diff --git a/src/plugin-sdk/acpx.ts b/src/plugin-sdk/acpx.ts
index 36da2f48810..9d634ec8fb5 100644
--- a/src/plugin-sdk/acpx.ts
+++ b/src/plugin-sdk/acpx.ts
@@ -1,5 +1,5 @@
-// Narrow plugin-sdk surface for the bundled acpx plugin.
-// Keep this list additive and scoped to symbols used under extensions/acpx.
+// Public ACPX runtime backend helpers.
+// Keep this surface narrow and limited to the ACP runtime/backend contract.
 
 export type { AcpRuntimeErrorCode } from "../acp/runtime/errors.js";
 export { AcpRuntimeError } from "../acp/runtime/errors.js";
diff --git a/src/plugin-sdk/subpaths.test.ts b/src/plugin-sdk/subpaths.test.ts
index d7b9399a0f2..f3cd5537398 100644
--- a/src/plugin-sdk/subpaths.test.ts
+++ b/src/plugin-sdk/subpaths.test.ts
@@ -315,7 +315,7 @@ describe("plugin-sdk subpath exports", () => {
     expect(typeof tlonSdk.tlonSetupAdapter).toBe("object");
   });
 
-  it("exports acpx helpers", async () => {
+  it("exports ACPX runtime backend helpers", async () => {
     expect(typeof acpxSdk.listKnownProviderAuthEnvVarNames).toBe("function");
     expect(typeof acpxSdk.omitEnvKeysCaseInsensitive).toBe("function");
   });