diff --git a/studio/frontend/src/features/chat/artifacts/artifact-card.tsx b/studio/frontend/src/features/chat/artifacts/artifact-card.tsx
index ee8c26abf1..0345dc6e2a 100644
--- a/studio/frontend/src/features/chat/artifacts/artifact-card.tsx
+++ b/studio/frontend/src/features/chat/artifacts/artifact-card.tsx
@@ -8,7 +8,7 @@ import { cn } from "@/lib/utils";
 import { useAuiState } from "@assistant-ui/react";
 import { LayoutTwoColumnIcon as Layout2ColumnIcon } from "@hugeicons/core-free-icons";
 import { HugeiconsIcon } from "@hugeicons/react";
-import { useLayoutEffect, useMemo } from "react";
+import { useLayoutEffect, useMemo, useRef } from "react";
 import { useChatRuntimeStore } from "../stores/chat-runtime-store";
 import type { ArtifactViewMode } from "./html-frame";
 import {
@@ -83,15 +83,18 @@ export function ArtifactCard({
     ],
   );
   const surface = artifactThreadId ? "panel" : "overlay";
+  // Once per mount, so a view-change cleanup can't re-trigger a stale open.
+  const autoOpenAttemptedRef = useRef(false);
 
   useLayoutEffect(() => {
     if (selectedArtifactId === artifact.id) {
       updateArtifact(artifact);
     }
 
-    if (!autoOpen) {
+    if (!autoOpen || autoOpenAttemptedRef.current) {
       return;
     }
+    autoOpenAttemptedRef.current = true;
     if (hasAutoOpenedArtifact(artifact.id)) {
       return;
     }
diff --git a/studio/frontend/src/features/chat/chat-page.tsx b/studio/frontend/src/features/chat/chat-page.tsx
index 380ce0e0ab..ec0ad977bf 100644
--- a/studio/frontend/src/features/chat/chat-page.tsx
+++ b/studio/frontend/src/features/chat/chat-page.tsx
@@ -247,13 +247,13 @@ const SingleContent = memo(function SingleContent({
     useState(false);
   const [isArtifactSurfaceVisible, setIsArtifactSurfaceVisible] =
     useState(false);
+  // Without a URL threadId the artifact must belong to the active thread.
   const showArtifactPanel = Boolean(
     artifact &&
       artifactSurface === "panel" &&
       (threadId
         ? !artifact.threadId || artifact.threadId === threadId
-        : Boolean(newThreadNonce) ||
-          Boolean(artifact.threadId && artifact.threadId === activeThreadId)),
+        : Boolean(artifact.threadId && artifact.threadId === activeThreadId)),
   );
 
   const artifactLayoutActive = showArtifactPanel || isArtifactPanelLayoutActive;
@@ -1771,10 +1771,8 @@ export function ChatPage({
 
   useEffect(() => {
     if (view.mode !== "single") return;
-    if (view.threadId || view.newThreadNonce || !selectedArtifact) return;
-    // view excludes __LOCALID_ threads (they fall through to mode:"single"
-    // with no threadId/nonce). Don't close a canvas whose thread is the
-    // active local thread.
+    if (view.threadId || !selectedArtifact) return;
+    // Close any canvas that doesn't belong to the active thread.
     if (
       selectedArtifact.threadId &&
       selectedArtifact.threadId === activeThreadId