diff --git a/frontend-web/src/position-roundtable/components/PositionNodeChat.tsx b/frontend-web/src/position-roundtable/components/PositionNodeChat.tsx
index 600d4c2b..f566fbb1 100644
--- a/frontend-web/src/position-roundtable/components/PositionNodeChat.tsx
+++ b/frontend-web/src/position-roundtable/components/PositionNodeChat.tsx
@@ -757,20 +757,28 @@ export function PositionNodeChat({
     }
     // One write_file call should open at most one preview. The parent further
     // guards manual close state, because it owns the page-wide singleton sandbox.
-    // A report is often rewritten to the same output path.  The tool-call key
-    // (not just the path) makes that a new previewable delivery.
+    // A report is often rewritten to the same output path — identity must be the
+    // tool-call key, not the path, otherwise a second write keeps the old panel
+    // and the sandbox never clears / remounts for the rewrite.
+    const toolCallKey = newStreamingArtifact.key;
+    const toolCallId = toolCallKey.includes(":")
+      ? toolCallKey.slice(toolCallKey.lastIndexOf(":") + 1)
+      : undefined;
     const startedPreview = activeWriteFilePreviewRef.current;
-    const previewKey =
-      startedPreview?.path === newStreamingArtifact.sourcePath
-        ? startedPreview.previewKey
-        : newStreamingArtifact.key;
-    if (!startedPreview || startedPreview.path !== newStreamingArtifact.sourcePath) {
-      activeWriteFilePreviewRef.current = {
-        path: newStreamingArtifact.sourcePath,
-        previewKey,
-        toolCallId: startedPreview?.toolCallId,
-      };
-    }
+    const isSameToolCall =
+      startedPreview != null &&
+      (startedPreview.previewKey === toolCallKey ||
+        (toolCallId != null &&
+          (startedPreview.toolCallId === toolCallId ||
+            startedPreview.previewKey.endsWith(`:${toolCallId}`))));
+    // Same tool call may upgrade a provisional filename → real path; keep the
+    // open panel. A different tool call is a new delivery even on the same path.
+    const previewKey = isSameToolCall ? startedPreview.previewKey : toolCallKey;
+    activeWriteFilePreviewRef.current = {
+      path: newStreamingArtifact.sourcePath,
+      previewKey,
+      toolCallId: toolCallId ?? startedPreview?.toolCallId,
+    };
     // The path takes part in the identity so that a preview opened under a
     // provisional name is re-published once the real path streams in. The
     // preview key stays the same, so the parent treats it as an update of the