fix(native): allow virgin empty chat replay

native/Sources/RTCStore/RTCStore.swift

@@ -213,6 +213,13 @@ public final class SQLiteConversationEventRepository: ConversationReplayReposito
     public func page(reviewID: ReviewID, conversationID: UUID, after: Int, maximumEvents: Int, maximumBytes: Int) async throws -> ConversationPage {
         guard after >= 0, maximumEvents > 0, maximumBytes > 0 else { throw RTCStoreError.corrupt("invalid conversation page") }
         return try await store.read { db in
+            // A newly opened conversation has no durable binding until its first write.
+            // Cursor zero is the only valid replay request for that virgin stream; keep
+            // all established-stream scope and cursor validation unchanged below.
+            guard try String.fetchOne(db, sql: "SELECT review_id FROM conversations WHERE id = ?", arguments: [conversationID.uuidString]) != nil else {
+                guard after == 0 else { throw RTCStoreError.corrupt("conversation scope") }
+                return ConversationPage(after: 0, nextCursor: 0, events: [], hasMore: false)
+            }
             try self.requireBinding(db, reviewID: reviewID, conversationID: conversationID)
             let last = (try Int.fetchOne(db, sql: "SELECT COALESCE(MAX(sequence), 0) FROM conversation_events WHERE conversation_id = ?", arguments: [conversationID.uuidString])) ?? 0
             guard after <= last else { throw RTCStoreError.corrupt("conversation cursor ahead") }

native/Tests/RTCAgentChatTests/AgentChatCoordinatorTests.swift

@@ -4,6 +4,15 @@ import RTCContracts
 import RTCAgentChat
 
 final class AgentChatCoordinatorTests: XCTestCase {
+    func testEmptyConversationReplayLeavesChatRailUsable() async throws {
+        let reviewID = try ReviewID("0123456789abcdef01234567")
+        let coordinator = AgentChatCoordinator(reviewID: reviewID, conversationID: UUID(), repository: MemoryRepository(), wakeSink: NoopWake())
+        let snapshot = try await coordinator.replay()
+        XCTAssertTrue(snapshot.events.isEmpty)
+        XCTAssertEqual(snapshot.cursor, 0)
+        XCTAssertFalse(snapshot.ended)
+    }
+
     func testReplayRejectsGapsAndWrongStream() async throws {
         let reviewID = try ReviewID("0123456789abcdef01234567")
         let conversationID = UUID(uuidString: "00000000-0000-0000-0000-000000000010")!

native/Tests/RTCStoreTests/StoreTests.swift

@@ -15,6 +15,26 @@ final class StoreTests: XCTestCase {
 }
 
 extension StoreTests {
+    func testVirginConversationAllowsOnlyEmptyCursorZeroPage() async throws {
+        let root = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("rtc-virgin-\(UUID().uuidString)")
+        defer { try? FileManager.default.removeItem(at: root) }
+        let store = try SQLiteStore(rootURL: root)
+        let repository = SQLiteConversationEventRepository(store: store)
+        let reviewID = try ReviewID("0123456789abcdef01234567")
+        let conversationID = UUID(uuidString: "00000000-0000-0000-0000-000000000010")!
+
+        let empty = try await repository.page(reviewID: reviewID, conversationID: conversationID, after: 0, maximumEvents: 100, maximumBytes: 1024)
+        XCTAssertTrue(empty.events.isEmpty)
+        XCTAssertEqual(empty.nextCursor, 0)
+        do { _ = try await repository.page(reviewID: reviewID, conversationID: conversationID, after: 1, maximumEvents: 100, maximumBytes: 1024); XCTFail("virgin nonzero cursor must fail") } catch { }
+
+        let otherReview = try ReviewID("fedcba9876543210fedcba98")
+        let decoder = JSONDecoder(); decoder.dateDecodingStrategy = .iso8601
+        let fixture = try decoder.decode([ConversationEvent].self, from: Data(contentsOf: URL(fileURLWithPath: "native/Fixtures/Chat/replay-lossless.json")))
+        try await repository.append(fixture[0])
+        do { _ = try await repository.page(reviewID: otherReview, conversationID: conversationID, after: 0, maximumEvents: 100, maximumBytes: 1024); XCTFail("mismatched binding must fail") } catch { }
+    }
+
     func testConversationReplayIsLosslessAcrossRepositoryInstances() async throws {
         let root = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("rtc-conversation-\(UUID().uuidString)")
         defer { try? FileManager.default.removeItem(at: root) }