diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..17114e9
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,42 @@
+# AGENTS.md
+
+F# source loader for the Hosihikari Framework. It compiles `.fsx` files with FSharp.Compiler.Service
+at load and runs the result in a collectible assembly load context.
+
+## Repository map
+
+- `src/` — loader implementation and cache.
+- `host/` — assertion host for compilation, caching, isolation, and unload.
+- `test/` — fixture packages and private dependencies.
+- `pack.ps1` — build the `hosihikari-fsharp` lip package.
+- `tooth.json` — lip package metadata.
+
+## Build and verify
+
+```bash
+dotnet run --project host/Hosihikari.PluginLoader.FSharp.Host.csproj -c Release --nologo
+pwsh ./pack.ps1 -Version 1.0.0 -OutputRoot artifacts
+```
+
+The host expects sibling `PluginManager`, `Plugin.Abstractions`, and `McMaster.NETCore.Plugins`
+checkouts. `pack.ps1` calls the core packer and needs the same `PluginManager` checkout.
+
+## Invariants
+
+- The loader package is named `hosihikari-fsharp`; it routes on `extraInfo.loader: assembly` with
+  entry `Hosihikari.PluginLoader.FSharp.dll`. Source packages conventionally use
+  `extraInfo.loader: fsharp` and entry `main.fsx`; the loader follows the manifest's `EntryPath`,
+  so nested or renamed script paths remain valid.
+- Compile-time references follow the runtime order: framework shared layer, package-local DLLs,
+  the loader directory (for dependencies such as `FSharp.Core`), then trusted platform assemblies.
+- Cache keys cover source text, `#load` and local `#r` inputs, package-local DLLs, compiler version,
+  and runtime version. Keep the checksum check in sync.
+- A failed load releases its ALC. After excluding abstract/interface types and implementations
+  without a public parameterless constructor, a package exposes exactly one `IPlugin` candidate.
+- Public default branches are protected. Work on a branch, open a pull request, and squash merge.
+
+## Context
+
+- [Design record](https://github.com/HosihikariFramework/Design) — GLOSSARY and ADRs.
+- [F# loader](https://github.com/HosihikariFramework/FSharpLoader) and the
+  [F# plugin template](https://github.com/HosihikariFramework/FSharpPluginTemplate).