diff --git a/packages/agent/src/harness/session/memory.ts b/packages/agent/src/harness/session/memory.ts
index 9bb7c9f72..356856ebe 100644
--- a/packages/agent/src/harness/session/memory.ts
+++ b/packages/agent/src/harness/session/memory.ts
@@ -1,7 +1,7 @@
 import { type Usage, uuidv7 } from "@earendil-works/pi-ai";
 import type { AgentMessage } from "../../types.ts";
 import { StorageBackedSession } from "./session.ts";
-import { StorageState, type StorageStateSnapshot } from "./storage-state.ts";
+import { registerKey, StorageState, type StorageStateSnapshot } from "./storage-state.ts";
 import type {
 	BranchScan,
 	CommitResult,
@@ -37,10 +37,6 @@ export interface MemorySessionRepoOptions {
 	now?: () => number;
 }
 
-function registerKey(namespace: RegisterNamespace, key: string): string {
-	return `${namespace}\u0000${key}`;
-}
-
 function isRegisterNamespace<TNamespace extends RegisterNamespace>(
 	register: Register,
 	namespace: TNamespace,
diff --git a/packages/agent/src/harness/session/storage-state.ts b/packages/agent/src/harness/session/storage-state.ts
index 33b4e7f90..d8cd1a299 100644
--- a/packages/agent/src/harness/session/storage-state.ts
+++ b/packages/agent/src/harness/session/storage-state.ts
@@ -32,7 +32,7 @@ export interface StorageStateSnapshot {
 	nextSeq: number;
 }
 
-function registerKey(namespace: RegisterNamespace, key: string): string {
+export function registerKey(namespace: RegisterNamespace, key: string): string {
 	return `${namespace}\u0000${key}`;
 }