diff --git a/packages/core/src/npm.ts b/packages/core/src/npm.ts
index 30e12cff1206..9beb577d76ab 100644
--- a/packages/core/src/npm.ts
+++ b/packages/core/src/npm.ts
@@ -47,6 +47,18 @@ export function sanitize(pkg: string) {
   return Array.from(pkg, (char) => (illegal.has(char) || char.charCodeAt(0) < 32 ? "_" : char)).join("")
 }
 
+// Canonical cache root for a specifier (#48514): bare names share the
+// @latest root so plugin, provider and V1 config-ref loaders all resolve
+// the same install instead of keying the cache by raw specifier string.
+export function cacheKey(pkg: string) {
+  try {
+    const parsed = npa(pkg)
+    return parsed.name && parsed.raw === parsed.name ? `${parsed.name}@latest` : pkg
+  } catch {
+    return pkg
+  }
+}
+
 const resolveEntryPoint = (name: string, dir: string): EntryPoint => {
   let entrypoint: string | undefined
   try {
@@ -113,7 +125,7 @@ const layer = Layer.effect(
       )
 
     const add = Effect.fn("Npm.add")(function* (pkg: string) {
-      const dir = directory(pkg)
+      const dir = directory(cacheKey(pkg))
       const name = (() => {
         try {
           return npa(pkg).name ?? pkg
@@ -190,7 +202,7 @@ const layer = Layer.effect(
     }, Effect.scoped)
 
     const which = Effect.fn("Npm.which")(function* (pkg: string, bin?: string) {
-      const dir = directory(pkg)
+      const dir = directory(cacheKey(pkg))
       const binDir = path.join(dir, "node_modules", ".bin")
 
       const pick = Effect.fnUntraced(function* () {
diff --git a/packages/core/test/npm.test.ts b/packages/core/test/npm.test.ts
index 7e4a5763bf08..30c27cf7d7b6 100644
--- a/packages/core/test/npm.test.ts
+++ b/packages/core/test/npm.test.ts
@@ -35,6 +35,22 @@ describe("Npm.sanitize", () => {
   })
 })
 
+describe("Npm.cacheKey", () => {
+  test("bare names share the @latest cache root", () => {
+    expect(Npm.cacheKey("prettier")).toBe("prettier@latest")
+    expect(Npm.cacheKey("prettier@latest")).toBe("prettier@latest")
+    expect(Npm.cacheKey("@scope/pkg")).toBe("@scope/pkg@latest")
+    expect(Npm.cacheKey("@scope/pkg@latest")).toBe("@scope/pkg@latest")
+  })
+
+  test("versioned and non-registry specs keep their own root", () => {
+    expect(Npm.cacheKey("prettier@1.2.3")).toBe("prettier@1.2.3")
+    expect(Npm.cacheKey("prettier@^2")).toBe("prettier@^2")
+    const spec = "acme@git+https://github.com/opencode/acme.git"
+    expect(Npm.cacheKey(spec)).toBe(spec)
+  })
+})
+
 describe("Npm.add", () => {
   test("reifies when package cache directory exists without the package installed", async () => {
     await using tmp = await tmpdir()