diff --git a/tests/e2e/cross-version-wire/structured-agent-session-host-fixture.ts b/tests/e2e/cross-version-wire/structured-agent-session-host-fixture.ts
index 6cf13ecff24..465899751a2 100644
--- a/tests/e2e/cross-version-wire/structured-agent-session-host-fixture.ts
+++ b/tests/e2e/cross-version-wire/structured-agent-session-host-fixture.ts
@@ -78,6 +78,9 @@ export function structuredHostStub(
       subscriber.emit({ type: 'snapshot', sessions: [] })
       return () => undefined
     }),
+    // No opening emit, unlike the status feed above: a completion is an edge, so this stream
+    // opens empty and a subscriber that was away has missed what passed.
+    subscribeTurnCompletions: vi.fn(() => () => undefined),
     unsubscribe: vi.fn()
   }
 }
diff --git a/tests/e2e/cross-version-wire/structured-agent-session-surface-manifest.ts b/tests/e2e/cross-version-wire/structured-agent-session-surface-manifest.ts
index 0bb0b43f20f..97588ae0cfb 100644
--- a/tests/e2e/cross-version-wire/structured-agent-session-surface-manifest.ts
+++ b/tests/e2e/cross-version-wire/structured-agent-session-surface-manifest.ts
@@ -18,6 +18,7 @@ export const THREAD = '019fd532-7c11-7a90-b6de-4e1a2c3d5f60'
 export const NOW = 1_800_000_000_000
 export const REWIND_METHOD = 'agentSession.rewind'
 export const STATUS_FEED_METHOD = 'agentSession.subscribeStatus'
+export const TURN_COMPLETION_FEED_METHOD = 'agentSession.subscribeTurnCompletions'
 
 let operations = 0
 
@@ -147,6 +148,13 @@ export const STRUCTURED_CALLS: {
     hostMethod: 'subscribeStatus',
     result: { type: 'snapshot', sessions: [] }
   },
+  // Opens with nothing for the same reason `agentSession.subscribe` does, and unlike the status
+  // feed above: a completion is an edge that has already passed, not state a late subscriber
+  // needs. Reaching the host is the only signal that the gate opened.
+  {
+    method: TURN_COMPLETION_FEED_METHOD,
+    hostMethod: 'subscribeTurnCompletions'
+  },
   // Teardown runs through the runtime's subscription registry rather than the
   // host, so its reply is the only signal that the gate opened.
   { method: 'agentSession.unsubscribe', hostMethod: null, result: { unsubscribed: true } }