diff --git a/CODEX.md b/CODEX.md
new file mode 100644
index 0000000..593747e
--- /dev/null
+++ b/CODEX.md
@@ -0,0 +1,22 @@
+# CODEX.md
+
+This repository uses the same working conventions described in [`CLAUDE.md`](CLAUDE.md).
+Keep the two files aligned.
+
+## AX Notes
+
+- Prefer descriptive names over abbreviations.
+- Public comments should show real usage with concrete values.
+- Keep examples in UK English.
+- Do not add compatibility aliases; the primary API names are the contract.
+- Preserve the single-connection SQLite design.
+- Verify with `go test ./...`, `go test -race ./...`, and `go vet ./...` before committing.
+- Use conventional commits and include the `Co-Authored-By: Virgil <virgil@lethean.io>` trailer.
+
+## Repository Shape
+
+- `store.go` contains the core store API and SQLite lifecycle.
+- `events.go` contains mutation events, watchers, and callbacks.
+- `scope.go` contains namespace isolation and quota enforcement.
+- `docs/` contains the package docs, architecture notes, and history.
+
diff --git a/README.md b/README.md
index 6e1d563..fe53bf1 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,7 @@ func main() {
 
 ## Documentation
 
+- [Agent Conventions](CODEX.md) - Codex-facing repo rules and AX notes
 - [Architecture](docs/architecture.md) — storage layer, group/key model, TTL expiry, event system, namespace isolation
 - [Development Guide](docs/development.md) — prerequisites, test patterns, benchmarks, adding methods
 - [Project History](docs/history.md) — completed phases, known limitations, future considerations
diff --git a/conventions_test.go b/conventions_test.go
index aad7708..48e56d2 100644
--- a/conventions_test.go
+++ b/conventions_test.go
@@ -174,7 +174,7 @@ func TestConventions_Exports_Good_NoCompatibilityAliases(t *testing.T) {
 func repoGoFiles(t *testing.T, keep func(name string) bool) []string {
 	t.Helper()
 
-	result := testFS().List(".")
+	result := testFilesystem().List(".")
 	requireCoreOK(t, result)
 
 	entries, ok := result.Value.([]fs.DirEntry)
diff --git a/coverage_test.go b/coverage_test.go
index 1f25cf6..032d772 100644
--- a/coverage_test.go
+++ b/coverage_test.go
@@ -118,8 +118,8 @@ func TestCoverage_GetAll_Bad_RowsError(t *testing.T) {
 	requireCoreWriteBytes(t, dbPath, data)
 
 	// Remove WAL/SHM so the reopened connection reads from the main file.
-	_ = testFS().Delete(dbPath + "-wal")
-	_ = testFS().Delete(dbPath + "-shm")
+	_ = testFilesystem().Delete(dbPath + "-wal")
+	_ = testFilesystem().Delete(dbPath + "-shm")
 
 	s2, err := New(dbPath)
 	require.NoError(t, err)
@@ -204,8 +204,8 @@ func TestCoverage_Render_Bad_RowsError(t *testing.T) {
 	copy(data[offset+len(garbage):offset+(len(garbage)*2)], garbage)
 	requireCoreWriteBytes(t, dbPath, data)
 
-	_ = testFS().Delete(dbPath + "-wal")
-	_ = testFS().Delete(dbPath + "-shm")
+	_ = testFilesystem().Delete(dbPath + "-wal")
+	_ = testFilesystem().Delete(dbPath + "-shm")
 
 	s2, err := New(dbPath)
 	require.NoError(t, err)
diff --git a/doc.go b/doc.go
index 81b70f3..648f304 100644
--- a/doc.go
+++ b/doc.go
@@ -1,8 +1,12 @@
 // Package store provides a SQLite-backed key-value store with group namespaces,
 // TTL expiry, quota-enforced scoped views, and reactive change notifications.
 //
-// storeInstance, _ := store.New(":memory:")
-// value, _ := storeInstance.Get("config", "theme")
+// Usage example:
+//
+//	storeInstance, _ := store.New(":memory:")
+//	scopedStore, _ := store.NewScoped(storeInstance, "tenant-a")
+//	_ = scopedStore.Set("config", "theme", "dark")
+//	value, _ := storeInstance.Get("config", "theme")
 //
 // Use New to open a store, then Set/Get for CRUD operations. Use
 // NewScoped/NewScopedWithQuota when group names need tenant isolation or
diff --git a/docs/index.md b/docs/index.md
index 238e08a..9cf9c0d 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -130,5 +130,6 @@ There are no other direct dependencies. The package uses the Go standard library
 
 ## Further Reading
 
+- [Agent Conventions](../CODEX.md) -- Codex-facing repo rules and AX notes
 - [Architecture](architecture.md) -- storage layer internals, TTL model, event system, concurrency design
 - [Development Guide](development.md) -- building, testing, benchmarks, contribution workflow
diff --git a/store_test.go b/store_test.go
index b680e21..2d2572e 100644
--- a/store_test.go
+++ b/store_test.go
@@ -55,7 +55,7 @@ func TestStore_New_Bad_InvalidPath(t *testing.T) {
 func TestStore_New_Bad_CorruptFile(t *testing.T) {
 	// A file that exists but is not a valid SQLite database should fail.
 	dbPath := testPath(t, "corrupt.db")
-	requireCoreOK(t, testFS().Write(dbPath, "not a sqlite database"))
+	requireCoreOK(t, testFilesystem().Write(dbPath, "not a sqlite database"))
 
 	_, err := New(dbPath)
 	require.Error(t, err)
@@ -73,8 +73,8 @@ func TestStore_New_Bad_ReadOnlyDir(t *testing.T) {
 	require.NoError(t, s.Close())
 
 	// Remove WAL/SHM files and make directory read-only.
-	_ = testFS().Delete(dbPath + "-wal")
-	_ = testFS().Delete(dbPath + "-shm")
+	_ = testFilesystem().Delete(dbPath + "-wal")
+	_ = testFilesystem().Delete(dbPath + "-shm")
 	require.NoError(t, syscall.Chmod(dir, 0555))
 	defer func() { _ = syscall.Chmod(dir, 0755) }() // restore for cleanup
 
diff --git a/test_helpers_test.go b/test_helpers_test.go
index 986057b..a7a5c12 100644
--- a/test_helpers_test.go
+++ b/test_helpers_test.go
@@ -7,7 +7,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func testFS() *core.Fs {
+func testFilesystem() *core.Fs {
 	return (&core.Fs{}).NewUnrestricted()
 }
 
@@ -23,14 +23,14 @@ func requireCoreOK(tb testing.TB, result core.Result) {
 
 func requireCoreReadBytes(tb testing.TB, path string) []byte {
 	tb.Helper()
-	result := testFS().Read(path)
+	result := testFilesystem().Read(path)
 	requireCoreOK(tb, result)
 	return []byte(result.Value.(string))
 }
 
 func requireCoreWriteBytes(tb testing.TB, path string, data []byte) {
 	tb.Helper()
-	requireCoreOK(tb, testFS().Write(path, string(data)))
+	requireCoreOK(tb, testFilesystem().Write(path, string(data)))
 }
 
 func repeatString(value string, count int) string {