[Fix] Live Fast turns get stamped as interrupted after 15 minutes

packages/cloud-agents/src/server/fast-agent/fast-agent-constants.ts

@@ -4,6 +4,11 @@ export const FAST_AGENT_MODEL_ROLE = 'orchestration' as const;
 // responses, short enough that a crashed turn self-heals the session status.
 // Streaming touch points re-extend it so long turns keep the lease fresh.
 export const FAST_RESPONDING_LEASE_MS = 15 * 60 * 1000;
+// Assistant-message persists also extend the lease, but a turn can spend
+// longer than the lease inside tool calls or a streaming stretch without
+// persisting one; the time-based renewal keeps the lease fresh for exactly
+// as long as the turn is actually executing.
+export const FAST_RESPONDING_LEASE_RENEW_MS = FAST_RESPONDING_LEASE_MS / 3;
 export const FAST_AGENT_GITHUB_MCP_PATH = '/api/mcp-routing/github';
 export const FAST_AGENT_TASKS_API_PATH = '/api/mcp/tasks';
 export const FAST_AGENT_ENVIRONMENTS_API_PATH = '/api/mcp/environments';

packages/cloud-agents/src/server/fast-agent/fast-agent-conversation-repository.ts

@@ -10,6 +10,8 @@ import {
   advanceSessionNotifiedCursor,
   advanceSessionReadCursor,
   getSessionForFastConversation,
+  gt,
+  isNotNull,
   isNull,
   lt,
   or,
@@ -207,6 +209,33 @@ export async function markFastAgentInferenceRetryNoticeInterruption(
   return stamped.length > 0;
 }
 
+/**
+ * Extend the responding lease with the fence in the statement itself: only a
+ * lease that is still live is extended, so a stale renewal from an owner that
+ * lost the conversation mid-write can never resurrect a lease a settlement
+ * or successor already cleared. No read precedes the write, which removes
+ * the check-then-write window entirely. Returns whether a lease was renewed.
+ */
+export async function renewFastSessionRespondingLease(
+  fastConversationId: string,
+): Promise<boolean> {
+  const renewed = await db
+    .update(sessions)
+    .set({
+      respondingUntil: new Date(Date.now() + FAST_RESPONDING_LEASE_MS),
+      updatedAt: new Date(),
+    })
+    .where(
+      and(
+        eq(sessions.fastConversationId, fastConversationId),
+        isNotNull(sessions.respondingUntil),
+        gt(sessions.respondingUntil, new Date()),
+      ),
+    )
+    .returning({ id: sessions.id });
+  return renewed.length > 0;
+}
+
 export async function reconcileExpiredFastAgentInferenceRetryNotices(
   limit = 100,
 ): Promise<number> {