diff --git a/packages/ui/src/sync/DOCUMENTATION.md b/packages/ui/src/sync/DOCUMENTATION.md
index 92399850..c8056edc 100644
--- a/packages/ui/src/sync/DOCUMENTATION.md
+++ b/packages/ui/src/sync/DOCUMENTATION.md
@@ -217,15 +217,15 @@ Examples of global-store updates performed in `session-actions.ts`:
 - `deleteSession()` -> waits for server confirmation or `404`, then removes the session and its persisted state
 - `moveSessionToDirectory()` -> move the session between directory stores and update the global directory index
 
-Archive callers whose confirmation spans asynchronous SDK calls may capture the
-runtime key at operation start and pass it as `expectedRuntimeKey`. The guarded
-action rechecks that key before every store reconciliation, so a response
+Archive actions capture the active runtime key when they start and recheck it
+before every store reconciliation, so a response
 produced by the previous runtime is rejected instead of mutating the current
 runtime's live or global session state. A guarded batch stops at the first
 observed runtime change: sessions the server already confirmed remain archived
 and stay in `archivedIds`, while every ID not confirmed on the captured runtime
 is returned in `failedIds` so existing partial-failure feedback stays truthful.
-Callers that pass no runtime key keep the previous unguarded behavior.
+Callers whose confirmation can span a runtime switch may pass an
+`expectedRuntimeKey` captured earlier; ordinary callers are guarded by default.
 
 ## The golden rule
 
diff --git a/packages/ui/src/sync/session-actions.test.ts b/packages/ui/src/sync/session-actions.test.ts
index 0e2bda49..b23f6e19 100644
--- a/packages/ui/src/sync/session-actions.test.ts
+++ b/packages/ui/src/sync/session-actions.test.ts
@@ -448,7 +448,7 @@ describe("confirmed session removal", () => {
     const { archiveSession, setActionRefs } = await import("./session-actions")
     setActionRefs(mockSdk as unknown as OpencodeClient, createChildStores([["/test/project", source]]), () => "/test/project")
 
-    expect(await archiveSession("session-a", "archive-runtime-a")).toBe(false)
+    expect(await archiveSession("session-a")).toBe(false)
     expect(getRuntimeKey()).toBe("archive-runtime-b")
     // The stale response must not reconcile the runtime the user switched to.
     expect(source.getState().session.map((item) => item.id)).toEqual(["session-a"])
@@ -476,9 +476,7 @@ describe("confirmed session removal", () => {
     const { archiveSessions, setActionRefs } = await import("./session-actions")
     setActionRefs(mockSdk as unknown as OpencodeClient, createChildStores([["/test/project", source]]), () => "/test/project")
 
-    const result = await archiveSessions(["session-a", "session-b", "session-c"], {
-      expectedRuntimeKey: "archive-batch-a",
-    })
+    const result = await archiveSessions(["session-a", "session-b", "session-c"])
 
     // session-a was confirmed before the switch and stays archived; session-b's
     // response is stale and session-c is never attempted, so both are reported
diff --git a/packages/ui/src/sync/session-actions.ts b/packages/ui/src/sync/session-actions.ts
index 43e08171..c554b9c6 100644
--- a/packages/ui/src/sync/session-actions.ts
+++ b/packages/ui/src/sync/session-actions.ts
@@ -827,15 +827,16 @@ export async function deleteSessionInDirectory(sessionId: string, directory: str
 /**
  * Archive one session.
  *
- * `expectedRuntimeKey` is the runtime key the caller captured when the user
- * confirmed the operation. When it is supplied and the runtime changes, the
- * action stops and returns `false` without reconciling any store, so a response
+ * `expectedRuntimeKey` defaults to the active runtime when the action starts.
+ * Callers may supply a key captured earlier when confirmation spans a runtime
+ * switch. When the runtime changes, the action stops and returns `false`
+ * without reconciling any store, so a response
  * produced by the previous runtime cannot mutate the current runtime's live or
  * global session state. A session the server already archived before the switch
  * stays archived on that runtime and is re-read from the server the next time
  * the runtime is loaded.
  */
-export async function archiveSession(sessionId: string, expectedRuntimeKey?: string): Promise<boolean> {
+export async function archiveSession(sessionId: string, expectedRuntimeKey = getRuntimeKey()): Promise<boolean> {
   if (isStaleRuntime(expectedRuntimeKey)) return false
   const sessionDirectory = getSessionDirectory(sessionId)
   const archivedAt = Date.now()
@@ -884,7 +885,7 @@ export async function archiveSessions(
 ): Promise<{ archivedIds: string[]; failedIds: string[] }> {
   const archivedIds: string[] = []
   const failedIds: string[] = []
-  const expectedRuntimeKey = options?.expectedRuntimeKey
+  const expectedRuntimeKey = options?.expectedRuntimeKey ?? getRuntimeKey()
 
   for (const [index, id] of ids.entries()) {
     if (isStaleRuntime(expectedRuntimeKey)) {