and conversation (the context's recomputation after a compaction or `/clear` starts the count over), the context's files never; a Read that attached files sends the nested row. A `~` or `~/` path is read under the home directory as the Read tool reads it |

## What it calls on `$`

`fs.ancestors` (with each found file's `parts`: the file and its imports
apart; with `below` on a Read; it finds nothing on a thin client, whose
workspace files are remote, as the engine's own walk does), `session.root`,
`session.cwd`, `env.get` (`HOME` and `USERPROFILE`, once per load, the
profile first on a Windows spelling of the working directory, so a `~/` path
the model hands a Read resolves where the Read tool reads it; `CLAUDE_CODE_SIMPLE`
and `CLAUDE_CODE_DISABLE_ATTACHMENTS` on every Read), `ui.log`,
`telemetry.log` and `telemetry.mark`.

`$.telemetry` is the [telemetry](../telemetry) plugin's noun; where that
plugin is not seated the calls find no noun and are dropped without a trace,
and nothing else changes.

## What it logs

Counts and closed choices only; no path and no file text. Each row goes
through `$.telemetry.log`, so it exists only where the telemetry plugin
does:

| event | when | properties |
| --- | --- | --- |
| `agents_md_mode` | once per fresh load, at `session.start` | `mode` (`claude-md` \| `claude-md-or-agents-md` \| `claude-md-and-agents-md` \| `managed-only`), `is_interactive` |
| `agents_md_load` | the first context of a load, under `claude-md-or-agents-md` and `claude-md-and-agents-md` | `mode`, `file_count` (`AGENTS.md` files handed to the engine), `import_count` (their `@` imports), `total_content_length`, `yielded` (`claude-md-or-agents-md` stood down for a `CLAUDE.md` of the project's own), `walk_failed`; with it one `$.telemetry.mark` for feature `agents_md`: `ok`, or `sad` with reason `walk_failed` |
| `agents_md_nested` | a Read that attached nested files | `mode`, `file_count` |

## Where it still differs from CLAUDE.md

All of these apply only to the modes that load `AGENTS.md`,
`claude-md-or-agents-md` (the default) and `claude-md-and-agents-md`. Each
names a loader fact a plugin cannot reach through the events it has today.

1. Nested files attach on a text `Read` only. The engine also attaches a
   directory's `CLAUDE.md` for a file `@`-mentioned in the prompt, for the
   IDE's opened file or selection, and for the `Read` tool's notebook, image
   and PDF results.
2. A nested file the plugin attaches is not registered in the loop's
   read-file state, so after a compaction the engine does not restore it
   among the recently read files (the plugin attaches it again at the next
   `Read` under that directory instead), and a change to it mid-session is
   not re-announced.
3. `/cd` carries the new tree's `CLAUDE.md` in its own notice; the plugin's
   files for the new tree arrive in the same next request through the
   engine's instructions announcement instead.
4. Paths compare by spelling; the engine resolves a symlinked alias of the
   working directory before deciding a file is inside it.
5. `--add-dir` directories contribute no `AGENTS.md`, where the engine can
   load their `CLAUDE.md`.
6. `/memory` and the `#` shortcut do not know `AGENTS.md` files, and the
   engine's own initial-load row does not count them (this plugin's
   `agents_md_load` row does).
7. An `@` import outside the working directory inside an `AGENTS.md` is
   honoured only once the approval the engine asks for a `CLAUDE.md`'s
   external imports has been given (without it the import is left out, as a
   `CLAUDE.md`'s is); the approval dialog itself is raised for `CLAUDE.md`
   imports alone.
8. A subagent that is not a fork gets a nested `AGENTS.md` at its own first
   `Read` under that directory even when its parent's loop was already given
   it; the engine does not hand such a subagent the nested `CLAUDE.md` again.
   A fork matches the engine on both sides.

## Testing

    claude plugin test mods/agents-md

`tests/register.test.ts` covers the default mode: a project with `AGENTS.md`
alone gets it as a project instruction file and one debug-log line naming
it, with nothing in the transcript, a project with a `CLAUDE.md` of its own is
left to the engine without a walk, a failed walk leaves the context as handed,
and the start hands `$.telemetry` the mode row alone where a test seats a
provider for that noun, and goes on untouched where none is seated.