diff --git a/apps/web/src/components/files/FilePreviewPanel.test.ts b/apps/web/src/components/files/FilePreviewPanel.test.ts
index d9361ba21244a..d689a393d8db2 100644
--- a/apps/web/src/components/files/FilePreviewPanel.test.ts
+++ b/apps/web/src/components/files/FilePreviewPanel.test.ts
@@ -296,7 +296,7 @@ Third}`;
         },
       ],
     });
-    // IPython traceback frames can omit trailing newlines or place ANSI resets after them.
+    // IPython traceback frames carry ANSI SGR colors and can omit trailing newlines.
     const failed = openNotebook(
       bytes(
         JSON.stringify({
@@ -304,7 +304,7 @@ Third}`;
           cells: [
             {
               cell_type: "code",
-              source: "fail()",
+              source: 'print("\u001b[32m")\nfail()',
               outputs: [
                 {
                   output_type: "error",
@@ -330,7 +330,7 @@ Third}`;
                     "\u001b[31mTraceback (most recent call last):\n\u001b[0m",
                     "\u001b[32mCell In[3], line 1\n----> 1 fail()\n\u001b[0m\u001b[39m",
                     "\u001b[31mValueError: preview proof\u001b[0m",
-                    "final entry",
+                    "final entry \\x1b[31m kept",
                   ],
                 },
               ],
@@ -340,6 +340,7 @@ Third}`;
       ),
     );
     if (failed.type !== "notebook") throw new Error("Expected notebook");
+    expect(failed.cells[0]!.source).toBe('print("\u001b[32m")\nfail()');
     expect(failed.cells[0]!.outputs).toEqual([
       {
         kind: "text",
@@ -351,7 +352,7 @@ Third}`;
       },
       {
         kind: "text",
-        text: "\u001b[31mTraceback (most recent call last):\n\u001b[0m\u001b[32mCell In[3], line 1\n----> 1 fail()\n\u001b[0m\u001b[39m\u001b[31mValueError: preview proof\u001b[0m\nfinal entry",
+        text: "Traceback (most recent call last):\nCell In[3], line 1\n----> 1 fail()\nValueError: preview proof\nfinal entry \\x1b[31m kept",
       },
     ]);
     expect(() => openNotebook(bytes('{"nbformat":3,"cells":[]}'))).toThrow("version 4");
diff --git a/apps/web/src/components/files/extendedDocumentPreview.ts b/apps/web/src/components/files/extendedDocumentPreview.ts
index 6b840a00543a6..384e3a3e78dac 100644
--- a/apps/web/src/components/files/extendedDocumentPreview.ts
+++ b/apps/web/src/components/files/extendedDocumentPreview.ts
@@ -431,12 +431,14 @@ function notebookText(value: unknown, limit = 256_000): string {
   if (result.length > limit) throw new Error("A notebook cell is too large to preview.");
   return result;
 }
-// IPython traceback frames may omit a final newline or follow it with ANSI SGR sequences.
+// IPython traceback frames carry ANSI SGR colors a <pre> cannot render and may omit a final newline.
 function tracebackLines(value: unknown): unknown {
   if (!Array.isArray(value)) return value;
-  const frames = value.filter((frame): frame is string => typeof frame === "string");
+  const frames = value
+    .filter((frame): frame is string => typeof frame === "string")
+    .map((frame) => frame.replaceAll(/\u001b\[[\d;:]*m/g, ""));
   return frames.map((frame, index) =>
-    index && !/\n(?:\u001b\[[\d;:]*m)*$/.test(frames[index - 1]!) ? `\n${frame}` : frame,
+    index && !frames[index - 1]!.endsWith("\n") ? `\n${frame}` : frame,
   );
 }
 export function openNotebook(bytes: ArrayBuffer): OfficeWorkerResult {